[Kamailio-Users] handling of DNS-SRV in kamailio-1.4.3 & 1.5.0

Daniel-Constantin Mierla miconda at gmail.com
Tue Mar 10 12:32:46 CET 2009 

Hello Klaus,

please register the issue in the tracker so it does not get lost in the 
mailing list. Please put there the content of this last email:
http://sourceforge.net/tracker/?atid=743020&group_id=139143&func=browse

Thanks,
Daniel


On 03/09/2009 04:41 PM, Klaus Feichtinger wrote:
> Hello Daniel,
>
> I've done several test with different scenarios:
>
> 1) including 4 hosts in the answer of the SRV reply message; the 1st and 2nd host are unreachable, the third an fourth are reachable - the SIP message never reached the target (= host 3)
>
> 2) including 4 hosts in the answer of the SRV reply message; the SIP service is not running on the first and second host; the third and fourth have the service activated - the SIP message is transmitted to the second host after the fr_timeout of the TM module, but is not forwarded to the target (= host 3); it is retransmitted to host 2 until SIP timeout
>
> The conclusion is: when only on master and slave are in the answer of the SRV reply message it works fine. But starting with the third host the service hangs on the second host and does not try reaching an alternative target (as listed in the SRV response).
>
> In the syslog I can only see entries like this (but no ERROR message):
>
> Mar  9 15:36:21 lennysrv /usr/local/sbin/kamailio[25041]: DBG:core:mk_proxy: doing DNS lookup...
> Mar  9 15:36:21 lennysrv /usr/local/sbin/kamailio[25041]: DBG:core:a2dns_node: storing kamailio2.test.loc:5080
> Mar  9 15:36:21 lennysrv /usr/local/sbin/kamailio[25041]: DBG:core:a2dns_node: storing kamailio3.test.loc:5060
> Mar  9 15:36:26 lennysrv /usr/local/sbin/kamailio[25043]: DBG:core:mk_proxy: doing DNS lookup...
> Mar  9 15:36:28 lennysrv /usr/local/sbin/kamailio[25047]: DBG:tm:is_3263_failure: dns-failover test: branch=0, last_recv=408, flags=1
> Mar  9 15:36:28 lennysrv /usr/local/sbin/kamailio[25047]: DBG:tm:t_should_relay_response: trying DNS-based failover
> Mar  9 15:36:28 lennysrv /usr/local/sbin/kamailio[25047]: DBG:tm:do_dns_failover: new destination available
> Mar  9 15:36:31 lennysrv /usr/local/sbin/kamailio[25047]: DBG:tm:is_3263_failure: dns-failover test: branch=1, last_recv=408, flags=1
> Mar  9 15:36:31 lennysrv /usr/local/sbin/kamailio[25047]: DBG:tm:t_should_relay_response: trying DNS-based failover
> Mar  9 15:36:31 lennysrv /usr/local/sbin/kamailio[25047]: DBG:tm:do_dns_failover: new destination available
> Mar  9 15:36:34 lennysrv /usr/local/sbin/kamailio[25047]: DBG:tm:is_3263_failure: dns-failover test: branch=2, last_recv=408, flags=1
> Mar  9 15:36:34 lennysrv /usr/local/sbin/kamailio[25047]: DBG:tm:t_should_relay_response: trying DNS-based failover
> Mar  9 15:36:34 lennysrv /usr/local/sbin/kamailio[25047]: DBG:tm:do_dns_failover: new destination available
> Mar  9 15:36:37 lennysrv /usr/local/sbin/kamailio[25047]: DBG:tm:is_3263_failure: dns-failover test: branch=3, last_recv=408, flags=1
> Mar  9 15:36:37 lennysrv /usr/local/sbin/kamailio[25047]: DBG:tm:t_should_relay_response: trying DNS-based failover
> Mar  9 15:36:37 lennysrv /usr/local/sbin/kamailio[25047]: DBG:tm:do_dns_failover: new destination available
> Mar  9 15:36:40 lennysrv /usr/local/sbin/kamailio[25047]: DBG:tm:is_3263_failure: dns-failover test: branch=4, last_recv=408, flags=1
> Mar  9 15:36:40 lennysrv /usr/local/sbin/kamailio[25047]: DBG:tm:t_should_relay_response: trying DNS-based failover
> Mar  9 15:36:40 lennysrv /usr/local/sbin/kamailio[25047]: DBG:tm:do_dns_failover: new destination available
> Mar  9 15:36:43 lennysrv /usr/local/sbin/kamailio[25045]: DBG:tm:is_3263_failure: dns-failover test: branch=5, last_recv=487, flags=1
>
> The syslog output seems to be okay, because kamailio theoretically makes a dns_failover. But practically it is only sent to the first and second target.
>
>
> Do you have any other idea what could be wrong? I haven't found any specific parameters that could influence this behaviour of kamailio....
>
> regards,
>
> Klaus F.
>
>
> -------- Original-Nachricht --------
>   
>> Datum: Fri, 06 Mar 2009 10:59:28 +0200
>> Von: Daniel-Constantin Mierla <miconda at gmail.com>
>> An: Klaus Feichtinger <klaus.feichtinger at gmx.net>
>> CC: users at lists.kamailio.org
>> Betreff: Re: [Kamailio-Users] handling of DNS-SRV in kamailio-1.4.3 & 1.5.0
>>     
>
>   
>> Hello,
>>
>> On 03/05/2009 02:51 PM, Klaus Feichtinger wrote:
>>     
>>> Hello,
>>>
>>> I have to relay SIP requests to a special "redundant" destination (=
>>>       
>> FQDN - e.g. "test.kamailio.loc") that consists of 3 hosts with different
>> priorities.
>>     
>>> After startup Kamailio creates a DNS-SRV request to the DNS server and
>>>       
>> receives a response with following answer (e.g.):
>>     
>>>    _sip._udp.test.kamailio.loc: type SRV, class IN, priority 10, weight
>>>       
>> 100, port 5060, target host1.test.kamailio.loc
>>     
>>>    _sip._udp.test.kamailio.loc: type SRV, class IN, priority 20, weight
>>>       
>> 90, port 5060, target host2.test.kamailio.loc
>>     
>>>    _sip._udp.test.kamailio.loc: type SRV, class IN, priority 30, weight
>>>       
>> 80, port 5060, target host3.test.kamailio.loc
>>     
>>> In worst case - if the prime and secondary host (host1 and host2) are
>>>       
>> unavailable - I expect that kamailio tries relaying the request to the third
>> host in the list. But it doesn't. It makes retransmission of the original
>> invite to the second host and does not try reaching the third host. 
>>     
>>> For tuning the switchover to the alternative target(2) I have set the
>>>       
>> module parameter "fr_timer" for TM to 3 seconds (modparam("tm", "fr_timer",
>> 3)).
>>     
>>> Is this behaviour of Kamailio-1.4.3 and Kamailio-1.5.0 (I've tested it
>>>       
>> with both versions) as expected (= limited to support only two answers in a
>> DNS SRV reply)? Does anybody have experience with this scenario? Can
>> anybody give me a hint?
>>     
>>>   
>>>       
>> should be no such limitation. If you try with 4 hosts what happens? Do 
>> you get any errors in the syslog?
>>
>> Cheers,
>> Daniel
>>
>> -- 
>> Daniel-Constantin Mierla
>> http://www.asipto.com
>>     
>
>   

-- 
Daniel-Constantin Mierla
http://www.asipto.com

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