Commit cd736d8b authored May 13, 2019 by Yuchung Cheng Committed by David S. Miller May 14, 2019

tcp: fix retrans timestamp on passive Fast Open



Commit c7d13c8f ("tcp: properly track retry time on
passive Fast Open") sets the start of SYNACK retransmission
time on passive Fast Open in "retrans_stamp". However the
timestamp is not reset upon the handshake has completed. As a
result, future data packet retransmission may not update it in
tcp_retransmit_skb(). This may lead to socket aborting earlier
unexpectedly by retransmits_timed_out() since retrans_stamp remains
the SYNACK rtx time.

This bug only manifests on passive TFO sender that a) suffered
SYNACK timeout and then b) stalls on very first loss recovery. Any
successful loss recovery would reset the timestamp to avoid this
issue.

Fixes: c7d13c8f ("tcp: properly track retry time on passive Fast Open")
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 35c99ffa

net/ipv4/tcp_input.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -6024,6 +6024,9 @@ reset_and_undo:
		static void tcp_rcv_synrecv_state_fastopen(struct sock *sk)
		{
		tcp_try_undo_loss(sk, false);

		/* Reset rtx states to prevent spurious retransmits_timed_out() */
		tcp_sk(sk)->retrans_stamp = 0;
		inet_csk(sk)->icsk_retransmits = 0;

		/* Once we leave TCP_SYN_RECV or TCP_FIN_WAIT_1,

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