2009/7/8 Klaus Darilion klaus.mailinglists@pernau.at:
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?
This is not RFC 3261 compliant. "received" MUST be added if the Via "sent-by" field is a domain/hostname, always.
dns=no: the "received" parameter is always added?
This is the correct behavior.