6256 lines
178 KiB
C
6256 lines
178 KiB
C
/*
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* INET An implementation of the TCP/IP protocol suite for the LINUX
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* operating system. INET is implemented using the BSD Socket
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* interface as the means of communication with the user level.
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*
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* Implementation of the Transmission Control Protocol(TCP).
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*
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* Authors: Ross Biro
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* Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
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* Mark Evans, <evansmp@uhura.aston.ac.uk>
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* Corey Minyard <wf-rch!minyard@relay.EU.net>
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* Florian La Roche, <flla@stud.uni-sb.de>
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* Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
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* Linus Torvalds, <torvalds@cs.helsinki.fi>
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* Alan Cox, <gw4pts@gw4pts.ampr.org>
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* Matthew Dillon, <dillon@apollo.west.oic.com>
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* Arnt Gulbrandsen, <agulbra@nvg.unit.no>
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* Jorge Cwik, <jorge@laser.satlink.net>
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*/
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/*
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* Changes:
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* Pedro Roque : Fast Retransmit/Recovery.
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* Two receive queues.
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* Retransmit queue handled by TCP.
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* Better retransmit timer handling.
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* New congestion avoidance.
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* Header prediction.
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* Variable renaming.
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*
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* Eric : Fast Retransmit.
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* Randy Scott : MSS option defines.
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* Eric Schenk : Fixes to slow start algorithm.
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* Eric Schenk : Yet another double ACK bug.
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* Eric Schenk : Delayed ACK bug fixes.
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* Eric Schenk : Floyd style fast retrans war avoidance.
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* David S. Miller : Don't allow zero congestion window.
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* Eric Schenk : Fix retransmitter so that it sends
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* next packet on ack of previous packet.
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* Andi Kleen : Moved open_request checking here
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* and process RSTs for open_requests.
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* Andi Kleen : Better prune_queue, and other fixes.
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* Andrey Savochkin: Fix RTT measurements in the presence of
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* timestamps.
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* Andrey Savochkin: Check sequence numbers correctly when
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* removing SACKs due to in sequence incoming
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* data segments.
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* Andi Kleen: Make sure we never ack data there is not
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* enough room for. Also make this condition
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* a fatal error if it might still happen.
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* Andi Kleen: Add tcp_measure_rcv_mss to make
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* connections with MSS<min(MTU,ann. MSS)
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* work without delayed acks.
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* Andi Kleen: Process packets with PSH set in the
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* fast path.
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* J Hadi Salim: ECN support
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* Andrei Gurtov,
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* Pasi Sarolahti,
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* Panu Kuhlberg: Experimental audit of TCP (re)transmission
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* engine. Lots of bugs are found.
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* Pasi Sarolahti: F-RTO for dealing with spurious RTOs
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*/
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#define pr_fmt(fmt) "TCP: " fmt
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#include <linux/mm.h>
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#include <linux/slab.h>
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#include <linux/module.h>
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#include <linux/sysctl.h>
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#include <linux/kernel.h>
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#include <linux/prefetch.h>
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#include <net/dst.h>
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#include <net/tcp.h>
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#include <net/inet_common.h>
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#include <linux/ipsec.h>
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#include <asm/unaligned.h>
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#include <linux/errqueue.h>
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int sysctl_tcp_timestamps __read_mostly = 1;
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int sysctl_tcp_window_scaling __read_mostly = 1;
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int sysctl_tcp_sack __read_mostly = 1;
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int sysctl_tcp_fack __read_mostly = 1;
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int sysctl_tcp_reordering __read_mostly = TCP_FASTRETRANS_THRESH;
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int sysctl_tcp_max_reordering __read_mostly = 300;
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EXPORT_SYMBOL(sysctl_tcp_reordering);
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int sysctl_tcp_dsack __read_mostly = 1;
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int sysctl_tcp_app_win __read_mostly = 31;
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int sysctl_tcp_adv_win_scale __read_mostly = 1;
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EXPORT_SYMBOL(sysctl_tcp_adv_win_scale);
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/* rfc5961 challenge ack rate limiting */
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int sysctl_tcp_challenge_ack_limit = 100;
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int sysctl_tcp_stdurg __read_mostly;
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int sysctl_tcp_rfc1337 __read_mostly;
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int sysctl_tcp_max_orphans __read_mostly = NR_FILE;
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int sysctl_tcp_frto __read_mostly = 2;
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int sysctl_tcp_thin_dupack __read_mostly;
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int sysctl_tcp_moderate_rcvbuf __read_mostly = 1;
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int sysctl_tcp_early_retrans __read_mostly = 3;
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int sysctl_tcp_invalid_ratelimit __read_mostly = HZ/2;
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#define FLAG_DATA 0x01 /* Incoming frame contained data. */
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#define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
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#define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
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#define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
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#define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
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#define FLAG_DATA_SACKED 0x20 /* New SACK. */
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#define FLAG_ECE 0x40 /* ECE in this ACK */
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#define FLAG_LOST_RETRANS 0x80 /* This ACK marks some retransmission lost */
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#define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
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#define FLAG_ORIG_SACK_ACKED 0x200 /* Never retransmitted data are (s)acked */
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#define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
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#define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */
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#define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */
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#define FLAG_UPDATE_TS_RECENT 0x4000 /* tcp_replace_ts_recent() */
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#define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
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#define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
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#define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
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#define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
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#define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
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#define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
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/* Adapt the MSS value used to make delayed ack decision to the
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* real world.
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*/
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static void tcp_measure_rcv_mss(struct sock *sk, const struct sk_buff *skb)
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{
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struct inet_connection_sock *icsk = inet_csk(sk);
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const unsigned int lss = icsk->icsk_ack.last_seg_size;
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unsigned int len;
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icsk->icsk_ack.last_seg_size = 0;
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/* skb->len may jitter because of SACKs, even if peer
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* sends good full-sized frames.
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*/
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len = skb_shinfo(skb)->gso_size ? : skb->len;
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if (len >= icsk->icsk_ack.rcv_mss) {
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icsk->icsk_ack.rcv_mss = len;
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} else {
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/* Otherwise, we make more careful check taking into account,
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* that SACKs block is variable.
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*
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* "len" is invariant segment length, including TCP header.
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*/
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len += skb->data - skb_transport_header(skb);
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if (len >= TCP_MSS_DEFAULT + sizeof(struct tcphdr) ||
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/* If PSH is not set, packet should be
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* full sized, provided peer TCP is not badly broken.
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* This observation (if it is correct 8)) allows
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* to handle super-low mtu links fairly.
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*/
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(len >= TCP_MIN_MSS + sizeof(struct tcphdr) &&
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!(tcp_flag_word(tcp_hdr(skb)) & TCP_REMNANT))) {
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/* Subtract also invariant (if peer is RFC compliant),
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* tcp header plus fixed timestamp option length.
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* Resulting "len" is MSS free of SACK jitter.
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*/
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len -= tcp_sk(sk)->tcp_header_len;
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icsk->icsk_ack.last_seg_size = len;
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if (len == lss) {
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icsk->icsk_ack.rcv_mss = len;
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return;
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}
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}
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if (icsk->icsk_ack.pending & ICSK_ACK_PUSHED)
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icsk->icsk_ack.pending |= ICSK_ACK_PUSHED2;
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icsk->icsk_ack.pending |= ICSK_ACK_PUSHED;
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}
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}
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static void tcp_incr_quickack(struct sock *sk)
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{
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struct inet_connection_sock *icsk = inet_csk(sk);
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unsigned int quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss);
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if (quickacks == 0)
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quickacks = 2;
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if (quickacks > icsk->icsk_ack.quick)
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icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS);
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}
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static void tcp_enter_quickack_mode(struct sock *sk)
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{
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struct inet_connection_sock *icsk = inet_csk(sk);
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tcp_incr_quickack(sk);
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icsk->icsk_ack.pingpong = 0;
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icsk->icsk_ack.ato = TCP_ATO_MIN;
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}
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/* Send ACKs quickly, if "quick" count is not exhausted
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* and the session is not interactive.
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*/
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static bool tcp_in_quickack_mode(struct sock *sk)
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{
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const struct inet_connection_sock *icsk = inet_csk(sk);
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const struct dst_entry *dst = __sk_dst_get(sk);
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return (dst && dst_metric(dst, RTAX_QUICKACK)) ||
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(icsk->icsk_ack.quick && !icsk->icsk_ack.pingpong);
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}
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static void tcp_ecn_queue_cwr(struct tcp_sock *tp)
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{
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if (tp->ecn_flags & TCP_ECN_OK)
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tp->ecn_flags |= TCP_ECN_QUEUE_CWR;
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}
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static void tcp_ecn_accept_cwr(struct tcp_sock *tp, const struct sk_buff *skb)
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{
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if (tcp_hdr(skb)->cwr)
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tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR;
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}
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static void tcp_ecn_withdraw_cwr(struct tcp_sock *tp)
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{
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tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR;
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}
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static void __tcp_ecn_check_ce(struct tcp_sock *tp, const struct sk_buff *skb)
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{
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switch (TCP_SKB_CB(skb)->ip_dsfield & INET_ECN_MASK) {
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case INET_ECN_NOT_ECT:
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/* Funny extension: if ECT is not set on a segment,
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* and we already seen ECT on a previous segment,
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* it is probably a retransmit.
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*/
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if (tp->ecn_flags & TCP_ECN_SEEN)
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tcp_enter_quickack_mode((struct sock *)tp);
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break;
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case INET_ECN_CE:
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if (tcp_ca_needs_ecn((struct sock *)tp))
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tcp_ca_event((struct sock *)tp, CA_EVENT_ECN_IS_CE);
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if (!(tp->ecn_flags & TCP_ECN_DEMAND_CWR)) {
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/* Better not delay acks, sender can have a very low cwnd */
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tcp_enter_quickack_mode((struct sock *)tp);
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tp->ecn_flags |= TCP_ECN_DEMAND_CWR;
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}
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tp->ecn_flags |= TCP_ECN_SEEN;
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break;
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default:
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if (tcp_ca_needs_ecn((struct sock *)tp))
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tcp_ca_event((struct sock *)tp, CA_EVENT_ECN_NO_CE);
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tp->ecn_flags |= TCP_ECN_SEEN;
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break;
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}
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}
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static void tcp_ecn_check_ce(struct tcp_sock *tp, const struct sk_buff *skb)
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{
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if (tp->ecn_flags & TCP_ECN_OK)
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__tcp_ecn_check_ce(tp, skb);
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}
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static void tcp_ecn_rcv_synack(struct tcp_sock *tp, const struct tcphdr *th)
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{
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if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || th->cwr))
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tp->ecn_flags &= ~TCP_ECN_OK;
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}
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static void tcp_ecn_rcv_syn(struct tcp_sock *tp, const struct tcphdr *th)
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{
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if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || !th->cwr))
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tp->ecn_flags &= ~TCP_ECN_OK;
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}
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static bool tcp_ecn_rcv_ecn_echo(const struct tcp_sock *tp, const struct tcphdr *th)
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{
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if (th->ece && !th->syn && (tp->ecn_flags & TCP_ECN_OK))
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return true;
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return false;
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}
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/* Buffer size and advertised window tuning.
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*
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* 1. Tuning sk->sk_sndbuf, when connection enters established state.
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*/
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static void tcp_sndbuf_expand(struct sock *sk)
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{
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const struct tcp_sock *tp = tcp_sk(sk);
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int sndmem, per_mss;
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u32 nr_segs;
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/* Worst case is non GSO/TSO : each frame consumes one skb
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* and skb->head is kmalloced using power of two area of memory
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*/
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per_mss = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) +
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MAX_TCP_HEADER +
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SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
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per_mss = roundup_pow_of_two(per_mss) +
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SKB_DATA_ALIGN(sizeof(struct sk_buff));
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nr_segs = max_t(u32, TCP_INIT_CWND, tp->snd_cwnd);
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nr_segs = max_t(u32, nr_segs, tp->reordering + 1);
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/* Fast Recovery (RFC 5681 3.2) :
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* Cubic needs 1.7 factor, rounded to 2 to include
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* extra cushion (application might react slowly to POLLOUT)
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*/
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sndmem = 2 * nr_segs * per_mss;
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if (sk->sk_sndbuf < sndmem)
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sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]);
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}
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/* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
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*
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* All tcp_full_space() is split to two parts: "network" buffer, allocated
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* forward and advertised in receiver window (tp->rcv_wnd) and
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* "application buffer", required to isolate scheduling/application
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* latencies from network.
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* window_clamp is maximal advertised window. It can be less than
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* tcp_full_space(), in this case tcp_full_space() - window_clamp
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* is reserved for "application" buffer. The less window_clamp is
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* the smoother our behaviour from viewpoint of network, but the lower
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* throughput and the higher sensitivity of the connection to losses. 8)
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*
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* rcv_ssthresh is more strict window_clamp used at "slow start"
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* phase to predict further behaviour of this connection.
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* It is used for two goals:
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* - to enforce header prediction at sender, even when application
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* requires some significant "application buffer". It is check #1.
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* - to prevent pruning of receive queue because of misprediction
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* of receiver window. Check #2.
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*
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* The scheme does not work when sender sends good segments opening
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* window and then starts to feed us spaghetti. But it should work
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* in common situations. Otherwise, we have to rely on queue collapsing.
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*/
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/* Slow part of check#2. */
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static int __tcp_grow_window(const struct sock *sk, const struct sk_buff *skb)
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{
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struct tcp_sock *tp = tcp_sk(sk);
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/* Optimize this! */
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int truesize = tcp_win_from_space(skb->truesize) >> 1;
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int window = tcp_win_from_space(sysctl_tcp_rmem[2]) >> 1;
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while (tp->rcv_ssthresh <= window) {
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if (truesize <= skb->len)
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return 2 * inet_csk(sk)->icsk_ack.rcv_mss;
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truesize >>= 1;
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window >>= 1;
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}
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return 0;
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}
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static void tcp_grow_window(struct sock *sk, const struct sk_buff *skb)
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{
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struct tcp_sock *tp = tcp_sk(sk);
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/* Check #1 */
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if (tp->rcv_ssthresh < tp->window_clamp &&
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(int)tp->rcv_ssthresh < tcp_space(sk) &&
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!tcp_under_memory_pressure(sk)) {
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int incr;
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/* Check #2. Increase window, if skb with such overhead
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* will fit to rcvbuf in future.
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*/
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if (tcp_win_from_space(skb->truesize) <= skb->len)
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incr = 2 * tp->advmss;
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else
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incr = __tcp_grow_window(sk, skb);
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if (incr) {
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incr = max_t(int, incr, 2 * skb->len);
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tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr,
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tp->window_clamp);
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inet_csk(sk)->icsk_ack.quick |= 1;
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}
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}
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}
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/* 3. Tuning rcvbuf, when connection enters established state. */
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static void tcp_fixup_rcvbuf(struct sock *sk)
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{
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u32 mss = tcp_sk(sk)->advmss;
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int rcvmem;
|
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rcvmem = 2 * SKB_TRUESIZE(mss + MAX_TCP_HEADER) *
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tcp_default_init_rwnd(mss);
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|
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/* Dynamic Right Sizing (DRS) has 2 to 3 RTT latency
|
|
* Allow enough cushion so that sender is not limited by our window
|
|
*/
|
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if (sysctl_tcp_moderate_rcvbuf)
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rcvmem <<= 2;
|
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|
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if (sk->sk_rcvbuf < rcvmem)
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sk->sk_rcvbuf = min(rcvmem, sysctl_tcp_rmem[2]);
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}
|
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|
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/* 4. Try to fixup all. It is made immediately after connection enters
|
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* established state.
|
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*/
|
|
void tcp_init_buffer_space(struct sock *sk)
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{
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struct tcp_sock *tp = tcp_sk(sk);
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int maxwin;
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|
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if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK))
|
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tcp_fixup_rcvbuf(sk);
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if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK))
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tcp_sndbuf_expand(sk);
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tp->rcvq_space.space = tp->rcv_wnd;
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tp->rcvq_space.time = tcp_time_stamp;
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tp->rcvq_space.seq = tp->copied_seq;
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|
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maxwin = tcp_full_space(sk);
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|
|
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if (tp->window_clamp >= maxwin) {
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tp->window_clamp = maxwin;
|
|
|
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if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss)
|
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tp->window_clamp = max(maxwin -
|
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(maxwin >> sysctl_tcp_app_win),
|
|
4 * tp->advmss);
|
|
}
|
|
|
|
/* Force reservation of one segment. */
|
|
if (sysctl_tcp_app_win &&
|
|
tp->window_clamp > 2 * tp->advmss &&
|
|
tp->window_clamp + tp->advmss > maxwin)
|
|
tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss);
|
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|
|
tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp);
|
|
tp->snd_cwnd_stamp = tcp_time_stamp;
|
|
}
|
|
|
|
/* 5. Recalculate window clamp after socket hit its memory bounds. */
|
|
static void tcp_clamp_window(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct inet_connection_sock *icsk = inet_csk(sk);
|
|
|
|
icsk->icsk_ack.quick = 0;
|
|
|
|
if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] &&
|
|
!(sk->sk_userlocks & SOCK_RCVBUF_LOCK) &&
|
|
!tcp_under_memory_pressure(sk) &&
|
|
sk_memory_allocated(sk) < sk_prot_mem_limits(sk, 0)) {
|
|
sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc),
|
|
sysctl_tcp_rmem[2]);
|
|
}
|
|
if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf)
|
|
tp->rcv_ssthresh = min(tp->window_clamp, 2U * tp->advmss);
|
|
}
|
|
|
|
/* Initialize RCV_MSS value.
|
|
* RCV_MSS is an our guess about MSS used by the peer.
|
|
* We haven't any direct information about the MSS.
|
|
* It's better to underestimate the RCV_MSS rather than overestimate.
|
|
* Overestimations make us ACKing less frequently than needed.
|
|
* Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
|
|
*/
|
|
void tcp_initialize_rcv_mss(struct sock *sk)
|
|
{
|
|
const struct tcp_sock *tp = tcp_sk(sk);
|
|
unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache);
|
|
|
|
hint = min(hint, tp->rcv_wnd / 2);
|
|
hint = min(hint, TCP_MSS_DEFAULT);
|
|
hint = max(hint, TCP_MIN_MSS);
|
|
|
|
inet_csk(sk)->icsk_ack.rcv_mss = hint;
|
|
}
|
|
EXPORT_SYMBOL(tcp_initialize_rcv_mss);
|
|
|
|
/* Receiver "autotuning" code.
|
|
*
|
|
* The algorithm for RTT estimation w/o timestamps is based on
|
|
* Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
|
|
* <http://public.lanl.gov/radiant/pubs.html#DRS>
|
|
*
|
|
* More detail on this code can be found at
|
|
* <http://staff.psc.edu/jheffner/>,
|
|
* though this reference is out of date. A new paper
|
|
* is pending.
|
|
*/
|
|
static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep)
|
|
{
|
|
u32 new_sample = tp->rcv_rtt_est.rtt;
|
|
long m = sample;
|
|
|
|
if (m == 0)
|
|
m = 1;
|
|
|
|
if (new_sample != 0) {
|
|
/* If we sample in larger samples in the non-timestamp
|
|
* case, we could grossly overestimate the RTT especially
|
|
* with chatty applications or bulk transfer apps which
|
|
* are stalled on filesystem I/O.
|
|
*
|
|
* Also, since we are only going for a minimum in the
|
|
* non-timestamp case, we do not smooth things out
|
|
* else with timestamps disabled convergence takes too
|
|
* long.
|
|
*/
|
|
if (!win_dep) {
|
|
m -= (new_sample >> 3);
|
|
new_sample += m;
|
|
} else {
|
|
m <<= 3;
|
|
if (m < new_sample)
|
|
new_sample = m;
|
|
}
|
|
} else {
|
|
/* No previous measure. */
|
|
new_sample = m << 3;
|
|
}
|
|
|
|
if (tp->rcv_rtt_est.rtt != new_sample)
|
|
tp->rcv_rtt_est.rtt = new_sample;
|
|
}
|
|
|
|
static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp)
|
|
{
|
|
if (tp->rcv_rtt_est.time == 0)
|
|
goto new_measure;
|
|
if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq))
|
|
return;
|
|
tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rcv_rtt_est.time, 1);
|
|
|
|
new_measure:
|
|
tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd;
|
|
tp->rcv_rtt_est.time = tcp_time_stamp;
|
|
}
|
|
|
|
static inline void tcp_rcv_rtt_measure_ts(struct sock *sk,
|
|
const struct sk_buff *skb)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
if (tp->rx_opt.rcv_tsecr &&
|
|
(TCP_SKB_CB(skb)->end_seq -
|
|
TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss))
|
|
tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0);
|
|
}
|
|
|
|
/*
|
|
* This function should be called every time data is copied to user space.
|
|
* It calculates the appropriate TCP receive buffer space.
|
|
*/
|
|
void tcp_rcv_space_adjust(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
int time;
|
|
int copied;
|
|
|
|
time = tcp_time_stamp - tp->rcvq_space.time;
|
|
if (time < (tp->rcv_rtt_est.rtt >> 3) || tp->rcv_rtt_est.rtt == 0)
|
|
return;
|
|
|
|
/* Number of bytes copied to user in last RTT */
|
|
copied = tp->copied_seq - tp->rcvq_space.seq;
|
|
if (copied <= tp->rcvq_space.space)
|
|
goto new_measure;
|
|
|
|
/* A bit of theory :
|
|
* copied = bytes received in previous RTT, our base window
|
|
* To cope with packet losses, we need a 2x factor
|
|
* To cope with slow start, and sender growing its cwin by 100 %
|
|
* every RTT, we need a 4x factor, because the ACK we are sending
|
|
* now is for the next RTT, not the current one :
|
|
* <prev RTT . ><current RTT .. ><next RTT .... >
|
|
*/
|
|
|
|
if (sysctl_tcp_moderate_rcvbuf &&
|
|
!(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) {
|
|
int rcvwin, rcvmem, rcvbuf;
|
|
|
|
/* minimal window to cope with packet losses, assuming
|
|
* steady state. Add some cushion because of small variations.
|
|
*/
|
|
rcvwin = (copied << 1) + 16 * tp->advmss;
|
|
|
|
/* If rate increased by 25%,
|
|
* assume slow start, rcvwin = 3 * copied
|
|
* If rate increased by 50%,
|
|
* assume sender can use 2x growth, rcvwin = 4 * copied
|
|
*/
|
|
if (copied >=
|
|
tp->rcvq_space.space + (tp->rcvq_space.space >> 2)) {
|
|
if (copied >=
|
|
tp->rcvq_space.space + (tp->rcvq_space.space >> 1))
|
|
rcvwin <<= 1;
|
|
else
|
|
rcvwin += (rcvwin >> 1);
|
|
}
|
|
|
|
rcvmem = SKB_TRUESIZE(tp->advmss + MAX_TCP_HEADER);
|
|
while (tcp_win_from_space(rcvmem) < tp->advmss)
|
|
rcvmem += 128;
|
|
|
|
rcvbuf = min(rcvwin / tp->advmss * rcvmem, sysctl_tcp_rmem[2]);
|
|
if (rcvbuf > sk->sk_rcvbuf) {
|
|
sk->sk_rcvbuf = rcvbuf;
|
|
|
|
/* Make the window clamp follow along. */
|
|
tp->window_clamp = rcvwin;
|
|
}
|
|
}
|
|
tp->rcvq_space.space = copied;
|
|
|
|
new_measure:
|
|
tp->rcvq_space.seq = tp->copied_seq;
|
|
tp->rcvq_space.time = tcp_time_stamp;
|
|
}
|
|
|
|
/* There is something which you must keep in mind when you analyze the
|
|
* behavior of the tp->ato delayed ack timeout interval. When a
|
|
* connection starts up, we want to ack as quickly as possible. The
|
|
* problem is that "good" TCP's do slow start at the beginning of data
|
|
* transmission. The means that until we send the first few ACK's the
|
|
* sender will sit on his end and only queue most of his data, because
|
|
* he can only send snd_cwnd unacked packets at any given time. For
|
|
* each ACK we send, he increments snd_cwnd and transmits more of his
|
|
* queue. -DaveM
|
|
*/
|
|
static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct inet_connection_sock *icsk = inet_csk(sk);
|
|
u32 now;
|
|
|
|
inet_csk_schedule_ack(sk);
|
|
|
|
tcp_measure_rcv_mss(sk, skb);
|
|
|
|
tcp_rcv_rtt_measure(tp);
|
|
|
|
now = tcp_time_stamp;
|
|
|
|
if (!icsk->icsk_ack.ato) {
|
|
/* The _first_ data packet received, initialize
|
|
* delayed ACK engine.
|
|
*/
|
|
tcp_incr_quickack(sk);
|
|
icsk->icsk_ack.ato = TCP_ATO_MIN;
|
|
} else {
|
|
int m = now - icsk->icsk_ack.lrcvtime;
|
|
|
|
if (m <= TCP_ATO_MIN / 2) {
|
|
/* The fastest case is the first. */
|
|
icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2;
|
|
} else if (m < icsk->icsk_ack.ato) {
|
|
icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m;
|
|
if (icsk->icsk_ack.ato > icsk->icsk_rto)
|
|
icsk->icsk_ack.ato = icsk->icsk_rto;
|
|
} else if (m > icsk->icsk_rto) {
|
|
/* Too long gap. Apparently sender failed to
|
|
* restart window, so that we send ACKs quickly.
|
|
*/
|
|
tcp_incr_quickack(sk);
|
|
sk_mem_reclaim(sk);
|
|
}
|
|
}
|
|
icsk->icsk_ack.lrcvtime = now;
|
|
|
|
tcp_ecn_check_ce(tp, skb);
|
|
|
|
if (skb->len >= 128)
|
|
tcp_grow_window(sk, skb);
|
|
}
|
|
|
|
/* Called to compute a smoothed rtt estimate. The data fed to this
|
|
* routine either comes from timestamps, or from segments that were
|
|
* known _not_ to have been retransmitted [see Karn/Partridge
|
|
* Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
|
|
* piece by Van Jacobson.
|
|
* NOTE: the next three routines used to be one big routine.
|
|
* To save cycles in the RFC 1323 implementation it was better to break
|
|
* it up into three procedures. -- erics
|
|
*/
|
|
static void tcp_rtt_estimator(struct sock *sk, long mrtt_us)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
long m = mrtt_us; /* RTT */
|
|
u32 srtt = tp->srtt_us;
|
|
|
|
/* The following amusing code comes from Jacobson's
|
|
* article in SIGCOMM '88. Note that rtt and mdev
|
|
* are scaled versions of rtt and mean deviation.
|
|
* This is designed to be as fast as possible
|
|
* m stands for "measurement".
|
|
*
|
|
* On a 1990 paper the rto value is changed to:
|
|
* RTO = rtt + 4 * mdev
|
|
*
|
|
* Funny. This algorithm seems to be very broken.
|
|
* These formulae increase RTO, when it should be decreased, increase
|
|
* too slowly, when it should be increased quickly, decrease too quickly
|
|
* etc. I guess in BSD RTO takes ONE value, so that it is absolutely
|
|
* does not matter how to _calculate_ it. Seems, it was trap
|
|
* that VJ failed to avoid. 8)
|
|
*/
|
|
if (srtt != 0) {
|
|
m -= (srtt >> 3); /* m is now error in rtt est */
|
|
srtt += m; /* rtt = 7/8 rtt + 1/8 new */
|
|
if (m < 0) {
|
|
m = -m; /* m is now abs(error) */
|
|
m -= (tp->mdev_us >> 2); /* similar update on mdev */
|
|
/* This is similar to one of Eifel findings.
|
|
* Eifel blocks mdev updates when rtt decreases.
|
|
* This solution is a bit different: we use finer gain
|
|
* for mdev in this case (alpha*beta).
|
|
* Like Eifel it also prevents growth of rto,
|
|
* but also it limits too fast rto decreases,
|
|
* happening in pure Eifel.
|
|
*/
|
|
if (m > 0)
|
|
m >>= 3;
|
|
} else {
|
|
m -= (tp->mdev_us >> 2); /* similar update on mdev */
|
|
}
|
|
tp->mdev_us += m; /* mdev = 3/4 mdev + 1/4 new */
|
|
if (tp->mdev_us > tp->mdev_max_us) {
|
|
tp->mdev_max_us = tp->mdev_us;
|
|
if (tp->mdev_max_us > tp->rttvar_us)
|
|
tp->rttvar_us = tp->mdev_max_us;
|
|
}
|
|
if (after(tp->snd_una, tp->rtt_seq)) {
|
|
if (tp->mdev_max_us < tp->rttvar_us)
|
|
tp->rttvar_us -= (tp->rttvar_us - tp->mdev_max_us) >> 2;
|
|
tp->rtt_seq = tp->snd_nxt;
|
|
tp->mdev_max_us = tcp_rto_min_us(sk);
|
|
}
|
|
} else {
|
|
/* no previous measure. */
|
|
srtt = m << 3; /* take the measured time to be rtt */
|
|
tp->mdev_us = m << 1; /* make sure rto = 3*rtt */
|
|
tp->rttvar_us = max(tp->mdev_us, tcp_rto_min_us(sk));
|
|
tp->mdev_max_us = tp->rttvar_us;
|
|
tp->rtt_seq = tp->snd_nxt;
|
|
}
|
|
tp->srtt_us = max(1U, srtt);
|
|
}
|
|
|
|
/* Set the sk_pacing_rate to allow proper sizing of TSO packets.
|
|
* Note: TCP stack does not yet implement pacing.
|
|
* FQ packet scheduler can be used to implement cheap but effective
|
|
* TCP pacing, to smooth the burst on large writes when packets
|
|
* in flight is significantly lower than cwnd (or rwin)
|
|
*/
|
|
int sysctl_tcp_pacing_ss_ratio __read_mostly = 200;
|
|
int sysctl_tcp_pacing_ca_ratio __read_mostly = 120;
|
|
|
|
static void tcp_update_pacing_rate(struct sock *sk)
|
|
{
|
|
const struct tcp_sock *tp = tcp_sk(sk);
|
|
u64 rate;
|
|
|
|
/* set sk_pacing_rate to 200 % of current rate (mss * cwnd / srtt) */
|
|
rate = (u64)tp->mss_cache * ((USEC_PER_SEC / 100) << 3);
|
|
|
|
/* current rate is (cwnd * mss) / srtt
|
|
* In Slow Start [1], set sk_pacing_rate to 200 % the current rate.
|
|
* In Congestion Avoidance phase, set it to 120 % the current rate.
|
|
*
|
|
* [1] : Normal Slow Start condition is (tp->snd_cwnd < tp->snd_ssthresh)
|
|
* If snd_cwnd >= (tp->snd_ssthresh / 2), we are approaching
|
|
* end of slow start and should slow down.
|
|
*/
|
|
if (tp->snd_cwnd < tp->snd_ssthresh / 2)
|
|
rate *= sysctl_tcp_pacing_ss_ratio;
|
|
else
|
|
rate *= sysctl_tcp_pacing_ca_ratio;
|
|
|
|
rate *= max(tp->snd_cwnd, tp->packets_out);
|
|
|
|
if (likely(tp->srtt_us))
|
|
do_div(rate, tp->srtt_us);
|
|
|
|
/* ACCESS_ONCE() is needed because sch_fq fetches sk_pacing_rate
|
|
* without any lock. We want to make sure compiler wont store
|
|
* intermediate values in this location.
|
|
*/
|
|
ACCESS_ONCE(sk->sk_pacing_rate) = min_t(u64, rate,
|
|
sk->sk_max_pacing_rate);
|
|
}
|
|
|
|
/* Calculate rto without backoff. This is the second half of Van Jacobson's
|
|
* routine referred to above.
|
|
*/
|
|
static void tcp_set_rto(struct sock *sk)
|
|
{
|
|
const struct tcp_sock *tp = tcp_sk(sk);
|
|
/* Old crap is replaced with new one. 8)
|
|
*
|
|
* More seriously:
|
|
* 1. If rtt variance happened to be less 50msec, it is hallucination.
|
|
* It cannot be less due to utterly erratic ACK generation made
|
|
* at least by solaris and freebsd. "Erratic ACKs" has _nothing_
|
|
* to do with delayed acks, because at cwnd>2 true delack timeout
|
|
* is invisible. Actually, Linux-2.4 also generates erratic
|
|
* ACKs in some circumstances.
|
|
*/
|
|
inet_csk(sk)->icsk_rto = __tcp_set_rto(tp);
|
|
|
|
/* 2. Fixups made earlier cannot be right.
|
|
* If we do not estimate RTO correctly without them,
|
|
* all the algo is pure shit and should be replaced
|
|
* with correct one. It is exactly, which we pretend to do.
|
|
*/
|
|
|
|
/* NOTE: clamping at TCP_RTO_MIN is not required, current algo
|
|
* guarantees that rto is higher.
|
|
*/
|
|
tcp_bound_rto(sk);
|
|
}
|
|
|
|
__u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst)
|
|
{
|
|
__u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0);
|
|
|
|
if (!cwnd)
|
|
cwnd = TCP_INIT_CWND;
|
|
return min_t(__u32, cwnd, tp->snd_cwnd_clamp);
|
|
}
|
|
|
|
/*
|
|
* Packet counting of FACK is based on in-order assumptions, therefore TCP
|
|
* disables it when reordering is detected
|
|
*/
|
|
void tcp_disable_fack(struct tcp_sock *tp)
|
|
{
|
|
/* RFC3517 uses different metric in lost marker => reset on change */
|
|
if (tcp_is_fack(tp))
|
|
tp->lost_skb_hint = NULL;
|
|
tp->rx_opt.sack_ok &= ~TCP_FACK_ENABLED;
|
|
}
|
|
|
|
/* Take a notice that peer is sending D-SACKs */
|
|
static void tcp_dsack_seen(struct tcp_sock *tp)
|
|
{
|
|
tp->rx_opt.sack_ok |= TCP_DSACK_SEEN;
|
|
}
|
|
|
|
static void tcp_update_reordering(struct sock *sk, const int metric,
|
|
const int ts)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
if (metric > tp->reordering) {
|
|
int mib_idx;
|
|
|
|
tp->reordering = min(sysctl_tcp_max_reordering, metric);
|
|
|
|
/* This exciting event is worth to be remembered. 8) */
|
|
if (ts)
|
|
mib_idx = LINUX_MIB_TCPTSREORDER;
|
|
else if (tcp_is_reno(tp))
|
|
mib_idx = LINUX_MIB_TCPRENOREORDER;
|
|
else if (tcp_is_fack(tp))
|
|
mib_idx = LINUX_MIB_TCPFACKREORDER;
|
|
else
|
|
mib_idx = LINUX_MIB_TCPSACKREORDER;
|
|
|
|
NET_INC_STATS_BH(sock_net(sk), mib_idx);
|
|
#if FASTRETRANS_DEBUG > 1
|
|
pr_debug("Disorder%d %d %u f%u s%u rr%d\n",
|
|
tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state,
|
|
tp->reordering,
|
|
tp->fackets_out,
|
|
tp->sacked_out,
|
|
tp->undo_marker ? tp->undo_retrans : 0);
|
|
#endif
|
|
tcp_disable_fack(tp);
|
|
}
|
|
|
|
if (metric > 0)
|
|
tcp_disable_early_retrans(tp);
|
|
}
|
|
|
|
/* This must be called before lost_out is incremented */
|
|
static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb)
|
|
{
|
|
if (!tp->retransmit_skb_hint ||
|
|
before(TCP_SKB_CB(skb)->seq,
|
|
TCP_SKB_CB(tp->retransmit_skb_hint)->seq))
|
|
tp->retransmit_skb_hint = skb;
|
|
|
|
if (!tp->lost_out ||
|
|
after(TCP_SKB_CB(skb)->end_seq, tp->retransmit_high))
|
|
tp->retransmit_high = TCP_SKB_CB(skb)->end_seq;
|
|
}
|
|
|
|
static void tcp_skb_mark_lost(struct tcp_sock *tp, struct sk_buff *skb)
|
|
{
|
|
if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) {
|
|
tcp_verify_retransmit_hint(tp, skb);
|
|
|
|
tp->lost_out += tcp_skb_pcount(skb);
|
|
TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
|
|
}
|
|
}
|
|
|
|
static void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp,
|
|
struct sk_buff *skb)
|
|
{
|
|
tcp_verify_retransmit_hint(tp, skb);
|
|
|
|
if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) {
|
|
tp->lost_out += tcp_skb_pcount(skb);
|
|
TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
|
|
}
|
|
}
|
|
|
|
/* This procedure tags the retransmission queue when SACKs arrive.
|
|
*
|
|
* We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
|
|
* Packets in queue with these bits set are counted in variables
|
|
* sacked_out, retrans_out and lost_out, correspondingly.
|
|
*
|
|
* Valid combinations are:
|
|
* Tag InFlight Description
|
|
* 0 1 - orig segment is in flight.
|
|
* S 0 - nothing flies, orig reached receiver.
|
|
* L 0 - nothing flies, orig lost by net.
|
|
* R 2 - both orig and retransmit are in flight.
|
|
* L|R 1 - orig is lost, retransmit is in flight.
|
|
* S|R 1 - orig reached receiver, retrans is still in flight.
|
|
* (L|S|R is logically valid, it could occur when L|R is sacked,
|
|
* but it is equivalent to plain S and code short-curcuits it to S.
|
|
* L|S is logically invalid, it would mean -1 packet in flight 8))
|
|
*
|
|
* These 6 states form finite state machine, controlled by the following events:
|
|
* 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
|
|
* 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
|
|
* 3. Loss detection event of two flavors:
|
|
* A. Scoreboard estimator decided the packet is lost.
|
|
* A'. Reno "three dupacks" marks head of queue lost.
|
|
* A''. Its FACK modification, head until snd.fack is lost.
|
|
* B. SACK arrives sacking SND.NXT at the moment, when the
|
|
* segment was retransmitted.
|
|
* 4. D-SACK added new rule: D-SACK changes any tag to S.
|
|
*
|
|
* It is pleasant to note, that state diagram turns out to be commutative,
|
|
* so that we are allowed not to be bothered by order of our actions,
|
|
* when multiple events arrive simultaneously. (see the function below).
|
|
*
|
|
* Reordering detection.
|
|
* --------------------
|
|
* Reordering metric is maximal distance, which a packet can be displaced
|
|
* in packet stream. With SACKs we can estimate it:
|
|
*
|
|
* 1. SACK fills old hole and the corresponding segment was not
|
|
* ever retransmitted -> reordering. Alas, we cannot use it
|
|
* when segment was retransmitted.
|
|
* 2. The last flaw is solved with D-SACK. D-SACK arrives
|
|
* for retransmitted and already SACKed segment -> reordering..
|
|
* Both of these heuristics are not used in Loss state, when we cannot
|
|
* account for retransmits accurately.
|
|
*
|
|
* SACK block validation.
|
|
* ----------------------
|
|
*
|
|
* SACK block range validation checks that the received SACK block fits to
|
|
* the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
|
|
* Note that SND.UNA is not included to the range though being valid because
|
|
* it means that the receiver is rather inconsistent with itself reporting
|
|
* SACK reneging when it should advance SND.UNA. Such SACK block this is
|
|
* perfectly valid, however, in light of RFC2018 which explicitly states
|
|
* that "SACK block MUST reflect the newest segment. Even if the newest
|
|
* segment is going to be discarded ...", not that it looks very clever
|
|
* in case of head skb. Due to potentional receiver driven attacks, we
|
|
* choose to avoid immediate execution of a walk in write queue due to
|
|
* reneging and defer head skb's loss recovery to standard loss recovery
|
|
* procedure that will eventually trigger (nothing forbids us doing this).
|
|
*
|
|
* Implements also blockage to start_seq wrap-around. Problem lies in the
|
|
* fact that though start_seq (s) is before end_seq (i.e., not reversed),
|
|
* there's no guarantee that it will be before snd_nxt (n). The problem
|
|
* happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
|
|
* wrap (s_w):
|
|
*
|
|
* <- outs wnd -> <- wrapzone ->
|
|
* u e n u_w e_w s n_w
|
|
* | | | | | | |
|
|
* |<------------+------+----- TCP seqno space --------------+---------->|
|
|
* ...-- <2^31 ->| |<--------...
|
|
* ...---- >2^31 ------>| |<--------...
|
|
*
|
|
* Current code wouldn't be vulnerable but it's better still to discard such
|
|
* crazy SACK blocks. Doing this check for start_seq alone closes somewhat
|
|
* similar case (end_seq after snd_nxt wrap) as earlier reversed check in
|
|
* snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
|
|
* equal to the ideal case (infinite seqno space without wrap caused issues).
|
|
*
|
|
* With D-SACK the lower bound is extended to cover sequence space below
|
|
* SND.UNA down to undo_marker, which is the last point of interest. Yet
|
|
* again, D-SACK block must not to go across snd_una (for the same reason as
|
|
* for the normal SACK blocks, explained above). But there all simplicity
|
|
* ends, TCP might receive valid D-SACKs below that. As long as they reside
|
|
* fully below undo_marker they do not affect behavior in anyway and can
|
|
* therefore be safely ignored. In rare cases (which are more or less
|
|
* theoretical ones), the D-SACK will nicely cross that boundary due to skb
|
|
* fragmentation and packet reordering past skb's retransmission. To consider
|
|
* them correctly, the acceptable range must be extended even more though
|
|
* the exact amount is rather hard to quantify. However, tp->max_window can
|
|
* be used as an exaggerated estimate.
|
|
*/
|
|
static bool tcp_is_sackblock_valid(struct tcp_sock *tp, bool is_dsack,
|
|
u32 start_seq, u32 end_seq)
|
|
{
|
|
/* Too far in future, or reversed (interpretation is ambiguous) */
|
|
if (after(end_seq, tp->snd_nxt) || !before(start_seq, end_seq))
|
|
return false;
|
|
|
|
/* Nasty start_seq wrap-around check (see comments above) */
|
|
if (!before(start_seq, tp->snd_nxt))
|
|
return false;
|
|
|
|
/* In outstanding window? ...This is valid exit for D-SACKs too.
|
|
* start_seq == snd_una is non-sensical (see comments above)
|
|
*/
|
|
if (after(start_seq, tp->snd_una))
|
|
return true;
|
|
|
|
if (!is_dsack || !tp->undo_marker)
|
|
return false;
|
|
|
|
/* ...Then it's D-SACK, and must reside below snd_una completely */
|
|
if (after(end_seq, tp->snd_una))
|
|
return false;
|
|
|
|
if (!before(start_seq, tp->undo_marker))
|
|
return true;
|
|
|
|
/* Too old */
|
|
if (!after(end_seq, tp->undo_marker))
|
|
return false;
|
|
|
|
/* Undo_marker boundary crossing (overestimates a lot). Known already:
|
|
* start_seq < undo_marker and end_seq >= undo_marker.
|
|
*/
|
|
return !before(start_seq, end_seq - tp->max_window);
|
|
}
|
|
|
|
/* Check for lost retransmit. This superb idea is borrowed from "ratehalving".
|
|
* Event "B". Later note: FACK people cheated me again 8), we have to account
|
|
* for reordering! Ugly, but should help.
|
|
*
|
|
* Search retransmitted skbs from write_queue that were sent when snd_nxt was
|
|
* less than what is now known to be received by the other end (derived from
|
|
* highest SACK block). Also calculate the lowest snd_nxt among the remaining
|
|
* retransmitted skbs to avoid some costly processing per ACKs.
|
|
*/
|
|
static void tcp_mark_lost_retrans(struct sock *sk, int *flag)
|
|
{
|
|
const struct inet_connection_sock *icsk = inet_csk(sk);
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct sk_buff *skb;
|
|
int cnt = 0;
|
|
u32 new_low_seq = tp->snd_nxt;
|
|
u32 received_upto = tcp_highest_sack_seq(tp);
|
|
|
|
if (!tcp_is_fack(tp) || !tp->retrans_out ||
|
|
!after(received_upto, tp->lost_retrans_low) ||
|
|
icsk->icsk_ca_state != TCP_CA_Recovery)
|
|
return;
|
|
|
|
tcp_for_write_queue(skb, sk) {
|
|
u32 ack_seq = TCP_SKB_CB(skb)->ack_seq;
|
|
|
|
if (skb == tcp_send_head(sk))
|
|
break;
|
|
if (cnt == tp->retrans_out)
|
|
break;
|
|
if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
|
|
continue;
|
|
|
|
if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS))
|
|
continue;
|
|
|
|
/* TODO: We would like to get rid of tcp_is_fack(tp) only
|
|
* constraint here (see above) but figuring out that at
|
|
* least tp->reordering SACK blocks reside between ack_seq
|
|
* and received_upto is not easy task to do cheaply with
|
|
* the available datastructures.
|
|
*
|
|
* Whether FACK should check here for tp->reordering segs
|
|
* in-between one could argue for either way (it would be
|
|
* rather simple to implement as we could count fack_count
|
|
* during the walk and do tp->fackets_out - fack_count).
|
|
*/
|
|
if (after(received_upto, ack_seq)) {
|
|
TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
|
|
tp->retrans_out -= tcp_skb_pcount(skb);
|
|
*flag |= FLAG_LOST_RETRANS;
|
|
tcp_skb_mark_lost_uncond_verify(tp, skb);
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSTRETRANSMIT);
|
|
} else {
|
|
if (before(ack_seq, new_low_seq))
|
|
new_low_seq = ack_seq;
|
|
cnt += tcp_skb_pcount(skb);
|
|
}
|
|
}
|
|
|
|
if (tp->retrans_out)
|
|
tp->lost_retrans_low = new_low_seq;
|
|
}
|
|
|
|
static bool tcp_check_dsack(struct sock *sk, const struct sk_buff *ack_skb,
|
|
struct tcp_sack_block_wire *sp, int num_sacks,
|
|
u32 prior_snd_una)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
u32 start_seq_0 = get_unaligned_be32(&sp[0].start_seq);
|
|
u32 end_seq_0 = get_unaligned_be32(&sp[0].end_seq);
|
|
bool dup_sack = false;
|
|
|
|
if (before(start_seq_0, TCP_SKB_CB(ack_skb)->ack_seq)) {
|
|
dup_sack = true;
|
|
tcp_dsack_seen(tp);
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDSACKRECV);
|
|
} else if (num_sacks > 1) {
|
|
u32 end_seq_1 = get_unaligned_be32(&sp[1].end_seq);
|
|
u32 start_seq_1 = get_unaligned_be32(&sp[1].start_seq);
|
|
|
|
if (!after(end_seq_0, end_seq_1) &&
|
|
!before(start_seq_0, start_seq_1)) {
|
|
dup_sack = true;
|
|
tcp_dsack_seen(tp);
|
|
NET_INC_STATS_BH(sock_net(sk),
|
|
LINUX_MIB_TCPDSACKOFORECV);
|
|
}
|
|
}
|
|
|
|
/* D-SACK for already forgotten data... Do dumb counting. */
|
|
if (dup_sack && tp->undo_marker && tp->undo_retrans > 0 &&
|
|
!after(end_seq_0, prior_snd_una) &&
|
|
after(end_seq_0, tp->undo_marker))
|
|
tp->undo_retrans--;
|
|
|
|
return dup_sack;
|
|
}
|
|
|
|
struct tcp_sacktag_state {
|
|
int reord;
|
|
int fack_count;
|
|
/* Timestamps for earliest and latest never-retransmitted segment
|
|
* that was SACKed. RTO needs the earliest RTT to stay conservative,
|
|
* but congestion control should still get an accurate delay signal.
|
|
*/
|
|
struct skb_mstamp first_sackt;
|
|
struct skb_mstamp last_sackt;
|
|
int flag;
|
|
};
|
|
|
|
/* Check if skb is fully within the SACK block. In presence of GSO skbs,
|
|
* the incoming SACK may not exactly match but we can find smaller MSS
|
|
* aligned portion of it that matches. Therefore we might need to fragment
|
|
* which may fail and creates some hassle (caller must handle error case
|
|
* returns).
|
|
*
|
|
* FIXME: this could be merged to shift decision code
|
|
*/
|
|
static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb,
|
|
u32 start_seq, u32 end_seq)
|
|
{
|
|
int err;
|
|
bool in_sack;
|
|
unsigned int pkt_len;
|
|
unsigned int mss;
|
|
|
|
in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
|
|
!before(end_seq, TCP_SKB_CB(skb)->end_seq);
|
|
|
|
if (tcp_skb_pcount(skb) > 1 && !in_sack &&
|
|
after(TCP_SKB_CB(skb)->end_seq, start_seq)) {
|
|
mss = tcp_skb_mss(skb);
|
|
in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq);
|
|
|
|
if (!in_sack) {
|
|
pkt_len = start_seq - TCP_SKB_CB(skb)->seq;
|
|
if (pkt_len < mss)
|
|
pkt_len = mss;
|
|
} else {
|
|
pkt_len = end_seq - TCP_SKB_CB(skb)->seq;
|
|
if (pkt_len < mss)
|
|
return -EINVAL;
|
|
}
|
|
|
|
/* Round if necessary so that SACKs cover only full MSSes
|
|
* and/or the remaining small portion (if present)
|
|
*/
|
|
if (pkt_len > mss) {
|
|
unsigned int new_len = (pkt_len / mss) * mss;
|
|
if (!in_sack && new_len < pkt_len) {
|
|
new_len += mss;
|
|
if (new_len >= skb->len)
|
|
return 0;
|
|
}
|
|
pkt_len = new_len;
|
|
}
|
|
err = tcp_fragment(sk, skb, pkt_len, mss, GFP_ATOMIC);
|
|
if (err < 0)
|
|
return err;
|
|
}
|
|
|
|
return in_sack;
|
|
}
|
|
|
|
/* Mark the given newly-SACKed range as such, adjusting counters and hints. */
|
|
static u8 tcp_sacktag_one(struct sock *sk,
|
|
struct tcp_sacktag_state *state, u8 sacked,
|
|
u32 start_seq, u32 end_seq,
|
|
int dup_sack, int pcount,
|
|
const struct skb_mstamp *xmit_time)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
int fack_count = state->fack_count;
|
|
|
|
/* Account D-SACK for retransmitted packet. */
|
|
if (dup_sack && (sacked & TCPCB_RETRANS)) {
|
|
if (tp->undo_marker && tp->undo_retrans > 0 &&
|
|
after(end_seq, tp->undo_marker))
|
|
tp->undo_retrans--;
|
|
if (sacked & TCPCB_SACKED_ACKED)
|
|
state->reord = min(fack_count, state->reord);
|
|
}
|
|
|
|
/* Nothing to do; acked frame is about to be dropped (was ACKed). */
|
|
if (!after(end_seq, tp->snd_una))
|
|
return sacked;
|
|
|
|
if (!(sacked & TCPCB_SACKED_ACKED)) {
|
|
if (sacked & TCPCB_SACKED_RETRANS) {
|
|
/* If the segment is not tagged as lost,
|
|
* we do not clear RETRANS, believing
|
|
* that retransmission is still in flight.
|
|
*/
|
|
if (sacked & TCPCB_LOST) {
|
|
sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
|
|
tp->lost_out -= pcount;
|
|
tp->retrans_out -= pcount;
|
|
}
|
|
} else {
|
|
if (!(sacked & TCPCB_RETRANS)) {
|
|
/* New sack for not retransmitted frame,
|
|
* which was in hole. It is reordering.
|
|
*/
|
|
if (before(start_seq,
|
|
tcp_highest_sack_seq(tp)))
|
|
state->reord = min(fack_count,
|
|
state->reord);
|
|
if (!after(end_seq, tp->high_seq))
|
|
state->flag |= FLAG_ORIG_SACK_ACKED;
|
|
if (state->first_sackt.v64 == 0)
|
|
state->first_sackt = *xmit_time;
|
|
state->last_sackt = *xmit_time;
|
|
}
|
|
|
|
if (sacked & TCPCB_LOST) {
|
|
sacked &= ~TCPCB_LOST;
|
|
tp->lost_out -= pcount;
|
|
}
|
|
}
|
|
|
|
sacked |= TCPCB_SACKED_ACKED;
|
|
state->flag |= FLAG_DATA_SACKED;
|
|
tp->sacked_out += pcount;
|
|
|
|
fack_count += pcount;
|
|
|
|
/* Lost marker hint past SACKed? Tweak RFC3517 cnt */
|
|
if (!tcp_is_fack(tp) && tp->lost_skb_hint &&
|
|
before(start_seq, TCP_SKB_CB(tp->lost_skb_hint)->seq))
|
|
tp->lost_cnt_hint += pcount;
|
|
|
|
if (fack_count > tp->fackets_out)
|
|
tp->fackets_out = fack_count;
|
|
}
|
|
|
|
/* D-SACK. We can detect redundant retransmission in S|R and plain R
|
|
* frames and clear it. undo_retrans is decreased above, L|R frames
|
|
* are accounted above as well.
|
|
*/
|
|
if (dup_sack && (sacked & TCPCB_SACKED_RETRANS)) {
|
|
sacked &= ~TCPCB_SACKED_RETRANS;
|
|
tp->retrans_out -= pcount;
|
|
}
|
|
|
|
return sacked;
|
|
}
|
|
|
|
/* Shift newly-SACKed bytes from this skb to the immediately previous
|
|
* already-SACKed sk_buff. Mark the newly-SACKed bytes as such.
|
|
*/
|
|
static bool tcp_shifted_skb(struct sock *sk, struct sk_buff *skb,
|
|
struct tcp_sacktag_state *state,
|
|
unsigned int pcount, int shifted, int mss,
|
|
bool dup_sack)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct sk_buff *prev = tcp_write_queue_prev(sk, skb);
|
|
u32 start_seq = TCP_SKB_CB(skb)->seq; /* start of newly-SACKed */
|
|
u32 end_seq = start_seq + shifted; /* end of newly-SACKed */
|
|
|
|
BUG_ON(!pcount);
|
|
|
|
/* Adjust counters and hints for the newly sacked sequence
|
|
* range but discard the return value since prev is already
|
|
* marked. We must tag the range first because the seq
|
|
* advancement below implicitly advances
|
|
* tcp_highest_sack_seq() when skb is highest_sack.
|
|
*/
|
|
tcp_sacktag_one(sk, state, TCP_SKB_CB(skb)->sacked,
|
|
start_seq, end_seq, dup_sack, pcount,
|
|
&skb->skb_mstamp);
|
|
|
|
if (skb == tp->lost_skb_hint)
|
|
tp->lost_cnt_hint += pcount;
|
|
|
|
TCP_SKB_CB(prev)->end_seq += shifted;
|
|
TCP_SKB_CB(skb)->seq += shifted;
|
|
|
|
tcp_skb_pcount_add(prev, pcount);
|
|
BUG_ON(tcp_skb_pcount(skb) < pcount);
|
|
tcp_skb_pcount_add(skb, -pcount);
|
|
|
|
/* When we're adding to gso_segs == 1, gso_size will be zero,
|
|
* in theory this shouldn't be necessary but as long as DSACK
|
|
* code can come after this skb later on it's better to keep
|
|
* setting gso_size to something.
|
|
*/
|
|
if (!TCP_SKB_CB(prev)->tcp_gso_size)
|
|
TCP_SKB_CB(prev)->tcp_gso_size = mss;
|
|
|
|
/* CHECKME: To clear or not to clear? Mimics normal skb currently */
|
|
if (tcp_skb_pcount(skb) <= 1)
|
|
TCP_SKB_CB(skb)->tcp_gso_size = 0;
|
|
|
|
/* Difference in this won't matter, both ACKed by the same cumul. ACK */
|
|
TCP_SKB_CB(prev)->sacked |= (TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS);
|
|
|
|
if (skb->len > 0) {
|
|
BUG_ON(!tcp_skb_pcount(skb));
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTED);
|
|
return false;
|
|
}
|
|
|
|
/* Whole SKB was eaten :-) */
|
|
|
|
if (skb == tp->retransmit_skb_hint)
|
|
tp->retransmit_skb_hint = prev;
|
|
if (skb == tp->lost_skb_hint) {
|
|
tp->lost_skb_hint = prev;
|
|
tp->lost_cnt_hint -= tcp_skb_pcount(prev);
|
|
}
|
|
|
|
TCP_SKB_CB(prev)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
|
|
if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
|
|
TCP_SKB_CB(prev)->end_seq++;
|
|
|
|
if (skb == tcp_highest_sack(sk))
|
|
tcp_advance_highest_sack(sk, skb);
|
|
|
|
tcp_unlink_write_queue(skb, sk);
|
|
sk_wmem_free_skb(sk, skb);
|
|
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKMERGED);
|
|
|
|
return true;
|
|
}
|
|
|
|
/* I wish gso_size would have a bit more sane initialization than
|
|
* something-or-zero which complicates things
|
|
*/
|
|
static int tcp_skb_seglen(const struct sk_buff *skb)
|
|
{
|
|
return tcp_skb_pcount(skb) == 1 ? skb->len : tcp_skb_mss(skb);
|
|
}
|
|
|
|
/* Shifting pages past head area doesn't work */
|
|
static int skb_can_shift(const struct sk_buff *skb)
|
|
{
|
|
return !skb_headlen(skb) && skb_is_nonlinear(skb);
|
|
}
|
|
|
|
/* Try collapsing SACK blocks spanning across multiple skbs to a single
|
|
* skb.
|
|
*/
|
|
static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb,
|
|
struct tcp_sacktag_state *state,
|
|
u32 start_seq, u32 end_seq,
|
|
bool dup_sack)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct sk_buff *prev;
|
|
int mss;
|
|
int pcount = 0;
|
|
int len;
|
|
int in_sack;
|
|
|
|
if (!sk_can_gso(sk))
|
|
goto fallback;
|
|
|
|
/* Normally R but no L won't result in plain S */
|
|
if (!dup_sack &&
|
|
(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_RETRANS)) == TCPCB_SACKED_RETRANS)
|
|
goto fallback;
|
|
if (!skb_can_shift(skb))
|
|
goto fallback;
|
|
/* This frame is about to be dropped (was ACKed). */
|
|
if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
|
|
goto fallback;
|
|
|
|
/* Can only happen with delayed DSACK + discard craziness */
|
|
if (unlikely(skb == tcp_write_queue_head(sk)))
|
|
goto fallback;
|
|
prev = tcp_write_queue_prev(sk, skb);
|
|
|
|
if ((TCP_SKB_CB(prev)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED)
|
|
goto fallback;
|
|
|
|
in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
|
|
!before(end_seq, TCP_SKB_CB(skb)->end_seq);
|
|
|
|
if (in_sack) {
|
|
len = skb->len;
|
|
pcount = tcp_skb_pcount(skb);
|
|
mss = tcp_skb_seglen(skb);
|
|
|
|
/* TODO: Fix DSACKs to not fragment already SACKed and we can
|
|
* drop this restriction as unnecessary
|
|
*/
|
|
if (mss != tcp_skb_seglen(prev))
|
|
goto fallback;
|
|
} else {
|
|
if (!after(TCP_SKB_CB(skb)->end_seq, start_seq))
|
|
goto noop;
|
|
/* CHECKME: This is non-MSS split case only?, this will
|
|
* cause skipped skbs due to advancing loop btw, original
|
|
* has that feature too
|
|
*/
|
|
if (tcp_skb_pcount(skb) <= 1)
|
|
goto noop;
|
|
|
|
in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq);
|
|
if (!in_sack) {
|
|
/* TODO: head merge to next could be attempted here
|
|
* if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)),
|
|
* though it might not be worth of the additional hassle
|
|
*
|
|
* ...we can probably just fallback to what was done
|
|
* previously. We could try merging non-SACKed ones
|
|
* as well but it probably isn't going to buy off
|
|
* because later SACKs might again split them, and
|
|
* it would make skb timestamp tracking considerably
|
|
* harder problem.
|
|
*/
|
|
goto fallback;
|
|
}
|
|
|
|
len = end_seq - TCP_SKB_CB(skb)->seq;
|
|
BUG_ON(len < 0);
|
|
BUG_ON(len > skb->len);
|
|
|
|
/* MSS boundaries should be honoured or else pcount will
|
|
* severely break even though it makes things bit trickier.
|
|
* Optimize common case to avoid most of the divides
|
|
*/
|
|
mss = tcp_skb_mss(skb);
|
|
|
|
/* TODO: Fix DSACKs to not fragment already SACKed and we can
|
|
* drop this restriction as unnecessary
|
|
*/
|
|
if (mss != tcp_skb_seglen(prev))
|
|
goto fallback;
|
|
|
|
if (len == mss) {
|
|
pcount = 1;
|
|
} else if (len < mss) {
|
|
goto noop;
|
|
} else {
|
|
pcount = len / mss;
|
|
len = pcount * mss;
|
|
}
|
|
}
|
|
|
|
/* tcp_sacktag_one() won't SACK-tag ranges below snd_una */
|
|
if (!after(TCP_SKB_CB(skb)->seq + len, tp->snd_una))
|
|
goto fallback;
|
|
|
|
if (!skb_shift(prev, skb, len))
|
|
goto fallback;
|
|
if (!tcp_shifted_skb(sk, skb, state, pcount, len, mss, dup_sack))
|
|
goto out;
|
|
|
|
/* Hole filled allows collapsing with the next as well, this is very
|
|
* useful when hole on every nth skb pattern happens
|
|
*/
|
|
if (prev == tcp_write_queue_tail(sk))
|
|
goto out;
|
|
skb = tcp_write_queue_next(sk, prev);
|
|
|
|
if (!skb_can_shift(skb) ||
|
|
(skb == tcp_send_head(sk)) ||
|
|
((TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) ||
|
|
(mss != tcp_skb_seglen(skb)))
|
|
goto out;
|
|
|
|
len = skb->len;
|
|
if (skb_shift(prev, skb, len)) {
|
|
pcount += tcp_skb_pcount(skb);
|
|
tcp_shifted_skb(sk, skb, state, tcp_skb_pcount(skb), len, mss, 0);
|
|
}
|
|
|
|
out:
|
|
state->fack_count += pcount;
|
|
return prev;
|
|
|
|
noop:
|
|
return skb;
|
|
|
|
fallback:
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTFALLBACK);
|
|
return NULL;
|
|
}
|
|
|
|
static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk,
|
|
struct tcp_sack_block *next_dup,
|
|
struct tcp_sacktag_state *state,
|
|
u32 start_seq, u32 end_seq,
|
|
bool dup_sack_in)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct sk_buff *tmp;
|
|
|
|
tcp_for_write_queue_from(skb, sk) {
|
|
int in_sack = 0;
|
|
bool dup_sack = dup_sack_in;
|
|
|
|
if (skb == tcp_send_head(sk))
|
|
break;
|
|
|
|
/* queue is in-order => we can short-circuit the walk early */
|
|
if (!before(TCP_SKB_CB(skb)->seq, end_seq))
|
|
break;
|
|
|
|
if (next_dup &&
|
|
before(TCP_SKB_CB(skb)->seq, next_dup->end_seq)) {
|
|
in_sack = tcp_match_skb_to_sack(sk, skb,
|
|
next_dup->start_seq,
|
|
next_dup->end_seq);
|
|
if (in_sack > 0)
|
|
dup_sack = true;
|
|
}
|
|
|
|
/* skb reference here is a bit tricky to get right, since
|
|
* shifting can eat and free both this skb and the next,
|
|
* so not even _safe variant of the loop is enough.
|
|
*/
|
|
if (in_sack <= 0) {
|
|
tmp = tcp_shift_skb_data(sk, skb, state,
|
|
start_seq, end_seq, dup_sack);
|
|
if (tmp) {
|
|
if (tmp != skb) {
|
|
skb = tmp;
|
|
continue;
|
|
}
|
|
|
|
in_sack = 0;
|
|
} else {
|
|
in_sack = tcp_match_skb_to_sack(sk, skb,
|
|
start_seq,
|
|
end_seq);
|
|
}
|
|
}
|
|
|
|
if (unlikely(in_sack < 0))
|
|
break;
|
|
|
|
if (in_sack) {
|
|
TCP_SKB_CB(skb)->sacked =
|
|
tcp_sacktag_one(sk,
|
|
state,
|
|
TCP_SKB_CB(skb)->sacked,
|
|
TCP_SKB_CB(skb)->seq,
|
|
TCP_SKB_CB(skb)->end_seq,
|
|
dup_sack,
|
|
tcp_skb_pcount(skb),
|
|
&skb->skb_mstamp);
|
|
|
|
if (!before(TCP_SKB_CB(skb)->seq,
|
|
tcp_highest_sack_seq(tp)))
|
|
tcp_advance_highest_sack(sk, skb);
|
|
}
|
|
|
|
state->fack_count += tcp_skb_pcount(skb);
|
|
}
|
|
return skb;
|
|
}
|
|
|
|
/* Avoid all extra work that is being done by sacktag while walking in
|
|
* a normal way
|
|
*/
|
|
static struct sk_buff *tcp_sacktag_skip(struct sk_buff *skb, struct sock *sk,
|
|
struct tcp_sacktag_state *state,
|
|
u32 skip_to_seq)
|
|
{
|
|
tcp_for_write_queue_from(skb, sk) {
|
|
if (skb == tcp_send_head(sk))
|
|
break;
|
|
|
|
if (after(TCP_SKB_CB(skb)->end_seq, skip_to_seq))
|
|
break;
|
|
|
|
state->fack_count += tcp_skb_pcount(skb);
|
|
}
|
|
return skb;
|
|
}
|
|
|
|
static struct sk_buff *tcp_maybe_skipping_dsack(struct sk_buff *skb,
|
|
struct sock *sk,
|
|
struct tcp_sack_block *next_dup,
|
|
struct tcp_sacktag_state *state,
|
|
u32 skip_to_seq)
|
|
{
|
|
if (!next_dup)
|
|
return skb;
|
|
|
|
if (before(next_dup->start_seq, skip_to_seq)) {
|
|
skb = tcp_sacktag_skip(skb, sk, state, next_dup->start_seq);
|
|
skb = tcp_sacktag_walk(skb, sk, NULL, state,
|
|
next_dup->start_seq, next_dup->end_seq,
|
|
1);
|
|
}
|
|
|
|
return skb;
|
|
}
|
|
|
|
static int tcp_sack_cache_ok(const struct tcp_sock *tp, const struct tcp_sack_block *cache)
|
|
{
|
|
return cache < tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache);
|
|
}
|
|
|
|
static int
|
|
tcp_sacktag_write_queue(struct sock *sk, const struct sk_buff *ack_skb,
|
|
u32 prior_snd_una, struct tcp_sacktag_state *state)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
const unsigned char *ptr = (skb_transport_header(ack_skb) +
|
|
TCP_SKB_CB(ack_skb)->sacked);
|
|
struct tcp_sack_block_wire *sp_wire = (struct tcp_sack_block_wire *)(ptr+2);
|
|
struct tcp_sack_block sp[TCP_NUM_SACKS];
|
|
struct tcp_sack_block *cache;
|
|
struct sk_buff *skb;
|
|
int num_sacks = min(TCP_NUM_SACKS, (ptr[1] - TCPOLEN_SACK_BASE) >> 3);
|
|
int used_sacks;
|
|
bool found_dup_sack = false;
|
|
int i, j;
|
|
int first_sack_index;
|
|
|
|
state->flag = 0;
|
|
state->reord = tp->packets_out;
|
|
|
|
if (!tp->sacked_out) {
|
|
if (WARN_ON(tp->fackets_out))
|
|
tp->fackets_out = 0;
|
|
tcp_highest_sack_reset(sk);
|
|
}
|
|
|
|
found_dup_sack = tcp_check_dsack(sk, ack_skb, sp_wire,
|
|
num_sacks, prior_snd_una);
|
|
if (found_dup_sack)
|
|
state->flag |= FLAG_DSACKING_ACK;
|
|
|
|
/* Eliminate too old ACKs, but take into
|
|
* account more or less fresh ones, they can
|
|
* contain valid SACK info.
|
|
*/
|
|
if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window))
|
|
return 0;
|
|
|
|
if (!tp->packets_out)
|
|
goto out;
|
|
|
|
used_sacks = 0;
|
|
first_sack_index = 0;
|
|
for (i = 0; i < num_sacks; i++) {
|
|
bool dup_sack = !i && found_dup_sack;
|
|
|
|
sp[used_sacks].start_seq = get_unaligned_be32(&sp_wire[i].start_seq);
|
|
sp[used_sacks].end_seq = get_unaligned_be32(&sp_wire[i].end_seq);
|
|
|
|
if (!tcp_is_sackblock_valid(tp, dup_sack,
|
|
sp[used_sacks].start_seq,
|
|
sp[used_sacks].end_seq)) {
|
|
int mib_idx;
|
|
|
|
if (dup_sack) {
|
|
if (!tp->undo_marker)
|
|
mib_idx = LINUX_MIB_TCPDSACKIGNOREDNOUNDO;
|
|
else
|
|
mib_idx = LINUX_MIB_TCPDSACKIGNOREDOLD;
|
|
} else {
|
|
/* Don't count olds caused by ACK reordering */
|
|
if ((TCP_SKB_CB(ack_skb)->ack_seq != tp->snd_una) &&
|
|
!after(sp[used_sacks].end_seq, tp->snd_una))
|
|
continue;
|
|
mib_idx = LINUX_MIB_TCPSACKDISCARD;
|
|
}
|
|
|
|
NET_INC_STATS_BH(sock_net(sk), mib_idx);
|
|
if (i == 0)
|
|
first_sack_index = -1;
|
|
continue;
|
|
}
|
|
|
|
/* Ignore very old stuff early */
|
|
if (!after(sp[used_sacks].end_seq, prior_snd_una))
|
|
continue;
|
|
|
|
used_sacks++;
|
|
}
|
|
|
|
/* order SACK blocks to allow in order walk of the retrans queue */
|
|
for (i = used_sacks - 1; i > 0; i--) {
|
|
for (j = 0; j < i; j++) {
|
|
if (after(sp[j].start_seq, sp[j + 1].start_seq)) {
|
|
swap(sp[j], sp[j + 1]);
|
|
|
|
/* Track where the first SACK block goes to */
|
|
if (j == first_sack_index)
|
|
first_sack_index = j + 1;
|
|
}
|
|
}
|
|
}
|
|
|
|
skb = tcp_write_queue_head(sk);
|
|
state->fack_count = 0;
|
|
i = 0;
|
|
|
|
if (!tp->sacked_out) {
|
|
/* It's already past, so skip checking against it */
|
|
cache = tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache);
|
|
} else {
|
|
cache = tp->recv_sack_cache;
|
|
/* Skip empty blocks in at head of the cache */
|
|
while (tcp_sack_cache_ok(tp, cache) && !cache->start_seq &&
|
|
!cache->end_seq)
|
|
cache++;
|
|
}
|
|
|
|
while (i < used_sacks) {
|
|
u32 start_seq = sp[i].start_seq;
|
|
u32 end_seq = sp[i].end_seq;
|
|
bool dup_sack = (found_dup_sack && (i == first_sack_index));
|
|
struct tcp_sack_block *next_dup = NULL;
|
|
|
|
if (found_dup_sack && ((i + 1) == first_sack_index))
|
|
next_dup = &sp[i + 1];
|
|
|
|
/* Skip too early cached blocks */
|
|
while (tcp_sack_cache_ok(tp, cache) &&
|
|
!before(start_seq, cache->end_seq))
|
|
cache++;
|
|
|
|
/* Can skip some work by looking recv_sack_cache? */
|
|
if (tcp_sack_cache_ok(tp, cache) && !dup_sack &&
|
|
after(end_seq, cache->start_seq)) {
|
|
|
|
/* Head todo? */
|
|
if (before(start_seq, cache->start_seq)) {
|
|
skb = tcp_sacktag_skip(skb, sk, state,
|
|
start_seq);
|
|
skb = tcp_sacktag_walk(skb, sk, next_dup,
|
|
state,
|
|
start_seq,
|
|
cache->start_seq,
|
|
dup_sack);
|
|
}
|
|
|
|
/* Rest of the block already fully processed? */
|
|
if (!after(end_seq, cache->end_seq))
|
|
goto advance_sp;
|
|
|
|
skb = tcp_maybe_skipping_dsack(skb, sk, next_dup,
|
|
state,
|
|
cache->end_seq);
|
|
|
|
/* ...tail remains todo... */
|
|
if (tcp_highest_sack_seq(tp) == cache->end_seq) {
|
|
/* ...but better entrypoint exists! */
|
|
skb = tcp_highest_sack(sk);
|
|
if (!skb)
|
|
break;
|
|
state->fack_count = tp->fackets_out;
|
|
cache++;
|
|
goto walk;
|
|
}
|
|
|
|
skb = tcp_sacktag_skip(skb, sk, state, cache->end_seq);
|
|
/* Check overlap against next cached too (past this one already) */
|
|
cache++;
|
|
continue;
|
|
}
|
|
|
|
if (!before(start_seq, tcp_highest_sack_seq(tp))) {
|
|
skb = tcp_highest_sack(sk);
|
|
if (!skb)
|
|
break;
|
|
state->fack_count = tp->fackets_out;
|
|
}
|
|
skb = tcp_sacktag_skip(skb, sk, state, start_seq);
|
|
|
|
walk:
|
|
skb = tcp_sacktag_walk(skb, sk, next_dup, state,
|
|
start_seq, end_seq, dup_sack);
|
|
|
|
advance_sp:
|
|
i++;
|
|
}
|
|
|
|
/* Clear the head of the cache sack blocks so we can skip it next time */
|
|
for (i = 0; i < ARRAY_SIZE(tp->recv_sack_cache) - used_sacks; i++) {
|
|
tp->recv_sack_cache[i].start_seq = 0;
|
|
tp->recv_sack_cache[i].end_seq = 0;
|
|
}
|
|
for (j = 0; j < used_sacks; j++)
|
|
tp->recv_sack_cache[i++] = sp[j];
|
|
|
|
if ((state->reord < tp->fackets_out) &&
|
|
((inet_csk(sk)->icsk_ca_state != TCP_CA_Loss) || tp->undo_marker))
|
|
tcp_update_reordering(sk, tp->fackets_out - state->reord, 0);
|
|
|
|
tcp_mark_lost_retrans(sk, &state->flag);
|
|
tcp_verify_left_out(tp);
|
|
out:
|
|
|
|
#if FASTRETRANS_DEBUG > 0
|
|
WARN_ON((int)tp->sacked_out < 0);
|
|
WARN_ON((int)tp->lost_out < 0);
|
|
WARN_ON((int)tp->retrans_out < 0);
|
|
WARN_ON((int)tcp_packets_in_flight(tp) < 0);
|
|
#endif
|
|
return state->flag;
|
|
}
|
|
|
|
/* Limits sacked_out so that sum with lost_out isn't ever larger than
|
|
* packets_out. Returns false if sacked_out adjustement wasn't necessary.
|
|
*/
|
|
static bool tcp_limit_reno_sacked(struct tcp_sock *tp)
|
|
{
|
|
u32 holes;
|
|
|
|
holes = max(tp->lost_out, 1U);
|
|
holes = min(holes, tp->packets_out);
|
|
|
|
if ((tp->sacked_out + holes) > tp->packets_out) {
|
|
tp->sacked_out = tp->packets_out - holes;
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/* If we receive more dupacks than we expected counting segments
|
|
* in assumption of absent reordering, interpret this as reordering.
|
|
* The only another reason could be bug in receiver TCP.
|
|
*/
|
|
static void tcp_check_reno_reordering(struct sock *sk, const int addend)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
if (tcp_limit_reno_sacked(tp))
|
|
tcp_update_reordering(sk, tp->packets_out + addend, 0);
|
|
}
|
|
|
|
/* Emulate SACKs for SACKless connection: account for a new dupack. */
|
|
|
|
static void tcp_add_reno_sack(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
tp->sacked_out++;
|
|
tcp_check_reno_reordering(sk, 0);
|
|
tcp_verify_left_out(tp);
|
|
}
|
|
|
|
/* Account for ACK, ACKing some data in Reno Recovery phase. */
|
|
|
|
static void tcp_remove_reno_sacks(struct sock *sk, int acked)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
if (acked > 0) {
|
|
/* One ACK acked hole. The rest eat duplicate ACKs. */
|
|
if (acked - 1 >= tp->sacked_out)
|
|
tp->sacked_out = 0;
|
|
else
|
|
tp->sacked_out -= acked - 1;
|
|
}
|
|
tcp_check_reno_reordering(sk, acked);
|
|
tcp_verify_left_out(tp);
|
|
}
|
|
|
|
static inline void tcp_reset_reno_sack(struct tcp_sock *tp)
|
|
{
|
|
tp->sacked_out = 0;
|
|
}
|
|
|
|
void tcp_clear_retrans(struct tcp_sock *tp)
|
|
{
|
|
tp->retrans_out = 0;
|
|
tp->lost_out = 0;
|
|
tp->undo_marker = 0;
|
|
tp->undo_retrans = -1;
|
|
tp->fackets_out = 0;
|
|
tp->sacked_out = 0;
|
|
}
|
|
|
|
static inline void tcp_init_undo(struct tcp_sock *tp)
|
|
{
|
|
tp->undo_marker = tp->snd_una;
|
|
/* Retransmission still in flight may cause DSACKs later. */
|
|
tp->undo_retrans = tp->retrans_out ? : -1;
|
|
}
|
|
|
|
/* Enter Loss state. If we detect SACK reneging, forget all SACK information
|
|
* and reset tags completely, otherwise preserve SACKs. If receiver
|
|
* dropped its ofo queue, we will know this due to reneging detection.
|
|
*/
|
|
void tcp_enter_loss(struct sock *sk)
|
|
{
|
|
const struct inet_connection_sock *icsk = inet_csk(sk);
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct sk_buff *skb;
|
|
bool new_recovery = icsk->icsk_ca_state < TCP_CA_Recovery;
|
|
bool is_reneg; /* is receiver reneging on SACKs? */
|
|
|
|
/* Reduce ssthresh if it has not yet been made inside this window. */
|
|
if (icsk->icsk_ca_state <= TCP_CA_Disorder ||
|
|
!after(tp->high_seq, tp->snd_una) ||
|
|
(icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) {
|
|
tp->prior_ssthresh = tcp_current_ssthresh(sk);
|
|
tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
|
|
tcp_ca_event(sk, CA_EVENT_LOSS);
|
|
tcp_init_undo(tp);
|
|
}
|
|
tp->snd_cwnd = 1;
|
|
tp->snd_cwnd_cnt = 0;
|
|
tp->snd_cwnd_stamp = tcp_time_stamp;
|
|
|
|
tp->retrans_out = 0;
|
|
tp->lost_out = 0;
|
|
|
|
if (tcp_is_reno(tp))
|
|
tcp_reset_reno_sack(tp);
|
|
|
|
skb = tcp_write_queue_head(sk);
|
|
is_reneg = skb && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED);
|
|
if (is_reneg) {
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSACKRENEGING);
|
|
tp->sacked_out = 0;
|
|
tp->fackets_out = 0;
|
|
}
|
|
tcp_clear_all_retrans_hints(tp);
|
|
|
|
tcp_for_write_queue(skb, sk) {
|
|
if (skb == tcp_send_head(sk))
|
|
break;
|
|
|
|
TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED;
|
|
if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || is_reneg) {
|
|
TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED;
|
|
TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
|
|
tp->lost_out += tcp_skb_pcount(skb);
|
|
tp->retransmit_high = TCP_SKB_CB(skb)->end_seq;
|
|
}
|
|
}
|
|
tcp_verify_left_out(tp);
|
|
|
|
/* Timeout in disordered state after receiving substantial DUPACKs
|
|
* suggests that the degree of reordering is over-estimated.
|
|
*/
|
|
if (icsk->icsk_ca_state <= TCP_CA_Disorder &&
|
|
tp->sacked_out >= sysctl_tcp_reordering)
|
|
tp->reordering = min_t(unsigned int, tp->reordering,
|
|
sysctl_tcp_reordering);
|
|
tcp_set_ca_state(sk, TCP_CA_Loss);
|
|
tp->high_seq = tp->snd_nxt;
|
|
tcp_ecn_queue_cwr(tp);
|
|
|
|
/* F-RTO RFC5682 sec 3.1 step 1: retransmit SND.UNA if no previous
|
|
* loss recovery is underway except recurring timeout(s) on
|
|
* the same SND.UNA (sec 3.2). Disable F-RTO on path MTU probing
|
|
*/
|
|
tp->frto = sysctl_tcp_frto &&
|
|
(new_recovery || icsk->icsk_retransmits) &&
|
|
!inet_csk(sk)->icsk_mtup.probe_size;
|
|
}
|
|
|
|
/* If ACK arrived pointing to a remembered SACK, it means that our
|
|
* remembered SACKs do not reflect real state of receiver i.e.
|
|
* receiver _host_ is heavily congested (or buggy).
|
|
*
|
|
* To avoid big spurious retransmission bursts due to transient SACK
|
|
* scoreboard oddities that look like reneging, we give the receiver a
|
|
* little time (max(RTT/2, 10ms)) to send us some more ACKs that will
|
|
* restore sanity to the SACK scoreboard. If the apparent reneging
|
|
* persists until this RTO then we'll clear the SACK scoreboard.
|
|
*/
|
|
static bool tcp_check_sack_reneging(struct sock *sk, int flag)
|
|
{
|
|
if (flag & FLAG_SACK_RENEGING) {
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
unsigned long delay = max(usecs_to_jiffies(tp->srtt_us >> 4),
|
|
msecs_to_jiffies(10));
|
|
|
|
inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
|
|
delay, TCP_RTO_MAX);
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
static inline int tcp_fackets_out(const struct tcp_sock *tp)
|
|
{
|
|
return tcp_is_reno(tp) ? tp->sacked_out + 1 : tp->fackets_out;
|
|
}
|
|
|
|
/* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
|
|
* counter when SACK is enabled (without SACK, sacked_out is used for
|
|
* that purpose).
|
|
*
|
|
* Instead, with FACK TCP uses fackets_out that includes both SACKed
|
|
* segments up to the highest received SACK block so far and holes in
|
|
* between them.
|
|
*
|
|
* With reordering, holes may still be in flight, so RFC3517 recovery
|
|
* uses pure sacked_out (total number of SACKed segments) even though
|
|
* it violates the RFC that uses duplicate ACKs, often these are equal
|
|
* but when e.g. out-of-window ACKs or packet duplication occurs,
|
|
* they differ. Since neither occurs due to loss, TCP should really
|
|
* ignore them.
|
|
*/
|
|
static inline int tcp_dupack_heuristics(const struct tcp_sock *tp)
|
|
{
|
|
return tcp_is_fack(tp) ? tp->fackets_out : tp->sacked_out + 1;
|
|
}
|
|
|
|
static bool tcp_pause_early_retransmit(struct sock *sk, int flag)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
unsigned long delay;
|
|
|
|
/* Delay early retransmit and entering fast recovery for
|
|
* max(RTT/4, 2msec) unless ack has ECE mark, no RTT samples
|
|
* available, or RTO is scheduled to fire first.
|
|
*/
|
|
if (sysctl_tcp_early_retrans < 2 || sysctl_tcp_early_retrans > 3 ||
|
|
(flag & FLAG_ECE) || !tp->srtt_us)
|
|
return false;
|
|
|
|
delay = max(usecs_to_jiffies(tp->srtt_us >> 5),
|
|
msecs_to_jiffies(2));
|
|
|
|
if (!time_after(inet_csk(sk)->icsk_timeout, (jiffies + delay)))
|
|
return false;
|
|
|
|
inet_csk_reset_xmit_timer(sk, ICSK_TIME_EARLY_RETRANS, delay,
|
|
TCP_RTO_MAX);
|
|
return true;
|
|
}
|
|
|
|
/* Linux NewReno/SACK/FACK/ECN state machine.
|
|
* --------------------------------------
|
|
*
|
|
* "Open" Normal state, no dubious events, fast path.
|
|
* "Disorder" In all the respects it is "Open",
|
|
* but requires a bit more attention. It is entered when
|
|
* we see some SACKs or dupacks. It is split of "Open"
|
|
* mainly to move some processing from fast path to slow one.
|
|
* "CWR" CWND was reduced due to some Congestion Notification event.
|
|
* It can be ECN, ICMP source quench, local device congestion.
|
|
* "Recovery" CWND was reduced, we are fast-retransmitting.
|
|
* "Loss" CWND was reduced due to RTO timeout or SACK reneging.
|
|
*
|
|
* tcp_fastretrans_alert() is entered:
|
|
* - each incoming ACK, if state is not "Open"
|
|
* - when arrived ACK is unusual, namely:
|
|
* * SACK
|
|
* * Duplicate ACK.
|
|
* * ECN ECE.
|
|
*
|
|
* Counting packets in flight is pretty simple.
|
|
*
|
|
* in_flight = packets_out - left_out + retrans_out
|
|
*
|
|
* packets_out is SND.NXT-SND.UNA counted in packets.
|
|
*
|
|
* retrans_out is number of retransmitted segments.
|
|
*
|
|
* left_out is number of segments left network, but not ACKed yet.
|
|
*
|
|
* left_out = sacked_out + lost_out
|
|
*
|
|
* sacked_out: Packets, which arrived to receiver out of order
|
|
* and hence not ACKed. With SACKs this number is simply
|
|
* amount of SACKed data. Even without SACKs
|
|
* it is easy to give pretty reliable estimate of this number,
|
|
* counting duplicate ACKs.
|
|
*
|
|
* lost_out: Packets lost by network. TCP has no explicit
|
|
* "loss notification" feedback from network (for now).
|
|
* It means that this number can be only _guessed_.
|
|
* Actually, it is the heuristics to predict lossage that
|
|
* distinguishes different algorithms.
|
|
*
|
|
* F.e. after RTO, when all the queue is considered as lost,
|
|
* lost_out = packets_out and in_flight = retrans_out.
|
|
*
|
|
* Essentially, we have now two algorithms counting
|
|
* lost packets.
|
|
*
|
|
* FACK: It is the simplest heuristics. As soon as we decided
|
|
* that something is lost, we decide that _all_ not SACKed
|
|
* packets until the most forward SACK are lost. I.e.
|
|
* lost_out = fackets_out - sacked_out and left_out = fackets_out.
|
|
* It is absolutely correct estimate, if network does not reorder
|
|
* packets. And it loses any connection to reality when reordering
|
|
* takes place. We use FACK by default until reordering
|
|
* is suspected on the path to this destination.
|
|
*
|
|
* NewReno: when Recovery is entered, we assume that one segment
|
|
* is lost (classic Reno). While we are in Recovery and
|
|
* a partial ACK arrives, we assume that one more packet
|
|
* is lost (NewReno). This heuristics are the same in NewReno
|
|
* and SACK.
|
|
*
|
|
* Imagine, that's all! Forget about all this shamanism about CWND inflation
|
|
* deflation etc. CWND is real congestion window, never inflated, changes
|
|
* only according to classic VJ rules.
|
|
*
|
|
* Really tricky (and requiring careful tuning) part of algorithm
|
|
* is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
|
|
* The first determines the moment _when_ we should reduce CWND and,
|
|
* hence, slow down forward transmission. In fact, it determines the moment
|
|
* when we decide that hole is caused by loss, rather than by a reorder.
|
|
*
|
|
* tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
|
|
* holes, caused by lost packets.
|
|
*
|
|
* And the most logically complicated part of algorithm is undo
|
|
* heuristics. We detect false retransmits due to both too early
|
|
* fast retransmit (reordering) and underestimated RTO, analyzing
|
|
* timestamps and D-SACKs. When we detect that some segments were
|
|
* retransmitted by mistake and CWND reduction was wrong, we undo
|
|
* window reduction and abort recovery phase. This logic is hidden
|
|
* inside several functions named tcp_try_undo_<something>.
|
|
*/
|
|
|
|
/* This function decides, when we should leave Disordered state
|
|
* and enter Recovery phase, reducing congestion window.
|
|
*
|
|
* Main question: may we further continue forward transmission
|
|
* with the same cwnd?
|
|
*/
|
|
static bool tcp_time_to_recover(struct sock *sk, int flag)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
__u32 packets_out;
|
|
|
|
/* Trick#1: The loss is proven. */
|
|
if (tp->lost_out)
|
|
return true;
|
|
|
|
/* Not-A-Trick#2 : Classic rule... */
|
|
if (tcp_dupack_heuristics(tp) > tp->reordering)
|
|
return true;
|
|
|
|
/* Trick#4: It is still not OK... But will it be useful to delay
|
|
* recovery more?
|
|
*/
|
|
packets_out = tp->packets_out;
|
|
if (packets_out <= tp->reordering &&
|
|
tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) &&
|
|
!tcp_may_send_now(sk)) {
|
|
/* We have nothing to send. This connection is limited
|
|
* either by receiver window or by application.
|
|
*/
|
|
return true;
|
|
}
|
|
|
|
/* If a thin stream is detected, retransmit after first
|
|
* received dupack. Employ only if SACK is supported in order
|
|
* to avoid possible corner-case series of spurious retransmissions
|
|
* Use only if there are no unsent data.
|
|
*/
|
|
if ((tp->thin_dupack || sysctl_tcp_thin_dupack) &&
|
|
tcp_stream_is_thin(tp) && tcp_dupack_heuristics(tp) > 1 &&
|
|
tcp_is_sack(tp) && !tcp_send_head(sk))
|
|
return true;
|
|
|
|
/* Trick#6: TCP early retransmit, per RFC5827. To avoid spurious
|
|
* retransmissions due to small network reorderings, we implement
|
|
* Mitigation A.3 in the RFC and delay the retransmission for a short
|
|
* interval if appropriate.
|
|
*/
|
|
if (tp->do_early_retrans && !tp->retrans_out && tp->sacked_out &&
|
|
(tp->packets_out >= (tp->sacked_out + 1) && tp->packets_out < 4) &&
|
|
!tcp_may_send_now(sk))
|
|
return !tcp_pause_early_retransmit(sk, flag);
|
|
|
|
return false;
|
|
}
|
|
|
|
/* Detect loss in event "A" above by marking head of queue up as lost.
|
|
* For FACK or non-SACK(Reno) senders, the first "packets" number of segments
|
|
* are considered lost. For RFC3517 SACK, a segment is considered lost if it
|
|
* has at least tp->reordering SACKed seqments above it; "packets" refers to
|
|
* the maximum SACKed segments to pass before reaching this limit.
|
|
*/
|
|
static void tcp_mark_head_lost(struct sock *sk, int packets, int mark_head)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct sk_buff *skb;
|
|
int cnt, oldcnt;
|
|
int err;
|
|
unsigned int mss;
|
|
/* Use SACK to deduce losses of new sequences sent during recovery */
|
|
const u32 loss_high = tcp_is_sack(tp) ? tp->snd_nxt : tp->high_seq;
|
|
|
|
WARN_ON(packets > tp->packets_out);
|
|
if (tp->lost_skb_hint) {
|
|
skb = tp->lost_skb_hint;
|
|
cnt = tp->lost_cnt_hint;
|
|
/* Head already handled? */
|
|
if (mark_head && skb != tcp_write_queue_head(sk))
|
|
return;
|
|
} else {
|
|
skb = tcp_write_queue_head(sk);
|
|
cnt = 0;
|
|
}
|
|
|
|
tcp_for_write_queue_from(skb, sk) {
|
|
if (skb == tcp_send_head(sk))
|
|
break;
|
|
/* TODO: do this better */
|
|
/* this is not the most efficient way to do this... */
|
|
tp->lost_skb_hint = skb;
|
|
tp->lost_cnt_hint = cnt;
|
|
|
|
if (after(TCP_SKB_CB(skb)->end_seq, loss_high))
|
|
break;
|
|
|
|
oldcnt = cnt;
|
|
if (tcp_is_fack(tp) || tcp_is_reno(tp) ||
|
|
(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
|
|
cnt += tcp_skb_pcount(skb);
|
|
|
|
if (cnt > packets) {
|
|
if ((tcp_is_sack(tp) && !tcp_is_fack(tp)) ||
|
|
(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) ||
|
|
(oldcnt >= packets))
|
|
break;
|
|
|
|
mss = tcp_skb_mss(skb);
|
|
err = tcp_fragment(sk, skb, (packets - oldcnt) * mss,
|
|
mss, GFP_ATOMIC);
|
|
if (err < 0)
|
|
break;
|
|
cnt = packets;
|
|
}
|
|
|
|
tcp_skb_mark_lost(tp, skb);
|
|
|
|
if (mark_head)
|
|
break;
|
|
}
|
|
tcp_verify_left_out(tp);
|
|
}
|
|
|
|
/* Account newly detected lost packet(s) */
|
|
|
|
static void tcp_update_scoreboard(struct sock *sk, int fast_rexmit)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
if (tcp_is_reno(tp)) {
|
|
tcp_mark_head_lost(sk, 1, 1);
|
|
} else if (tcp_is_fack(tp)) {
|
|
int lost = tp->fackets_out - tp->reordering;
|
|
if (lost <= 0)
|
|
lost = 1;
|
|
tcp_mark_head_lost(sk, lost, 0);
|
|
} else {
|
|
int sacked_upto = tp->sacked_out - tp->reordering;
|
|
if (sacked_upto >= 0)
|
|
tcp_mark_head_lost(sk, sacked_upto, 0);
|
|
else if (fast_rexmit)
|
|
tcp_mark_head_lost(sk, 1, 1);
|
|
}
|
|
}
|
|
|
|
/* CWND moderation, preventing bursts due to too big ACKs
|
|
* in dubious situations.
|
|
*/
|
|
static inline void tcp_moderate_cwnd(struct tcp_sock *tp)
|
|
{
|
|
tp->snd_cwnd = min(tp->snd_cwnd,
|
|
tcp_packets_in_flight(tp) + tcp_max_burst(tp));
|
|
tp->snd_cwnd_stamp = tcp_time_stamp;
|
|
}
|
|
|
|
/* Nothing was retransmitted or returned timestamp is less
|
|
* than timestamp of the first retransmission.
|
|
*/
|
|
static inline bool tcp_packet_delayed(const struct tcp_sock *tp)
|
|
{
|
|
return !tp->retrans_stamp ||
|
|
(tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
|
|
before(tp->rx_opt.rcv_tsecr, tp->retrans_stamp));
|
|
}
|
|
|
|
/* Undo procedures. */
|
|
|
|
/* We can clear retrans_stamp when there are no retransmissions in the
|
|
* window. It would seem that it is trivially available for us in
|
|
* tp->retrans_out, however, that kind of assumptions doesn't consider
|
|
* what will happen if errors occur when sending retransmission for the
|
|
* second time. ...It could the that such segment has only
|
|
* TCPCB_EVER_RETRANS set at the present time. It seems that checking
|
|
* the head skb is enough except for some reneging corner cases that
|
|
* are not worth the effort.
|
|
*
|
|
* Main reason for all this complexity is the fact that connection dying
|
|
* time now depends on the validity of the retrans_stamp, in particular,
|
|
* that successive retransmissions of a segment must not advance
|
|
* retrans_stamp under any conditions.
|
|
*/
|
|
static bool tcp_any_retrans_done(const struct sock *sk)
|
|
{
|
|
const struct tcp_sock *tp = tcp_sk(sk);
|
|
struct sk_buff *skb;
|
|
|
|
if (tp->retrans_out)
|
|
return true;
|
|
|
|
skb = tcp_write_queue_head(sk);
|
|
if (unlikely(skb && TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS))
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
#if FASTRETRANS_DEBUG > 1
|
|
static void DBGUNDO(struct sock *sk, const char *msg)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct inet_sock *inet = inet_sk(sk);
|
|
|
|
if (sk->sk_family == AF_INET) {
|
|
pr_debug("Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n",
|
|
msg,
|
|
&inet->inet_daddr, ntohs(inet->inet_dport),
|
|
tp->snd_cwnd, tcp_left_out(tp),
|
|
tp->snd_ssthresh, tp->prior_ssthresh,
|
|
tp->packets_out);
|
|
}
|
|
#if IS_ENABLED(CONFIG_IPV6)
|
|
else if (sk->sk_family == AF_INET6) {
|
|
struct ipv6_pinfo *np = inet6_sk(sk);
|
|
pr_debug("Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n",
|
|
msg,
|
|
&np->daddr, ntohs(inet->inet_dport),
|
|
tp->snd_cwnd, tcp_left_out(tp),
|
|
tp->snd_ssthresh, tp->prior_ssthresh,
|
|
tp->packets_out);
|
|
}
|
|
#endif
|
|
}
|
|
#else
|
|
#define DBGUNDO(x...) do { } while (0)
|
|
#endif
|
|
|
|
static void tcp_undo_cwnd_reduction(struct sock *sk, bool unmark_loss)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
if (unmark_loss) {
|
|
struct sk_buff *skb;
|
|
|
|
tcp_for_write_queue(skb, sk) {
|
|
if (skb == tcp_send_head(sk))
|
|
break;
|
|
TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
|
|
}
|
|
tp->lost_out = 0;
|
|
tcp_clear_all_retrans_hints(tp);
|
|
}
|
|
|
|
if (tp->prior_ssthresh) {
|
|
const struct inet_connection_sock *icsk = inet_csk(sk);
|
|
|
|
if (icsk->icsk_ca_ops->undo_cwnd)
|
|
tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk);
|
|
else
|
|
tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh << 1);
|
|
|
|
if (tp->prior_ssthresh > tp->snd_ssthresh) {
|
|
tp->snd_ssthresh = tp->prior_ssthresh;
|
|
tcp_ecn_withdraw_cwr(tp);
|
|
}
|
|
} else {
|
|
tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh);
|
|
}
|
|
tp->snd_cwnd_stamp = tcp_time_stamp;
|
|
tp->undo_marker = 0;
|
|
}
|
|
|
|
static inline bool tcp_may_undo(const struct tcp_sock *tp)
|
|
{
|
|
return tp->undo_marker && (!tp->undo_retrans || tcp_packet_delayed(tp));
|
|
}
|
|
|
|
/* People celebrate: "We love our President!" */
|
|
static bool tcp_try_undo_recovery(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
if (tcp_may_undo(tp)) {
|
|
int mib_idx;
|
|
|
|
/* Happy end! We did not retransmit anything
|
|
* or our original transmission succeeded.
|
|
*/
|
|
DBGUNDO(sk, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans");
|
|
tcp_undo_cwnd_reduction(sk, false);
|
|
if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss)
|
|
mib_idx = LINUX_MIB_TCPLOSSUNDO;
|
|
else
|
|
mib_idx = LINUX_MIB_TCPFULLUNDO;
|
|
|
|
NET_INC_STATS_BH(sock_net(sk), mib_idx);
|
|
}
|
|
if (tp->snd_una == tp->high_seq && tcp_is_reno(tp)) {
|
|
/* Hold old state until something *above* high_seq
|
|
* is ACKed. For Reno it is MUST to prevent false
|
|
* fast retransmits (RFC2582). SACK TCP is safe. */
|
|
tcp_moderate_cwnd(tp);
|
|
if (!tcp_any_retrans_done(sk))
|
|
tp->retrans_stamp = 0;
|
|
return true;
|
|
}
|
|
tcp_set_ca_state(sk, TCP_CA_Open);
|
|
return false;
|
|
}
|
|
|
|
/* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
|
|
static bool tcp_try_undo_dsack(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
if (tp->undo_marker && !tp->undo_retrans) {
|
|
DBGUNDO(sk, "D-SACK");
|
|
tcp_undo_cwnd_reduction(sk, false);
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDSACKUNDO);
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/* Undo during loss recovery after partial ACK or using F-RTO. */
|
|
static bool tcp_try_undo_loss(struct sock *sk, bool frto_undo)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
if (frto_undo || tcp_may_undo(tp)) {
|
|
tcp_undo_cwnd_reduction(sk, true);
|
|
|
|
DBGUNDO(sk, "partial loss");
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSSUNDO);
|
|
if (frto_undo)
|
|
NET_INC_STATS_BH(sock_net(sk),
|
|
LINUX_MIB_TCPSPURIOUSRTOS);
|
|
inet_csk(sk)->icsk_retransmits = 0;
|
|
if (frto_undo || tcp_is_sack(tp))
|
|
tcp_set_ca_state(sk, TCP_CA_Open);
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/* The cwnd reduction in CWR and Recovery uses the PRR algorithm in RFC 6937.
|
|
* It computes the number of packets to send (sndcnt) based on packets newly
|
|
* delivered:
|
|
* 1) If the packets in flight is larger than ssthresh, PRR spreads the
|
|
* cwnd reductions across a full RTT.
|
|
* 2) Otherwise PRR uses packet conservation to send as much as delivered.
|
|
* But when the retransmits are acked without further losses, PRR
|
|
* slow starts cwnd up to ssthresh to speed up the recovery.
|
|
*/
|
|
static void tcp_init_cwnd_reduction(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
tp->high_seq = tp->snd_nxt;
|
|
tp->tlp_high_seq = 0;
|
|
tp->snd_cwnd_cnt = 0;
|
|
tp->prior_cwnd = tp->snd_cwnd;
|
|
tp->prr_delivered = 0;
|
|
tp->prr_out = 0;
|
|
tp->snd_ssthresh = inet_csk(sk)->icsk_ca_ops->ssthresh(sk);
|
|
tcp_ecn_queue_cwr(tp);
|
|
}
|
|
|
|
static void tcp_cwnd_reduction(struct sock *sk, const int prior_unsacked,
|
|
int fast_rexmit, int flag)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
int sndcnt = 0;
|
|
int delta = tp->snd_ssthresh - tcp_packets_in_flight(tp);
|
|
int newly_acked_sacked = prior_unsacked -
|
|
(tp->packets_out - tp->sacked_out);
|
|
|
|
tp->prr_delivered += newly_acked_sacked;
|
|
if (delta < 0) {
|
|
u64 dividend = (u64)tp->snd_ssthresh * tp->prr_delivered +
|
|
tp->prior_cwnd - 1;
|
|
sndcnt = div_u64(dividend, tp->prior_cwnd) - tp->prr_out;
|
|
} else if ((flag & FLAG_RETRANS_DATA_ACKED) &&
|
|
!(flag & FLAG_LOST_RETRANS)) {
|
|
sndcnt = min_t(int, delta,
|
|
max_t(int, tp->prr_delivered - tp->prr_out,
|
|
newly_acked_sacked) + 1);
|
|
} else {
|
|
sndcnt = min(delta, newly_acked_sacked);
|
|
}
|
|
sndcnt = max(sndcnt, (fast_rexmit ? 1 : 0));
|
|
tp->snd_cwnd = tcp_packets_in_flight(tp) + sndcnt;
|
|
}
|
|
|
|
static inline void tcp_end_cwnd_reduction(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
/* Reset cwnd to ssthresh in CWR or Recovery (unless it's undone) */
|
|
if (inet_csk(sk)->icsk_ca_state == TCP_CA_CWR ||
|
|
(tp->undo_marker && tp->snd_ssthresh < TCP_INFINITE_SSTHRESH)) {
|
|
tp->snd_cwnd = tp->snd_ssthresh;
|
|
tp->snd_cwnd_stamp = tcp_time_stamp;
|
|
}
|
|
tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR);
|
|
}
|
|
|
|
/* Enter CWR state. Disable cwnd undo since congestion is proven with ECN */
|
|
void tcp_enter_cwr(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
tp->prior_ssthresh = 0;
|
|
if (inet_csk(sk)->icsk_ca_state < TCP_CA_CWR) {
|
|
tp->undo_marker = 0;
|
|
tcp_init_cwnd_reduction(sk);
|
|
tcp_set_ca_state(sk, TCP_CA_CWR);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(tcp_enter_cwr);
|
|
|
|
static void tcp_try_keep_open(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
int state = TCP_CA_Open;
|
|
|
|
if (tcp_left_out(tp) || tcp_any_retrans_done(sk))
|
|
state = TCP_CA_Disorder;
|
|
|
|
if (inet_csk(sk)->icsk_ca_state != state) {
|
|
tcp_set_ca_state(sk, state);
|
|
tp->high_seq = tp->snd_nxt;
|
|
}
|
|
}
|
|
|
|
static void tcp_try_to_open(struct sock *sk, int flag, const int prior_unsacked)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
tcp_verify_left_out(tp);
|
|
|
|
if (!tcp_any_retrans_done(sk))
|
|
tp->retrans_stamp = 0;
|
|
|
|
if (flag & FLAG_ECE)
|
|
tcp_enter_cwr(sk);
|
|
|
|
if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) {
|
|
tcp_try_keep_open(sk);
|
|
} else {
|
|
tcp_cwnd_reduction(sk, prior_unsacked, 0, flag);
|
|
}
|
|
}
|
|
|
|
static void tcp_mtup_probe_failed(struct sock *sk)
|
|
{
|
|
struct inet_connection_sock *icsk = inet_csk(sk);
|
|
|
|
icsk->icsk_mtup.search_high = icsk->icsk_mtup.probe_size - 1;
|
|
icsk->icsk_mtup.probe_size = 0;
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPMTUPFAIL);
|
|
}
|
|
|
|
static void tcp_mtup_probe_success(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct inet_connection_sock *icsk = inet_csk(sk);
|
|
|
|
/* FIXME: breaks with very large cwnd */
|
|
tp->prior_ssthresh = tcp_current_ssthresh(sk);
|
|
tp->snd_cwnd = tp->snd_cwnd *
|
|
tcp_mss_to_mtu(sk, tp->mss_cache) /
|
|
icsk->icsk_mtup.probe_size;
|
|
tp->snd_cwnd_cnt = 0;
|
|
tp->snd_cwnd_stamp = tcp_time_stamp;
|
|
tp->snd_ssthresh = tcp_current_ssthresh(sk);
|
|
|
|
icsk->icsk_mtup.search_low = icsk->icsk_mtup.probe_size;
|
|
icsk->icsk_mtup.probe_size = 0;
|
|
tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPMTUPSUCCESS);
|
|
}
|
|
|
|
/* Do a simple retransmit without using the backoff mechanisms in
|
|
* tcp_timer. This is used for path mtu discovery.
|
|
* The socket is already locked here.
|
|
*/
|
|
void tcp_simple_retransmit(struct sock *sk)
|
|
{
|
|
const struct inet_connection_sock *icsk = inet_csk(sk);
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct sk_buff *skb;
|
|
unsigned int mss = tcp_current_mss(sk);
|
|
u32 prior_lost = tp->lost_out;
|
|
|
|
tcp_for_write_queue(skb, sk) {
|
|
if (skb == tcp_send_head(sk))
|
|
break;
|
|
if (tcp_skb_seglen(skb) > mss &&
|
|
!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
|
|
if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
|
|
TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
|
|
tp->retrans_out -= tcp_skb_pcount(skb);
|
|
}
|
|
tcp_skb_mark_lost_uncond_verify(tp, skb);
|
|
}
|
|
}
|
|
|
|
tcp_clear_retrans_hints_partial(tp);
|
|
|
|
if (prior_lost == tp->lost_out)
|
|
return;
|
|
|
|
if (tcp_is_reno(tp))
|
|
tcp_limit_reno_sacked(tp);
|
|
|
|
tcp_verify_left_out(tp);
|
|
|
|
/* Don't muck with the congestion window here.
|
|
* Reason is that we do not increase amount of _data_
|
|
* in network, but units changed and effective
|
|
* cwnd/ssthresh really reduced now.
|
|
*/
|
|
if (icsk->icsk_ca_state != TCP_CA_Loss) {
|
|
tp->high_seq = tp->snd_nxt;
|
|
tp->snd_ssthresh = tcp_current_ssthresh(sk);
|
|
tp->prior_ssthresh = 0;
|
|
tp->undo_marker = 0;
|
|
tcp_set_ca_state(sk, TCP_CA_Loss);
|
|
}
|
|
tcp_xmit_retransmit_queue(sk);
|
|
}
|
|
EXPORT_SYMBOL(tcp_simple_retransmit);
|
|
|
|
static void tcp_enter_recovery(struct sock *sk, bool ece_ack)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
int mib_idx;
|
|
|
|
if (tcp_is_reno(tp))
|
|
mib_idx = LINUX_MIB_TCPRENORECOVERY;
|
|
else
|
|
mib_idx = LINUX_MIB_TCPSACKRECOVERY;
|
|
|
|
NET_INC_STATS_BH(sock_net(sk), mib_idx);
|
|
|
|
tp->prior_ssthresh = 0;
|
|
tcp_init_undo(tp);
|
|
|
|
if (!tcp_in_cwnd_reduction(sk)) {
|
|
if (!ece_ack)
|
|
tp->prior_ssthresh = tcp_current_ssthresh(sk);
|
|
tcp_init_cwnd_reduction(sk);
|
|
}
|
|
tcp_set_ca_state(sk, TCP_CA_Recovery);
|
|
}
|
|
|
|
/* Process an ACK in CA_Loss state. Move to CA_Open if lost data are
|
|
* recovered or spurious. Otherwise retransmits more on partial ACKs.
|
|
*/
|
|
static void tcp_process_loss(struct sock *sk, int flag, bool is_dupack)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
bool recovered = !before(tp->snd_una, tp->high_seq);
|
|
|
|
if ((flag & FLAG_SND_UNA_ADVANCED) &&
|
|
tcp_try_undo_loss(sk, false))
|
|
return;
|
|
|
|
if (tp->frto) { /* F-RTO RFC5682 sec 3.1 (sack enhanced version). */
|
|
/* Step 3.b. A timeout is spurious if not all data are
|
|
* lost, i.e., never-retransmitted data are (s)acked.
|
|
*/
|
|
if ((flag & FLAG_ORIG_SACK_ACKED) &&
|
|
tcp_try_undo_loss(sk, true))
|
|
return;
|
|
|
|
if (after(tp->snd_nxt, tp->high_seq)) {
|
|
if (flag & FLAG_DATA_SACKED || is_dupack)
|
|
tp->frto = 0; /* Step 3.a. loss was real */
|
|
} else if (flag & FLAG_SND_UNA_ADVANCED && !recovered) {
|
|
tp->high_seq = tp->snd_nxt;
|
|
__tcp_push_pending_frames(sk, tcp_current_mss(sk),
|
|
TCP_NAGLE_OFF);
|
|
if (after(tp->snd_nxt, tp->high_seq))
|
|
return; /* Step 2.b */
|
|
tp->frto = 0;
|
|
}
|
|
}
|
|
|
|
if (recovered) {
|
|
/* F-RTO RFC5682 sec 3.1 step 2.a and 1st part of step 3.a */
|
|
tcp_try_undo_recovery(sk);
|
|
return;
|
|
}
|
|
if (tcp_is_reno(tp)) {
|
|
/* A Reno DUPACK means new data in F-RTO step 2.b above are
|
|
* delivered. Lower inflight to clock out (re)tranmissions.
|
|
*/
|
|
if (after(tp->snd_nxt, tp->high_seq) && is_dupack)
|
|
tcp_add_reno_sack(sk);
|
|
else if (flag & FLAG_SND_UNA_ADVANCED)
|
|
tcp_reset_reno_sack(tp);
|
|
}
|
|
tcp_xmit_retransmit_queue(sk);
|
|
}
|
|
|
|
/* Undo during fast recovery after partial ACK. */
|
|
static bool tcp_try_undo_partial(struct sock *sk, const int acked,
|
|
const int prior_unsacked, int flag)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
if (tp->undo_marker && tcp_packet_delayed(tp)) {
|
|
/* Plain luck! Hole if filled with delayed
|
|
* packet, rather than with a retransmit.
|
|
*/
|
|
tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1);
|
|
|
|
/* We are getting evidence that the reordering degree is higher
|
|
* than we realized. If there are no retransmits out then we
|
|
* can undo. Otherwise we clock out new packets but do not
|
|
* mark more packets lost or retransmit more.
|
|
*/
|
|
if (tp->retrans_out) {
|
|
tcp_cwnd_reduction(sk, prior_unsacked, 0, flag);
|
|
return true;
|
|
}
|
|
|
|
if (!tcp_any_retrans_done(sk))
|
|
tp->retrans_stamp = 0;
|
|
|
|
DBGUNDO(sk, "partial recovery");
|
|
tcp_undo_cwnd_reduction(sk, true);
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPPARTIALUNDO);
|
|
tcp_try_keep_open(sk);
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/* Process an event, which can update packets-in-flight not trivially.
|
|
* Main goal of this function is to calculate new estimate for left_out,
|
|
* taking into account both packets sitting in receiver's buffer and
|
|
* packets lost by network.
|
|
*
|
|
* Besides that it does CWND reduction, when packet loss is detected
|
|
* and changes state of machine.
|
|
*
|
|
* It does _not_ decide what to send, it is made in function
|
|
* tcp_xmit_retransmit_queue().
|
|
*/
|
|
static void tcp_fastretrans_alert(struct sock *sk, const int acked,
|
|
const int prior_unsacked,
|
|
bool is_dupack, int flag)
|
|
{
|
|
struct inet_connection_sock *icsk = inet_csk(sk);
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
bool do_lost = is_dupack || ((flag & FLAG_DATA_SACKED) &&
|
|
(tcp_fackets_out(tp) > tp->reordering));
|
|
int fast_rexmit = 0;
|
|
|
|
if (WARN_ON(!tp->packets_out && tp->sacked_out))
|
|
tp->sacked_out = 0;
|
|
if (WARN_ON(!tp->sacked_out && tp->fackets_out))
|
|
tp->fackets_out = 0;
|
|
|
|
/* Now state machine starts.
|
|
* A. ECE, hence prohibit cwnd undoing, the reduction is required. */
|
|
if (flag & FLAG_ECE)
|
|
tp->prior_ssthresh = 0;
|
|
|
|
/* B. In all the states check for reneging SACKs. */
|
|
if (tcp_check_sack_reneging(sk, flag))
|
|
return;
|
|
|
|
/* C. Check consistency of the current state. */
|
|
tcp_verify_left_out(tp);
|
|
|
|
/* D. Check state exit conditions. State can be terminated
|
|
* when high_seq is ACKed. */
|
|
if (icsk->icsk_ca_state == TCP_CA_Open) {
|
|
WARN_ON(tp->retrans_out != 0);
|
|
tp->retrans_stamp = 0;
|
|
} else if (!before(tp->snd_una, tp->high_seq)) {
|
|
switch (icsk->icsk_ca_state) {
|
|
case TCP_CA_CWR:
|
|
/* CWR is to be held something *above* high_seq
|
|
* is ACKed for CWR bit to reach receiver. */
|
|
if (tp->snd_una != tp->high_seq) {
|
|
tcp_end_cwnd_reduction(sk);
|
|
tcp_set_ca_state(sk, TCP_CA_Open);
|
|
}
|
|
break;
|
|
|
|
case TCP_CA_Recovery:
|
|
if (tcp_is_reno(tp))
|
|
tcp_reset_reno_sack(tp);
|
|
if (tcp_try_undo_recovery(sk))
|
|
return;
|
|
tcp_end_cwnd_reduction(sk);
|
|
break;
|
|
}
|
|
}
|
|
|
|
/* E. Process state. */
|
|
switch (icsk->icsk_ca_state) {
|
|
case TCP_CA_Recovery:
|
|
if (!(flag & FLAG_SND_UNA_ADVANCED)) {
|
|
if (tcp_is_reno(tp) && is_dupack)
|
|
tcp_add_reno_sack(sk);
|
|
} else {
|
|
if (tcp_try_undo_partial(sk, acked, prior_unsacked, flag))
|
|
return;
|
|
/* Partial ACK arrived. Force fast retransmit. */
|
|
do_lost = tcp_is_reno(tp) ||
|
|
tcp_fackets_out(tp) > tp->reordering;
|
|
}
|
|
if (tcp_try_undo_dsack(sk)) {
|
|
tcp_try_keep_open(sk);
|
|
return;
|
|
}
|
|
break;
|
|
case TCP_CA_Loss:
|
|
tcp_process_loss(sk, flag, is_dupack);
|
|
if (icsk->icsk_ca_state != TCP_CA_Open &&
|
|
!(flag & FLAG_LOST_RETRANS))
|
|
return;
|
|
/* Change state if cwnd is undone or retransmits are lost */
|
|
default:
|
|
if (tcp_is_reno(tp)) {
|
|
if (flag & FLAG_SND_UNA_ADVANCED)
|
|
tcp_reset_reno_sack(tp);
|
|
if (is_dupack)
|
|
tcp_add_reno_sack(sk);
|
|
}
|
|
|
|
if (icsk->icsk_ca_state <= TCP_CA_Disorder)
|
|
tcp_try_undo_dsack(sk);
|
|
|
|
if (!tcp_time_to_recover(sk, flag)) {
|
|
tcp_try_to_open(sk, flag, prior_unsacked);
|
|
return;
|
|
}
|
|
|
|
/* MTU probe failure: don't reduce cwnd */
|
|
if (icsk->icsk_ca_state < TCP_CA_CWR &&
|
|
icsk->icsk_mtup.probe_size &&
|
|
tp->snd_una == tp->mtu_probe.probe_seq_start) {
|
|
tcp_mtup_probe_failed(sk);
|
|
/* Restores the reduction we did in tcp_mtup_probe() */
|
|
tp->snd_cwnd++;
|
|
tcp_simple_retransmit(sk);
|
|
return;
|
|
}
|
|
|
|
/* Otherwise enter Recovery state */
|
|
tcp_enter_recovery(sk, (flag & FLAG_ECE));
|
|
fast_rexmit = 1;
|
|
}
|
|
|
|
if (do_lost)
|
|
tcp_update_scoreboard(sk, fast_rexmit);
|
|
tcp_cwnd_reduction(sk, prior_unsacked, fast_rexmit, flag);
|
|
tcp_xmit_retransmit_queue(sk);
|
|
}
|
|
|
|
static inline bool tcp_ack_update_rtt(struct sock *sk, const int flag,
|
|
long seq_rtt_us, long sack_rtt_us)
|
|
{
|
|
const struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
/* Prefer RTT measured from ACK's timing to TS-ECR. This is because
|
|
* broken middle-boxes or peers may corrupt TS-ECR fields. But
|
|
* Karn's algorithm forbids taking RTT if some retransmitted data
|
|
* is acked (RFC6298).
|
|
*/
|
|
if (flag & FLAG_RETRANS_DATA_ACKED)
|
|
seq_rtt_us = -1L;
|
|
|
|
if (seq_rtt_us < 0)
|
|
seq_rtt_us = sack_rtt_us;
|
|
|
|
/* RTTM Rule: A TSecr value received in a segment is used to
|
|
* update the averaged RTT measurement only if the segment
|
|
* acknowledges some new data, i.e., only if it advances the
|
|
* left edge of the send window.
|
|
* See draft-ietf-tcplw-high-performance-00, section 3.3.
|
|
*/
|
|
if (seq_rtt_us < 0 && tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
|
|
flag & FLAG_ACKED)
|
|
seq_rtt_us = jiffies_to_usecs(tcp_time_stamp - tp->rx_opt.rcv_tsecr);
|
|
|
|
if (seq_rtt_us < 0)
|
|
return false;
|
|
|
|
tcp_rtt_estimator(sk, seq_rtt_us);
|
|
tcp_set_rto(sk);
|
|
|
|
/* RFC6298: only reset backoff on valid RTT measurement. */
|
|
inet_csk(sk)->icsk_backoff = 0;
|
|
return true;
|
|
}
|
|
|
|
/* Compute time elapsed between (last) SYNACK and the ACK completing 3WHS. */
|
|
static void tcp_synack_rtt_meas(struct sock *sk, const u32 synack_stamp)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
long seq_rtt_us = -1L;
|
|
|
|
if (synack_stamp && !tp->total_retrans)
|
|
seq_rtt_us = jiffies_to_usecs(tcp_time_stamp - synack_stamp);
|
|
|
|
/* If the ACK acks both the SYNACK and the (Fast Open'd) data packets
|
|
* sent in SYN_RECV, SYNACK RTT is the smooth RTT computed in tcp_ack()
|
|
*/
|
|
if (!tp->srtt_us)
|
|
tcp_ack_update_rtt(sk, FLAG_SYN_ACKED, seq_rtt_us, -1L);
|
|
}
|
|
|
|
static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 acked)
|
|
{
|
|
const struct inet_connection_sock *icsk = inet_csk(sk);
|
|
|
|
icsk->icsk_ca_ops->cong_avoid(sk, ack, acked);
|
|
tcp_sk(sk)->snd_cwnd_stamp = tcp_time_stamp;
|
|
}
|
|
|
|
/* Restart timer after forward progress on connection.
|
|
* RFC2988 recommends to restart timer to now+rto.
|
|
*/
|
|
void tcp_rearm_rto(struct sock *sk)
|
|
{
|
|
const struct inet_connection_sock *icsk = inet_csk(sk);
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
/* If the retrans timer is currently being used by Fast Open
|
|
* for SYN-ACK retrans purpose, stay put.
|
|
*/
|
|
if (tp->fastopen_rsk)
|
|
return;
|
|
|
|
if (!tp->packets_out) {
|
|
inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
|
|
} else {
|
|
u32 rto = inet_csk(sk)->icsk_rto;
|
|
/* Offset the time elapsed after installing regular RTO */
|
|
if (icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS ||
|
|
icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) {
|
|
struct sk_buff *skb = tcp_write_queue_head(sk);
|
|
const u32 rto_time_stamp =
|
|
tcp_skb_timestamp(skb) + rto;
|
|
s32 delta = (s32)(rto_time_stamp - tcp_time_stamp);
|
|
/* delta may not be positive if the socket is locked
|
|
* when the retrans timer fires and is rescheduled.
|
|
*/
|
|
if (delta > 0)
|
|
rto = delta;
|
|
}
|
|
inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, rto,
|
|
TCP_RTO_MAX);
|
|
}
|
|
}
|
|
|
|
/* This function is called when the delayed ER timer fires. TCP enters
|
|
* fast recovery and performs fast-retransmit.
|
|
*/
|
|
void tcp_resume_early_retransmit(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
tcp_rearm_rto(sk);
|
|
|
|
/* Stop if ER is disabled after the delayed ER timer is scheduled */
|
|
if (!tp->do_early_retrans)
|
|
return;
|
|
|
|
tcp_enter_recovery(sk, false);
|
|
tcp_update_scoreboard(sk, 1);
|
|
tcp_xmit_retransmit_queue(sk);
|
|
}
|
|
|
|
/* If we get here, the whole TSO packet has not been acked. */
|
|
static u32 tcp_tso_acked(struct sock *sk, struct sk_buff *skb)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
u32 packets_acked;
|
|
|
|
BUG_ON(!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una));
|
|
|
|
packets_acked = tcp_skb_pcount(skb);
|
|
if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
|
|
return 0;
|
|
packets_acked -= tcp_skb_pcount(skb);
|
|
|
|
if (packets_acked) {
|
|
BUG_ON(tcp_skb_pcount(skb) == 0);
|
|
BUG_ON(!before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq));
|
|
}
|
|
|
|
return packets_acked;
|
|
}
|
|
|
|
static void tcp_ack_tstamp(struct sock *sk, struct sk_buff *skb,
|
|
u32 prior_snd_una)
|
|
{
|
|
const struct skb_shared_info *shinfo;
|
|
|
|
/* Avoid cache line misses to get skb_shinfo() and shinfo->tx_flags */
|
|
if (likely(!(sk->sk_tsflags & SOF_TIMESTAMPING_TX_ACK)))
|
|
return;
|
|
|
|
shinfo = skb_shinfo(skb);
|
|
if ((shinfo->tx_flags & SKBTX_ACK_TSTAMP) &&
|
|
between(shinfo->tskey, prior_snd_una, tcp_sk(sk)->snd_una - 1))
|
|
__skb_tstamp_tx(skb, NULL, sk, SCM_TSTAMP_ACK);
|
|
}
|
|
|
|
/* Remove acknowledged frames from the retransmission queue. If our packet
|
|
* is before the ack sequence we can discard it as it's confirmed to have
|
|
* arrived at the other end.
|
|
*/
|
|
static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
|
|
u32 prior_snd_una,
|
|
struct tcp_sacktag_state *sack)
|
|
{
|
|
const struct inet_connection_sock *icsk = inet_csk(sk);
|
|
struct skb_mstamp first_ackt, last_ackt, now;
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
u32 prior_sacked = tp->sacked_out;
|
|
u32 reord = tp->packets_out;
|
|
bool fully_acked = true;
|
|
long sack_rtt_us = -1L;
|
|
long seq_rtt_us = -1L;
|
|
long ca_rtt_us = -1L;
|
|
struct sk_buff *skb;
|
|
u32 pkts_acked = 0;
|
|
bool rtt_update;
|
|
int flag = 0;
|
|
|
|
first_ackt.v64 = 0;
|
|
|
|
while ((skb = tcp_write_queue_head(sk)) && skb != tcp_send_head(sk)) {
|
|
struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
|
|
u8 sacked = scb->sacked;
|
|
u32 acked_pcount;
|
|
|
|
tcp_ack_tstamp(sk, skb, prior_snd_una);
|
|
|
|
/* Determine how many packets and what bytes were acked, tso and else */
|
|
if (after(scb->end_seq, tp->snd_una)) {
|
|
if (tcp_skb_pcount(skb) == 1 ||
|
|
!after(tp->snd_una, scb->seq))
|
|
break;
|
|
|
|
acked_pcount = tcp_tso_acked(sk, skb);
|
|
if (!acked_pcount)
|
|
break;
|
|
|
|
fully_acked = false;
|
|
} else {
|
|
/* Speedup tcp_unlink_write_queue() and next loop */
|
|
prefetchw(skb->next);
|
|
acked_pcount = tcp_skb_pcount(skb);
|
|
}
|
|
|
|
if (unlikely(sacked & TCPCB_RETRANS)) {
|
|
if (sacked & TCPCB_SACKED_RETRANS)
|
|
tp->retrans_out -= acked_pcount;
|
|
flag |= FLAG_RETRANS_DATA_ACKED;
|
|
} else if (!(sacked & TCPCB_SACKED_ACKED)) {
|
|
last_ackt = skb->skb_mstamp;
|
|
WARN_ON_ONCE(last_ackt.v64 == 0);
|
|
if (!first_ackt.v64)
|
|
first_ackt = last_ackt;
|
|
|
|
reord = min(pkts_acked, reord);
|
|
if (!after(scb->end_seq, tp->high_seq))
|
|
flag |= FLAG_ORIG_SACK_ACKED;
|
|
}
|
|
|
|
if (sacked & TCPCB_SACKED_ACKED)
|
|
tp->sacked_out -= acked_pcount;
|
|
if (sacked & TCPCB_LOST)
|
|
tp->lost_out -= acked_pcount;
|
|
|
|
tp->packets_out -= acked_pcount;
|
|
pkts_acked += acked_pcount;
|
|
|
|
/* Initial outgoing SYN's get put onto the write_queue
|
|
* just like anything else we transmit. It is not
|
|
* true data, and if we misinform our callers that
|
|
* this ACK acks real data, we will erroneously exit
|
|
* connection startup slow start one packet too
|
|
* quickly. This is severely frowned upon behavior.
|
|
*/
|
|
if (likely(!(scb->tcp_flags & TCPHDR_SYN))) {
|
|
flag |= FLAG_DATA_ACKED;
|
|
} else {
|
|
flag |= FLAG_SYN_ACKED;
|
|
tp->retrans_stamp = 0;
|
|
}
|
|
|
|
if (!fully_acked)
|
|
break;
|
|
|
|
tcp_unlink_write_queue(skb, sk);
|
|
sk_wmem_free_skb(sk, skb);
|
|
if (unlikely(skb == tp->retransmit_skb_hint))
|
|
tp->retransmit_skb_hint = NULL;
|
|
if (unlikely(skb == tp->lost_skb_hint))
|
|
tp->lost_skb_hint = NULL;
|
|
}
|
|
|
|
if (likely(between(tp->snd_up, prior_snd_una, tp->snd_una)))
|
|
tp->snd_up = tp->snd_una;
|
|
|
|
if (skb && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
|
|
flag |= FLAG_SACK_RENEGING;
|
|
|
|
skb_mstamp_get(&now);
|
|
if (likely(first_ackt.v64)) {
|
|
seq_rtt_us = skb_mstamp_us_delta(&now, &first_ackt);
|
|
ca_rtt_us = skb_mstamp_us_delta(&now, &last_ackt);
|
|
}
|
|
if (sack->first_sackt.v64) {
|
|
sack_rtt_us = skb_mstamp_us_delta(&now, &sack->first_sackt);
|
|
ca_rtt_us = skb_mstamp_us_delta(&now, &sack->last_sackt);
|
|
}
|
|
|
|
rtt_update = tcp_ack_update_rtt(sk, flag, seq_rtt_us, sack_rtt_us);
|
|
|
|
if (flag & FLAG_ACKED) {
|
|
tcp_rearm_rto(sk);
|
|
if (unlikely(icsk->icsk_mtup.probe_size &&
|
|
!after(tp->mtu_probe.probe_seq_end, tp->snd_una))) {
|
|
tcp_mtup_probe_success(sk);
|
|
}
|
|
|
|
if (tcp_is_reno(tp)) {
|
|
tcp_remove_reno_sacks(sk, pkts_acked);
|
|
} else {
|
|
int delta;
|
|
|
|
/* Non-retransmitted hole got filled? That's reordering */
|
|
if (reord < prior_fackets)
|
|
tcp_update_reordering(sk, tp->fackets_out - reord, 0);
|
|
|
|
delta = tcp_is_fack(tp) ? pkts_acked :
|
|
prior_sacked - tp->sacked_out;
|
|
tp->lost_cnt_hint -= min(tp->lost_cnt_hint, delta);
|
|
}
|
|
|
|
tp->fackets_out -= min(pkts_acked, tp->fackets_out);
|
|
|
|
} else if (skb && rtt_update && sack_rtt_us >= 0 &&
|
|
sack_rtt_us > skb_mstamp_us_delta(&now, &skb->skb_mstamp)) {
|
|
/* Do not re-arm RTO if the sack RTT is measured from data sent
|
|
* after when the head was last (re)transmitted. Otherwise the
|
|
* timeout may continue to extend in loss recovery.
|
|
*/
|
|
tcp_rearm_rto(sk);
|
|
}
|
|
|
|
if (icsk->icsk_ca_ops->pkts_acked)
|
|
icsk->icsk_ca_ops->pkts_acked(sk, pkts_acked, ca_rtt_us);
|
|
|
|
#if FASTRETRANS_DEBUG > 0
|
|
WARN_ON((int)tp->sacked_out < 0);
|
|
WARN_ON((int)tp->lost_out < 0);
|
|
WARN_ON((int)tp->retrans_out < 0);
|
|
if (!tp->packets_out && tcp_is_sack(tp)) {
|
|
icsk = inet_csk(sk);
|
|
if (tp->lost_out) {
|
|
pr_debug("Leak l=%u %d\n",
|
|
tp->lost_out, icsk->icsk_ca_state);
|
|
tp->lost_out = 0;
|
|
}
|
|
if (tp->sacked_out) {
|
|
pr_debug("Leak s=%u %d\n",
|
|
tp->sacked_out, icsk->icsk_ca_state);
|
|
tp->sacked_out = 0;
|
|
}
|
|
if (tp->retrans_out) {
|
|
pr_debug("Leak r=%u %d\n",
|
|
tp->retrans_out, icsk->icsk_ca_state);
|
|
tp->retrans_out = 0;
|
|
}
|
|
}
|
|
#endif
|
|
return flag;
|
|
}
|
|
|
|
static void tcp_ack_probe(struct sock *sk)
|
|
{
|
|
const struct tcp_sock *tp = tcp_sk(sk);
|
|
struct inet_connection_sock *icsk = inet_csk(sk);
|
|
|
|
/* Was it a usable window open? */
|
|
|
|
if (!after(TCP_SKB_CB(tcp_send_head(sk))->end_seq, tcp_wnd_end(tp))) {
|
|
icsk->icsk_backoff = 0;
|
|
inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0);
|
|
/* Socket must be waked up by subsequent tcp_data_snd_check().
|
|
* This function is not for random using!
|
|
*/
|
|
} else {
|
|
unsigned long when = tcp_probe0_when(sk, TCP_RTO_MAX);
|
|
|
|
inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
|
|
when, TCP_RTO_MAX);
|
|
}
|
|
}
|
|
|
|
static inline bool tcp_ack_is_dubious(const struct sock *sk, const int flag)
|
|
{
|
|
return !(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) ||
|
|
inet_csk(sk)->icsk_ca_state != TCP_CA_Open;
|
|
}
|
|
|
|
/* Decide wheather to run the increase function of congestion control. */
|
|
static inline bool tcp_may_raise_cwnd(const struct sock *sk, const int flag)
|
|
{
|
|
if (tcp_in_cwnd_reduction(sk))
|
|
return false;
|
|
|
|
/* If reordering is high then always grow cwnd whenever data is
|
|
* delivered regardless of its ordering. Otherwise stay conservative
|
|
* and only grow cwnd on in-order delivery (RFC5681). A stretched ACK w/
|
|
* new SACK or ECE mark may first advance cwnd here and later reduce
|
|
* cwnd in tcp_fastretrans_alert() based on more states.
|
|
*/
|
|
if (tcp_sk(sk)->reordering > sysctl_tcp_reordering)
|
|
return flag & FLAG_FORWARD_PROGRESS;
|
|
|
|
return flag & FLAG_DATA_ACKED;
|
|
}
|
|
|
|
/* Check that window update is acceptable.
|
|
* The function assumes that snd_una<=ack<=snd_next.
|
|
*/
|
|
static inline bool tcp_may_update_window(const struct tcp_sock *tp,
|
|
const u32 ack, const u32 ack_seq,
|
|
const u32 nwin)
|
|
{
|
|
return after(ack, tp->snd_una) ||
|
|
after(ack_seq, tp->snd_wl1) ||
|
|
(ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd);
|
|
}
|
|
|
|
/* If we update tp->snd_una, also update tp->bytes_acked */
|
|
static void tcp_snd_una_update(struct tcp_sock *tp, u32 ack)
|
|
{
|
|
u32 delta = ack - tp->snd_una;
|
|
|
|
u64_stats_update_begin(&tp->syncp);
|
|
tp->bytes_acked += delta;
|
|
u64_stats_update_end(&tp->syncp);
|
|
tp->snd_una = ack;
|
|
}
|
|
|
|
/* If we update tp->rcv_nxt, also update tp->bytes_received */
|
|
static void tcp_rcv_nxt_update(struct tcp_sock *tp, u32 seq)
|
|
{
|
|
u32 delta = seq - tp->rcv_nxt;
|
|
|
|
u64_stats_update_begin(&tp->syncp);
|
|
tp->bytes_received += delta;
|
|
u64_stats_update_end(&tp->syncp);
|
|
tp->rcv_nxt = seq;
|
|
}
|
|
|
|
/* Update our send window.
|
|
*
|
|
* Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
|
|
* and in FreeBSD. NetBSD's one is even worse.) is wrong.
|
|
*/
|
|
static int tcp_ack_update_window(struct sock *sk, const struct sk_buff *skb, u32 ack,
|
|
u32 ack_seq)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
int flag = 0;
|
|
u32 nwin = ntohs(tcp_hdr(skb)->window);
|
|
|
|
if (likely(!tcp_hdr(skb)->syn))
|
|
nwin <<= tp->rx_opt.snd_wscale;
|
|
|
|
if (tcp_may_update_window(tp, ack, ack_seq, nwin)) {
|
|
flag |= FLAG_WIN_UPDATE;
|
|
tcp_update_wl(tp, ack_seq);
|
|
|
|
if (tp->snd_wnd != nwin) {
|
|
tp->snd_wnd = nwin;
|
|
|
|
/* Note, it is the only place, where
|
|
* fast path is recovered for sending TCP.
|
|
*/
|
|
tp->pred_flags = 0;
|
|
tcp_fast_path_check(sk);
|
|
|
|
if (tcp_send_head(sk))
|
|
tcp_slow_start_after_idle_check(sk);
|
|
|
|
if (nwin > tp->max_window) {
|
|
tp->max_window = nwin;
|
|
tcp_sync_mss(sk, inet_csk(sk)->icsk_pmtu_cookie);
|
|
}
|
|
}
|
|
}
|
|
|
|
tcp_snd_una_update(tp, ack);
|
|
|
|
return flag;
|
|
}
|
|
|
|
/* Return true if we're currently rate-limiting out-of-window ACKs and
|
|
* thus shouldn't send a dupack right now. We rate-limit dupacks in
|
|
* response to out-of-window SYNs or ACKs to mitigate ACK loops or DoS
|
|
* attacks that send repeated SYNs or ACKs for the same connection. To
|
|
* do this, we do not send a duplicate SYNACK or ACK if the remote
|
|
* endpoint is sending out-of-window SYNs or pure ACKs at a high rate.
|
|
*/
|
|
bool tcp_oow_rate_limited(struct net *net, const struct sk_buff *skb,
|
|
int mib_idx, u32 *last_oow_ack_time)
|
|
{
|
|
/* Data packets without SYNs are not likely part of an ACK loop. */
|
|
if ((TCP_SKB_CB(skb)->seq != TCP_SKB_CB(skb)->end_seq) &&
|
|
!tcp_hdr(skb)->syn)
|
|
goto not_rate_limited;
|
|
|
|
if (*last_oow_ack_time) {
|
|
s32 elapsed = (s32)(tcp_time_stamp - *last_oow_ack_time);
|
|
|
|
if (0 <= elapsed && elapsed < sysctl_tcp_invalid_ratelimit) {
|
|
NET_INC_STATS_BH(net, mib_idx);
|
|
return true; /* rate-limited: don't send yet! */
|
|
}
|
|
}
|
|
|
|
*last_oow_ack_time = tcp_time_stamp;
|
|
|
|
not_rate_limited:
|
|
return false; /* not rate-limited: go ahead, send dupack now! */
|
|
}
|
|
|
|
/* RFC 5961 7 [ACK Throttling] */
|
|
static void tcp_send_challenge_ack(struct sock *sk, const struct sk_buff *skb)
|
|
{
|
|
/* unprotected vars, we dont care of overwrites */
|
|
static u32 challenge_timestamp;
|
|
static unsigned int challenge_count;
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
u32 now;
|
|
|
|
/* First check our per-socket dupack rate limit. */
|
|
if (tcp_oow_rate_limited(sock_net(sk), skb,
|
|
LINUX_MIB_TCPACKSKIPPEDCHALLENGE,
|
|
&tp->last_oow_ack_time))
|
|
return;
|
|
|
|
/* Then check the check host-wide RFC 5961 rate limit. */
|
|
now = jiffies / HZ;
|
|
if (now != challenge_timestamp) {
|
|
challenge_timestamp = now;
|
|
challenge_count = 0;
|
|
}
|
|
if (++challenge_count <= sysctl_tcp_challenge_ack_limit) {
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPCHALLENGEACK);
|
|
tcp_send_ack(sk);
|
|
}
|
|
}
|
|
|
|
static void tcp_store_ts_recent(struct tcp_sock *tp)
|
|
{
|
|
tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval;
|
|
tp->rx_opt.ts_recent_stamp = get_seconds();
|
|
}
|
|
|
|
static void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq)
|
|
{
|
|
if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) {
|
|
/* PAWS bug workaround wrt. ACK frames, the PAWS discard
|
|
* extra check below makes sure this can only happen
|
|
* for pure ACK frames. -DaveM
|
|
*
|
|
* Not only, also it occurs for expired timestamps.
|
|
*/
|
|
|
|
if (tcp_paws_check(&tp->rx_opt, 0))
|
|
tcp_store_ts_recent(tp);
|
|
}
|
|
}
|
|
|
|
/* This routine deals with acks during a TLP episode.
|
|
* We mark the end of a TLP episode on receiving TLP dupack or when
|
|
* ack is after tlp_high_seq.
|
|
* Ref: loss detection algorithm in draft-dukkipati-tcpm-tcp-loss-probe.
|
|
*/
|
|
static void tcp_process_tlp_ack(struct sock *sk, u32 ack, int flag)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
if (before(ack, tp->tlp_high_seq))
|
|
return;
|
|
|
|
if (flag & FLAG_DSACKING_ACK) {
|
|
/* This DSACK means original and TLP probe arrived; no loss */
|
|
tp->tlp_high_seq = 0;
|
|
} else if (after(ack, tp->tlp_high_seq)) {
|
|
/* ACK advances: there was a loss, so reduce cwnd. Reset
|
|
* tlp_high_seq in tcp_init_cwnd_reduction()
|
|
*/
|
|
tcp_init_cwnd_reduction(sk);
|
|
tcp_set_ca_state(sk, TCP_CA_CWR);
|
|
tcp_end_cwnd_reduction(sk);
|
|
tcp_try_keep_open(sk);
|
|
NET_INC_STATS_BH(sock_net(sk),
|
|
LINUX_MIB_TCPLOSSPROBERECOVERY);
|
|
} else if (!(flag & (FLAG_SND_UNA_ADVANCED |
|
|
FLAG_NOT_DUP | FLAG_DATA_SACKED))) {
|
|
/* Pure dupack: original and TLP probe arrived; no loss */
|
|
tp->tlp_high_seq = 0;
|
|
}
|
|
}
|
|
|
|
static inline void tcp_in_ack_event(struct sock *sk, u32 flags)
|
|
{
|
|
const struct inet_connection_sock *icsk = inet_csk(sk);
|
|
|
|
if (icsk->icsk_ca_ops->in_ack_event)
|
|
icsk->icsk_ca_ops->in_ack_event(sk, flags);
|
|
}
|
|
|
|
/* This routine deals with incoming acks, but not outgoing ones. */
|
|
static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
|
|
{
|
|
struct inet_connection_sock *icsk = inet_csk(sk);
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct tcp_sacktag_state sack_state;
|
|
u32 prior_snd_una = tp->snd_una;
|
|
u32 ack_seq = TCP_SKB_CB(skb)->seq;
|
|
u32 ack = TCP_SKB_CB(skb)->ack_seq;
|
|
bool is_dupack = false;
|
|
u32 prior_fackets;
|
|
int prior_packets = tp->packets_out;
|
|
const int prior_unsacked = tp->packets_out - tp->sacked_out;
|
|
int acked = 0; /* Number of packets newly acked */
|
|
|
|
sack_state.first_sackt.v64 = 0;
|
|
|
|
/* We very likely will need to access write queue head. */
|
|
prefetchw(sk->sk_write_queue.next);
|
|
|
|
/* If the ack is older than previous acks
|
|
* then we can probably ignore it.
|
|
*/
|
|
if (before(ack, prior_snd_una)) {
|
|
/* RFC 5961 5.2 [Blind Data Injection Attack].[Mitigation] */
|
|
if (before(ack, prior_snd_una - tp->max_window)) {
|
|
tcp_send_challenge_ack(sk, skb);
|
|
return -1;
|
|
}
|
|
goto old_ack;
|
|
}
|
|
|
|
/* If the ack includes data we haven't sent yet, discard
|
|
* this segment (RFC793 Section 3.9).
|
|
*/
|
|
if (after(ack, tp->snd_nxt))
|
|
goto invalid_ack;
|
|
|
|
if (icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS ||
|
|
icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)
|
|
tcp_rearm_rto(sk);
|
|
|
|
if (after(ack, prior_snd_una)) {
|
|
flag |= FLAG_SND_UNA_ADVANCED;
|
|
icsk->icsk_retransmits = 0;
|
|
}
|
|
|
|
prior_fackets = tp->fackets_out;
|
|
|
|
/* ts_recent update must be made after we are sure that the packet
|
|
* is in window.
|
|
*/
|
|
if (flag & FLAG_UPDATE_TS_RECENT)
|
|
tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
|
|
|
|
if (!(flag & FLAG_SLOWPATH) && after(ack, prior_snd_una)) {
|
|
/* Window is constant, pure forward advance.
|
|
* No more checks are required.
|
|
* Note, we use the fact that SND.UNA>=SND.WL2.
|
|
*/
|
|
tcp_update_wl(tp, ack_seq);
|
|
tcp_snd_una_update(tp, ack);
|
|
flag |= FLAG_WIN_UPDATE;
|
|
|
|
tcp_in_ack_event(sk, CA_ACK_WIN_UPDATE);
|
|
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPACKS);
|
|
} else {
|
|
u32 ack_ev_flags = CA_ACK_SLOWPATH;
|
|
|
|
if (ack_seq != TCP_SKB_CB(skb)->end_seq)
|
|
flag |= FLAG_DATA;
|
|
else
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPPUREACKS);
|
|
|
|
flag |= tcp_ack_update_window(sk, skb, ack, ack_seq);
|
|
|
|
if (TCP_SKB_CB(skb)->sacked)
|
|
flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una,
|
|
&sack_state);
|
|
|
|
if (tcp_ecn_rcv_ecn_echo(tp, tcp_hdr(skb))) {
|
|
flag |= FLAG_ECE;
|
|
ack_ev_flags |= CA_ACK_ECE;
|
|
}
|
|
|
|
if (flag & FLAG_WIN_UPDATE)
|
|
ack_ev_flags |= CA_ACK_WIN_UPDATE;
|
|
|
|
tcp_in_ack_event(sk, ack_ev_flags);
|
|
}
|
|
|
|
/* We passed data and got it acked, remove any soft error
|
|
* log. Something worked...
|
|
*/
|
|
sk->sk_err_soft = 0;
|
|
icsk->icsk_probes_out = 0;
|
|
tp->rcv_tstamp = tcp_time_stamp;
|
|
if (!prior_packets)
|
|
goto no_queue;
|
|
|
|
/* See if we can take anything off of the retransmit queue. */
|
|
acked = tp->packets_out;
|
|
flag |= tcp_clean_rtx_queue(sk, prior_fackets, prior_snd_una,
|
|
&sack_state);
|
|
acked -= tp->packets_out;
|
|
|
|
if (tcp_ack_is_dubious(sk, flag)) {
|
|
is_dupack = !(flag & (FLAG_SND_UNA_ADVANCED | FLAG_NOT_DUP));
|
|
tcp_fastretrans_alert(sk, acked, prior_unsacked,
|
|
is_dupack, flag);
|
|
}
|
|
if (tp->tlp_high_seq)
|
|
tcp_process_tlp_ack(sk, ack, flag);
|
|
|
|
/* Advance cwnd if state allows */
|
|
if (tcp_may_raise_cwnd(sk, flag))
|
|
tcp_cong_avoid(sk, ack, acked);
|
|
|
|
if ((flag & FLAG_FORWARD_PROGRESS) || !(flag & FLAG_NOT_DUP)) {
|
|
struct dst_entry *dst = __sk_dst_get(sk);
|
|
if (dst)
|
|
dst_confirm(dst);
|
|
}
|
|
|
|
if (icsk->icsk_pending == ICSK_TIME_RETRANS)
|
|
tcp_schedule_loss_probe(sk);
|
|
tcp_update_pacing_rate(sk);
|
|
return 1;
|
|
|
|
no_queue:
|
|
/* If data was DSACKed, see if we can undo a cwnd reduction. */
|
|
if (flag & FLAG_DSACKING_ACK)
|
|
tcp_fastretrans_alert(sk, acked, prior_unsacked,
|
|
is_dupack, flag);
|
|
/* If this ack opens up a zero window, clear backoff. It was
|
|
* being used to time the probes, and is probably far higher than
|
|
* it needs to be for normal retransmission.
|
|
*/
|
|
if (tcp_send_head(sk))
|
|
tcp_ack_probe(sk);
|
|
|
|
if (tp->tlp_high_seq)
|
|
tcp_process_tlp_ack(sk, ack, flag);
|
|
return 1;
|
|
|
|
invalid_ack:
|
|
SOCK_DEBUG(sk, "Ack %u after %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
|
|
return -1;
|
|
|
|
old_ack:
|
|
/* If data was SACKed, tag it and see if we should send more data.
|
|
* If data was DSACKed, see if we can undo a cwnd reduction.
|
|
*/
|
|
if (TCP_SKB_CB(skb)->sacked) {
|
|
flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una,
|
|
&sack_state);
|
|
tcp_fastretrans_alert(sk, acked, prior_unsacked,
|
|
is_dupack, flag);
|
|
}
|
|
|
|
SOCK_DEBUG(sk, "Ack %u before %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
|
|
return 0;
|
|
}
|
|
|
|
static void tcp_parse_fastopen_option(int len, const unsigned char *cookie,
|
|
bool syn, struct tcp_fastopen_cookie *foc,
|
|
bool exp_opt)
|
|
{
|
|
/* Valid only in SYN or SYN-ACK with an even length. */
|
|
if (!foc || !syn || len < 0 || (len & 1))
|
|
return;
|
|
|
|
if (len >= TCP_FASTOPEN_COOKIE_MIN &&
|
|
len <= TCP_FASTOPEN_COOKIE_MAX)
|
|
memcpy(foc->val, cookie, len);
|
|
else if (len != 0)
|
|
len = -1;
|
|
foc->len = len;
|
|
foc->exp = exp_opt;
|
|
}
|
|
|
|
/* Look for tcp options. Normally only called on SYN and SYNACK packets.
|
|
* But, this can also be called on packets in the established flow when
|
|
* the fast version below fails.
|
|
*/
|
|
void tcp_parse_options(const struct sk_buff *skb,
|
|
struct tcp_options_received *opt_rx, int estab,
|
|
struct tcp_fastopen_cookie *foc)
|
|
{
|
|
const unsigned char *ptr;
|
|
const struct tcphdr *th = tcp_hdr(skb);
|
|
int length = (th->doff * 4) - sizeof(struct tcphdr);
|
|
|
|
ptr = (const unsigned char *)(th + 1);
|
|
opt_rx->saw_tstamp = 0;
|
|
|
|
while (length > 0) {
|
|
int opcode = *ptr++;
|
|
int opsize;
|
|
|
|
switch (opcode) {
|
|
case TCPOPT_EOL:
|
|
return;
|
|
case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
|
|
length--;
|
|
continue;
|
|
default:
|
|
opsize = *ptr++;
|
|
if (opsize < 2) /* "silly options" */
|
|
return;
|
|
if (opsize > length)
|
|
return; /* don't parse partial options */
|
|
switch (opcode) {
|
|
case TCPOPT_MSS:
|
|
if (opsize == TCPOLEN_MSS && th->syn && !estab) {
|
|
u16 in_mss = get_unaligned_be16(ptr);
|
|
if (in_mss) {
|
|
if (opt_rx->user_mss &&
|
|
opt_rx->user_mss < in_mss)
|
|
in_mss = opt_rx->user_mss;
|
|
opt_rx->mss_clamp = in_mss;
|
|
}
|
|
}
|
|
break;
|
|
case TCPOPT_WINDOW:
|
|
if (opsize == TCPOLEN_WINDOW && th->syn &&
|
|
!estab && sysctl_tcp_window_scaling) {
|
|
__u8 snd_wscale = *(__u8 *)ptr;
|
|
opt_rx->wscale_ok = 1;
|
|
if (snd_wscale > 14) {
|
|
net_info_ratelimited("%s: Illegal window scaling value %d >14 received\n",
|
|
__func__,
|
|
snd_wscale);
|
|
snd_wscale = 14;
|
|
}
|
|
opt_rx->snd_wscale = snd_wscale;
|
|
}
|
|
break;
|
|
case TCPOPT_TIMESTAMP:
|
|
if ((opsize == TCPOLEN_TIMESTAMP) &&
|
|
((estab && opt_rx->tstamp_ok) ||
|
|
(!estab && sysctl_tcp_timestamps))) {
|
|
opt_rx->saw_tstamp = 1;
|
|
opt_rx->rcv_tsval = get_unaligned_be32(ptr);
|
|
opt_rx->rcv_tsecr = get_unaligned_be32(ptr + 4);
|
|
}
|
|
break;
|
|
case TCPOPT_SACK_PERM:
|
|
if (opsize == TCPOLEN_SACK_PERM && th->syn &&
|
|
!estab && sysctl_tcp_sack) {
|
|
opt_rx->sack_ok = TCP_SACK_SEEN;
|
|
tcp_sack_reset(opt_rx);
|
|
}
|
|
break;
|
|
|
|
case TCPOPT_SACK:
|
|
if ((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) &&
|
|
!((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) &&
|
|
opt_rx->sack_ok) {
|
|
TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th;
|
|
}
|
|
break;
|
|
#ifdef CONFIG_TCP_MD5SIG
|
|
case TCPOPT_MD5SIG:
|
|
/*
|
|
* The MD5 Hash has already been
|
|
* checked (see tcp_v{4,6}_do_rcv()).
|
|
*/
|
|
break;
|
|
#endif
|
|
case TCPOPT_FASTOPEN:
|
|
tcp_parse_fastopen_option(
|
|
opsize - TCPOLEN_FASTOPEN_BASE,
|
|
ptr, th->syn, foc, false);
|
|
break;
|
|
|
|
case TCPOPT_EXP:
|
|
/* Fast Open option shares code 254 using a
|
|
* 16 bits magic number.
|
|
*/
|
|
if (opsize >= TCPOLEN_EXP_FASTOPEN_BASE &&
|
|
get_unaligned_be16(ptr) ==
|
|
TCPOPT_FASTOPEN_MAGIC)
|
|
tcp_parse_fastopen_option(opsize -
|
|
TCPOLEN_EXP_FASTOPEN_BASE,
|
|
ptr + 2, th->syn, foc, true);
|
|
break;
|
|
|
|
}
|
|
ptr += opsize-2;
|
|
length -= opsize;
|
|
}
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(tcp_parse_options);
|
|
|
|
static bool tcp_parse_aligned_timestamp(struct tcp_sock *tp, const struct tcphdr *th)
|
|
{
|
|
const __be32 *ptr = (const __be32 *)(th + 1);
|
|
|
|
if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
|
|
| (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) {
|
|
tp->rx_opt.saw_tstamp = 1;
|
|
++ptr;
|
|
tp->rx_opt.rcv_tsval = ntohl(*ptr);
|
|
++ptr;
|
|
if (*ptr)
|
|
tp->rx_opt.rcv_tsecr = ntohl(*ptr) - tp->tsoffset;
|
|
else
|
|
tp->rx_opt.rcv_tsecr = 0;
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/* Fast parse options. This hopes to only see timestamps.
|
|
* If it is wrong it falls back on tcp_parse_options().
|
|
*/
|
|
static bool tcp_fast_parse_options(const struct sk_buff *skb,
|
|
const struct tcphdr *th, struct tcp_sock *tp)
|
|
{
|
|
/* In the spirit of fast parsing, compare doff directly to constant
|
|
* values. Because equality is used, short doff can be ignored here.
|
|
*/
|
|
if (th->doff == (sizeof(*th) / 4)) {
|
|
tp->rx_opt.saw_tstamp = 0;
|
|
return false;
|
|
} else if (tp->rx_opt.tstamp_ok &&
|
|
th->doff == ((sizeof(*th) + TCPOLEN_TSTAMP_ALIGNED) / 4)) {
|
|
if (tcp_parse_aligned_timestamp(tp, th))
|
|
return true;
|
|
}
|
|
|
|
tcp_parse_options(skb, &tp->rx_opt, 1, NULL);
|
|
if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
|
|
tp->rx_opt.rcv_tsecr -= tp->tsoffset;
|
|
|
|
return true;
|
|
}
|
|
|
|
#ifdef CONFIG_TCP_MD5SIG
|
|
/*
|
|
* Parse MD5 Signature option
|
|
*/
|
|
const u8 *tcp_parse_md5sig_option(const struct tcphdr *th)
|
|
{
|
|
int length = (th->doff << 2) - sizeof(*th);
|
|
const u8 *ptr = (const u8 *)(th + 1);
|
|
|
|
/* If the TCP option is too short, we can short cut */
|
|
if (length < TCPOLEN_MD5SIG)
|
|
return NULL;
|
|
|
|
while (length > 0) {
|
|
int opcode = *ptr++;
|
|
int opsize;
|
|
|
|
switch (opcode) {
|
|
case TCPOPT_EOL:
|
|
return NULL;
|
|
case TCPOPT_NOP:
|
|
length--;
|
|
continue;
|
|
default:
|
|
opsize = *ptr++;
|
|
if (opsize < 2 || opsize > length)
|
|
return NULL;
|
|
if (opcode == TCPOPT_MD5SIG)
|
|
return opsize == TCPOLEN_MD5SIG ? ptr : NULL;
|
|
}
|
|
ptr += opsize - 2;
|
|
length -= opsize;
|
|
}
|
|
return NULL;
|
|
}
|
|
EXPORT_SYMBOL(tcp_parse_md5sig_option);
|
|
#endif
|
|
|
|
/* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
|
|
*
|
|
* It is not fatal. If this ACK does _not_ change critical state (seqs, window)
|
|
* it can pass through stack. So, the following predicate verifies that
|
|
* this segment is not used for anything but congestion avoidance or
|
|
* fast retransmit. Moreover, we even are able to eliminate most of such
|
|
* second order effects, if we apply some small "replay" window (~RTO)
|
|
* to timestamp space.
|
|
*
|
|
* All these measures still do not guarantee that we reject wrapped ACKs
|
|
* on networks with high bandwidth, when sequence space is recycled fastly,
|
|
* but it guarantees that such events will be very rare and do not affect
|
|
* connection seriously. This doesn't look nice, but alas, PAWS is really
|
|
* buggy extension.
|
|
*
|
|
* [ Later note. Even worse! It is buggy for segments _with_ data. RFC
|
|
* states that events when retransmit arrives after original data are rare.
|
|
* It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
|
|
* the biggest problem on large power networks even with minor reordering.
|
|
* OK, let's give it small replay window. If peer clock is even 1hz, it is safe
|
|
* up to bandwidth of 18Gigabit/sec. 8) ]
|
|
*/
|
|
|
|
static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb)
|
|
{
|
|
const struct tcp_sock *tp = tcp_sk(sk);
|
|
const struct tcphdr *th = tcp_hdr(skb);
|
|
u32 seq = TCP_SKB_CB(skb)->seq;
|
|
u32 ack = TCP_SKB_CB(skb)->ack_seq;
|
|
|
|
return (/* 1. Pure ACK with correct sequence number. */
|
|
(th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) &&
|
|
|
|
/* 2. ... and duplicate ACK. */
|
|
ack == tp->snd_una &&
|
|
|
|
/* 3. ... and does not update window. */
|
|
!tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) &&
|
|
|
|
/* 4. ... and sits in replay window. */
|
|
(s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (inet_csk(sk)->icsk_rto * 1024) / HZ);
|
|
}
|
|
|
|
static inline bool tcp_paws_discard(const struct sock *sk,
|
|
const struct sk_buff *skb)
|
|
{
|
|
const struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
return !tcp_paws_check(&tp->rx_opt, TCP_PAWS_WINDOW) &&
|
|
!tcp_disordered_ack(sk, skb);
|
|
}
|
|
|
|
/* Check segment sequence number for validity.
|
|
*
|
|
* Segment controls are considered valid, if the segment
|
|
* fits to the window after truncation to the window. Acceptability
|
|
* of data (and SYN, FIN, of course) is checked separately.
|
|
* See tcp_data_queue(), for example.
|
|
*
|
|
* Also, controls (RST is main one) are accepted using RCV.WUP instead
|
|
* of RCV.NXT. Peer still did not advance his SND.UNA when we
|
|
* delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
|
|
* (borrowed from freebsd)
|
|
*/
|
|
|
|
static inline bool tcp_sequence(const struct tcp_sock *tp, u32 seq, u32 end_seq)
|
|
{
|
|
return !before(end_seq, tp->rcv_wup) &&
|
|
!after(seq, tp->rcv_nxt + tcp_receive_window(tp));
|
|
}
|
|
|
|
/* When we get a reset we do this. */
|
|
void tcp_reset(struct sock *sk)
|
|
{
|
|
/* We want the right error as BSD sees it (and indeed as we do). */
|
|
switch (sk->sk_state) {
|
|
case TCP_SYN_SENT:
|
|
sk->sk_err = ECONNREFUSED;
|
|
break;
|
|
case TCP_CLOSE_WAIT:
|
|
sk->sk_err = EPIPE;
|
|
break;
|
|
case TCP_CLOSE:
|
|
return;
|
|
default:
|
|
sk->sk_err = ECONNRESET;
|
|
}
|
|
/* This barrier is coupled with smp_rmb() in tcp_poll() */
|
|
smp_wmb();
|
|
|
|
if (!sock_flag(sk, SOCK_DEAD))
|
|
sk->sk_error_report(sk);
|
|
|
|
tcp_done(sk);
|
|
}
|
|
|
|
/*
|
|
* Process the FIN bit. This now behaves as it is supposed to work
|
|
* and the FIN takes effect when it is validly part of sequence
|
|
* space. Not before when we get holes.
|
|
*
|
|
* If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
|
|
* (and thence onto LAST-ACK and finally, CLOSE, we never enter
|
|
* TIME-WAIT)
|
|
*
|
|
* If we are in FINWAIT-1, a received FIN indicates simultaneous
|
|
* close and we go into CLOSING (and later onto TIME-WAIT)
|
|
*
|
|
* If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
|
|
*/
|
|
static void tcp_fin(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
inet_csk_schedule_ack(sk);
|
|
|
|
sk->sk_shutdown |= RCV_SHUTDOWN;
|
|
sock_set_flag(sk, SOCK_DONE);
|
|
|
|
switch (sk->sk_state) {
|
|
case TCP_SYN_RECV:
|
|
case TCP_ESTABLISHED:
|
|
/* Move to CLOSE_WAIT */
|
|
tcp_set_state(sk, TCP_CLOSE_WAIT);
|
|
inet_csk(sk)->icsk_ack.pingpong = 1;
|
|
break;
|
|
|
|
case TCP_CLOSE_WAIT:
|
|
case TCP_CLOSING:
|
|
/* Received a retransmission of the FIN, do
|
|
* nothing.
|
|
*/
|
|
break;
|
|
case TCP_LAST_ACK:
|
|
/* RFC793: Remain in the LAST-ACK state. */
|
|
break;
|
|
|
|
case TCP_FIN_WAIT1:
|
|
/* This case occurs when a simultaneous close
|
|
* happens, we must ack the received FIN and
|
|
* enter the CLOSING state.
|
|
*/
|
|
tcp_send_ack(sk);
|
|
tcp_set_state(sk, TCP_CLOSING);
|
|
break;
|
|
case TCP_FIN_WAIT2:
|
|
/* Received a FIN -- send ACK and enter TIME_WAIT. */
|
|
tcp_send_ack(sk);
|
|
tcp_time_wait(sk, TCP_TIME_WAIT, 0);
|
|
break;
|
|
default:
|
|
/* Only TCP_LISTEN and TCP_CLOSE are left, in these
|
|
* cases we should never reach this piece of code.
|
|
*/
|
|
pr_err("%s: Impossible, sk->sk_state=%d\n",
|
|
__func__, sk->sk_state);
|
|
break;
|
|
}
|
|
|
|
/* It _is_ possible, that we have something out-of-order _after_ FIN.
|
|
* Probably, we should reset in this case. For now drop them.
|
|
*/
|
|
__skb_queue_purge(&tp->out_of_order_queue);
|
|
if (tcp_is_sack(tp))
|
|
tcp_sack_reset(&tp->rx_opt);
|
|
sk_mem_reclaim(sk);
|
|
|
|
if (!sock_flag(sk, SOCK_DEAD)) {
|
|
sk->sk_state_change(sk);
|
|
|
|
/* Do not send POLL_HUP for half duplex close. */
|
|
if (sk->sk_shutdown == SHUTDOWN_MASK ||
|
|
sk->sk_state == TCP_CLOSE)
|
|
sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
|
|
else
|
|
sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN);
|
|
}
|
|
}
|
|
|
|
static inline bool tcp_sack_extend(struct tcp_sack_block *sp, u32 seq,
|
|
u32 end_seq)
|
|
{
|
|
if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) {
|
|
if (before(seq, sp->start_seq))
|
|
sp->start_seq = seq;
|
|
if (after(end_seq, sp->end_seq))
|
|
sp->end_seq = end_seq;
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
static void tcp_dsack_set(struct sock *sk, u32 seq, u32 end_seq)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
if (tcp_is_sack(tp) && sysctl_tcp_dsack) {
|
|
int mib_idx;
|
|
|
|
if (before(seq, tp->rcv_nxt))
|
|
mib_idx = LINUX_MIB_TCPDSACKOLDSENT;
|
|
else
|
|
mib_idx = LINUX_MIB_TCPDSACKOFOSENT;
|
|
|
|
NET_INC_STATS_BH(sock_net(sk), mib_idx);
|
|
|
|
tp->rx_opt.dsack = 1;
|
|
tp->duplicate_sack[0].start_seq = seq;
|
|
tp->duplicate_sack[0].end_seq = end_seq;
|
|
}
|
|
}
|
|
|
|
static void tcp_dsack_extend(struct sock *sk, u32 seq, u32 end_seq)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
if (!tp->rx_opt.dsack)
|
|
tcp_dsack_set(sk, seq, end_seq);
|
|
else
|
|
tcp_sack_extend(tp->duplicate_sack, seq, end_seq);
|
|
}
|
|
|
|
static void tcp_send_dupack(struct sock *sk, const struct sk_buff *skb)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
|
|
before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOST);
|
|
tcp_enter_quickack_mode(sk);
|
|
|
|
if (tcp_is_sack(tp) && sysctl_tcp_dsack) {
|
|
u32 end_seq = TCP_SKB_CB(skb)->end_seq;
|
|
|
|
if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))
|
|
end_seq = tp->rcv_nxt;
|
|
tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, end_seq);
|
|
}
|
|
}
|
|
|
|
tcp_send_ack(sk);
|
|
}
|
|
|
|
/* These routines update the SACK block as out-of-order packets arrive or
|
|
* in-order packets close up the sequence space.
|
|
*/
|
|
static void tcp_sack_maybe_coalesce(struct tcp_sock *tp)
|
|
{
|
|
int this_sack;
|
|
struct tcp_sack_block *sp = &tp->selective_acks[0];
|
|
struct tcp_sack_block *swalk = sp + 1;
|
|
|
|
/* See if the recent change to the first SACK eats into
|
|
* or hits the sequence space of other SACK blocks, if so coalesce.
|
|
*/
|
|
for (this_sack = 1; this_sack < tp->rx_opt.num_sacks;) {
|
|
if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) {
|
|
int i;
|
|
|
|
/* Zap SWALK, by moving every further SACK up by one slot.
|
|
* Decrease num_sacks.
|
|
*/
|
|
tp->rx_opt.num_sacks--;
|
|
for (i = this_sack; i < tp->rx_opt.num_sacks; i++)
|
|
sp[i] = sp[i + 1];
|
|
continue;
|
|
}
|
|
this_sack++, swalk++;
|
|
}
|
|
}
|
|
|
|
static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct tcp_sack_block *sp = &tp->selective_acks[0];
|
|
int cur_sacks = tp->rx_opt.num_sacks;
|
|
int this_sack;
|
|
|
|
if (!cur_sacks)
|
|
goto new_sack;
|
|
|
|
for (this_sack = 0; this_sack < cur_sacks; this_sack++, sp++) {
|
|
if (tcp_sack_extend(sp, seq, end_seq)) {
|
|
/* Rotate this_sack to the first one. */
|
|
for (; this_sack > 0; this_sack--, sp--)
|
|
swap(*sp, *(sp - 1));
|
|
if (cur_sacks > 1)
|
|
tcp_sack_maybe_coalesce(tp);
|
|
return;
|
|
}
|
|
}
|
|
|
|
/* Could not find an adjacent existing SACK, build a new one,
|
|
* put it at the front, and shift everyone else down. We
|
|
* always know there is at least one SACK present already here.
|
|
*
|
|
* If the sack array is full, forget about the last one.
|
|
*/
|
|
if (this_sack >= TCP_NUM_SACKS) {
|
|
this_sack--;
|
|
tp->rx_opt.num_sacks--;
|
|
sp--;
|
|
}
|
|
for (; this_sack > 0; this_sack--, sp--)
|
|
*sp = *(sp - 1);
|
|
|
|
new_sack:
|
|
/* Build the new head SACK, and we're done. */
|
|
sp->start_seq = seq;
|
|
sp->end_seq = end_seq;
|
|
tp->rx_opt.num_sacks++;
|
|
}
|
|
|
|
/* RCV.NXT advances, some SACKs should be eaten. */
|
|
|
|
static void tcp_sack_remove(struct tcp_sock *tp)
|
|
{
|
|
struct tcp_sack_block *sp = &tp->selective_acks[0];
|
|
int num_sacks = tp->rx_opt.num_sacks;
|
|
int this_sack;
|
|
|
|
/* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
|
|
if (skb_queue_empty(&tp->out_of_order_queue)) {
|
|
tp->rx_opt.num_sacks = 0;
|
|
return;
|
|
}
|
|
|
|
for (this_sack = 0; this_sack < num_sacks;) {
|
|
/* Check if the start of the sack is covered by RCV.NXT. */
|
|
if (!before(tp->rcv_nxt, sp->start_seq)) {
|
|
int i;
|
|
|
|
/* RCV.NXT must cover all the block! */
|
|
WARN_ON(before(tp->rcv_nxt, sp->end_seq));
|
|
|
|
/* Zap this SACK, by moving forward any other SACKS. */
|
|
for (i = this_sack+1; i < num_sacks; i++)
|
|
tp->selective_acks[i-1] = tp->selective_acks[i];
|
|
num_sacks--;
|
|
continue;
|
|
}
|
|
this_sack++;
|
|
sp++;
|
|
}
|
|
tp->rx_opt.num_sacks = num_sacks;
|
|
}
|
|
|
|
/**
|
|
* tcp_try_coalesce - try to merge skb to prior one
|
|
* @sk: socket
|
|
* @to: prior buffer
|
|
* @from: buffer to add in queue
|
|
* @fragstolen: pointer to boolean
|
|
*
|
|
* Before queueing skb @from after @to, try to merge them
|
|
* to reduce overall memory use and queue lengths, if cost is small.
|
|
* Packets in ofo or receive queues can stay a long time.
|
|
* Better try to coalesce them right now to avoid future collapses.
|
|
* Returns true if caller should free @from instead of queueing it
|
|
*/
|
|
static bool tcp_try_coalesce(struct sock *sk,
|
|
struct sk_buff *to,
|
|
struct sk_buff *from,
|
|
bool *fragstolen)
|
|
{
|
|
int delta;
|
|
|
|
*fragstolen = false;
|
|
|
|
/* Its possible this segment overlaps with prior segment in queue */
|
|
if (TCP_SKB_CB(from)->seq != TCP_SKB_CB(to)->end_seq)
|
|
return false;
|
|
|
|
if (!skb_try_coalesce(to, from, fragstolen, &delta))
|
|
return false;
|
|
|
|
atomic_add(delta, &sk->sk_rmem_alloc);
|
|
sk_mem_charge(sk, delta);
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRCVCOALESCE);
|
|
TCP_SKB_CB(to)->end_seq = TCP_SKB_CB(from)->end_seq;
|
|
TCP_SKB_CB(to)->ack_seq = TCP_SKB_CB(from)->ack_seq;
|
|
TCP_SKB_CB(to)->tcp_flags |= TCP_SKB_CB(from)->tcp_flags;
|
|
return true;
|
|
}
|
|
|
|
/* This one checks to see if we can put data from the
|
|
* out_of_order queue into the receive_queue.
|
|
*/
|
|
static void tcp_ofo_queue(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
__u32 dsack_high = tp->rcv_nxt;
|
|
struct sk_buff *skb, *tail;
|
|
bool fragstolen, eaten;
|
|
|
|
while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) {
|
|
if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
|
|
break;
|
|
|
|
if (before(TCP_SKB_CB(skb)->seq, dsack_high)) {
|
|
__u32 dsack = dsack_high;
|
|
if (before(TCP_SKB_CB(skb)->end_seq, dsack_high))
|
|
dsack_high = TCP_SKB_CB(skb)->end_seq;
|
|
tcp_dsack_extend(sk, TCP_SKB_CB(skb)->seq, dsack);
|
|
}
|
|
|
|
__skb_unlink(skb, &tp->out_of_order_queue);
|
|
if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
|
|
SOCK_DEBUG(sk, "ofo packet was already received\n");
|
|
__kfree_skb(skb);
|
|
continue;
|
|
}
|
|
SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n",
|
|
tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
|
|
TCP_SKB_CB(skb)->end_seq);
|
|
|
|
tail = skb_peek_tail(&sk->sk_receive_queue);
|
|
eaten = tail && tcp_try_coalesce(sk, tail, skb, &fragstolen);
|
|
tcp_rcv_nxt_update(tp, TCP_SKB_CB(skb)->end_seq);
|
|
if (!eaten)
|
|
__skb_queue_tail(&sk->sk_receive_queue, skb);
|
|
if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
|
|
tcp_fin(sk);
|
|
if (eaten)
|
|
kfree_skb_partial(skb, fragstolen);
|
|
}
|
|
}
|
|
|
|
static bool tcp_prune_ofo_queue(struct sock *sk);
|
|
static int tcp_prune_queue(struct sock *sk);
|
|
|
|
static int tcp_try_rmem_schedule(struct sock *sk, struct sk_buff *skb,
|
|
unsigned int size)
|
|
{
|
|
if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
|
|
!sk_rmem_schedule(sk, skb, size)) {
|
|
|
|
if (tcp_prune_queue(sk) < 0)
|
|
return -1;
|
|
|
|
if (!sk_rmem_schedule(sk, skb, size)) {
|
|
if (!tcp_prune_ofo_queue(sk))
|
|
return -1;
|
|
|
|
if (!sk_rmem_schedule(sk, skb, size))
|
|
return -1;
|
|
}
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct sk_buff *skb1;
|
|
u32 seq, end_seq;
|
|
|
|
tcp_ecn_check_ce(tp, skb);
|
|
|
|
if (unlikely(tcp_try_rmem_schedule(sk, skb, skb->truesize))) {
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPOFODROP);
|
|
__kfree_skb(skb);
|
|
return;
|
|
}
|
|
|
|
/* Disable header prediction. */
|
|
tp->pred_flags = 0;
|
|
inet_csk_schedule_ack(sk);
|
|
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPOFOQUEUE);
|
|
SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n",
|
|
tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
|
|
|
|
skb1 = skb_peek_tail(&tp->out_of_order_queue);
|
|
if (!skb1) {
|
|
/* Initial out of order segment, build 1 SACK. */
|
|
if (tcp_is_sack(tp)) {
|
|
tp->rx_opt.num_sacks = 1;
|
|
tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq;
|
|
tp->selective_acks[0].end_seq =
|
|
TCP_SKB_CB(skb)->end_seq;
|
|
}
|
|
__skb_queue_head(&tp->out_of_order_queue, skb);
|
|
goto end;
|
|
}
|
|
|
|
seq = TCP_SKB_CB(skb)->seq;
|
|
end_seq = TCP_SKB_CB(skb)->end_seq;
|
|
|
|
if (seq == TCP_SKB_CB(skb1)->end_seq) {
|
|
bool fragstolen;
|
|
|
|
if (!tcp_try_coalesce(sk, skb1, skb, &fragstolen)) {
|
|
__skb_queue_after(&tp->out_of_order_queue, skb1, skb);
|
|
} else {
|
|
tcp_grow_window(sk, skb);
|
|
kfree_skb_partial(skb, fragstolen);
|
|
skb = NULL;
|
|
}
|
|
|
|
if (!tp->rx_opt.num_sacks ||
|
|
tp->selective_acks[0].end_seq != seq)
|
|
goto add_sack;
|
|
|
|
/* Common case: data arrive in order after hole. */
|
|
tp->selective_acks[0].end_seq = end_seq;
|
|
goto end;
|
|
}
|
|
|
|
/* Find place to insert this segment. */
|
|
while (1) {
|
|
if (!after(TCP_SKB_CB(skb1)->seq, seq))
|
|
break;
|
|
if (skb_queue_is_first(&tp->out_of_order_queue, skb1)) {
|
|
skb1 = NULL;
|
|
break;
|
|
}
|
|
skb1 = skb_queue_prev(&tp->out_of_order_queue, skb1);
|
|
}
|
|
|
|
/* Do skb overlap to previous one? */
|
|
if (skb1 && before(seq, TCP_SKB_CB(skb1)->end_seq)) {
|
|
if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
|
|
/* All the bits are present. Drop. */
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPOFOMERGE);
|
|
__kfree_skb(skb);
|
|
skb = NULL;
|
|
tcp_dsack_set(sk, seq, end_seq);
|
|
goto add_sack;
|
|
}
|
|
if (after(seq, TCP_SKB_CB(skb1)->seq)) {
|
|
/* Partial overlap. */
|
|
tcp_dsack_set(sk, seq,
|
|
TCP_SKB_CB(skb1)->end_seq);
|
|
} else {
|
|
if (skb_queue_is_first(&tp->out_of_order_queue,
|
|
skb1))
|
|
skb1 = NULL;
|
|
else
|
|
skb1 = skb_queue_prev(
|
|
&tp->out_of_order_queue,
|
|
skb1);
|
|
}
|
|
}
|
|
if (!skb1)
|
|
__skb_queue_head(&tp->out_of_order_queue, skb);
|
|
else
|
|
__skb_queue_after(&tp->out_of_order_queue, skb1, skb);
|
|
|
|
/* And clean segments covered by new one as whole. */
|
|
while (!skb_queue_is_last(&tp->out_of_order_queue, skb)) {
|
|
skb1 = skb_queue_next(&tp->out_of_order_queue, skb);
|
|
|
|
if (!after(end_seq, TCP_SKB_CB(skb1)->seq))
|
|
break;
|
|
if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
|
|
tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq,
|
|
end_seq);
|
|
break;
|
|
}
|
|
__skb_unlink(skb1, &tp->out_of_order_queue);
|
|
tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq,
|
|
TCP_SKB_CB(skb1)->end_seq);
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPOFOMERGE);
|
|
__kfree_skb(skb1);
|
|
}
|
|
|
|
add_sack:
|
|
if (tcp_is_sack(tp))
|
|
tcp_sack_new_ofo_skb(sk, seq, end_seq);
|
|
end:
|
|
if (skb) {
|
|
tcp_grow_window(sk, skb);
|
|
skb_set_owner_r(skb, sk);
|
|
}
|
|
}
|
|
|
|
static int __must_check tcp_queue_rcv(struct sock *sk, struct sk_buff *skb, int hdrlen,
|
|
bool *fragstolen)
|
|
{
|
|
int eaten;
|
|
struct sk_buff *tail = skb_peek_tail(&sk->sk_receive_queue);
|
|
|
|
__skb_pull(skb, hdrlen);
|
|
eaten = (tail &&
|
|
tcp_try_coalesce(sk, tail, skb, fragstolen)) ? 1 : 0;
|
|
tcp_rcv_nxt_update(tcp_sk(sk), TCP_SKB_CB(skb)->end_seq);
|
|
if (!eaten) {
|
|
__skb_queue_tail(&sk->sk_receive_queue, skb);
|
|
skb_set_owner_r(skb, sk);
|
|
}
|
|
return eaten;
|
|
}
|
|
|
|
int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size)
|
|
{
|
|
struct sk_buff *skb;
|
|
bool fragstolen;
|
|
|
|
if (size == 0)
|
|
return 0;
|
|
|
|
skb = alloc_skb(size, sk->sk_allocation);
|
|
if (!skb)
|
|
goto err;
|
|
|
|
if (tcp_try_rmem_schedule(sk, skb, skb->truesize))
|
|
goto err_free;
|
|
|
|
if (memcpy_from_msg(skb_put(skb, size), msg, size))
|
|
goto err_free;
|
|
|
|
TCP_SKB_CB(skb)->seq = tcp_sk(sk)->rcv_nxt;
|
|
TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq + size;
|
|
TCP_SKB_CB(skb)->ack_seq = tcp_sk(sk)->snd_una - 1;
|
|
|
|
if (tcp_queue_rcv(sk, skb, 0, &fragstolen)) {
|
|
WARN_ON_ONCE(fragstolen); /* should not happen */
|
|
__kfree_skb(skb);
|
|
}
|
|
return size;
|
|
|
|
err_free:
|
|
kfree_skb(skb);
|
|
err:
|
|
return -ENOMEM;
|
|
}
|
|
|
|
static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
int eaten = -1;
|
|
bool fragstolen = false;
|
|
|
|
if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq)
|
|
goto drop;
|
|
|
|
skb_dst_drop(skb);
|
|
__skb_pull(skb, tcp_hdr(skb)->doff * 4);
|
|
|
|
tcp_ecn_accept_cwr(tp, skb);
|
|
|
|
tp->rx_opt.dsack = 0;
|
|
|
|
/* Queue data for delivery to the user.
|
|
* Packets in sequence go to the receive queue.
|
|
* Out of sequence packets to the out_of_order_queue.
|
|
*/
|
|
if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
|
|
if (tcp_receive_window(tp) == 0)
|
|
goto out_of_window;
|
|
|
|
/* Ok. In sequence. In window. */
|
|
if (tp->ucopy.task == current &&
|
|
tp->copied_seq == tp->rcv_nxt && tp->ucopy.len &&
|
|
sock_owned_by_user(sk) && !tp->urg_data) {
|
|
int chunk = min_t(unsigned int, skb->len,
|
|
tp->ucopy.len);
|
|
|
|
__set_current_state(TASK_RUNNING);
|
|
|
|
local_bh_enable();
|
|
if (!skb_copy_datagram_msg(skb, 0, tp->ucopy.msg, chunk)) {
|
|
tp->ucopy.len -= chunk;
|
|
tp->copied_seq += chunk;
|
|
eaten = (chunk == skb->len);
|
|
tcp_rcv_space_adjust(sk);
|
|
}
|
|
local_bh_disable();
|
|
}
|
|
|
|
if (eaten <= 0) {
|
|
queue_and_out:
|
|
if (eaten < 0) {
|
|
if (skb_queue_len(&sk->sk_receive_queue) == 0)
|
|
sk_forced_mem_schedule(sk, skb->truesize);
|
|
else if (tcp_try_rmem_schedule(sk, skb, skb->truesize))
|
|
goto drop;
|
|
}
|
|
eaten = tcp_queue_rcv(sk, skb, 0, &fragstolen);
|
|
}
|
|
tcp_rcv_nxt_update(tp, TCP_SKB_CB(skb)->end_seq);
|
|
if (skb->len)
|
|
tcp_event_data_recv(sk, skb);
|
|
if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
|
|
tcp_fin(sk);
|
|
|
|
if (!skb_queue_empty(&tp->out_of_order_queue)) {
|
|
tcp_ofo_queue(sk);
|
|
|
|
/* RFC2581. 4.2. SHOULD send immediate ACK, when
|
|
* gap in queue is filled.
|
|
*/
|
|
if (skb_queue_empty(&tp->out_of_order_queue))
|
|
inet_csk(sk)->icsk_ack.pingpong = 0;
|
|
}
|
|
|
|
if (tp->rx_opt.num_sacks)
|
|
tcp_sack_remove(tp);
|
|
|
|
tcp_fast_path_check(sk);
|
|
|
|
if (eaten > 0)
|
|
kfree_skb_partial(skb, fragstolen);
|
|
if (!sock_flag(sk, SOCK_DEAD))
|
|
sk->sk_data_ready(sk);
|
|
return;
|
|
}
|
|
|
|
if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
|
|
/* A retransmit, 2nd most common case. Force an immediate ack. */
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOST);
|
|
tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
|
|
|
|
out_of_window:
|
|
tcp_enter_quickack_mode(sk);
|
|
inet_csk_schedule_ack(sk);
|
|
drop:
|
|
__kfree_skb(skb);
|
|
return;
|
|
}
|
|
|
|
/* Out of window. F.e. zero window probe. */
|
|
if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp)))
|
|
goto out_of_window;
|
|
|
|
tcp_enter_quickack_mode(sk);
|
|
|
|
if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
|
|
/* Partial packet, seq < rcv_next < end_seq */
|
|
SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n",
|
|
tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
|
|
TCP_SKB_CB(skb)->end_seq);
|
|
|
|
tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, tp->rcv_nxt);
|
|
|
|
/* If window is closed, drop tail of packet. But after
|
|
* remembering D-SACK for its head made in previous line.
|
|
*/
|
|
if (!tcp_receive_window(tp))
|
|
goto out_of_window;
|
|
goto queue_and_out;
|
|
}
|
|
|
|
tcp_data_queue_ofo(sk, skb);
|
|
}
|
|
|
|
static struct sk_buff *tcp_collapse_one(struct sock *sk, struct sk_buff *skb,
|
|
struct sk_buff_head *list)
|
|
{
|
|
struct sk_buff *next = NULL;
|
|
|
|
if (!skb_queue_is_last(list, skb))
|
|
next = skb_queue_next(list, skb);
|
|
|
|
__skb_unlink(skb, list);
|
|
__kfree_skb(skb);
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRCVCOLLAPSED);
|
|
|
|
return next;
|
|
}
|
|
|
|
/* Collapse contiguous sequence of skbs head..tail with
|
|
* sequence numbers start..end.
|
|
*
|
|
* If tail is NULL, this means until the end of the list.
|
|
*
|
|
* Segments with FIN/SYN are not collapsed (only because this
|
|
* simplifies code)
|
|
*/
|
|
static void
|
|
tcp_collapse(struct sock *sk, struct sk_buff_head *list,
|
|
struct sk_buff *head, struct sk_buff *tail,
|
|
u32 start, u32 end)
|
|
{
|
|
struct sk_buff *skb, *n;
|
|
bool end_of_skbs;
|
|
|
|
/* First, check that queue is collapsible and find
|
|
* the point where collapsing can be useful. */
|
|
skb = head;
|
|
restart:
|
|
end_of_skbs = true;
|
|
skb_queue_walk_from_safe(list, skb, n) {
|
|
if (skb == tail)
|
|
break;
|
|
/* No new bits? It is possible on ofo queue. */
|
|
if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
|
|
skb = tcp_collapse_one(sk, skb, list);
|
|
if (!skb)
|
|
break;
|
|
goto restart;
|
|
}
|
|
|
|
/* The first skb to collapse is:
|
|
* - not SYN/FIN and
|
|
* - bloated or contains data before "start" or
|
|
* overlaps to the next one.
|
|
*/
|
|
if (!(TCP_SKB_CB(skb)->tcp_flags & (TCPHDR_SYN | TCPHDR_FIN)) &&
|
|
(tcp_win_from_space(skb->truesize) > skb->len ||
|
|
before(TCP_SKB_CB(skb)->seq, start))) {
|
|
end_of_skbs = false;
|
|
break;
|
|
}
|
|
|
|
if (!skb_queue_is_last(list, skb)) {
|
|
struct sk_buff *next = skb_queue_next(list, skb);
|
|
if (next != tail &&
|
|
TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(next)->seq) {
|
|
end_of_skbs = false;
|
|
break;
|
|
}
|
|
}
|
|
|
|
/* Decided to skip this, advance start seq. */
|
|
start = TCP_SKB_CB(skb)->end_seq;
|
|
}
|
|
if (end_of_skbs ||
|
|
(TCP_SKB_CB(skb)->tcp_flags & (TCPHDR_SYN | TCPHDR_FIN)))
|
|
return;
|
|
|
|
while (before(start, end)) {
|
|
int copy = min_t(int, SKB_MAX_ORDER(0, 0), end - start);
|
|
struct sk_buff *nskb;
|
|
|
|
nskb = alloc_skb(copy, GFP_ATOMIC);
|
|
if (!nskb)
|
|
return;
|
|
|
|
memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
|
|
TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start;
|
|
__skb_queue_before(list, skb, nskb);
|
|
skb_set_owner_r(nskb, sk);
|
|
|
|
/* Copy data, releasing collapsed skbs. */
|
|
while (copy > 0) {
|
|
int offset = start - TCP_SKB_CB(skb)->seq;
|
|
int size = TCP_SKB_CB(skb)->end_seq - start;
|
|
|
|
BUG_ON(offset < 0);
|
|
if (size > 0) {
|
|
size = min(copy, size);
|
|
if (skb_copy_bits(skb, offset, skb_put(nskb, size), size))
|
|
BUG();
|
|
TCP_SKB_CB(nskb)->end_seq += size;
|
|
copy -= size;
|
|
start += size;
|
|
}
|
|
if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
|
|
skb = tcp_collapse_one(sk, skb, list);
|
|
if (!skb ||
|
|
skb == tail ||
|
|
(TCP_SKB_CB(skb)->tcp_flags & (TCPHDR_SYN | TCPHDR_FIN)))
|
|
return;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
|
|
* and tcp_collapse() them until all the queue is collapsed.
|
|
*/
|
|
static void tcp_collapse_ofo_queue(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct sk_buff *skb = skb_peek(&tp->out_of_order_queue);
|
|
struct sk_buff *head;
|
|
u32 start, end;
|
|
|
|
if (!skb)
|
|
return;
|
|
|
|
start = TCP_SKB_CB(skb)->seq;
|
|
end = TCP_SKB_CB(skb)->end_seq;
|
|
head = skb;
|
|
|
|
for (;;) {
|
|
struct sk_buff *next = NULL;
|
|
|
|
if (!skb_queue_is_last(&tp->out_of_order_queue, skb))
|
|
next = skb_queue_next(&tp->out_of_order_queue, skb);
|
|
skb = next;
|
|
|
|
/* Segment is terminated when we see gap or when
|
|
* we are at the end of all the queue. */
|
|
if (!skb ||
|
|
after(TCP_SKB_CB(skb)->seq, end) ||
|
|
before(TCP_SKB_CB(skb)->end_seq, start)) {
|
|
tcp_collapse(sk, &tp->out_of_order_queue,
|
|
head, skb, start, end);
|
|
head = skb;
|
|
if (!skb)
|
|
break;
|
|
/* Start new segment */
|
|
start = TCP_SKB_CB(skb)->seq;
|
|
end = TCP_SKB_CB(skb)->end_seq;
|
|
} else {
|
|
if (before(TCP_SKB_CB(skb)->seq, start))
|
|
start = TCP_SKB_CB(skb)->seq;
|
|
if (after(TCP_SKB_CB(skb)->end_seq, end))
|
|
end = TCP_SKB_CB(skb)->end_seq;
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Purge the out-of-order queue.
|
|
* Return true if queue was pruned.
|
|
*/
|
|
static bool tcp_prune_ofo_queue(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
bool res = false;
|
|
|
|
if (!skb_queue_empty(&tp->out_of_order_queue)) {
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_OFOPRUNED);
|
|
__skb_queue_purge(&tp->out_of_order_queue);
|
|
|
|
/* Reset SACK state. A conforming SACK implementation will
|
|
* do the same at a timeout based retransmit. When a connection
|
|
* is in a sad state like this, we care only about integrity
|
|
* of the connection not performance.
|
|
*/
|
|
if (tp->rx_opt.sack_ok)
|
|
tcp_sack_reset(&tp->rx_opt);
|
|
sk_mem_reclaim(sk);
|
|
res = true;
|
|
}
|
|
return res;
|
|
}
|
|
|
|
/* Reduce allocated memory if we can, trying to get
|
|
* the socket within its memory limits again.
|
|
*
|
|
* Return less than zero if we should start dropping frames
|
|
* until the socket owning process reads some of the data
|
|
* to stabilize the situation.
|
|
*/
|
|
static int tcp_prune_queue(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq);
|
|
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PRUNECALLED);
|
|
|
|
if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf)
|
|
tcp_clamp_window(sk);
|
|
else if (tcp_under_memory_pressure(sk))
|
|
tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss);
|
|
|
|
tcp_collapse_ofo_queue(sk);
|
|
if (!skb_queue_empty(&sk->sk_receive_queue))
|
|
tcp_collapse(sk, &sk->sk_receive_queue,
|
|
skb_peek(&sk->sk_receive_queue),
|
|
NULL,
|
|
tp->copied_seq, tp->rcv_nxt);
|
|
sk_mem_reclaim(sk);
|
|
|
|
if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
|
|
return 0;
|
|
|
|
/* Collapsing did not help, destructive actions follow.
|
|
* This must not ever occur. */
|
|
|
|
tcp_prune_ofo_queue(sk);
|
|
|
|
if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
|
|
return 0;
|
|
|
|
/* If we are really being abused, tell the caller to silently
|
|
* drop receive data on the floor. It will get retransmitted
|
|
* and hopefully then we'll have sufficient space.
|
|
*/
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_RCVPRUNED);
|
|
|
|
/* Massive buffer overcommit. */
|
|
tp->pred_flags = 0;
|
|
return -1;
|
|
}
|
|
|
|
static bool tcp_should_expand_sndbuf(const struct sock *sk)
|
|
{
|
|
const struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
/* If the user specified a specific send buffer setting, do
|
|
* not modify it.
|
|
*/
|
|
if (sk->sk_userlocks & SOCK_SNDBUF_LOCK)
|
|
return false;
|
|
|
|
/* If we are under global TCP memory pressure, do not expand. */
|
|
if (tcp_under_memory_pressure(sk))
|
|
return false;
|
|
|
|
/* If we are under soft global TCP memory pressure, do not expand. */
|
|
if (sk_memory_allocated(sk) >= sk_prot_mem_limits(sk, 0))
|
|
return false;
|
|
|
|
/* If we filled the congestion window, do not expand. */
|
|
if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
/* When incoming ACK allowed to free some skb from write_queue,
|
|
* we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
|
|
* on the exit from tcp input handler.
|
|
*
|
|
* PROBLEM: sndbuf expansion does not work well with largesend.
|
|
*/
|
|
static void tcp_new_space(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
if (tcp_should_expand_sndbuf(sk)) {
|
|
tcp_sndbuf_expand(sk);
|
|
tp->snd_cwnd_stamp = tcp_time_stamp;
|
|
}
|
|
|
|
sk->sk_write_space(sk);
|
|
}
|
|
|
|
static void tcp_check_space(struct sock *sk)
|
|
{
|
|
if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) {
|
|
sock_reset_flag(sk, SOCK_QUEUE_SHRUNK);
|
|
/* pairs with tcp_poll() */
|
|
smp_mb__after_atomic();
|
|
if (sk->sk_socket &&
|
|
test_bit(SOCK_NOSPACE, &sk->sk_socket->flags))
|
|
tcp_new_space(sk);
|
|
}
|
|
}
|
|
|
|
static inline void tcp_data_snd_check(struct sock *sk)
|
|
{
|
|
tcp_push_pending_frames(sk);
|
|
tcp_check_space(sk);
|
|
}
|
|
|
|
/*
|
|
* Check if sending an ack is needed.
|
|
*/
|
|
static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
/* More than one full frame received... */
|
|
if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss &&
|
|
/* ... and right edge of window advances far enough.
|
|
* (tcp_recvmsg() will send ACK otherwise). Or...
|
|
*/
|
|
__tcp_select_window(sk) >= tp->rcv_wnd) ||
|
|
/* We ACK each frame or... */
|
|
tcp_in_quickack_mode(sk) ||
|
|
/* We have out of order data. */
|
|
(ofo_possible && skb_peek(&tp->out_of_order_queue))) {
|
|
/* Then ack it now */
|
|
tcp_send_ack(sk);
|
|
} else {
|
|
/* Else, send delayed ack. */
|
|
tcp_send_delayed_ack(sk);
|
|
}
|
|
}
|
|
|
|
static inline void tcp_ack_snd_check(struct sock *sk)
|
|
{
|
|
if (!inet_csk_ack_scheduled(sk)) {
|
|
/* We sent a data segment already. */
|
|
return;
|
|
}
|
|
__tcp_ack_snd_check(sk, 1);
|
|
}
|
|
|
|
/*
|
|
* This routine is only called when we have urgent data
|
|
* signaled. Its the 'slow' part of tcp_urg. It could be
|
|
* moved inline now as tcp_urg is only called from one
|
|
* place. We handle URGent data wrong. We have to - as
|
|
* BSD still doesn't use the correction from RFC961.
|
|
* For 1003.1g we should support a new option TCP_STDURG to permit
|
|
* either form (or just set the sysctl tcp_stdurg).
|
|
*/
|
|
|
|
static void tcp_check_urg(struct sock *sk, const struct tcphdr *th)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
u32 ptr = ntohs(th->urg_ptr);
|
|
|
|
if (ptr && !sysctl_tcp_stdurg)
|
|
ptr--;
|
|
ptr += ntohl(th->seq);
|
|
|
|
/* Ignore urgent data that we've already seen and read. */
|
|
if (after(tp->copied_seq, ptr))
|
|
return;
|
|
|
|
/* Do not replay urg ptr.
|
|
*
|
|
* NOTE: interesting situation not covered by specs.
|
|
* Misbehaving sender may send urg ptr, pointing to segment,
|
|
* which we already have in ofo queue. We are not able to fetch
|
|
* such data and will stay in TCP_URG_NOTYET until will be eaten
|
|
* by recvmsg(). Seems, we are not obliged to handle such wicked
|
|
* situations. But it is worth to think about possibility of some
|
|
* DoSes using some hypothetical application level deadlock.
|
|
*/
|
|
if (before(ptr, tp->rcv_nxt))
|
|
return;
|
|
|
|
/* Do we already have a newer (or duplicate) urgent pointer? */
|
|
if (tp->urg_data && !after(ptr, tp->urg_seq))
|
|
return;
|
|
|
|
/* Tell the world about our new urgent pointer. */
|
|
sk_send_sigurg(sk);
|
|
|
|
/* We may be adding urgent data when the last byte read was
|
|
* urgent. To do this requires some care. We cannot just ignore
|
|
* tp->copied_seq since we would read the last urgent byte again
|
|
* as data, nor can we alter copied_seq until this data arrives
|
|
* or we break the semantics of SIOCATMARK (and thus sockatmark())
|
|
*
|
|
* NOTE. Double Dutch. Rendering to plain English: author of comment
|
|
* above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
|
|
* and expect that both A and B disappear from stream. This is _wrong_.
|
|
* Though this happens in BSD with high probability, this is occasional.
|
|
* Any application relying on this is buggy. Note also, that fix "works"
|
|
* only in this artificial test. Insert some normal data between A and B and we will
|
|
* decline of BSD again. Verdict: it is better to remove to trap
|
|
* buggy users.
|
|
*/
|
|
if (tp->urg_seq == tp->copied_seq && tp->urg_data &&
|
|
!sock_flag(sk, SOCK_URGINLINE) && tp->copied_seq != tp->rcv_nxt) {
|
|
struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);
|
|
tp->copied_seq++;
|
|
if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) {
|
|
__skb_unlink(skb, &sk->sk_receive_queue);
|
|
__kfree_skb(skb);
|
|
}
|
|
}
|
|
|
|
tp->urg_data = TCP_URG_NOTYET;
|
|
tp->urg_seq = ptr;
|
|
|
|
/* Disable header prediction. */
|
|
tp->pred_flags = 0;
|
|
}
|
|
|
|
/* This is the 'fast' part of urgent handling. */
|
|
static void tcp_urg(struct sock *sk, struct sk_buff *skb, const struct tcphdr *th)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
/* Check if we get a new urgent pointer - normally not. */
|
|
if (th->urg)
|
|
tcp_check_urg(sk, th);
|
|
|
|
/* Do we wait for any urgent data? - normally not... */
|
|
if (tp->urg_data == TCP_URG_NOTYET) {
|
|
u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) -
|
|
th->syn;
|
|
|
|
/* Is the urgent pointer pointing into this packet? */
|
|
if (ptr < skb->len) {
|
|
u8 tmp;
|
|
if (skb_copy_bits(skb, ptr, &tmp, 1))
|
|
BUG();
|
|
tp->urg_data = TCP_URG_VALID | tmp;
|
|
if (!sock_flag(sk, SOCK_DEAD))
|
|
sk->sk_data_ready(sk);
|
|
}
|
|
}
|
|
}
|
|
|
|
static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
int chunk = skb->len - hlen;
|
|
int err;
|
|
|
|
local_bh_enable();
|
|
if (skb_csum_unnecessary(skb))
|
|
err = skb_copy_datagram_msg(skb, hlen, tp->ucopy.msg, chunk);
|
|
else
|
|
err = skb_copy_and_csum_datagram_msg(skb, hlen, tp->ucopy.msg);
|
|
|
|
if (!err) {
|
|
tp->ucopy.len -= chunk;
|
|
tp->copied_seq += chunk;
|
|
tcp_rcv_space_adjust(sk);
|
|
}
|
|
|
|
local_bh_disable();
|
|
return err;
|
|
}
|
|
|
|
static __sum16 __tcp_checksum_complete_user(struct sock *sk,
|
|
struct sk_buff *skb)
|
|
{
|
|
__sum16 result;
|
|
|
|
if (sock_owned_by_user(sk)) {
|
|
local_bh_enable();
|
|
result = __tcp_checksum_complete(skb);
|
|
local_bh_disable();
|
|
} else {
|
|
result = __tcp_checksum_complete(skb);
|
|
}
|
|
return result;
|
|
}
|
|
|
|
static inline bool tcp_checksum_complete_user(struct sock *sk,
|
|
struct sk_buff *skb)
|
|
{
|
|
return !skb_csum_unnecessary(skb) &&
|
|
__tcp_checksum_complete_user(sk, skb);
|
|
}
|
|
|
|
/* Does PAWS and seqno based validation of an incoming segment, flags will
|
|
* play significant role here.
|
|
*/
|
|
static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
|
|
const struct tcphdr *th, int syn_inerr)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
/* RFC1323: H1. Apply PAWS check first. */
|
|
if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
|
|
tcp_paws_discard(sk, skb)) {
|
|
if (!th->rst) {
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED);
|
|
if (!tcp_oow_rate_limited(sock_net(sk), skb,
|
|
LINUX_MIB_TCPACKSKIPPEDPAWS,
|
|
&tp->last_oow_ack_time))
|
|
tcp_send_dupack(sk, skb);
|
|
goto discard;
|
|
}
|
|
/* Reset is accepted even if it did not pass PAWS. */
|
|
}
|
|
|
|
/* Step 1: check sequence number */
|
|
if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
|
|
/* RFC793, page 37: "In all states except SYN-SENT, all reset
|
|
* (RST) segments are validated by checking their SEQ-fields."
|
|
* And page 69: "If an incoming segment is not acceptable,
|
|
* an acknowledgment should be sent in reply (unless the RST
|
|
* bit is set, if so drop the segment and return)".
|
|
*/
|
|
if (!th->rst) {
|
|
if (th->syn)
|
|
goto syn_challenge;
|
|
if (!tcp_oow_rate_limited(sock_net(sk), skb,
|
|
LINUX_MIB_TCPACKSKIPPEDSEQ,
|
|
&tp->last_oow_ack_time))
|
|
tcp_send_dupack(sk, skb);
|
|
}
|
|
goto discard;
|
|
}
|
|
|
|
/* Step 2: check RST bit */
|
|
if (th->rst) {
|
|
/* RFC 5961 3.2 :
|
|
* If sequence number exactly matches RCV.NXT, then
|
|
* RESET the connection
|
|
* else
|
|
* Send a challenge ACK
|
|
*/
|
|
if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt)
|
|
tcp_reset(sk);
|
|
else
|
|
tcp_send_challenge_ack(sk, skb);
|
|
goto discard;
|
|
}
|
|
|
|
/* step 3: check security and precedence [ignored] */
|
|
|
|
/* step 4: Check for a SYN
|
|
* RFC 5961 4.2 : Send a challenge ack
|
|
*/
|
|
if (th->syn) {
|
|
syn_challenge:
|
|
if (syn_inerr)
|
|
TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSYNCHALLENGE);
|
|
tcp_send_challenge_ack(sk, skb);
|
|
goto discard;
|
|
}
|
|
|
|
return true;
|
|
|
|
discard:
|
|
__kfree_skb(skb);
|
|
return false;
|
|
}
|
|
|
|
/*
|
|
* TCP receive function for the ESTABLISHED state.
|
|
*
|
|
* It is split into a fast path and a slow path. The fast path is
|
|
* disabled when:
|
|
* - A zero window was announced from us - zero window probing
|
|
* is only handled properly in the slow path.
|
|
* - Out of order segments arrived.
|
|
* - Urgent data is expected.
|
|
* - There is no buffer space left
|
|
* - Unexpected TCP flags/window values/header lengths are received
|
|
* (detected by checking the TCP header against pred_flags)
|
|
* - Data is sent in both directions. Fast path only supports pure senders
|
|
* or pure receivers (this means either the sequence number or the ack
|
|
* value must stay constant)
|
|
* - Unexpected TCP option.
|
|
*
|
|
* When these conditions are not satisfied it drops into a standard
|
|
* receive procedure patterned after RFC793 to handle all cases.
|
|
* The first three cases are guaranteed by proper pred_flags setting,
|
|
* the rest is checked inline. Fast processing is turned on in
|
|
* tcp_data_queue when everything is OK.
|
|
*/
|
|
void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
|
|
const struct tcphdr *th, unsigned int len)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
if (unlikely(!sk->sk_rx_dst))
|
|
inet_csk(sk)->icsk_af_ops->sk_rx_dst_set(sk, skb);
|
|
/*
|
|
* Header prediction.
|
|
* The code loosely follows the one in the famous
|
|
* "30 instruction TCP receive" Van Jacobson mail.
|
|
*
|
|
* Van's trick is to deposit buffers into socket queue
|
|
* on a device interrupt, to call tcp_recv function
|
|
* on the receive process context and checksum and copy
|
|
* the buffer to user space. smart...
|
|
*
|
|
* Our current scheme is not silly either but we take the
|
|
* extra cost of the net_bh soft interrupt processing...
|
|
* We do checksum and copy also but from device to kernel.
|
|
*/
|
|
|
|
tp->rx_opt.saw_tstamp = 0;
|
|
|
|
/* pred_flags is 0xS?10 << 16 + snd_wnd
|
|
* if header_prediction is to be made
|
|
* 'S' will always be tp->tcp_header_len >> 2
|
|
* '?' will be 0 for the fast path, otherwise pred_flags is 0 to
|
|
* turn it off (when there are holes in the receive
|
|
* space for instance)
|
|
* PSH flag is ignored.
|
|
*/
|
|
|
|
if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags &&
|
|
TCP_SKB_CB(skb)->seq == tp->rcv_nxt &&
|
|
!after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt)) {
|
|
int tcp_header_len = tp->tcp_header_len;
|
|
|
|
/* Timestamp header prediction: tcp_header_len
|
|
* is automatically equal to th->doff*4 due to pred_flags
|
|
* match.
|
|
*/
|
|
|
|
/* Check timestamp */
|
|
if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) {
|
|
/* No? Slow path! */
|
|
if (!tcp_parse_aligned_timestamp(tp, th))
|
|
goto slow_path;
|
|
|
|
/* If PAWS failed, check it more carefully in slow path */
|
|
if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0)
|
|
goto slow_path;
|
|
|
|
/* DO NOT update ts_recent here, if checksum fails
|
|
* and timestamp was corrupted part, it will result
|
|
* in a hung connection since we will drop all
|
|
* future packets due to the PAWS test.
|
|
*/
|
|
}
|
|
|
|
if (len <= tcp_header_len) {
|
|
/* Bulk data transfer: sender */
|
|
if (len == tcp_header_len) {
|
|
/* Predicted packet is in window by definition.
|
|
* seq == rcv_nxt and rcv_wup <= rcv_nxt.
|
|
* Hence, check seq<=rcv_wup reduces to:
|
|
*/
|
|
if (tcp_header_len ==
|
|
(sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
|
|
tp->rcv_nxt == tp->rcv_wup)
|
|
tcp_store_ts_recent(tp);
|
|
|
|
/* We know that such packets are checksummed
|
|
* on entry.
|
|
*/
|
|
tcp_ack(sk, skb, 0);
|
|
__kfree_skb(skb);
|
|
tcp_data_snd_check(sk);
|
|
return;
|
|
} else { /* Header too small */
|
|
TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
|
|
goto discard;
|
|
}
|
|
} else {
|
|
int eaten = 0;
|
|
bool fragstolen = false;
|
|
|
|
if (tp->ucopy.task == current &&
|
|
tp->copied_seq == tp->rcv_nxt &&
|
|
len - tcp_header_len <= tp->ucopy.len &&
|
|
sock_owned_by_user(sk)) {
|
|
__set_current_state(TASK_RUNNING);
|
|
|
|
if (!tcp_copy_to_iovec(sk, skb, tcp_header_len)) {
|
|
/* Predicted packet is in window by definition.
|
|
* seq == rcv_nxt and rcv_wup <= rcv_nxt.
|
|
* Hence, check seq<=rcv_wup reduces to:
|
|
*/
|
|
if (tcp_header_len ==
|
|
(sizeof(struct tcphdr) +
|
|
TCPOLEN_TSTAMP_ALIGNED) &&
|
|
tp->rcv_nxt == tp->rcv_wup)
|
|
tcp_store_ts_recent(tp);
|
|
|
|
tcp_rcv_rtt_measure_ts(sk, skb);
|
|
|
|
__skb_pull(skb, tcp_header_len);
|
|
tcp_rcv_nxt_update(tp, TCP_SKB_CB(skb)->end_seq);
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPHITSTOUSER);
|
|
eaten = 1;
|
|
}
|
|
}
|
|
if (!eaten) {
|
|
if (tcp_checksum_complete_user(sk, skb))
|
|
goto csum_error;
|
|
|
|
if ((int)skb->truesize > sk->sk_forward_alloc)
|
|
goto step5;
|
|
|
|
/* Predicted packet is in window by definition.
|
|
* seq == rcv_nxt and rcv_wup <= rcv_nxt.
|
|
* Hence, check seq<=rcv_wup reduces to:
|
|
*/
|
|
if (tcp_header_len ==
|
|
(sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
|
|
tp->rcv_nxt == tp->rcv_wup)
|
|
tcp_store_ts_recent(tp);
|
|
|
|
tcp_rcv_rtt_measure_ts(sk, skb);
|
|
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPHITS);
|
|
|
|
/* Bulk data transfer: receiver */
|
|
eaten = tcp_queue_rcv(sk, skb, tcp_header_len,
|
|
&fragstolen);
|
|
}
|
|
|
|
tcp_event_data_recv(sk, skb);
|
|
|
|
if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) {
|
|
/* Well, only one small jumplet in fast path... */
|
|
tcp_ack(sk, skb, FLAG_DATA);
|
|
tcp_data_snd_check(sk);
|
|
if (!inet_csk_ack_scheduled(sk))
|
|
goto no_ack;
|
|
}
|
|
|
|
__tcp_ack_snd_check(sk, 0);
|
|
no_ack:
|
|
if (eaten)
|
|
kfree_skb_partial(skb, fragstolen);
|
|
sk->sk_data_ready(sk);
|
|
return;
|
|
}
|
|
}
|
|
|
|
slow_path:
|
|
if (len < (th->doff << 2) || tcp_checksum_complete_user(sk, skb))
|
|
goto csum_error;
|
|
|
|
if (!th->ack && !th->rst && !th->syn)
|
|
goto discard;
|
|
|
|
/*
|
|
* Standard slow path.
|
|
*/
|
|
|
|
if (!tcp_validate_incoming(sk, skb, th, 1))
|
|
return;
|
|
|
|
step5:
|
|
if (tcp_ack(sk, skb, FLAG_SLOWPATH | FLAG_UPDATE_TS_RECENT) < 0)
|
|
goto discard;
|
|
|
|
tcp_rcv_rtt_measure_ts(sk, skb);
|
|
|
|
/* Process urgent data. */
|
|
tcp_urg(sk, skb, th);
|
|
|
|
/* step 7: process the segment text */
|
|
tcp_data_queue(sk, skb);
|
|
|
|
tcp_data_snd_check(sk);
|
|
tcp_ack_snd_check(sk);
|
|
return;
|
|
|
|
csum_error:
|
|
TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_CSUMERRORS);
|
|
TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
|
|
|
|
discard:
|
|
__kfree_skb(skb);
|
|
}
|
|
EXPORT_SYMBOL(tcp_rcv_established);
|
|
|
|
void tcp_finish_connect(struct sock *sk, struct sk_buff *skb)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct inet_connection_sock *icsk = inet_csk(sk);
|
|
|
|
tcp_set_state(sk, TCP_ESTABLISHED);
|
|
|
|
if (skb) {
|
|
icsk->icsk_af_ops->sk_rx_dst_set(sk, skb);
|
|
security_inet_conn_established(sk, skb);
|
|
}
|
|
|
|
/* Make sure socket is routed, for correct metrics. */
|
|
icsk->icsk_af_ops->rebuild_header(sk);
|
|
|
|
tcp_init_metrics(sk);
|
|
|
|
tcp_init_congestion_control(sk);
|
|
|
|
/* Prevent spurious tcp_cwnd_restart() on first data
|
|
* packet.
|
|
*/
|
|
tp->lsndtime = tcp_time_stamp;
|
|
|
|
tcp_init_buffer_space(sk);
|
|
|
|
if (sock_flag(sk, SOCK_KEEPOPEN))
|
|
inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp));
|
|
|
|
if (!tp->rx_opt.snd_wscale)
|
|
__tcp_fast_path_on(tp, tp->snd_wnd);
|
|
else
|
|
tp->pred_flags = 0;
|
|
|
|
if (!sock_flag(sk, SOCK_DEAD)) {
|
|
sk->sk_state_change(sk);
|
|
sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
|
|
}
|
|
}
|
|
|
|
static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,
|
|
struct tcp_fastopen_cookie *cookie)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct sk_buff *data = tp->syn_data ? tcp_write_queue_head(sk) : NULL;
|
|
u16 mss = tp->rx_opt.mss_clamp, try_exp = 0;
|
|
bool syn_drop = false;
|
|
|
|
if (mss == tp->rx_opt.user_mss) {
|
|
struct tcp_options_received opt;
|
|
|
|
/* Get original SYNACK MSS value if user MSS sets mss_clamp */
|
|
tcp_clear_options(&opt);
|
|
opt.user_mss = opt.mss_clamp = 0;
|
|
tcp_parse_options(synack, &opt, 0, NULL);
|
|
mss = opt.mss_clamp;
|
|
}
|
|
|
|
if (!tp->syn_fastopen) {
|
|
/* Ignore an unsolicited cookie */
|
|
cookie->len = -1;
|
|
} else if (tp->total_retrans) {
|
|
/* SYN timed out and the SYN-ACK neither has a cookie nor
|
|
* acknowledges data. Presumably the remote received only
|
|
* the retransmitted (regular) SYNs: either the original
|
|
* SYN-data or the corresponding SYN-ACK was dropped.
|
|
*/
|
|
syn_drop = (cookie->len < 0 && data);
|
|
} else if (cookie->len < 0 && !tp->syn_data) {
|
|
/* We requested a cookie but didn't get it. If we did not use
|
|
* the (old) exp opt format then try so next time (try_exp=1).
|
|
* Otherwise we go back to use the RFC7413 opt (try_exp=2).
|
|
*/
|
|
try_exp = tp->syn_fastopen_exp ? 2 : 1;
|
|
}
|
|
|
|
tcp_fastopen_cache_set(sk, mss, cookie, syn_drop, try_exp);
|
|
|
|
if (data) { /* Retransmit unacked data in SYN */
|
|
tcp_for_write_queue_from(data, sk) {
|
|
if (data == tcp_send_head(sk) ||
|
|
__tcp_retransmit_skb(sk, data))
|
|
break;
|
|
}
|
|
tcp_rearm_rto(sk);
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENACTIVEFAIL);
|
|
return true;
|
|
}
|
|
tp->syn_data_acked = tp->syn_data;
|
|
if (tp->syn_data_acked)
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENACTIVE);
|
|
return false;
|
|
}
|
|
|
|
static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
|
|
const struct tcphdr *th, unsigned int len)
|
|
{
|
|
struct inet_connection_sock *icsk = inet_csk(sk);
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct tcp_fastopen_cookie foc = { .len = -1 };
|
|
int saved_clamp = tp->rx_opt.mss_clamp;
|
|
|
|
tcp_parse_options(skb, &tp->rx_opt, 0, &foc);
|
|
if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
|
|
tp->rx_opt.rcv_tsecr -= tp->tsoffset;
|
|
|
|
if (th->ack) {
|
|
/* rfc793:
|
|
* "If the state is SYN-SENT then
|
|
* first check the ACK bit
|
|
* If the ACK bit is set
|
|
* If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
|
|
* a reset (unless the RST bit is set, if so drop
|
|
* the segment and return)"
|
|
*/
|
|
if (!after(TCP_SKB_CB(skb)->ack_seq, tp->snd_una) ||
|
|
after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt))
|
|
goto reset_and_undo;
|
|
|
|
if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
|
|
!between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp,
|
|
tcp_time_stamp)) {
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSACTIVEREJECTED);
|
|
goto reset_and_undo;
|
|
}
|
|
|
|
/* Now ACK is acceptable.
|
|
*
|
|
* "If the RST bit is set
|
|
* If the ACK was acceptable then signal the user "error:
|
|
* connection reset", drop the segment, enter CLOSED state,
|
|
* delete TCB, and return."
|
|
*/
|
|
|
|
if (th->rst) {
|
|
tcp_reset(sk);
|
|
goto discard;
|
|
}
|
|
|
|
/* rfc793:
|
|
* "fifth, if neither of the SYN or RST bits is set then
|
|
* drop the segment and return."
|
|
*
|
|
* See note below!
|
|
* --ANK(990513)
|
|
*/
|
|
if (!th->syn)
|
|
goto discard_and_undo;
|
|
|
|
/* rfc793:
|
|
* "If the SYN bit is on ...
|
|
* are acceptable then ...
|
|
* (our SYN has been ACKed), change the connection
|
|
* state to ESTABLISHED..."
|
|
*/
|
|
|
|
tcp_ecn_rcv_synack(tp, th);
|
|
|
|
tcp_init_wl(tp, TCP_SKB_CB(skb)->seq);
|
|
tcp_ack(sk, skb, FLAG_SLOWPATH);
|
|
|
|
/* Ok.. it's good. Set up sequence numbers and
|
|
* move to established.
|
|
*/
|
|
tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
|
|
tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
|
|
|
|
/* RFC1323: The window in SYN & SYN/ACK segments is
|
|
* never scaled.
|
|
*/
|
|
tp->snd_wnd = ntohs(th->window);
|
|
|
|
if (!tp->rx_opt.wscale_ok) {
|
|
tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0;
|
|
tp->window_clamp = min(tp->window_clamp, 65535U);
|
|
}
|
|
|
|
if (tp->rx_opt.saw_tstamp) {
|
|
tp->rx_opt.tstamp_ok = 1;
|
|
tp->tcp_header_len =
|
|
sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
|
|
tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
|
|
tcp_store_ts_recent(tp);
|
|
} else {
|
|
tp->tcp_header_len = sizeof(struct tcphdr);
|
|
}
|
|
|
|
if (tcp_is_sack(tp) && sysctl_tcp_fack)
|
|
tcp_enable_fack(tp);
|
|
|
|
tcp_mtup_init(sk);
|
|
tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
|
|
tcp_initialize_rcv_mss(sk);
|
|
|
|
/* Remember, tcp_poll() does not lock socket!
|
|
* Change state from SYN-SENT only after copied_seq
|
|
* is initialized. */
|
|
tp->copied_seq = tp->rcv_nxt;
|
|
|
|
smp_mb();
|
|
|
|
tcp_finish_connect(sk, skb);
|
|
|
|
if ((tp->syn_fastopen || tp->syn_data) &&
|
|
tcp_rcv_fastopen_synack(sk, skb, &foc))
|
|
return -1;
|
|
|
|
if (sk->sk_write_pending ||
|
|
icsk->icsk_accept_queue.rskq_defer_accept ||
|
|
icsk->icsk_ack.pingpong) {
|
|
/* Save one ACK. Data will be ready after
|
|
* several ticks, if write_pending is set.
|
|
*
|
|
* It may be deleted, but with this feature tcpdumps
|
|
* look so _wonderfully_ clever, that I was not able
|
|
* to stand against the temptation 8) --ANK
|
|
*/
|
|
inet_csk_schedule_ack(sk);
|
|
icsk->icsk_ack.lrcvtime = tcp_time_stamp;
|
|
tcp_enter_quickack_mode(sk);
|
|
inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
|
|
TCP_DELACK_MAX, TCP_RTO_MAX);
|
|
|
|
discard:
|
|
__kfree_skb(skb);
|
|
return 0;
|
|
} else {
|
|
tcp_send_ack(sk);
|
|
}
|
|
return -1;
|
|
}
|
|
|
|
/* No ACK in the segment */
|
|
|
|
if (th->rst) {
|
|
/* rfc793:
|
|
* "If the RST bit is set
|
|
*
|
|
* Otherwise (no ACK) drop the segment and return."
|
|
*/
|
|
|
|
goto discard_and_undo;
|
|
}
|
|
|
|
/* PAWS check. */
|
|
if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp &&
|
|
tcp_paws_reject(&tp->rx_opt, 0))
|
|
goto discard_and_undo;
|
|
|
|
if (th->syn) {
|
|
/* We see SYN without ACK. It is attempt of
|
|
* simultaneous connect with crossed SYNs.
|
|
* Particularly, it can be connect to self.
|
|
*/
|
|
tcp_set_state(sk, TCP_SYN_RECV);
|
|
|
|
if (tp->rx_opt.saw_tstamp) {
|
|
tp->rx_opt.tstamp_ok = 1;
|
|
tcp_store_ts_recent(tp);
|
|
tp->tcp_header_len =
|
|
sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
|
|
} else {
|
|
tp->tcp_header_len = sizeof(struct tcphdr);
|
|
}
|
|
|
|
tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
|
|
tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
|
|
|
|
/* RFC1323: The window in SYN & SYN/ACK segments is
|
|
* never scaled.
|
|
*/
|
|
tp->snd_wnd = ntohs(th->window);
|
|
tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
|
|
tp->max_window = tp->snd_wnd;
|
|
|
|
tcp_ecn_rcv_syn(tp, th);
|
|
|
|
tcp_mtup_init(sk);
|
|
tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
|
|
tcp_initialize_rcv_mss(sk);
|
|
|
|
tcp_send_synack(sk);
|
|
#if 0
|
|
/* Note, we could accept data and URG from this segment.
|
|
* There are no obstacles to make this (except that we must
|
|
* either change tcp_recvmsg() to prevent it from returning data
|
|
* before 3WHS completes per RFC793, or employ TCP Fast Open).
|
|
*
|
|
* However, if we ignore data in ACKless segments sometimes,
|
|
* we have no reasons to accept it sometimes.
|
|
* Also, seems the code doing it in step6 of tcp_rcv_state_process
|
|
* is not flawless. So, discard packet for sanity.
|
|
* Uncomment this return to process the data.
|
|
*/
|
|
return -1;
|
|
#else
|
|
goto discard;
|
|
#endif
|
|
}
|
|
/* "fifth, if neither of the SYN or RST bits is set then
|
|
* drop the segment and return."
|
|
*/
|
|
|
|
discard_and_undo:
|
|
tcp_clear_options(&tp->rx_opt);
|
|
tp->rx_opt.mss_clamp = saved_clamp;
|
|
goto discard;
|
|
|
|
reset_and_undo:
|
|
tcp_clear_options(&tp->rx_opt);
|
|
tp->rx_opt.mss_clamp = saved_clamp;
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* This function implements the receiving procedure of RFC 793 for
|
|
* all states except ESTABLISHED and TIME_WAIT.
|
|
* It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
|
|
* address independent.
|
|
*/
|
|
|
|
int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
|
|
const struct tcphdr *th, unsigned int len)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct inet_connection_sock *icsk = inet_csk(sk);
|
|
struct request_sock *req;
|
|
int queued = 0;
|
|
bool acceptable;
|
|
u32 synack_stamp;
|
|
|
|
tp->rx_opt.saw_tstamp = 0;
|
|
|
|
switch (sk->sk_state) {
|
|
case TCP_CLOSE:
|
|
goto discard;
|
|
|
|
case TCP_LISTEN:
|
|
if (th->ack)
|
|
return 1;
|
|
|
|
if (th->rst)
|
|
goto discard;
|
|
|
|
if (th->syn) {
|
|
if (th->fin)
|
|
goto discard;
|
|
if (icsk->icsk_af_ops->conn_request(sk, skb) < 0)
|
|
return 1;
|
|
|
|
/* Now we have several options: In theory there is
|
|
* nothing else in the frame. KA9Q has an option to
|
|
* send data with the syn, BSD accepts data with the
|
|
* syn up to the [to be] advertised window and
|
|
* Solaris 2.1 gives you a protocol error. For now
|
|
* we just ignore it, that fits the spec precisely
|
|
* and avoids incompatibilities. It would be nice in
|
|
* future to drop through and process the data.
|
|
*
|
|
* Now that TTCP is starting to be used we ought to
|
|
* queue this data.
|
|
* But, this leaves one open to an easy denial of
|
|
* service attack, and SYN cookies can't defend
|
|
* against this problem. So, we drop the data
|
|
* in the interest of security over speed unless
|
|
* it's still in use.
|
|
*/
|
|
kfree_skb(skb);
|
|
return 0;
|
|
}
|
|
goto discard;
|
|
|
|
case TCP_SYN_SENT:
|
|
queued = tcp_rcv_synsent_state_process(sk, skb, th, len);
|
|
if (queued >= 0)
|
|
return queued;
|
|
|
|
/* Do step6 onward by hand. */
|
|
tcp_urg(sk, skb, th);
|
|
__kfree_skb(skb);
|
|
tcp_data_snd_check(sk);
|
|
return 0;
|
|
}
|
|
|
|
req = tp->fastopen_rsk;
|
|
if (req) {
|
|
WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV &&
|
|
sk->sk_state != TCP_FIN_WAIT1);
|
|
|
|
if (!tcp_check_req(sk, skb, req, true))
|
|
goto discard;
|
|
}
|
|
|
|
if (!th->ack && !th->rst && !th->syn)
|
|
goto discard;
|
|
|
|
if (!tcp_validate_incoming(sk, skb, th, 0))
|
|
return 0;
|
|
|
|
/* step 5: check the ACK field */
|
|
acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH |
|
|
FLAG_UPDATE_TS_RECENT) > 0;
|
|
|
|
switch (sk->sk_state) {
|
|
case TCP_SYN_RECV:
|
|
if (!acceptable)
|
|
return 1;
|
|
|
|
/* Once we leave TCP_SYN_RECV, we no longer need req
|
|
* so release it.
|
|
*/
|
|
if (req) {
|
|
synack_stamp = tcp_rsk(req)->snt_synack;
|
|
tp->total_retrans = req->num_retrans;
|
|
reqsk_fastopen_remove(sk, req, false);
|
|
} else {
|
|
synack_stamp = tp->lsndtime;
|
|
/* Make sure socket is routed, for correct metrics. */
|
|
icsk->icsk_af_ops->rebuild_header(sk);
|
|
tcp_init_congestion_control(sk);
|
|
|
|
tcp_mtup_init(sk);
|
|
tp->copied_seq = tp->rcv_nxt;
|
|
tcp_init_buffer_space(sk);
|
|
}
|
|
smp_mb();
|
|
tcp_set_state(sk, TCP_ESTABLISHED);
|
|
sk->sk_state_change(sk);
|
|
|
|
/* Note, that this wakeup is only for marginal crossed SYN case.
|
|
* Passively open sockets are not waked up, because
|
|
* sk->sk_sleep == NULL and sk->sk_socket == NULL.
|
|
*/
|
|
if (sk->sk_socket)
|
|
sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
|
|
|
|
tp->snd_una = TCP_SKB_CB(skb)->ack_seq;
|
|
tp->snd_wnd = ntohs(th->window) << tp->rx_opt.snd_wscale;
|
|
tcp_init_wl(tp, TCP_SKB_CB(skb)->seq);
|
|
tcp_synack_rtt_meas(sk, synack_stamp);
|
|
|
|
if (tp->rx_opt.tstamp_ok)
|
|
tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
|
|
|
|
if (req) {
|
|
/* Re-arm the timer because data may have been sent out.
|
|
* This is similar to the regular data transmission case
|
|
* when new data has just been ack'ed.
|
|
*
|
|
* (TFO) - we could try to be more aggressive and
|
|
* retransmitting any data sooner based on when they
|
|
* are sent out.
|
|
*/
|
|
tcp_rearm_rto(sk);
|
|
} else
|
|
tcp_init_metrics(sk);
|
|
|
|
tcp_update_pacing_rate(sk);
|
|
|
|
/* Prevent spurious tcp_cwnd_restart() on first data packet */
|
|
tp->lsndtime = tcp_time_stamp;
|
|
|
|
tcp_initialize_rcv_mss(sk);
|
|
tcp_fast_path_on(tp);
|
|
break;
|
|
|
|
case TCP_FIN_WAIT1: {
|
|
struct dst_entry *dst;
|
|
int tmo;
|
|
|
|
/* If we enter the TCP_FIN_WAIT1 state and we are a
|
|
* Fast Open socket and this is the first acceptable
|
|
* ACK we have received, this would have acknowledged
|
|
* our SYNACK so stop the SYNACK timer.
|
|
*/
|
|
if (req) {
|
|
/* Return RST if ack_seq is invalid.
|
|
* Note that RFC793 only says to generate a
|
|
* DUPACK for it but for TCP Fast Open it seems
|
|
* better to treat this case like TCP_SYN_RECV
|
|
* above.
|
|
*/
|
|
if (!acceptable)
|
|
return 1;
|
|
/* We no longer need the request sock. */
|
|
reqsk_fastopen_remove(sk, req, false);
|
|
tcp_rearm_rto(sk);
|
|
}
|
|
if (tp->snd_una != tp->write_seq)
|
|
break;
|
|
|
|
tcp_set_state(sk, TCP_FIN_WAIT2);
|
|
sk->sk_shutdown |= SEND_SHUTDOWN;
|
|
|
|
dst = __sk_dst_get(sk);
|
|
if (dst)
|
|
dst_confirm(dst);
|
|
|
|
if (!sock_flag(sk, SOCK_DEAD)) {
|
|
/* Wake up lingering close() */
|
|
sk->sk_state_change(sk);
|
|
break;
|
|
}
|
|
|
|
if (tp->linger2 < 0 ||
|
|
(TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
|
|
after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) {
|
|
tcp_done(sk);
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONDATA);
|
|
return 1;
|
|
}
|
|
|
|
tmo = tcp_fin_time(sk);
|
|
if (tmo > TCP_TIMEWAIT_LEN) {
|
|
inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN);
|
|
} else if (th->fin || sock_owned_by_user(sk)) {
|
|
/* Bad case. We could lose such FIN otherwise.
|
|
* It is not a big problem, but it looks confusing
|
|
* and not so rare event. We still can lose it now,
|
|
* if it spins in bh_lock_sock(), but it is really
|
|
* marginal case.
|
|
*/
|
|
inet_csk_reset_keepalive_timer(sk, tmo);
|
|
} else {
|
|
tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
|
|
goto discard;
|
|
}
|
|
break;
|
|
}
|
|
|
|
case TCP_CLOSING:
|
|
if (tp->snd_una == tp->write_seq) {
|
|
tcp_time_wait(sk, TCP_TIME_WAIT, 0);
|
|
goto discard;
|
|
}
|
|
break;
|
|
|
|
case TCP_LAST_ACK:
|
|
if (tp->snd_una == tp->write_seq) {
|
|
tcp_update_metrics(sk);
|
|
tcp_done(sk);
|
|
goto discard;
|
|
}
|
|
break;
|
|
}
|
|
|
|
/* step 6: check the URG bit */
|
|
tcp_urg(sk, skb, th);
|
|
|
|
/* step 7: process the segment text */
|
|
switch (sk->sk_state) {
|
|
case TCP_CLOSE_WAIT:
|
|
case TCP_CLOSING:
|
|
case TCP_LAST_ACK:
|
|
if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
|
|
break;
|
|
case TCP_FIN_WAIT1:
|
|
case TCP_FIN_WAIT2:
|
|
/* RFC 793 says to queue data in these states,
|
|
* RFC 1122 says we MUST send a reset.
|
|
* BSD 4.4 also does reset.
|
|
*/
|
|
if (sk->sk_shutdown & RCV_SHUTDOWN) {
|
|
if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
|
|
after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) {
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONDATA);
|
|
tcp_reset(sk);
|
|
return 1;
|
|
}
|
|
}
|
|
/* Fall through */
|
|
case TCP_ESTABLISHED:
|
|
tcp_data_queue(sk, skb);
|
|
queued = 1;
|
|
break;
|
|
}
|
|
|
|
/* tcp_data could move socket to TIME-WAIT */
|
|
if (sk->sk_state != TCP_CLOSE) {
|
|
tcp_data_snd_check(sk);
|
|
tcp_ack_snd_check(sk);
|
|
}
|
|
|
|
if (!queued) {
|
|
discard:
|
|
__kfree_skb(skb);
|
|
}
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(tcp_rcv_state_process);
|
|
|
|
static inline void pr_drop_req(struct request_sock *req, __u16 port, int family)
|
|
{
|
|
struct inet_request_sock *ireq = inet_rsk(req);
|
|
|
|
if (family == AF_INET)
|
|
net_dbg_ratelimited("drop open request from %pI4/%u\n",
|
|
&ireq->ir_rmt_addr, port);
|
|
#if IS_ENABLED(CONFIG_IPV6)
|
|
else if (family == AF_INET6)
|
|
net_dbg_ratelimited("drop open request from %pI6/%u\n",
|
|
&ireq->ir_v6_rmt_addr, port);
|
|
#endif
|
|
}
|
|
|
|
/* RFC3168 : 6.1.1 SYN packets must not have ECT/ECN bits set
|
|
*
|
|
* If we receive a SYN packet with these bits set, it means a
|
|
* network is playing bad games with TOS bits. In order to
|
|
* avoid possible false congestion notifications, we disable
|
|
* TCP ECN negotiation.
|
|
*
|
|
* Exception: tcp_ca wants ECN. This is required for DCTCP
|
|
* congestion control: Linux DCTCP asserts ECT on all packets,
|
|
* including SYN, which is most optimal solution; however,
|
|
* others, such as FreeBSD do not.
|
|
*/
|
|
static void tcp_ecn_create_request(struct request_sock *req,
|
|
const struct sk_buff *skb,
|
|
const struct sock *listen_sk,
|
|
const struct dst_entry *dst)
|
|
{
|
|
const struct tcphdr *th = tcp_hdr(skb);
|
|
const struct net *net = sock_net(listen_sk);
|
|
bool th_ecn = th->ece && th->cwr;
|
|
bool ect, ecn_ok;
|
|
u32 ecn_ok_dst;
|
|
|
|
if (!th_ecn)
|
|
return;
|
|
|
|
ect = !INET_ECN_is_not_ect(TCP_SKB_CB(skb)->ip_dsfield);
|
|
ecn_ok_dst = dst_feature(dst, DST_FEATURE_ECN_MASK);
|
|
ecn_ok = net->ipv4.sysctl_tcp_ecn || ecn_ok_dst;
|
|
|
|
if ((!ect && ecn_ok) || tcp_ca_needs_ecn(listen_sk) ||
|
|
(ecn_ok_dst & DST_FEATURE_ECN_CA))
|
|
inet_rsk(req)->ecn_ok = 1;
|
|
}
|
|
|
|
static void tcp_openreq_init(struct request_sock *req,
|
|
const struct tcp_options_received *rx_opt,
|
|
struct sk_buff *skb, const struct sock *sk)
|
|
{
|
|
struct inet_request_sock *ireq = inet_rsk(req);
|
|
|
|
req->rcv_wnd = 0; /* So that tcp_send_synack() knows! */
|
|
req->cookie_ts = 0;
|
|
tcp_rsk(req)->rcv_isn = TCP_SKB_CB(skb)->seq;
|
|
tcp_rsk(req)->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
|
|
tcp_rsk(req)->snt_synack = tcp_time_stamp;
|
|
tcp_rsk(req)->last_oow_ack_time = 0;
|
|
req->mss = rx_opt->mss_clamp;
|
|
req->ts_recent = rx_opt->saw_tstamp ? rx_opt->rcv_tsval : 0;
|
|
ireq->tstamp_ok = rx_opt->tstamp_ok;
|
|
ireq->sack_ok = rx_opt->sack_ok;
|
|
ireq->snd_wscale = rx_opt->snd_wscale;
|
|
ireq->wscale_ok = rx_opt->wscale_ok;
|
|
ireq->acked = 0;
|
|
ireq->ecn_ok = 0;
|
|
ireq->ir_rmt_port = tcp_hdr(skb)->source;
|
|
ireq->ir_num = ntohs(tcp_hdr(skb)->dest);
|
|
ireq->ir_mark = inet_request_mark(sk, skb);
|
|
}
|
|
|
|
struct request_sock *inet_reqsk_alloc(const struct request_sock_ops *ops,
|
|
struct sock *sk_listener)
|
|
{
|
|
struct request_sock *req = reqsk_alloc(ops, sk_listener);
|
|
|
|
if (req) {
|
|
struct inet_request_sock *ireq = inet_rsk(req);
|
|
|
|
kmemcheck_annotate_bitfield(ireq, flags);
|
|
ireq->opt = NULL;
|
|
atomic64_set(&ireq->ir_cookie, 0);
|
|
ireq->ireq_state = TCP_NEW_SYN_RECV;
|
|
write_pnet(&ireq->ireq_net, sock_net(sk_listener));
|
|
ireq->ireq_family = sk_listener->sk_family;
|
|
}
|
|
|
|
return req;
|
|
}
|
|
EXPORT_SYMBOL(inet_reqsk_alloc);
|
|
|
|
/*
|
|
* Return true if a syncookie should be sent
|
|
*/
|
|
static bool tcp_syn_flood_action(struct sock *sk,
|
|
const struct sk_buff *skb,
|
|
const char *proto)
|
|
{
|
|
const char *msg = "Dropping request";
|
|
bool want_cookie = false;
|
|
struct listen_sock *lopt;
|
|
|
|
#ifdef CONFIG_SYN_COOKIES
|
|
if (sysctl_tcp_syncookies) {
|
|
msg = "Sending cookies";
|
|
want_cookie = true;
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPREQQFULLDOCOOKIES);
|
|
} else
|
|
#endif
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPREQQFULLDROP);
|
|
|
|
lopt = inet_csk(sk)->icsk_accept_queue.listen_opt;
|
|
if (!lopt->synflood_warned && sysctl_tcp_syncookies != 2) {
|
|
lopt->synflood_warned = 1;
|
|
pr_info("%s: Possible SYN flooding on port %d. %s. Check SNMP counters.\n",
|
|
proto, ntohs(tcp_hdr(skb)->dest), msg);
|
|
}
|
|
return want_cookie;
|
|
}
|
|
|
|
static void tcp_reqsk_record_syn(const struct sock *sk,
|
|
struct request_sock *req,
|
|
const struct sk_buff *skb)
|
|
{
|
|
if (tcp_sk(sk)->save_syn) {
|
|
u32 len = skb_network_header_len(skb) + tcp_hdrlen(skb);
|
|
u32 *copy;
|
|
|
|
copy = kmalloc(len + sizeof(u32), GFP_ATOMIC);
|
|
if (copy) {
|
|
copy[0] = len;
|
|
memcpy(©[1], skb_network_header(skb), len);
|
|
req->saved_syn = copy;
|
|
}
|
|
}
|
|
}
|
|
|
|
int tcp_conn_request(struct request_sock_ops *rsk_ops,
|
|
const struct tcp_request_sock_ops *af_ops,
|
|
struct sock *sk, struct sk_buff *skb)
|
|
{
|
|
struct tcp_options_received tmp_opt;
|
|
struct request_sock *req;
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct dst_entry *dst = NULL;
|
|
__u32 isn = TCP_SKB_CB(skb)->tcp_tw_isn;
|
|
bool want_cookie = false, fastopen;
|
|
struct flowi fl;
|
|
struct tcp_fastopen_cookie foc = { .len = -1 };
|
|
int err;
|
|
|
|
|
|
/* TW buckets are converted to open requests without
|
|
* limitations, they conserve resources and peer is
|
|
* evidently real one.
|
|
*/
|
|
if ((sysctl_tcp_syncookies == 2 ||
|
|
inet_csk_reqsk_queue_is_full(sk)) && !isn) {
|
|
want_cookie = tcp_syn_flood_action(sk, skb, rsk_ops->slab_name);
|
|
if (!want_cookie)
|
|
goto drop;
|
|
}
|
|
|
|
|
|
/* Accept backlog is full. If we have already queued enough
|
|
* of warm entries in syn queue, drop request. It is better than
|
|
* clogging syn queue with openreqs with exponentially increasing
|
|
* timeout.
|
|
*/
|
|
if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1) {
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS);
|
|
goto drop;
|
|
}
|
|
|
|
req = inet_reqsk_alloc(rsk_ops, sk);
|
|
if (!req)
|
|
goto drop;
|
|
|
|
tcp_rsk(req)->af_specific = af_ops;
|
|
|
|
tcp_clear_options(&tmp_opt);
|
|
tmp_opt.mss_clamp = af_ops->mss_clamp;
|
|
tmp_opt.user_mss = tp->rx_opt.user_mss;
|
|
tcp_parse_options(skb, &tmp_opt, 0, want_cookie ? NULL : &foc);
|
|
|
|
if (want_cookie && !tmp_opt.saw_tstamp)
|
|
tcp_clear_options(&tmp_opt);
|
|
|
|
tmp_opt.tstamp_ok = tmp_opt.saw_tstamp;
|
|
tcp_openreq_init(req, &tmp_opt, skb, sk);
|
|
|
|
/* Note: tcp_v6_init_req() might override ir_iif for link locals */
|
|
inet_rsk(req)->ir_iif = sk->sk_bound_dev_if;
|
|
|
|
af_ops->init_req(req, sk, skb);
|
|
|
|
if (security_inet_conn_request(sk, skb, req))
|
|
goto drop_and_free;
|
|
|
|
if (!want_cookie && !isn) {
|
|
/* VJ's idea. We save last timestamp seen
|
|
* from the destination in peer table, when entering
|
|
* state TIME-WAIT, and check against it before
|
|
* accepting new connection request.
|
|
*
|
|
* If "isn" is not zero, this request hit alive
|
|
* timewait bucket, so that all the necessary checks
|
|
* are made in the function processing timewait state.
|
|
*/
|
|
if (tcp_death_row.sysctl_tw_recycle) {
|
|
bool strict;
|
|
|
|
dst = af_ops->route_req(sk, &fl, req, &strict);
|
|
|
|
if (dst && strict &&
|
|
!tcp_peer_is_proven(req, dst, true,
|
|
tmp_opt.saw_tstamp)) {
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSPASSIVEREJECTED);
|
|
goto drop_and_release;
|
|
}
|
|
}
|
|
/* Kill the following clause, if you dislike this way. */
|
|
else if (!sysctl_tcp_syncookies &&
|
|
(sysctl_max_syn_backlog - inet_csk_reqsk_queue_len(sk) <
|
|
(sysctl_max_syn_backlog >> 2)) &&
|
|
!tcp_peer_is_proven(req, dst, false,
|
|
tmp_opt.saw_tstamp)) {
|
|
/* Without syncookies last quarter of
|
|
* backlog is filled with destinations,
|
|
* proven to be alive.
|
|
* It means that we continue to communicate
|
|
* to destinations, already remembered
|
|
* to the moment of synflood.
|
|
*/
|
|
pr_drop_req(req, ntohs(tcp_hdr(skb)->source),
|
|
rsk_ops->family);
|
|
goto drop_and_release;
|
|
}
|
|
|
|
isn = af_ops->init_seq(skb);
|
|
}
|
|
if (!dst) {
|
|
dst = af_ops->route_req(sk, &fl, req, NULL);
|
|
if (!dst)
|
|
goto drop_and_free;
|
|
}
|
|
|
|
tcp_ecn_create_request(req, skb, sk, dst);
|
|
|
|
if (want_cookie) {
|
|
isn = cookie_init_sequence(af_ops, sk, skb, &req->mss);
|
|
req->cookie_ts = tmp_opt.tstamp_ok;
|
|
if (!tmp_opt.tstamp_ok)
|
|
inet_rsk(req)->ecn_ok = 0;
|
|
}
|
|
|
|
tcp_rsk(req)->snt_isn = isn;
|
|
tcp_openreq_init_rwin(req, sk, dst);
|
|
fastopen = !want_cookie &&
|
|
tcp_try_fastopen(sk, skb, req, &foc, dst);
|
|
err = af_ops->send_synack(sk, dst, &fl, req,
|
|
skb_get_queue_mapping(skb), &foc);
|
|
if (!fastopen) {
|
|
if (err || want_cookie)
|
|
goto drop_and_free;
|
|
|
|
tcp_rsk(req)->tfo_listener = false;
|
|
af_ops->queue_hash_add(sk, req, TCP_TIMEOUT_INIT);
|
|
}
|
|
tcp_reqsk_record_syn(sk, req, skb);
|
|
|
|
return 0;
|
|
|
|
drop_and_release:
|
|
dst_release(dst);
|
|
drop_and_free:
|
|
reqsk_free(req);
|
|
drop:
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENDROPS);
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(tcp_conn_request);
|