On Tue, Apr 18, 2017 at 9:45 AM, Eric Dumazet <eduma...@google.com> wrote:
>
> When using TCP FastOpen for an active session, we send one wakeup event
> from tcp_finish_connect(), right before the data eventually contained in
> the received SYNACK is queued to sk->sk_receive_queue.
>
> This means that depending on machine load or luck, poll() users
> might receive POLLOUT events instead of POLLIN|POLLOUT
>
> To fix this, we need to move the call to sk->sk_state_change()
> after the (optional) call to tcp_rcv_fastopen_synack()
>
> Signed-off-by: Eric Dumazet <eduma...@google.com>
Acked-by: Yuchung Cheng <ych...@google.com>
Thanks for the fix!
> ---
> net/ipv4/tcp_input.c | 16 +++++++++-------
> 1 file changed, 9 insertions(+), 7 deletions(-)
>
> diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
> index
> 37e2aa925f62395cfb48145cd3a76b6afebb64b1..341f021f02a2931cd75b2e1e71af9729fc4c7895
> 100644
> --- a/net/ipv4/tcp_input.c
> +++ b/net/ipv4/tcp_input.c
> @@ -5580,10 +5580,6 @@ void tcp_finish_connect(struct sock *sk, struct
> sk_buff *skb)
> else
> tp->pred_flags = 0;
>
> - if (!sock_flag(sk, SOCK_DEAD)) {
> - sk->sk_state_change(sk);
> - sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
> - }
> }
>
> static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,
> @@ -5652,6 +5648,7 @@ static int tcp_rcv_synsent_state_process(struct sock
> *sk, struct sk_buff *skb,
> struct tcp_sock *tp = tcp_sk(sk);
> struct tcp_fastopen_cookie foc = { .len = -1 };
> int saved_clamp = tp->rx_opt.mss_clamp;
> + bool fastopen_fail;
>
> tcp_parse_options(skb, &tp->rx_opt, 0, &foc);
> if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
> @@ -5755,10 +5752,15 @@ static int tcp_rcv_synsent_state_process(struct sock
> *sk, struct sk_buff *skb,
>
> tcp_finish_connect(sk, skb);
>
> - if ((tp->syn_fastopen || tp->syn_data) &&
> - tcp_rcv_fastopen_synack(sk, skb, &foc))
> - return -1;
> + fastopen_fail = (tp->syn_fastopen || tp->syn_data) &&
> + tcp_rcv_fastopen_synack(sk, skb, &foc);
>
> + if (!sock_flag(sk, SOCK_DEAD)) {
> + sk->sk_state_change(sk);
> + sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
> + }
> + if (fastopen_fail)
> + return -1;
> if (sk->sk_write_pending ||
> icsk->icsk_accept_queue.rskq_defer_accept ||
> icsk->icsk_ack.pingpong) {
> --
> 2.12.2.762.g0e3151a226-goog
>
