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tcp: reset timer after any SYNACK retransmit

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Linux immediately returns SYNACK on (spurious) SYN retransmits, but
keeps the SYNACK timer running independently. Thus the timer may
fire right after the SYNACK retransmit and causes a SYN-SYNACK
cross-fire burst.

Adopt the fast retransmit/recovery idea in established state by
re-arming the SYNACK timer after the fast (SYNACK) retransmit. The
timer may fire late up to 500ms due to the current SYNACK timer wheel,
but it's OK to be conservative when network is congested. Eric's new
listener design should address this issue.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Yuchung Cheng 2013-04-29 08:44:51 +00:00 committed by David S. Miller
parent 6a5dc9e598
commit cd75eff64d
1 changed files with 6 additions and 1 deletions
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7
net/ipv4/tcp_minisocks.c
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@ -551,8 +551,13 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
*
* Note that even if there is new data in the SYN packet
* they will be thrown away too.
*
* Reset timer after retransmitting SYNACK, similar to
* the idea of fast retransmit in recovery.
*/
inet_rtx_syn_ack(sk, req);
if (!inet_rtx_syn_ack(sk, req))
req->expires = min(TCP_TIMEOUT_INIT << req->num_timeout,
TCP_RTO_MAX) + jiffies;
return NULL;
}