openwrtv3/package/busybox/patches/243-udhcpc_changed_ifindex.patch

--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -320,6 +320,12 @@ int udhcpc_main(int argc UNUSED_PARAM, c
 	for (;;) {
 		unsigned timestamp_before_wait;
 
+		/* When running on a bridge, the ifindex may have changed (e.g. if
+		 * member interfaces were added/removed or if the status of the
+		 * bridge changed).
+		 * Workaround: refresh it here before processing the next packet */
+		udhcp_read_interface(client_config.interface, &client_config.ifindex, NULL, client_config.arp);
+
 		if (listen_mode != LISTEN_NONE && sockfd < 0) {
 			if (listen_mode == LISTEN_KERNEL)
 				sockfd = udhcp_listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_config.interface);