Re: [PATCH] resolv_test.c: also cope with CONNREFUSED errors returned by recvfrom

[Florian Weimer <fweimer at redhat dot com>]

On 09/25/2017 09:38 AM, Samuel Thibault wrote:
> Florian Weimer, on lun. 25 sept. 2017 09:31:02 +0200, wrote:
> > On 09/10/2017 04:38 PM, Samuel Thibault wrote:
> > > +  if (length < 0)
> > > +    {
> > > +      /* The other end had closed the socket, and we are notified only now. */
> > > +      TEST_VERIFY_EXIT (errno == ECONNREFUSED);
> > > +      return true;
> > > +    }
> >
> > Sorry for not replying sooner.
> >
> > This UDP socket is unconnected.  If asynchronous error notifications are
> > received on it, this is arguably a TCP/IP stack bug.
>
> Reception of "port unreachable" icmp packets can be asynchronous with
> UDP too.

Stevens says that this can happen on connected sockets only.  Both TCPv2 
and UNIX Network Programming have detailed explanations.  I can 
summarize those if you don't have access.

The only quoted exception is Linux, but the kernel behavior changed 
around 2.4.0.

Thanks,
Florian