Don't exit, but retry, if mdns_start() fails.

testmdnsd.c

@@ -357,7 +357,8 @@ main(int argc, char **argv)
 	
 			if (mdnsd_start(fullname, ip_addr) < 0) {
 				fprintf(stderr, "mdnsd_start() error\n");
-				return 1;
+				/* may just have no interface */
+				continue;
 			}
 			running = 1;