[asterisk-bugs] [Asterisk 0015738]: chan_sip lockup by DNS and connect timeouts

[Asterisk Bug Tracker]

A NOTE has been added to this issue. 
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https://issues.asterisk.org/view.php?id=15738 
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Reported By:                kmuenning
Assigned To:                
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Project:                    Asterisk
Issue ID:                   15738
Category:                   Channels/chan_sip/General
Reproducibility:            always
Severity:                   major
Priority:                   normal
Status:                     new
Asterisk Version:           Older 1.6.1 
Regression:                 No 
SVN Branch (only for SVN checkouts, not tarball releases): N/A 
SVN Revision (number only!):  
Request Review:              
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Date Submitted:             2009-08-18 09:33 CDT
Last Modified:              2009-08-18 10:00 CDT
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Summary:                    chan_sip lockup by DNS and connect timeouts
Description: 
This seems to be related to issue https://issues.asterisk.org/view.php?id=9536
but as it is closed I have to open
a new bug. This is a major issue as the disruption of the internet
connection caused a complete service disruption which was not happening
with asterisk 1.2.x I was using until few weeks ago for which it seems to
have been fixed, according to the issue above.

I am now using asterisk-1.6.1.1-r1 on Gentoo with several external SIP
accounts and a mISDN local line. This night my internet connection went
down and as a result all SIP phones went offline as they could not register
to asterisk. I assume the reason is that chan_sip was stuck in DNS lookups
to send registration requests to external SIP providers and was not
responding to SIP requests from the phones. A SIP debug or verbosity
setting was not showing anything from the phones (as probably chan_sip did
not process the debug request) but tcpdump was showing that requests were
sent. The only messages appearing were like:

[Aug 18 09:56:27] NOTICE[13801] chan_sip.c:    -- Registration for
'xxxx at nikotel-zyxel' timed out, trying again (Attempt
https://issues.asterisk.org/view.php?id=4)
[Aug 18 09:56:27] WARNING[13801] chan_sip.c: Probably a DNS error for
registration to xxxx at nikotel-zyxel, trying REGISTER again (after 20
seconds)

I had to kill asterisk as issuing a restart gracefully just hung CLI.
Probably as chan_sip was not responding to that either. When asterisk was
restarted, above warning started appearing again but no CLI sip channel
commands were possible (word sip was not recognized) - probably channel was
not yet initialized. After adding the domain names asterisk had to lookup
in local hosts file sip channel was up and phones registered so at least
local and ISDN connections were working again. After internet was up again
I could delete the hosts lines and everything was OK again.

So chan_sip should not block in such cases (as probably was fixed with
issue mentioned above) so other communication can continue in case of
internet/DNS failure.
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 (0109209) aragon (reporter) - 2009-08-18 10:00
 https://issues.asterisk.org/view.php?id=15738#c109209 
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Interesting...

I was debugging bug 15109 with valgrind running and noticed some funky dns
stuff
valgrind17082009.txt attached 

Issue History 
Date Modified    Username       Field                    Change               
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2009-08-18 10:00 aragon         Note Added: 0109209                          
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