tcp: properly track retry time on passive Fast Open

This patch addresses a corner issue on timeout behavior of a
passive Fast Open socket.  A passive Fast Open server may write
and close the socket when it is re-trying SYN-ACK to complete
the handshake. After the handshake is completely, the server does
not properly stamp the recovery start time (tp->retrans_stamp is
0), and the socket may abort immediately on the very first FIN
timeout, instead of retying until it passes the system or user
specified limit.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 0 deletions

diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index 1e61f0bd6e24..074de38bafbd 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -378,6 +378,7 @@ static void tcp_fastopen_synack_timer(struct sock *sk)
         struct inet_connection_sock *icsk = inet_csk(sk);
         int max_retries = icsk->icsk_syn_retries ? :
             sock_net(sk)->ipv4.sysctl_tcp_synack_retries + 1; /* add one more retry for fastopen */
+        struct tcp_sock *tp = tcp_sk(sk);
         struct request_sock *req;
 
         req = tcp_sk(sk)->fastopen_rsk;
@@ -395,6 +396,8 @@ static void tcp_fastopen_synack_timer(struct sock *sk)
         inet_rtx_syn_ack(sk, req);
         req->num_timeout++;
         icsk->icsk_retransmits++;
+        if (!tp->retrans_stamp)
+                tp->retrans_stamp = tcp_time_stamp(tp);
         inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
                           TCP_TIMEOUT_INIT << req->num_timeout, TCP_RTO_MAX);
 }