/* * BIRD -- BGP Attributes * * (c) 2000 Martin Mares * (c) 2008--2016 Ondrej Zajicek * (c) 2008--2016 CZ.NIC z.s.p.o. * * Can be freely distributed and used under the terms of the GNU GPL. */ #undef LOCAL_DEBUG #include #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 * * Loop detection based on AS_PATH causes updates to be withdrawn.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 * * Loop detection related to route reflection (based on ORIGINATOR_ID * and CLUSTER_LIST) causes updates to be withdrawn.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. * * BGP attribute table has several hooks: * * export - Hook that validates and normalizes attribute during export phase. * Receives eattr, may modify it (e.g., sort community lists for canonical * representation), UNSET() it (e.g., skip empty lists), or WITHDRAW() it if * necessary. May assume that eattr has value valid w.r.t. its type, but may be * invalid w.r.t. BGP constraints. Optional. * * encode - Hook that converts internal representation to external one during * packet writing. Receives eattr and puts it in the buffer (including attribute * header). Returns number of bytes, or -1 if not enough space. May assume that * eattr has value valid w.r.t. its type and validated by export hook. Mandatory * for all known attributes that exist internally after export phase (i.e., all * except pseudoattributes MP_(UN)REACH_NLRI). * * decode - Hook that converts external representation to internal one during * packet parsing. Receives attribute data in buffer, validates it and adds * attribute to ea_list. If data are invalid, steps DISCARD(), WITHDRAW() or * bgp_parse_error() may be used to escape. Mandatory for all known attributes. * * format - Optional hook that converts eattr to textual representation. */ struct bgp_attr_desc { const char *name; uint type; uint flags; void (*export)(struct bgp_export_state *s, eattr *a); int (*encode)(struct bgp_write_state *s, eattr *a, byte *buf, uint size); void (*decode)(struct bgp_parse_state *s, uint code, uint flags, byte *data, uint len, ea_list **to); void (*format)(eattr *ea, byte *buf, uint size); }; static const struct bgp_attr_desc bgp_attr_table[]; static inline int bgp_attr_known(uint code); eattr * bgp_set_attr(ea_list **attrs, struct linpool *pool, uint code, uint flags, uintptr_t val) { ASSERT(bgp_attr_known(code)); ea_list *a = lp_alloc(pool, sizeof(ea_list) + sizeof(eattr)); eattr *e = &a->attrs[0]; a->flags = EALF_SORTED; a->count = 1; a->next = *attrs; *attrs = a; e->id = EA_CODE(EAP_BGP, code); e->type = bgp_attr_table[code].type; e->flags = flags; if (e->type & EAF_EMBEDDED) e->u.data = (u32) val; else e->u.ptr = (struct adata *) val; return e; } #define REPORT(msg, args...) \ ({ log(L_REMOTE "%s: " msg, s->proto->p.name, ## args); }) #define DISCARD(msg, args...) \ ({ REPORT(msg, ## args); return; }) #define WITHDRAW(msg, args...) \ ({ REPORT(msg, ## args); s->err_withdraw = 1; return; }) #define UNSET(a) \ ({ a->type = EAF_TYPE_UNDEF; return; }) #define NEW_BGP "Discarding %s attribute received from AS4-aware neighbor" #define BAD_EBGP "Discarding %s attribute received from EBGP neighbor" #define BAD_LENGTH "Malformed %s attribute - invalid length (%u)" #define BAD_VALUE "Malformed %s attribute - invalid value (%u)" #define NO_MANDATORY "Missing mandatory %s attribute" static inline int bgp_put_attr_hdr3(byte *buf, uint code, uint flags, uint len) { *buf++ = flags; *buf++ = code; *buf++ = len; return 3; } static inline int bgp_put_attr_hdr4(byte *buf, uint code, uint flags, uint len) { *buf++ = flags | BAF_EXT_LEN; *buf++ = code; put_u16(buf, len); return 4; } static inline int bgp_put_attr_hdr(byte *buf, uint code, uint flags, uint len) { if (len < 256) return bgp_put_attr_hdr3(buf, code, flags, len); else return bgp_put_attr_hdr4(buf, code, flags, len); } static int bgp_encode_u8(struct bgp_write_state *s UNUSED, eattr *a, byte *buf, uint size) { if (size < (3+1)) return -1; bgp_put_attr_hdr3(buf, EA_ID(a->id), a->flags, 1); buf[3] = a->u.data; return 3+1; } static int bgp_encode_u32(struct bgp_write_state *s UNUSED, eattr *a, byte *buf, uint size) { if (size < (3+4)) return -1; bgp_put_attr_hdr3(buf, EA_ID(a->id), a->flags, 4); put_u32(buf+3, a->u.data); return 3+4; } static int bgp_encode_u32s(struct bgp_write_state *s UNUSED, eattr *a, byte *buf, uint size) { uint len = a->u.ptr->length; if (size < (4+len)) return -1; uint hdr = bgp_put_attr_hdr(buf, EA_ID(a->id), a->flags, len); put_u32s(buf + hdr, (u32 *) a->u.ptr->data, len / 4); return hdr + len; } static int bgp_put_attr(byte *buf, uint size, uint code, uint flags, byte *data, uint len) { if (size < (4+len)) return -1; uint hdr = bgp_put_attr_hdr(buf, code, flags, len); memcpy(buf + hdr, data, len); return hdr + len; } static int bgp_encode_raw(struct bgp_write_state *s UNUSED, eattr *a, byte *buf, uint size) { return bgp_put_attr(buf, size, EA_ID(a->id), a->flags, a->u.ptr->data, a->u.ptr->length); } /* * Attribute hooks */ static void bgp_export_origin(struct bgp_export_state *s, eattr *a) { if (a->u.data > 2) WITHDRAW(BAD_VALUE, "ORIGIN", a->u.data); } static void bgp_decode_origin(struct bgp_parse_state *s, uint code UNUSED, uint flags, byte *data, uint len, ea_list **to) { if (len != 1) WITHDRAW(BAD_LENGTH, "ORIGIN", len); if (data[0] > 2) WITHDRAW(BAD_VALUE, "ORIGIN", data[0]); bgp_set_attr_u32(to, s->pool, BA_ORIGIN, flags, data[0]); } static void bgp_format_origin(eattr *a, byte *buf, uint size UNUSED) { static const char *bgp_origin_names[] = { "IGP", "EGP", "Incomplete" }; bsprintf(buf, (a->u.data <= 2) ? bgp_origin_names[a->u.data] : "?"); } static int bgp_encode_as_path(struct bgp_write_state *s, eattr *a, byte *buf, uint size) { byte *data = a->u.ptr->data; uint len = a->u.ptr->length; if (!s->as4_session) { /* Prepare 16-bit AS_PATH (from 32-bit one) in a temporary buffer */ byte *src = data; data = alloca(len); len = as_path_32to16(data, src, len); } return bgp_put_attr(buf, size, BA_AS_PATH, a->flags, data, len); } static void bgp_decode_as_path(struct bgp_parse_state *s, uint code UNUSED, uint flags, byte *data, uint len, ea_list **to) { struct bgp_proto *p = s->proto; int as_length = s->as4_session ? 4 : 2; int as_confed = p->cf->confederation && p->is_interior; char err[128]; if (!as_path_valid(data, len, as_length, as_confed, err, sizeof(err))) WITHDRAW("Malformed AS_PATH attribute - %s", err); /* In some circumstances check for initial AS_CONFED_SEQUENCE; RFC 5065 5.0 */ if (p->is_interior && !p->is_internal && ((len < 2) || (data[0] != AS_PATH_CONFED_SEQUENCE))) WITHDRAW("Malformed AS_PATH attribute - %s", "missing initial AS_CONFED_SEQUENCE"); if (!s->as4_session) { /* Prepare 32-bit AS_PATH (from 16-bit one) in a temporary buffer */ byte *src = data; data = alloca(2*len); len = as_path_16to32(data, src, len); } bgp_set_attr_data(to, s->pool, BA_AS_PATH, flags, data, len); } static int bgp_encode_next_hop(struct bgp_write_state *s, eattr *a, byte *buf, uint size) { /* * The NEXT_HOP attribute is used only in traditional (IPv4) BGP. In MP-BGP, * the next hop is encoded as a part of the MP_REACH_NLRI attribute, so we * store it and encode it later by AFI-specific hooks. */ if ((s->channel->afi == BGP_AF_IPV4) && !s->channel->ext_next_hop) { ASSERT(a->u.ptr->length == sizeof(ip_addr)); if (size < (3+4)) return -1; bgp_put_attr_hdr3(buf, BA_NEXT_HOP, a->flags, 4); put_ip4(buf+3, ipa_to_ip4( *(ip_addr *) a->u.ptr->data )); return 3+4; } else { s->mp_next_hop = a; return 0; } } static void bgp_decode_next_hop(struct bgp_parse_state *s, uint code UNUSED, uint flags UNUSED, byte *data, uint len, ea_list **to UNUSED) { if (len != 4) WITHDRAW(BAD_LENGTH, "NEXT_HOP", len); /* Semantic checks are done later */ s->ip_next_hop_len = len; s->ip_next_hop_data = data; } /* TODO: This function should use AF-specific hook */ static void bgp_format_next_hop(eattr *a, byte *buf, uint size UNUSED) { ip_addr *nh = (void *) a->u.ptr->data; uint len = a->u.ptr->length; ASSERT((len == 16) || (len == 32)); /* in IPv6, we may have two addresses in NEXT HOP */ if ((len == 16) || ipa_zero(nh[1])) bsprintf(buf, "%I", nh[0]); else bsprintf(buf, "%I %I", nh[0], nh[1]); } static void bgp_decode_med(struct bgp_parse_state *s, uint code UNUSED, uint flags, byte *data, uint len, ea_list **to) { if (len != 4) WITHDRAW(BAD_LENGTH, "MULTI_EXIT_DISC", len); u32 val = get_u32(data); bgp_set_attr_u32(to, s->pool, BA_MULTI_EXIT_DISC, flags, val); } static void bgp_export_local_pref(struct bgp_export_state *s, eattr *a) { if (!s->proto->is_interior && !s->proto->cf->allow_local_pref) UNSET(a); } static void bgp_decode_local_pref(struct bgp_parse_state *s, uint code UNUSED, uint flags, byte *data, uint len, ea_list **to) { if (!s->proto->is_interior && !s->proto->cf->allow_local_pref) DISCARD(BAD_EBGP, "LOCAL_PREF"); if (len != 4) WITHDRAW(BAD_LENGTH, "LOCAL_PREF", len); u32 val = get_u32(data); bgp_set_attr_u32(to, s->pool, BA_LOCAL_PREF, flags, val); } static void bgp_decode_atomic_aggr(struct bgp_parse_state *s, uint code UNUSED, uint flags, byte *data UNUSED, uint len, ea_list **to) { if (len != 0) DISCARD(BAD_LENGTH, "ATOMIC_AGGR", len); bgp_set_attr_data(to, s->pool, BA_ATOMIC_AGGR, flags, NULL, 0); } static int bgp_encode_aggregator(struct bgp_write_state *s, eattr *a, byte *buf, uint size) { byte *data = a->u.ptr->data; uint len = a->u.ptr->length; if (!s->as4_session) { /* Prepare 16-bit AGGREGATOR (from 32-bit one) in a temporary buffer */ byte *src = data; data = alloca(6); len = aggregator_32to16(data, src); } return bgp_put_attr(buf, size, BA_AGGREGATOR, a->flags, data, len); } static void bgp_decode_aggregator(struct bgp_parse_state *s, uint code UNUSED, uint flags, byte *data, uint len, ea_list **to) { if (len != (s->as4_session ? 8 : 6)) DISCARD(BAD_LENGTH, "AGGREGATOR", len); if (!s->as4_session) { /* Prepare 32-bit AGGREGATOR (from 16-bit one) in a temporary buffer */ byte *src = data; data = alloca(8); len = aggregator_16to32(data, src); } bgp_set_attr_data(to, s->pool, BA_AGGREGATOR, flags, data, len); } static void bgp_format_aggregator(eattr *a, byte *buf, uint size UNUSED) { byte *data = a->u.ptr->data; bsprintf(buf, "%I4 AS%u", get_ip4(data+4), get_u32(data+0)); } static void bgp_export_community(struct bgp_export_state *s, eattr *a) { if (a->u.ptr->length == 0) UNSET(a); a->u.ptr = int_set_sort(s->pool, a->u.ptr); } static void bgp_decode_community(struct bgp_parse_state *s, uint code UNUSED, uint flags, byte *data, uint len, ea_list **to) { if (!len || (len % 4)) WITHDRAW(BAD_LENGTH, "COMMUNITY", len); struct adata *ad = lp_alloc_adata(s->pool, len); get_u32s(data, (u32 *) ad->data, len / 4); bgp_set_attr_ptr(to, s->pool, BA_COMMUNITY, flags, ad); } static void bgp_export_originator_id(struct bgp_export_state *s, eattr *a) { if (!s->proto->is_internal) UNSET(a); } static void bgp_decode_originator_id(struct bgp_parse_state *s, uint code UNUSED, uint flags, byte *data, uint len, ea_list **to) { if (!s->proto->is_internal) DISCARD(BAD_EBGP, "ORIGINATOR_ID"); if (len != 4) WITHDRAW(BAD_LENGTH, "ORIGINATOR_ID", len); u32 val = get_u32(data); bgp_set_attr_u32(to, s->pool, BA_ORIGINATOR_ID, flags, val); } static void bgp_export_cluster_list(struct bgp_export_state *s UNUSED, eattr *a) { if (!s->proto->is_internal) UNSET(a); if (a->u.ptr->length == 0) UNSET(a); } static void bgp_decode_cluster_list(struct bgp_parse_state *s, uint code UNUSED, uint flags, byte *data, uint len, ea_list **to) { if (!s->proto->is_internal) DISCARD(BAD_EBGP, "CLUSTER_LIST"); if (!len || (len % 4)) WITHDRAW(BAD_LENGTH, "CLUSTER_LIST", len); struct adata *ad = lp_alloc_adata(s->pool, len); get_u32s(data, (u32 *) ad->data, len / 4); bgp_set_attr_ptr(to, s->pool, BA_CLUSTER_LIST, flags, ad); } static void bgp_format_cluster_list(eattr *a, byte *buf, uint size) { /* Truncates cluster lists larger than buflen, probably not a problem */ int_set_format(a->u.ptr, 0, -1, buf, size); } static inline u32 get_af3(byte *buf) { return (get_u16(buf) << 16) | buf[2]; } static void bgp_decode_mp_reach_nlri(struct bgp_parse_state *s, uint code UNUSED, uint flags UNUSED, byte *data, uint len, ea_list **to UNUSED) { /* * 2 B MP_REACH_NLRI data - Address Family Identifier * 1 B MP_REACH_NLRI data - Subsequent Address Family Identifier * 1 B MP_REACH_NLRI data - Length of Next Hop Network Address * var MP_REACH_NLRI data - Network Address of Next Hop * 1 B MP_REACH_NLRI data - Reserved (zero) * var MP_REACH_NLRI data - Network Layer Reachability Information */ if ((len < 5) || (len < (5 + (uint) data[3]))) bgp_parse_error(s, 9); s->mp_reach_af = get_af3(data); s->mp_next_hop_len = data[3]; s->mp_next_hop_data = data + 4; s->mp_reach_len = len - 5 - s->mp_next_hop_len; s->mp_reach_nlri = data + 5 + s->mp_next_hop_len; } static void bgp_decode_mp_unreach_nlri(struct bgp_parse_state *s, uint code UNUSED, uint flags UNUSED, byte *data, uint len, ea_list **to UNUSED) { /* * 2 B MP_UNREACH_NLRI data - Address Family Identifier * 1 B MP_UNREACH_NLRI data - Subsequent Address Family Identifier * var MP_UNREACH_NLRI data - Network Layer Reachability Information */ if (len < 3) bgp_parse_error(s, 9); s->mp_unreach_af = get_af3(data); s->mp_unreach_len = len - 3; s->mp_unreach_nlri = data + 3; } static void bgp_export_ext_community(struct bgp_export_state *s, eattr *a) { a->u.ptr = ec_set_del_nontrans(s->pool, a->u.ptr); if (a->u.ptr->length == 0) UNSET(a); ec_set_sort_x(a->u.ptr); } static void bgp_decode_ext_community(struct bgp_parse_state *s, uint code UNUSED, uint flags, byte *data, uint len, ea_list **to) { if (!len || (len % 8)) WITHDRAW(BAD_LENGTH, "EXT_COMMUNITY", len); struct adata *ad = lp_alloc_adata(s->pool, len); get_u32s(data, (u32 *) ad->data, len / 4); bgp_set_attr_ptr(to, s->pool, BA_EXT_COMMUNITY, flags, ad); } static void bgp_decode_as4_aggregator(struct bgp_parse_state *s, uint code UNUSED, uint flags, byte *data, uint len, ea_list **to) { if (s->as4_session) DISCARD(NEW_BGP, "AS4_AGGREGATOR"); if (len != 8) DISCARD(BAD_LENGTH, "AS4_AGGREGATOR", len); bgp_set_attr_data(to, s->pool, BA_AS4_AGGREGATOR, flags, data, len); } static void bgp_decode_as4_path(struct bgp_parse_state *s, uint code UNUSED, uint flags, byte *data, uint len, ea_list **to) { char err[128]; if (s->as4_session) DISCARD(NEW_BGP, "AS4_PATH"); if (len < 6) DISCARD(BAD_LENGTH, "AS4_PATH", len); if (!as_path_valid(data, len, 4, 1, err, sizeof(err))) DISCARD("Malformed AS4_PATH attribute - %s", err); struct adata *a = lp_alloc_adata(s->pool, len); memcpy(a->data, data, len); /* AS_CONFED* segments are invalid in AS4_PATH; RFC 6793 6 */ if (as_path_contains_confed(a)) { REPORT("Discarding AS_CONFED* segment from AS4_PATH attribute"); a = as_path_strip_confed(s->pool, a); } bgp_set_attr_ptr(to, s->pool, BA_AS4_PATH, flags, a); } static void bgp_export_large_community(struct bgp_export_state *s, eattr *a) { if (a->u.ptr->length == 0) UNSET(a); a->u.ptr = lc_set_sort(s->pool, a->u.ptr); } static void bgp_decode_large_community(struct bgp_parse_state *s, uint code UNUSED, uint flags, byte *data, uint len, ea_list **to) { if (!len || (len % 12)) WITHDRAW(BAD_LENGTH, "LARGE_COMMUNITY", len); struct adata *ad = lp_alloc_adata(s->pool, len); get_u32s(data, (u32 *) ad->data, len / 4); bgp_set_attr_ptr(to, s->pool, BA_LARGE_COMMUNITY, flags, ad); } static void bgp_export_mpls_label_stack(struct bgp_export_state *s, eattr *a) { net_addr *n = s->route->net->n.addr; u32 *labels = (u32 *) a->u.ptr->data; uint lnum = a->u.ptr->length / 4; /* Perhaps we should just ignore it? */ if (!s->mpls) WITHDRAW("Unexpected MPLS stack"); /* Empty MPLS stack is not allowed */ if (!lnum) WITHDRAW("Malformed MPLS stack - empty"); /* This is ugly, but we must ensure that labels fit into NLRI field */ if ((24*lnum + (net_is_vpn(n) ? 64 : 0) + net_pxlen(n)) > 255) WITHDRAW("Malformed MPLS stack - too many labels (%u)", lnum); for (uint i = 0; i < lnum; i++) { if (labels[i] > 0xfffff) WITHDRAW("Malformed MPLS stack - invalid label (%u)", labels[i]); /* TODO: Check for special-purpose label values? */ } } static int bgp_encode_mpls_label_stack(struct bgp_write_state *s, eattr *a, byte *buf UNUSED, uint size UNUSED) { /* * MPLS labels are encoded as a part of the NLRI in MP_REACH_NLRI attribute, * so we store MPLS_LABEL_STACK and encode it later by AFI-specific hooks. */ s->mpls_labels = a->u.ptr; return 0; } static void bgp_decode_mpls_label_stack(struct bgp_parse_state *s, uint code UNUSED, uint flags UNUSED, byte *data UNUSED, uint len UNUSED, ea_list **to UNUSED) { DISCARD("Discarding received attribute #0"); } static void bgp_format_mpls_label_stack(eattr *a, byte *buf, uint size) { u32 *labels = (u32 *) a->u.ptr->data; uint lnum = a->u.ptr->length / 4; char *pos = buf; for (uint i = 0; i < lnum; i++) { if (size < 20) { bsprintf(pos, "..."); return; } uint l = bsprintf(pos, "%d/", labels[i]); ADVANCE(pos, size, l); } /* Clear last slash or terminate empty string */ pos[lnum ? -1 : 0] = 0; } static inline void bgp_decode_unknown(struct bgp_parse_state *s, uint code, uint flags, byte *data, uint len, ea_list **to) { /* Cannot use bgp_set_attr_data() as it works on known attributes only */ ea_set_attr_data(to, s->pool, EA_CODE(EAP_BGP, code), flags, EAF_TYPE_OPAQUE, data, len); } /* * Attribute table */ static const struct bgp_attr_desc bgp_attr_table[] = { [BA_ORIGIN] = { .name = "origin", .type = EAF_TYPE_INT, .flags = BAF_TRANSITIVE, .export = bgp_export_origin, .encode = bgp_encode_u8, .decode = bgp_decode_origin, .format = bgp_format_origin, }, [BA_AS_PATH] = { .name = "as_path", .type = EAF_TYPE_AS_PATH, .flags = BAF_TRANSITIVE, .encode = bgp_encode_as_path, .decode = bgp_decode_as_path, }, [BA_NEXT_HOP] = { .name = "next_hop", .type = EAF_TYPE_IP_ADDRESS, .flags = BAF_TRANSITIVE, .encode = bgp_encode_next_hop, .decode = bgp_decode_next_hop, .format = bgp_format_next_hop, }, [BA_MULTI_EXIT_DISC] = { .name = "med", .type = EAF_TYPE_INT, .flags = BAF_OPTIONAL, .encode = bgp_encode_u32, .decode = bgp_decode_med, }, [BA_LOCAL_PREF] = { .name = "local_pref", .type = EAF_TYPE_INT, .flags = BAF_TRANSITIVE, .export = bgp_export_local_pref, .encode = bgp_encode_u32, .decode = bgp_decode_local_pref, }, [BA_ATOMIC_AGGR] = { .name = "atomic_aggr", .type = EAF_TYPE_OPAQUE, .flags = BAF_TRANSITIVE, .encode = bgp_encode_raw, .decode = bgp_decode_atomic_aggr, }, [BA_AGGREGATOR] = { .name = "aggregator", .type = EAF_TYPE_OPAQUE, .flags = BAF_OPTIONAL | BAF_TRANSITIVE, .encode = bgp_encode_aggregator, .decode = bgp_decode_aggregator, .format = bgp_format_aggregator, }, [BA_COMMUNITY] = { .name = "community", .type = EAF_TYPE_INT_SET, .flags = BAF_OPTIONAL | BAF_TRANSITIVE, .export = bgp_export_community, .encode = bgp_encode_u32s, .decode = bgp_decode_community, }, [BA_ORIGINATOR_ID] = { .name = "originator_id", .type = EAF_TYPE_ROUTER_ID, .flags = BAF_OPTIONAL, .export = bgp_export_originator_id, .encode = bgp_encode_u32, .decode = bgp_decode_originator_id, }, [BA_CLUSTER_LIST] = { .name = "cluster_list", .type = EAF_TYPE_INT_SET, .flags = BAF_OPTIONAL, .export = bgp_export_cluster_list, .encode = bgp_encode_u32s, .decode = bgp_decode_cluster_list, .format = bgp_format_cluster_list, }, [BA_MP_REACH_NLRI] = { .name = "mp_reach_nlri", .type = EAF_TYPE_OPAQUE, .flags = BAF_OPTIONAL, .decode = bgp_decode_mp_reach_nlri, }, [BA_MP_UNREACH_NLRI] = { .name = "mp_unreach_nlri", .type = EAF_TYPE_OPAQUE, .flags = BAF_OPTIONAL, .decode = bgp_decode_mp_unreach_nlri, }, [BA_EXT_COMMUNITY] = { .name = "ext_community", .type = EAF_TYPE_EC_SET, .flags = BAF_OPTIONAL | BAF_TRANSITIVE, .export = bgp_export_ext_community, .encode = bgp_encode_u32s, .decode = bgp_decode_ext_community, }, [BA_AS4_PATH] = { .name = "as4_path", .type = EAF_TYPE_AS_PATH, .flags = BAF_OPTIONAL | BAF_TRANSITIVE, .encode = bgp_encode_raw, .decode = bgp_decode_as4_path, }, [BA_AS4_AGGREGATOR] = { .name = "as4_aggregator", .type = EAF_TYPE_OPAQUE, .flags = BAF_OPTIONAL | BAF_TRANSITIVE, .encode = bgp_encode_raw, .decode = bgp_decode_as4_aggregator, .format = bgp_format_aggregator, }, [BA_LARGE_COMMUNITY] = { .name = "large_community", .type = EAF_TYPE_LC_SET, .flags = BAF_OPTIONAL | BAF_TRANSITIVE, .export = bgp_export_large_community, .encode = bgp_encode_u32s, .decode = bgp_decode_large_community, }, [BA_MPLS_LABEL_STACK] = { .name = "mpls_label_stack", .type = EAF_TYPE_INT_SET, .export = bgp_export_mpls_label_stack, .encode = bgp_encode_mpls_label_stack, .decode = bgp_decode_mpls_label_stack, .format = bgp_format_mpls_label_stack, }, }; static inline int bgp_attr_known(uint code) { return (code < ARRAY_SIZE(bgp_attr_table)) && bgp_attr_table[code].name; } /* * Attribute export */ static inline void bgp_export_attr(struct bgp_export_state *s, eattr *a, ea_list *to) { if (EA_PROTO(a->id) != EAP_BGP) return; uint code = EA_ID(a->id); if (bgp_attr_known(code)) { const struct bgp_attr_desc *desc = &bgp_attr_table[code]; /* The flags might have been zero if the attr was added by filters */ a->flags = (a->flags & BAF_PARTIAL) | desc->flags; /* Set partial bit if new opt-trans attribute is attached to non-local route */ if ((s->src != NULL) && (a->type & EAF_ORIGINATED) && (a->flags & BAF_OPTIONAL) && (a->flags & BAF_TRANSITIVE)) a->flags |= BAF_PARTIAL; /* Call specific hook */ CALL(desc->export, s, a); /* Attribute might become undefined in hook */ if ((a->type & EAF_TYPE_MASK) == EAF_TYPE_UNDEF) return; } else { /* Don't re-export unknown non-transitive attributes */ if (!(a->flags & BAF_TRANSITIVE)) return; a->flags |= BAF_PARTIAL; } /* Append updated attribute */ to->attrs[to->count++] = *a; } /** * bgp_export_attrs - export BGP attributes * @s: BGP export state * @attrs: a list of extended attributes * * The bgp_export_attrs() function takes a list of attributes and merges it to * one newly allocated and sorted segment. Attributes are validated and * normalized by type-specific export hooks and attribute flags are updated. * Some attributes may be eliminated (e.g. unknown non-tranitive attributes, or * empty community sets). * * Result: one sorted attribute list segment, or NULL if attributes are unsuitable. */ static inline ea_list * bgp_export_attrs(struct bgp_export_state *s, ea_list *attrs) { /* Merge the attribute list */ ea_list *new = lp_alloc(s->pool, ea_scan(attrs)); ea_merge(attrs, new); ea_sort(new); uint i, count; count = new->count; new->count = 0; /* Export each attribute */ for (i = 0; i < count; i++) bgp_export_attr(s, &new->attrs[i], new); if (s->err_withdraw) return NULL; return new; } /* * Attribute encoding */ static inline int bgp_encode_attr(struct bgp_write_state *s, eattr *a, byte *buf, uint size) { ASSERT(EA_PROTO(a->id) == EAP_BGP); uint code = EA_ID(a->id); if (bgp_attr_known(code)) return bgp_attr_table[code].encode(s, a, buf, size); else return bgp_encode_raw(s, a, buf, size); } /** * bgp_encode_attrs - encode BGP attributes * @s: BGP write state * @attrs: a list of extended attributes * @buf: buffer * @end: buffer end * * 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. */ int bgp_encode_attrs(struct bgp_write_state *s, ea_list *attrs, byte *buf, byte *end) { byte *pos = buf; int i, len; for (i = 0; i < attrs->count; i++) { len = bgp_encode_attr(s, &attrs->attrs[i], pos, end - pos); if (len < 0) return -1; pos += len; } return pos - buf; } /* * Attribute decoding */ static void bgp_process_as4_attrs(ea_list **attrs, struct linpool *pool); static inline int bgp_as_path_loopy(struct bgp_proto *p, ea_list *attrs, u32 asn) { eattr *e = bgp_find_attr(attrs, BA_AS_PATH); int num = p->cf->allow_local_as + 1; return (e && (num > 0) && as_path_contains(e->u.ptr, asn, num)); } static inline int bgp_originator_id_loopy(struct bgp_proto *p, ea_list *attrs) { eattr *e = bgp_find_attr(attrs, BA_ORIGINATOR_ID); return (e && (e->u.data == p->local_id)); } static inline int bgp_cluster_list_loopy(struct bgp_proto *p, ea_list *attrs) { eattr *e = bgp_find_attr(attrs, BA_CLUSTER_LIST); return (e && int_set_contains(e->u.ptr, p->rr_cluster_id)); } static inline void bgp_decode_attr(struct bgp_parse_state *s, uint code, uint flags, byte *data, uint len, ea_list **to) { /* Handle duplicate attributes; RFC 7606 3 (g) */ if (BIT32_TEST(s->attrs_seen, code)) { if ((code == BA_MP_REACH_NLRI) || (code == BA_MP_UNREACH_NLRI)) bgp_parse_error(s, 1); else DISCARD("Discarding duplicate attribute (code %u)", code); } BIT32_SET(s->attrs_seen, code); if (bgp_attr_known(code)) { const struct bgp_attr_desc *desc = &bgp_attr_table[code]; /* Handle conflicting flags; RFC 7606 3 (c) */ if ((flags ^ desc->flags) & (BAF_OPTIONAL | BAF_TRANSITIVE)) WITHDRAW("Malformed %s attribute - conflicting flags (%02x)", desc->name, flags); desc->decode(s, code, flags, data, len, to); } else /* Unknown attribute */ { if (!(flags & BAF_OPTIONAL)) WITHDRAW("Unknown attribute (code %u) - conflicting flags (%02x)", code, flags); bgp_decode_unknown(s, code, flags, data, len, to); } } /** * bgp_decode_attrs - check and decode BGP attributes * @s: BGP parse state * @data: start of attribute block * @len: length of attribute block * * 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 an (uncached) &rta. */ ea_list * bgp_decode_attrs(struct bgp_parse_state *s, byte *data, uint len) { struct bgp_proto *p = s->proto; ea_list *attrs = NULL; uint code, flags, alen; byte *pos = data; /* Parse the attributes */ while (len) { alen = 0; /* Read attribute type */ if (len < 2) goto framing_error; flags = pos[0]; code = pos[1]; ADVANCE(pos, len, 2); /* Read attribute length */ if (flags & BAF_EXT_LEN) { if (len < 2) goto framing_error; alen = get_u16(pos); ADVANCE(pos, len, 2); } else { if (len < 1) goto framing_error; alen = *pos; ADVANCE(pos, len, 1); } if (alen > len) goto framing_error; DBG("Attr %02x %02x %u\n", code, flags, alen); bgp_decode_attr(s, code, flags, pos, alen, &attrs); ADVANCE(pos, len, alen); } if (s->err_withdraw) goto withdraw; /* If there is no reachability NLRI, we are finished */ if (!s->ip_reach_len && !s->mp_reach_len) return NULL; /* Handle missing mandatory attributes; RFC 7606 3 (d) */ if (!BIT32_TEST(s->attrs_seen, BA_ORIGIN)) { REPORT(NO_MANDATORY, "ORIGIN"); goto withdraw; } if (!BIT32_TEST(s->attrs_seen, BA_AS_PATH)) { REPORT(NO_MANDATORY, "AS_PATH"); goto withdraw; } /* When receiving attributes from non-AS4-aware BGP speaker, we have to reconstruct AS_PATH and AGGREGATOR attributes; RFC 6793 4.2.3 */ if (!p->as4_session) bgp_process_as4_attrs(&attrs, s->pool); /* Reject routes with our ASN in AS_PATH attribute */ if (bgp_as_path_loopy(p, attrs, p->local_as)) goto withdraw; /* Reject routes with our Confederation ID in AS_PATH attribute; RFC 5065 4.0 */ if ((p->public_as != p->local_as) && bgp_as_path_loopy(p, attrs, p->public_as)) goto withdraw; /* Reject routes with our Router ID in ORIGINATOR_ID attribute; RFC 4456 8 */ if (p->is_internal && bgp_originator_id_loopy(p, attrs)) goto withdraw; /* Reject routes with our Cluster ID in CLUSTER_LIST attribute; RFC 4456 8 */ if (p->rr_client && bgp_cluster_list_loopy(p, attrs)) goto withdraw; /* If there is no local preference, define one */ if (!BIT32_TEST(s->attrs_seen, BA_LOCAL_PREF)) bgp_set_attr_u32(&attrs, s->pool, BA_LOCAL_PREF, 0, p->cf->default_local_pref); return attrs; framing_error: /* RFC 7606 4 - handle attribute framing errors */ REPORT("Malformed attribute list - framing error (%u/%u) at %d", alen, len, (int) (pos - s->attrs)); withdraw: /* RFC 7606 5.2 - handle missing NLRI during errors */ if (!s->ip_reach_len && !s->mp_reach_len) bgp_parse_error(s, 1); s->err_withdraw = 1; return NULL; } /* * Route bucket hash table */ #define RBH_KEY(b) b->eattrs, b->hash #define RBH_NEXT(b) b->next #define RBH_EQ(a1,h1,a2,h2) h1 == h2 && ea_same(a1, a2) #define RBH_FN(a,h) h #define RBH_REHASH bgp_rbh_rehash #define RBH_PARAMS /8, *2, 2, 2, 8, 20 HASH_DEFINE_REHASH_FN(RBH, struct bgp_bucket) void bgp_init_bucket_table(struct bgp_channel *c) { HASH_INIT(c->bucket_hash, c->pool, 8); init_list(&c->bucket_queue); c->withdraw_bucket = NULL; } void bgp_free_bucket_table(struct bgp_channel *c) { HASH_FREE(c->bucket_hash); struct bgp_bucket *b; WALK_LIST_FIRST(b, c->bucket_queue) { rem_node(&b->send_node); mb_free(b); } mb_free(c->withdraw_bucket); c->withdraw_bucket = NULL; } static struct bgp_bucket * bgp_get_bucket(struct bgp_channel *c, ea_list *new) { /* Hash and lookup */ u32 hash = ea_hash(new); struct bgp_bucket *b = HASH_FIND(c->bucket_hash, RBH, new, hash); if (b) return b; uint ea_size = sizeof(ea_list) + new->count * sizeof(eattr); uint ea_size_aligned = BIRD_ALIGN(ea_size, CPU_STRUCT_ALIGN); uint size = sizeof(struct bgp_bucket) + ea_size_aligned; uint i; byte *dest; /* 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 */ b = mb_alloc(c->pool, size); init_list(&b->prefixes); b->hash = hash; /* Copy list of extended attributes */ 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); } } /* Insert the bucket to send queue and bucket hash */ add_tail(&c->bucket_queue, &b->send_node); HASH_INSERT2(c->bucket_hash, RBH, c->pool, b); return b; } static struct bgp_bucket * bgp_get_withdraw_bucket(struct bgp_channel *c) { if (!c->withdraw_bucket) { c->withdraw_bucket = mb_allocz(c->pool, sizeof(struct bgp_bucket)); init_list(&c->withdraw_bucket->prefixes); } return c->withdraw_bucket; } void bgp_free_bucket(struct bgp_channel *c, struct bgp_bucket *b) { rem_node(&b->send_node); HASH_REMOVE2(c->bucket_hash, RBH, c->pool, b); mb_free(b); } void bgp_defer_bucket(struct bgp_channel *c, struct bgp_bucket *b) { rem_node(&b->send_node); add_tail(&c->bucket_queue, &b->send_node); } void bgp_withdraw_bucket(struct bgp_channel *c, struct bgp_bucket *b) { struct bgp_proto *p = (void *) c->c.proto; struct bgp_bucket *wb = bgp_get_withdraw_bucket(c); log(L_ERR "%s: Attribute list too long", p->p.name); while (!EMPTY_LIST(b->prefixes)) { struct bgp_prefix *px = HEAD(b->prefixes); log(L_ERR "%s: - withdrawing %N", p->p.name, &px->net); rem_node(&px->buck_node); add_tail(&wb->prefixes, &px->buck_node); } } /* * Prefix hash table */ #define PXH_KEY(px) px->net, px->path_id, px->hash #define PXH_NEXT(px) px->next #define PXH_EQ(n1,i1,h1,n2,i2,h2) h1 == h2 && i1 == i2 && net_equal(n1, n2) #define PXH_FN(n,i,h) h #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_channel *c) { HASH_INIT(c->prefix_hash, c->pool, 8); uint alen = net_addr_length[c->c.net_type]; c->prefix_slab = alen ? sl_new(c->pool, sizeof(struct bgp_prefix) + alen) : NULL; } void bgp_free_prefix_table(struct bgp_channel *c) { HASH_FREE(c->prefix_hash); rfree(c->prefix_slab); c->prefix_slab = NULL; } static struct bgp_prefix * bgp_get_prefix(struct bgp_channel *c, net_addr *net, u32 path_id) { u32 hash = net_hash(net) ^ u32_hash(path_id); struct bgp_prefix *px = HASH_FIND(c->prefix_hash, PXH, net, path_id, hash); if (px) { rem_node(&px->buck_node); return px; } if (c->prefix_slab) px = sl_alloc(c->prefix_slab); else px = mb_alloc(c->pool, sizeof(struct bgp_prefix) + net->length); px->buck_node.next = NULL; px->buck_node.prev = NULL; px->hash = hash; px->path_id = path_id; net_copy(px->net, net); HASH_INSERT2(c->prefix_hash, PXH, c->pool, px); return px; } void bgp_free_prefix(struct bgp_channel *c, struct bgp_prefix *px) { rem_node(&px->buck_node); HASH_REMOVE2(c->prefix_hash, PXH, c->pool, px); if (c->prefix_slab) sl_free(c->prefix_slab, px); else mb_free(px); } /* * BGP protocol glue */ int bgp_import_control(struct proto *P, rte **new, ea_list **attrs UNUSED, struct linpool *pool UNUSED) { rte *e = *new; struct proto *SRC = e->attrs->src->proto; struct bgp_proto *p = (struct bgp_proto *) P; struct bgp_proto *src = (SRC->proto == &proto_bgp) ? (struct bgp_proto *) SRC : NULL; /* Reject our routes */ if (src == p) return -1; /* Accept non-BGP routes */ if (src == NULL) return 0; // XXXX: Check next hop AF /* IBGP route reflection, RFC 4456 */ if (p->is_internal && src->is_internal && (p->local_as == src->local_as)) { /* Rejected unless configured as route reflector */ if (!p->rr_client && !src->rr_client) return -1; /* Generally, this should be handled when path is received, but we check it also here as rr_cluster_id may be undefined or different in src. */ if (p->rr_cluster_id && bgp_cluster_list_loopy(p, e->attrs->eattrs)) return -1; } /* Handle well-known communities, RFC 1997 */ struct eattr *c; if (p->cf->interpret_communities && (c = ea_find(e->attrs->eattrs, EA_CODE(EAP_BGP, BA_COMMUNITY)))) { struct adata *d = c->u.ptr; /* Do not export anywhere */ if (int_set_contains(d, BGP_COMM_NO_ADVERTISE)) return -1; /* Do not export outside of AS (or member-AS) */ if (!p->is_internal && int_set_contains(d, BGP_COMM_NO_EXPORT_SUBCONFED)) return -1; /* Do not export outside of AS (or confederation) */ if (!p->is_interior && int_set_contains(d, BGP_COMM_NO_EXPORT)) return -1; } return 0; } static adata null_adata; /* adata of length 0 */ static ea_list * bgp_update_attrs(struct bgp_proto *p, struct bgp_channel *c, rte *e, ea_list *attrs0, struct linpool *pool) { struct proto *SRC = e->attrs->src->proto; struct bgp_proto *src = (SRC->proto == &proto_bgp) ? (void *) SRC : NULL; struct bgp_export_state s = { .proto = p, .channel = c, .pool = pool, .src = src, .route = e, .mpls = c->desc->mpls }; ea_list *attrs = attrs0; eattr *a; adata *ad; /* ORIGIN attribute - mandatory, attach if missing */ if (! bgp_find_attr(attrs0, BA_ORIGIN)) bgp_set_attr_u32(&attrs, pool, BA_ORIGIN, 0, src ? ORIGIN_INCOMPLETE : ORIGIN_IGP); /* AS_PATH attribute - mandatory */ a = bgp_find_attr(attrs0, BA_AS_PATH); ad = a ? a->u.ptr : &null_adata; /* AS_PATH attribute - strip AS_CONFED* segments outside confederation */ if ((!p->cf->confederation || !p->is_interior) && as_path_contains_confed(ad)) ad = as_path_strip_confed(pool, ad); /* AS_PATH attribute - keep or prepend ASN */ if (p->is_internal || (p->rs_client && src && src->rs_client)) { /* IBGP or route server -> just ensure there is one */ if (!a) bgp_set_attr_ptr(&attrs, pool, BA_AS_PATH, 0, &null_adata); } else if (p->is_interior) { /* Confederation -> prepend ASN as AS_CONFED_SEQUENCE */ ad = as_path_prepend2(pool, ad, AS_PATH_CONFED_SEQUENCE, p->public_as); bgp_set_attr_ptr(&attrs, pool, BA_AS_PATH, 0, ad); } else /* Regular EBGP (no RS, no confederation) */ { /* Regular EBGP -> prepend ASN as regular sequence */ ad = as_path_prepend2(pool, ad, AS_PATH_SEQUENCE, p->public_as); bgp_set_attr_ptr(&attrs, pool, BA_AS_PATH, 0, ad); /* MULTI_EXIT_DESC attribute - accept only if set in export filter */ a = bgp_find_attr(attrs0, BA_MULTI_EXIT_DISC); if (a && !(a->type & EAF_FRESH)) bgp_unset_attr(&attrs, pool, BA_MULTI_EXIT_DISC); } /* NEXT_HOP attribute - delegated to AF-specific hook */ a = bgp_find_attr(attrs0, BA_NEXT_HOP); bgp_update_next_hop(&s, a, &attrs); /* LOCAL_PREF attribute - required for IBGP, attach if missing */ if (p->is_interior && ! bgp_find_attr(attrs0, BA_LOCAL_PREF)) bgp_set_attr_u32(&attrs, pool, BA_LOCAL_PREF, 0, p->cf->default_local_pref); /* IBGP route reflection, RFC 4456 */ if (src && src->is_internal && p->is_internal && (src->local_as == p->local_as)) { /* ORIGINATOR_ID attribute - attach if not already set */ if (! bgp_find_attr(attrs0, BA_ORIGINATOR_ID)) bgp_set_attr_u32(&attrs, pool, BA_ORIGINATOR_ID, 0, src->remote_id); /* CLUSTER_LIST attribute - prepend cluster ID */ a = bgp_find_attr(attrs0, BA_CLUSTER_LIST); ad = a ? a->u.ptr : NULL; /* Prepend src cluster ID */ if (src->rr_cluster_id) ad = int_set_prepend(pool, ad, src->rr_cluster_id); /* Prepend dst cluster ID if src and dst clusters are different */ if (p->rr_cluster_id && (src->rr_cluster_id != p->rr_cluster_id)) ad = int_set_prepend(pool, ad, p->rr_cluster_id); /* Should be at least one prepended cluster ID */ bgp_set_attr_ptr(&attrs, pool, BA_CLUSTER_LIST, 0, ad); } /* AS4_* transition attributes, RFC 6793 4.2.2 */ if (! p->as4_session) { a = bgp_find_attr(attrs, BA_AS_PATH); if (a && as_path_contains_as4(a->u.ptr)) { bgp_set_attr_ptr(&attrs, pool, BA_AS_PATH, 0, as_path_to_old(pool, a->u.ptr)); bgp_set_attr_ptr(&attrs, pool, BA_AS4_PATH, 0, as_path_strip_confed(pool, a->u.ptr)); } a = bgp_find_attr(attrs, BA_AGGREGATOR); if (a && aggregator_contains_as4(a->u.ptr)) { bgp_set_attr_ptr(&attrs, pool, BA_AGGREGATOR, 0, aggregator_to_old(pool, a->u.ptr)); bgp_set_attr_ptr(&attrs, pool, BA_AS4_AGGREGATOR, 0, a->u.ptr); } } /* * Presence of mandatory attributes ORIGIN and AS_PATH is ensured by above * conditions. Presence and validity of quasi-mandatory NEXT_HOP attribute * should be checked in AF-specific hooks. */ /* Apply per-attribute export hooks for validatation and normalization */ return bgp_export_attrs(&s, attrs); } void bgp_rt_notify(struct proto *P, struct channel *C, net *n, rte *new, rte *old, ea_list *attrs) { struct bgp_proto *p = (void *) P; struct bgp_channel *c = (void *) C; struct bgp_bucket *buck; struct bgp_prefix *px; u32 path; if (new) { attrs = bgp_update_attrs(p, c, new, attrs, bgp_linpool2); /* If attributes are invalid, we fail back to withdraw */ buck = attrs ? bgp_get_bucket(c, attrs) : bgp_get_withdraw_bucket(c); path = new->attrs->src->global_id; lp_flush(bgp_linpool2); } else { buck = bgp_get_withdraw_bucket(c); path = old->attrs->src->global_id; } px = bgp_get_prefix(c, n->n.addr, c->add_path_tx ? path : 0); add_tail(&buck->prefixes, &px->buck_node); bgp_schedule_packet(p->conn, c, PKT_UPDATE); } 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_regular(e->u.ptr, &as)) return as; /* If AS_PATH is not defined, we treat rte as locally originated */ struct bgp_proto *p = (void *) r->attrs->src->proto; return p->cf->confederation ?: p->local_as; } static inline int rte_resolvable(rte *rt) { return rt->attrs->dest == RTD_UNICAST; } 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_interior > old_bgp->is_interior) return 0; if (new_bgp->is_interior < old_bgp->is_interior) 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 neighbor 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_interior != sec_bgp->is_interior) 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; } /* * Reconstruct AS_PATH and AGGREGATOR according to RFC 6793 4.2.3 */ static void bgp_process_as4_attrs(ea_list **attrs, struct linpool *pool) { eattr *p2 = bgp_find_attr(*attrs, BA_AS_PATH); eattr *p4 = bgp_find_attr(*attrs, BA_AS4_PATH); eattr *a2 = bgp_find_attr(*attrs, BA_AGGREGATOR); eattr *a4 = bgp_find_attr(*attrs, BA_AS4_AGGREGATOR); /* First, unset AS4_* attributes */ if (p4) bgp_unset_attr(attrs, pool, BA_AS4_PATH); if (a4) bgp_unset_attr(attrs, pool, BA_AS4_AGGREGATOR); /* Handle AGGREGATOR attribute */ if (a2 && a4) { u32 a2_asn = get_u32(a2->u.ptr->data); /* If routes were aggregated by an old router, then AS4_PATH and AS4_AGGREGATOR are invalid. In that case we give up. */ if (a2_asn != AS_TRANS) return; /* Use AS4_AGGREGATOR instead of AGGREGATOR */ a2->u.ptr = a4->u.ptr; } /* Handle AS_PATH attribute */ if (p2 && p4) { /* Both as_path_getlen() and as_path_cut() take AS_CONFED* as zero length */ int p2_len = as_path_getlen(p2->u.ptr); int p4_len = as_path_getlen(p4->u.ptr); /* AS_PATH is too short, give up */ if (p2_len < p4_len) return; /* Merge AS_PATH and AS4_PATH */ as_path_cut(p2->u.ptr, p2_len - p4_len); p2->u.ptr = as_path_merge(pool, p2->u.ptr, p4->u.ptr); } } int bgp_get_attr(eattr *a, byte *buf, int buflen) { uint i = EA_ID(a->id); const struct bgp_attr_desc *d; int len; if (bgp_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_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, "]"); }