[sr-dev] dns resolver issue (RFC3263)

MÉSZÁROS Mihály misi at niif.hu
Tue Nov 6 13:31:23 CET 2012


Dear Klaus et al.

Exactly the same was in my mind.
So my plan is to sort the protocols using these dns_PROTO_pref values.
If the pref is the same to all protocols,
(like it should according to the RFC3263 dns lookup process)
then the order will be udp,tcp,tls,sctp.

Any other suggestions are welcome!

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
>>




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