BGP multipath support

Kernel option 'merge paths' allows to merge routes exported to kernel
protocol (currently BGP and static routes) to multipath routes.

4 files changed, 85 insertions, 0 deletions

diff --git a/proto/bgp/attrs.c b/proto/bgp/attrs.c
index d56c017d..d85afa8f 100644
--- a/proto/bgp/attrs.c
+++ b/proto/bgp/attrs.c
@@ -1312,6 +1312,82 @@ bgp_rte_better(rte *new, rte *old)
 }
 
 
+int
+bgp_rte_mergable(rte *pri, rte *sec)
+{
+  struct bgp_proto *pri_bgp = (struct bgp_proto *) pri->attrs->src->proto;
+  struct bgp_proto *sec_bgp = (struct bgp_proto *) sec->attrs->src->proto;
+  eattr *x, *y;
+  u32 p, s;
+
+  /* Skip suppressed routes (see bgp_rte_recalculate()) */
+  if (pri->u.bgp.suppressed != sec->u.bgp.suppressed)
+    return 0;
+
+  /* RFC 4271 9.1.2.1. Route resolvability test */
+  if (!rte_resolvable(sec))
+    return 0;
+
+  /* Start with local preferences */
+  x = ea_find(pri->attrs->eattrs, EA_CODE(EAP_BGP, BA_LOCAL_PREF));
+  y = ea_find(sec->attrs->eattrs, EA_CODE(EAP_BGP, BA_LOCAL_PREF));
+  p = x ? x->u.data : pri_bgp->cf->default_local_pref;
+  s = y ? y->u.data : sec_bgp->cf->default_local_pref;
+  if (p != s)
+    return 0;
+
+  /* RFC 4271 9.1.2.2. a)  Use AS path lengths */
+  if (pri_bgp->cf->compare_path_lengths || sec_bgp->cf->compare_path_lengths)
+    {
+      x = ea_find(pri->attrs->eattrs, EA_CODE(EAP_BGP, BA_AS_PATH));
+      y = ea_find(sec->attrs->eattrs, EA_CODE(EAP_BGP, BA_AS_PATH));
+      p = x ? as_path_getlen(x->u.ptr) : AS_PATH_MAXLEN;
+      s = y ? as_path_getlen(y->u.ptr) : AS_PATH_MAXLEN;
+
+      if (p != s)
+	return 0;
+
+//      if (DELTA(p, s) > pri_bgp->cf->relax_multipath)
+//	return 0;
+    }
+
+  /* RFC 4271 9.1.2.2. b) Use origins */
+  x = ea_find(pri->attrs->eattrs, EA_CODE(EAP_BGP, BA_ORIGIN));
+  y = ea_find(sec->attrs->eattrs, EA_CODE(EAP_BGP, BA_ORIGIN));
+  p = x ? x->u.data : ORIGIN_INCOMPLETE;
+  s = y ? y->u.data : ORIGIN_INCOMPLETE;
+  if (p != s)
+    return 0;
+
+  /* RFC 4271 9.1.2.2. c) Compare MED's */
+  if (pri_bgp->cf->med_metric || sec_bgp->cf->med_metric ||
+      (bgp_get_neighbor(pri) == bgp_get_neighbor(sec)))
+    {
+      x = ea_find(pri->attrs->eattrs, EA_CODE(EAP_BGP, BA_MULTI_EXIT_DISC));
+      y = ea_find(sec->attrs->eattrs, EA_CODE(EAP_BGP, BA_MULTI_EXIT_DISC));
+      p = x ? x->u.data : pri_bgp->cf->default_med;
+      s = y ? y->u.data : sec_bgp->cf->default_med;
+      if (p != s)
+	return 0;
+    }
+
+  /* RFC 4271 9.1.2.2. d) Prefer external peers */
+  if (pri_bgp->is_internal != sec_bgp->is_internal)
+    return 0;
+
+  /* RFC 4271 9.1.2.2. e) Compare IGP metrics */
+  p = pri_bgp->cf->igp_metric ? pri->attrs->igp_metric : 0;
+  s = sec_bgp->cf->igp_metric ? sec->attrs->igp_metric : 0;
+  if (p != s)
+    return 0;
+
+  /* Remaining criteria are ignored */
+
+  return 1;
+}
+
+
+
 static inline int
 same_group(rte *r, u32 lpref, u32 lasn)
 {
diff --git a/proto/bgp/bgp.c b/proto/bgp/bgp.c
index e48b643b..9e28b278 100644
--- a/proto/bgp/bgp.c
+++ b/proto/bgp/bgp.c
@@ -1243,6 +1243,7 @@ bgp_init(struct proto_config *C)
   P->feed_begin = bgp_feed_begin;
   P->feed_end = bgp_feed_end;
   P->rte_better = bgp_rte_better;
+  P->rte_mergable = bgp_rte_mergable;
   P->rte_recalculate = c->deterministic_med ? bgp_rte_recalculate : NULL;
 
   p->cf = c;
diff --git a/proto/bgp/bgp.h b/proto/bgp/bgp.h
index 446fc857..b6e80fe5 100644
--- a/proto/bgp/bgp.h
+++ b/proto/bgp/bgp.h
@@ -238,6 +238,7 @@ byte *bgp_attach_attr_wa(struct ea_list **to, struct linpool *pool, unsigned att
 struct rta *bgp_decode_attrs(struct bgp_conn *conn, byte *a, uint len, struct linpool *pool, int mandatory);
 int bgp_get_attr(struct eattr *e, byte *buf, int buflen);
 int bgp_rte_better(struct rte *, struct rte *);
+int bgp_rte_mergable(rte *pri, rte *sec);
 int bgp_rte_recalculate(rtable *table, net *net, rte *new, rte *old, rte *old_best);
 void bgp_rt_notify(struct proto *P, rtable *tbl UNUSED, net *n, rte *new, rte *old UNUSED, ea_list *attrs);
 int bgp_import_control(struct proto *, struct rte **, struct ea_list **, struct linpool *);
diff --git a/proto/static/static.c b/proto/static/static.c
index 4b72fa9d..e7e7ab15 100644
--- a/proto/static/static.c
+++ b/proto/static/static.c
@@ -352,6 +352,12 @@ static_if_notify(struct proto *p, unsigned flags, struct iface *i)
     }
 }
 
+int
+static_rte_mergable(rte *pri, rte *sec)
+{
+  return 1;
+}
+
 void
 static_init_config(struct static_config *c)
 {
@@ -366,6 +372,7 @@ static_init(struct proto_config *c)
 
   p->neigh_notify = static_neigh_notify;
   p->if_notify = static_if_notify;
+  p->rte_mergable = static_rte_mergable;
 
   return p;
 }