On Wed, Apr 12, 2017 at 01:54:41AM +0530, Deepak Khandelwal wrote:
> Hi,
>
Please don't top post..
>
> App act as client (1-1 Style SOCK_STREAM)
> App try to send 278 bytes of message.
Okay.
>
> So you mean that, if socket has space for few bytes (say 1 or 2
> bytes), lksctp will set POLLOUT event for fd,
> but since user application doesn;t know the underlying socket space
> available, it can write more than that but will fail with EAGAIN ?
Was reading the code again on this, I actually don't think this can
happen. The sleep on waiting for sndbuf doesn't check for msgsize, just
if there is any amount of buffer available or not.
sctp_sendmsg()
{
...
timeo = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT);
if (!sctp_wspace(asoc)) {
err = sctp_wait_for_sndbuf(asoc, &timeo, msg_len);
if (err)
goto out_free;
}
...
}
For returning -EAGAIN due to sndbuf, it has to match !sctp_wspace, which
is only about the soc/asoc and not the message. The EAGAIN in this case
comes from inside sctp_wait_for_sndbuf().
That leads us to my other question, are you binding/connecting this
socket before sending the message?
>
>
> Best Regards,
> Deepak
>
> On Wed, Apr 12, 2017 at 12:44 AM, Michael Tuexen
> <Michael.Tuexen@xxxxxxxxxxxxxxxxx> wrote:
> >> On 11. Apr 2017, at 21:08, Deepak Khandelwal <dazz.87@xxxxxxxxx> wrote:
> >>
> >> Hi,
> >>
> >> I am using 4.4.x kernel.
> >>
> >> in context of LKSCTP, what could be the possible reasons that poll or
> >> select on fd return false positive events, causing application do
> >> write on fd but failed with EAGAIN ?
> > I'm just guessing here... What if you can write something, but not
> > something big as you try...
> > So how big is the message you are trying so send?
> >
> > Best regards
> > Michael
> >>
> >>
> >> Best Regards,
> >> Deepak
> >> --
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