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bird/proto/bgp/attrs.c
Ondrej Zajicek (work) 62e64905b7 Several minor fixes
2017-02-20 02:26:45 +01:00

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/*
* BIRD -- BGP Attributes
*
* (c) 2000 Martin Mares <mj@ucw.cz>
* (c) 2008--2016 Ondrej Zajicek <santiago@crfreenet.org>
* (c) 2008--2016 CZ.NIC z.s.p.o.
*
* Can be freely distributed and used under the terms of the GNU GPL.
*/
#undef LOCAL_DEBUG
#include <stdlib.h>
#include "nest/bird.h"
#include "nest/iface.h"
#include "nest/protocol.h"
#include "nest/route.h"
#include "nest/attrs.h"
#include "conf/conf.h"
#include "lib/resource.h"
#include "lib/string.h"
#include "lib/unaligned.h"
#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* Loop detection based on AS_PATH causes updates to be withdrawn.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* and CLUSTER_LIST) causes updates to be withdrawn.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()).
*
* BGP attribute table has several hooks:
*
* export - Hook that validates and normalizes attribute during export phase.
* Receives eattr, may modify it (e.g., sort community lists for canonical
* representation), UNSET() it (e.g., skip empty lists), or WITHDRAW() it if
* necessary. May assume that eattr has value valid w.r.t. its type, but may be
* invalid w.r.t. BGP constraints. Optional.
*
* encode - Hook that converts internal representation to external one during
* packet writing. Receives eattr and puts it in the buffer (including attribute
* header). Returns number of bytes, or -1 if not enough space. May assume that
* eattr has value valid w.r.t. its type and validated by export hook. Mandatory
* for all known attributes that exist internally after export phase (i.e., all
* except pseudoattributes MP_(UN)REACH_NLRI).
*
* decode - Hook that converts external representation to internal one during
* packet parsing. Receives attribute data in buffer, validates it and adds
* attribute to ea_list. If data are invalid, steps DISCARD(), WITHDRAW() or
* bgp_parse_error() may be used to escape. Mandatory for all known attributes.
*
* format - Optional hook that converts eattr to textual representation.
*/
// XXXX review pool usage : c->c.proto->pool
struct bgp_attr_desc {
const char *name;
uint type;
uint flags;
void (*export)(struct bgp_export_state *s, eattr *a);
int (*encode)(struct bgp_write_state *s, eattr *a, byte *buf, uint size);
void (*decode)(struct bgp_parse_state *s, uint code, uint flags, byte *data, uint len, ea_list **to);
void (*format)(eattr *ea, byte *buf, uint size);
};
static const struct bgp_attr_desc bgp_attr_table[];
static inline int bgp_attr_known(uint code);
eattr *
bgp_set_attr(ea_list **attrs, struct linpool *pool, uint code, uint flags, uintptr_t val)
{
ASSERT(bgp_attr_known(code));
ea_list *a = lp_alloc(pool, sizeof(ea_list) + sizeof(eattr));
eattr *e = &a->attrs[0];
a->flags = EALF_SORTED;
a->count = 1;
a->next = *attrs;
*attrs = a;
e->id = EA_CODE(EAP_BGP, code);
e->type = bgp_attr_table[code].type;
e->flags = flags;
if (e->type & EAF_EMBEDDED)
e->u.data = (u32) val;
else
e->u.ptr = (struct adata *) val;
return e;
}
#define REPORT(msg, args...) \
({ log(L_REMOTE "%s: " msg, s->proto->p.name, ## args); })
#define DISCARD(msg, args...) \
({ REPORT(msg, ## args); return; })
#define WITHDRAW(msg, args...) \
({ REPORT(msg, ## args); s->err_withdraw = 1; return; })
#define UNSET(a) \
({ a->type = EAF_TYPE_UNDEF; return; })
#define NEW_BGP "Discarding %s attribute received from AS4-aware neighbor"
#define BAD_EBGP "Discarding %s attribute received from EBGP neighbor"
#define BAD_LENGTH "Malformed %s attribute - invalid length (%u)"
#define BAD_VALUE "Malformed %s attribute - invalid value (%u)"
#define NO_MANDATORY "Missing mandatory %s attribute"
static inline int
bgp_put_attr_hdr3(byte *buf, uint code, uint flags, uint len)
{
*buf++ = flags;
*buf++ = code;
*buf++ = len;
return 3;
}
static inline int
bgp_put_attr_hdr4(byte *buf, uint code, uint flags, uint len)
{
*buf++ = flags | BAF_EXT_LEN;
*buf++ = code;
put_u16(buf, len);
return 4;
}
static inline int
bgp_put_attr_hdr(byte *buf, uint code, uint flags, uint len)
{
if (len < 256)
return bgp_put_attr_hdr3(buf, code, flags, len);
else
return bgp_put_attr_hdr4(buf, code, flags, len);
}
static int
bgp_encode_u8(struct bgp_write_state *s UNUSED, eattr *a, byte *buf, uint size)
{
if (size < (3+1))
return -1;
bgp_put_attr_hdr3(buf, EA_ID(a->id), a->flags, 1);
buf[3] = a->u.data;
return 3+1;
}
static int
bgp_encode_u32(struct bgp_write_state *s UNUSED, eattr *a, byte *buf, uint size)
{
if (size < (3+4))
return -1;
bgp_put_attr_hdr3(buf, EA_ID(a->id), a->flags, 4);
put_u32(buf+3, a->u.data);
return 3+4;
}
static int
bgp_encode_u32s(struct bgp_write_state *s UNUSED, eattr *a, byte *buf, uint size)
{
uint len = a->u.ptr->length;
if (size < (4+len))
return -1;
uint hdr = bgp_put_attr_hdr(buf, EA_ID(a->id), a->flags, len);
put_u32s(buf + hdr, (u32 *) a->u.ptr->data, len / 4);
return hdr + len;
}
static int
bgp_put_attr(byte *buf, uint size, uint code, uint flags, byte *data, uint len)
{
if (size < (4+len))
return -1;
uint hdr = bgp_put_attr_hdr(buf, code, flags, len);
memcpy(buf + hdr, data, len);
return hdr + len;
}
static int
bgp_encode_raw(struct bgp_write_state *s UNUSED, eattr *a, byte *buf, uint size)
{
return bgp_put_attr(buf, size, EA_ID(a->id), a->flags, a->u.ptr->data, a->u.ptr->length);
}
/*
* Attribute hooks
*/
static void
bgp_export_origin(struct bgp_export_state *s, eattr *a)
{
if (a->u.data > 2)
WITHDRAW(BAD_VALUE, "ORIGIN", a->u.data);
}
static void
bgp_decode_origin(struct bgp_parse_state *s, uint code UNUSED, uint flags, byte *data, uint len, ea_list **to)
{
if (len != 1)
WITHDRAW(BAD_LENGTH, "ORIGIN", len);
if (data[0] > 2)
WITHDRAW(BAD_VALUE, "ORIGIN", data[0]);
bgp_set_attr_u32(to, s->pool, BA_ORIGIN, flags, data[0]);
}
static void
bgp_format_origin(eattr *a, byte *buf, uint size UNUSED)
{
static const char *bgp_origin_names[] = { "IGP", "EGP", "Incomplete" };
bsprintf(buf, (a->u.data <= 2) ? bgp_origin_names[a->u.data] : "?");
}
static int
bgp_encode_as_path(struct bgp_write_state *s, eattr *a, byte *buf, uint size)
{
byte *data = a->u.ptr->data;
uint len = a->u.ptr->length;
if (!s->as4_session)
{
/* Prepare 16-bit AS_PATH (from 32-bit one) in a temporary buffer */
byte *src = data;
data = alloca(len);
len = as_path_32to16(data, src, len);
}
return bgp_put_attr(buf, size, BA_AS_PATH, a->flags, data, len);
}
static void
bgp_decode_as_path(struct bgp_parse_state *s, uint code UNUSED, uint flags, byte *data, uint len, ea_list **to)
{
char err[128];
if (!as_path_valid(data, len, (s->as4_session ? 4 : 2), err, sizeof(err)))
WITHDRAW("Malformed AS_PATH attribute - %s", err);
if (!s->as4_session)
{
/* Prepare 32-bit AS_PATH (from 16-bit one) in a temporary buffer */
byte *src = data;
data = alloca(2*len);
len = as_path_16to32(data, src, len);
}
bgp_set_attr_data(to, s->pool, BA_AS_PATH, flags, data, len);
}
static int
bgp_encode_next_hop(struct bgp_write_state *s, eattr *a, byte *buf, uint size)
{
/*
* The NEXT_HOP attribute is used only in traditional (IPv4) BGP. In MP-BGP,
* the next hop is encoded as a part of the MP_REACH_NLRI attribute, so we
* store it and encode it later by AFI-specific hooks.
*/
if (s->channel->afi == BGP_AF_IPV4)
{
ASSERT(a->u.ptr->length == sizeof(ip_addr));
if (size < (3+4))
return -1;
bgp_put_attr_hdr3(buf, BA_NEXT_HOP, a->flags, 4);
put_ip4(buf+3, ipa_to_ip4( *(ip_addr *) a->u.ptr->data ));
return 3+4;
}
else
{
s->mp_next_hop = a;
return 0;
}
}
static void
bgp_decode_next_hop(struct bgp_parse_state *s, uint code UNUSED, uint flags UNUSED, byte *data, uint len, ea_list **to UNUSED)
{
if (len != 4)
WITHDRAW(BAD_LENGTH, "NEXT_HOP", len);
/* Semantic checks are done later */
s->ip_next_hop_len = len;
s->ip_next_hop_data = data;
}
/* TODO: This function should use AF-specific hook */
static void
bgp_format_next_hop(eattr *a, byte *buf, uint size UNUSED)
{
ip_addr *nh = (void *) a->u.ptr->data;
uint len = a->u.ptr->length;
ASSERT((len == 16) || (len == 32));
/* in IPv6, we may have two addresses in NEXT HOP */
if ((len == 16) || ipa_zero(nh[1]))
bsprintf(buf, "%I", nh[0]);
else
bsprintf(buf, "%I %I", nh[0], nh[1]);
}
static void
bgp_decode_med(struct bgp_parse_state *s, uint code UNUSED, uint flags, byte *data, uint len, ea_list **to)
{
if (len != 4)
WITHDRAW(BAD_LENGTH, "MULTI_EXIT_DISC", len);
u32 val = get_u32(data);
bgp_set_attr_u32(to, s->pool, BA_MULTI_EXIT_DISC, flags, val);
}
static void
bgp_export_local_pref(struct bgp_export_state *s, eattr *a)
{
if (!s->proto->is_interior)
UNSET(a);
}
static void
bgp_decode_local_pref(struct bgp_parse_state *s, uint code UNUSED, uint flags, byte *data, uint len, ea_list **to)
{
if (!s->proto->is_interior)
DISCARD(BAD_EBGP, "LOCAL_PREF");
if (len != 4)
WITHDRAW(BAD_LENGTH, "LOCAL_PREF", len);
u32 val = get_u32(data);
bgp_set_attr_u32(to, s->pool, BA_LOCAL_PREF, flags, val);
}
static void
bgp_decode_atomic_aggr(struct bgp_parse_state *s, uint code UNUSED, uint flags, byte *data UNUSED, uint len, ea_list **to)
{
if (len != 0)
DISCARD(BAD_LENGTH, "ATOMIC_AGGR", len);
bgp_set_attr_data(to, s->pool, BA_ATOMIC_AGGR, flags, NULL, 0);
}
static int
bgp_encode_aggregator(struct bgp_write_state *s, eattr *a, byte *buf, uint size)
{
byte *data = a->u.ptr->data;
uint len = a->u.ptr->length;
if (!s->as4_session)
{
/* Prepare 16-bit AGGREGATOR (from 32-bit one) in a temporary buffer */
byte *src = data;
data = alloca(6);
len = aggregator_32to16(data, src);
}
return bgp_put_attr(buf, size, BA_AGGREGATOR, a->flags, data, len);
}
static void
bgp_decode_aggregator(struct bgp_parse_state *s, uint code UNUSED, uint flags, byte *data, uint len, ea_list **to)
{
if (len != (s->as4_session ? 8 : 6))
DISCARD(BAD_LENGTH, "AGGREGATOR", len);
if (!s->as4_session)
{
/* Prepare 32-bit AGGREGATOR (from 16-bit one) in a temporary buffer */
byte *src = data;
data = alloca(8);
len = aggregator_16to32(data, src);
}
bgp_set_attr_data(to, s->pool, BA_AGGREGATOR, flags, data, len);
}
static void
bgp_format_aggregator(eattr *a, byte *buf, uint size UNUSED)
{
byte *data = a->u.ptr->data;
bsprintf(buf, "%I4 AS%u", get_ip4(data+4), get_u32(data+0));
}
static void
bgp_export_community(struct bgp_export_state *s, eattr *a)
{
if (a->u.ptr->length == 0)
UNSET(a);
a->u.ptr = int_set_sort(s->pool, a->u.ptr);
}
static void
bgp_decode_community(struct bgp_parse_state *s, uint code UNUSED, uint flags, byte *data, uint len, ea_list **to)
{
if (!len || (len % 4))
WITHDRAW(BAD_LENGTH, "COMMUNITY", len);
struct adata *ad = lp_alloc_adata(s->pool, len);
get_u32s(data, (u32 *) ad->data, len / 4);
bgp_set_attr_ptr(to, s->pool, BA_COMMUNITY, flags, ad);
}
static void
bgp_export_originator_id(struct bgp_export_state *s, eattr *a)
{
if (!s->proto->is_internal)
UNSET(a);
}
static void
bgp_decode_originator_id(struct bgp_parse_state *s, uint code UNUSED, uint flags, byte *data, uint len, ea_list **to)
{
if (!s->proto->is_internal)
DISCARD(BAD_EBGP, "ORIGINATOR_ID");
if (len != 4)
WITHDRAW(BAD_LENGTH, "ORIGINATOR_ID", len);
u32 val = get_u32(data);
bgp_set_attr_u32(to, s->pool, BA_ORIGINATOR_ID, flags, val);
}
static void
bgp_export_cluster_list(struct bgp_export_state *s UNUSED, eattr *a)
{
if (!s->proto->is_internal)
UNSET(a);
if (a->u.ptr->length == 0)
UNSET(a);
}
static void
bgp_decode_cluster_list(struct bgp_parse_state *s, uint code UNUSED, uint flags, byte *data, uint len, ea_list **to)
{
if (!s->proto->is_internal)
DISCARD(BAD_EBGP, "CLUSTER_LIST");
if (!len || (len % 4))
WITHDRAW(BAD_LENGTH, "CLUSTER_LIST", len);
struct adata *ad = lp_alloc_adata(s->pool, len);
get_u32s(data, (u32 *) ad->data, len / 4);
bgp_set_attr_ptr(to, s->pool, BA_CLUSTER_LIST, flags, ad);
}
static void
bgp_format_cluster_list(eattr *a, byte *buf, uint size)
{
/* Truncates cluster lists larger than buflen, probably not a problem */
int_set_format(a->u.ptr, 0, -1, buf, size);
}
static inline u32
get_af3(byte *buf)
{
return (get_u16(buf) << 16) | buf[2];
}
static void
bgp_decode_mp_reach_nlri(struct bgp_parse_state *s, uint code UNUSED, uint flags UNUSED, byte *data, uint len, ea_list **to UNUSED)
{
/*
* 2 B MP_REACH_NLRI data - Address Family Identifier
* 1 B MP_REACH_NLRI data - Subsequent Address Family Identifier
* 1 B MP_REACH_NLRI data - Length of Next Hop Network Address
* var MP_REACH_NLRI data - Network Address of Next Hop
* 1 B MP_REACH_NLRI data - Reserved (zero)
* var MP_REACH_NLRI data - Network Layer Reachability Information
*/
if ((len < 5) || (len < (5 + (uint) data[3])))
bgp_parse_error(s, 9);
s->mp_reach_af = get_af3(data);
s->mp_next_hop_len = data[3];
s->mp_next_hop_data = data + 4;
s->mp_reach_len = len - 5 - s->mp_next_hop_len;
s->mp_reach_nlri = data + 5 + s->mp_next_hop_len;
}
static void
bgp_decode_mp_unreach_nlri(struct bgp_parse_state *s, uint code UNUSED, uint flags UNUSED, byte *data, uint len, ea_list **to UNUSED)
{
/*
* 2 B MP_UNREACH_NLRI data - Address Family Identifier
* 1 B MP_UNREACH_NLRI data - Subsequent Address Family Identifier
* var MP_UNREACH_NLRI data - Network Layer Reachability Information
*/
if (len < 3)
bgp_parse_error(s, 9);
s->mp_unreach_af = get_af3(data);
s->mp_unreach_len = len - 3;
s->mp_unreach_nlri = data + 3;
}
static void
bgp_export_ext_community(struct bgp_export_state *s, eattr *a)
{
if (a->u.ptr->length == 0)
UNSET(a);
a->u.ptr = ec_set_sort(s->pool, a->u.ptr);
}
static void
bgp_decode_ext_community(struct bgp_parse_state *s, uint code UNUSED, uint flags, byte *data, uint len, ea_list **to)
{
if (!len || (len % 8))
WITHDRAW(BAD_LENGTH, "EXT_COMMUNITY", len);
struct adata *ad = lp_alloc_adata(s->pool, len);
get_u32s(data, (u32 *) ad->data, len / 4);
bgp_set_attr_ptr(to, s->pool, BA_EXT_COMMUNITY, flags, ad);
}
static void
bgp_decode_as4_aggregator(struct bgp_parse_state *s, uint code UNUSED, uint flags, byte *data, uint len, ea_list **to)
{
if (s->as4_session)
DISCARD(NEW_BGP, "AS4_AGGREGATOR");
if (len != 8)
DISCARD(BAD_LENGTH, "AS4_AGGREGATOR", len);
bgp_set_attr_data(to, s->pool, BA_AS4_AGGREGATOR, flags, data, len);
}
static void
bgp_decode_as4_path(struct bgp_parse_state *s, uint code UNUSED, uint flags, byte *data, uint len, ea_list **to)
{
char err[128];
if (s->as4_session)
DISCARD(NEW_BGP, "AS4_PATH");
if (len < 6)
DISCARD(BAD_LENGTH, "AS4_PATH", len);
if (!as_path_valid(data, len, 4, err, sizeof(err)))
DISCARD("Malformed AS4_PATH attribute - %s", err);
/* XXXX remove CONFED segments */
bgp_set_attr_data(to, s->pool, BA_AS4_PATH, flags, data, len);
}
static void
bgp_export_large_community(struct bgp_export_state *s, eattr *a)
{
if (a->u.ptr->length == 0)
UNSET(a);
a->u.ptr = lc_set_sort(s->pool, a->u.ptr);
}
static void
bgp_decode_large_community(struct bgp_parse_state *s, uint code UNUSED, uint flags, byte *data, uint len, ea_list **to)
{
if (!len || (len % 12))
WITHDRAW(BAD_LENGTH, "LARGE_COMMUNITY", len);
struct adata *ad = lp_alloc_adata(s->pool, len);
get_u32s(data, (u32 *) ad->data, len / 4);
bgp_set_attr_ptr(to, s->pool, BA_LARGE_COMMUNITY, flags, ad);
}
static inline void
bgp_decode_unknown(struct bgp_parse_state *s, uint code, uint flags, byte *data, uint len, ea_list **to)
{
bgp_set_attr_data(to, s->pool, code, flags, data, len);
}
/*
* Attribute table
*/
static const struct bgp_attr_desc bgp_attr_table[] = {
[BA_ORIGIN] = {
.name = "origin",
.type = EAF_TYPE_INT,
.flags = BAF_TRANSITIVE,
.export = bgp_export_origin,
.encode = bgp_encode_u8,
.decode = bgp_decode_origin,
.format = bgp_format_origin,
},
[BA_AS_PATH] = {
.name = "as_path",
.type = EAF_TYPE_AS_PATH,
.flags = BAF_TRANSITIVE,
.encode = bgp_encode_as_path,
.decode = bgp_decode_as_path,
},
[BA_NEXT_HOP] = {
.name = "next_hop",
.type = EAF_TYPE_IP_ADDRESS,
.flags = BAF_TRANSITIVE,
.encode = bgp_encode_next_hop,
.decode = bgp_decode_next_hop,
.format = bgp_format_next_hop,
},
[BA_MULTI_EXIT_DISC] = {
.name = "med",
.type = EAF_TYPE_INT,
.flags = BAF_OPTIONAL,
.encode = bgp_encode_u32,
.decode = bgp_decode_med,
},
[BA_LOCAL_PREF] = {
.name = "local_pref",
.type = EAF_TYPE_INT,
.flags = BAF_TRANSITIVE,
.export = bgp_export_local_pref,
.encode = bgp_encode_u32,
.decode = bgp_decode_local_pref,
},
[BA_ATOMIC_AGGR] = {
.name = "atomic_aggr",
.type = EAF_TYPE_OPAQUE,
.flags = BAF_TRANSITIVE,
.encode = bgp_encode_raw,
.decode = bgp_decode_atomic_aggr,
},
[BA_AGGREGATOR] = {
.name = "aggregator",
.type = EAF_TYPE_OPAQUE,
.flags = BAF_OPTIONAL | BAF_TRANSITIVE,
.encode = bgp_encode_aggregator,
.decode = bgp_decode_aggregator,
.format = bgp_format_aggregator,
},
[BA_COMMUNITY] = {
.name = "community",
.type = EAF_TYPE_INT_SET,
.flags = BAF_OPTIONAL | BAF_TRANSITIVE,
.export = bgp_export_community,
.encode = bgp_encode_u32s,
.decode = bgp_decode_community,
},
[BA_ORIGINATOR_ID] = {
.name = "originator_id",
.type = EAF_TYPE_ROUTER_ID,
.flags = BAF_OPTIONAL,
.export = bgp_export_originator_id,
.encode = bgp_encode_u32,
.decode = bgp_decode_originator_id,
},
[BA_CLUSTER_LIST] = {
.name = "cluster_list",
.type = EAF_TYPE_INT_SET,
.flags = BAF_OPTIONAL,
.export = bgp_export_cluster_list,
.encode = bgp_encode_u32s,
.decode = bgp_decode_cluster_list,
.format = bgp_format_cluster_list,
},
[BA_MP_REACH_NLRI] = {
.name = "mp_reach_nlri",
.type = EAF_TYPE_OPAQUE,
.flags = BAF_OPTIONAL,
.decode = bgp_decode_mp_reach_nlri,
},
[BA_MP_UNREACH_NLRI] = {
.name = "mp_unreach_nlri",
.type = EAF_TYPE_OPAQUE,
.flags = BAF_OPTIONAL,
.decode = bgp_decode_mp_unreach_nlri,
},
[BA_EXT_COMMUNITY] = {
.name = "ext_community",
.type = EAF_TYPE_EC_SET,
.flags = BAF_OPTIONAL | BAF_TRANSITIVE,
.export = bgp_export_ext_community,
.encode = bgp_encode_u32s,
.decode = bgp_decode_ext_community,
},
[BA_AS4_PATH] = {
.name = "as4_path",
.type = EAF_TYPE_AS_PATH,
.flags = BAF_OPTIONAL | BAF_TRANSITIVE,
.encode = bgp_encode_raw,
.decode = bgp_decode_as4_path,
},
[BA_AS4_AGGREGATOR] = {
.name = "as4_aggregator",
.type = EAF_TYPE_OPAQUE,
.flags = BAF_OPTIONAL | BAF_TRANSITIVE,
.encode = bgp_encode_raw,
.decode = bgp_decode_as4_aggregator,
.format = bgp_format_aggregator,
},
[BA_LARGE_COMMUNITY] = {
.name = "large_community",
.type = EAF_TYPE_LC_SET,
.flags = BAF_OPTIONAL | BAF_TRANSITIVE,
.export = bgp_export_large_community,
.encode = bgp_encode_u32s,
.decode = bgp_decode_large_community,
},
};
static inline int
bgp_attr_known(uint code)
{
return (code < ARRAY_SIZE(bgp_attr_table)) && bgp_attr_table[code].name;
}
/*
* Attribute export
*/
static inline void
bgp_export_attr(struct bgp_export_state *s, eattr *a, ea_list *to)
{
if (EA_PROTO(a->id) != EAP_BGP)
return;
uint code = EA_ID(a->id);
if (bgp_attr_known(code))
{
const struct bgp_attr_desc *desc = &bgp_attr_table[code];
/* The flags might have been zero if the attr was added by filters */
a->flags = (a->flags & BAF_PARTIAL) | desc->flags;
/* Set partial bit if new opt-trans attribute is attached to non-local route */
if ((s->src != NULL) && (a->type & EAF_ORIGINATED) &&
(a->flags & BAF_OPTIONAL) && (a->flags & BAF_TRANSITIVE))
a->flags |= BAF_PARTIAL;
/* Call specific hook */
CALL(desc->export, s, a);
/* Attribute might become undefined in hook */
if ((a->type & EAF_TYPE_MASK) == EAF_TYPE_UNDEF)
return;
}
else
{
/* Don't re-export unknown non-transitive attributes */
if (!(a->flags & BAF_TRANSITIVE))
return;
a->flags |= BAF_PARTIAL;
}
/* Append updated attribute */
to->attrs[to->count++] = *a;
}
/**
* bgp_export_attrs - export BGP attributes
* @s: BGP export state
* @attrs: a list of extended attributes
*
* The bgp_export_attrs() function takes a list of attributes and merges it to
* one newly allocated and sorted segment. Attributes are validated and
* normalized by type-specific export hooks and attribute flags are updated.
* Some attributes may be eliminated (e.g. unknown non-tranitive attributes, or
* empty community sets).
*
* Result: one sorted attribute list segment, or NULL if attributes are unsuitable.
*/
static inline ea_list *
bgp_export_attrs(struct bgp_export_state *s, ea_list *attrs)
{
/* Merge the attribute list */
ea_list *new = lp_alloc(s->pool, ea_scan(attrs));
ea_merge(attrs, new);
ea_sort(new);
uint i, count;
count = new->count;
new->count = 0;
/* Export each attribute */
for (i = 0; i < count; i++)
bgp_export_attr(s, &new->attrs[i], new);
if (s->err_withdraw)
return NULL;
return new;
}
/*
* Attribute encoding
*/
static inline int
bgp_encode_attr(struct bgp_write_state *s, eattr *a, byte *buf, uint size)
{
ASSERT(EA_PROTO(a->id) == EAP_BGP);
uint code = EA_ID(a->id);
if (bgp_attr_known(code))
return bgp_attr_table[code].encode(s, a, buf, size);
else
return bgp_encode_raw(s, a, buf, size);
}
/**
* bgp_encode_attrs - encode BGP attributes
* @s: BGP write state
* @attrs: a list of extended attributes
* @buf: buffer
* @end: buffer end
*
* The bgp_encode_attrs() function takes a list of extended attributes
* and converts it to its BGP representation (a part of an Update message).
*
* Result: Length of the attribute block generated or -1 if not enough space.
*/
int
bgp_encode_attrs(struct bgp_write_state *s, ea_list *attrs, byte *buf, byte *end)
{
byte *pos = buf;
int i, len;
for (i = 0; i < attrs->count; i++)
{
len = bgp_encode_attr(s, &attrs->attrs[i], pos, end - pos);
if (len < 0)
return -1;
pos += len;
}
return pos - buf;
}
/*
* Attribute decoding
*/
static void bgp_process_as4_attrs(ea_list **attrs, struct linpool *pool);
static inline int
bgp_as_path_loopy(struct bgp_proto *p, ea_list *attrs, u32 asn)
{
eattr *e = bgp_find_attr(attrs, BA_AS_PATH);
int num = p->cf->allow_local_as + 1;
return (e && (num > 0) && as_path_contains(e->u.ptr, asn, num));
}
static inline int
bgp_originator_id_loopy(struct bgp_proto *p, ea_list *attrs)
{
eattr *e = bgp_find_attr(attrs, BA_ORIGINATOR_ID);
return (e && (e->u.data == p->local_id));
}
static inline int
bgp_cluster_list_loopy(struct bgp_proto *p, ea_list *attrs)
{
eattr *e = bgp_find_attr(attrs, BA_CLUSTER_LIST);
return (e && int_set_contains(e->u.ptr, p->rr_cluster_id));
}
static inline void
bgp_decode_attr(struct bgp_parse_state *s, uint code, uint flags, byte *data, uint len, ea_list **to)
{
/* Handle duplicate attributes; RFC 7606 3 (g) */
if (BIT32_TEST(s->attrs_seen, code))
{
if ((code == BA_MP_REACH_NLRI) || (code == BA_MP_UNREACH_NLRI))
bgp_parse_error(s, 1);
else
DISCARD("Discarding duplicate attribute (code %u)", code);
}
BIT32_SET(s->attrs_seen, code);
if (bgp_attr_known(code))
{
const struct bgp_attr_desc *desc = &bgp_attr_table[code];
/* Handle conflicting flags; RFC 7606 3 (c) */
if ((flags ^ desc->flags) & (BAF_OPTIONAL | BAF_TRANSITIVE))
WITHDRAW("Malformed %s attribute - conflicting flags (%02x)", desc->name, flags);
desc->decode(s, code, flags, data, len, to);
}
else /* Unknown attribute */
{
if (!(flags & BAF_OPTIONAL))
WITHDRAW("Unknown attribute (code %u) - conflicting flags (%02x)", code, flags);
bgp_decode_unknown(s, code, flags, data, len, to);
}
}
/**
* bgp_decode_attrs - check and decode BGP attributes
* @s: BGP parse state
* @data: start of attribute block
* @len: length of attribute block
*
* This function takes a BGP attribute block (a part of an Update message), checks
* its consistency and converts it to a list of BIRD route attributes represented
* by an (uncached) &rta.
*/
ea_list *
bgp_decode_attrs(struct bgp_parse_state *s, byte *data, uint len)
{
struct bgp_proto *p = s->proto;
ea_list *attrs = NULL;
uint code, flags, alen;
byte *pos = data;
/* Parse the attributes */
while (len)
{
alen = 0;
/* Read attribute type */
if (len < 2)
goto framing_error;
flags = pos[0];
code = pos[1];
ADVANCE(pos, len, 2);
/* Read attribute length */
if (flags & BAF_EXT_LEN)
{
if (len < 2)
goto framing_error;
alen = get_u16(pos);
ADVANCE(pos, len, 2);
}
else
{
if (len < 1)
goto framing_error;
alen = *pos;
ADVANCE(pos, len, 1);
}
if (alen > len)
goto framing_error;
DBG("Attr %02x %02x %u\n", code, flags, alen);
bgp_decode_attr(s, code, flags, pos, alen, &attrs);
ADVANCE(pos, len, alen);
}
if (s->err_withdraw)
goto withdraw;
/* If there is no reachability NLRI, we are finished */
if (!s->ip_reach_len && !s->mp_reach_len)
return NULL;
/* Handle missing mandatory attributes; RFC 7606 3 (d) */
if (!BIT32_TEST(s->attrs_seen, BA_ORIGIN))
{ REPORT(NO_MANDATORY, "ORIGIN"); goto withdraw; }
if (!BIT32_TEST(s->attrs_seen, BA_AS_PATH))
{ REPORT(NO_MANDATORY, "AS_PATH"); goto withdraw; }
/* When receiving attributes from non-AS4-aware BGP speaker, we have to
reconstruct AS_PATH and AGGREGATOR attributes; RFC 6793 4.2.3 */
if (!p->as4_session)
bgp_process_as4_attrs(&attrs, s->pool);
/* Reject routes with our ASN in AS_PATH attribute */
if (bgp_as_path_loopy(p, attrs, p->local_as))
goto withdraw;
/* Reject routes with our Confederation ID in AS_PATH attribute; RFC 5065 4 */
if ((p->public_as != p->local_as) && bgp_as_path_loopy(p, attrs, p->public_as))
goto withdraw;
/* Reject routes with our Router ID in ORIGINATOR_ID attribute; RFC 4456 8 */
if (p->is_internal && bgp_originator_id_loopy(p, attrs))
goto withdraw;
/* Reject routes with our Cluster ID in CLUSTER_LIST attribute; RFC 4456 8 */
if (p->rr_client && bgp_cluster_list_loopy(p, attrs))
goto withdraw;
/* If there is no local preference, define one */
if (!BIT32_TEST(s->attrs_seen, BA_LOCAL_PREF))
bgp_set_attr_u32(&attrs, s->pool, BA_LOCAL_PREF, 0, p->cf->default_local_pref);
return attrs;
framing_error:
/* RFC 7606 4 - handle attribute framing errors */
REPORT("Malformed attribute list - framing error (%u/%u) at %d",
alen, len, (int) (pos - s->attrs));
withdraw:
/* RFC 7606 5.2 - handle missing NLRI during errors */
if (!s->ip_reach_len && !s->mp_reach_len)
bgp_parse_error(s, 1);
s->err_withdraw = 1;
return NULL;
}
/*
* Route bucket hash table
*/
#define RBH_KEY(b) b->eattrs, b->hash
#define RBH_NEXT(b) b->next
#define RBH_EQ(a1,h1,a2,h2) h1 == h2 && ea_same(a1, a2)
#define RBH_FN(a,h) h
#define RBH_REHASH bgp_rbh_rehash
#define RBH_PARAMS /8, *2, 2, 2, 8, 20
HASH_DEFINE_REHASH_FN(RBH, struct bgp_bucket)
void
bgp_init_bucket_table(struct bgp_channel *c)
{
HASH_INIT(c->bucket_hash, c->pool, 8);
init_list(&c->bucket_queue);
c->withdraw_bucket = NULL;
}
static struct bgp_bucket *
bgp_get_bucket(struct bgp_channel *c, ea_list *new)
{
/* Hash and lookup */
u32 hash = ea_hash(new);
struct bgp_bucket *b = HASH_FIND(c->bucket_hash, RBH, new, hash);
if (b)
return b;
uint ea_size = sizeof(ea_list) + new->count * sizeof(eattr);
uint ea_size_aligned = BIRD_ALIGN(ea_size, CPU_STRUCT_ALIGN);
uint size = sizeof(struct bgp_bucket) + ea_size_aligned;
uint i;
byte *dest;
/* Gather total size of non-inline attributes */
for (i = 0; i < new->count; i++)
{
eattr *a = &new->attrs[i];
if (!(a->type & EAF_EMBEDDED))
size += BIRD_ALIGN(sizeof(struct adata) + a->u.ptr->length, CPU_STRUCT_ALIGN);
}
/* Create the bucket */
b = mb_alloc(c->pool, size);
init_list(&b->prefixes);
b->hash = hash;
/* Copy list of extended attributes */
memcpy(b->eattrs, new, ea_size);
dest = ((byte *) b->eattrs) + ea_size_aligned;
/* Copy values of non-inline attributes */
for (i = 0; i < new->count; i++)
{
eattr *a = &b->eattrs->attrs[i];
if (!(a->type & EAF_EMBEDDED))
{
struct adata *oa = a->u.ptr;
struct adata *na = (struct adata *) dest;
memcpy(na, oa, sizeof(struct adata) + oa->length);
a->u.ptr = na;
dest += BIRD_ALIGN(sizeof(struct adata) + na->length, CPU_STRUCT_ALIGN);
}
}
/* Insert the bucket to send queue and bucket hash */
add_tail(&c->bucket_queue, &b->send_node);
HASH_INSERT2(c->bucket_hash, RBH, c->pool, b);
return b;
}
static struct bgp_bucket *
bgp_get_withdraw_bucket(struct bgp_channel *c)
{
if (!c->withdraw_bucket)
{
c->withdraw_bucket = mb_allocz(c->pool, sizeof(struct bgp_bucket));
init_list(&c->withdraw_bucket->prefixes);
}
return c->withdraw_bucket;
}
void
bgp_free_bucket(struct bgp_channel *c, struct bgp_bucket *b)
{
rem_node(&b->send_node);
HASH_REMOVE2(c->bucket_hash, RBH, c->pool, b);
mb_free(b);
}
void
bgp_defer_bucket(struct bgp_channel *c, struct bgp_bucket *b)
{
rem_node(&b->send_node);
add_tail(&c->bucket_queue, &b->send_node);
}
void
bgp_withdraw_bucket(struct bgp_channel *c, struct bgp_bucket *b)
{
struct bgp_proto *p = (void *) c->c.proto;
struct bgp_bucket *wb = bgp_get_withdraw_bucket(c);
log(L_ERR "%s: Attribute list too long", p->p.name);
while (!EMPTY_LIST(b->prefixes))
{
struct bgp_prefix *px = HEAD(b->prefixes);
log(L_ERR "%s: - withdrawing %N", p->p.name, &px->net);
rem_node(&px->buck_node);
add_tail(&wb->prefixes, &px->buck_node);
}
}
/*
* Prefix hash table
*/
#define PXH_KEY(px) px->net, px->path_id, px->hash
#define PXH_NEXT(px) px->next
#define PXH_EQ(n1,i1,h1,n2,i2,h2) h1 == h2 && i1 == i2 && net_equal(n1, n2)
#define PXH_FN(n,i,h) h
#define PXH_REHASH bgp_pxh_rehash
#define PXH_PARAMS /8, *2, 2, 2, 8, 20
HASH_DEFINE_REHASH_FN(PXH, struct bgp_prefix)
void
bgp_init_prefix_table(struct bgp_channel *c)
{
HASH_INIT(c->prefix_hash, c->pool, 8);
c->prefix_slab = sl_new(c->pool, sizeof(struct bgp_prefix) +
net_addr_length[c->c.net_type]);
}
static struct bgp_prefix *
bgp_get_prefix(struct bgp_channel *c, net_addr *net, u32 path_id)
{
u32 hash = net_hash(net) ^ u32_hash(path_id);
struct bgp_prefix *px = HASH_FIND(c->prefix_hash, PXH, net, path_id, hash);
if (px)
{
rem_node(&px->buck_node);
return px;
}
px = sl_alloc(c->prefix_slab);
px->buck_node.next = NULL;
px->buck_node.prev = NULL;
px->hash = hash;
px->path_id = path_id;
net_copy(px->net, net);
HASH_INSERT2(c->prefix_hash, PXH, c->pool, px);
return px;
}
void
bgp_free_prefix(struct bgp_channel *c, struct bgp_prefix *px)
{
rem_node(&px->buck_node);
HASH_REMOVE2(c->prefix_hash, PXH, c->pool, px);
sl_free(c->prefix_slab, px);
}
/*
* BGP protocol glue
*/
int
bgp_import_control(struct proto *P, rte **new, ea_list **attrs UNUSED, struct linpool *pool UNUSED)
{
rte *e = *new;
struct proto *SRC = e->attrs->src->proto;
struct bgp_proto *p = (struct bgp_proto *) P;
struct bgp_proto *src = (SRC->proto == &proto_bgp) ? (struct bgp_proto *) SRC : NULL;
/* Reject our routes */
if (src == p)
return -1;
/* Accept non-BGP routes */
if (src == NULL)
return 0;
/* IBGP route reflection, RFC 4456 */
if (p->is_internal && src->is_internal && (p->local_as == src->local_as))
{
/* Rejected unless configured as route reflector */
if (!p->rr_client && !src->rr_client)
return -1;
/* Generally, this should be handled when path is received, but we check it
also here as rr_cluster_id may be undefined or different in src. */
if (p->rr_cluster_id && bgp_cluster_list_loopy(p, e->attrs->eattrs))
return -1;
}
/* Handle well-known communities, RFC 1997 */
struct eattr *c;
if (p->cf->interpret_communities &&
(c = ea_find(e->attrs->eattrs, EA_CODE(EAP_BGP, BA_COMMUNITY))))
{
struct adata *d = c->u.ptr;
/* Do not export anywhere */
if (int_set_contains(d, BGP_COMM_NO_ADVERTISE))
return -1;
/* Do not export outside of AS (or member-AS) */
if (!p->is_internal && int_set_contains(d, BGP_COMM_NO_EXPORT_SUBCONFED))
return -1;
/* Do not export outside of AS (or confederation) */
if (!p->is_interior && int_set_contains(d, BGP_COMM_NO_EXPORT))
return -1;
}
return 0;
}
static const adata null_adata; /* adata of length 0 */
static inline void
bgp_path_prepend(ea_list **attrs, struct linpool *pool, int seg, u32 as, int strip)
{
eattr *a = bgp_find_attr(*attrs, BA_AS_PATH);
adata *d = as_path_prepend2(pool, a ? a->u.ptr : &null_adata, seg, as, strip);
bgp_set_attr_ptr(attrs, pool, BA_AS_PATH, 0, d);
}
static inline void
bgp_cluster_list_prepend(ea_list **attrs, struct linpool *pool, u32 id)
{
eattr *a = bgp_find_attr(*attrs, BA_CLUSTER_LIST);
adata *d = int_set_add(pool, a ? a->u.ptr : NULL, id);
bgp_set_attr_ptr(attrs, pool, BA_CLUSTER_LIST, 0, d);
}
static ea_list *
bgp_update_attrs(struct bgp_proto *p, struct bgp_channel *c, rte *e, ea_list *attrs, struct linpool *pool)
{
struct proto *SRC = e->attrs->src->proto;
struct bgp_proto *src = (SRC->proto == &proto_bgp) ? (void *) SRC : NULL;
struct bgp_export_state s = { .proto = p, .channel =c, .pool = pool, .src = src, .route = e };
eattr *a;
/* ORIGIN attribute - mandatory, attach if missing */
if (! bgp_find_attr(attrs, BA_ORIGIN))
bgp_set_attr_u32(&attrs, pool, BA_ORIGIN, 0, src ? ORIGIN_INCOMPLETE : ORIGIN_IGP);
/* AS_PATH attribute - keep or prepend ASN */
if (p->is_internal ||
(p->rs_client && src && src->rs_client))
{
/* IBGP or route server -> just ensure there is one */
if (! bgp_find_attr(attrs, BA_AS_PATH))
bgp_set_attr_ptr(&attrs, pool, BA_AS_PATH, 0, lp_alloc_adata(pool, 0));
}
else if (p->is_interior)
{
/* Confederation -> prepend ASN as CONFED_SEQUENCE, keep CONFED_* segments */
bgp_path_prepend(&attrs, pool, AS_PATH_CONFED_SEQUENCE, p->public_as, 0);
}
else /* Regular EBGP (no RS, no confederation) */
{
/* Regular EBGP -> prepend ASN as regular segment, strip CONFED_* segments */
bgp_path_prepend(&attrs, pool, AS_PATH_SEQUENCE, p->public_as, 1);
/* MULTI_EXIT_DESC attribute - accept only if set in export filter */
a = bgp_find_attr(attrs, BA_MULTI_EXIT_DISC);
if (a && !(a->type & EAF_FRESH))
bgp_unset_attr(&attrs, pool, BA_MULTI_EXIT_DISC);
}
/* NEXT_HOP attribute - delegated to AF-specific hook */
a = bgp_find_attr(attrs, BA_NEXT_HOP);
bgp_update_next_hop(&s, a, &attrs);
/* LOCAL_PREF attribute - required for IBGP, attach if missing */
if (p->is_interior && ! bgp_find_attr(attrs, BA_LOCAL_PREF))
bgp_set_attr_u32(&attrs, pool, BA_LOCAL_PREF, 0, p->cf->default_local_pref);
/* IBGP route reflection, RFC 4456 */
if (src && src->is_internal && p->is_internal && (src->local_as == p->local_as))
{
/* ORIGINATOR_ID attribute - attach if not already set */
if (! bgp_find_attr(attrs, BA_ORIGINATOR_ID))
bgp_set_attr_u32(&attrs, pool, BA_ORIGINATOR_ID, 0, src->remote_id);
/* CLUSTER_LIST attribute - prepend cluster ID */
if (src->rr_cluster_id)
bgp_cluster_list_prepend(&attrs, pool, src->rr_cluster_id);
/* Handle different src and dst cluster ID - prepend both ones */
if (p->rr_cluster_id && (src->rr_cluster_id != p->rr_cluster_id))
bgp_cluster_list_prepend(&attrs, pool, p->rr_cluster_id);
}
/* AS4_* transition attributes, RFC 6793 4.2.2 */
if (! p->as4_session)
{
a = bgp_find_attr(attrs, BA_AS_PATH);
if (a && as_path_contains_as4(a->u.ptr))
{
bgp_set_attr_ptr(&attrs, pool, BA_AS_PATH, 0, as_path_to_old(pool, a->u.ptr));
bgp_set_attr_ptr(&attrs, pool, BA_AS4_PATH, 0, as_path_strip_confed(pool, a->u.ptr));
}
a = bgp_find_attr(attrs, BA_AGGREGATOR);
if (a && aggregator_contains_as4(a->u.ptr))
{
bgp_set_attr_ptr(&attrs, pool, BA_AGGREGATOR, 0, aggregator_to_old(pool, a->u.ptr));
bgp_set_attr_ptr(&attrs, pool, BA_AS4_AGGREGATOR, 0, a->u.ptr);
}
}
/* Apply per-attribute export hooks for validatation and normalization */
return bgp_export_attrs(&s, attrs);
}
void
bgp_rt_notify(struct proto *P, struct channel *C, net *n, rte *new, rte *old, ea_list *attrs)
{
struct bgp_proto *p = (void *) P;
struct bgp_channel *c = (void *) C;
struct bgp_bucket *buck;
struct bgp_prefix *px;
u32 path;
if (new)
{
attrs = bgp_update_attrs(p, c, new, attrs, bgp_linpool);
/* If attributes are invalid, we fail back to withdraw */
buck = attrs ? bgp_get_bucket(c, attrs) : bgp_get_withdraw_bucket(c);
path = new->attrs->src->global_id;
lp_flush(bgp_linpool);
}
else
{
buck = bgp_get_withdraw_bucket(c);
path = old->attrs->src->global_id;
}
px = bgp_get_prefix(c, n->n.addr, c->add_path_tx ? path : 0);
add_tail(&buck->prefixes, &px->buck_node);
bgp_schedule_packet(p->conn, c, PKT_UPDATE);
}
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_first(e->u.ptr, &as))
return as;
else
return ((struct bgp_proto *) r->attrs->src->proto)->remote_as;
}
static inline int
rte_resolvable(rte *rt)
{
return rt->attrs->dest == RTD_UNICAST;
}
int
bgp_rte_better(rte *new, rte *old)
{
struct bgp_proto *new_bgp = (struct bgp_proto *) new->attrs->src->proto;
struct bgp_proto *old_bgp = (struct bgp_proto *) old->attrs->src->proto;
eattr *x, *y;
u32 n, o;
/* Skip suppressed routes (see bgp_rte_recalculate()) */
n = new->u.bgp.suppressed;
o = old->u.bgp.suppressed;
if (n > o)
return 0;
if (n < o)
return 1;
/* RFC 4271 9.1.2.1. Route resolvability test */
n = rte_resolvable(new);
o = rte_resolvable(old);
if (n > o)
return 1;
if (n < o)
return 0;
/* Start with local preferences */
x = ea_find(new->attrs->eattrs, EA_CODE(EAP_BGP, BA_LOCAL_PREF));
y = ea_find(old->attrs->eattrs, EA_CODE(EAP_BGP, BA_LOCAL_PREF));
n = x ? x->u.data : new_bgp->cf->default_local_pref;
o = y ? y->u.data : old_bgp->cf->default_local_pref;
if (n > o)
return 1;
if (n < o)
return 0;
/* RFC 4271 9.1.2.2. a) Use AS path lengths */
if (new_bgp->cf->compare_path_lengths || old_bgp->cf->compare_path_lengths)
{
x = ea_find(new->attrs->eattrs, EA_CODE(EAP_BGP, BA_AS_PATH));
y = ea_find(old->attrs->eattrs, EA_CODE(EAP_BGP, BA_AS_PATH));
n = x ? as_path_getlen(x->u.ptr) : AS_PATH_MAXLEN;
o = y ? as_path_getlen(y->u.ptr) : AS_PATH_MAXLEN;
if (n < o)
return 1;
if (n > o)
return 0;
}
/* RFC 4271 9.1.2.2. b) Use origins */
x = ea_find(new->attrs->eattrs, EA_CODE(EAP_BGP, BA_ORIGIN));
y = ea_find(old->attrs->eattrs, EA_CODE(EAP_BGP, BA_ORIGIN));
n = x ? x->u.data : ORIGIN_INCOMPLETE;
o = y ? y->u.data : ORIGIN_INCOMPLETE;
if (n < o)
return 1;
if (n > o)
return 0;
/* RFC 4271 9.1.2.2. c) Compare MED's */
/* Proper RFC 4271 path selection cannot be interpreted as finding
* the best path in some ordering. It is implemented partially in
* bgp_rte_recalculate() when deterministic_med option is
* active. Without that option, the behavior is just an
* approximation, which in specific situations may lead to
* persistent routing loops, because it is nondeterministic - it
* depends on the order in which routes appeared. But it is also the
* same behavior as used by default in Cisco routers, so it is
* probably not a big issue.
*/
if (new_bgp->cf->med_metric || old_bgp->cf->med_metric ||
(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_interior > old_bgp->is_interior)
return 0;
if (new_bgp->is_interior < old_bgp->is_interior)
return 1;
/* RFC 4271 9.1.2.2. e) Compare IGP metrics */
n = new_bgp->cf->igp_metric ? new->attrs->igp_metric : 0;
o = old_bgp->cf->igp_metric ? old->attrs->igp_metric : 0;
if (n < o)
return 1;
if (n > o)
return 0;
/* RFC 4271 9.1.2.2. f) Compare BGP identifiers */
/* RFC 4456 9. a) Use ORIGINATOR_ID instead of local neighbor ID */
x = ea_find(new->attrs->eattrs, EA_CODE(EAP_BGP, BA_ORIGINATOR_ID));
y = ea_find(old->attrs->eattrs, EA_CODE(EAP_BGP, BA_ORIGINATOR_ID));
n = x ? x->u.data : new_bgp->remote_id;
o = y ? y->u.data : old_bgp->remote_id;
/* RFC 5004 - prefer older routes */
/* (if both are external and from different peer) */
if ((new_bgp->cf->prefer_older || old_bgp->cf->prefer_older) &&
!new_bgp->is_internal && n != o)
return 0;
/* rest of RFC 4271 9.1.2.2. f) */
if (n < o)
return 1;
if (n > o)
return 0;
/* RFC 4456 9. b) Compare cluster list lengths */
x = ea_find(new->attrs->eattrs, EA_CODE(EAP_BGP, BA_CLUSTER_LIST));
y = ea_find(old->attrs->eattrs, EA_CODE(EAP_BGP, BA_CLUSTER_LIST));
n = x ? int_set_get_size(x->u.ptr) : 0;
o = y ? int_set_get_size(y->u.ptr) : 0;
if (n < o)
return 1;
if (n > o)
return 0;
/* RFC 4271 9.1.2.2. g) Compare peer IP adresses */
return (ipa_compare(new_bgp->cf->remote_ip, old_bgp->cf->remote_ip) < 0);
}
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)
{
return (r->pref == lpref) && (bgp_get_neighbor(r) == lasn);
}
static inline int
use_deterministic_med(rte *r)
{
struct proto *P = r->attrs->src->proto;
return (P->proto == &proto_bgp) && ((struct bgp_proto *) P)->cf->deterministic_med;
}
int
bgp_rte_recalculate(rtable *table, net *net, rte *new, rte *old, rte *old_best)
{
rte *r, *s;
rte *key = new ? new : old;
u32 lpref = key->pref;
u32 lasn = bgp_get_neighbor(key);
int old_is_group_best = 0;
/*
* Proper RFC 4271 path selection is a bit complicated, it cannot be
* implemented just by rte_better(), because it is not a linear
* ordering. But it can be splitted to two levels, where the lower
* level chooses the best routes in each group of routes from the
* same neighboring AS and higher level chooses the best route (with
* a slightly different ordering) between the best-in-group routes.
*
* When deterministic_med is disabled, we just ignore this issue and
* choose the best route by bgp_rte_better() alone. If enabled, the
* lower level of the route selection is done here (for the group
* to which the changed route belongs), all routes in group are
* marked as suppressed, just chosen best-in-group is not.
*
* Global best route selection then implements higher level by
* choosing between non-suppressed routes (as they are always
* preferred over suppressed routes). Routes from BGP protocols
* that do not set deterministic_med are just never suppressed. As
* they do not participate in the lower level selection, it is OK
* that this fn is not called for them.
*
* The idea is simple, the implementation is more problematic,
* mostly because of optimizations in rte_recalculate() that
* avoids full recalculation in most cases.
*
* We can assume that at least one of new, old is non-NULL and both
* are from the same protocol with enabled deterministic_med. We
* group routes by both neighbor AS (lasn) and preference (lpref),
* because bgp_rte_better() does not handle preference itself.
*/
/* If new and old are from different groups, we just process that
as two independent events */
if (new && old && !same_group(old, lpref, lasn))
{
int i1, i2;
i1 = bgp_rte_recalculate(table, net, NULL, old, old_best);
i2 = bgp_rte_recalculate(table, net, new, NULL, old_best);
return i1 || i2;
}
/*
* We could find the best-in-group and then make some shortcuts like
* in rte_recalculate, but as we would have to walk through all
* net->routes just to find it, it is probably not worth. So we
* just have two simpler fast cases that use just the old route.
* We also set suppressed flag to avoid using it in bgp_rte_better().
*/
if (new)
new->u.bgp.suppressed = 1;
if (old)
{
old_is_group_best = !old->u.bgp.suppressed;
old->u.bgp.suppressed = 1;
int new_is_better = new && bgp_rte_better(new, old);
/* The first case - replace not best with worse (or remove not best) */
if (!old_is_group_best && !new_is_better)
return 0;
/* The second case - replace the best with better */
if (old_is_group_best && new_is_better)
{
/* new is best-in-group, the see discussion below - this is
a special variant of NBG && OBG. From OBG we can deduce
that same_group(old_best) iff (old == old_best) */
new->u.bgp.suppressed = 0;
return (old == old_best);
}
}
/* The default case - find a new best-in-group route */
r = new; /* new may not be in the list */
for (s=net->routes; rte_is_valid(s); s=s->next)
if (use_deterministic_med(s) && same_group(s, lpref, lasn))
{
s->u.bgp.suppressed = 1;
if (!r || bgp_rte_better(s, r))
r = s;
}
/* Simple case - the last route in group disappears */
if (!r)
return 0;
/* Found best-in-group */
r->u.bgp.suppressed = 0;
/*
* There are generally two reasons why we have to force
* recalculation (return 1): First, the new route may be wrongfully
* chosen to be the best in the first case check in
* rte_recalculate(), this may happen only if old_best is from the
* same group. Second, another (different than new route)
* best-in-group is chosen and that may be the proper best (although
* rte_recalculate() without ignore that possibility).
*
* There are three possible cases according to whether the old route
* was the best in group (OBG, stored in old_is_group_best) and
* whether the new route is the best in group (NBG, tested by r == new).
* These cases work even if old or new is NULL.
*
* NBG -> new is a possible candidate for the best route, so we just
* check for the first reason using same_group().
*
* !NBG && OBG -> Second reason applies, return 1
*
* !NBG && !OBG -> Best in group does not change, old != old_best,
* rte_better(new, old_best) is false and therefore
* the first reason does not apply, return 0
*/
if (r == new)
return old_best && same_group(old_best, lpref, lasn);
else
return old_is_group_best;
}
/*
* Reconstruct AS_PATH and AGGREGATOR according to RFC 6793 4.2.3
*/
static void
bgp_process_as4_attrs(ea_list **attrs, struct linpool *pool)
{
eattr *p2 = bgp_find_attr(*attrs, BA_AS_PATH);
eattr *p4 = bgp_find_attr(*attrs, BA_AS4_PATH);
eattr *a2 = bgp_find_attr(*attrs, BA_AGGREGATOR);
eattr *a4 = bgp_find_attr(*attrs, BA_AS4_AGGREGATOR);
/* First, unset AS4_* attributes */
if (p4) bgp_unset_attr(attrs, pool, BA_AS4_PATH);
if (a4) bgp_unset_attr(attrs, pool, BA_AS4_AGGREGATOR);
/* Handle AGGREGATOR attribute */
if (a2 && a4)
{
u32 a2_asn = get_u32(a2->u.ptr->data);
/* If routes were aggregated by an old router, then AS4_PATH and
AS4_AGGREGATOR are invalid. In that case we give up. */
if (a2_asn != AS_TRANS)
return;
/* Use AS4_AGGREGATOR instead of AGGREGATOR */
a2->u.ptr = a4->u.ptr;
}
/* Handle AS_PATH attribute */
if (p2 && p4)
{
int p2_len = as_path_getlen(p2->u.ptr);
int p4_len = as_path_getlen(p4->u.ptr);
/* AS_PATH is too short, give up */
if (p2_len < p4_len)
return;
/* Merge AS_PATH and AS4_PATH */
as_path_cut(p2->u.ptr, p2_len - p4_len);
p2->u.ptr = as_path_merge(pool, p2->u.ptr, p4->u.ptr);
}
}
int
bgp_get_attr(eattr *a, byte *buf, int buflen)
{
uint i = EA_ID(a->id);
const struct bgp_attr_desc *d;
int len;
if (bgp_attr_known(i))
{
d = &bgp_attr_table[i];
len = bsprintf(buf, "%s", d->name);
buf += len;
if (d->format)
{
*buf++ = ':';
*buf++ = ' ';
d->format(a, buf, buflen - len - 2);
return GA_FULL;
}
return GA_NAME;
}
bsprintf(buf, "%02x%s", i, (a->flags & BAF_TRANSITIVE) ? " [t]" : "");
return GA_NAME;
}
void
bgp_get_route_info(rte *e, byte *buf, ea_list *attrs)
{
eattr *p = ea_find(attrs, EA_CODE(EAP_BGP, BA_AS_PATH));
eattr *o = ea_find(attrs, EA_CODE(EAP_BGP, BA_ORIGIN));
u32 origas;
buf += bsprintf(buf, " (%d", e->pref);
if (e->u.bgp.suppressed)
buf += bsprintf(buf, "-");
if (e->attrs->hostentry)
{
if (!rte_resolvable(e))
buf += bsprintf(buf, "/-");
else if (e->attrs->igp_metric >= IGP_METRIC_UNKNOWN)
buf += bsprintf(buf, "/?");
else
buf += bsprintf(buf, "/%d", e->attrs->igp_metric);
}
buf += bsprintf(buf, ") [");
if (p && as_path_get_last(p->u.ptr, &origas))
buf += bsprintf(buf, "AS%u", origas);
if (o)
buf += bsprintf(buf, "%c", "ie?"[o->u.data]);
strcpy(buf, "]");
}
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