Commit 2c7269b2 authored Jun 10, 2020 by Sabrina Dubroca Committed by Alexei Starovoitov Jun 12, 2020

bpf: tcp: Recv() should return 0 when the peer socket is closed



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: 604326b4 ("bpf, sockmap: convert to generic sk_msg interface")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/bpf/26038a28c21fea5d04d4bd4744c5686d3f2e5504.1591784177.git.sd@queasysnail.net

parent 2c4779ef

net/ipv4/tcp_bpf.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -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;

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