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>

diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index f87dbc78b6bcb85e12b72bdf57679a36440bb5bf..71a29e9c06206f3826296515d81ab5c010d222e7 100644 (file)
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -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;