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Better handling of AS4 optional attribute errors

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AS4 optional attribute errors were handled by session
drop (according to BGP RFC). This patch implements
error handling according to new BGP AS4 draft (*)
 - ignoring invalid AS4 optional attributes.

(*) http://www.ietf.org/internet-drafts/draft-chen-rfc4893bis-02.txt
This commit is contained in:
Ondrej Zajicek 2009-03-18 20:30:21 +01:00
parent eb875dbbe1
commit 48d79d521c
3 changed files with 95 additions and 17 deletions
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2
nest/attrs.h
View File

@ -13,6 +13,8 @@
#define AS_PATH_SET 1 /* Types of path segments */
#define AS_PATH_SEQUENCE 2
#define AS_PATH_CONFED_SEQUENCE 3
#define AS_PATH_CONFED_SET 4
#define AS_PATH_MAXLEN 10000

108
proto/bgp/attrs.c
View File

@ -76,16 +76,6 @@ 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)
{
@ -196,8 +186,8 @@ static struct attr_desc bgp_attr_table[] = {
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 },
{ "as4_aggregator", -1, BAF_OPTIONAL | BAF_TRANSITIVE, EAF_TYPE_OPAQUE, 1, /* BA_AS4_PATH */
NULL, NULL }
};
@ -1063,6 +1053,85 @@ bgp_merge_as_paths(struct adata *old2, struct adata *old4, int req_as, struct li
return newa;
}
static int
as4_aggregator_valid(struct adata *aggr)
{
if (aggr->length != 8)
return 0;
u32 *a = (u32 *) aggr->data;
if ((a[0] == 0) || (a[1] == 0))
return 0;
}
static int
as4_path_sanitize_and_get_length(struct adata *path)
{
int res = 0;
u8 *p, *dst;
int len, plen, copy;
dst = p = path->data;
len = path->length;
while (len)
{
if (len <= 2) /* We do not allow empty segments */
goto inconsistent_path;
switch (p[0])
{
case AS_PATH_SET:
plen = 2 + 4 * p[1];
copy = 1;
res++;
break;
case AS_PATH_SEQUENCE:
plen = 2 + 4 * p[1];
copy = 1;
res += p[1];
break;
case AS_PATH_CONFED_SEQUENCE:
case AS_PATH_CONFED_SET:
log(L_WARN "BGP: AS4_PATH attribute contains AS_CONFED_* segment, skipping segment");
plen = 2 + 4 * p[1];
copy = 0;
break;
default:
goto unknown_segment;
}
if (len < plen)
goto inconsistent_path;
if (copy)
{
if (dst != p)
memmove(dst, p, plen);
dst += plen;
}
len -= plen;
p += plen;
}
path->length = dst - path->data;
return res;
inconsistent_path:
log(L_WARN "BGP: AS4_PATH attribute is inconsistent, skipping attribute");
return -1;
unknown_segment:
log(L_WARN "BGP: AS4_PATH attribute contains unknown segment, skipping attribute");
return -1;
}
/* Reconstruct 4B AS_PATH and AGGREGATOR according to RFC 4893 4.2.3 */
static void
@ -1072,6 +1141,14 @@ bgp_reconstruct_4b_atts(struct bgp_proto *p, rta *a, struct linpool *pool)
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));
int a4_removed = 0;
if (a4 && !as4_aggregator_valid(a4->u.ptr))
{
log(L_WARN "BGP: AS4_AGGREGATOR attribute is invalid, skipping attribute");
a4 = NULL;
a4_removed = 1;
}
if (a2)
{
@ -1103,7 +1180,7 @@ bgp_reconstruct_4b_atts(struct bgp_proto *p, rta *a, struct linpool *pool)
/* Common case, use old AGGREGATOR attribute */
a2->u.ptr = bgp_aggregator_convert_to_new(a2->u.ptr, pool);
if (a2_as == AS_TRANS)
if ((a2_as == AS_TRANS) && !a4_removed)
log(L_WARN "BGP: AGGREGATOR attribute contain AS_TRANS, but AS4_AGGREGATOR is missing");
}
}
@ -1112,13 +1189,12 @@ bgp_reconstruct_4b_atts(struct bgp_proto *p, rta *a, struct linpool *pool)
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;
int p4_len = p4 ? as4_path_sanitize_and_get_length(p4->u.ptr) : -1;
if (p2_len < p4_len)
if ((p4_len <= 0) || (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

2
proto/bgp/bgp.c
View File

@ -53,7 +53,7 @@
* Unknown transitive attributes are attached to the route as %EAF_TYPE_OPAQUE byte streams.
*/
#define LOCAL_DEBUG
#undef LOCAL_DEBUG
#include "nest/bird.h"
#include "nest/iface.h"