[Serusers] symmetric nat/ broadband routers

Howdy! I'm having some trouble with the nathelper module and certain types of broadband routers (ie d-link 604 & d-link 624). I'll try to explain the situation below and hope that someone is willing to help me out, because i'm stuck. In short, the setup is a ata-186 box (which is symmetric) behind a d-link 604 (which isn't symmetric at all times). The nathelper module included in the distribution (both 0.8.11 and 0.8.12) has a function called fix_nated_contact(). fix_nated_contact() rewrites the contact-header with the source-ip & source-port of the packet. However, in some cases (ie non-symmetric d-link router between the ata-box and the internet) this is a problem since the d-link router sometimes rewrites the source-port which is then used as a location in ser. When the session has timed out on the d-link (doesn't really seem to help with the natping) the location-information in ser is no longer valid. Is there any reason why the nathelper rewrites the port in the contact-header? If the client is symmetric the source-port and the port in the contact-header shouldn't differ anyway? I trust there is a reason, i just dont see it ;) On a side-note, when glancing at nathelper.c it looks as if the int len is calculated with the original values of the header, then filled through snprintf with values which are not 100% positively the same length (msg->rcv.src_port). Isn't it for example possible that the port in the header is 5060 but the source_port is 22444 (which is one character longer than the length of len is calculated to). I hope someone can shed some light over the matter. /Martin