Let the kernel delete the (default) route when we deconfigure the

interface.

This works around a problem where the kernel always deletes
the first default route if there are multiple present
with the same gateway.

This only fixes the problem when running ifconfig inet -autoconf.

There are other cases where we call configure_rotures(RTM_DELETE), for
example when setting ignore routes in dhcpleased.conf and issuing a
reload. To fix that we either need help from the kernel to distinguish
routes by IFP or track priorities and hope they are unique.

Problem reported by mbuhl.
OK claudio

1 files changed, 15 insertions, 1 deletions

diff --git a/sbin/dhcpleased/dhcpleased.c b/sbin/dhcpleased/dhcpleased.c
index bfd7c84e6e0..ef6200d6bc0 100644
--- a/sbin/dhcpleased/dhcpleased.c
+++ b/sbin/dhcpleased/dhcpleased.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: dhcpleased.c,v 1.25 2022/07/23 09:29:20 florian Exp $	*/
+/*	$OpenBSD: dhcpleased.c,v 1.26 2022/07/23 09:33:18 florian Exp $	*/
 
 /*
  * Copyright (c) 2017, 2021 Florian Obser <florian@openbsd.org>
@@ -914,8 +914,22 @@ deconfigure_interface(struct imsg_configure_interface *imsg)
 
 	memset(&ifaliasreq, 0, sizeof(ifaliasreq));
 
+#if 0
+	/*
+	 * When two default routes have the same gateway the kernel always
+	 * deletes the first which might be the wrong one. When we then
+	 * deconfigure the IP address from the interface the kernel deletes
+	 * all routes pointing out that interface and we end up with no
+	 * default.
+	 * This can happen with a wired & wireless interface on the same
+	 * layer 2 network and the user issues ifconfig $WIFI inet -autoconf.
+	 * Work around this issue by not deleting the default route and let
+	 * the kernel handle it when we remove the IP address a few lines
+	 * down.
+	 */
 	if (imsg->routes_len > 0)
 		configure_routes(RTM_DELETE, imsg);
+#endif
 
 	if (if_indextoname(imsg->if_index, ifaliasreq.ifra_name) == NULL) {
 		log_warnx("%s: cannot find interface %d", __func__,