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authorOndrej Zajicek <santiago@crfreenet.org>2008-10-26 22:59:21 +0100
committerOndrej Zajicek <santiago@crfreenet.org>2008-10-26 22:59:21 +0100
commitb6bf284a905412cfe107b4967e55649e6194187e (patch)
treef0098a6d05a72982c6cd9f7e85c195b8a4861b94 /proto/bgp
parent4819c3e17ac22c6810ee80261ac3bffb5127e39d (diff)
downloadbird-b6bf284a905412cfe107b4967e55649e6194187e.tar
bird-b6bf284a905412cfe107b4967e55649e6194187e.zip
Bugfixes in MULIT_EXIT_DISC attribute handling.
- Old MED handling was completely different from behavior specified in RFCs - for example they havn't been propagated to neighboring areas. - Update tie-breaking according to RFC 4271. - Change default value for 'default bgp_med' configuration option according to RFC 4271.
Diffstat (limited to 'proto/bgp')
-rw-r--r--proto/bgp/attrs.c46
-rw-r--r--proto/bgp/config.Y2
2 files changed, 37 insertions, 11 deletions
diff --git a/proto/bgp/attrs.c b/proto/bgp/attrs.c
index b5d8fba..2210cbe 100644
--- a/proto/bgp/attrs.c
+++ b/proto/bgp/attrs.c
@@ -146,7 +146,7 @@ static struct attr_desc bgp_attr_table[] = {
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 },
@@ -829,7 +829,17 @@ bgp_update_attrs(struct bgp_proto *p, rte *e, ea_list **attrs, struct linpool *p
eattr *a;
if (!p->is_internal)
- bgp_path_prepend(e, attrs, pool, p->local_as);
+ {
+ 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)))
@@ -894,6 +904,18 @@ bgp_import_control(struct proto *P, rte **new, ea_list **attrs, struct linpool *
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)
{
@@ -936,14 +958,18 @@ bgp_rte_better(rte *new, rte *old)
return 0;
/* RFC 4271 9.1.2.2. c) 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;
- if (n < o)
- return 1;
- if (n > o)
- return 0;
+
+ 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)
diff --git a/proto/bgp/config.Y b/proto/bgp/config.Y
index d7bba57..8524b2d 100644
--- a/proto/bgp/config.Y
+++ b/proto/bgp/config.Y
@@ -33,7 +33,7 @@ bgp_proto_start: proto_start BGP {
BGP_CFG->hold_time = 240;
BGP_CFG->connect_retry_time = 120;
BGP_CFG->initial_hold_time = 240;
- BGP_CFG->default_med = ~0; /* RFC 1771 doesn't specify this, draft-09 says ~0 */
+ BGP_CFG->default_med = 0;
BGP_CFG->compare_path_lengths = 1;
BGP_CFG->start_delay_time = 5;
BGP_CFG->error_amnesia_time = 300;