Re: [OpenSER-Users] recover from previous strict routing triggered incorrectly in ALG scenario

Hi Andrew,

Just a short question - how comes that your BYE has proxy ips in RURI and Route ? where the end-device IP ??

Regards, Bogdan

Andrew Pogrebennyk wrote:

Hi, Im'm cross-posting this from OpenSER-Devel because I am not 100% sure this is a bug.

I am trying to create openser configuration for proxy that connects private (VPN) network with public network. I started with a config similar to http://voipembedded.com/resources/openser_cr.cfg, added a call to force_send_socket() to send from public IP and rtpproxy/nathelper in bridge mode. As per config loose_route() is called from openser.cfg to route a sequential request within a dialog through record-routing. Now when a BYE from callee comes in, it contains two Route headers: Route: <a.b.c.d;r2=on;lr;ftag=...> where a.b.c.d is server's public IP, Route: <10.0.0.100;r2=on;lr;ftag=...> where 10.0.0.100 is a private IP and username@a.b.c.d in Request-URI.

Take a look at loose_route():

/*

• Do loose routing as defined in RFC3261

*/ int loose_route(struct sip_msg* _m, char* _s1, char* _s2) { int ret;

 if (find_first_route(_m) != 0) {
     LM_DBG("There is no Route HF\n");
     return -1;
 }

 if (parse_sip_msg_uri(_m)<0) {
     LM_ERR("failed to parse Request URI\n");
     return -1;
 }

 ret = is_preloaded(_m);
 if (ret < 0) {
     return -1;
 } else if (ret == 1) {
     return after_loose(_m, 1);
 } else {

#ifdef ENABLE_USER_CHECK if (is_myself(&_m->parsed_uri.user, &_m->parsed_uri.host, _m->parsed_uri.port_no)) { #else if (is_myself(&_m->parsed_uri.host, _m->parsed_uri.port_no)) { #endif return after_strict(_m); } else { return after_loose(_m, 0); } } }

Obviously, is_myself() check passes and after_strict() is called.

when after_strict() is called, it looks if the URI given in Route contains lr parameter which marks loose routers, if so this block of code is executed: { LM_DBG("Next hop: '%.*s' is loose router\n", uri.len, ZSW(uri.s));

     if(get_maddr_uri(&uri, &puri)!=0) {
         LM_ERR("failed to check maddr\n");
         return RR_ERROR;
     }
     if (set_dst_uri(_m, &uri) < 0) {
         LM_ERR("failed to set dst_uri\n");
         return RR_ERROR;
     }

     /* Next hop is a loose router - Which means that is is not 

endpoint yet * In This case we have to recover from previous strict routing, that * means we have to find the last Route URI and put in in R-URI and * remove the last Route URI. */ if (rt != hdr->parsed) { /* There is a previous route uri which was 2nd uri of mine * and must be removed here */ rem_off = hdr->body.s; rem_len = rt->nameaddr.name.s - hdr->body.s; if (!del_lump(_m, rem_off - _m->buf, rem_len, 0)) { LM_ERR("failed to remove Route HF\n"); return RR_ERROR; } }

     res = find_rem_target(_m, &hdr, &rt, &prev);
     if (res < 0) {
         LM_ERR("searching for last Route URI failed\n");
         return RR_ERROR;
     } else if (res > 0) {
         /* No remote target is an error */
         return RR_ERROR;
     }

     uri = rt->nameaddr.uri;
     if(get_maddr_uri(&uri, 0)!=0) {
         LM_ERR("checking maddr failed\n");
         return RR_ERROR;
     }
     if (rewrite_uri(_m, &uri) < 0) {
         LM_ERR("failed to rewrite R-URI\n");
         return RR_ERROR;
     }

     /* The first character if uri will be either '<' when it is the
      * only URI in a Route header field or ',' if there is more than
      * one URI in the header field */
     LM_DBG("The last route URI: '%.*s'\n", rt->nameaddr.uri.len,
             ZSW(rt->nameaddr.uri.s));

     if (prev) {
         rem_off = prev->nameaddr.name.s + prev->len;
         rem_len = rt->nameaddr.name.s + rt->len - rem_off;
     } else {
         rem_off = hdr->name.s;
         rem_len = hdr->len;
     }
     if (!del_lump(_m, rem_off - _m->buf, rem_len, 0)) {
         LM_ERR("failed to remove Route HF\n");
         return RR_ERROR;
     }
 }

Therefore recover from previous strict routing is triggered: contents of request line is destroyed and 10.0.0.100 is put instead: Apr 15 16:16:24 vpn-proxy oser[11027]: DBG:core:rewrite_uri: rewriting Request-URI with 'sip:10.0.0.100;r2=on;lr;ftag=aa40c2a5-54fb-1810-970d-0015c5bf2da5' Apr 15 16:16:24 vpn-proxy oser[11032]: [1] Got in dialog request not catched by loose_route(): BYE sip:10.0.0.100;r2=on;lr;ftag=aa40c2a5-54fb-1810-970d-0015c5bf2da5 SIP/2.0^M Via:...

And we respond with 404 to in-dialog requests not caught by loose_route(). Previous hop is SER and I don't know why OpenSER considered it a strict router. Looks like a peculiarity of ALG mode. Please advice what should I do to solve this problem. Is it a configuration issue or perhaps loose_route() should not call after_strict() in case of double record-routing?

-- Thank you, Andrew Pogrebennyk

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