Netlink: Ignore dead routes

With net.ipv4.conf.XXX.ignore_routes_with_linkdown sysctl, a user can
ensure the kernel does not use a route whose target interface is down.
Such route is marked with a 'dead' / RTNH_F_DEAD flag.

Ignore these routes or multipath nexthops during scan.

Thanks to Vincent Bernat for the original patch.

1 files changed, 7 insertions, 1 deletions

diff --git a/sysdep/linux/netlink.c b/sysdep/linux/netlink.c
index 6d98e53d..fdf3f2db 100644
--- a/sysdep/linux/netlink.c
+++ b/sysdep/linux/netlink.c
@@ -697,6 +697,9 @@ nl_parse_multipath(struct nl_parse_state *s, struct krt_proto *p, struct rtattr
       if ((len < sizeof(*nh)) || (len < nh->rtnh_len))
 	return NULL;
 
+      if (nh->rtnh_flags & RTNH_F_DEAD)
+	goto next;
+
       *last = rv = lp_allocz(s->pool, NEXTHOP_MAX_SIZE);
       last = &(rv->next);
 
@@ -772,7 +775,7 @@ nl_parse_multipath(struct nl_parse_state *s, struct krt_proto *p, struct rtattr
       }
 #endif
 
-
+    next:
       len -= NLMSG_ALIGN(nh->rtnh_len);
       nh = RTNH_NEXT(nh);
     }
@@ -1683,6 +1686,9 @@ nl_parse_route(struct nl_parse_state *s, struct nlmsghdr *h)
 	  break;
 	}
 
+      if (i->rtm_flags & RTNH_F_DEAD)
+	return;
+
       ra->nh.iface = if_find_by_index(oif);
       if (!ra->nh.iface)
 	{