On Wed, 10 Jun 2020 12:19:43 +0200
Sabrina Dubroca <sd@xxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxx>
> ---
> 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@xxxxxxxxxxxxxx>
