Re: [reSIProcate] unresponsive DNS query blocks stack thread if USE_IPV6 is not defined (windows)

[Kennard White <kennard_white@xxxxxxxxxxxx>]

Hey guys,

I think I figured out why the code was setup for blocking under linux. There is a bug in the linux implementation of ares make_socket_non_blocking(). The line:
               if (fcntl(s, F_GETFL, &flags) == -1)

should be:
               if ( (flags  = fcntl( fd, F_GETFL, 0)) == -1 )

Reference rutil/Socket.cxx for comparison. (Though that function is missing the error checking).

Because of above bug, the set to nonblocking would fail under linux. Someone must have worked around this by getting rid of the nonblocking completely.

I didn't include patch since one-line fix.

Thanks,
Kennard

On Mon, Nov 1, 2010 at 7:34 AM, Justin Matthews <jmatthewsr@xxxxxxxxx> wrote:

Updated ares_process.c to set UDP sockets non-blocking for build configurations where they were previously blocking:

 

·         Windows where USE_IPV6 was not defined

·         All non-windows builds

 

-justin

 

From: slgodin@xxxxxxxxx [mailto:slgodin@xxxxxxxxx] On Behalf Of Scott Godin
Sent: Friday, October 29, 2010 8:05 PM
To: Justin Matthews
Cc: resiprocate-devel
Subject: Re: [reSIProcate] unresponsive DNS query blocks stack thread if USE_IPV6 is not defined (windows)

 

After a quick look, seems odd to me as well.  Also if non-windows we never set the UDP socket to non-blocking.  What I don't get is why people on linux have not noticed a blocking problem yet.  TCP DNS sockets seem to be set as non-blocking properly for linux and windows both with and without the USE_IPV6 directive.

 

Scott

On Fri, Oct 29, 2010 at 10:52 AM, Justin Matthews <jmatthewsr@xxxxxxxxx> wrote:

Hi,

Does anyone know if it's intended behavior for the ares UDP socket to block
if USE_IPV6 is not defined (Windows OS)?  In ares_process.c ,
open_udp_socket() will set the socket non-blocking only if USE_IPV6 is
defined.  If DNS is misconfigured or there is no response for a DNS record
lookup, the resip stack thread will block indefinitely in the recv() call in
read_udp_packets().

Thanks,

-justin

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