1 files changed, 526 insertions, 127 deletions

diff --git a/proto/bgp/attrs.c b/proto/bgp/attrs.c
index 30699f84..2210cbe7 100644
--- a/proto/bgp/attrs.c
+++ b/proto/bgp/attrs.c
@@ -55,22 +55,38 @@ bgp_format_origin(eattr *a, byte *buf)
 }
 
 static int
-bgp_check_path(struct bgp_proto *p UNUSED, byte *a, int len)
+bgp_check_path(byte *a, int len, int bs, int errcode)
 {
   while (len)
     {
       DBG("Path segment %02x %02x\n", a[0], a[1]);
       if (len < 2 ||
-	  a[0] != AS_PATH_SET && a[0] != AS_PATH_SEQUENCE ||
-	  2*a[1] + 2 > len)
-	return 11;
-      len -= 2*a[1] + 2;
-      a += 2*a[1] + 2;
+	  (a[0] != AS_PATH_SET && a[0] != AS_PATH_SEQUENCE) ||
+	  bs * a[1] + 2 > len)
+	return errcode;
+      len -= bs * a[1] + 2;
+      a += bs * a[1] + 2;
     }
   return 0;
 }
 
 static int
+bgp_check_as_path(struct bgp_proto *p, byte *a, int len)
+{
+  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_session))
+    return bgp_check_path(a, len, 4, 9);
+  else 
+    return 0;
+}
+
+
+static int
 bgp_check_next_hop(struct bgp_proto *p UNUSED, byte *a, int len)
 {
 #ifdef IPV6
@@ -88,6 +104,20 @@ 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 = p->as4_session ? 8 : 6;
+  
+  return (len == exp_len) ? 0 : 5;
+}
+
+static int
+bgp_check_cluster_list(struct bgp_proto *p UNUSED, UNUSED byte *a, int len)
+{
+  return ((len % 4) == 0) ? 0 : 5;
+}
+
+static int
 bgp_check_reach_nlri(struct bgp_proto *p UNUSED, byte *a UNUSED, int len UNUSED)
 {
 #ifdef IPV6
@@ -113,21 +143,23 @@ static struct attr_desc bgp_attr_table[] = {
   { "origin", 1, BAF_TRANSITIVE, EAF_TYPE_INT, 1,				/* BA_ORIGIN */
     bgp_check_origin, bgp_format_origin },
   { "as_path", -1, BAF_TRANSITIVE, EAF_TYPE_AS_PATH, 1,				/* BA_AS_PATH */
-    bgp_check_path, NULL },
+    bgp_check_as_path, NULL },
   { "next_hop", 4, BAF_TRANSITIVE, EAF_TYPE_IP_ADDRESS, 1,			/* BA_NEXT_HOP */
     bgp_check_next_hop, NULL },
-  { "med", 4, BAF_OPTIONAL, EAF_TYPE_INT, 0,					/* BA_MULTI_EXIT_DISC */
+  { "med", 4, BAF_OPTIONAL, EAF_TYPE_INT, 1,					/* BA_MULTI_EXIT_DISC */
     NULL, NULL },
   { "local_pref", 4, BAF_TRANSITIVE, EAF_TYPE_INT, 0,				/* BA_LOCAL_PREF */
     NULL, NULL },
   { "atomic_aggr", 0, BAF_TRANSITIVE, EAF_TYPE_OPAQUE, 1,			/* BA_ATOMIC_AGGR */
     NULL, NULL },
-  { "aggregator", 6, BAF_OPTIONAL | BAF_TRANSITIVE, EAF_TYPE_OPAQUE, 1,		/* BA_AGGREGATOR */
-    NULL, NULL },
+  { "aggregator", -1, BAF_OPTIONAL | BAF_TRANSITIVE, EAF_TYPE_OPAQUE, 1,	/* BA_AGGREGATOR */
+    bgp_check_aggregator, NULL },
   { "community", -1, BAF_OPTIONAL | BAF_TRANSITIVE, EAF_TYPE_INT_SET, 1,	/* BA_COMMUNITY */
     NULL, NULL },
-  { NULL, },									/* BA_ORIGINATOR_ID */
-  { NULL, },									/* BA_CLUSTER_LIST */
+  { "originator_id", 4, BAF_OPTIONAL, EAF_TYPE_INT, 0,				/* BA_ORIGINATOR_ID */
+    NULL, NULL },
+  { "cluster_list", -1, BAF_OPTIONAL, EAF_TYPE_INT_SET, 0,			/* BA_CLUSTER_LIST */
+    bgp_check_cluster_list, NULL }, 
   { NULL, },									/* BA_DPA */
   { NULL, },									/* BA_ADVERTISER */
   { NULL, },									/* BA_RCID_PATH */
@@ -135,43 +167,152 @@ static struct attr_desc bgp_attr_table[] = {
     bgp_check_reach_nlri, NULL },
   { "mp_unreach_nlri", -1, BAF_OPTIONAL, EAF_TYPE_OPAQUE, 1,			/* BA_MP_UNREACH_NLRI */
     bgp_check_unreach_nlri, NULL },
+  { NULL, },									/* BA_EXTENDED_COMM */
+  { "as4_path", -1, BAF_OPTIONAL | BAF_TRANSITIVE, EAF_TYPE_OPAQUE, 1,		/* BA_AS4_PATH */
+    bgp_check_as4_path, NULL },
+  { "as4_aggregator", 8, BAF_OPTIONAL | BAF_TRANSITIVE, EAF_TYPE_OPAQUE, 1,	/* BA_AS4_PATH */
+    NULL, NULL }
 };
 
+/* BA_AS4_PATH is type EAF_TYPE_OPAQUE and not type EAF_TYPE_AS_PATH because
+ * EAF_TYPE_AS_PATH is supposed to have different format (2 or 4 B for each ASN)
+ * depending on bgp_as4_support variable.
+ */
+
 #define ATTR_KNOWN(code) ((code) < ARRAY_SIZE(bgp_attr_table) && bgp_attr_table[code].name)
 
-static byte *
-bgp_set_attr(eattr *e, struct linpool *pool, unsigned attr, unsigned val)
+static inline struct adata *
+bgp_alloc_adata(struct linpool *pool, unsigned len)
+{
+  struct adata *ad = lp_alloc(pool, sizeof(struct adata) + len);
+  ad->length = len;
+  return ad;
+}
+
+static void
+bgp_set_attr(eattr *e, unsigned attr, uintptr_t val)
 {
   ASSERT(ATTR_KNOWN(attr));
   e->id = EA_CODE(EAP_BGP, attr);
   e->type = bgp_attr_table[attr].type;
   e->flags = bgp_attr_table[attr].expected_flags;
   if (e->type & EAF_EMBEDDED)
-    {
-      e->u.data = val;
-      return NULL;
-    }
+    e->u.data = val;
   else
-    {
-      e->u.ptr = lp_alloc(pool, sizeof(struct adata) + val);
-      e->u.ptr->length = val;
-      return e->u.ptr->data;
-    }
+    e->u.ptr = (struct adata *) val;
 }
 
-byte *
-bgp_attach_attr(ea_list **to, struct linpool *pool, unsigned attr, unsigned val)
+static byte *
+bgp_set_attr_wa(eattr *e, struct linpool *pool, unsigned attr, unsigned len)
+{
+  struct adata *ad = bgp_alloc_adata(pool, len);
+  bgp_set_attr(e, attr, (uintptr_t) ad);
+  return ad->data;
+}
+
+void
+bgp_attach_attr(ea_list **to, struct linpool *pool, unsigned attr, uintptr_t val)
 {
   ea_list *a = lp_alloc(pool, sizeof(ea_list) + sizeof(eattr));
   a->next = *to;
   *to = a;
   a->flags = EALF_SORTED;
   a->count = 1;
-  return bgp_set_attr(a->attrs, pool, attr, val);
+  bgp_set_attr(a->attrs, attr, val);
 }
 
+byte *
+bgp_attach_attr_wa(ea_list **to, struct linpool *pool, unsigned attr, unsigned len)
+{
+  struct adata *ad = bgp_alloc_adata(pool, len);
+  bgp_attach_attr(to, pool, attr, (uintptr_t) ad);
+  return ad->data;
+}
+
+static int
+bgp_encode_attr_hdr(byte *dst, unsigned int flags, unsigned code, int len)
+{
+  int wlen;
+
+  DBG("\tAttribute %02x (%d bytes, flags %02x)\n", code, len, flags);
+
+  if (len < 256)
+    {
+      *dst++ = flags;
+      *dst++ = code;
+      *dst++ = len;
+      wlen = 3;
+    }
+  else
+    {
+      *dst++ = flags | BAF_EXT_LEN;
+      *dst++ = code;
+      put_u16(dst, len);
+      wlen = 4;
+    }
+
+  return wlen;
+}
+
+static void
+aggregator_convert_to_old(struct adata *aggr, byte *dst, int *new_used)
+{
+  byte *src = aggr->data;
+  *new_used = 0;
+
+  u32 as = get_u32(src);
+  if (as > 0xFFFF) 
+    {
+      as = AS_TRANS;
+      *new_used = 1;
+    }
+  put_u16(dst, as);
+
+  /* Copy IPv4 address */
+  memcpy(dst + 2, src + 4, 4);
+}
+
+static void
+aggregator_convert_to_new(struct adata *aggr, byte *dst)
+{
+  byte *src = aggr->data;
+
+  u32 as   = get_u16(src);
+  put_u32(dst, as);
+
+  /* Copy IPv4 address */
+  memcpy(dst + 4, src + 2, 4);
+}
+
+static int
+bgp_get_attr_len(eattr *a)
+{
+  int len;
+  if (ATTR_KNOWN(EA_ID(a->id)))
+    {
+      int code = EA_ID(a->id);
+      struct attr_desc *desc = &bgp_attr_table[code];
+      len = desc->expected_length;
+      if (len < 0)
+	{
+	  ASSERT(!(a->type & EAF_EMBEDDED));
+	  len = a->u.ptr->length;
+	}
+    }
+  else
+    {
+      ASSERT((a->type & EAF_TYPE_MASK) == EAF_TYPE_OPAQUE);
+      len = a->u.ptr->length;
+    }
+  
+  return len;
+}
+
+#define ADVANCE(w, r, l) do { r -= l; w += l; } while (0)
+
 /**
  * bgp_encode_attrs - encode BGP attributes
+ * @p: BGP instance
  * @w: buffer
  * @attrs: a list of extended attributes
  * @remains: remaining space in the buffer
@@ -182,11 +323,11 @@ bgp_attach_attr(ea_list **to, struct linpool *pool, unsigned attr, unsigned val)
  * Result: Length of the attribute block generated.
  */
 unsigned int
-bgp_encode_attrs(byte *w, ea_list *attrs, int remains)
+bgp_encode_attrs(struct bgp_proto *p, byte *w, ea_list *attrs, int remains)
 {
   unsigned int i, code, flags;
   byte *start = w;
-  int len;
+  int len, rv;
 
   for(i=0; i<attrs->count; i++)
     {
@@ -198,43 +339,90 @@ bgp_encode_attrs(byte *w, ea_list *attrs, int remains)
       if (code == BA_NEXT_HOP)
 	continue;
 #endif
-      flags = a->flags & (BAF_OPTIONAL | BAF_TRANSITIVE | BAF_PARTIAL);
-      if (ATTR_KNOWN(code))
-	{
-	  struct attr_desc *desc = &bgp_attr_table[code];
-	  len = desc->expected_length;
-	  if (len < 0)
-	    {
-	      ASSERT(!(a->type & EAF_EMBEDDED));
-	      len = a->u.ptr->length;
-	    }
-	}
-      else
+
+      /* When AS4-aware BGP speaker is talking to non-AS4-aware BGP speaker,
+       * 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_session))
 	{
-	  ASSERT((a->type & EAF_TYPE_MASK) == EAF_TYPE_OPAQUE);
 	  len = a->u.ptr->length;
+
+	  if (remains < (len + 4))
+	    goto err_no_buffer;
+
+	  /* Using temporary buffer because don't know a length of created attr
+	   * and therefore a length of a header. Perhaps i should better always
+	   * use BAF_EXT_LEN. */
+	  
+	  byte buf[len];
+	  int new_used;
+	  int nl = as_path_convert_to_old(a->u.ptr, buf, &new_used);
+
+	  rv = bgp_encode_attr_hdr(w, BAF_TRANSITIVE, BA_AS_PATH, nl);
+	  ADVANCE(w, remains, rv);
+	  memcpy(w, buf, nl);
+	  ADVANCE(w, remains, nl);
+
+	  if (! new_used)
+	    continue;
+
+	  if (remains < (len + 4))
+	    goto err_no_buffer;
+
+	  /* We should discard AS_CONFED_SEQUENCE or AS_CONFED_SET path segments 
+	   * here but we don't support confederations and such paths we already
+	   * discarded in bgp_check_as_path().
+	   */
+
+	  rv = bgp_encode_attr_hdr(w, BAF_OPTIONAL | BAF_TRANSITIVE, BA_AS4_PATH, len);
+	  ADVANCE(w, remains, rv);
+	  memcpy(w, a->u.ptr->data, len);
+	  ADVANCE(w, remains, len);
+
+	  continue;
 	}
-      DBG("\tAttribute %02x (type %02x, %d bytes, flags %02x)\n", code, a->type, len, flags);
-      if (remains < len + 4)
-	{
-	  log(L_ERR "BGP: attribute list too long, ignoring the remaining attributes");
-	  break;
-	}
-      if (len < 256)
-	{
-	  *w++ = flags;
-	  *w++ = code;
-	  *w++ = len;
-	  remains -= 3;
-	}
-      else
+
+      /* The same issue with AGGREGATOR attribute */
+      if ((code == BA_AGGREGATOR) && bgp_as4_support && (! p->as4_session))
 	{
-	  *w++ = flags | BAF_EXT_LEN;
-	  *w++ = code;
-	  put_u16(w, len);
-	  w += 2;
-	  remains -= 4;
+	  int new_used;
+
+	  len = 6;
+	  if (remains < (len + 3))
+	    goto err_no_buffer;
+
+	  rv = bgp_encode_attr_hdr(w, BAF_OPTIONAL | BAF_TRANSITIVE, BA_AGGREGATOR, len);
+	  ADVANCE(w, remains, rv);
+	  aggregator_convert_to_old(a->u.ptr, w, &new_used);
+	  ADVANCE(w, remains, len);
+
+	  if (! new_used)
+	    continue;
+
+	  len = 8;
+	  if (remains < (len + 3))
+	    goto err_no_buffer;
+
+	  rv = bgp_encode_attr_hdr(w, BAF_OPTIONAL | BAF_TRANSITIVE, BA_AS4_AGGREGATOR, len);
+	  ADVANCE(w, remains, rv);
+	  memcpy(w, a->u.ptr->data, len);
+	  ADVANCE(w, remains, len);
+
+	  continue;
 	}
+
+      /* Standard path continues here ... */
+
+      flags = a->flags & (BAF_OPTIONAL | BAF_TRANSITIVE | BAF_PARTIAL);
+      len = bgp_get_attr_len(a);
+
+      if (remains < len + 4)
+	goto err_no_buffer;
+
+      rv = bgp_encode_attr_hdr(w, flags, code, len);
+      ADVANCE(w, remains, rv);
+
       switch (a->type & EAF_TYPE_MASK)
 	{
 	case EAF_TYPE_INT:
@@ -266,10 +454,13 @@ bgp_encode_attrs(byte *w, ea_list *attrs, int remains)
 	default:
 	  bug("bgp_encode_attrs: unknown attribute type %02x", a->type);
 	}
-      remains -= len;
-      w += len;
+      ADVANCE(w, remains, len);
     }
   return w - start;
+
+ err_no_buffer:
+  log(L_ERR "BGP: attribute list too long, ignoring the remaining attributes");
+  return w - start;
 }
 
 static void
@@ -547,6 +738,7 @@ bgp_rt_notify(struct proto *P, net *n, rte *new, rte *old UNUSED, ea_list *attrs
   bgp_schedule_packet(p->conn, PKT_UPDATE);
 }
 
+
 static int
 bgp_create_attrs(struct bgp_proto *p, rte *e, ea_list **attrs, struct linpool *pool)
 {
@@ -559,20 +751,24 @@ bgp_create_attrs(struct bgp_proto *p, rte *e, ea_list **attrs, struct linpool *p
   ea->flags = EALF_SORTED;
   ea->count = 4;
 
-  bgp_set_attr(ea->attrs, pool, BA_ORIGIN,
+  bgp_set_attr(ea->attrs, BA_ORIGIN,
        ((rta->source == RTS_OSPF_EXT1) || (rta->source == RTS_OSPF_EXT2)) ? ORIGIN_INCOMPLETE : ORIGIN_IGP);
 
   if (p->is_internal)
-    bgp_set_attr(ea->attrs+1, pool, BA_AS_PATH, 0);
+    bgp_set_attr_wa(ea->attrs+1, pool, BA_AS_PATH, 0);
   else
     {
-      z = bgp_set_attr(ea->attrs+1, pool, BA_AS_PATH, 4);
+      z = bgp_set_attr_wa(ea->attrs+1, pool, BA_AS_PATH, bgp_as4_support ? 6 : 4);
       z[0] = AS_PATH_SEQUENCE;
       z[1] = 1;				/* 1 AS */
-      put_u16(z+2, p->local_as);
+
+      if (bgp_as4_support)
+	put_u32(z+2, p->local_as);
+      else
+	put_u16(z+2, p->local_as);
     }
 
-  z = bgp_set_attr(ea->attrs+2, pool, BA_NEXT_HOP, sizeof(ip_addr));
+  z = bgp_set_attr_wa(ea->attrs+2, pool, BA_NEXT_HOP, sizeof(ip_addr));
   if (p->cf->next_hop_self ||
       !p->is_internal ||
       rta->dest != RTD_ROUTER)
@@ -585,34 +781,65 @@ bgp_create_attrs(struct bgp_proto *p, rte *e, ea_list **attrs, struct linpool *p
   else
     *(ip_addr *)z = e->attrs->gw;
 
-  bgp_set_attr(ea->attrs+3, pool, BA_LOCAL_PREF, 0);
+  bgp_set_attr(ea->attrs+3, BA_LOCAL_PREF, 0);
 
   return 0;				/* Leave decision to the filters */
 }
 
-static ea_list *
-bgp_path_prepend(struct linpool *pool, eattr *a, ea_list *old, int as)
+
+static inline int
+bgp_as_path_loopy(struct bgp_proto *p, rta *a)
 {
-  struct ea_list *e = lp_alloc(pool, sizeof(ea_list) + sizeof(eattr));
-  struct adata *olda = a->u.ptr;
+  eattr *e = ea_find(a->eattrs, EA_CODE(EAP_BGP, BA_AS_PATH));
+  return (e && as_path_is_member(e->u.ptr, p->local_as));
+}
 
-  e->next = old;
-  e->flags = EALF_SORTED;
-  e->count = 1;
-  e->attrs[0].id = EA_CODE(EAP_BGP, BA_AS_PATH);
-  e->attrs[0].flags = BAF_TRANSITIVE;
-  e->attrs[0].type = EAF_TYPE_AS_PATH;
-  e->attrs[0].u.ptr = as_path_prepend(pool, olda, as);
-  return e;
+static inline int
+bgp_originator_id_loopy(struct bgp_proto *p, rta *a)
+{
+  eattr *e = ea_find(a->eattrs, EA_CODE(EAP_BGP, BA_ORIGINATOR_ID));
+  return (e && (e->u.data == p->local_id));
+}
+
+static inline int
+bgp_cluster_list_loopy(struct bgp_proto *p, rta *a)
+{
+  eattr *e = ea_find(a->eattrs, EA_CODE(EAP_BGP, BA_CLUSTER_LIST));
+  return (e && p->rr_client && int_set_contains(e->u.ptr, p->rr_cluster_id));
+}
+
+
+static inline void
+bgp_path_prepend(rte *e, ea_list **attrs, struct linpool *pool, u32 as)
+{
+  eattr *a = ea_find(e->attrs->eattrs, EA_CODE(EAP_BGP, BA_AS_PATH));
+  bgp_attach_attr(attrs, pool, BA_AS_PATH, (uintptr_t) as_path_prepend(pool, a->u.ptr, as));
+}
+
+static inline void
+bgp_cluster_list_prepend(rte *e, ea_list **attrs, struct linpool *pool, u32 cid)
+{
+  eattr *a = ea_find(e->attrs->eattrs, EA_CODE(EAP_BGP, BA_CLUSTER_LIST));
+  bgp_attach_attr(attrs, pool, BA_CLUSTER_LIST, (uintptr_t) int_set_add(pool, a ? a->u.ptr : NULL, cid));
 }
 
 static int
-bgp_update_attrs(struct bgp_proto *p, rte *e, ea_list **attrs, struct linpool *pool)
+bgp_update_attrs(struct bgp_proto *p, rte *e, ea_list **attrs, struct linpool *pool, int rr)
 {
   eattr *a;
 
-  if (!p->is_internal && (a = ea_find(e->attrs->eattrs, EA_CODE(EAP_BGP, BA_AS_PATH))))
-    *attrs = bgp_path_prepend(pool, a, *attrs, p->local_as);
+  if (!p->is_internal)
+    {
+      bgp_path_prepend(e, attrs, pool, p->local_as);
+
+      /* The MULTI_EXIT_DISC attribute received from a neighboring AS MUST NOT be
+       * propagated to other neighboring ASes.
+       * Perhaps it would be better to undefine it.
+       */
+      a = ea_find(e->attrs->eattrs, EA_CODE(EAP_BGP, BA_MULTI_EXIT_DISC));
+      if (a)
+	bgp_attach_attr(attrs, pool, BA_MULTI_EXIT_DISC, 0);
+    }
 
   a = ea_find(e->attrs->eattrs, EA_CODE(EAP_BGP, BA_NEXT_HOP));
   if (a && (p->is_internal || (!p->is_internal && e->attrs->iface == p->neigh->iface)))
@@ -622,7 +849,24 @@ bgp_update_attrs(struct bgp_proto *p, rte *e, ea_list **attrs, struct linpool *p
   else
     {
       /* Need to create new one */
-      *(ip_addr *) bgp_attach_attr(attrs, pool, BA_NEXT_HOP, sizeof(ip_addr)) = p->local_addr;
+      bgp_attach_attr_ip(attrs, pool, BA_NEXT_HOP, p->local_addr);
+    }
+
+  if (rr)
+    {
+      /* Handling route reflection, RFC 4456 */
+      struct bgp_proto *src = (struct bgp_proto *) e->attrs->proto;
+
+      a = ea_find(e->attrs->eattrs, EA_CODE(EAP_BGP, BA_ORIGINATOR_ID));
+      if (!a)
+	bgp_attach_attr(attrs, pool, BA_ORIGINATOR_ID, src->remote_id);
+
+      /* We attach proper cluster ID according to whether the route is entering or leaving the cluster */
+      bgp_cluster_list_prepend(e, attrs, pool, src->rr_client ? src->rr_cluster_id : p->rr_cluster_id);
+
+      /* Two RR clients with different cluster ID, hmmm */
+      if (src->rr_client && p->rr_client && (src->rr_cluster_id != p->rr_cluster_id))
+	bgp_cluster_list_prepend(e, attrs, pool, p->rr_cluster_id);
     }
 
   return 0;				/* Leave decision to the filters */
@@ -639,14 +883,39 @@ bgp_import_control(struct proto *P, rte **new, ea_list **attrs, struct linpool *
     return -1;
   if (new_bgp)
     {
+      /* We should check here for cluster list loop, because the receiving BGP instance
+	 might have different cluster ID  */
+      if (bgp_cluster_list_loopy(p, e->attrs))
+	return -1;
+
       if (p->local_as == new_bgp->local_as && p->is_internal && new_bgp->is_internal)
-	return -1;			/* Don't redistribute internal routes with IBGP */
-      return bgp_update_attrs(p, e, attrs, pool);
+	{
+	  /* Redistribution of internal routes with IBGP */
+	  if (p->rr_client || new_bgp->rr_client)
+	    /* Route reflection, RFC 4456 */
+	    return bgp_update_attrs(p, e, attrs, pool, 1);
+	  else
+	    return -1;
+	}
+      else
+	return bgp_update_attrs(p, e, attrs, pool, 0);
     }
   else
     return bgp_create_attrs(p, e, attrs, pool);
 }
 
+static inline u32
+bgp_get_neighbor(rte *r)
+{
+  eattr *e = ea_find(r->attrs->eattrs, EA_CODE(EAP_BGP, BA_AS_PATH));
+  u32 as;
+
+  if (e && as_path_get_last(e->u.ptr, &as))
+    return as;
+  else
+    return ((struct bgp_proto *) r->attrs->proto)->remote_as;
+}
+
 int
 bgp_rte_better(rte *new, rte *old)
 {
@@ -665,20 +934,20 @@ bgp_rte_better(rte *new, rte *old)
   if (n < o)
     return 0;
 
-  /* Use AS path lengths */
+  /* RFC 4271 9.1.2.2. a)  Use AS path lengths */
   if (new_bgp->cf->compare_path_lengths || old_bgp->cf->compare_path_lengths)
     {
       x = ea_find(new->attrs->eattrs, EA_CODE(EAP_BGP, BA_AS_PATH));
       y = ea_find(old->attrs->eattrs, EA_CODE(EAP_BGP, BA_AS_PATH));
-      n = x ? as_path_getlen(x->u.ptr) : 100000;
-      o = y ? as_path_getlen(y->u.ptr) : 100000;
+      n = x ? as_path_getlen(x->u.ptr) : AS_PATH_MAXLEN;
+      o = y ? as_path_getlen(y->u.ptr) : AS_PATH_MAXLEN;
       if (n < o)
 	return 1;
       if (n > o)
 	return 0;
     }
 
-  /* Use origins */
+  /* RFC 4271 9.1.2.2. b) Use origins */
   x = ea_find(new->attrs->eattrs, EA_CODE(EAP_BGP, BA_ORIGIN));
   y = ea_find(old->attrs->eattrs, EA_CODE(EAP_BGP, BA_ORIGIN));
   n = x ? x->u.data : ORIGIN_INCOMPLETE;
@@ -688,47 +957,163 @@ bgp_rte_better(rte *new, rte *old)
   if (n > o)
     return 0;
 
-  /* Compare MED's */
-  x = ea_find(new->attrs->eattrs, EA_CODE(EAP_BGP, BA_MULTI_EXIT_DISC));
-  y = ea_find(old->attrs->eattrs, EA_CODE(EAP_BGP, BA_MULTI_EXIT_DISC));
-  n = x ? x->u.data : new_bgp->cf->default_med;
-  o = y ? y->u.data : old_bgp->cf->default_med;
+  /* RFC 4271 9.1.2.2. c) Compare MED's */
+
+  if (bgp_get_neighbor(new) == bgp_get_neighbor(old))
+    {
+      x = ea_find(new->attrs->eattrs, EA_CODE(EAP_BGP, BA_MULTI_EXIT_DISC));
+      y = ea_find(old->attrs->eattrs, EA_CODE(EAP_BGP, BA_MULTI_EXIT_DISC));
+      n = x ? x->u.data : new_bgp->cf->default_med;
+      o = y ? y->u.data : old_bgp->cf->default_med;
+      if (n < o)
+	return 1;
+      if (n > o)
+	return 0;
+    }
+
+  /* RFC 4271 9.1.2.2. d) Prefer external peers */
+  if (new_bgp->is_internal > old_bgp->is_internal)
+    return 0;
+  if (new_bgp->is_internal < old_bgp->is_internal)
+    return 1;
+
+  /* Skipping RFC 4271 9.1.2.2. e) */
+  /* We don't have interior distances */
+
+  /* RFC 4456 9. b) Compare cluster list lengths */
+  x = ea_find(new->attrs->eattrs, EA_CODE(EAP_BGP, BA_CLUSTER_LIST));
+  y = ea_find(old->attrs->eattrs, EA_CODE(EAP_BGP, BA_CLUSTER_LIST));
+  n = x ? int_set_get_size(x->u.ptr) : 0;
+  o = y ? int_set_get_size(y->u.ptr) : 0;
   if (n < o)
     return 1;
   if (n > o)
     return 0;
 
-  /* A tie breaking procedure according to RFC 1771, section 9.1.2.1 */
-  /* We don't have interior distances */
-  /* We prefer external peers */
-  if (new_bgp->is_internal > old_bgp->is_internal)
-    return 0;
-  if (new_bgp->is_internal < old_bgp->is_internal)
+  /* RFC 4271 9.1.2.2. f) Compare BGP identifiers */
+  /* RFC 4456 9. a) Use ORIGINATOR_ID instead of local neighor ID */
+  x = ea_find(new->attrs->eattrs, EA_CODE(EAP_BGP, BA_ORIGINATOR_ID));
+  y = ea_find(old->attrs->eattrs, EA_CODE(EAP_BGP, BA_ORIGINATOR_ID));
+  n = x ? x->u.data : new_bgp->remote_id;
+  o = y ? y->u.data : old_bgp->remote_id;
+  if (n < o)
     return 1;
-  /* Finally we compare BGP identifiers */
-  return (new_bgp->remote_id < old_bgp->remote_id);
+  if (n > o)
+    return 0;
+
+
+  /* RFC 4271 9.1.2.2. g) Compare peer IP adresses */
+  return (ipa_compare(new_bgp->cf->remote_ip, old_bgp->cf->remote_ip) < 0);
 }
 
-static int
-bgp_path_loopy(struct bgp_proto *p, eattr *a)
+static struct adata *
+bgp_aggregator_convert_to_new(struct adata *old, struct linpool *pool)
+{
+  struct adata *newa = lp_alloc(pool, sizeof(struct adata) + 8);
+  newa->length = 8;
+  aggregator_convert_to_new(old, newa->data);
+  return newa;
+}
+
+
+/* Take last req_as ASNs from path old2 (in 2B format), convert to 4B format
+ * and append path old4 (in 4B format).
+ */
+static struct adata *
+bgp_merge_as_paths(struct adata *old2, struct adata *old4, int req_as, struct linpool *pool)
+{
+  byte buf[old2->length * 2];
+
+  int ol = as_path_convert_to_new(old2, buf, req_as);
+  int nl = ol + (old4 ? old4->length : 0);
+
+  struct adata *newa = lp_alloc(pool, sizeof(struct adata) + nl);
+  newa->length = nl;
+  memcpy(newa->data, buf, ol);
+  if (old4) memcpy(newa->data + ol, old4->data, old4->length);
+
+  return newa;
+}
+
+
+/* Reconstruct 4B AS_PATH and AGGREGATOR according to RFC 4893 4.2.3 */
+static void
+bgp_reconstruct_4b_atts(struct bgp_proto *p, rta *a, struct linpool *pool)
+{
+  eattr *p2 =ea_find(a->eattrs, EA_CODE(EAP_BGP, BA_AS_PATH));
+  eattr *p4 =ea_find(a->eattrs, EA_CODE(EAP_BGP, BA_AS4_PATH));
+  eattr *a2 =ea_find(a->eattrs, EA_CODE(EAP_BGP, BA_AGGREGATOR));
+  eattr *a4 =ea_find(a->eattrs, EA_CODE(EAP_BGP, BA_AS4_AGGREGATOR));
+
+  if (a2)
+    {
+      u32 a2_as = get_u16(a2->u.ptr->data);
+
+      if (a4)
+	{
+	  if (a2_as != AS_TRANS)
+	    {
+	      /* Routes were aggregated by old router and therefore AS4_PATH
+	       * and AS4_AGGREGATOR is invalid
+	       *
+	       * Convert AS_PATH and AGGREGATOR to 4B format and finish.
+	       */
+
+	      a2->u.ptr = bgp_aggregator_convert_to_new(a2->u.ptr, pool);
+	      p2->u.ptr = bgp_merge_as_paths(p2->u.ptr, NULL, AS_PATH_MAXLEN, pool);
+
+	      return;
+	    }
+	  else
+	    {
+	      /* Common case, use AS4_AGGREGATOR attribute */
+	      a2->u.ptr = a4->u.ptr;
+	    }
+	}
+      else
+	{
+	  /* Common case, use old AGGREGATOR attribute */
+	  a2->u.ptr = bgp_aggregator_convert_to_new(a2->u.ptr, pool);
+
+	  if (a2_as == AS_TRANS)
+	    log(L_WARN "BGP: AGGREGATOR attribute contain AS_TRANS, but AS4_AGGREGATOR is missing");
+	}
+    }
+  else
+    if (a4)
+      log(L_WARN "BGP: AS4_AGGREGATOR attribute received, but AGGREGATOR attribute is missing");
+
+  int p2_len = as_path_getlen(p2->u.ptr);
+  int p4_len = p4 ? as_path_getlen(p4->u.ptr) : AS_PATH_MAXLEN;
+
+  if (p2_len < p4_len)
+    p2->u.ptr = bgp_merge_as_paths(p2->u.ptr, NULL, AS_PATH_MAXLEN, pool);
+  else
+    p2->u.ptr = bgp_merge_as_paths(p2->u.ptr, p4->u.ptr, p2_len - p4_len, pool);
+
+}
+
+static void
+bgp_remove_as4_attrs(struct bgp_proto *p, rta *a)
 {
-  byte *path = a->u.ptr->data;
-  int len = a->u.ptr->length;
-  int i, n;
+  unsigned id1 = EA_CODE(EAP_BGP, BA_AS4_PATH);
+  unsigned id2 = EA_CODE(EAP_BGP, BA_AS4_AGGREGATOR);
+  ea_list **el = &(a->eattrs);
 
-  while (len > 0)
+  /* We know that ea_lists constructed in bgp_decode_attrs have one attribute per ea_list struct */
+  while (*el != NULL)
     {
-      n = path[1];
-      len -= 2 + 2*n;
-      path += 2;
-      for(i=0; i<n; i++)
+      unsigned fid = (*el)->attrs[0].id;
+
+      if ((fid == id1) || (fid == id2))
 	{
-	  if (get_u16(path) == p->local_as)
-	    return 1;
-	  path += 2;
+	  *el = (*el)->next;
+	  if (p->as4_session)
+	    log(L_WARN "BGP: Unexpected AS4_* attributes received");
 	}
+      else
+	el = &((*el)->next);
     }
-  return 0;
 }
 
 /**
@@ -883,20 +1268,34 @@ 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_session))
+    bgp_reconstruct_4b_atts(bgp, a, pool);
+
+  if (bgp_as4_support)
+    bgp_remove_as4_attrs(bgp, a);
 
   /* If the AS path attribute contains our AS, reject the routes */
-  e = ea_find(a->eattrs, EA_CODE(EAP_BGP, BA_AS_PATH));
-  if (e && bgp_path_loopy(bgp, e))
-    {
-      DBG("BGP: Path loop!\n");
-      return NULL;
-    }
+  if (bgp_as_path_loopy(bgp, a))
+    goto loop;
+
+  /* Two checks for IBGP loops caused by route reflection, RFC 4456 */ 
+  if (bgp_originator_id_loopy(bgp, a) ||
+      bgp_cluster_list_loopy(bgp, a))
+    goto loop;
 
   /* If there's no local preference, define one */
-  if (!(seen[0] && (1 << BA_LOCAL_PREF)))
+  if (!(seen[0] & (1 << BA_LOCAL_PREF)))
     bgp_attach_attr(&a->eattrs, pool, BA_LOCAL_PREF, 0);
   return a;
 
+loop:
+  DBG("BGP: Path loop!\n");
+  return NULL;
+
 malformed:
   bgp_error(conn, 3, 1, NULL, 0);
   return NULL;
@@ -945,11 +1344,11 @@ bgp_get_route_info(rte *e, byte *buf, ea_list *attrs)
 {
   eattr *p = ea_find(attrs, EA_CODE(EAP_BGP, BA_AS_PATH));
   eattr *o = ea_find(attrs, EA_CODE(EAP_BGP, BA_ORIGIN));
-  int origas;
+  u32 origas;
 
   buf += bsprintf(buf, " (%d) [", e->pref);
-  if (p && (origas = as_path_get_first(p->u.ptr)) >= 0)
-    buf += bsprintf(buf, "AS%d", origas);
+  if (p && as_path_get_first(p->u.ptr, &origas))
+    buf += bsprintf(buf, "AS%u", origas);
   if (o)
     buf += bsprintf(buf, "%c", "ie?"[o->u.data]);
   strcpy(buf, "]");