[SR-Users] [sr-dev] dns resolver issue (RFC3263)

[MÉSZÁROS Mihály]

Hi,

I made some progress. As I stated before, I made a patch and submitted 
to git branch misi/dns_srv.
I tested with dns cache. It works for me.

I made it also available for case if "no dns cache" is used too,
but it isn't tested yet.

Please review my commit, and let me know if any corrections needed.
Any suggestion, comment highly appreciated!

Please also let me know even if you find my code OK and i can merge it 
to the master.

Current status:
If there is no NAPTR record then based on the dns_/protocol/_pref scores 
it sort the list of the sr supported protocols,  and it tries protocols 
to resolve SRV.
It stops the loop and returns, if it founds the first most preferred and 
available/so DNS SRV exists for the protocol/ record.

I will appreciate if anyone can help me to explain how can i made future 
progress with this SRV issue.
My problem is, that i don't know how to iterate and fallback to other 
preferred and available protocols, so keep the state of the failed 
protocols.
How can i save state and fallback if the access the remote side with the 
currently selected SRV protocol failed so fall back to second,third.. 
available and preferred protocol.

Many thanks,
Misi

On 2012-11-05 15:03, Klaus Darilion wrote:
> Indeed, this is not implemented correctly.
>
> If you fix it, the question is: what should be used if there are SRV 
> records for UDP and TCP?
>
> AFAIK there is already a configuration option to choose the respective 
> NAPTR records according to local priority. These config options could 
> be reused.
>
> See dns_udp_pref/dns_tcp_pref/... options in doc/dns.txt
>
> regards
> Klaus
>
> On 29.10.2012 16:33, MÉSZÁROS Mihály wrote:
>> Hi All,
>>
>> I am experiencing an issue when i try to contact xy at cisco.com.
>> I found that kamailio/sip-router can't resolve by default resolving way
>> a TCP + SRV records from domain cisco.com.
>>
>> e.g. cisco.com
>>
>>     misi at alma:~$ host -t NAPTR cisco.com
>>     cisco.com has no NAPTR record
>>     misi at alma:~$ host -t SRV _sip._udp.cisco.com
>>     Host _sip._udp.cisco.com not found: 3(NXDOMAIN)
>>     misi at alma:~$ host -t SRV _sip._tcp.cisco.com
>>     _sip._tcp.cisco.com has SRV record 1 0 5060 vcsgw.cisco.com.
>>     misi at alma:~$ host -t SRV _sips._tcp.cisco.com
>>     _sips._tcp.cisco.com has SRV record 1 0 5061 vcsgw.cisco.com.
>>
>>
>> I can't call xy at cisco.com because it does not exists an NAPTR record in
>> domain cisco.com,
>> and furthermore no SRV with udp.
>>
>> But it exists sip+tcp record
>> and also exists an secure sip SRV, so sips+tcp record!
>>
>> I read rfc3263
>> I find kamailio dns resolver is not working as it should according 
>> RFC3263.
>>
>> http://tools.ietf.org/html/rfc3263
>>
>>     _If no NAPTR records are found, the client constructs SRV queries
>>     for those transport protocols it supports, and does a query for 
>> each._
>>
>>
>> So kamailio should query all (udp, tcp, tls, sctp whatever) protocols.
>>
>> Can anyone help/guide me to create a fix to this issue?
>> My plan is to create a patch to kamailio resolver, to correct and behave
>> according RFC3263.
>>
>> Any help or guidance appreciated!
>>
>> Thanks,
>> Misi
>>
>>
>>
>>
>>
>>
>> _______________________________________________
>> sr-dev mailing list
>> sr-dev at lists.sip-router.org
>> http://lists.sip-router.org/cgi-bin/mailman/listinfo/sr-dev
>>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.sip-router.org/pipermail/sr-users/attachments/20121112/bb9ca74f/attachment.htm>