[BB#81] allow listening on multiple families when no Listen is provided in config

This is achieved by not stopping at the first result of getaddrinfo
that we managed to listen on: Without "Listen" in the config, we
call getraddrinfo with NULL address. With AI_PASSIVE, this gives results
for both IPv4 and IPv6 wildcard addresses (if both are supported).

This lets tinyproxy listen on both IPv4 and IPv6 wildcard if the system
supports them.

Signed-off-by: Michael Adam <obnox@samba.org>
(cherry picked from commit d0732f9ade)

src/sock.c

@@ -281,10 +281,17 @@ int listen_sock (const char *addr, uint16_t port, vector_t listen_fds)
 
                 vector_append (listen_fds, &listenfd, sizeof(int));
 
-                /* success, don't continue */
+                /* success */
                 ret = 0;
+
+                if (addr != NULL) {
+                        /*
+                         * Unless wildcard is requested, only listen
+                         * on the first result that works.
+                         */
                         break;
                 }
+        }
 
         if (ret != 0) {
                 log_message (LOG_ERR, "Unable to listen on any address.");