8 "github.com/anacrolix/missinggo"
10 "github.com/anacrolix/torrent/metainfo"
13 type ExtensionBit uint
16 ExtensionBitDHT = 0 // http://www.bittorrent.org/beps/bep_0005.html
17 ExtensionBitExtended = 20 // http://www.bittorrent.org/beps/bep_0010.html
18 ExtensionBitFast = 2 // http://www.bittorrent.org/beps/bep_0006.html
21 func handshakeWriter(w io.Writer, bb <-chan []byte, done chan<- error) {
33 PeerExtensionBits [8]byte
36 func (me PeerExtensionBits) String() string {
37 return hex.EncodeToString(me[:])
40 func NewPeerExtensionBytes(bits ...ExtensionBit) (ret PeerExtensionBits) {
41 for _, b := range bits {
47 func (pex PeerExtensionBits) SupportsExtended() bool {
48 return pex.GetBit(ExtensionBitExtended)
51 func (pex PeerExtensionBits) SupportsDHT() bool {
52 return pex.GetBit(ExtensionBitDHT)
55 func (pex PeerExtensionBits) SupportsFast() bool {
56 return pex.GetBit(ExtensionBitFast)
59 func (pex *PeerExtensionBits) SetBit(bit ExtensionBit) {
60 pex[7-bit/8] |= 1 << (bit % 8)
63 func (pex PeerExtensionBits) GetBit(bit ExtensionBit) bool {
64 return pex[7-bit/8]&(1<<(bit%8)) != 0
67 type HandshakeResult struct {
73 // ih is nil if we expect the peer to declare the InfoHash, such as when the
74 // peer initiated the connection. Returns ok if the Handshake was successful,
75 // and err if there was an unexpected condition other than the peer simply
76 // abandoning the Handshake.
77 func Handshake(sock io.ReadWriter, ih *metainfo.Hash, peerID [20]byte, extensions PeerExtensionBits) (res HandshakeResult, ok bool, err error) {
78 // Bytes to be sent to the peer. Should never block the sender.
79 postCh := make(chan []byte, 4)
80 // A single error value sent when the writer completes.
81 writeDone := make(chan error, 1)
82 // Performs writes to the socket and ensures posts don't block.
83 go handshakeWriter(sock, postCh, writeDone)
86 close(postCh) // Done writing.
93 // Wait until writes complete before returning from handshake.
96 err = fmt.Errorf("error writing: %s", err)
100 post := func(bb []byte) {
104 panic("mustn't block while posting")
108 post([]byte(Protocol))
110 if ih != nil { // We already know what we want.
115 _, err = io.ReadFull(sock, b[:68])
120 if string(b[:20]) != Protocol {
123 missinggo.CopyExact(&res.PeerExtensionBits, b[20:28])
124 missinggo.CopyExact(&res.Hash, b[28:48])
125 missinggo.CopyExact(&res.PeerID, b[48:68])
126 // peerExtensions.Add(res.PeerExtensionBits.String(), 1)
128 // TODO: Maybe we can just drop peers here if we're not interested. This
129 // could prevent them trying to reconnect, falsely believing there was
131 if ih == nil { // We were waiting for the peer to tell us what they wanted.