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bird/proto/bgp/attrs.c
Ondrej Zajicek (work) 261816b0d4 BGP: Cluster list item should be prepended 
Commit 3c09af41... changed behavior of int_set_add() from prepend to
append, which makes more sense for community list, but prepend must be
used for cluster list. Add int_set_prepend() and use it in cluster list
handling code.
2016-11-15 16:24:39 +01:00

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53 KiB
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/*
* BIRD -- BGP Attributes
*
* (c) 2000 Martin Mares <mj@ucw.cz>
*
* 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* Loop detection based on AS_PATH causes updates to be withdrawn.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* and CLUSTER_LIST) causes updates to be withdrawn.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()).
*/
static byte bgp_mandatory_attrs[] = { BA_ORIGIN, BA_AS_PATH
#ifndef IPV6
,BA_NEXT_HOP
#endif
};
struct attr_desc {
char *name;
int expected_length;
int expected_flags;
int type;
int allow_in_ebgp;
int (*validate)(struct bgp_proto *p, byte *attr, int len);
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)
{
if (*a > 2)
return 6;
return 0;
}
static void
bgp_format_origin(eattr *a, byte *buf, int buflen UNUSED)
{
static char *bgp_origin_names[] = { "IGP", "EGP", "Incomplete" };
bsprintf(buf, bgp_origin_names[a->u.data]);
}
static int
path_segment_contains(byte *p, int bs, u32 asn)
{
int i;
int len = p[1];
p += 2;
for(i=0; i<len; i++)
{
u32 asn2 = (bs == 4) ? get_u32(p) : get_u16(p);
if (asn2 == asn)
return 1;
p += bs;
}
return 0;
}
/* Validates path attribute, removes AS_CONFED_* segments, and also returns path length */
static int
validate_path(struct bgp_proto *p, int as_path, int bs, byte *idata, uint *ilength)
{
int res = 0;
u8 *a, *dst;
int len, plen;
dst = a = idata;
len = *ilength;
while (len)
{
if (len < 2)
return -1;
plen = 2 + bs * a[1];
if (len < plen)
return -1;
if (a[1] == 0)
{
log(L_WARN "%s: %s_PATH attribute contains empty segment, skipping it",
p->p.name, as_path ? "AS" : "AS4");
goto skip;
}
switch (a[0])
{
case AS_PATH_SET:
res++;
break;
case AS_PATH_SEQUENCE:
res += a[1];
break;
case AS_PATH_CONFED_SEQUENCE:
case AS_PATH_CONFED_SET:
if (as_path && path_segment_contains(a, bs, p->remote_as))
{
log(L_WARN "%s: AS_CONFED_* segment with peer ASN found, misconfigured confederation?", p->p.name);
return -1;
}
log(L_WARN "%s: %s_PATH attribute contains AS_CONFED_* segment, skipping segment",
p->p.name, as_path ? "AS" : "AS4");
goto skip;
default:
return -1;
}
if (dst != a)
memmove(dst, a, plen);
dst += plen;
skip:
len -= plen;
a += plen;
}
*ilength = dst - idata;
return res;
}
static inline int
validate_as_path(struct bgp_proto *p, byte *a, int *len)
{
return validate_path(p, 1, p->as4_session ? 4 : 2, a, len);
}
static inline int
validate_as4_path(struct bgp_proto *p, struct adata *path)
{
return validate_path(p, 0, 4, path->data, &path->length);
}
static int
bgp_check_next_hop(struct bgp_proto *p UNUSED, byte *a UNUSED6, int len UNUSED6)
{
#ifdef IPV6
return IGNORE;
#else
ip_addr addr;
memcpy(&addr, a, len);
ipa_ntoh(addr);
if (ipa_classify(addr) & IADDR_HOST)
return 0;
else
return 8;
#endif
}
static void
bgp_format_next_hop(eattr *a, byte *buf, int buflen UNUSED)
{
ip_addr *ipp = (ip_addr *) a->u.ptr->data;
#ifdef IPV6
/* in IPv6, we might have two addresses in NEXT HOP */
if ((a->u.ptr->length == NEXT_HOP_LENGTH) && ipa_nonzero(ipp[1]))
{
bsprintf(buf, "%I %I", ipp[0], ipp[1]);
return;
}
#endif
bsprintf(buf, "%I", ipp[0]);
}
static int
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 : WITHDRAW;
}
static void
bgp_format_aggregator(eattr *a, byte *buf, int buflen UNUSED)
{
struct adata *ad = a->u.ptr;
byte *data = ad->data;
u32 as;
as = get_u32(data);
data += 4;
bsprintf(buf, "%d.%d.%d.%d AS%u", 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)
{
return ((len % 4) == 0) ? 0 : 5;
}
static void
bgp_format_cluster_list(eattr *a, byte *buf, int buflen)
{
/* Truncates cluster lists larger than buflen, probably not a problem */
int_set_format(a->u.ptr, 0, -1, buf, buflen);
}
static int
bgp_check_reach_nlri(struct bgp_proto *p UNUSED, byte *a UNUSED, int len UNUSED)
{
#ifdef IPV6
p->mp_reach_start = a;
p->mp_reach_len = len;
#endif
return IGNORE;
}
static int
bgp_check_unreach_nlri(struct bgp_proto *p UNUSED, byte *a UNUSED, int len UNUSED)
{
#ifdef IPV6
p->mp_unreach_start = a;
p->mp_unreach_len = len;
#endif
return IGNORE;
}
static int
bgp_check_ext_community(struct bgp_proto *p UNUSED, byte *a UNUSED, int len)
{
return ((len % 8) == 0) ? 0 : WITHDRAW;
}
static int
bgp_check_large_community(struct bgp_proto *p UNUSED, byte *a UNUSED, int len)
{
return ((len % 12) == 0) ? 0 : WITHDRAW;
}
static struct attr_desc bgp_attr_table[] = {
{ NULL, -1, 0, 0, 0, /* Undefined */
NULL, NULL },
{ "origin", 1, BAF_TRANSITIVE, EAF_TYPE_INT, 1, /* BA_ORIGIN */
bgp_check_origin, bgp_format_origin },
{ "as_path", -1, BAF_TRANSITIVE, EAF_TYPE_AS_PATH, 1, /* BA_AS_PATH */
NULL, NULL }, /* is checked by validate_as_path() as a special case */
{ "next_hop", 4, BAF_TRANSITIVE, EAF_TYPE_IP_ADDRESS, 1, /* BA_NEXT_HOP */
bgp_check_next_hop, bgp_format_next_hop },
{ "med", 4, BAF_OPTIONAL, EAF_TYPE_INT, 1, /* BA_MULTI_EXIT_DISC */
NULL, NULL },
{ "local_pref", 4, BAF_TRANSITIVE, EAF_TYPE_INT, 0, /* BA_LOCAL_PREF */
NULL, NULL },
{ "atomic_aggr", 0, BAF_TRANSITIVE, EAF_TYPE_OPAQUE, 1, /* BA_ATOMIC_AGGR */
NULL, NULL },
{ "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 */
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 */
{ "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 },
{ "ext_community", -1, BAF_OPTIONAL | BAF_TRANSITIVE, EAF_TYPE_EC_SET, 1, /* BA_EXT_COMMUNITY */
bgp_check_ext_community, NULL },
{ "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 */
NULL, NULL },
[BA_LARGE_COMMUNITY] =
{ "large_community", -1, BAF_OPTIONAL | BAF_TRANSITIVE, EAF_TYPE_LC_SET, 1,
bgp_check_large_community, NULL }
};
/* BA_AS4_PATH is type EAF_TYPE_OPAQUE and not type EAF_TYPE_AS_PATH.
* It does not matter as this attribute does not appear on routes in the routing table.
*/
#define ATTR_KNOWN(code) ((code) < ARRAY_SIZE(bgp_attr_table) && bgp_attr_table[code].name)
static inline struct adata *
bgp_alloc_adata(struct linpool *pool, unsigned len)
{
struct adata *ad = lp_alloc(pool, sizeof(struct adata) + len);
ad->length = len;
return ad;
}
static void
bgp_set_attr(eattr *e, unsigned attr, uintptr_t val)
{
ASSERT(ATTR_KNOWN(attr));
e->id = EA_CODE(EAP_BGP, attr);
e->type = bgp_attr_table[attr].type;
e->flags = bgp_attr_table[attr].expected_flags;
if (e->type & EAF_EMBEDDED)
e->u.data = val;
else
e->u.ptr = (struct adata *) val;
}
static byte *
bgp_set_attr_wa(eattr *e, struct linpool *pool, unsigned attr, unsigned len)
{
struct adata *ad = bgp_alloc_adata(pool, len);
bgp_set_attr(e, attr, (uintptr_t) ad);
return ad->data;
}
void
bgp_attach_attr(ea_list **to, struct linpool *pool, unsigned attr, uintptr_t val)
{
ea_list *a = lp_alloc(pool, sizeof(ea_list) + sizeof(eattr));
a->next = *to;
*to = a;
a->flags = EALF_SORTED;
a->count = 1;
bgp_set_attr(a->attrs, attr, val);
}
byte *
bgp_attach_attr_wa(ea_list **to, struct linpool *pool, unsigned attr, unsigned len)
{
struct adata *ad = bgp_alloc_adata(pool, len);
bgp_attach_attr(to, pool, attr, (uintptr_t) ad);
return ad->data;
}
static int
bgp_encode_attr_hdr(byte *dst, uint flags, unsigned code, int len)
{
int wlen;
DBG("\tAttribute %02x (%d bytes, flags %02x)\n", code, len, flags);
if (len < 256)
{
*dst++ = flags;
*dst++ = code;
*dst++ = len;
wlen = 3;
}
else
{
*dst++ = flags | BAF_EXT_LEN;
*dst++ = code;
put_u16(dst, len);
wlen = 4;
}
return wlen;
}
static void
aggregator_convert_to_old(struct adata *aggr, byte *dst, int *new_used)
{
byte *src = aggr->data;
*new_used = 0;
u32 as = get_u32(src);
if (as > 0xFFFF)
{
as = AS_TRANS;
*new_used = 1;
}
put_u16(dst, as);
/* Copy IPv4 address */
memcpy(dst + 2, src + 4, 4);
}
static void
aggregator_convert_to_new(struct adata *aggr, byte *dst)
{
byte *src = aggr->data;
u32 as = get_u16(src);
put_u32(dst, as);
/* Copy IPv4 address */
memcpy(dst + 4, src + 2, 4);
}
static int
bgp_get_attr_len(eattr *a)
{
int len;
if (ATTR_KNOWN(EA_ID(a->id)))
{
int code = EA_ID(a->id);
struct attr_desc *desc = &bgp_attr_table[code];
len = desc->expected_length;
if (len < 0)
{
ASSERT(!(a->type & EAF_EMBEDDED));
len = a->u.ptr->length;
}
}
else
{
ASSERT((a->type & EAF_TYPE_MASK) == EAF_TYPE_OPAQUE);
len = a->u.ptr->length;
}
return len;
}
#define ADVANCE(w, r, l) do { r -= l; w += l; } while (0)
/**
* bgp_encode_attrs - encode BGP attributes
* @p: BGP instance
* @w: buffer
* @attrs: a list of extended attributes
* @remains: remaining space in the buffer
*
* 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.
*/
uint
bgp_encode_attrs(struct bgp_proto *p, byte *w, ea_list *attrs, int remains)
{
uint i, code, type, flags;
byte *start = w;
int len, rv;
for(i=0; i<attrs->count; i++)
{
eattr *a = &attrs->attrs[i];
ASSERT(EA_PROTO(a->id) == EAP_BGP);
code = EA_ID(a->id);
#ifdef IPV6
/* When talking multiprotocol BGP, the NEXT_HOP attributes are used only temporarily. */
if (code == BA_NEXT_HOP)
continue;
#endif
/* When AS4-aware BGP speaker is talking to non-AS4-aware BGP speaker,
* we have to convert our 4B AS_PATH to 2B AS_PATH and send our AS_PATH
* as optional AS4_PATH attribute.
*/
if ((code == BA_AS_PATH) && (! p->as4_session))
{
len = a->u.ptr->length;
if (remains < (len + 4))
goto err_no_buffer;
/* Using temporary buffer because don't know a length of created attr
* and therefore a length of a header. Perhaps i should better always
* use BAF_EXT_LEN. */
byte buf[len];
int new_used;
int nl = as_path_convert_to_old(a->u.ptr, buf, &new_used);
DBG("BGP: Encoding old AS_PATH\n");
rv = bgp_encode_attr_hdr(w, BAF_TRANSITIVE, BA_AS_PATH, nl);
ADVANCE(w, remains, rv);
memcpy(w, buf, nl);
ADVANCE(w, remains, nl);
if (! new_used)
continue;
if (remains < (len + 4))
goto err_no_buffer;
/* We should discard AS_CONFED_SEQUENCE or AS_CONFED_SET path segments
* here but we don't support confederations and such paths we already
* discarded in bgp_check_as_path().
*/
DBG("BGP: Encoding AS4_PATH\n");
rv = bgp_encode_attr_hdr(w, BAF_OPTIONAL | BAF_TRANSITIVE, BA_AS4_PATH, len);
ADVANCE(w, remains, rv);
memcpy(w, a->u.ptr->data, len);
ADVANCE(w, remains, len);
continue;
}
/* The same issue with AGGREGATOR attribute */
if ((code == BA_AGGREGATOR) && (! p->as4_session))
{
int new_used;
len = 6;
if (remains < (len + 3))
goto err_no_buffer;
rv = bgp_encode_attr_hdr(w, BAF_OPTIONAL | BAF_TRANSITIVE, BA_AGGREGATOR, len);
ADVANCE(w, remains, rv);
aggregator_convert_to_old(a->u.ptr, w, &new_used);
ADVANCE(w, remains, len);
if (! new_used)
continue;
len = 8;
if (remains < (len + 3))
goto err_no_buffer;
rv = bgp_encode_attr_hdr(w, BAF_OPTIONAL | BAF_TRANSITIVE, BA_AS4_AGGREGATOR, len);
ADVANCE(w, remains, rv);
memcpy(w, a->u.ptr->data, len);
ADVANCE(w, remains, len);
continue;
}
/* Standard path continues here ... */
type = a->type & EAF_TYPE_MASK;
flags = a->flags & (BAF_OPTIONAL | BAF_TRANSITIVE | BAF_PARTIAL);
len = bgp_get_attr_len(a);
/* Skip empty sets */
if (((type == EAF_TYPE_INT_SET) || (type == EAF_TYPE_EC_SET) || (type == EAF_TYPE_LC_SET)) && (len == 0))
continue;
if (remains < len + 4)
goto err_no_buffer;
rv = bgp_encode_attr_hdr(w, flags, code, len);
ADVANCE(w, remains, rv);
switch (type)
{
case EAF_TYPE_INT:
case EAF_TYPE_ROUTER_ID:
if (len == 4)
put_u32(w, a->u.data);
else
*w = a->u.data;
break;
case EAF_TYPE_IP_ADDRESS:
{
ip_addr ip = *(ip_addr *)a->u.ptr->data;
ipa_hton(ip);
memcpy(w, &ip, len);
break;
}
case EAF_TYPE_INT_SET:
case EAF_TYPE_LC_SET:
case EAF_TYPE_EC_SET:
{
u32 *z = int_set_get_data(a->u.ptr);
int i;
for(i=0; i<len; i+=4)
put_u32(w+i, *z++);
break;
}
case EAF_TYPE_OPAQUE:
case EAF_TYPE_AS_PATH:
memcpy(w, a->u.ptr->data, len);
break;
default:
bug("bgp_encode_attrs: unknown attribute type %02x", a->type);
}
ADVANCE(w, remains, len);
}
return w - start;
err_no_buffer:
return -1;
}
/*
static void
bgp_init_prefix(struct fib_node *N)
{
struct bgp_prefix *p = (struct bgp_prefix *) N;
p->bucket_node.next = NULL;
}
*/
static int
bgp_compare_u32(const u32 *x, const u32 *y)
{
return (*x < *y) ? -1 : (*x > *y) ? 1 : 0;
}
static inline void
bgp_normalize_int_set(u32 *dest, u32 *src, unsigned cnt)
{
memcpy(dest, src, sizeof(u32) * cnt);
qsort(dest, cnt, sizeof(u32), (int(*)(const void *, const void *)) bgp_compare_u32);
}
static int
bgp_compare_ec(const u32 *xp, const u32 *yp)
{
u64 x = ec_get(xp, 0);
u64 y = ec_get(yp, 0);
return (x < y) ? -1 : (x > y) ? 1 : 0;
}
static inline void
bgp_normalize_ec_set(struct adata *ad, u32 *src, int internal)
{
u32 *dst = int_set_get_data(ad);
/* Remove non-transitive communities (EC_TBIT active) on external sessions */
if (! internal)
{
int len = int_set_get_size(ad);
u32 *t = dst;
int i;
for (i=0; i < len; i += 2)
{
if (src[i] & EC_TBIT)
continue;
*t++ = src[i];
*t++ = src[i+1];
}
ad->length = (t - dst) * 4;
}
else
memcpy(dst, src, ad->length);
qsort(dst, ad->length / 8, 8, (int(*)(const void *, const void *)) bgp_compare_ec);
}
static int
bgp_compare_lc(const u32 *x, const u32 *y)
{
if (x[0] != y[0])
return (x[0] > y[0]) ? 1 : -1;
if (x[1] != y[1])
return (x[1] > y[1]) ? 1 : -1;
if (x[2] != y[2])
return (x[2] > y[2]) ? 1 : -1;
return 0;
}
static inline void
bgp_normalize_lc_set(u32 *dest, u32 *src, unsigned cnt)
{
memcpy(dest, src, LCOMM_LENGTH * cnt);
qsort(dest, cnt, LCOMM_LENGTH, (int(*)(const void *, const void *)) bgp_compare_lc);
}
static void
bgp_rehash_buckets(struct bgp_proto *p)
{
struct bgp_bucket **old = p->bucket_hash;
struct bgp_bucket **new;
unsigned oldn = p->hash_size;
unsigned i, e, mask;
struct bgp_bucket *b;
p->hash_size = p->hash_limit;
DBG("BGP: Rehashing bucket table from %d to %d\n", oldn, p->hash_size);
p->hash_limit *= 4;
if (p->hash_limit >= 65536)
p->hash_limit = ~0;
new = p->bucket_hash = mb_allocz(p->p.pool, p->hash_size * sizeof(struct bgp_bucket *));
mask = p->hash_size - 1;
for (i=0; i<oldn; i++)
while (b = old[i])
{
old[i] = b->hash_next;
e = b->hash & mask;
b->hash_next = new[e];
if (b->hash_next)
b->hash_next->hash_prev = b;
b->hash_prev = NULL;
new[e] = b;
}
mb_free(old);
}
static struct bgp_bucket *
bgp_new_bucket(struct bgp_proto *p, ea_list *new, unsigned hash)
{
struct bgp_bucket *b;
unsigned ea_size = sizeof(ea_list) + new->count * sizeof(eattr);
unsigned ea_size_aligned = BIRD_ALIGN(ea_size, CPU_STRUCT_ALIGN);
unsigned size = sizeof(struct bgp_bucket) + ea_size_aligned;
unsigned i;
byte *dest;
unsigned index = hash & (p->hash_size - 1);
/* 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 and hash it */
b = mb_alloc(p->p.pool, size);
b->hash_next = p->bucket_hash[index];
if (b->hash_next)
b->hash_next->hash_prev = b;
p->bucket_hash[index] = b;
b->hash_prev = NULL;
b->hash = hash;
add_tail(&p->bucket_queue, &b->send_node);
init_list(&b->prefixes);
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);
}
}
/* If needed, rehash */
p->hash_count++;
if (p->hash_count > p->hash_limit)
bgp_rehash_buckets(p);
return b;
}
static struct bgp_bucket *
bgp_get_bucket(struct bgp_proto *p, net *n, ea_list *attrs, int originate)
{
ea_list *new;
unsigned i, cnt, hash, code;
eattr *a, *d;
u32 seen = 0;
struct bgp_bucket *b;
/* Merge the attribute list */
new = alloca(ea_scan(attrs));
ea_merge(attrs, new);
ea_sort(new);
/* Normalize attributes */
d = new->attrs;
cnt = new->count;
new->count = 0;
for(i=0; i<cnt; i++)
{
a = &new->attrs[i];
if (EA_PROTO(a->id) != EAP_BGP)
continue;
code = EA_ID(a->id);
if (ATTR_KNOWN(code))
{
if (!bgp_attr_table[code].allow_in_ebgp && !p->is_internal)
continue;
/* The flags might have been zero if the attr was added by filters */
a->flags = (a->flags & BAF_PARTIAL) | bgp_attr_table[code].expected_flags;
if (code < 32)
seen |= 1 << code;
}
else
{
/* Don't re-export unknown non-transitive attributes */
if (!(a->flags & BAF_TRANSITIVE))
continue;
}
*d = *a;
if ((d->type & EAF_ORIGINATED) && !originate && (d->flags & BAF_TRANSITIVE) && (d->flags & BAF_OPTIONAL))
d->flags |= BAF_PARTIAL;
switch (d->type & EAF_TYPE_MASK)
{
case EAF_TYPE_INT_SET:
{
struct adata *z = alloca(sizeof(struct adata) + d->u.ptr->length);
z->length = d->u.ptr->length;
bgp_normalize_int_set((u32 *) z->data, (u32 *) d->u.ptr->data, z->length / 4);
d->u.ptr = z;
break;
}
case EAF_TYPE_EC_SET:
{
struct adata *z = alloca(sizeof(struct adata) + d->u.ptr->length);
z->length = d->u.ptr->length;
bgp_normalize_ec_set(z, (u32 *) d->u.ptr->data, p->is_internal);
d->u.ptr = z;
break;
}
case EAF_TYPE_LC_SET:
{
struct adata *z = alloca(sizeof(struct adata) + d->u.ptr->length);
z->length = d->u.ptr->length;
bgp_normalize_lc_set((u32 *) z->data, (u32 *) d->u.ptr->data, z->length / LCOMM_LENGTH);
d->u.ptr = z;
break;
}
default: ;
}
d++;
new->count++;
}
/* Hash */
hash = ea_hash(new);
for(b=p->bucket_hash[hash & (p->hash_size - 1)]; b; b=b->hash_next)
if (b->hash == hash && ea_same(b->eattrs, new))
{
DBG("Found bucket.\n");
return b;
}
/* Ensure that there are all mandatory attributes */
for(i=0; i<ARRAY_SIZE(bgp_mandatory_attrs); i++)
if (!(seen & (1 << bgp_mandatory_attrs[i])))
{
log(L_ERR "%s: Mandatory attribute %s missing in route %I/%d", p->p.name, bgp_attr_table[bgp_mandatory_attrs[i]].name, n->n.prefix, n->n.pxlen);
return NULL;
}
/* Check if next hop is valid */
a = ea_find(new, EA_CODE(EAP_BGP, BA_NEXT_HOP));
if (!a || ipa_equal(p->cf->remote_ip, *(ip_addr *)a->u.ptr->data))
{
log(L_ERR "%s: Invalid NEXT_HOP attribute in route %I/%d", p->p.name, n->n.prefix, n->n.pxlen);
return NULL;
}
/* Create new bucket */
DBG("Creating bucket.\n");
return bgp_new_bucket(p, new, hash);
}
void
bgp_free_bucket(struct bgp_proto *p, struct bgp_bucket *buck)
{
if (buck->hash_next)
buck->hash_next->hash_prev = buck->hash_prev;
if (buck->hash_prev)
buck->hash_prev->hash_next = buck->hash_next;
else
p->bucket_hash[buck->hash & (p->hash_size-1)] = buck->hash_next;
mb_free(buck);
}
/* Prefix hash table */
#define PXH_KEY(n1) n1->n.prefix, n1->n.pxlen, n1->path_id
#define PXH_NEXT(n) n->next
#define PXH_EQ(p1,l1,i1,p2,l2,i2) ipa_equal(p1, p2) && l1 == l2 && i1 == i2
#define PXH_FN(p,l,i) ipa_hash32(p) ^ u32_hash((l << 16) ^ i)
#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_proto *p, u32 order)
{
HASH_INIT(p->prefix_hash, p->p.pool, order);
p->prefix_slab = sl_new(p->p.pool, sizeof(struct bgp_prefix));
}
static struct bgp_prefix *
bgp_get_prefix(struct bgp_proto *p, ip_addr prefix, int pxlen, u32 path_id)
{
struct bgp_prefix *bp = HASH_FIND(p->prefix_hash, PXH, prefix, pxlen, path_id);
if (bp)
return bp;
bp = sl_alloc(p->prefix_slab);
bp->n.prefix = prefix;
bp->n.pxlen = pxlen;
bp->path_id = path_id;
bp->bucket_node.next = NULL;
HASH_INSERT2(p->prefix_hash, PXH, p->p.pool, bp);
return bp;
}
void
bgp_free_prefix(struct bgp_proto *p, struct bgp_prefix *bp)
{
HASH_REMOVE2(p->prefix_hash, PXH, p->p.pool, bp);
sl_free(p->prefix_slab, bp);
}
void
bgp_rt_notify(struct proto *P, rtable *tbl UNUSED, net *n, rte *new, rte *old UNUSED, ea_list *attrs)
{
struct bgp_proto *p = (struct bgp_proto *) P;
struct bgp_bucket *buck;
struct bgp_prefix *px;
rte *key;
u32 path_id;
DBG("BGP: Got route %I/%d %s\n", n->n.prefix, n->n.pxlen, new ? "up" : "down");
if (new)
{
key = new;
buck = bgp_get_bucket(p, n, attrs, new->attrs->source != RTS_BGP);
if (!buck) /* Inconsistent attribute list */
return;
}
else
{
key = old;
if (!(buck = p->withdraw_bucket))
{
buck = p->withdraw_bucket = mb_alloc(P->pool, sizeof(struct bgp_bucket));
init_list(&buck->prefixes);
}
}
path_id = p->add_path_tx ? key->attrs->src->global_id : 0;
px = bgp_get_prefix(p, n->n.prefix, n->n.pxlen, path_id);
if (px->bucket_node.next)
{
DBG("\tRemoving old entry.\n");
rem_node(&px->bucket_node);
}
add_tail(&buck->prefixes, &px->bucket_node);
bgp_schedule_packet(p->conn, PKT_UPDATE);
}
static int
bgp_create_attrs(struct bgp_proto *p, rte *e, ea_list **attrs, struct linpool *pool)
{
ea_list *ea = lp_alloc(pool, sizeof(ea_list) + 4*sizeof(eattr));
rta *rta = e->attrs;
byte *z;
ea->next = *attrs;
*attrs = ea;
ea->flags = EALF_SORTED;
ea->count = 4;
bgp_set_attr(ea->attrs, BA_ORIGIN,
((rta->source == RTS_OSPF_EXT1) || (rta->source == RTS_OSPF_EXT2)) ? ORIGIN_INCOMPLETE : ORIGIN_IGP);
if (p->is_internal)
bgp_set_attr_wa(ea->attrs+1, pool, BA_AS_PATH, 0);
else
{
z = bgp_set_attr_wa(ea->attrs+1, pool, BA_AS_PATH, 6);
z[0] = AS_PATH_SEQUENCE;
z[1] = 1; /* 1 AS */
put_u32(z+2, p->local_as);
}
/* iBGP -> use gw, eBGP multi-hop -> use source_addr,
eBGP single-hop -> use gw if on the same iface */
z = bgp_set_attr_wa(ea->attrs+2, pool, BA_NEXT_HOP, NEXT_HOP_LENGTH);
if (p->cf->next_hop_self ||
rta->dest != RTD_ROUTER ||
ipa_equal(rta->gw, IPA_NONE) ||
ipa_is_link_local(rta->gw) ||
(!p->is_internal && !p->cf->next_hop_keep &&
(!p->neigh || (rta->iface != p->neigh->iface))))
set_next_hop(z, p->source_addr);
else
set_next_hop(z, rta->gw);
bgp_set_attr(ea->attrs+3, BA_LOCAL_PREF, p->cf->default_local_pref);
return 0; /* Leave decision to the filters */
}
static inline int
bgp_as_path_loopy(struct bgp_proto *p, rta *a)
{
int num = p->cf->allow_local_as + 1;
eattr *e = ea_find(a->eattrs, EA_CODE(EAP_BGP, BA_AS_PATH));
return (e && (num > 0) && as_path_contains(e->u.ptr, p->local_as, num));
}
static inline int
bgp_originator_id_loopy(struct bgp_proto *p, rta *a)
{
eattr *e = ea_find(a->eattrs, EA_CODE(EAP_BGP, BA_ORIGINATOR_ID));
return (e && (e->u.data == p->local_id));
}
static inline int
bgp_cluster_list_loopy(struct bgp_proto *p, rta *a)
{
eattr *e = ea_find(a->eattrs, EA_CODE(EAP_BGP, BA_CLUSTER_LIST));
return (e && p->rr_client && int_set_contains(e->u.ptr, p->rr_cluster_id));
}
static inline void
bgp_path_prepend(rte *e, ea_list **attrs, struct linpool *pool, u32 as)
{
eattr *a = ea_find(e->attrs->eattrs, EA_CODE(EAP_BGP, BA_AS_PATH));
bgp_attach_attr(attrs, pool, BA_AS_PATH, (uintptr_t) as_path_prepend(pool, a->u.ptr, as));
}
static inline void
bgp_cluster_list_prepend(rte *e, ea_list **attrs, struct linpool *pool, u32 cid)
{
eattr *a = ea_find(e->attrs->eattrs, EA_CODE(EAP_BGP, BA_CLUSTER_LIST));
bgp_attach_attr(attrs, pool, BA_CLUSTER_LIST, (uintptr_t) int_set_prepend(pool, a ? a->u.ptr : NULL, cid));
}
static int
bgp_update_attrs(struct bgp_proto *p, rte *e, ea_list **attrs, struct linpool *pool, int rr)
{
eattr *a;
if (!p->is_internal && !p->rs_client)
{
bgp_path_prepend(e, attrs, pool, p->local_as);
/* The MULTI_EXIT_DISC attribute received from a neighboring AS MUST NOT be
* propagated to other neighboring ASes.
* Perhaps it would be better to undefine it.
*/
a = ea_find(e->attrs->eattrs, EA_CODE(EAP_BGP, BA_MULTI_EXIT_DISC));
if (a)
bgp_attach_attr(attrs, pool, BA_MULTI_EXIT_DISC, 0);
}
/* iBGP -> keep next_hop, eBGP multi-hop -> use source_addr,
* eBGP single-hop -> keep next_hop if on the same iface.
* If the next_hop is zero (i.e. link-local), keep only if on the same iface.
*
* Note that same-iface-check uses iface from route, which is based on gw.
*/
a = ea_find(e->attrs->eattrs, EA_CODE(EAP_BGP, BA_NEXT_HOP));
if (a && !p->cf->next_hop_self &&
(p->cf->next_hop_keep ||
(p->is_internal && ipa_nonzero(*((ip_addr *) a->u.ptr->data))) ||
(p->neigh && (e->attrs->iface == p->neigh->iface))))
{
/* Leave the original next hop attribute, will check later where does it point */
}
else
{
/* Need to create new one */
byte *b = bgp_attach_attr_wa(attrs, pool, BA_NEXT_HOP, NEXT_HOP_LENGTH);
set_next_hop(b, p->source_addr);
}
if (rr)
{
/* Handling route reflection, RFC 4456 */
struct bgp_proto *src = (struct bgp_proto *) e->attrs->src->proto;
a = ea_find(e->attrs->eattrs, EA_CODE(EAP_BGP, BA_ORIGINATOR_ID));
if (!a)
bgp_attach_attr(attrs, pool, BA_ORIGINATOR_ID, src->remote_id);
/* We attach proper cluster ID according to whether the route is entering or leaving the cluster */
bgp_cluster_list_prepend(e, attrs, pool, src->rr_client ? src->rr_cluster_id : p->rr_cluster_id);
/* Two RR clients with different cluster ID, hmmm */
if (src->rr_client && p->rr_client && (src->rr_cluster_id != p->rr_cluster_id))
bgp_cluster_list_prepend(e, attrs, pool, p->rr_cluster_id);
}
return 0; /* Leave decision to the filters */
}
static int
bgp_community_filter(struct bgp_proto *p, rte *e)
{
eattr *a;
struct adata *d;
/* Check if we aren't forbidden to export the route by communities */
a = ea_find(e->attrs->eattrs, EA_CODE(EAP_BGP, BA_COMMUNITY));
if (a)
{
d = a->u.ptr;
if (int_set_contains(d, BGP_COMM_NO_ADVERTISE))
{
DBG("\tNO_ADVERTISE\n");
return 1;
}
if (!p->is_internal &&
(int_set_contains(d, BGP_COMM_NO_EXPORT) ||
int_set_contains(d, BGP_COMM_NO_EXPORT_SUBCONFED)))
{
DBG("\tNO_EXPORT\n");
return 1;
}
}
return 0;
}
int
bgp_import_control(struct proto *P, rte **new, ea_list **attrs, struct linpool *pool)
{
rte *e = *new;
struct bgp_proto *p = (struct bgp_proto *) P;
struct bgp_proto *new_bgp = (e->attrs->src->proto->proto == &proto_bgp) ?
(struct bgp_proto *) e->attrs->src->proto : NULL;
if (p == new_bgp) /* Poison reverse updates */
return -1;
if (new_bgp)
{
/* We should check here for cluster list loop, because the receiving BGP instance
might have different cluster ID */
if (bgp_cluster_list_loopy(p, e->attrs))
return -1;
if (p->cf->interpret_communities && bgp_community_filter(p, e))
return -1;
if (p->local_as == new_bgp->local_as && p->is_internal && new_bgp->is_internal)
{
/* Redistribution of internal routes with IBGP */
if (p->rr_client || new_bgp->rr_client)
/* Route reflection, RFC 4456 */
return bgp_update_attrs(p, e, attrs, pool, 1);
else
return -1;
}
else
return bgp_update_attrs(p, e, attrs, pool, 0);
}
else
return bgp_create_attrs(p, e, attrs, pool);
}
static inline u32
bgp_get_neighbor(rte *r)
{
eattr *e = ea_find(r->attrs->eattrs, EA_CODE(EAP_BGP, BA_AS_PATH));
u32 as;
if (e && as_path_get_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)
{
int rd = rt->attrs->dest;
return (rd == RTD_ROUTER) || (rd == RTD_DEVICE) || (rd == RTD_MULTIPATH);
}
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_internal > old_bgp->is_internal)
return 0;
if (new_bgp->is_internal < old_bgp->is_internal)
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 neighor 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;
}
static struct adata *
bgp_aggregator_convert_to_new(struct adata *old, struct linpool *pool)
{
struct adata *newa = lp_alloc(pool, sizeof(struct adata) + 8);
newa->length = 8;
aggregator_convert_to_new(old, newa->data);
return newa;
}
/* Take last req_as ASNs from path old2 (in 2B format), convert to 4B format
* and append path old4 (in 4B format).
*/
static struct adata *
bgp_merge_as_paths(struct adata *old2, struct adata *old4, int req_as, struct linpool *pool)
{
byte buf[old2->length * 2];
int ol = as_path_convert_to_new(old2, buf, req_as);
int nl = ol + (old4 ? old4->length : 0);
struct adata *newa = lp_alloc(pool, sizeof(struct adata) + nl);
newa->length = nl;
memcpy(newa->data, buf, ol);
if (old4) memcpy(newa->data + ol, old4->data, old4->length);
return newa;
}
static int
as4_aggregator_valid(struct adata *aggr)
{
return aggr->length == 8;
}
/* Reconstruct 4B AS_PATH and AGGREGATOR according to RFC 4893 4.2.3 */
static void
bgp_reconstruct_4b_atts(struct bgp_proto *p, rta *a, struct linpool *pool)
{
eattr *p2 =ea_find(a->eattrs, EA_CODE(EAP_BGP, BA_AS_PATH));
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 "%s: AS4_AGGREGATOR attribute is invalid, skipping attribute", p->p.name);
a4 = NULL;
a4_removed = 1;
}
if (a2)
{
u32 a2_as = get_u16(a2->u.ptr->data);
if (a4)
{
if (a2_as != AS_TRANS)
{
/* Routes were aggregated by old router and therefore AS4_PATH
* and AS4_AGGREGATOR is invalid
*
* Convert AS_PATH and AGGREGATOR to 4B format and finish.
*/
a2->u.ptr = bgp_aggregator_convert_to_new(a2->u.ptr, pool);
p2->u.ptr = bgp_merge_as_paths(p2->u.ptr, NULL, AS_PATH_MAXLEN, pool);
return;
}
else
{
/* Common case, use AS4_AGGREGATOR attribute */
a2->u.ptr = a4->u.ptr;
}
}
else
{
/* Common case, use old AGGREGATOR attribute */
a2->u.ptr = bgp_aggregator_convert_to_new(a2->u.ptr, pool);
if ((a2_as == AS_TRANS) && !a4_removed)
log(L_WARN "%s: AGGREGATOR attribute contain AS_TRANS, but AS4_AGGREGATOR is missing", p->p.name);
}
}
else
if (a4)
log(L_WARN "%s: AS4_AGGREGATOR attribute received, but AGGREGATOR attribute is missing", p->p.name);
int p2_len = as_path_getlen_int(p2->u.ptr, 2);
int p4_len = p4 ? validate_as4_path(p, p4->u.ptr) : -1;
if (p4 && (p4_len < 0))
log(L_WARN "%s: AS4_PATH attribute is malformed, skipping attribute", p->p.name);
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
bgp_remove_as4_attrs(struct bgp_proto *p, rta *a)
{
unsigned id1 = EA_CODE(EAP_BGP, BA_AS4_PATH);
unsigned id2 = EA_CODE(EAP_BGP, BA_AS4_AGGREGATOR);
ea_list **el = &(a->eattrs);
/* We know that ea_lists constructed in bgp_decode attrs have one attribute per ea_list struct */
while (*el != NULL)
{
unsigned fid = (*el)->attrs[0].id;
if ((fid == id1) || (fid == id2))
{
*el = (*el)->next;
if (p->as4_session)
log(L_WARN "%s: Unexpected AS4_* attributes received", p->p.name);
}
else
el = &((*el)->next);
}
}
/**
* bgp_decode_attrs - check and decode BGP attributes
* @conn: connection
* @attr: start of attribute block
* @len: length of attribute block
* @pool: linear pool to make all the allocations in
* @mandatory: 1 iff presence of mandatory attributes has to be checked
*
* 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 a &rta.
*/
struct rta *
bgp_decode_attrs(struct bgp_conn *conn, byte *attr, uint len, struct linpool *pool, int mandatory)
{
struct bgp_proto *bgp = conn->bgp;
rta *a = lp_alloc(pool, sizeof(struct rta));
uint flags, code, l, i, type;
int errcode;
byte *z, *attr_start;
byte seen[256/8];
ea_list *ea;
struct adata *ad;
int withdraw = 0;
bzero(a, sizeof(rta));
a->source = RTS_BGP;
a->scope = SCOPE_UNIVERSE;
a->cast = RTC_UNICAST;
/* a->dest = RTD_ROUTER; -- set in bgp_set_next_hop() */
a->from = bgp->cf->remote_ip;
/* Parse the attributes */
bzero(seen, sizeof(seen));
DBG("BGP: Parsing attributes\n");
while (len)
{
if (len < 2)
goto malformed;
attr_start = attr;
flags = *attr++;
code = *attr++;
len -= 2;
if (flags & BAF_EXT_LEN)
{
if (len < 2)
goto malformed;
l = get_u16(attr);
attr += 2;
len -= 2;
}
else
{
if (len < 1)
goto malformed;
l = *attr++;
len--;
}
if (l > len)
goto malformed;
len -= l;
z = attr;
attr += l;
DBG("Attr %02x %02x %d\n", code, flags, l);
if (seen[code/8] & (1 << (code%8)))
goto malformed;
if (ATTR_KNOWN(code))
{
struct attr_desc *desc = &bgp_attr_table[code];
if (desc->expected_length >= 0 && desc->expected_length != (int) l)
{ errcode = 5; goto err; }
if ((desc->expected_flags ^ flags) & (BAF_OPTIONAL | BAF_TRANSITIVE))
{ errcode = 4; goto err; }
if (!desc->allow_in_ebgp && !bgp->is_internal)
continue;
if (desc->validate)
{
errcode = desc->validate(bgp, z, l);
if (errcode > 0)
goto err;
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)
{
/* Special case as it might also trim the attribute */
if (validate_as_path(bgp, z, &l) < 0)
{ errcode = 11; goto err; }
}
type = desc->type;
}
else /* Unknown attribute */
{
if (!(flags & BAF_OPTIONAL))
{ errcode = 2; goto err; }
type = EAF_TYPE_OPAQUE;
}
// Only OPTIONAL and TRANSITIVE attributes may have non-zero PARTIAL flag
// if (!((flags & BAF_OPTIONAL) && (flags & BAF_TRANSITIVE)) && (flags & BAF_PARTIAL))
// { errcode = 4; goto err; }
seen[code/8] |= (1 << (code%8));
ea = lp_alloc(pool, sizeof(ea_list) + sizeof(eattr));
ea->next = a->eattrs;
a->eattrs = ea;
ea->flags = 0;
ea->count = 1;
ea->attrs[0].id = EA_CODE(EAP_BGP, code);
ea->attrs[0].flags = flags;
ea->attrs[0].type = type;
if (type & EAF_EMBEDDED)
ad = NULL;
else
{
ad = lp_alloc(pool, sizeof(struct adata) + l);
ea->attrs[0].u.ptr = ad;
ad->length = l;
memcpy(ad->data, z, l);
}
switch (type)
{
case EAF_TYPE_ROUTER_ID:
case EAF_TYPE_INT:
if (l == 1)
ea->attrs[0].u.data = *z;
else
ea->attrs[0].u.data = get_u32(z);
break;
case EAF_TYPE_IP_ADDRESS:
ipa_ntoh(*(ip_addr *)ad->data);
break;
case EAF_TYPE_INT_SET:
case EAF_TYPE_LC_SET:
case EAF_TYPE_EC_SET:
{
u32 *z = (u32 *) ad->data;
for(i=0; i<ad->length/4; i++)
z[i] = ntohl(z[i]);
break;
}
}
}
if (withdraw)
goto withdraw;
#ifdef IPV6
/* If we received MP_REACH_NLRI we should check mandatory attributes */
if (bgp->mp_reach_len != 0)
mandatory = 1;
#endif
/* If there is no (reachability) NLRI, we should exit now */
if (! mandatory)
return a;
/* Check if all mandatory attributes are present */
for(i=0; i < ARRAY_SIZE(bgp_mandatory_attrs); i++)
{
code = bgp_mandatory_attrs[i];
if (!(seen[code/8] & (1 << (code%8))))
{
bgp_error(conn, 3, 3, &bgp_mandatory_attrs[i], 1);
return NULL;
}
}
/* When receiving attributes from non-AS4-aware BGP speaker,
* we have to reconstruct 4B AS_PATH and AGGREGATOR attributes
*/
if (! bgp->as4_session)
bgp_reconstruct_4b_atts(bgp, a, pool);
bgp_remove_as4_attrs(bgp, a);
/* If the AS path attribute contains our AS, reject the routes */
if (bgp_as_path_loopy(bgp, a))
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 withdraw;
/* If there's no local preference, define one */
if (!(seen[0] & (1 << BA_LOCAL_PREF)))
bgp_attach_attr(&a->eattrs, pool, BA_LOCAL_PREF, bgp->cf->default_local_pref);
return a;
withdraw:
return NULL;
malformed:
bgp_error(conn, 3, 1, NULL, 0);
return NULL;
err:
bgp_error(conn, 3, errcode, attr_start, z+l-attr_start);
return NULL;
}
int
bgp_get_attr(eattr *a, byte *buf, int buflen)
{
uint i = EA_ID(a->id);
struct attr_desc *d;
int len;
if (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_init_bucket_table(struct bgp_proto *p)
{
p->hash_size = 256;
p->hash_limit = p->hash_size * 4;
p->bucket_hash = mb_allocz(p->p.pool, p->hash_size * sizeof(struct bgp_bucket *));
init_list(&p->bucket_queue);
p->withdraw_bucket = NULL;
// fib_init(&p->prefix_fib, p->p.pool, sizeof(struct bgp_prefix), 0, bgp_init_prefix);
}
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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