Commit c5715b8f authored Jan 08, 2019 by Yuchung Cheng Committed by David S. Miller Jan 10, 2019

tcp: change txhash on SYN-data timeout



Previously upon SYN timeouts the sender recomputes the txhash to
try a different path. However this does not apply on the initial
timeout of SYN-data (active Fast Open). Therefore an active IPv6
Fast Open connection may incur one second RTO penalty to take on
a new path after the second SYN retransmission uses a new flow label.

This patch removes this undesirable behavior so Fast Open changes
the flow label just like the regular connections. This also helps
avoid falsely disabling Fast Open on the sender which triggers
after two consecutive SYN timeouts on Fast Open.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent ea89098e

net/ipv4/tcp_timer.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -226,7 +226,7 @@ static int tcp_write_timeout(struct sock *sk)
		if ((1 << sk->sk_state) & (TCPF_SYN_SENT \| TCPF_SYN_RECV)) {
		if (icsk->icsk_retransmits) {
		dst_negative_advice(sk);
		} else if (!tp->syn_data && !tp->syn_fastopen) {
		} else {
		sk_rethink_txhash(sk);
		}
		retry_until = icsk->icsk_syn_retries ? : net->ipv4.sysctl_tcp_syn_retries;

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