Implementation of an option for disabling AS4 support per BGP instance.

5 files changed, 20 insertions, 13 deletions

diff --git a/proto/bgp/attrs.c b/proto/bgp/attrs.c
index a42a488..0fcd1ce 100644
--- a/proto/bgp/attrs.c
+++ b/proto/bgp/attrs.c
@@ -73,13 +73,13 @@ bgp_check_path(byte *a, int len, int bs, int errcode)
 static int
 bgp_check_as_path(struct bgp_proto *p, byte *a, int len)
 {
-  return bgp_check_path(a, len, (bgp_as4_support && p->as4_support) ? 4 : 2, 11);
+  return bgp_check_path(a, len, p->as4_session ? 4 : 2, 11);
 }
 
 static int
 bgp_check_as4_path(struct bgp_proto *p, byte *a, int len)
 {
-  if (bgp_as4_support && (! p->as4_support))
+  if (bgp_as4_support && (! p->as4_session))
     return bgp_check_path(a, len, 4, 9);
   else 
     return 0;
@@ -106,7 +106,7 @@ bgp_check_next_hop(struct bgp_proto *p UNUSED, byte *a, int len)
 static int
 bgp_check_aggregator(struct bgp_proto *p, UNUSED byte *a, int len)
 {
-  int exp_len = (bgp_as4_support && p->as4_support) ? 8 : 6;
+  int exp_len = p->as4_session ? 8 : 6;
   
   return (len == exp_len) ? 0 : 5;
 }
@@ -344,7 +344,7 @@ bgp_encode_attrs(struct bgp_proto *p, byte *w, ea_list *attrs, int remains)
        * we have to convert our 4B AS_PATH to 2B AS_PATH and send our AS_PATH 
        * as optional AS4_PATH attribute.
        */
-      if ((code == BA_AS_PATH) && bgp_as4_support && (! p->as4_support))
+      if ((code == BA_AS_PATH) && bgp_as4_support && (! p->as4_session))
 	{
 	  len = a->u.ptr->length;
 
@@ -384,7 +384,7 @@ bgp_encode_attrs(struct bgp_proto *p, byte *w, ea_list *attrs, int remains)
 	}
 
       /* The same issue with AGGREGATOR attribute */
-      if ((code == BA_AGGREGATOR) && bgp_as4_support && (! p->as4_support))
+      if ((code == BA_AGGREGATOR) && bgp_as4_support && (! p->as4_session))
 	{
 	  int new_used;
 
@@ -1082,7 +1082,7 @@ bgp_remove_as4_attrs(struct bgp_proto *p, rta *a)
       if ((fid == id1) || (fid == id2))
 	{
 	  *el = (*el)->next;
-	  if (p->as4_support)
+	  if (p->as4_session)
 	    log(L_WARN "BGP: Unexpected AS4_* attributes received");
 	}
       else
@@ -1246,7 +1246,7 @@ bgp_decode_attrs(struct bgp_conn *conn, byte *attr, unsigned int len, struct lin
   /* When receiving attributes from non-AS4-aware BGP speaker,
    * we have to reconstruct 4B AS_PATH and AGGREGATOR attributes
    */
-  if (bgp_as4_support && (! bgp->as4_support))
+  if (bgp_as4_support && (! bgp->as4_session))
     bgp_reconstruct_4b_atts(bgp, a, pool);
 
   if (bgp_as4_support)
diff --git a/proto/bgp/bgp.c b/proto/bgp/bgp.c
index 5fa1249..0d580be 100644
--- a/proto/bgp/bgp.c
+++ b/proto/bgp/bgp.c
@@ -636,9 +636,11 @@ bgp_check(struct bgp_config *c)
     cf_error("Local AS number must be set");
   if (!c->remote_as)
     cf_error("Neighbor must be configured");
-  if (!bgp_as4_support && (c->local_as > 0xFFFF))
+  if (!bgp_as4_support && c->enable_as4)
+    cf_error("AS4 support disabled globbaly");
+  if (!c->enable_as4 && (c->local_as > 0xFFFF))
     cf_error("Local AS number out of range");
-  if (!bgp_as4_support && (c->remote_as > 0xFFFF))
+  if (!c->enable_as4 && (c->remote_as > 0xFFFF))
     cf_error("Neighbor AS number out of range");
   if ((c->local_as != c->remote_as) && (c->rr_client))
     cf_error("Only internal neighbor can be RR client");
diff --git a/proto/bgp/bgp.h b/proto/bgp/bgp.h
index af3c5c5..1d67e33 100644
--- a/proto/bgp/bgp.h
+++ b/proto/bgp/bgp.h
@@ -25,6 +25,7 @@ struct bgp_config {
   int compare_path_lengths;		/* Use path lengths when selecting best route */
   u32 default_local_pref;		/* Default value for LOCAL_PREF attribute */
   u32 default_med;			/* Default value for MULTI_EXIT_DISC attribute */
+  int enable_as4;			/* Enable local support for 4B AS numbers [RFC4893] */
   u32 rr_cluster_id;			/* Route reflector cluster ID, if different from local ID */
   int rr_client;			/* Whether neighbor is RR client of me */
   unsigned connect_retry_time;
@@ -60,6 +61,7 @@ struct bgp_proto {
   u32 local_as, remote_as;
   int is_internal;			/* Internal BGP connection (local_as == remote_as) */
   int as4_support;			/* Peer supports 4B AS numbers [RFC4893] */
+  int as4_session;			/* Session uses 4B AS numbers in AS_PATH (both sides support it) */
   u32 local_id;				/* BGP identifier of this router */
   u32 remote_id;			/* BGP identifier of the neighbor */
   u32 rr_cluster_id;			/* Route reflector cluster ID */
diff --git a/proto/bgp/config.Y b/proto/bgp/config.Y
index b23b66c..d7bba57 100644
--- a/proto/bgp/config.Y
+++ b/proto/bgp/config.Y
@@ -18,10 +18,10 @@ CF_DECLS
 
 CF_KEYWORDS(BGP, LOCAL, NEIGHBOR, AS, HOLD, TIME, CONNECT, RETRY, KEEPALIVE,
 	MULTIHOP, STARTUP, VIA, NEXT, HOP, SELF, DEFAULT, PATH, METRIC,
-	ERROR, START, DELAY, FORGET, WAIT, DISABLE, AFTER,
+	ERROR, START, DELAY, FORGET, WAIT, ENABLE, DISABLE, AFTER,
 	BGP_PATH, BGP_LOCAL_PREF, BGP_MED, BGP_ORIGIN, BGP_NEXT_HOP,
 	BGP_ATOMIC_AGGR, BGP_AGGREGATOR, BGP_COMMUNITY, SOURCE, ADDRESS,
-	PASSWORD, RR, CLIENT, CLUSTER, ID)
+	PASSWORD, RR, CLIENT, CLUSTER, ID, AS4)
 
 CF_GRAMMAR
 
@@ -39,6 +39,7 @@ bgp_proto_start: proto_start BGP {
      BGP_CFG->error_amnesia_time = 300;
      BGP_CFG->error_delay_time_min = 60;
      BGP_CFG->error_delay_time_max = 300;
+     BGP_CFG->enable_as4 = bgp_as4_support;
  }
  ;
 
@@ -68,6 +69,7 @@ bgp_proto:
  | bgp_proto ERROR FORGET TIME expr ';' { BGP_CFG->error_amnesia_time = $5; } 
  | bgp_proto ERROR WAIT TIME expr ',' expr ';' { BGP_CFG->error_delay_time_min = $5; BGP_CFG->error_delay_time_max = $7; }
  | bgp_proto DISABLE AFTER ERROR bool ';' { BGP_CFG->disable_after_error = $5; }
+ | bgp_proto ENABLE AS4 bool ';' { BGP_CFG->enable_as4 = $4; }
  | bgp_proto PASSWORD TEXT ';' { BGP_CFG->password = $3; }
  ;
 
diff --git a/proto/bgp/packets.c b/proto/bgp/packets.c
index 8a352c6..c18c6e4 100644
--- a/proto/bgp/packets.c
+++ b/proto/bgp/packets.c
@@ -73,7 +73,7 @@ bgp_create_open(struct bgp_conn *conn, byte *buf)
 #ifdef IPV6
   cap = bgp_put_cap_ipv6(conn, cap);
 #endif
-  if (bgp_as4_support)
+  if (p->cf->enable_as4)
     cap = bgp_put_cap_as4(conn, cap);
 
   cap_len = cap - buf - 12;
@@ -407,7 +407,8 @@ bgp_parse_capabilities(struct bgp_conn *conn, byte *opt, int len)
 	  if (cl != 4)
 	    goto err;
 	  p->as4_support = 1;
-	  if (bgp_as4_support)
+	  p->as4_session = p->cf->enable_as4;
+	  if (p->as4_session)
 	    conn->advertised_as = get_u32(opt + 2);
 	  break;