[Serusers] Rewriting URI in the Contact field

Folks, I need an advise on how to better implement one feature, which isn't currently present in SER. We need to allow UAs behind NAT properly register with the registrar - by "properly" I mean that host:port portion of URI in Contact field should not be used, but host:port the request came from should be used instead. By definition we know that those UAs will support symmetric SIP signalling, so that this scheme will work just fine. In my opinion there are two ways to do it: either add new rewritecontact* family of functions similar to rewritehost ones. or add a new flag for the save() function. This is where I need your help - which implementation looks better for you (or maybe you have even some better idea), since we are really interested in inclusion of our changes into the mainline to reduce our local hacks. Regards, Maxim