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Fixes some problems in BGP error handling.

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This commit is contained in:
Ondrej Zajicek 2011-03-30 01:09:18 +02:00
parent 83696b3913
commit 06fb60c4af
2 changed files with 156 additions and 84 deletions
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93
proto/bgp/attrs.c
View File

@ -22,6 +22,42 @@
#include "bgp.h"
/*
* UPDATE message error handling
*
* All checks from RFC 4271 6.3 are done as specified with these exceptions:
* - The semantic check of an IP address from NEXT_HOP attribute is missing.
* - Checks of some optional attribute values are missing.
* - Syntactic and semantic checks of NLRIs (done in DECODE_PREFIX())
* are probably inadequate.
*
* Loop detection based on AS_PATH causes updates to be withdrawn. RFC
* 4271 does not explicitly specifiy the behavior in that case.
*
* Loop detection related to route reflection (based on ORIGINATOR_ID
* and CLUSTER_LIST) causes updates to be withdrawn. RFC 4456 8
* specifies that such updates should be ignored, but that is generally
* a bad idea.
*
* Error checking of optional transitive attributes is done according to
* draft-ietf-idr-optional-transitive-03, but errors are handled always
* as withdraws.
*
* Unexpected AS_CONFED_* segments in AS_PATH are logged and removed,
* but unknown segments cause a session drop with Malformed AS_PATH
* error (see validate_path()). The behavior in such case is not
* explicitly specified by RFC 4271. RFC 5065 specifies that
* inconsistent AS_CONFED_* segments should cause a session drop, but
* implementations that pass invalid AS_CONFED_* segments are
* widespread.
*
* Error handling of AS4_* attributes is done as specified by
* draft-ietf-idr-rfc4893bis-03. There are several possible
* inconsistencies between AGGREGATOR and AS4_AGGREGATOR that are not
* handled by that draft, these are logged and ignored (see
* bgp_reconstruct_4b_attrs()).
*/
static byte bgp_mandatory_attrs[] = { BA_ORIGIN, BA_AS_PATH
#ifndef IPV6
,BA_NEXT_HOP
@ -38,6 +74,9 @@ struct attr_desc {
void (*format)(eattr *ea, byte *buf, int buflen);
};
#define IGNORE -1
#define WITHDRAW -2
static int
bgp_check_origin(struct bgp_proto *p UNUSED, byte *a, int len UNUSED)
{
@ -152,7 +191,7 @@ static int
bgp_check_next_hop(struct bgp_proto *p UNUSED, byte *a, int len)
{
#ifdef IPV6
return -1;
return IGNORE;
#else
ip_addr addr;
@ -186,7 +225,7 @@ bgp_check_aggregator(struct bgp_proto *p, byte *a UNUSED, int len)
{
int exp_len = p->as4_session ? 8 : 6;
return (len == exp_len) ? 0 : 5;
return (len == exp_len) ? 0 : WITHDRAW;
}
static void
@ -202,6 +241,13 @@ bgp_format_aggregator(eattr *a, byte *buf, int buflen UNUSED)
bsprintf(buf, "%d.%d.%d.%d AS%d", data[0], data[1], data[2], data[3], as);
}
static int
bgp_check_community(struct bgp_proto *p UNUSED, byte *a UNUSED, int len)
{
return ((len % 4) == 0) ? 0 : WITHDRAW;
}
static int
bgp_check_cluster_list(struct bgp_proto *p UNUSED, byte *a UNUSED, int len)
{
@ -221,7 +267,7 @@ bgp_check_reach_nlri(struct bgp_proto *p UNUSED, byte *a UNUSED, int len UNUSED)
p->mp_reach_start = a;
p->mp_reach_len = len;
#endif
return -1;
return IGNORE;
}
static int
@ -231,7 +277,7 @@ bgp_check_unreach_nlri(struct bgp_proto *p UNUSED, byte *a UNUSED, int len UNUSE
p->mp_unreach_start = a;
p->mp_unreach_len = len;
#endif
return -1;
return IGNORE;
}
static struct attr_desc bgp_attr_table[] = {
@ -252,19 +298,19 @@ static struct attr_desc bgp_attr_table[] = {
{ "aggregator", -1, BAF_OPTIONAL | BAF_TRANSITIVE, EAF_TYPE_OPAQUE, 1, /* BA_AGGREGATOR */
bgp_check_aggregator, bgp_format_aggregator },
{ "community", -1, BAF_OPTIONAL | BAF_TRANSITIVE, EAF_TYPE_INT_SET, 1, /* BA_COMMUNITY */
NULL, NULL },
bgp_check_community, NULL },
{ "originator_id", 4, BAF_OPTIONAL, EAF_TYPE_ROUTER_ID, 0, /* BA_ORIGINATOR_ID */
NULL, NULL },
{ "cluster_list", -1, BAF_OPTIONAL, EAF_TYPE_INT_SET, 0, /* BA_CLUSTER_LIST */
bgp_check_cluster_list, bgp_format_cluster_list },
{ .name = NULL }, /* BA_DPA */
{ .name = NULL }, /* BA_ADVERTISER */
{ .name = NULL }, /* BA_RCID_PATH */
{ .name = NULL }, /* BA_ADVERTISER */
{ .name = NULL }, /* BA_RCID_PATH */
{ "mp_reach_nlri", -1, BAF_OPTIONAL, EAF_TYPE_OPAQUE, 1, /* BA_MP_REACH_NLRI */
bgp_check_reach_nlri, NULL },
{ "mp_unreach_nlri", -1, BAF_OPTIONAL, EAF_TYPE_OPAQUE, 1, /* BA_MP_UNREACH_NLRI */
bgp_check_unreach_nlri, NULL },
{ .name = NULL }, /* BA_EXTENDED_COMM */
{ .name = NULL }, /* BA_EXTENDED_COMM */
{ "as4_path", -1, 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 */
@ -1163,15 +1209,7 @@ bgp_merge_as_paths(struct adata *old2, struct adata *old4, int req_as, struct li
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;
return 1;
return aggr->length == 8;
}
@ -1258,7 +1296,7 @@ bgp_remove_as4_attrs(struct bgp_proto *p, rta *a)
{
*el = (*el)->next;
if (p->as4_session)
log(L_WARN "BGP: Unexpected AS4_* attributes received");
log(L_WARN "%s: Unexpected AS4_* attributes received", p->p.name);
}
else
el = &((*el)->next);
@ -1288,6 +1326,7 @@ bgp_decode_attrs(struct bgp_conn *conn, byte *attr, unsigned int len, struct lin
byte seen[256/8];
ea_list *ea;
struct adata *ad;
int withdraw = 0;
bzero(a, sizeof(rta));
a->proto = &bgp->p;
@ -1345,8 +1384,14 @@ bgp_decode_attrs(struct bgp_conn *conn, byte *attr, unsigned int len, struct lin
errcode = desc->validate(bgp, z, l);
if (errcode > 0)
goto err;
if (errcode < 0)
if (errcode == IGNORE)
continue;
if (errcode <= WITHDRAW)
{
log(L_WARN "%s: Attribute %s is malformed, withdrawing update",
bgp->p.name, desc->name);
withdraw = 1;
}
}
else if (code == BA_AS_PATH)
{
@ -1407,6 +1452,9 @@ bgp_decode_attrs(struct bgp_conn *conn, byte *attr, unsigned int len, struct lin
}
}
if (withdraw)
goto withdraw;
#ifdef IPV6
/* If we received MP_REACH_NLRI we should check mandatory attributes */
if (bgp->mp_reach_len != 0)
@ -1438,12 +1486,12 @@ bgp_decode_attrs(struct bgp_conn *conn, byte *attr, unsigned int len, struct lin
/* If the AS path attribute contains our AS, reject the routes */
if (bgp_as_path_loopy(bgp, a))
goto loop;
goto withdraw;
/* 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;
goto withdraw;
/* If there's no local preference, define one */
if (!(seen[0] & (1 << BA_LOCAL_PREF)))
@ -1451,8 +1499,7 @@ bgp_decode_attrs(struct bgp_conn *conn, byte *attr, unsigned int len, struct lin
return a;
loop:
DBG("BGP: Path loop!\n");
withdraw:
return NULL;
malformed:

147
proto/bgp/packets.c
View File

@ -790,9 +790,9 @@ bgp_rx_open(struct bgp_conn *conn, byte *pkt, int len)
int b = *pp++; \
int q; \
ll--; \
if (b > BITS_PER_IP_ADDRESS) { err=10; goto bad; } \
if (b > BITS_PER_IP_ADDRESS) { err=10; goto done; } \
q = (b+7) / 8; \
if (ll < q) { err=1; goto bad; } \
if (ll < q) { err=1; goto done; } \
memcpy(&prefix, pp, q); \
pp += q; \
ll -= q; \
@ -840,11 +840,10 @@ bgp_do_rx_update(struct bgp_conn *conn,
byte *attrs, int attr_len)
{
struct bgp_proto *p = conn->bgp;
rta *a0;
rta *a = NULL;
ip_addr prefix;
net *n;
int err = 0, pxlen;
rta *a0, *a = NULL;
ip_addr prefix;
int pxlen, err = 0;
/* Withdraw routes */
while (withdrawn_len)
@ -859,32 +858,43 @@ bgp_do_rx_update(struct bgp_conn *conn,
return;
a0 = bgp_decode_attrs(conn, attrs, attr_len, bgp_linpool, nlri_len);
if (a0 && nlri_len && bgp_set_next_hop(p, a0))
if (conn->state != BS_ESTABLISHED) /* fatal error during decoding */
return;
if (a0 && bgp_set_next_hop(p, a0))
a = rta_lookup(a0);
while (nlri_len)
{
a = rta_lookup(a0);
while (nlri_len)
DECODE_PREFIX(nlri, nlri_len);
DBG("Add %I/%d\n", prefix, pxlen);
if (a)
{
rte *e;
DECODE_PREFIX(nlri, nlri_len);
DBG("Add %I/%d\n", prefix, pxlen);
e = rte_get_temp(rta_clone(a));
n = net_get(p->p.table, prefix, pxlen);
e->net = n;
rte *e = rte_get_temp(rta_clone(a));
e->net = net_get(p->p.table, prefix, pxlen);
e->pflags = 0;
rte_update(p->p.table, n, &p->p, &p->p, e);
if (bgp_apply_limits(p) < 0)
goto bad2;
rte_update(p->p.table, e->net, &p->p, &p->p, e);
}
rta_free(a);
else
{
/* Forced withdraw as a result of soft error */
if (n = net_find(p->p.table, prefix, pxlen))
rte_update(p->p.table, n, &p->p, &p->p, NULL);
}
if (bgp_apply_limits(p) < 0)
goto done;
}
return;
bad:
bgp_error(conn, 3, err, NULL, 0);
bad2:
done:
if (a)
rta_free(a);
if (err)
bgp_error(conn, 3, err, NULL, 0);
return;
}
@ -895,7 +905,7 @@ bgp_do_rx_update(struct bgp_conn *conn,
len = len0 = p->name##_len; \
if (len) \
{ \
if (len < 3) goto bad; \
if (len < 3) { err=9; goto done; } \
af = get_u16(x); \
sub = x[2]; \
x += 3; \
@ -906,6 +916,24 @@ bgp_do_rx_update(struct bgp_conn *conn,
af = 0; \
if (af == BGP_AF_IPV6)
static void
bgp_attach_next_hop(rta *a0, byte *x)
{
ip_addr *nh = (ip_addr *) bgp_attach_attr_wa(&a0->eattrs, bgp_linpool, BA_NEXT_HOP, NEXT_HOP_LENGTH);
memcpy(nh, x+1, 16);
ipa_ntoh(nh[0]);
/* We store received link local address in the other part of BA_NEXT_HOP eattr. */
if (*x == 32)
{
memcpy(nh+1, x+17, 16);
ipa_ntoh(nh[1]);
}
else
nh[1] = IPA_NONE;
}
static void
bgp_do_rx_update(struct bgp_conn *conn,
byte *withdrawn, int withdrawn_len,
@ -916,16 +944,16 @@ bgp_do_rx_update(struct bgp_conn *conn,
byte *start, *x;
int len, len0;
unsigned af, sub;
rta *a0;
rta *a = NULL;
ip_addr prefix;
net *n;
int err = 0, pxlen;
rta *a0, *a = NULL;
ip_addr prefix;
int pxlen, err = 0;
p->mp_reach_len = 0;
p->mp_unreach_len = 0;
a0 = bgp_decode_attrs(conn, attrs, attr_len, bgp_linpool, 0);
if (!a0)
if (conn->state != BS_ESTABLISHED) /* fatal error during decoding */
return;
DO_NLRI(mp_unreach)
@ -943,52 +971,49 @@ bgp_do_rx_update(struct bgp_conn *conn,
{
/* Create fake NEXT_HOP attribute */
if (len < 1 || (*x != 16 && *x != 32) || len < *x + 2)
goto bad;
{ err = 9; goto done; }
ip_addr *nh = (ip_addr *) bgp_attach_attr_wa(&a0->eattrs, bgp_linpool, BA_NEXT_HOP, NEXT_HOP_LENGTH);
memcpy(nh, x+1, 16);
ipa_ntoh(nh[0]);
/* We store received link local address in the other part of BA_NEXT_HOP eattr. */
if (*x == 32)
{
memcpy(nh+1, x+17, 16);
ipa_ntoh(nh[1]);
}
else
nh[1] = IPA_NONE;
if (a0)
bgp_attach_next_hop(a0, x);
/* Also ignore one reserved byte */
len -= *x + 2;
x += *x + 2;
if (bgp_set_next_hop(p, a0))
if (a0 && bgp_set_next_hop(p, a0))
a = rta_lookup(a0);
while (len)
{
a = rta_lookup(a0);
while (len)
DECODE_PREFIX(x, len);
DBG("Add %I/%d\n", prefix, pxlen);
if (a)
{
rte *e;
DECODE_PREFIX(x, len);
DBG("Add %I/%d\n", prefix, pxlen);
e = rte_get_temp(rta_clone(a));
n = net_get(p->p.table, prefix, pxlen);
e->net = n;
rte *e = rte_get_temp(rta_clone(a));
e->net = net_get(p->p.table, prefix, pxlen);
e->pflags = 0;
rte_update(p->p.table, n, &p->p, &p->p, e);
if (bgp_apply_limits(p) < 0)
goto bad2;
rte_update(p->p.table, e->net, &p->p, &p->p, e);
}
rta_free(a);
else
{
/* Forced withdraw as a result of soft error */
if (n = net_find(p->p.table, prefix, pxlen))
rte_update(p->p.table, n, &p->p, &p->p, NULL);
}
if (bgp_apply_limits(p) < 0)
goto done;
}
}
return;
bad:
bgp_error(conn, 3, 9, start, len0);
bad2:
done:
if (a)
rta_free(a);
if (err) /* Use subcode 9, not err */
bgp_error(conn, 3, 9, NULL, 0);
return;
}