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tcp: consolidate SYNACK RTT sampling 

The first patch consolidates SYNACK and other RTT measurement to use a
central function tcp_ack_update_rtt(). A (small) bonus is now SYNACK
RTT measurement happens after PAWS check, potentially reducing the
impact of RTO seeding on bad TCP timestamps values.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Yuchung Cheng 2013-07-22 16:20:45 -07:00 committed by David S. Miller
parent c3f51d5f38
commit 375fe02c91
5 changed files with 14 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
include/net/tcp.h
View File

@ -1094,15 +1094,6 @@ static inline void tcp_openreq_init(struct request_sock *req,
ireq->loc_port = tcp_hdr(skb)->dest; ireq->loc_port = tcp_hdr(skb)->dest;
} }
/* Compute time elapsed between SYNACK and the ACK completing 3WHS */
static inline void tcp_synack_rtt_meas(struct sock *sk,
struct request_sock *req)
{
if (tcp_rsk(req)->snt_synack)
tcp_valid_rtt_meas(sk,
tcp_time_stamp - tcp_rsk(req)->snt_synack);
}
extern void tcp_enter_memory_pressure(struct sock *sk); extern void tcp_enter_memory_pressure(struct sock *sk);
static inline int keepalive_intvl_when(const struct tcp_sock *tp) static inline int keepalive_intvl_when(const struct tcp_sock *tp)

14
net/ipv4/tcp_input.c
View File

@ -2853,6 +2853,17 @@ static inline void tcp_ack_update_rtt(struct sock *sk, const int flag,
tcp_ack_no_tstamp(sk, seq_rtt, flag); tcp_ack_no_tstamp(sk, seq_rtt, flag);
} }
/* Compute time elapsed between (last) SYNACK and the ACK completing 3WHS. */
static void tcp_synack_rtt_meas(struct sock *sk, struct request_sock *req)
{
struct tcp_sock *tp = tcp_sk(sk);
s32 seq_rtt = -1;
if (tp->lsndtime && !tp->total_retrans)
seq_rtt = tcp_time_stamp - tp->lsndtime;
tcp_ack_update_rtt(sk, FLAG_SYN_ACKED, seq_rtt);
}
static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 in_flight) static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
{ {
const struct inet_connection_sock *icsk = inet_csk(sk); const struct inet_connection_sock *icsk = inet_csk(sk);
@ -5624,9 +5635,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
* so release it. * so release it.
*/ */
if (req) { if (req) {
tcp_synack_rtt_meas(sk, req);
tp->total_retrans = req->num_retrans; tp->total_retrans = req->num_retrans;
reqsk_fastopen_remove(sk, req, false); reqsk_fastopen_remove(sk, req, false);
} else { } else {
/* Make sure socket is routed, for correct metrics. */ /* Make sure socket is routed, for correct metrics. */
@ -5651,6 +5660,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
tp->snd_una = TCP_SKB_CB(skb)->ack_seq; tp->snd_una = TCP_SKB_CB(skb)->ack_seq;
tp->snd_wnd = ntohs(th->window) << tp->rx_opt.snd_wscale; tp->snd_wnd = ntohs(th->window) << tp->rx_opt.snd_wscale;
tcp_init_wl(tp, TCP_SKB_CB(skb)->seq); tcp_init_wl(tp, TCP_SKB_CB(skb)->seq);
tcp_synack_rtt_meas(sk, req);
if (tp->rx_opt.tstamp_ok) if (tp->rx_opt.tstamp_ok)
tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;

2
net/ipv4/tcp_ipv4.c
View File

@ -1671,8 +1671,6 @@ struct sock *tcp_v4_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
newtp->advmss = tcp_sk(sk)->rx_opt.user_mss; newtp->advmss = tcp_sk(sk)->rx_opt.user_mss;
tcp_initialize_rcv_mss(newsk); tcp_initialize_rcv_mss(newsk);
tcp_synack_rtt_meas(newsk, req);
newtp->total_retrans = req->num_retrans;
#ifdef CONFIG_TCP_MD5SIG #ifdef CONFIG_TCP_MD5SIG
/* Copy over the MD5 key from the original socket */ /* Copy over the MD5 key from the original socket */

8
net/ipv4/tcp_minisocks.c
View File

@ -411,6 +411,8 @@ struct sock *tcp_create_openreq_child(struct sock *sk, struct request_sock *req,
newtp->snd_ssthresh = TCP_INFINITE_SSTHRESH; newtp->snd_ssthresh = TCP_INFINITE_SSTHRESH;
tcp_enable_early_retrans(newtp); tcp_enable_early_retrans(newtp);
newtp->tlp_high_seq = 0; newtp->tlp_high_seq = 0;
newtp->lsndtime = treq->snt_synack;
newtp->total_retrans = req->num_retrans;
/* So many TCP implementations out there (incorrectly) count the /* So many TCP implementations out there (incorrectly) count the
* initial SYN frame in their delayed-ACK and congestion control * initial SYN frame in their delayed-ACK and congestion control
@ -666,12 +668,6 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
if (!(flg & TCP_FLAG_ACK)) if (!(flg & TCP_FLAG_ACK))
return NULL; return NULL;
/* Got ACK for our SYNACK, so update baseline for SYNACK RTT sample. */
if (tmp_opt.saw_tstamp && tmp_opt.rcv_tsecr)
tcp_rsk(req)->snt_synack = tmp_opt.rcv_tsecr;
else if (req->num_retrans) /* don't take RTT sample if retrans && ~TS */
tcp_rsk(req)->snt_synack = 0;
/* For Fast Open no more processing is needed (sk is the /* For Fast Open no more processing is needed (sk is the
* child socket). * child socket).
*/ */

2
net/ipv6/tcp_ipv6.c
View File

@ -1237,8 +1237,6 @@ static struct sock * tcp_v6_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
newtp->advmss = tcp_sk(sk)->rx_opt.user_mss; newtp->advmss = tcp_sk(sk)->rx_opt.user_mss;
tcp_initialize_rcv_mss(newsk); tcp_initialize_rcv_mss(newsk);
tcp_synack_rtt_meas(newsk, req);
newtp->total_retrans = req->num_retrans;
newinet->inet_daddr = newinet->inet_saddr = LOOPBACK4_IPV6; newinet->inet_daddr = newinet->inet_saddr = LOOPBACK4_IPV6;
newinet->inet_rcv_saddr = LOOPBACK4_IPV6; newinet->inet_rcv_saddr = LOOPBACK4_IPV6;