asterisk users - Oct 2008 - srv records not being honoured properly

Given the following SRV records:

_sip._udp.tollfree.sip-happens.com. 38400 IN SRV 10 0 5060
sometimes.sip-happens.com.
_sip._udp.tollfree.sip-happens.com. 38400 IN SRV 20 0 5070 ares.sip-happens.com.

Why is asterisk (1.4.17) not honouring the priority and not failing over
to using other records when a connection fails?

For a given call to tollfree.sip-happens.com ares.sip-happens.com was
chosen and tried before sometimes.sip-happens.com and additionally, when
the connection to ares.sip-happens.com was being refused there was no
roll-over to sometimes.sip-happens.  Here's what asterisk did:

    -- Executing [s at macro-enumdial:23]
Dial("SIP/anonymous-b5e02fd0", "SIP/18771234567 at
tollfree.sip-happens.com.||") in new stack
    -- ast_get_srv: SRV lookup for '_sip._udp.tollfree.sip-happens.com.'
mapped to host ares.sip-happens.com, port 5070
    -- Called 18771234567 at tollfree.sip-happens.com.
[Oct 17 10:15:46] NOTICE[4973]: chan_sip.c:2920 auto_congest: Auto-congesting
SIP/tollfree.sip-happens.com.-081ddc28
    -- SIP/tollfree.sip-happens.com.-081ddc28 is circuit-busy
  == Everyone is busy/congested at this time (1:0/1/0)

And here's the packet trace:

10:15:16.612062 IP 67.193.213.184.5060 > 209.9.237.93.5070: SIP, length: 855
10:15:16.652721 IP 209.9.237.93 > 67.193.213.184: ICMP 209.9.237.93 udp port
5070 unreachable, length 556
10:15:17.613997 IP 67.193.213.184.5060 > 209.9.237.93.5070: SIP, length: 855
10:15:17.654697 IP 209.9.237.93 > 67.193.213.184: ICMP 209.9.237.93 udp port
5070 unreachable, length 556
10:15:18.611068 IP 67.193.213.184.5060 > 209.9.237.93.5070: SIP, length: 855
10:15:18.652786 IP 209.9.237.93 > 67.193.213.184: ICMP 209.9.237.93 udp port
5070 unreachable, length 556
10:15:20.614106 IP 67.193.213.184.5060 > 209.9.237.93.5070: SIP, length: 855
10:15:20.654785 IP 209.9.237.93 > 67.193.213.184: ICMP 209.9.237.93 udp port
5070 unreachable, length 556
10:15:24.614115 IP 67.193.213.184.5060 > 209.9.237.93.5070: SIP, length: 855
10:15:24.658934 IP 209.9.237.93 > 67.193.213.184: ICMP 209.9.237.93 udp port
5070 unreachable, length 556
10:15:32.615275 IP 67.193.213.184.5060 > 209.9.237.93.5070: SIP, length: 855
10:15:32.668930 IP 209.9.237.93 > 67.193.213.184: ICMP 209.9.237.93 udp port
5070 unreachable, length 556
10:15:48.614675 IP 67.193.213.184.5060 > 209.9.237.93.5070: SIP, length: 855
10:15:48.655403 IP 209.9.237.93 > 67.193.213.184: ICMP 209.9.237.93 udp port
5070 unreachable, length 556

So, as you can see, the priority was not honoured, nor was the alternate
SRV record used when there was a connection failure.  Maybe that's
because it was looking for a lower priority.  Is SRV handling in
Asterisk just broken?  Or is this a known and fixed bug?

b.

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Brian J. Murrell wrote:
>Given the following SRV records:
>
>_sip._udp.tollfree.sip-happens.com. 38400 IN SRV 10 0 5060
sometimes.sip-happens.com.
>_sip._udp.tollfree.sip-happens.com. 38400 IN SRV 20 0 5070
ares.sip-happens.com.
>
>Why is asterisk (1.4.17) not honouring the priority and not failing over
>to using other records when a connection fails?
>
>  
>
Because Asterisk does not support that.  The only thing that Asterisk 
does is use the first SRV entry but it pays no attention to priorities 
or weights.  It does not care about other SRV entries either.  This is 
how things have been as long as I can remember.  I am not sure about 
version 1.6 though.

Andres
http://www.neuroredes.com
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On Fri, 2008-10-17 at 10:32 -0500, Andres wrote:
> 
> Because Asterisk does not support that.
Which is just another way of saying Asterisk is broken then.  SRV
records have requirements for their correct use.  If those requirements
are ignored, that is a broken implementation.
> The only thing that Asterisk 
> does is use the first SRV entry
First in terms of what was returned, not sorted by priority and weight,
right?
> but it pays no attention to priorities 
> or weights.  It does not care about other SRV entries either.
Tsk tsk tsk.
> This is 
> how things have been as long as I can remember.
Wonderful.  Nothing like half implementing standards.

b.

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It should be fairly easy to write an AGI script that does the SRV query, 
  do whatever you want with the response, set a channel variable with 
the results and use that in your dialplan.

Brian J. Murrell wrote:
> On Fri, 2008-10-17 at 10:32 -0500, Andres wrote:
>> Because Asterisk does not support that.
> 
> Which is just another way of saying Asterisk is broken then.  SRV
> records have requirements for their correct use.  If those requirements
> are ignored, that is a broken implementation.
> 
>> The only thing that Asterisk 
>> does is use the first SRV entry
> 
> First in terms of what was returned, not sorted by priority and weight,
> right?
> 
>> but it pays no attention to priorities 
>> or weights.  It does not care about other SRV entries either.
> 
> Tsk tsk tsk.
> 
>> This is 
>> how things have been as long as I can remember.
> 
> Wonderful.  Nothing like half implementing standards.

-- 
Consulting and design services for LAN, WAN, voice and data.  Based near 
Birmingham, AL.  Now accepting clients worldwide. Contact me for Tellabs 
echo canceling systems.  Also see http://www.fnords.org/skillslist.html

On Fri, 2008-10-17 at 11:18 -0500, Eric "ManxPower" Wieling
wrote:
> It should be fairly easy to write an AGI script that does the SRV query, 
>   do whatever you want with the response, set a channel variable with 
> the results and use that in your dialplan.
Maybe.  If I were an AGI hacker.  But really, should I (and every other
Asterisk user) have to?

b.

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