[PATCH] bpf: tcp_bpf_recvmsg should return EAGAIN when nonblocking and no data

[PATCH] bpf: tcp_bpf_recvmsg should return EAGAIN when nonblocking and no data

[John Fastabend]

We return 0 in the case of a nonblocking socket that has no data
available. However, this is incorrect and may confuse applications.
After this patch we do the correct thing and return the error
EAGAIN.

Quoting return codes from recvmsg manpage,

EAGAIN or EWOULDBLOCK
 The socket is marked nonblocking and the receive operation would
 block, or a receive timeout had been set and the timeout expired
 before data was received.

Signed-off-by: John Fastabend <john.fastabend@gmail.com>
---
 net/ipv4/tcp_bpf.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
index b7918d4..3b45fe5 100644
--- a/net/ipv4/tcp_bpf.c
+++ b/net/ipv4/tcp_bpf.c
@@ -145,6 +145,7 @@ int tcp_bpf_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 			ret = err;
 			goto out;
 		}
+		copied = -EAGAIN;
 	}
 	ret = copied;
 out:
-- 
1.9.1

Re: [PATCH] bpf: tcp_bpf_recvmsg should return EAGAIN when nonblocking and no data

[John Fastabend]

On 10/29/2018 12:31 PM, John Fastabend wrote:
> We return 0 in the case of a nonblocking socket that has no data
> available. However, this is incorrect and may confuse applications.
> After this patch we do the correct thing and return the error
> EAGAIN.
> 
> Quoting return codes from recvmsg manpage,
> 
> EAGAIN or EWOULDBLOCK
>  The socket is marked nonblocking and the receive operation would
>  block, or a receive timeout had been set and the timeout expired
>  before data was received.
> 
> Signed-off-by: John Fastabend <john.fastabend@gmail.com>
> ---

Add fixes tag.

Fixes: 604326b41a6f ("bpf, sockmap: convert to generic sk_msg interface")

Re: [PATCH] bpf: tcp_bpf_recvmsg should return EAGAIN when nonblocking and no data

[Song Liu]

On Mon, Oct 29, 2018 at 1:32 PM John Fastabend <john.fastabend@gmail.com> wrote:
>
> On 10/29/2018 12:31 PM, John Fastabend wrote:
> > We return 0 in the case of a nonblocking socket that has no data
> > available. However, this is incorrect and may confuse applications.
> > After this patch we do the correct thing and return the error
> > EAGAIN.
> >
> > Quoting return codes from recvmsg manpage,
> >
> > EAGAIN or EWOULDBLOCK
> >  The socket is marked nonblocking and the receive operation would
> >  block, or a receive timeout had been set and the timeout expired
> >  before data was received.
> >
> > Signed-off-by: John Fastabend <john.fastabend@gmail.com>

Acked-by: Song Liu <songliubraving@fb.com>

> > ---
>
> Add fixes tag.
>
> Fixes: 604326b41a6f ("bpf, sockmap: convert to generic sk_msg interface")
>
>
>
>

Re: [PATCH] bpf: tcp_bpf_recvmsg should return EAGAIN when nonblocking and no data

[Daniel Borkmann]

On 10/29/2018 08:31 PM, John Fastabend wrote:
> We return 0 in the case of a nonblocking socket that has no data
> available. However, this is incorrect and may confuse applications.
> After this patch we do the correct thing and return the error
> EAGAIN.
> 
> Quoting return codes from recvmsg manpage,
> 
> EAGAIN or EWOULDBLOCK
>  The socket is marked nonblocking and the receive operation would
>  block, or a receive timeout had been set and the timeout expired
>  before data was received.
> 
> Signed-off-by: John Fastabend <john.fastabend@gmail.com>

Applied to bpf, thanks!