netdev - Re: [PATCH net] tcp: allow MSG_ZEROCOPY transmission also in CLOSE

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Date:   Thu, 10 Jan 2019 14:45:09 -0500
From:   Soheil Hassas Yeganeh <soheil@...gle.com>
To:     Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc:     netdev <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Marek Majkowski <marek@...udflare.com>,
        Yuchung Cheng <ycheng@...gle.com>,
        Neal Cardwell <ncardwell@...gle.com>,
        Alexey Kodanev <alexey.kodanev@...cle.com>
Subject: Re: [PATCH net] tcp: allow MSG_ZEROCOPY transmission also in
 CLOSE_WAIT state

On Thu, Jan 10, 2019 at 2:40 PM Willem de Bruijn
<willemdebruijn.kernel@...il.com> wrote:
>
> From: Willem de Bruijn <willemb@...gle.com>
>
> TCP transmission with MSG_ZEROCOPY fails if the peer closes its end of
> the connection and so transitions this socket to CLOSE_WAIT state.
>
> Transmission in close wait state is acceptable. Other similar tests in
> the stack (e.g., in FastOpen) accept both states. Relax this test, too.
>
> Link: https://www.mail-archive.com/netdev@vger.kernel.org/msg276886.html
> Link: https://www.mail-archive.com/netdev@vger.kernel.org/msg227390.html
> Fixes: f214f915e7db ("tcp: enable MSG_ZEROCOPY")
> Reported-by: Marek Majkowski <marek@...udflare.com>
> Signed-off-by: Willem de Bruijn <willemb@...gle.com>
> CC: Yuchung Cheng <ycheng@...gle.com>
> CC: Neal Cardwell <ncardwell@...gle.com>
> CC: Soheil Hassas Yeganeh <soheil@...gle.com>
> CC: Alexey Kodanev <alexey.kodanev@...cle.com>

Acked-by: Soheil Hassas Yeganeh <soheil@...gle.com>

Thank you for the fix!

> ---
>
> This is a narrow fix. Alexey Kodanev suggested a while ago that the
> entire check might be removed, also opening up more cases for zerocopy
> with fastopen. For net-next, I will take another look at that and also
> at adding a tcp_data_sending_states() helper to avoid open coding this
> test everywhere.
> ---
>  net/ipv4/tcp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index 27e2f6837062..2079145a3b7c 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -1186,7 +1186,7 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
>         flags = msg->msg_flags;
>
>         if (flags & MSG_ZEROCOPY && size && sock_flag(sk, SOCK_ZEROCOPY)) {
> -               if (sk->sk_state != TCP_ESTABLISHED) {
> +               if ((1 << sk->sk_state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)) {
>                         err = -EINVAL;
>                         goto out_err;
>                 }
> --
> 2.20.1.97.g81188d93c3-goog
>