Commit c7d13c8f authored Jan 16, 2019 by Yuchung Cheng Committed by David S. Miller Jan 17, 2019

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>

parent 7ae18975

net/ipv4/tcp_timer.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -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);
		}

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