This is the mail archive of the
libc-alpha@sourceware.org
mailing list for the glibc project.
Re: [PATCH] resolv_test.c: also cope with CONNREFUSED errors returned by recvfrom
Florian Weimer, on lun. 25 sept. 2017 10:20:46 +0200, wrote:
> 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.
Running Linux 4.13
$ strace nc localhost 12345 -u
...
sendmsg(3, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="kljsdf\n", iov_len=7}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, 0) = 7
select(5, [3 4], [], NULL, NULL) = 1 (in [3])
recvmsg(3, {msg_namelen=0}, 0) = -1 ECONNREFUSED (Connection refused)
Samuel