Check IP address command line arg in dhcp_release.c

contrib/wrt/dhcp_release.c

@@ -277,6 +277,11 @@ int main(int argc, char **argv)
       exit(1);
     }
   
+  if (inet_addr(argv[2]) == INADDR_NONE)
+    {
+      perror("invalid ip address");
+      exit(1);
+    }
   
   lease.s_addr = inet_addr(argv[2]);
   server = find_interface(lease, nl, if_nametoindex(argv[1]));