86 lines
3.5 KiB
Go
86 lines
3.5 KiB
Go
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package krpc
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import (
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"fmt"
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)
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// Msg represents messages that nodes in the network send to each other as specified by the protocol.
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// They are also refered to as the KRPC messages.
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// There are three types of messages: QUERY, RESPONSE, ERROR
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// The message is a dictonary that is then
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// "bencoded" (serialization & compression format adopted by the BitTorrent)
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// and sent via the UDP connection to peers.
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//
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// A KRPC message is a single dictionary with two keys common to every message and additional keys depending on the type of message.
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// Every message has a key "t" with a string value representing a transaction ID.
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// This transaction ID is generated by the querying node and is echoed in the response, so responses
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// may be correlated with multiple queries to the same node. The transaction ID should be encoded as a short string of binary numbers, typically 2 characters are enough as they cover 2^16 outstanding queries. The other key contained in every KRPC message is "y" with a single character value describing the type of message. The value of the "y" key is one of "q" for query, "r" for response, or "e" for error.
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// 3 message types: QUERY, RESPONSE, ERROR
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type Msg struct {
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Q string `bencode:"q,omitempty"` // Query method (one of 4: "ping", "find_node", "get_peers", "announce_peer")
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A *MsgArgs `bencode:"a,omitempty"` // named arguments sent with a query
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T string `bencode:"t"` // required: transaction ID
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Y string `bencode:"y"` // required: type of the message: q for QUERY, r for RESPONSE, e for ERROR
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R *Return `bencode:"r,omitempty"` // RESPONSE type only
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E *Error `bencode:"e,omitempty"` // ERROR type only
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IP NodeAddr `bencode:"ip,omitempty"`
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ReadOnly bool `bencode:"ro,omitempty"`
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}
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type MsgArgs struct {
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ID ID `bencode:"id"` // ID of the querying Node
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InfoHash ID `bencode:"info_hash,omitempty"` // InfoHash of the torrent
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Target ID `bencode:"target,omitempty"` // ID of the node sought
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Token string `bencode:"token,omitempty"` // Token received from an earlier get_peers query
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Port int `bencode:"port,omitempty"` // Senders torrent port
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ImpliedPort bool `bencode:"implied_port,omitempty"` // Use senders apparent DHT port
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Want []Want `bencode:"want,omitempty"` // Contains strings like "n4" and "n6" from BEP 32.
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}
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type Want string
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const (
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WantNodes Want = "n4"
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WantNodes6 Want = "n6"
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)
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type Return struct {
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ID ID `bencode:"id"` // ID of the querying node
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Nodes CompactIPv4NodeInfo `bencode:"nodes,omitempty"` // K closest nodes to the requested target
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Nodes6 CompactIPv6NodeInfo `bencode:"nodes6,omitempty"` // K closest nodes to the requested target
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Token string `bencode:"token,omitempty"` // Token for future announce_peer
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Values []NodeAddr `bencode:"values,omitempty"` // Torrent peers
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}
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var _ fmt.Stringer = Msg{}
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func (m Msg) String() string {
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return fmt.Sprintf("%#v", m)
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}
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// The node ID of the source of this Msg. Returns nil if it isn't present.
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// TODO: Can we verify Msgs more aggressively so this is guaranteed to return
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// a valid ID for a checked Msg?
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func (m Msg) SenderID() *ID {
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switch m.Y {
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case "q":
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if m.A == nil {
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return nil
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}
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return &m.A.ID
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case "r":
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if m.R == nil {
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return nil
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}
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return &m.R.ID
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}
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return nil
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}
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func (m Msg) Error() *Error {
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if m.Y != "e" {
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return nil
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}
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return m.E
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}
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