[SR-Users] Re: Dispatcher Incoming

Path support in upstream PJSIP is broken, from what I'm given to understand. This is a regression from a capability that was (finally) added to chan_sip in Asterisk 12. Digium/Sangoma have clearly stated that they have no interest to fix: https://issues.asterisk.org/jira/browse/ASTERISK-28211 As stated in the comments on that JIRA issue, "There is no timeline." I'm not sure what the logic is. I think it's something like, "Nobody uses proxies" ?? Not sure. Our generally accepted "fix" for this is to hack the Path hop into the Contact header of the registrant before relaying the REGISTER upstream, so that registrations appear to Asterisk to come "from" Kamailio. This requires careful management and stateful reversion of the Contact value (i.e. in the RURI of incoming requests), making it a brittle and suboptimal solution. But when "there is no timeline", what can you do? ======== modparam("htable", "htable", "contacts=>size=18;autoexpire=300;") request_route { ... if(method == "REGISTER") { ... route(CONTACT_SPOOF_ENCODE); t_on_reply("REGISTER_REPLY_FROM_PBX"); } else if(src == PBX) { # Request destined for registrant, e.g. INVITE. route(CONTACT_SPOOF_DECODE); } } onreply_route[REGISTER_REPLY_FROM_PBX] { if(!method == "REGISTER") return; # If we are channeling a 200 OK for a register, it is very important to # restore the exact Contact binding registered by the UA, together with # all of its parameters, so that the UA comes to believe the binding # has been properly established. if($rs == 200) route(CONTACT_SPOOF_DECODE); } # This routine gets around the lack of Path support in upstream registrars by # encoding the original Contact domain as a supplementary parameter and attaching # it to the Contact binding. This can then be recovered on inbound requests. route[CONTACT_SPOOF_ENCODE] { $var(hash_key) = $(ct{s.sha256}); $sht(contacts=>$var(hash_key)) = $ct; remove_hf("Contact"); append_hf("Contact: <sip:gateway@$Ri:$Rp;cthash=$var(hash_key)>\r\n"); } # Use `cthash` parameter to retrieve original contact from `htable` if present, # and replace. We do this in a contextually sensitive way, extracting `cthash` # from the Contact header in a reply and from the RURI if it is a request. route[CONTACT_SPOOF_DECODE] { $var(ct) = $null; if(t_is_request_route()) $var(ct) = $ru; else if(t_is_reply_route()) $var(ct) = $(ct{nameaddr.uri}); # Unbracket the URI field. if(strempty($(var(ct){param.value,cthash}))) { if(t_is_request_route()) sl_send_reply("500", "Internal server error - missing ct"); xlog("L_INFO", "[R-CONTACT-SPOOF-DECODE:$ci] !> Unable to extract 'cthash' URI parameter\n"); exit; } $var(ct_key) = $(var(ct){param.value,cthash}); # Likewise error out if we cannot translate to the real contact, since there's # no point in sending an adulterated contact to the UA. if($sht(contacts=>$var(ct_key)) eq $null) { if(t_is_request_route()) sl_send_reply("500", "Internal server error - cannot map ct"); xlog("L_INFO", "[R-CONTACT-SPOOF-DECODE:$ci] !> cthash key does not map to a contact!\n"); exit; } if(t_is_request_route()) $ru = $(sht(contacts=>$var(ct_key)){nameaddr.uri}); else { remove_hf("Contact"); append_hf("Contact: $sht(contacts=>$var(ct_key))\r\n"); } } -- Alex -- Alex Balashov | Principal | Evariste Systems LLC Tel: +1-706-510-6800 / +1-800-250-5920 (toll-free) Web: http://www.evaristesys.com/, http://www.csrpswitch.com/