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udplite: fast-path computation of checksum coverage 

Commit 903ab86d19 of 1 March this year ("udp: Add
lockless transmit path") introduced a new fast TX path that broke the checksum
coverage computation of UDP-lite, which so far depended on up->len (only set
if the socket is locked and 0 in the fast path).

Fixed by providing both fast- and slow-path computation of checksum coverage.
The latter can be removed when UDP(-lite)v6 also uses a lockless transmit path.
 
Reported-by: Thomas Volkert <thomas@homer-conferencing.com>
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Gerrit Renker 2011-10-17 19:07:30 -04:00 committed by David S. Miller
parent 4c41042d1d
commit f36c23bb9f
1 changed files with 34 additions and 35 deletions
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69
include/net/udplite.h
View File

@ -66,41 +66,35 @@ static inline int udplite_checksum_init(struct sk_buff *skb, struct udphdr *uh)
return 0;
}
static inline int udplite_sender_cscov(struct udp_sock *up, struct udphdr *uh)
{
int cscov = up->len;
/*
* Sender has set `partial coverage' option on UDP-Lite socket
*/
if (up->pcflag & UDPLITE_SEND_CC) {
if (up->pcslen < up->len) {
/* up->pcslen == 0 means that full coverage is required,
* partial coverage only if 0 < up->pcslen < up->len */
if (0 < up->pcslen) {
cscov = up->pcslen;
}
uh->len = htons(up->pcslen);
}
/*
* NOTE: Causes for the error case `up->pcslen > up->len':
* (i) Application error (will not be penalized).
* (ii) Payload too big for send buffer: data is split
* into several packets, each with its own header.
* In this case (e.g. last segment), coverage may
* exceed packet length.
* Since packets with coverage length > packet length are
* illegal, we fall back to the defaults here.
*/
}
return cscov;
}
/* Slow-path computation of checksum. Socket is locked. */
static inline __wsum udplite_csum_outgoing(struct sock *sk, struct sk_buff *skb)
{
int cscov = udplite_sender_cscov(udp_sk(sk), udp_hdr(skb));
const struct udp_sock *up = udp_sk(skb->sk);
int cscov = up->len;
__wsum csum = 0;
if (up->pcflag & UDPLITE_SEND_CC) {
/*
* Sender has set `partial coverage' option on UDP-Lite socket.
* The special case "up->pcslen == 0" signifies full coverage.
*/
if (up->pcslen < up->len) {
if (0 < up->pcslen)
cscov = up->pcslen;
udp_hdr(skb)->len = htons(up->pcslen);
}
/*
* NOTE: Causes for the error case `up->pcslen > up->len':
* (i) Application error (will not be penalized).
* (ii) Payload too big for send buffer: data is split
* into several packets, each with its own header.
* In this case (e.g. last segment), coverage may
* exceed packet length.
* Since packets with coverage length > packet length are
* illegal, we fall back to the defaults here.
*/
}
skb->ip_summed = CHECKSUM_NONE; /* no HW support for checksumming */
skb_queue_walk(&sk->sk_write_queue, skb) {
@ -115,16 +109,21 @@ static inline __wsum udplite_csum_outgoing(struct sock *sk, struct sk_buff *skb)
return csum;
}
/* Fast-path computation of checksum. Socket may not be locked. */
static inline __wsum udplite_csum(struct sk_buff *skb)
{
struct sock *sk = skb->sk;
int cscov = udplite_sender_cscov(udp_sk(sk), udp_hdr(skb));
const struct udp_sock *up = udp_sk(skb->sk);
const int off = skb_transport_offset(skb);
const int len = skb->len - off;
int len = skb->len - off;
if ((up->pcflag & UDPLITE_SEND_CC) && up->pcslen < len) {
if (0 < up->pcslen)
len = up->pcslen;
udp_hdr(skb)->len = htons(up->pcslen);
}
skb->ip_summed = CHECKSUM_NONE; /* no HW support for checksumming */
return skb_checksum(skb, off, min(cscov, len), 0);
return skb_checksum(skb, off, len, 0);
}
extern void udplite4_register(void);