Fixes some problems in BGP error handling.
This commit is contained in:
Ondrej Zajicek
parent
83696b3913
commit
06fb60c4af
2 changed files with 156 additions and 84 deletions
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@ -22,6 +22,42 @@
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#include "bgp.h"
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/*
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* UPDATE message error handling
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*
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* All checks from RFC 4271 6.3 are done as specified with these exceptions:
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* - The semantic check of an IP address from NEXT_HOP attribute is missing.
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* - Checks of some optional attribute values are missing.
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* - Syntactic and semantic checks of NLRIs (done in DECODE_PREFIX())
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* are probably inadequate.
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*
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* Loop detection based on AS_PATH causes updates to be withdrawn. RFC
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* 4271 does not explicitly specifiy the behavior in that case.
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*
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* Loop detection related to route reflection (based on ORIGINATOR_ID
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* and CLUSTER_LIST) causes updates to be withdrawn. RFC 4456 8
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* specifies that such updates should be ignored, but that is generally
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* a bad idea.
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*
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* Error checking of optional transitive attributes is done according to
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* draft-ietf-idr-optional-transitive-03, but errors are handled always
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* as withdraws.
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*
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* Unexpected AS_CONFED_* segments in AS_PATH are logged and removed,
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* but unknown segments cause a session drop with Malformed AS_PATH
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* error (see validate_path()). The behavior in such case is not
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* explicitly specified by RFC 4271. RFC 5065 specifies that
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* inconsistent AS_CONFED_* segments should cause a session drop, but
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* implementations that pass invalid AS_CONFED_* segments are
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* widespread.
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*
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* Error handling of AS4_* attributes is done as specified by
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* draft-ietf-idr-rfc4893bis-03. There are several possible
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* inconsistencies between AGGREGATOR and AS4_AGGREGATOR that are not
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* handled by that draft, these are logged and ignored (see
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* bgp_reconstruct_4b_attrs()).
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*/
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static byte bgp_mandatory_attrs[] = { BA_ORIGIN, BA_AS_PATH
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#ifndef IPV6
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,BA_NEXT_HOP
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@ -38,6 +74,9 @@ struct attr_desc {
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void (*format)(eattr *ea, byte *buf, int buflen);
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};
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#define IGNORE -1
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#define WITHDRAW -2
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static int
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bgp_check_origin(struct bgp_proto *p UNUSED, byte *a, int len UNUSED)
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{
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@ -152,7 +191,7 @@ static int
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bgp_check_next_hop(struct bgp_proto *p UNUSED, byte *a, int len)
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{
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#ifdef IPV6
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return -1;
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return IGNORE;
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#else
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ip_addr addr;
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@ -186,7 +225,7 @@ bgp_check_aggregator(struct bgp_proto *p, byte *a UNUSED, int len)
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{
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int exp_len = p->as4_session ? 8 : 6;
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return (len == exp_len) ? 0 : 5;
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return (len == exp_len) ? 0 : WITHDRAW;
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}
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static void
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@ -202,6 +241,13 @@ bgp_format_aggregator(eattr *a, byte *buf, int buflen UNUSED)
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bsprintf(buf, "%d.%d.%d.%d AS%d", data[0], data[1], data[2], data[3], as);
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}
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static int
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bgp_check_community(struct bgp_proto *p UNUSED, byte *a UNUSED, int len)
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{
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return ((len % 4) == 0) ? 0 : WITHDRAW;
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}
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static int
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bgp_check_cluster_list(struct bgp_proto *p UNUSED, byte *a UNUSED, int len)
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{
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@ -221,7 +267,7 @@ bgp_check_reach_nlri(struct bgp_proto *p UNUSED, byte *a UNUSED, int len UNUSED)
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p->mp_reach_start = a;
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p->mp_reach_len = len;
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#endif
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return -1;
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return IGNORE;
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}
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static int
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@ -231,7 +277,7 @@ bgp_check_unreach_nlri(struct bgp_proto *p UNUSED, byte *a UNUSED, int len UNUSE
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p->mp_unreach_start = a;
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p->mp_unreach_len = len;
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#endif
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return -1;
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return IGNORE;
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}
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static struct attr_desc bgp_attr_table[] = {
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@ -252,7 +298,7 @@ static struct attr_desc bgp_attr_table[] = {
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{ "aggregator", -1, BAF_OPTIONAL | BAF_TRANSITIVE, EAF_TYPE_OPAQUE, 1, /* BA_AGGREGATOR */
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bgp_check_aggregator, bgp_format_aggregator },
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{ "community", -1, BAF_OPTIONAL | BAF_TRANSITIVE, EAF_TYPE_INT_SET, 1, /* BA_COMMUNITY */
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NULL, NULL },
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bgp_check_community, NULL },
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{ "originator_id", 4, BAF_OPTIONAL, EAF_TYPE_ROUTER_ID, 0, /* BA_ORIGINATOR_ID */
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NULL, NULL },
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{ "cluster_list", -1, BAF_OPTIONAL, EAF_TYPE_INT_SET, 0, /* BA_CLUSTER_LIST */
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@ -1163,15 +1209,7 @@ bgp_merge_as_paths(struct adata *old2, struct adata *old4, int req_as, struct li
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static int
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as4_aggregator_valid(struct adata *aggr)
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{
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if (aggr->length != 8)
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return 0;
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u32 *a = (u32 *) aggr->data;
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if ((a[0] == 0) || (a[1] == 0))
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return 0;
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return 1;
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return aggr->length == 8;
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}
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@ -1258,7 +1296,7 @@ bgp_remove_as4_attrs(struct bgp_proto *p, rta *a)
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{
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*el = (*el)->next;
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if (p->as4_session)
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log(L_WARN "BGP: Unexpected AS4_* attributes received");
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log(L_WARN "%s: Unexpected AS4_* attributes received", p->p.name);
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}
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else
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el = &((*el)->next);
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@ -1288,6 +1326,7 @@ bgp_decode_attrs(struct bgp_conn *conn, byte *attr, unsigned int len, struct lin
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byte seen[256/8];
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ea_list *ea;
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struct adata *ad;
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int withdraw = 0;
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bzero(a, sizeof(rta));
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a->proto = &bgp->p;
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@ -1345,8 +1384,14 @@ bgp_decode_attrs(struct bgp_conn *conn, byte *attr, unsigned int len, struct lin
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errcode = desc->validate(bgp, z, l);
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if (errcode > 0)
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goto err;
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if (errcode < 0)
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if (errcode == IGNORE)
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continue;
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if (errcode <= WITHDRAW)
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{
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log(L_WARN "%s: Attribute %s is malformed, withdrawing update",
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bgp->p.name, desc->name);
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withdraw = 1;
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}
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}
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else if (code == BA_AS_PATH)
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{
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@ -1407,6 +1452,9 @@ bgp_decode_attrs(struct bgp_conn *conn, byte *attr, unsigned int len, struct lin
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}
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}
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if (withdraw)
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goto withdraw;
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#ifdef IPV6
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/* If we received MP_REACH_NLRI we should check mandatory attributes */
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if (bgp->mp_reach_len != 0)
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@ -1438,12 +1486,12 @@ bgp_decode_attrs(struct bgp_conn *conn, byte *attr, unsigned int len, struct lin
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/* If the AS path attribute contains our AS, reject the routes */
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if (bgp_as_path_loopy(bgp, a))
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goto loop;
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goto withdraw;
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/* Two checks for IBGP loops caused by route reflection, RFC 4456 */
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if (bgp_originator_id_loopy(bgp, a) ||
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bgp_cluster_list_loopy(bgp, a))
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goto loop;
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goto withdraw;
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/* If there's no local preference, define one */
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if (!(seen[0] & (1 << BA_LOCAL_PREF)))
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@ -1451,8 +1499,7 @@ bgp_decode_attrs(struct bgp_conn *conn, byte *attr, unsigned int len, struct lin
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return a;
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loop:
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DBG("BGP: Path loop!\n");
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withdraw:
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return NULL;
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malformed:
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@ -790,9 +790,9 @@ bgp_rx_open(struct bgp_conn *conn, byte *pkt, int len)
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int b = *pp++; \
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int q; \
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ll--; \
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if (b > BITS_PER_IP_ADDRESS) { err=10; goto bad; } \
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if (b > BITS_PER_IP_ADDRESS) { err=10; goto done; } \
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q = (b+7) / 8; \
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if (ll < q) { err=1; goto bad; } \
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if (ll < q) { err=1; goto done; } \
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memcpy(&prefix, pp, q); \
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pp += q; \
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ll -= q; \
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@ -840,11 +840,10 @@ bgp_do_rx_update(struct bgp_conn *conn,
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byte *attrs, int attr_len)
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{
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struct bgp_proto *p = conn->bgp;
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rta *a0;
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rta *a = NULL;
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ip_addr prefix;
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net *n;
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int err = 0, pxlen;
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rta *a0, *a = NULL;
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ip_addr prefix;
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int pxlen, err = 0;
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/* Withdraw routes */
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while (withdrawn_len)
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@ -859,32 +858,43 @@ bgp_do_rx_update(struct bgp_conn *conn,
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return;
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a0 = bgp_decode_attrs(conn, attrs, attr_len, bgp_linpool, nlri_len);
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if (a0 && nlri_len && bgp_set_next_hop(p, a0))
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{
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a = rta_lookup(a0);
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while (nlri_len)
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{
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rte *e;
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DECODE_PREFIX(nlri, nlri_len);
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DBG("Add %I/%d\n", prefix, pxlen);
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e = rte_get_temp(rta_clone(a));
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n = net_get(p->p.table, prefix, pxlen);
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e->net = n;
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e->pflags = 0;
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rte_update(p->p.table, n, &p->p, &p->p, e);
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if (bgp_apply_limits(p) < 0)
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goto bad2;
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}
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rta_free(a);
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}
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if (conn->state != BS_ESTABLISHED) /* fatal error during decoding */
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return;
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bad:
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bgp_error(conn, 3, err, NULL, 0);
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bad2:
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if (a0 && bgp_set_next_hop(p, a0))
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a = rta_lookup(a0);
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while (nlri_len)
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{
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DECODE_PREFIX(nlri, nlri_len);
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DBG("Add %I/%d\n", prefix, pxlen);
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if (a)
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{
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rte *e = rte_get_temp(rta_clone(a));
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e->net = net_get(p->p.table, prefix, pxlen);
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e->pflags = 0;
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rte_update(p->p.table, e->net, &p->p, &p->p, e);
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}
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else
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{
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/* Forced withdraw as a result of soft error */
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if (n = net_find(p->p.table, prefix, pxlen))
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rte_update(p->p.table, n, &p->p, &p->p, NULL);
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}
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if (bgp_apply_limits(p) < 0)
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goto done;
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}
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done:
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if (a)
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rta_free(a);
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if (err)
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bgp_error(conn, 3, err, NULL, 0);
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return;
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}
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@ -895,7 +905,7 @@ bgp_do_rx_update(struct bgp_conn *conn,
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len = len0 = p->name##_len; \
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if (len) \
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{ \
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if (len < 3) goto bad; \
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if (len < 3) { err=9; goto done; } \
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af = get_u16(x); \
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sub = x[2]; \
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x += 3; \
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@ -906,6 +916,24 @@ bgp_do_rx_update(struct bgp_conn *conn,
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af = 0; \
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if (af == BGP_AF_IPV6)
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static void
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bgp_attach_next_hop(rta *a0, byte *x)
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{
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ip_addr *nh = (ip_addr *) bgp_attach_attr_wa(&a0->eattrs, bgp_linpool, BA_NEXT_HOP, NEXT_HOP_LENGTH);
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memcpy(nh, x+1, 16);
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ipa_ntoh(nh[0]);
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/* We store received link local address in the other part of BA_NEXT_HOP eattr. */
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if (*x == 32)
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{
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memcpy(nh+1, x+17, 16);
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ipa_ntoh(nh[1]);
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}
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else
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nh[1] = IPA_NONE;
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}
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static void
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bgp_do_rx_update(struct bgp_conn *conn,
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byte *withdrawn, int withdrawn_len,
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@ -916,16 +944,16 @@ bgp_do_rx_update(struct bgp_conn *conn,
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byte *start, *x;
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int len, len0;
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unsigned af, sub;
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rta *a0;
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rta *a = NULL;
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ip_addr prefix;
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net *n;
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int err = 0, pxlen;
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rta *a0, *a = NULL;
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ip_addr prefix;
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int pxlen, err = 0;
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p->mp_reach_len = 0;
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p->mp_unreach_len = 0;
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a0 = bgp_decode_attrs(conn, attrs, attr_len, bgp_linpool, 0);
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if (!a0)
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if (conn->state != BS_ESTABLISHED) /* fatal error during decoding */
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return;
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DO_NLRI(mp_unreach)
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@ -943,52 +971,49 @@ bgp_do_rx_update(struct bgp_conn *conn,
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{
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/* Create fake NEXT_HOP attribute */
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if (len < 1 || (*x != 16 && *x != 32) || len < *x + 2)
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goto bad;
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{ err = 9; goto done; }
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ip_addr *nh = (ip_addr *) bgp_attach_attr_wa(&a0->eattrs, bgp_linpool, BA_NEXT_HOP, NEXT_HOP_LENGTH);
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memcpy(nh, x+1, 16);
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ipa_ntoh(nh[0]);
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/* We store received link local address in the other part of BA_NEXT_HOP eattr. */
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if (*x == 32)
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{
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memcpy(nh+1, x+17, 16);
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ipa_ntoh(nh[1]);
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}
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else
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nh[1] = IPA_NONE;
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if (a0)
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bgp_attach_next_hop(a0, x);
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/* Also ignore one reserved byte */
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len -= *x + 2;
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x += *x + 2;
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if (bgp_set_next_hop(p, a0))
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{
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if (a0 && bgp_set_next_hop(p, a0))
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a = rta_lookup(a0);
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while (len)
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{
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rte *e;
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DECODE_PREFIX(x, len);
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DBG("Add %I/%d\n", prefix, pxlen);
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e = rte_get_temp(rta_clone(a));
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n = net_get(p->p.table, prefix, pxlen);
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e->net = n;
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if (a)
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{
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rte *e = rte_get_temp(rta_clone(a));
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e->net = net_get(p->p.table, prefix, pxlen);
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e->pflags = 0;
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rte_update(p->p.table, n, &p->p, &p->p, e);
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rte_update(p->p.table, e->net, &p->p, &p->p, e);
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}
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else
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{
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/* Forced withdraw as a result of soft error */
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if (n = net_find(p->p.table, prefix, pxlen))
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rte_update(p->p.table, n, &p->p, &p->p, NULL);
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}
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if (bgp_apply_limits(p) < 0)
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goto bad2;
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}
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rta_free(a);
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goto done;
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}
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}
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return;
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bad:
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bgp_error(conn, 3, 9, start, len0);
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bad2:
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done:
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if (a)
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rta_free(a);
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if (err) /* Use subcode 9, not err */
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bgp_error(conn, 3, 9, NULL, 0);
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return;
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}
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