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;
}

// A route originated by this router. It is announced with an AS_PATH of the
// local 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).
  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).
  // Must be 0 or >= 3. Defaults to 90 when unset.
  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;
}

// 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;
  // Send the peer several routes for a prefix.
  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;
}