ferrix/crates/server/proto/config.proto

syntax = "proto3";

package bgp.server;

// Top level BGP Server configuration.
message BgpConfig {
  // The router ID, written as a dotted-quad IPv4 address (e.g. "192.0.2.1").
  // Required even on IPv6-only routers per RFC 4271.
  string router_id = 1;

  // The local 4-byte AS number (RFC 6793).
  uint32 local_asn = 2;

  // Endpoints to accept incoming BGP connections on.
  // Defaults to 0.0.0.0:179 and [::]:179 when empty.
  repeated TcpEndpoint listen_endpoints = 3;

  // Peers configured on this server.
  repeated Peer peers = 4;

  // Routes this router originates and announces to every peer.
  repeated OriginatedRoute originate = 5;

  // Where to serve the HTTP API, status page and metrics. The port is
  // required. Unset disables the HTTP server.
  TcpEndpoint http_endpoint = 6;

  // Initial delay between attempts to connect to a configured peer, in
  // seconds. Doubles after each failure up to two minutes. Defaults to 5.
  uint32 connect_retry_seconds = 7;

  // Connection collisions (RFC 4271 §6.8) against a session that is already
  // Established are, by default, resolved by closing the new connection.
  // When true they are resolved like any other collision: the connection
  // initiated by the higher BGP Identifier survives, and a second connection
  // opened by the same side replaces the first. This lets a peer that
  // restarted take over from a session we have not yet noticed is dead,
  // instead of being refused until the hold timer expires.
  bool collision_detect_established_state = 8;

  // Connections are accepted only from the addresses of configured peers;
  // from anywhere else they are closed before a byte is read. When true,
  // any host that can reach a listening endpoint may open a session, as
  // any AS it cares to name, and have its routes taken. That is for
  // testing on a closed network and nothing else.
  bool accept_unconfigured_peers = 9;

  // Route origin validation (RFC 6811) and AS path verification with the
  // RPKI. Left out, routes are not validated.
  Rpki rpki = 10;

  // Put the best route of every prefix in the kernel's routing table, so
  // that the machine forwards packets by them. Left out, the daemon only
  // speaks BGP and the machine's forwarding is not touched.
  Kernel kernel = 11;

  // What is announced, and how, to every peer that has no `export` of its
  // own.
  ExportPolicy export = 12;

  // Let routes say, with communities, which peers they are passed on to
  // and how far away we look to them, as the route servers of Internet
  // exchanges and transit networks do. With L our own AS number, P a
  // peer's, and G a group of sessions (`groups` of a peer):
  //
  //   0:P   or  L:0:P    not to the peer with AS P
  //   L:P   or  L:1:P    to the peer with AS P, and then only to peers
  //                      named so
  //   0:L   or  L:0:0    to nobody
  //               L:11:P  with our AS once more on the path to the peer
  //               L:12:P  with AS P; twice, three times. P 0 is every
  //               L:13:P  peer in another AS.
  //               L:20:G  not to the sessions of group G
  //               L:21:G  to the sessions of group G, and then only to
  //                       sessions named so, by group or AS
  //               L:31:G  with our AS once more on the path to the
  //               L:32:G  sessions of group G; twice, three times
  //               L:33:G
  //
  // A route with none of these goes to everyone it otherwise would. "Not"
  // wins over "to". Of several prepends that apply, the most counts, on
  // top of the session's export.as_path_prepend. The two-part form is a
  // standard community, with room for AS numbers below 65536; the
  // three-part forms are large communities and work for any.
  //
  // They are acted on where a route leaves our AS, and taken off there:
  // to a peer in our own AS a route goes with them, for that router to act
  // on. They are honoured on routes we originate too (`communities` and
  // `large_communities` of `originate`), on what import.add_communities
  // puts on, and on what a peer in our own AS, or one with
  // import.accept_control_communities, sends. From any other peer the
  // communities of our own AS are taken off as its routes come in, so that
  // nobody outside can say what is done with our routes.
  //
  // With this on, standard communities L:n are taken for "to the peer
  // with AS n": mark routes with something else (large communities
  // L:100:n and up, say; functions 2 to 9 are left for marks too).
  bool control_communities = 13;

  // Graceful restart, for every peer that has no `graceful_restart` of its
  // own. Left out, it is on, as the defaults below have it.
  GracefulRestart graceful_restart = 14;

  // Where this router passes on routes from one router of our AS to
  // another (Peer.route_reflector_client), the cluster it does so for, as
  // a dotted-quad: what it puts on such routes, and what it does not take
  // back (RFC 4456). Give routers that serve the same clients the same
  // cluster ID. Defaults to router_id.
  string cluster_id = 15;

  // Limits on what goes to other networks that are not our customers: to
  // every peer whose role is PROVIDER, PEER or ROUTE_SERVER, and to one
  // in another AS that has no role. Not to customers, route server
  // clients or routers of our own AS. A peer's own `export_limits` takes
  // the place of these.
  //
  // They hold whatever the routes are and wherever they came from, and
  // whatever `export` says: a check on everything else, in case it goes
  // wrong. With the roles, a route learned from a provider or a peer is
  // passed on to customers only; these keep it from going further even
  // if a route is not marked as it should be.
  ExportLimits export_limits = 16;

  // Names for communities, for the status page to show in place of the
  // numbers: what the marks on routes mean to a reader. A name for one
  // community ("64601:100:2" is "comrack"), or for a kind of them, with
  // `*` for the part left open ("64601:102:*" is "interconnection"), which
  // is shown with the open part after the name. The daemon itself does
  // nothing with them.
  repeated CommunityName community_names = 17;
}

// A name for a community, or for a kind of them.
message CommunityName {
  // The community, standard ("64601:100") or large ("64601:100:2"), or a
  // pattern of them with `*` for a part left open ("64601:102:*").
  string community = 1;
  // What it is shown as.
  string name = 2;
}

// Limits on what is announced to a peer, which hold whatever `export`
// and the routes say.
message ExportLimits {
  // Only routes for these prefixes are announced: our own address space
  // and our customers', say, with max_length as long as the longest
  // prefix announced from it. Routes for other prefixes, learned or
  // originated, are not. Empty allows any.
  repeated PrefixRange prefixes = 1;

  // The most routes that are announced to the peer at a time. If more
  // were to be, none of them is: the session is ended with a Cease /
  // Administrative Shutdown NOTIFICATION that says why (RFC 9003), and the
  // peer is kept down for its import.hold_down_seconds, as when it sends
  // us too many. Set it somewhat above what is expected. Zero is no
  // limit.
  uint32 max_prefixes = 2;
}

// Graceful restart (RFC 4724): BGP restarting without the routes going.
//
// When the daemon is restarted in good order for an upgrade (on SIGUSR1),
// it leaves its routes in the kernel, and its peers keep the routes it
// announced to them, for as long as they were told a restart takes. When a
// peer restarts, its routes are kept and used as before, marked stale,
// until it has sent them again; those it does not send again are removed.
// Either way, nothing is withdrawn across the network for a restart.
//
// It is in use with a peer that offers it too. A session that ends with a
// Hard Reset (RFC 8538), or because of an error, has its routes removed at
// once, as without graceful restart.
message GracefulRestart {
  // True does not offer graceful restart: a peer's routes are removed as
  // soon as its session ends, and it removes ours as soon as it sees ours
  // end.
  optional bool disabled = 1;

  // How long, in seconds, peers are told a restart of this daemon takes:
  // how long they keep our routes after our session with them ends. At
  // most 4095. Defaults to 120.
  optional uint32 restart_time_seconds = 2;

  // The longest time, in seconds, a restarting peer's routes are kept
  // stale: while it is gone, whatever restart time it gave, and again once
  // it is back, until it has sent all its routes. Zero keeps none.
  // Defaults to 120.
  optional uint32 stale_routes_seconds = 3;
}

// Installing routes in the kernel. Linux only; the daemon needs the
// CAP_NET_ADMIN capability.
//
// The best route of a prefix is installed if its next hop is a neighbor:
// an address in the network of one of the machine's interfaces. Routes
// are marked as BGP's ("proto bgp"), and every route with that mark, the
// table and the metric below is taken to be this daemon's: what it finds
// at startup and no longer wants, it removes. When the daemon stops in
// good order it removes its routes.
message Kernel {
  // The routing table. Defaults to 254, the main table, which is the one
  // packets are forwarded by unless rules say otherwise.
  uint32 table = 1;

  // The metric of the routes. Defaults to 20. Of several routes for a
  // prefix the kernel uses the one with the lowest metric.
  optional uint32 metric = 2;

  // By default, where the kernel has nexthop objects (Linux 5.3 and
  // later), a gateway is put there once as such an object and routes name
  // it, which makes installing a full table about a third faster. `ip
  // route` then shows routes with "nhid". True has every route carry its
  // own gateway, as on older kernels.
  bool without_nexthop_objects = 3;

  // How long, after the daemon starts, routes of its own that an earlier
  // run left in the kernel are kept though no peer has announced them
  // (again). Defaults to 120. The daemon's table is empty until its peers
  // have sent theirs; removing the old routes at once would stop the
  // machine forwarding for as long as that takes. After this time, what
  // was not announced again is removed.
  // Zero removes them at once.
  optional uint32 stale_seconds = 4;

  // The kernel's table whose routes say how a next hop that is not a
  // neighbour is reached: its connected and static routes, and an IGP's
  // if there is one. Defaults to 254, the main table. A route whose next
  // hop is covered by such a route is installed with that route's gateway
  // and interface, the kernel not looking gateways up in turn. Routes put
  // in the table by BGP, this daemon's or another's, never count: a next
  // hop reached only by way of a BGP route rests on what may itself rest
  // on a next hop.
  uint32 resolution_table = 5;

  // Whether the default route in that table counts as the way to a next
  // hop. Off by default: on a router the default route points at a
  // transit provider, and a next hop "reached" only by sending the
  // packets to the Internet at large is not reached.
  bool resolve_via_default_route = 6;
}

// Where to get the validated ROA payloads that say which AS may originate
// which prefixes. With this set, a route whose origin is not authorised
// for its prefix ("invalid") is refused, from every peer that is not in
// our own AS and does not have accept_rpki_invalid set. Routes that
// nothing is known about are taken as before.
//
// A validator that speaks version 2 of the protocol also gives the ASPAs,
// in which networks say who their providers are. With those, a route
// whose AS path cannot have come about by networks passing routes on as
// they should (a route leak, or a made-up path) is refused, from every
// peer that has a role set and does not have accept_aspa_invalid set.
message Rpki {
  // The RPKI-to-Router servers (RFC 8210, draft-ietf-sidrops-8210bis) of
  // one or more validators, such as Routinator, rpki-client with StayRTR,
  // or FORT, in order of preference. The port is required. One is used at
  // a time, over plain TCP: keep it on a network you trust.
  repeated TcpEndpoint caches = 1;

  // How often to ask the cache for changes unprompted, how long to wait
  // before trying again after a failure, and how long the data may be used
  // without a cache confirming it, after which nothing is invalid any
  // more. Each defaults to what the cache says, or to 3600, 600 and 7200.
  uint32 refresh_seconds = 2;
  uint32 retry_seconds = 3;
  uint32 expire_seconds = 4;
}

// A route originated by this router. It is announced with an AS_PATH of the
// local AS (empty, to a peer in our own AS) and, on each session, that
// session's local address as next hop.
message OriginatedRoute {
  // The prefix in CIDR notation, e.g. "192.0.2.0/24" or "2001:db8::/32".
  string prefix = 1;

  // ORIGIN attribute: "IGP" (the default), "EGP" or "INCOMPLETE".
  string origin = 2;

  // Extra copies of the local AS to prepend to the AS_PATH. At most 16.
  uint32 as_path_prepend = 3;

  // MULTI_EXIT_DISC. Left out of the announcement when unset.
  optional uint32 med = 4;

  // Standard communities (RFC 1997): "ASN:VALUE", or a well-known name such
  // as "NO_EXPORT".
  repeated string communities = 5;

  // Large communities (RFC 8092): "GLOBAL:LOCAL1:LOCAL2".
  repeated string large_communities = 6;
}

// An IP address and port pair.
message TcpEndpoint {
  // IP address (V4 or V6). A peer at a link-local IPv6 address has the
  // interface it is on after it: "fe80::1%eth0".
  string address = 1;
  // TCP port. Defaults to 179 for BGP when unset.
  uint32 port = 2;
}

// Configuration of a BGP peer.
message Peer {
  // Human-readable name for logging and diagnostics.
  string name = 1;

  // Address and port to connect to for this peer.
  TcpEndpoint endpoint = 2;

  // The peer's 4-byte AS number (RFC 6793).
  uint32 remote_asn = 3;

  // Hold time to advertise in the OPEN message, in seconds (RFC 4271 §4.2).
  // At least 3, or 0 for a session without keepalives that is never timed
  // out. Defaults to 90 when unset.
  optional uint32 hold_time_seconds = 4;

  // Source IP address for connections we open to this peer. It is also the
  // next hop of the routes we send it. Required when the peer identifies us
  // by address and the host has several, e.g. when both speakers run on the
  // same machine. Must be the same address family as the endpoint. Unset
  // lets the operating system choose.
  string local_address = 5;

  // The address families to exchange with this peer. Each is offered to the
  // peer in our OPEN, and is in use on the session only if the peer offers
  // it too (RFC 4760). Defaults to all of them when empty. A session with
  // no family in common is refused.
  repeated AddressFamily address_families = 6;

  // ADD-PATH (RFC 7911): whether to take several routes for one prefix
  // from this peer, to send it several, or both. It is in use, for each
  // direction and address family, only if the peer agrees. Defaults to
  // off: one route for each prefix, as in plain BGP.
  AddPath add_path = 7;

  // Which of the peer's routes are taken. Left out, the general checks
  // apply and there is no limit and no list.
  ImportPolicy import = 8;

  // What the peer is to us. Not for a peer in our own AS. With it set:
  //
  // - Our OPEN says what we are to the peer, and a peer that says it is
  //   something else than configured here is refused (RFC 9234). One side
  //   having the other down as a customer and the other as a peer is how
  //   leaks come about.
  // - Routes are marked "only to customer" as they come in from a provider,
  //   a peer or a route server, and as they go out to a customer, a peer
  //   or a route server client. A route with that mark that comes back up
  //   from a customer, or across from a second peer, is a leak and is
  //   refused. This cannot be turned off.
  // - Where rpki is configured, the AS paths of the peer's routes are
  //   verified against the ASPAs: a route from a customer, a peer or a
  //   route server must have come up through providers all the way; one
  //   from a provider may have come up and then down.
  //
  // Left out, none of this is done for the peer.
  Role role = 9;

  // Refuse the peer unless its OPEN says what it is. By default a peer
  // that says nothing (one that does not implement RFC 9234) is taken at
  // this configuration's word for it. Needs role.
  bool require_role = 10;

  // What is announced to the peer, and how. Left out, the top-level
  // `export` holds, and without that the routes we originate are
  // announced as they are.
  ExportPolicy export = 11;

  // Graceful restart with this peer. What is set here takes the place of
  // what the top-level `graceful_restart` says.
  GracefulRestart graceful_restart = 12;

  // The groups the session is in, by number, for control communities to
  // name sessions by (see control_communities): those at one Internet
  // exchange, say, or those over one link, whatever AS the peers are. Use
  // the same numbers on all routers of the AS: a route marked on one is
  // acted on by another. From 1.
  repeated uint32 groups = 13;

  // Pass on to this peer, a router of our own AS, the routes learned from
  // our other routers, and pass on the routes it sends to all of them: we
  // are its route reflector (RFC 4456). Without it, as BGP has it, a route
  // learned from one router of our AS goes to no other, and every router
  // needs a session with every other. Routes go with this router as next
  // hop, so that the peer can reach what lies behind another router
  // through this one. Only for a peer in our own AS: other networks are
  // told of learned routes by `export` and the roles alone. The peer's
  // `export` still has to pass on learned routes.
  bool route_reflector_client = 14;

  // Limits on what is announced to the peer, in the place of the
  // top-level export_limits. They apply to the same peers as those do: to
  // one whose role is PROVIDER, PEER or ROUTE_SERVER, or that is in
  // another AS and has no role.
  ExportLimits export_limits = 15;

  // Do not open connections to the peer: wait for it to connect. The
  // session is configured in full, and comes up when the peer connects
  // from `endpoint`'s address; the port of `endpoint` is not used. For a
  // new peer whose side is not ready yet, or one that is to open the
  // connections itself.
  bool passive = 16;

  // About how many routes the peer sends when all is well: a full table,
  // a few hundred from an exchange peer, one from a customer. Nothing is
  // decided by it. The status page compares the routes the peer has in
  // the table with it, and shows an established session with fewer than
  // half as needing attention: a peer that is up but has sent next to
  // nothing looks, without this, exactly like one that is fine. Zero, the
  // default, compares nothing. The routing table is also made with room
  // for the largest of these from the start, so that it need not grow,
  // and so use twice its memory for a moment, while the tables come in.
  uint32 expected_routes = 17;
}

// What is announced to a peer.
//
// The routes we originate are always announced. Routes learned from other
// peers are passed on only if learned_routes says so, and then only as
// far as these let them:
//
// - Never back to the peer a route came from, nor to a peer whose AS is
//   on its path already.
// - A route from a peer in our own AS is not passed to another such peer,
//   unless one of them is a route reflector client of ours
//   (Peer.route_reflector_client).
// - Where peers have roles (RFC 9234): a route learned from a provider, a
//   peer or a route server goes on to customers only. So with roles on
//   all peers, turning this on makes us transit for our customers and for
//   nobody else. Without roles there is no such rule, and every route
//   goes to every peer: do not turn this on for a peer without a role
//   unless that is what is wanted.
// - The communities NO_EXPORT and NO_ADVERTISE, and control_communities.
//
// A route is passed on with our AS added to its path and ourselves as
// next hop, without the MED it came with. To a peer in our own AS the
// path is left as it is and LOCAL_PREF goes along. To a peer whose role
// is ROUTE_SERVER_CLIENT the route goes as a route server sends it
// (RFC 7947): path, MED and, where the client can use it, next hop
// unchanged.
message ExportPolicy {
  // Pass on the best routes learned from other peers.
  bool learned_routes = 1;

  // Communities put on every route announced to the peer: which router
  // it went through, say. "64601:100", or a well-known name.
  repeated string add_communities = 2;

  // Large communities put on, as "64601:1:2".
  repeated string add_large_communities = 3;

  // Communities taken off first: one ("64601:100"), all of an AS
  // ("64601:*"), or large ones with three parts ("64601:1:*").
  repeated string remove_communities = 4;

  // How many more times our AS is put on the path of every route
  // announced to the peer, to make them look further away. At most 16.
  uint32 as_path_prepend = 5;
}

// What a peer is to us.
enum Role {
  ROLE_UNSPECIFIED = 0;
  // We buy transit from the peer.
  PROVIDER = 1;
  // The peer buys transit from us.
  CUSTOMER = 2;
  // The peer and we exchange our own and our customers' routes.
  PEER = 3;
  // The peer is an Internet exchange's route server.
  ROUTE_SERVER = 4;
  // We are a route server and the peer is one of our clients.
  ROUTE_SERVER_CLIENT = 5;
}

// What is taken from a peer. Every route is judged before it goes into
// the routing table. One that is refused is dropped, and so is the route
// it would have replaced.
//
// A route whose AS path holds our own AS number is always refused.
message ImportPolicy {
  // The most routes the peer may have at a time. One more ends the session
  // with Cease / Maximum Number of Prefixes Reached, and the peer is kept
  // down for hold_down_seconds. Set it somewhat above what the peer is
  // expected to send. Zero is no limit.
  uint32 max_prefixes = 1;

  // How long the peer is kept down after going over max_prefixes. Neither
  // side's connections are taken meanwhile. Defaults to 600.
  uint32 hold_down_seconds = 2;

  // By default, prefixes that are not routed on the Internet are refused
  // (private, loopback, link-local, documentation, multicast and reserved
  // space), and so are routes with a reserved, private or documentation AS
  // number anywhere in their path. True takes them.
  bool accept_bogons = 3;

  // By default a default route (0.0.0.0/0 or ::/0) is refused. True takes
  // one, as from an upstream that is asked to send it.
  bool accept_default_route = 4;

  // The longest prefixes taken. Defaults to 24 and 48, the longest that are
  // routed between networks.
  uint32 max_ipv4_prefix_length = 5;
  uint32 max_ipv6_prefix_length = 6;

  // By default the AS path of a route has to begin with the peer's own AS
  // number. True takes any, as is needed for an Internet exchange's route
  // server, which does not put its AS on the path.
  bool accept_any_first_as = 7;

  // The longest AS path taken, counted in AS numbers. Defaults to 64.
  uint32 max_as_path_length = 8;

  // The prefixes the peer may announce. Empty allows any. This is the
  // list generated for a peer from the routing registries (with bgpq4,
  // say).
  repeated PrefixRange prefixes = 9;

  // The AS numbers the peer's routes may originate from: the last AS of
  // the path. Empty allows any.
  repeated uint32 origin_asns = 10;

  // By default, where route origin validation is configured (rpki), a
  // route that is invalid is refused. True takes it all the same.
  bool accept_rpki_invalid = 11;

  // By default, where the validator gives ASPAs and the peer has a role,
  // a route whose AS path they find invalid is refused. True takes it all
  // the same.
  bool accept_aspa_invalid = 12;

  // By default a route whose AS path has an AS_SET in it is refused: sets
  // are deprecated (RFC 9774), and with one nobody can say where a route
  // comes from. True takes such routes.
  bool accept_as_sets = 13;

  // By default the next hop of a route from another network has to be the
  // peer itself, so that a peer can only draw traffic to itself and not
  // send it to a third party. True takes any next hop packets can be sent
  // to. Not needed for a peer whose role is ROUTE_SERVER, whose routes
  // have its clients as next hops.
  bool accept_third_party_next_hop = 14;

  // Communities put on every route taken from the peer: where it was
  // learned, say, for other routers of ours and for `export` to go by.
  // "64601:100", or a well-known name.
  repeated string add_communities = 15;

  // Large communities put on, as "64601:1:2".
  repeated string add_large_communities = 16;

  // Communities taken off first: one ("64601:100"), all of an AS
  // ("64601:*"), or large ones with three parts ("64601:1:*"). Marks that
  // mean something to us are not to be taken on a peer's word.
  repeated string remove_communities = 17;

  // The LOCAL_PREF of the peer's routes: of two routes for a prefix the
  // one with the higher is chosen, whatever else they have. Left out, 100.
  optional uint32 local_pref = 18;

  // By default the communities of our own AS (L:n and L:n:m; and 0:n,
  // with control_communities on) are taken off the routes of a peer in
  // another AS as they come in, before add_communities puts ours on: what
  // they ask of us is not for others to ask. True keeps them, for a
  // customer that is to steer its own routes with control communities, or
  // a route server's client. Not for a peer in our own AS, whose routes
  // keep them in any case.
  bool accept_control_communities = 19;

  // What is done to some of the routes, beyond what is done to all of
  // them above. Each route that is taken is looked at by the rules in
  // turn, and the first that holds for it is applied; the rest are not
  // looked at. A rule sees the route as the statements above leave it:
  // with our communities taken off and ours put on.
  repeated ImportRule rules = 20;

  // By default a route with the BLACKHOLE community (65535:666, RFC
  // 7999), which asks for the traffic to its prefix to be dropped, is
  // refused ("blackhole request"). True takes such a route if it is for
  // one address (a /32 or /128), whatever the longest prefix taken
  // otherwise, and inside what the peer may announce; its next hop is
  // not looked at. The traffic to the address is then dropped by this
  // router (a blackhole route in the kernel), and the route goes on to
  // the peers the export policy sends it to, community and all, for them
  // to do the same. For a customer under attack, and for a route server
  // whose blackhole routes are to be honoured.
  bool accept_blackholes = 21;
}

// What is done to the routes with some communities, or for some prefixes:
// those learned at one exchange, say, by the mark another router of ours
// put on them, to be preferred less; or one prefix of a customer's, to be
// marked for a prepend.
message ImportRule {
  // The rule holds for routes with one of these communities: one
  // ("64601:100"), all of an AS ("64601:*"), or large ones with three
  // parts ("64601:101:*"). Left out, for routes with any.
  repeated string match_communities = 1;

  // And for routes for a prefix in these. Left out, for any prefix.
  repeated PrefixRange match_prefixes = 2;

  // The LOCAL_PREF of the routes, in place of import.local_pref.
  optional uint32 local_pref = 3;

  // Communities put on the routes.
  repeated string add_communities = 4;
  repeated string add_large_communities = 5;
}

// A prefix, and optionally the more specific prefixes inside it.
message PrefixRange {
  // In CIDR notation, e.g. "193.0.0.0/21".
  string prefix = 1;
  // The longest prefix inside it that is also allowed. Left out, only the
  // prefix itself is.
  uint32 max_length = 2;
}

// The directions ADD-PATH can be offered for.
enum AddPath {
  ADD_PATH_OFF = 0;
  // Accept several routes for a prefix from the peer.
  ADD_PATH_RECEIVE = 1;
  // Offer to send the peer several routes for a prefix. As yet only the
  // best is sent all the same.
  ADD_PATH_SEND = 2;
  ADD_PATH_BOTH = 3;
}

// An address family routes can be exchanged for.
enum AddressFamily {
  ADDRESS_FAMILY_UNSPECIFIED = 0;
  IPV4_UNICAST = 1;
  IPV6_UNICAST = 2;
}