[sr-dev] dns= and rev_dns= parameter

[Klaus Darilion]

Andrei Pelinescu-Onciul schrieb:
> On Jul 08, 2009 at 10:58, Klaus Darilion <klaus.mailinglists at pernau.at> wrote:
>> Thanks!
>>
>> Just for clarification:
>>
>>> dns
>>>
>>> This parameter controls if the SIP server will try doing a DNS lookup
>>> on the address in the Via header of a received sip request to decide
>>> if adding a received=<src_ip> parameter to the Via is necessary. Note
>>> that Vias containing DNS names (instead of IPs) should have received=
>>> added, so turning dns to yes is not recommended.
>>>
>>> Default is no.
>> Does this mean that, if the Via header in the received message contains 
>> a domain and:
>>
>> dns=yes, a lookup is done, and if the domain resolves to the src_ip, 
>> then the "received" parameter is not added, but only added when the 
>> domain resolves to a different IP address?
> 
> Yes.
>> dns=no: the "received" parameter is always added?
> 
> Yes, if the address in Via is a DNS name and not an IP (and this is the
> recommended behaviour according to the rfc).
> 
>> What about the behavior when the Via header contains an IP address (does 
>> this parameter affects the behavior)? Is the "received" parameter always 
>> added, or only if it Via-IP differs from source-IP? What about existing 
>> "received" parameter - will they be deleted/overwritten.
> 
> If the Via contains an IP, received is only added if the Via-IP!=src_IP.
> 
>> I ask because some time ago we had problems in Kamailio.
> 
> I think they do exactly the same thing in kamailio. These config params.
> are very old, from the early days of ser and I doubt anyone touched
> them.


I found the issue - this can be relevant for sr too:
https://sourceforge.net/tracker/?func=detail&atid=743020&aid=2002156&group_id=139143

regards
klaus