From: Jakub Sitnicki <jakub@cloudflare.com>
To: Sabrina Dubroca <sd@queasysnail.net>
Cc: netdev@vger.kernel.org, John Fastabend <john.fastabend@gmail.com>,
Daniel Borkmann <daniel@iogearbox.net>,
bpf@vger.kernel.org
Subject: Re: [PATCH bpf] bpf: tcp: recv() should return 0 when the peer socket is closed
Date: Fri, 12 Jun 2020 12:15:26 +0200 [thread overview]
Message-ID: <20200612121526.4810a073@toad> (raw)
In-Reply-To: <26038a28c21fea5d04d4bd4744c5686d3f2e5504.1591784177.git.sd@queasysnail.net>
On Wed, 10 Jun 2020 12:19:43 +0200
Sabrina Dubroca <sd@queasysnail.net> wrote:
> If the peer is closed, we will never get more data, so
> tcp_bpf_wait_data will get stuck forever. In case we passed
> MSG_DONTWAIT to recv(), we get EAGAIN but we should actually get
> 0.
>
> From man 2 recv:
>
> RETURN VALUE
>
> When a stream socket peer has performed an orderly shutdown, the
> return value will be 0 (the traditional "end-of-file" return).
>
> This patch makes tcp_bpf_wait_data always return 1 when the peer
> socket has been shutdown. Either we have data available, and it would
> have returned 1 anyway, or there isn't, in which case we'll call
> tcp_recvmsg which does the right thing in this situation.
>
> Fixes: 604326b41a6f ("bpf, sockmap: convert to generic sk_msg interface")
> Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
> ---
> net/ipv4/tcp_bpf.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
> index 2b915aafda42..7aa68f4aae6c 100644
> --- a/net/ipv4/tcp_bpf.c
> +++ b/net/ipv4/tcp_bpf.c
> @@ -245,6 +245,9 @@ static int tcp_bpf_wait_data(struct sock *sk, struct sk_psock *psock,
> DEFINE_WAIT_FUNC(wait, woken_wake_function);
> int ret = 0;
>
> + if (sk->sk_shutdown & RCV_SHUTDOWN)
> + return 1;
> +
> if (!timeo)
> return ret;
>
Acked-by: Jakub Sitnicki <jakub@cloudflare.com>
next prev parent reply other threads:[~2020-06-12 10:15 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-10 10:19 [PATCH bpf] bpf: tcp: recv() should return 0 when the peer socket is closed Sabrina Dubroca
2020-06-12 10:15 ` Jakub Sitnicki [this message]
2020-06-12 22:13 ` Alexei Starovoitov
2020-06-12 22:52 ` John Fastabend
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200612121526.4810a073@toad \
--to=jakub@cloudflare.com \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=john.fastabend@gmail.com \
--cc=netdev@vger.kernel.org \
--cc=sd@queasysnail.net \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).