From: Maria Matejka <mq@ucw.cz>
Date: Tue, 27 May 2025 08:58:23 +0000 (+0200)
Subject: Filters: Re-enabling onlink nexthop attribute
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c1957b2ae0ee596965fed5d7a5a74e78e49acd5e;p=thirdparty%2Fbird.git

Filters: Re-enabling onlink nexthop attribute

There are still some semantic problems wrt. VRF settings,
effectively allowing botched nexthops to slip through filters,
but it makes more sense to re-enable onlink setting, than
to wait until we find out how to do that all properly.

This resolves #258.
---

diff --git a/filter/config.Y b/filter/config.Y
index 8da771ff3..d2719637b 100644
--- a/filter/config.Y
+++ b/filter/config.Y
@@ -367,7 +367,7 @@ CF_KEYWORDS(FUNCTION, PRINT, PRINTN, UNSET, RETURN,
 	IF, THEN, ELSE, CASE,
 	FOR, IN, DO,
 	TRUE, FALSE, RT, RO, UNKNOWN, GENERIC,
-	FROM, GW, NET, PROTO, SCOPE, DEST, IFNAME, IFINDEX, WEIGHT, GW_MPLS,
+	FROM, GW, NET, PROTO, SCOPE, DEST, IFNAME, IFINDEX, WEIGHT, GW_MPLS, ONLINK,
 	ROA_CHECK, ASPA_CHECK,
 	DEFINED,
 	ADD, DELETE, RESET,
@@ -904,6 +904,7 @@ static_attr:
  | IFINDEX { $$ = f_new_static_attr(T_INT,        SA_IFINDEX,	1); }
  | WEIGHT  { $$ = f_new_static_attr(T_INT,        SA_WEIGHT,	0); }
  | GW_MPLS { $$ = f_new_static_attr(T_INT,        SA_GW_MPLS,	0); }
+ | ONLINK  { $$ = f_new_static_attr(T_BOOL,       SA_ONLINK,    0); }
  ;
 
 term_dot_method: term '.' { f_method_call_start($1); } method_name_cont { f_method_call_end(); $$ = $4; };
diff --git a/filter/data.h b/filter/data.h
index baee14c8e..dcc0501e5 100644
--- a/filter/data.h
+++ b/filter/data.h
@@ -39,6 +39,7 @@ enum f_sa_code {
   SA_IFINDEX,
   SA_WEIGHT,
   SA_GW_MPLS,
+  SA_ONLINK,
 } PACKED;
 
 /* Static attribute definition (members of struct rta) */
diff --git a/filter/f-inst.c b/filter/f-inst.c
index aeea55eaf..37017055a 100644
--- a/filter/f-inst.c
+++ b/filter/f-inst.c
@@ -725,6 +725,9 @@
 	    case SA_GW_MPLS:
 	      RESULT(sa.type, i, (nh && nh->labels) ? nh->label[0] : MPLS_NULL);
 	      break;
+	    case SA_ONLINK:
+	      RESULT(sa.type, i, (nh && !!(nh->flags & RNF_ONLINK)));
+	      break;
 	    default:
 	      bug("Invalid static attribute access (%u/%u)", sa.type, sa.sa_code);
 	  }
@@ -773,10 +776,11 @@
 	  struct nexthop *first = NEXTHOP_IS_REACHABLE(nhad) ? &(nhad->nh) : NULL;
 
 	  ip_addr ip = v1.val.ip;
-	  struct iface *ifa = (ipa_is_link_local(ip) && first) ? first->iface : NULL;
+	  bool onlink = first && (first->flags & RNF_ONLINK);
+	  struct iface *ifa = ((ipa_is_link_local(ip) || onlink) && first) ? first->iface : NULL;
 	  
 	  /* XXX this code supposes that every owner is a protocol XXX */
-	  neighbor *n = neigh_find(SKIP_BACK(struct proto, sources, fs->rte->src->owner), ip, ifa, 0);
+	  neighbor *n = neigh_find(SKIP_BACK(struct proto, sources, fs->rte->src->owner), ip, ifa, onlink ? NEF_ONLINK : 0);
 	  if (!n || (n->scope == SCOPE_HOST))
 	    runtime( "Invalid gw address" );
 
@@ -846,6 +850,33 @@
         }
 	break;
 
+      case SA_ONLINK:
+        {
+	  int i = v1.val.i;
+
+	  struct eattr *nh_ea = ea_find(fs->rte->attrs, &ea_gen_nexthop);
+	  if (!nh_ea)
+	    runtime( "Set iface first to make the nexthop onlink" );
+
+	  struct nexthop_adata *nhad = (struct nexthop_adata *) nh_ea->u.ptr;
+	  if (!NEXTHOP_IS_REACHABLE(nhad))
+	    runtime( "Set iface first to make the nexthop onlink" );
+
+	  struct nexthop_adata *nhax = (struct nexthop_adata *) tmp_copy_adata(&nhad->ad);
+
+	  /* Set onlink on all next hops */
+	  if (i)
+	    NEXTHOP_WALK(nh, nhax)
+	      nh->flags |=  RNF_ONLINK;
+	  else
+	    NEXTHOP_WALK(nh, nhax)
+	      nh->flags &= ~RNF_ONLINK;
+
+	  a = ea_set_attr(&fs->rte->attrs,
+	      EA_LITERAL_DIRECT_ADATA(&ea_gen_nexthop, 0, &nhax->ad));
+        }
+	break;
+
       default:
 	bug("Invalid static attribute access (%u/%u)", sa.type, sa.sa_code);
       }