Implement onlink flag for nexthops

Add proper support for per-nexthop onlink flag in routes to handle next
hop addresses that are not covered by interface IP ranges. Supported by
kernel and static protocols.

Thanks to Vincent Bernat for the idea.

1 files changed, 15 insertions, 2 deletions

diff --git a/sysdep/linux/netlink.c b/sysdep/linux/netlink.c
index 40d1196e..2b7b13fb 100644
--- a/sysdep/linux/netlink.c
+++ b/sysdep/linux/netlink.c
@@ -622,6 +622,9 @@ nl_add_multipath(struct nlmsghdr *h, uint bufsize, struct nexthop *nh, int af)
 
     nl_add_nexthop(h, bufsize, nh, af);
 
+    if (nh->flags & RNF_ONLINK)
+      rtnh->rtnh_flags |= RTNH_F_ONLINK;
+
     nl_close_nexthop(h, rtnh);
   }
 
@@ -660,6 +663,7 @@ nl_parse_multipath(struct krt_proto *p, struct rtattr *ra)
       rv->next = NULL;
       last = &(rv->next);
 
+      rv->flags = 0;
       rv->weight = nh->rtnh_hops;
       rv->iface = if_find_by_index(nh->rtnh_ifindex);
       if (!rv->iface)
@@ -672,9 +676,12 @@ nl_parse_multipath(struct krt_proto *p, struct rtattr *ra)
 	{
 	  rv->gw = rta_get_ipa(a[RTA_GATEWAY]);
 
+	  if (nh->rtnh_flags & RTNH_F_ONLINK)
+	    rv->flags |= RNF_ONLINK;
+
 	  neighbor *nbr;
 	  nbr = neigh_find2(&p->p, &rv->gw, rv->iface,
-			    (nh->rtnh_flags & RTNH_F_ONLINK) ? NEF_ONLINK : 0);
+			    (rv->flags & RNF_ONLINK) ? NEF_ONLINK : 0);
 	  if (!nbr || (nbr->scope == SCOPE_HOST))
 	    return NULL;
 	}
@@ -1228,6 +1235,9 @@ dest:
       {
 	nl_add_attr_u32(&r->h, rsize, RTA_OIF, nh->iface->index);
 	nl_add_nexthop(&r->h, rsize, nh, p->af);
+
+	if (nh->flags & RNF_ONLINK)
+	  r->r.rtm_flags |= RTNH_F_ONLINK;
       }
       break;
     case RTD_BLACKHOLE:
@@ -1543,9 +1553,12 @@ nl_parse_route(struct nl_parse_state *s, struct nlmsghdr *h)
 	  if ((i->rtm_family == AF_INET6) && ipa_in_netX(ra->nh.gw, (net_addr *) &sit))
 	    return;
 
+	  if (i->rtm_flags & RTNH_F_ONLINK)
+	    ra->nh.flags |= RNF_ONLINK;
+
 	  neighbor *nbr;
 	  nbr = neigh_find2(&p->p, &(ra->nh.gw), ra->nh.iface,
-			    (i->rtm_flags & RTNH_F_ONLINK) ? NEF_ONLINK : 0);
+			    (ra->nh.flags & RNF_ONLINK) ? NEF_ONLINK : 0);
 	  if (!nbr || (nbr->scope == SCOPE_HOST))
 	    {
 	      log(L_ERR "KRT: Received route %N with strange next-hop %I", net->n.addr,