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bird/proto/bgp/attrs.c

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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.
*/
#define LOCAL_DEBUG
#include "nest/bird.h"
#include "nest/iface.h"
#include "nest/protocol.h"
#include "nest/route.h"
#include "conf/conf.h"
#include "lib/resource.h"
#include "lib/string.h"
#include "lib/unaligned.h"
#include "bgp.h"
static int bgp_mandatory_attrs[] = { BA_ORIGIN, BA_AS_PATH, BA_NEXT_HOP };
struct bgp_bucket {
struct bgp_bucket *next;
unsigned hash;
ea_list eattrs[0];
};
struct attr_desc {
char *name; /* FIXME: Use the same names as in filters */
int expected_length;
int expected_flags;
int type;
int (*validate)(struct bgp_proto *p, byte *attr, int len);
void (*format)(eattr *ea, byte *buf);
};
extern struct attr_desc bgp_attr_table[];
static void
bgp_normalize_set(u32 *dest, u32 *src, unsigned cnt)
{
memcpy(dest, src, sizeof(u32) * cnt);
/* FIXME */
}
static void
bgp_rehash_buckets(struct bgp_proto *p)
{
struct bgp_bucket **old = p->bucket_table;
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_table = 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->next;
e = b->hash & mask;
b->next = new[e];
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 = 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 += 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->next = p->bucket_table[index];
p->bucket_table[index] = b;
b->hash = hash;
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 = &new->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 += ALIGN(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, ea_list *old, ea_list *tmp)
{
ea_list *t, *new;
unsigned i, cnt;
eattr *a, *d;
u32 seen = 0;
unsigned hash;
struct bgp_bucket *b;
/* Merge the attribute lists */
for(t=tmp; t->next; t=t->next)
;
t->next = old;
new = alloca(ea_scan(tmp));
ea_merge(tmp, new);
t->next = NULL;
ea_sort(tmp);
/* 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[256];
ea_format(a, buf);
DBG("\t%s\n", buf);
}
#endif
if (EA_PROTO(a->id) != EAP_BGP)
continue;
if (EA_ID(a->id) < 32)
seen |= 1 << EA_ID(a->id);
*d = *a;
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_table[hash & (p->hash_size - 1)]; b; b=b->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;
}
/* Create new bucket */
DBG("Creating bucket.\n");
return bgp_new_bucket(p, new, hash);
}
void
bgp_rt_notify(struct proto *P, net *n, rte *new, rte *old, ea_list *tmpa)
{
struct bgp_proto *p = (struct bgp_proto *) P;
DBG("BGP: Got route %I/%d\n", n->n.prefix, n->n.pxlen);
if (new)
{
struct bgp_bucket *buck = bgp_get_bucket(p, new->attrs->eattrs, tmpa);
if (!buck) /* Inconsistent attribute list */
return;
}
/* FIXME: Normalize attributes */
/* FIXME: Check next hop */
}
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) + 3*sizeof(eattr));
eattr *a = ea->attrs;
rta *rta = e->attrs;
ea->next = *attrs;
*attrs = ea;
ea->flags = EALF_SORTED;
ea->count = 3;
a->id = EA_CODE(EAP_BGP, BA_ORIGIN);
a->flags = BAF_TRANSITIVE;
a->type = EAF_TYPE_INT;
if (rta->source == RTS_RIP_EXT || rta->source == RTS_OSPF_EXT)
a->u.data = 2; /* Incomplete */
else
a->u.data = 0; /* IGP */
a++;
a->id = EA_CODE(EAP_BGP, BA_AS_PATH);
a->flags = BAF_TRANSITIVE;
a->type = EAF_TYPE_AS_PATH;
if (p->is_internal)
{
a->u.ptr = lp_alloc(pool, sizeof(struct adata));
a->u.ptr->length = 0;
}
else
{
byte *z;
a->u.ptr = lp_alloc(pool, sizeof(struct adata) + 4);
a->u.ptr->length = 4;
z = a->u.ptr->data;
z[0] = 2; /* AS_SEQUENCE */
z[1] = 1; /* 1 AS */
put_u16(z+2, p->local_as);
}
a++;
a->id = EA_CODE(EAP_BGP, BA_NEXT_HOP);
a->flags = BAF_TRANSITIVE;
a->type = EAF_TYPE_IP_ADDRESS;
a->u.ptr = lp_alloc(pool, sizeof(struct adata) + sizeof(ip_addr));
a->u.ptr->length = sizeof(ip_addr);
if (p->cf->next_hop_self ||
!p->is_internal ||
rta->dest != RTD_ROUTER)
*(ip_addr *)a->u.ptr->data = p->local_addr;
else
*(ip_addr *)a->u.ptr->data = e->attrs->gw;
return 0; /* Leave decision to the filters */
}
ea_list *
bgp_path_prepend(struct linpool *pool, eattr *a, ea_list *old, int as)
{
struct ea_list *e = lp_alloc(pool, sizeof(ea_list) + sizeof(eattr));
struct adata *olda = a->u.ptr;
struct adata *newa;
e->next = old;
e->flags = EALF_SORTED;
e->count = 1;
e->attrs[0].id = EA_CODE(EAP_BGP, BA_AS_PATH);
e->attrs[0].flags = BAF_TRANSITIVE;
e->attrs[0].type = EAF_TYPE_AS_PATH;
if (olda->length && olda->data[0] == 2 && olda->data[1] < 255) /* Starting with sequence => just prepend the AS number */
{
newa = lp_alloc(pool, sizeof(struct adata) + olda->length + 2);
newa->length = olda->length + 2;
newa->data[0] = 2;
newa->data[1] = olda->data[1] + 1;
memcpy(newa->data+4, olda->data+2, olda->length-2);
}
else /* Create new path segment */
{
newa = lp_alloc(pool, sizeof(struct adata) + olda->length + 4);
newa->length = olda->length + 4;
newa->data[0] = 2;
newa->data[1] = 1;
memcpy(newa->data+4, olda->data, olda->length);
}
put_u16(newa->data+2, as);
e->attrs[0].u.ptr = newa;
return e;
}
static int
bgp_update_attrs(struct bgp_proto *p, rte *e, ea_list **attrs, struct linpool *pool)
{
eattr *a;
if (!p->is_internal)
*attrs = bgp_path_prepend(pool, ea_find(e->attrs->eattrs, EA_CODE(EAP_BGP, BA_AS_PATH)), *attrs, p->local_as);
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 */
ea_list *ea = lp_alloc(pool, sizeof(ea_list) + sizeof(eattr));
ea->next = *attrs;
*attrs = ea;
ea->flags = EALF_SORTED;
ea->count = 1;
a = ea->attrs;
a->id = EA_CODE(EAP_BGP, BA_NEXT_HOP);
a->flags = BAF_TRANSITIVE;
a->type = EAF_TYPE_IP_ADDRESS;
a->u.ptr = lp_alloc(pool, sizeof(struct adata) + sizeof(ip_addr));
a->u.ptr->length = sizeof(ip_addr);
*(ip_addr *)a->u.ptr->data = p->local_addr;
}
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)
{
if (p->local_as == new_bgp->local_as && p->is_internal && new_bgp->is_internal)
return -1; /* Don't redistribute internal routes with IBGP */
return bgp_update_attrs(p, e, attrs, pool);
}
else
return bgp_create_attrs(p, e, attrs, pool);
}
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 *new_lpref = ea_find(new->attrs->eattrs, EA_CODE(EAP_BGP, BA_LOCAL_PREF));
eattr *old_lpref = ea_find(old->attrs->eattrs, EA_CODE(EAP_BGP, BA_LOCAL_PREF));
/* Start with local preferences */
if (new_lpref && old_lpref) /* Somebody might have undefined them */
{
if (new_lpref->u.data > old_lpref->u.data)
return 1;
if (new_lpref->u.data < old_lpref->u.data)
return 0;
}
/* A tie breaking procedure according to RFC 1771, section 9.1.2.1 */
/* FIXME: Look at MULTI_EXIT_DISC, take the lowest */
/* We don't have interior distances */
/* We 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;
/* Finally we compare BGP identifiers */
return (new_bgp->remote_id < old_bgp->remote_id);
}
static int
bgp_local_pref(struct bgp_proto *p, rta *a)
{
return 0; /* FIXME (should be compatible with Cisco defaults?) */
}
static int
bgp_path_loopy(struct bgp_proto *p, eattr *a)
{
byte *path = a->u.ptr->data;
int len = a->u.ptr->length;
int i, n;
while (len > 0)
{
n = path[1];
len -= 2 - 2*n;
path += 2;
for(i=0; i<n; i++)
{
if (get_u16(path) == p->local_as)
return 1;
path += 2;
}
}
return 0;
}
static int
bgp_check_origin(struct bgp_proto *p, byte *a, 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(struct bgp_proto *p, byte *a, int len)
{
while (len)
{
DBG("Path segment %02x %02x\n", a[0], a[1]);
if (len < 2 ||
a[0] != BGP_PATH_AS_SET && a[0] != BGP_PATH_AS_SEQUENCE ||
2*a[1] + 2 > len)
return 11;
len -= 2*a[1] + 2;
a += 2*a[1] + 2;
}
return 0;
}
static int
bgp_check_next_hop(struct bgp_proto *p, byte *a, int len)
{
ip_addr addr;
memcpy(&addr, a, len);
if (ipa_classify(ipa_ntoh(addr)) & IADDR_HOST)
return 0;
else
return 8;
}
static int
bgp_check_local_pref(struct bgp_proto *p, byte *a, int len)
{
if (!p->is_internal) /* Ignore local preference from EBGP connections */
return -1;
return 0;
}
static struct attr_desc bgp_attr_table[] = {
{ NULL, -1, 0, 0, /* Undefined */
NULL, NULL },
{ "origin", 1, BAF_TRANSITIVE, EAF_TYPE_INT, /* BA_ORIGIN */
bgp_check_origin, bgp_format_origin },
{ "as_path", -1, BAF_TRANSITIVE, EAF_TYPE_AS_PATH, /* BA_AS_PATH */
bgp_check_path, NULL },
{ "next_hop", 4, BAF_TRANSITIVE, EAF_TYPE_IP_ADDRESS, /* BA_NEXT_HOP */
bgp_check_next_hop, NULL },
{ "MED", 4, BAF_OPTIONAL, EAF_TYPE_INT, /* BA_MULTI_EXIT_DISC */
NULL, NULL },
{ "local_pref", 4, BAF_OPTIONAL, EAF_TYPE_INT, /* BA_LOCAL_PREF */
bgp_check_local_pref, NULL },
{ "atomic_aggr", 0, BAF_OPTIONAL, EAF_TYPE_OPAQUE, /* BA_ATOMIC_AGGR */
NULL, NULL },
{ "aggregator", 6, BAF_OPTIONAL, EAF_TYPE_OPAQUE, /* BA_AGGREGATOR */
NULL, NULL },
#if 0
/* FIXME: Handle community lists and remember to convert their endianity and normalize them */
{ 0, 0 }, /* BA_COMMUNITY */
{ 0, 0 }, /* BA_ORIGINATOR_ID */
{ 0, 0 }, /* BA_CLUSTER_LIST */
#endif
};
struct rta *
bgp_decode_attrs(struct bgp_conn *conn, byte *attr, unsigned int len, struct linpool *pool)
{
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;
neighbor *neigh;
ip_addr nexthop;
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 (code && code < sizeof(bgp_attr_table)/sizeof(bgp_attr_table[0]))
{
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->validate)
{
errcode = desc->validate(bgp, z, l);
if (errcode > 0)
goto err;
if (errcode < 0)
continue;
}
type = desc->type;
}
else /* Unknown attribute */
{ /* FIXME: Send partial bit when forwarding */
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:
*(ip_addr *)ad->data = ipa_ntoh(*(ip_addr *)ad->data);
break;
}
}
/* Check if all mandatory attributes are present */
for(i=0; i < sizeof(bgp_mandatory_attrs)/sizeof(bgp_mandatory_attrs[0]); i++)
{
code = bgp_mandatory_attrs[i];
if (!(seen[code/8] & (1 << (code%8))))
{
bgp_error(conn, 3, 3, code, 1);
return NULL;
}
}
/* Assign local preference if none defined */
if (!(seen[BA_LOCAL_PREF/8] & (1 << (BA_LOCAL_PREF%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, BA_LOCAL_PREF);
ea->attrs[0].flags = BAF_OPTIONAL;
ea->attrs[0].type = EAF_TYPE_INT;
ea->attrs[0].u.data = bgp_local_pref(bgp, a);
}
/* If the AS path attribute contains our AS, reject the routes */
e = ea_find(a->eattrs, EA_CODE(EAP_BGP, BA_AS_PATH));
ASSERT(e);
if (bgp_path_loopy(bgp, e))
return NULL;
/* Fill in the remaining rta fields */
e = ea_find(a->eattrs, EA_CODE(EAP_BGP, BA_NEXT_HOP));
ASSERT(e);
nexthop = *(ip_addr *) e->u.ptr->data;
if (ipa_equal(nexthop, bgp->local_addr))
{
DBG("BGP: Loop!\n"); /* FIXME */
return NULL;
}
neigh = neigh_find(&bgp->p, &nexthop, 0) ? : bgp->neigh;
a->gw = neigh->addr;
a->iface = neigh->iface;
return rta_lookup(a);
malformed:
bgp_error(conn, 3, 1, len, 0);
return NULL;
err:
bgp_error(conn, 3, errcode, code, 0); /* FIXME: Return attribute data! */
return NULL;
}
int
bgp_get_attr(eattr *a, byte *buf)
{
unsigned int i = EA_ID(a->id);
struct attr_desc *d;
if (i && i < sizeof(bgp_attr_table)/sizeof(bgp_attr_table[0]))
{
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_table = mb_allocz(p->p.pool, p->hash_size * sizeof(struct bgp_bucket *));
}
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