[sr-dev] dns resolver issue (RFC3263)

[MÉSZÁROS Mihály]

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




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