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a92fe607173b52cf28256f00399953c623788c35
labs-bird/proto/bgp/attrs.c
Ondrej Zajicek a92fe60717 Implementation of route server.
2008-11-01 12:55:43 +01:00

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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"
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);
};
static int
bgp_check_origin(struct bgp_proto *p UNUSED, byte *a UNUSED, int len)
{
if (len > 2)
return 6;
return 0;
}
static void
bgp_format_origin(eattr *a, byte *buf)
{
static char *bgp_origin_names[] = { "IGP", "EGP", "Incomplete" };
bsprintf(buf, bgp_origin_names[a->u.data]);
}
static int
bgp_check_path(byte *a, int len, int bs, int errcode)
{
while (len)
{
DBG("Path segment %02x %02x\n", a[0], a[1]);
if (len < 2 ||
(a[0] != AS_PATH_SET && a[0] != AS_PATH_SEQUENCE) ||
bs * a[1] + 2 > len)
return errcode;
len -= bs * a[1] + 2;
a += bs * a[1] + 2;
}
return 0;
}
static int
bgp_check_as_path(struct bgp_proto *p, byte *a, int len)
{
return bgp_check_path(a, len, p->as4_session ? 4 : 2, 11);
}
static int
bgp_check_as4_path(struct bgp_proto *p, byte *a, int len)
{
if (bgp_as4_support && (! p->as4_session))
return bgp_check_path(a, len, 4, 9);
else
return 0;
}
static int
bgp_check_next_hop(struct bgp_proto *p UNUSED, byte *a, int len)
{
#ifdef IPV6
return -1;
#else
ip_addr addr;
memcpy(&addr, a, len);
ipa_ntoh(addr);
if (ipa_classify(addr) & IADDR_HOST)
return 0;
else
return 8;
#endif
}
static int
bgp_check_aggregator(struct bgp_proto *p, UNUSED byte *a, int len)
{
int exp_len = p->as4_session ? 8 : 6;
return (len == exp_len) ? 0 : 5;
}
static int
bgp_check_cluster_list(struct bgp_proto *p UNUSED, UNUSED byte *a, int len)
{
return ((len % 4) == 0) ? 0 : 5;
}
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 -1;
}
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 -1;
}
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 */
bgp_check_as_path, NULL },
{ "next_hop", 4, BAF_TRANSITIVE, EAF_TYPE_IP_ADDRESS, 1, /* BA_NEXT_HOP */
bgp_check_next_hop, NULL },
{ "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, NULL },
{ "community", -1, BAF_OPTIONAL | BAF_TRANSITIVE, EAF_TYPE_INT_SET, 1, /* BA_COMMUNITY */
NULL, NULL },
{ "originator_id", 4, BAF_OPTIONAL, EAF_TYPE_INT, 0, /* BA_ORIGINATOR_ID */
NULL, NULL },
{ "cluster_list", -1, BAF_OPTIONAL, EAF_TYPE_INT_SET, 0, /* BA_CLUSTER_LIST */
bgp_check_cluster_list, NULL },
{ NULL, }, /* BA_DPA */
{ NULL, }, /* BA_ADVERTISER */
{ 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 },
{ NULL, }, /* BA_EXTENDED_COMM */
{ "as4_path", -1, BAF_OPTIONAL | BAF_TRANSITIVE, EAF_TYPE_OPAQUE, 1, /* BA_AS4_PATH */
bgp_check_as4_path, NULL },
{ "as4_aggregator", 8, BAF_OPTIONAL | BAF_TRANSITIVE, EAF_TYPE_OPAQUE, 1, /* BA_AS4_PATH */
NULL, NULL }
};
/* BA_AS4_PATH is type EAF_TYPE_OPAQUE and not type EAF_TYPE_AS_PATH because
* EAF_TYPE_AS_PATH is supposed to have different format (2 or 4 B for each ASN)
* depending on bgp_as4_support variable.
*/
#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, unsigned int 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.
*/
unsigned int
bgp_encode_attrs(struct bgp_proto *p, byte *w, ea_list *attrs, int remains)
{
unsigned int i, code, 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) && bgp_as4_support && (! 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);
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().
*/
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) && bgp_as4_support && (! 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 ... */
flags = a->flags & (BAF_OPTIONAL | BAF_TRANSITIVE | BAF_PARTIAL);
len = bgp_get_attr_len(a);
if (remains < len + 4)
goto err_no_buffer;
rv = bgp_encode_attr_hdr(w, flags, code, len);
ADVANCE(w, remains, rv);
switch (a->type & EAF_TYPE_MASK)
{
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:
{
u32 *z = (u32 *)a->u.ptr->data;
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:
log(L_ERR "BGP: attribute list too long, ignoring the remaining attributes");
return w - start;
}
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 void
bgp_normalize_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 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;
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 int
bgp_export_check(struct bgp_proto *p, ea_list *new)
{
eattr *a;
struct adata *d;
/* Check if next hop is valid */
a = ea_find(new, EA_CODE(EAP_BGP, BA_NEXT_HOP));
if (!a || ipa_equal(p->next_hop, *(ip_addr *)a->u.ptr))
{
DBG("\tInvalid NEXT_HOP\n");
return 0;
}
/* Check if we aren't forbidden to export the route by communities */
a = ea_find(new, 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 0;
}
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 0;
}
}
return 1;
}
static struct bgp_bucket *
bgp_get_bucket(struct bgp_proto *p, 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];
#ifdef LOCAL_DEBUG
{
byte buf[EA_FORMAT_BUF_SIZE];
ea_format(a, buf);
DBG("\t%s\n", buf);
}
#endif
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_set((u32 *) z->data, (u32 *) d->u.ptr->data, z->length / 4);
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", p->p.name, bgp_attr_table[bgp_mandatory_attrs[i]].name);
return NULL;
}
if (!bgp_export_check(p, new))
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);
}
void
bgp_rt_notify(struct proto *P, 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;
DBG("BGP: Got route %I/%d %s\n", n->n.prefix, n->n.pxlen, new ? "up" : "down");
if (new)
{
buck = bgp_get_bucket(p, attrs, new->attrs->source != RTS_BGP);
if (!buck) /* Inconsistent attribute list */
return;
}
else
{
if (!(buck = p->withdraw_bucket))
{
buck = p->withdraw_bucket = mb_alloc(P->pool, sizeof(struct bgp_bucket));
init_list(&buck->prefixes);
}
}
px = fib_get(&p->prefix_fib, &n->n.prefix, n->n.pxlen);
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, bgp_as4_support ? 6 : 4);
z[0] = AS_PATH_SEQUENCE;
z[1] = 1; /* 1 AS */
if (bgp_as4_support)
put_u32(z+2, p->local_as);
else
put_u16(z+2, p->local_as);
}
z = bgp_set_attr_wa(ea->attrs+2, pool, BA_NEXT_HOP, sizeof(ip_addr));
if (p->cf->next_hop_self ||
!p->is_internal ||
rta->dest != RTD_ROUTER)
{
if (ipa_nonzero(p->cf->source_addr))
*(ip_addr *)z = p->cf->source_addr;
else
*(ip_addr *)z = p->local_addr;
}
else
*(ip_addr *)z = e->attrs->gw;
bgp_set_attr(ea->attrs+3, BA_LOCAL_PREF, 0);
return 0; /* Leave decision to the filters */
}
static inline int
bgp_as_path_loopy(struct bgp_proto *p, rta *a)
{
eattr *e = ea_find(a->eattrs, EA_CODE(EAP_BGP, BA_AS_PATH));
return (e && as_path_is_member(e->u.ptr, p->local_as));
}
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_add(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);
}
a = ea_find(e->attrs->eattrs, EA_CODE(EAP_BGP, BA_NEXT_HOP));
if (a && (p->is_internal || (!p->is_internal && 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 */
bgp_attach_attr_ip(attrs, pool, BA_NEXT_HOP, p->local_addr);
}
if (rr)
{
/* Handling route reflection, RFC 4456 */
struct bgp_proto *src = (struct bgp_proto *) e->attrs->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 */
}
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->proto->proto == &proto_bgp) ? (struct bgp_proto *) e->attrs->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->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_last(e->u.ptr, &as))
return as;
else
return ((struct bgp_proto *) r->attrs->proto)->remote_as;
}
int
bgp_rte_better(rte *new, rte *old)
{
struct bgp_proto *new_bgp = (struct bgp_proto *) new->attrs->proto;
struct bgp_proto *old_bgp = (struct bgp_proto *) old->attrs->proto;
eattr *x, *y;
u32 n, o;
/* 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 */
if (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;
/* Skipping RFC 4271 9.1.2.2. e) */
/* We don't have interior distances */
/* 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. 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;
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);
}
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;
}
/* 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));
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)
log(L_WARN "BGP: AGGREGATOR attribute contain AS_TRANS, but AS4_AGGREGATOR is missing");
}
}
else
if (a4)
log(L_WARN "BGP: AS4_AGGREGATOR attribute received, but AGGREGATOR attribute is missing");
int p2_len = as_path_getlen(p2->u.ptr);
int p4_len = p4 ? as_path_getlen(p4->u.ptr) : AS_PATH_MAXLEN;
if (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 "BGP: Unexpected AS4_* attributes received");
}
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, unsigned int len, struct linpool *pool, int mandatory)
{
struct bgp_proto *bgp = conn->bgp;
rta *a = lp_alloc(pool, sizeof(struct rta));
unsigned int flags, code, l, i, type;
int errcode;
byte *z, *attr_start;
byte seen[256/8];
eattr *e;
ea_list *ea;
struct adata *ad;
a->proto = &bgp->p;
a->source = RTS_BGP;
a->scope = SCOPE_UNIVERSE;
a->cast = RTC_UNICAST;
a->dest = RTD_ROUTER;
a->flags = 0;
a->aflags = 0;
a->from = bgp->cf->remote_ip;
a->eattrs = NULL;
/* 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 < 0)
continue;
}
type = desc->type;
}
else /* Unknown attribute */
{
if (!(flags & BAF_OPTIONAL))
{ errcode = 2; goto err; }
type = EAF_TYPE_OPAQUE;
}
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:
{
u32 *z = (u32 *) ad->data;
for(i=0; i<ad->length/4; i++)
z[i] = ntohl(z[i]);
break;
}
}
}
#ifdef IPV6
if (seen[BA_MP_REACH_NLRI / 8] & (1 << (BA_MP_REACH_NLRI % 8)))
mandatory = 1;
#endif
/* Check if all mandatory attributes are present */
if (mandatory)
{
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_support && (! bgp->as4_session))
bgp_reconstruct_4b_atts(bgp, a, pool);
if (bgp_as4_support)
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 loop;
/* Two checks for IBGP loops caused by route reflection, RFC 4456 */
if (bgp_originator_id_loopy(bgp, a) ||
bgp_cluster_list_loopy(bgp, a))
goto loop;
/* If there's no local preference, define one */
if (!(seen[0] & (1 << BA_LOCAL_PREF)))
bgp_attach_attr(&a->eattrs, pool, BA_LOCAL_PREF, 0);
return a;
loop:
DBG("BGP: Path loop!\n");
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)
{
unsigned int i = EA_ID(a->id);
struct attr_desc *d;
if (ATTR_KNOWN(i))
{
d = &bgp_attr_table[i];
buf += bsprintf(buf, "%s", d->name);
if (d->format)
{
*buf++ = ':';
*buf++ = ' ';
d->format(a, buf);
return GA_FULL;
}
return GA_NAME;
}
bsprintf(buf, "%02x%s", i, (a->flags & BAF_TRANSITIVE) ? " [t]" : "");
return GA_NAME;
}
void
bgp_attr_init(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 (p && as_path_get_first(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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