Index: chan_sip.c
===================================================================
--- chan_sip.c	(revision 65247)
+++ chan_sip.c	(working copy)
@@ -1414,6 +1414,8 @@
 static struct sip_peer *temp_peer(const char *name);
 static void register_peer_exten(struct sip_peer *peer, int onoff);
 static struct sip_peer *find_peer(const char *peer, struct sockaddr_in *sin, int realtime);
+/*&&&*/
+static struct sip_peer *find_peer_siphead(const char *peer, struct sockaddr_in *sin, char *username, int realtime);
 static struct sip_user *find_user(const char *name, int realtime);
 static enum parse_register_result parse_register_contact(struct sip_pvt *pvt, struct sip_peer *p, struct sip_request *req);
 static int expire_register(void *data);
@@ -2506,6 +2508,7 @@
 					(p->addr.sin_addr.s_addr == sin->sin_addr.s_addr)));
 }
 
+
 /*! \brief Locate peer by name or ip address 
  *	This is used on incoming SIP message to find matching peer on ip
 	or outgoing message to find matching peer on name */
@@ -2524,6 +2527,38 @@
 	return p;
 }
 
+/*!&&& \brief Locate peer by username and ip address 
+ *	This is used on incoming SIP message to find matching peer on To username and sender IP */
+static struct sip_peer *find_peer_siphead(const char *peer, struct sockaddr_in *sin, char *username, int realtime)
+{
+	struct sip_peer *p = NULL;
+
+	if (peer) {
+		return NULL; /* use find_peer instead */
+	} else {
+		typeof((&peerl)->head) found = NULL; 
+		ASTOBJ_CONTAINER_TRAVERSE(&peerl, !found, do { 
+			ASTOBJ_RDLOCK(iterator); 
+			if (!(sip_addrcmp(iterator->name, sin)) &&
+			    !(strcmp(iterator->username, username))) { 
+				found = ASTOBJ_REF(iterator); 
+			} 
+			ASTOBJ_UNLOCK(iterator); 
+		} while (0)); 
+		p=found; 
+
+		/* fallback to old behavior */
+		if (p == NULL) {
+			p=find_peer(peer, sin, realtime);
+		}
+	} /* if */
+
+	if (!p && realtime)
+		p = realtime_peer(peer, sin);
+
+	return p;
+}
+
 /*! \brief Remove user object from in-memory storage */
 static void sip_destroy_user(struct sip_user *user)
 {
@@ -9008,6 +9043,7 @@
 	struct sip_user *user = NULL;
 	struct sip_peer *peer;
 	char from[256], *c;
+	char to[256], *ot; /*&&&*/
 	char *of;
 	char rpid_num[50];
 	const char *rpid;
@@ -9024,8 +9060,29 @@
 		t++;
 	*t = '\0';
 	ast_copy_string(from, get_header(req, "From"), sizeof(from));	/* XXX bug in original code, overwrote string */
-	if (pedanticsipchecking)
+	if (pedanticsipchecking) 
 		ast_uri_decode(from);
+
+	/*&&&start: extract To: username from To field */
+	ast_copy_string(to, get_header(req, "To"), sizeof(to));	/* &&& */
+	if (pedanticsipchecking) {
+		ast_uri_decode(to); /*&&&*/
+	}
+	ot = get_in_brackets(to);
+	if (strncasecmp(ot, "sip:", 4)) {
+		ast_log(LOG_NOTICE, "To address missing 'sip:', using it anyway\n");
+	} else {
+		ot += 4;
+	}
+	/* Get just the username part */
+	if ((c = strchr(ot, '@'))) {
+		*c = '\0';
+		if ((c = strchr(ot, ':')))
+			*c = '\0';
+	}
+	/* ot is now the username of the From field */
+	/*&&&end */
+
 	/* XXX here tries to map the username for invite things */
 	memset(calleridname, 0, sizeof(calleridname));
 	get_calleridname(from, calleridname, sizeof(calleridname));
@@ -9184,9 +9241,22 @@
 			/* If peer is registered from this IP address or have this as a default
 			   IP address, this call is from the peer 
 			*/
-			peer = find_peer(NULL, &p->recv, 1);
+/*&&& Original code is weak behavior. Lookup must be done viy SIP header data,
+      then - if all this fails - I may do the lookup via sender IP address.
+      Imagine different 2 account registered at the same provider - a lookup
+      purely based on sende IP address will mess up the matching between these
+      two accounts.
+*/
+			peer = find_peer_siphead(NULL, &p->recv, ot, 1);
 
 		if (peer) {
+			/*&&&*/
+			if (debug) {
+				ast_verbose("Found matching peer for '%s:%d [%s]'\n",
+				            ast_inet_ntoa(p->recv.sin_addr),
+					    ntohs(p->recv.sin_port), peer->name);
+			}
+
 			/* Set Frame packetization */
 			if (p->rtp) {
 				ast_rtp_codec_setpref(p->rtp, &peer->prefs);
@@ -14920,6 +14990,7 @@
 	int lockretry;
 
 	memset(&req, 0, sizeof(req));
+	memset(&sin, 0, sizeof(sin)); /*&&& just to be sure...*/
 	res = recvfrom(sipsock, req.data, sizeof(req.data) - 1, 0, (struct sockaddr *)&sin, &len);
 	if (res < 0) {
 #if !defined(__FreeBSD__)