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.

nest/route.h

@@ -366,12 +366,16 @@ struct nexthop {
   ip_addr gw;				/* Next hop */
   struct iface *iface;			/* Outgoing interface */
   struct nexthop *next;
+  byte flags;
   byte weight;
   byte labels_orig;			/* Number of labels before hostentry was applied */
   byte labels;				/* Number of all labels */
   u32 label[0];
 };
 
+#define RNF_ONLINK		0x1	/* Gateway is onlink regardless of IP ranges */
+
+
 struct rte_src {
   struct rte_src *next;			/* Hash chain */
   struct proto *proto;			/* Protocol the source is based on */

nest/rt-attr.c

@@ -171,7 +171,9 @@ nexthop__same(struct nexthop *x, struct nexthop *y)
 {
   for (; x && y; x = x->next, y = y->next)
   {
-    if (!ipa_equal(x->gw, y->gw) || (x->iface != y->iface) || (x->weight != y->weight) || (x->labels != y->labels))
+    if (!ipa_equal(x->gw, y->gw) || (x->iface != y->iface) ||
+	(x->flags != y->flags) || (x->weight != y->weight) ||
+	(x->labels != y->labels))
       return 0;
 
     for (int i = 0; i < x->labels; i++)
@@ -193,6 +195,8 @@ nexthop_compare_node(struct nexthop *x, struct nexthop *y)
   if (!y)
     return -1;
 
+  /* Should we also compare flags ? */
+
   r = ((int) y->weight) - ((int) x->weight);
   if (r)
     return r;

nest/rt-show.c

@@ -70,6 +70,7 @@ rt_show_rte(struct cli *c, byte *ia, rte *e, struct rt_show_data *d, ea_list *tm
     for (nh = &(a->nh); nh; nh = nh->next)
     {
       char mpls[MPLS_MAX_LABEL_STACK*12 + 5], *lsp = mpls;
+      char *onlink = (nh->flags & RNF_ONLINK) ? " onlink" : "";
 
       if (nh->labels)
         {
@@ -80,9 +81,11 @@ rt_show_rte(struct cli *c, byte *ia, rte *e, struct rt_show_data *d, ea_list *tm
       *lsp = '\0';
 
       if (a->nh.next)
-	cli_printf(c, -1007, "\tvia %I%s on %s weight %d", nh->gw, mpls, nh->iface->name, nh->weight + 1);
+	cli_printf(c, -1007, "\tvia %I%s on %s%s weight %d",
+		   nh->gw, mpls, nh->iface->name, onlink, nh->weight + 1);
       else
-	cli_printf(c, -1007, "\tvia %I%s on %s", nh->gw, mpls, nh->iface->name);
+	cli_printf(c, -1007, "\tvia %I%s on %s%s",
+		   nh->gw, mpls, nh->iface->name, onlink);
     }
 
   if (d->verbose)

nest/rt-table.c

@@ -1819,7 +1819,10 @@ no_nexthop:
       }
     }
     if (ipa_nonzero(nh->gw))
-      nhp->gw = nh->gw;		/* Router nexthop */
+    {
+      nhp->gw = nh->gw;			/* Router nexthop */
+      nhp->flags |= (nh->flags & RNF_ONLINK);
+    }
     else if (ipa_nonzero(he->link))
       nhp->gw = he->link;		/* Device nexthop with link-local address known */
     else

proto/static/config.Y

@@ -44,7 +44,7 @@ static_route_finish(void)
 CF_DECLS
 
 CF_KEYWORDS(STATIC, ROUTE, VIA, DROP, REJECT, PROHIBIT, PREFERENCE, CHECK, LINK)
-CF_KEYWORDS(WEIGHT, RECURSIVE, IGP, TABLE, BLACKHOLE, UNREACHABLE, BFD, MPLS)
+CF_KEYWORDS(ONLINK, WEIGHT, RECURSIVE, IGP, TABLE, BLACKHOLE, UNREACHABLE, BFD, MPLS)
 
 
 CF_GRAMMAR
@@ -87,6 +87,9 @@ stat_nexthop:
   | stat_nexthop MPLS label_stack {
     this_snh->mls = $3;
   }
+  | stat_nexthop ONLINK bool {
+    this_snh->onlink = $3;
+  }
   | stat_nexthop WEIGHT expr {
     this_snh->weight = $3 - 1;
     if (($3<1) || ($3>256)) cf_error("Weight must be in range 1-256");

proto/static/static.c

@@ -71,6 +71,7 @@ static_announce_rte(struct static_proto *p, struct static_route *r)
       struct nexthop *nh = allocz(NEXTHOP_MAX_SIZE);
       nh->gw = r2->via;
       nh->iface = r2->neigh->iface;
+      nh->flags = r2->onlink ? RNF_ONLINK : 0;
       nh->weight = r2->weight;
       if (r2->mls)
       {
@@ -205,7 +206,8 @@ static_add_rte(struct static_proto *p, struct static_route *r)
     for (r2 = r; r2; r2 = r2->mp_next)
     {
       n = ipa_nonzero(r2->via) ?
-	neigh_find2(&p->p, &r2->via, r2->iface, NEF_STICKY) :
+	neigh_find2(&p->p, &r2->via, r2->iface,
+		    NEF_STICKY | (r2->onlink ? NEF_ONLINK : 0)) :
 	neigh_find_iface(&p->p, r2->iface);
 
       if (!n)
@@ -267,8 +269,9 @@ static_same_dest(struct static_route *x, struct static_route *y)
     {
       if (!ipa_equal(x->via, y->via) ||
 	  (x->iface != y->iface) ||
-	  (x->use_bfd != y->use_bfd) ||
+	  (x->onlink != y->onlink) ||
 	  (x->weight != y->weight) ||
+	  (x->use_bfd != y->use_bfd) ||
 	  (!x->mls != !y->mls) ||
 	  ((x->mls) && (y->mls) && (x->mls->len != y->mls->len)))
 	return 0;
@@ -614,11 +617,13 @@ static_show_rt(struct static_route *r)
     for (r2 = r; r2; r2 = r2->mp_next)
     {
       if (r2->iface && ipa_zero(r2->via))
-	cli_msg(-1009, "\tdev %s%s%s", r2->iface->name,
+	cli_msg(-1009, "\tdev %s%s", r2->iface->name,
-		r2->bfd_req ? " (bfd)" : "", r2->active ? "" : " (dormant)");
+		r2->active ? "" : " (dormant)");
       else
-	cli_msg(-1009, "\tvia %I%J%s%s", r2->via, r2->iface,
+	cli_msg(-1009, "\tvia %I%J%s%s%s", r2->via, r2->iface,
-		r2->bfd_req ? " (bfd)" : "", r2->active ? "" : " (dormant)");
+		r2->onlink ? " onlink" : "",
+		r2->bfd_req ? " (bfd)" : "",
+		r2->active ? "" : " (dormant)");
     }
     break;
   }

proto/static/static.h

@@ -43,6 +43,7 @@ struct static_route {
   byte dest;				/* Destination type (RTD_*) */
   byte state;				/* State of route announcement (SRS_*) */
   byte active;				/* Next hop is active (nbr/iface/BFD available) */
+  byte onlink;				/* Gateway is onlink regardless of IP ranges */
   byte weight;				/* Multipath next hop weight */
   byte use_bfd;				/* Configured to use BFD */
   struct bfd_request *bfd_req;		/* BFD request, if BFD is used */

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,