introduce proxy_sticky_auth feature

thanks to Tobias Lindgren for reporting

core/AmConfig.cpp

@@ -71,6 +71,7 @@ int          AmConfig::LocalSIPPort            = 5060;
 string       AmConfig::LocalSIPIP              = "";
 string       AmConfig::OutboundProxy           = "";
 bool         AmConfig::ForceOutboundProxy      = false;
+bool         AmConfig::ProxyStickyAuth         = false;
 string       AmConfig::Signature               = "";
 unsigned int AmConfig::MaxForwards             = MAX_FORWARDS;
 bool	     AmConfig::SingleCodecInOK	       = false;
@@ -286,6 +287,10 @@ int AmConfig::readConfiguration()
   if(cfg.hasParameter("force_outbound_proxy")) {
     ForceOutboundProxy = (cfg.getParameter("force_outbound_proxy") == "yes");
   }
+
+  if(cfg.hasParameter("proxy_sticky_auth")) {
+    ProxyStickyAuth = (cfg.getParameter("proxy_sticky_auth") == "yes");
+  }
   
   // plugin_path
   if (cfg.hasParameter("plugin_path"))

core/AmConfig.h

@@ -102,6 +102,8 @@ struct AmConfig
   static string OutboundProxy;
   /** force Outbound Proxy to be used for in dialog requests */
   static bool ForceOutboundProxy;
+  /** update ruri-host to previously resolved IP:port on SIP auth */
+  static bool ProxyStickyAuth;
   /** Server/User-Agent header (optional) */
   static string Signature;
   /** Value of Max-Forward header field for new requests */

core/etc/sems.conf.sample

@@ -394,6 +394,16 @@ use_default_signature=yes
 #
 #100rel=require
 
+# Make SIP authenticated requests sticky to the proxy? [yes | no]
+#
+# If enabled, host of request-URI of out-of-dialog requests that are 
+# authenticated with SIP auth is changed to the previously resolved
+# next-hop IP:port.
+#
+# default: no
+#
+# proxy_sticky_auth=yes
+
 #
 # Accept final replies without To-tag? [yes|no]
 #

core/plug-in/uac_auth/UACAuth.cpp

@@ -167,6 +167,17 @@ bool UACAuth::onSipReply(const AmSipReply& reply, int old_dlg_status, const stri
 	      // reset remote tag so remote party 
 	      // thinks its new dlg
 	      dlg->remote_tag = "";
+
+	      if (AmConfig::ProxyStickyAuth) {
+		// update remote URI to resolved IP
+		size_t hpos = dlg->remote_uri.find("@");
+		if (hpos != string::npos && reply.remote_ip.length()) {
+		  dlg->remote_uri = dlg->remote_uri.substr(0, hpos+1) +
+		    reply.remote_ip + ":"+int2str(reply.remote_port);
+		  DBG("updated remote URI to '%s'\n", dlg->remote_uri.c_str());
+		}
+	      }
+
 	    }
 	    // resend request 
 	    if (dlg->sendRequest(ri->second.method,