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>

diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index 1e61f0bd6e2431b39a188eef83945943cf92855f..074de38bafbda0c9bf753190d8d1b060face3527 100644 (file)
--- 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);
 }