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Parsing of BGP attributes.

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This commit is contained in:
Martin Mares 2000-03-31 23:21:37 +00:00
parent 08732b7178
commit c00d31befa
5 changed files with 254 additions and 23 deletions
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210
proto/bgp/attrs.c
View file

@ -6,10 +6,220 @@
* 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_check_origin(byte *a, int len)
{
if (len > 2)
return 6;
return 0;
}
static int bgp_check_path(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(byte *a, int len)
{
ip_addr addr;
memcpy(&addr, a, len);
if (ipa_classify(ipa_ntoh(addr)) & IADDR_HOST)
return 0;
else
return 8;
}
struct attr_desc {
int expected_length;
int expected_flags;
int type;
int (*validate)(byte *attr, int len);
};
static struct attr_desc bgp_attr_table[] = {
{ -1, 0, 0, NULL }, /* Undefined */
{ 1, BAF_TRANSITIVE, EAF_TYPE_INT, bgp_check_origin }, /* BA_ORIGIN */
{ -1, BAF_TRANSITIVE, EAF_TYPE_AS_PATH, bgp_check_path }, /* BA_AS_PATH */
{ 4, BAF_TRANSITIVE, EAF_TYPE_IP_ADDRESS, bgp_check_next_hop }, /* BA_NEXT_HOP */
{ 4, BAF_OPTIONAL, EAF_TYPE_INT, NULL }, /* BA_MULTI_EXIT_DISC */
{ 4, BAF_OPTIONAL, EAF_TYPE_INT, NULL }, /* BA_LOCAL_PREF */
{ 0, BAF_OPTIONAL, EAF_TYPE_OPAQUE, NULL }, /* BA_ATOMIC_AGGR */
{ 6, BAF_OPTIONAL, EAF_TYPE_OPAQUE, NULL }, /* BA_AGGREGATOR */
#if 0
/* FIXME: Handle community lists */
{ 0, 0 }, /* BA_COMMUNITY */
{ 0, 0 }, /* BA_ORIGINATOR_ID */
{ 0, 0 }, /* BA_CLUSTER_LIST */
#endif
};
static int bgp_mandatory_attrs[] = { BA_ORIGIN, BA_AS_PATH, BA_NEXT_HOP };
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, errcode, i, type;
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;
seen[code/8] |= (1 << (code%8));
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(z, l)))
goto err;
type = desc->type;
}
else /* Unknown attribute */
{ /* FIXME: Send partial bit when forwarding */
if (!(flags & BAF_OPTIONAL))
{ errcode = 2; goto err; }
type = EAF_TYPE_OPAQUE;
}
ea = lp_alloc(pool, sizeof(struct ea_list) + sizeof(struct 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:
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;
}
}
/* 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;
neigh = neigh_find(&bgp->p, &nexthop, 0);
if (!neigh)
{
if (bgp->cf->multihop)
neigh = neigh_find(&bgp->p, &bgp->cf->multihop_via, 0);
else
neigh = neigh_find(&bgp->p, &bgp->cf->remote_ip, 0);
}
if (!neigh || !neigh->iface)
{
DBG("BGP: No route to peer!\n"); /* FIXME */
return NULL;
}
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;
}

2
proto/bgp/bgp.c
View file

@ -96,6 +96,8 @@ bgp_close_conn(struct bgp_conn *conn)
{
bgp_close(p);
p->conn = NULL;
if (conn->error_flag) /* FIXME: Enable automatically? */
p->p.disabled = 1;
proto_notify_state(&p->p, PS_DOWN);
}
}

10
proto/bgp/bgp.h
View file

@ -9,11 +9,14 @@
#ifndef _BIRD_BGP_H_
#define _BIRD_BGP_H_
struct linpool;
struct bgp_config {
struct proto_config c;
unsigned int local_as, remote_as;
ip_addr remote_ip;
int multihop; /* Number of hops if multihop */
ip_addr multihop_via; /* Multihop: address to route to */
unsigned connect_retry_time;
unsigned hold_time, initial_hold_time;
unsigned keepalive_time;
@ -63,6 +66,8 @@ void bgp_close_conn(struct bgp_conn *c);
/* attrs.c */
struct rta *bgp_decode_attrs(struct bgp_conn *conn, byte *a, unsigned int len, struct linpool *pool);
/* packets.c */
void bgp_schedule_packet(struct bgp_conn *conn, int type);
@ -88,7 +93,7 @@ int bgp_rx(struct birdsock *sk, int size);
#define BA_AS_PATH 0x02 /* WM */
#define BA_NEXT_HOP 0x03 /* WM */
#define BA_MULTI_EXIT_DISC 0x04 /* ON */
#define BA_LOCAL_PREF 0x05 /* WM */
#define BA_LOCAL_PREF 0x05 /* WD */
#define BA_ATOMIC_AGGR 0x06 /* WD */
#define BA_AGGREGATOR 0x07 /* OT */
#define BA_COMMUNITY 0x08 /* [RFC1997] */ /* OT */
@ -102,6 +107,9 @@ int bgp_rx(struct birdsock *sk, int size);
#define BA_MP_UNREACH_NLRI 0x0f
#define BA_EXTENDED_COMM 0x10 /* draft-ramachandra-bgp-ext-communities */
#define BGP_PATH_AS_SET 1 /* Types of path segments */
#define BGP_PATH_AS_SEQUENCE 2
/* BGP states */
#define BS_IDLE 0

4
proto/bgp/config.Y
View file

@ -15,7 +15,7 @@ CF_HDR
CF_DECLS
CF_KEYWORDS(BGP, LOCAL, NEIGHBOR, AS, HOLD, TIME, CONNECT, RETRY, KEEPALIVE,
MULTIHOP, STARTUP)
MULTIHOP, STARTUP, VIA)
CF_GRAMMAR
@ -46,7 +46,7 @@ bgp_proto:
| bgp_proto STARTUP HOLD TIME NUM ';' { BGP_CFG->initial_hold_time = $5; }
| bgp_proto CONNECT RETRY TIME NUM ';' { BGP_CFG->connect_retry_time = $5; }
| bgp_proto KEEPALIVE TIME NUM ';' { BGP_CFG->connect_retry_time = $4; }
| bgp_proto MULTIHOP NUM ';' { BGP_CFG->multihop = $3; }
| bgp_proto MULTIHOP NUM VIA IPA ';' { BGP_CFG->multihop = $3; BGP_CFG->multihop_via = $5; }
;
CF_CODE

51
proto/bgp/packets.c
View file

@ -218,24 +218,26 @@ bgp_rx_open(struct bgp_conn *conn, byte *pkt, int len)
#define DECODE_PREFIX(pp, ll) do { \
int b = *pp++; \
int q; \
ip_addr temp; \
ll--; \
if (b > BITS_PER_IP_ADDRESS) { bgp_error(conn, 3, 10, b, 0); return; } \
q = (b+7) / 8; \
if (ll < q) goto too_small; \
memcpy(&temp, pp, q); \
if (ll < q) goto malformed; \
memcpy(&prefix, pp, q); \
pp += q; \
ll -= q; \
n.n.prefix = ipa_and(ipa_ntoh(temp), ipa_mkmask(b)); \
n.n.pxlen = b; \
prefix = ipa_and(ipa_ntoh(prefix), ipa_mkmask(b)); \
pxlen = b; \
} while (0)
/* FIXME: Check validity of prefixes */
static void
bgp_rx_update(struct bgp_conn *conn, byte *pkt, int len)
{
struct bgp_proto *bgp = conn->bgp;
byte *withdrawn, *attrs, *nlri;
int withdrawn_len, attr_len, nlri_len;
net n;
ip_addr prefix;
int withdrawn_len, attr_len, nlri_len, pxlen;
net *n;
rte e;
DBG("BGP: UPDATE\n");
@ -246,45 +248,54 @@ bgp_rx_update(struct bgp_conn *conn, byte *pkt, int len)
/* Find parts of the packet and check sizes */
if (len < 23)
{
too_small:
bgp_error(conn, 1, 2, len, 2);
return;
}
withdrawn = pkt + 21;
withdrawn_len = get_u16(pkt + 19);
if (withdrawn_len + 23 > len)
goto too_small;
{
malformed:
bgp_error(conn, 3, 1, len, 0);
return;
}
attrs = withdrawn + withdrawn_len + 2;
attr_len = get_u16(attrs - 2);
if (withdrawn_len + attr_len + 23 > len)
goto too_small;
goto malformed;
nlri = attrs + attr_len;
nlri_len = len - withdrawn_len - attr_len - 23;
if (!attr_len && nlri_len)
goto too_small;
goto malformed;
DBG("Sizes: withdrawn=%d, attrs=%d, NLRI=%d\n", withdrawn_len, attr_len, nlri_len);
/* Withdraw routes */
while (withdrawn_len)
{
DECODE_PREFIX(withdrawn, withdrawn_len);
DBG("Withdraw %I/%d\n", n.n.prefix, n.n.pxlen);
DBG("Withdraw %I/%d\n", prefix, pxlen);
if (n = net_find(bgp->p.table, prefix, pxlen))
rte_update(bgp->p.table, n, &bgp->p, NULL);
}
if (nlri_len)
{
#if 0
rta *a = bgp_decode_attrs(conn, attrs, attr_len, bgp_linpool);
if (a)
#endif
if (!a)
return;
while (nlri_len)
{
while (nlri_len)
{
DECODE_PREFIX(nlri, nlri_len);
DBG("Add %I/%d\n", n.n.prefix, n.n.pxlen);
}
rte *e;
DECODE_PREFIX(nlri, nlri_len); /* FIXME: Uncache rta ! */
DBG("Add %I/%d\n", prefix, pxlen);
e = rte_get_temp(a);
n = net_get(bgp->p.table, prefix, pxlen);
e->net = n;
e->pflags = 0;
rte_update(bgp->p.table, n, &bgp->p, e);
}
lp_flush(bgp_linpool);
rta_free(a);
}
}