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msg.go
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msg.go
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package krpc
import (
"github.com/anacrolix/torrent/bencode"
)
// Msg represents messages that nodes in the network send to each other as specified by the protocol.
// They are also referred to as the KRPC messages.
// There are three types of messages: QUERY, RESPONSE, ERROR
// The message is a dictionary that is then
// "bencoded" (serialization & compression format adopted by the BitTorrent)
// and sent via the UDP connection to peers.
//
// A KRPC message is a single dictionary with two keys common to every message and additional keys depending on the type of message.
// Every message has a key "t" with a string value representing a transaction ID.
// This transaction ID is generated by the querying node and is echoed in the response, so responses
// 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.
// 3 message types: QUERY, RESPONSE, ERROR
type Msg struct {
Q string `bencode:"q,omitempty"` // Query method (one of 4: "ping", "find_node", "get_peers", "announce_peer")
A *MsgArgs `bencode:"a,omitempty"` // named arguments sent with a query
T string `bencode:"t"` // required: transaction ID
Y string `bencode:"y"` // required: type of the message: q for QUERY, r for RESPONSE, e for ERROR
R *Return `bencode:"r,omitempty"` // RESPONSE type only
E *Error `bencode:"e,omitempty"` // ERROR type only
IP NodeAddr `bencode:"ip,omitempty"`
ReadOnly bool `bencode:"ro,omitempty"` // BEP 43. Sender does not respond to queries.
}
type MsgArgs struct {
ID ID `bencode:"id"` // ID of the querying Node
InfoHash ID `bencode:"info_hash,omitempty"` // InfoHash of the torrent
Target ID `bencode:"target,omitempty"` // ID of the node sought
// Token received from an earlier get_peers query. Also used in a BEP 44 put.
Token string `bencode:"token,omitempty"`
Port *int `bencode:"port,omitempty"` // Sender's torrent port
ImpliedPort bool `bencode:"implied_port,omitempty"` // Use senders apparent DHT port
Want []Want `bencode:"want,omitempty"` // Contains strings like "n4" and "n6" from BEP 32.
NoSeed int `bencode:"noseed,omitempty"` // BEP 33
Scrape int `bencode:"scrape,omitempty"` // BEP 33
// BEP 44
// I don't know if we should use bencode.Bytes for this. If we unmarshalled bytes that didn't
// marshal back the same, our hashes will not match. But this might also serve to prevent abuse.
V interface{} `bencode:"v,omitempty"`
Seq *int64 `bencode:"seq,omitempty"`
Cas int64 `bencode:"cas,omitempty"`
K [32]byte `bencode:"k,omitempty"`
Salt []byte `bencode:"salt,omitempty"`
Sig [64]byte `bencode:"sig,omitempty"`
}
type Want string
const (
WantNodes Want = "n4"
WantNodes6 Want = "n6"
)
// BEP 51 (DHT Infohash Indexing)
type Bep51Return struct {
Interval *int64 `bencode:"interval,omitempty"`
Num *int64 `bencode:"num,omitempty"`
// Nodes supporting this extension should always include the samples field in the response, even
// when it is zero-length. This lets indexing nodes to distinguish nodes supporting this
// extension from those that respond to unknown query types which contain a target field [2].
Samples *CompactInfohashes `bencode:"samples,omitempty"`
}
type Bep44Return struct {
V bencode.Bytes `bencode:"v,omitempty"`
K [32]byte `bencode:"k,omitempty"`
Sig [64]byte `bencode:"sig,omitempty"`
Seq *int64 `bencode:"seq,omitempty"`
}
type Return struct {
// All returns are supposed to contain an ID, but what if they don't?
ID ID `bencode:"id"` // ID of the queried (and responding) node
// K closest nodes to the requested target. Included in responses to queries that imply
// traversal, for example get_peers, find_nodes, get, sample_infohashes.
Nodes CompactIPv4NodeInfo `bencode:"nodes,omitempty"`
Nodes6 CompactIPv6NodeInfo `bencode:"nodes6,omitempty"`
Token *string `bencode:"token,omitempty"` // Token for future announce_peer or put (BEP 44)
Values []NodeAddr `bencode:"values,omitempty"` // Torrent peers
// BEP 33 (scrapes)
BFsd *ScrapeBloomFilter `bencode:"BFsd,omitempty"`
BFpe *ScrapeBloomFilter `bencode:"BFpe,omitempty"`
Bep51Return
// BEP 44
Bep44Return
}
func (r Return) ForAllNodes(f func(NodeInfo)) {
for _, n := range r.Nodes {
f(n)
}
for _, n := range r.Nodes6 {
f(n)
}
}
// The node ID of the source of this Msg. Returns nil if it isn't present.
// TODO: Can we verify Msgs more aggressively so this is guaranteed to return
// a valid ID for a checked Msg?
func (m Msg) SenderID() *ID {
switch m.Y {
case "q":
if m.A == nil {
return nil
}
return &m.A.ID
case "r":
if m.R == nil {
return nil
}
return &m.R.ID
}
return nil
}
// This does not return an error, but (*Error)(nil) is still a non-nil error. You have been warned!
// This language is evil.
func (m Msg) Error() *Error {
if m.Y != "e" {
return nil
}
return m.E
}