Proper handle the case of no usrloc domain registered.

Prevent get_next_udomain() crashing if there are no usrloc domains registered (reported by Qasim Akhan on users mailing list.
Do not enable the pinging support in nathelper if usrloc has no registered domains.

modules/nathelper/nathelper.c

@@ -491,20 +491,6 @@ mod_init(void)
 		rcv_avp_type = 0;
 	}
 
-	if (force_socket_str) {
-		socket_str.s=force_socket_str;
-		socket_str.len=strlen(socket_str.s);
-		force_socket=grep_sock_info(&socket_str,0,0);
-	}
-
-	/* create raw socket? */
-	if (natping_socket && natping_socket[0]) {
-		if (get_natping_socket( natping_socket, &raw_ip, &raw_port)!=0)
-			return -1;
-		if (init_raw_socket() < 0)
-			return -1;
-	}
-
 	if (nortpproxy_str.s==NULL || nortpproxy_str.s[0]==0) {
 		nortpproxy_str.len = 0;
 		nortpproxy_str.s = NULL;
@@ -517,6 +503,9 @@ mod_init(void)
 			nortpproxy_str.s = NULL;
 	}
 
+	/* enable all the pinging stuff only if pinging interval is set and
+	 * if we have at least one domain in the usrloc (otherwise there is
+	 * nothing to ping) */
 	if (natping_interval > 0) {
 		bind_usrloc = (bind_usrloc_t)find_export("ul_bind_usrloc", 1, 0);
 		if (!bind_usrloc) {
@@ -528,6 +517,26 @@ mod_init(void)
 			return -1;
 		}
 
+		if ( ul.get_next_udomain(NULL)==NULL ) {
+			/* no usrloc domains, nothing to ping, so abort enabling
+			 * the pinging support */
+			goto after_pinging;
+		}
+
+		if (force_socket_str) {
+			socket_str.s=force_socket_str;
+			socket_str.len=strlen(socket_str.s);
+			force_socket=grep_sock_info(&socket_str,0,0);
+		}
+
+		/* create raw socket? */
+		if (natping_socket && natping_socket[0]) {
+			if (get_natping_socket( natping_socket, &raw_ip, &raw_port)!=0)
+				return -1;
+			if (init_raw_socket() < 0)
+				return -1;
+		}
+
 		natping_state =(unsigned int *) shm_malloc(sizeof(unsigned int));
 		if (!natping_state) {
 			LM_ERR("no shmem left\n");
@@ -547,13 +556,11 @@ mod_init(void)
 		}
 
 		fix_flag_name(sipping_flag_str, sipping_flag);
-		sipping_flag = get_flag_id_by_name(FLAG_TYPE_BRANCH, sipping_flag_str);
-
+		sipping_flag=get_flag_id_by_name(FLAG_TYPE_BRANCH, sipping_flag_str);
 		sipping_flag = (sipping_flag==-1)?0:(1<<sipping_flag);
 
 		fix_flag_name(rm_on_to_flag_str, rm_on_to_flag);
-		rm_on_to_flag = get_flag_id_by_name(FLAG_TYPE_BRANCH, rm_on_to_flag_str);
-
+		rm_on_to_flag=get_flag_id_by_name(FLAG_TYPE_BRANCH, rm_on_to_flag_str);
 		rm_on_to_flag = (rm_on_to_flag==-1)?0:(1<<rm_on_to_flag);
 
 		/* set reply function if SIP natping is enabled */
@@ -579,8 +586,8 @@ mod_init(void)
 		}
 
 		if (REMOVE_ON_TIMEOUT &&
-				register_timer("pg-chk-timer", ping_checker_timer,
-					NULL, ping_checker_interval, TIMER_FLAG_DELAY_ON_DELAY) < 0) {
+		register_timer("pg-chk-timer", ping_checker_timer,
+		NULL, ping_checker_interval, TIMER_FLAG_DELAY_ON_DELAY) < 0) {
 			LM_ERR("failed to register ping checker timer\n");
 			return -1;
 		}
@@ -603,6 +610,8 @@ mod_init(void)
 		}
 	}
 
+after_pinging:
+
 	/* Prepare 1918/6598 networks list */
 	for (i = 0; nets_1918[i].cnetaddr != NULL; i++) {
 		if (inet_aton(nets_1918[i].cnetaddr, &addr) != 1)

modules/usrloc/dlist.c

@@ -67,6 +67,11 @@ udomain_t* get_next_udomain(udomain_t *_d)
 {
 	dlist_t *it;
 
+	/* if not domain registered, return NULL directly */
+	if (root==NULL)
+		return NULL;
+
+	/* if no input provide, return the first domain */
 	if (_d==NULL)
 		return root->d;