/* * BIRD -- BGP Attributes * * (c) 2000 Martin Mares * * 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" void bgp_rt_notify(struct proto *P, net *n, rte *new, rte *old, ea_list *tmpa) { DBG("BGP: Got route %I/%d\n", n->n.prefix, n->n.pxlen); /* FIXME: Normalize attributes */ /* FIXME: Check next hop */ /* FIXME: Someone might have undefined the mandatory attributes */ } 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->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->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; ilocal_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; } 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); }; 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 }; 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, 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; }