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client.go
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client.go
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package torrent
import (
"bufio"
"bytes"
"crypto/rand"
"crypto/sha1"
"encoding/hex"
"errors"
"expvar"
"fmt"
"io"
"log"
"math/big"
mathRand "math/rand"
"net"
"net/url"
"os"
"path/filepath"
"sort"
"strconv"
"strings"
"time"
"github.com/anacrolix/missinggo"
. "github.com/anacrolix/missinggo"
"github.com/anacrolix/missinggo/bitmap"
"github.com/anacrolix/missinggo/pproffd"
"github.com/anacrolix/missinggo/pubsub"
"github.com/anacrolix/sync"
"github.com/anacrolix/utp"
"github.com/edsrzf/mmap-go"
"github.com/michaeldye/torrent/bencode"
filePkg "github.com/michaeldye/torrent/data/file"
"github.com/michaeldye/torrent/dht"
"github.com/michaeldye/torrent/iplist"
"github.com/michaeldye/torrent/metainfo"
"github.com/michaeldye/torrent/mse"
pp "github.com/michaeldye/torrent/peer_protocol"
"github.com/michaeldye/torrent/tracker"
)
// I could move a lot of these counters to their own file, but I suspect they
// may be attached to a Client someday.
var (
unwantedChunksReceived = expvar.NewInt("chunksReceivedUnwanted")
unexpectedChunksReceived = expvar.NewInt("chunksReceivedUnexpected")
chunksReceived = expvar.NewInt("chunksReceived")
peersAddedBySource = expvar.NewMap("peersAddedBySource")
uploadChunksPosted = expvar.NewInt("uploadChunksPosted")
unexpectedCancels = expvar.NewInt("unexpectedCancels")
postedCancels = expvar.NewInt("postedCancels")
duplicateConnsAvoided = expvar.NewInt("duplicateConnsAvoided")
pieceHashedCorrect = expvar.NewInt("pieceHashedCorrect")
pieceHashedNotCorrect = expvar.NewInt("pieceHashedNotCorrect")
unsuccessfulDials = expvar.NewInt("dialSuccessful")
successfulDials = expvar.NewInt("dialUnsuccessful")
acceptUTP = expvar.NewInt("acceptUTP")
acceptTCP = expvar.NewInt("acceptTCP")
acceptReject = expvar.NewInt("acceptReject")
peerExtensions = expvar.NewMap("peerExtensions")
completedHandshakeConnectionFlags = expvar.NewMap("completedHandshakeConnectionFlags")
// Count of connections to peer with same client ID.
connsToSelf = expvar.NewInt("connsToSelf")
// Number of completed connections to a client we're already connected with.
duplicateClientConns = expvar.NewInt("duplicateClientConns")
receivedMessageTypes = expvar.NewMap("receivedMessageTypes")
receivedKeepalives = expvar.NewInt("receivedKeepalives")
supportedExtensionMessages = expvar.NewMap("supportedExtensionMessages")
postedMessageTypes = expvar.NewMap("postedMessageTypes")
postedKeepalives = expvar.NewInt("postedKeepalives")
// Requests received for pieces we don't have.
requestsReceivedForMissingPieces = expvar.NewInt("requestsReceivedForMissingPieces")
)
const (
// Justification for set bits follows.
//
// Extension protocol ([5]|=0x10):
// http://www.bittorrent.org/beps/bep_0010.html
//
// Fast Extension ([7]|=0x04):
// http://bittorrent.org/beps/bep_0006.html.
// Disabled until AllowedFast is implemented.
//
// DHT ([7]|=1):
// http://www.bittorrent.org/beps/bep_0005.html
defaultExtensionBytes = "\x00\x00\x00\x00\x00\x10\x00\x01"
socketsPerTorrent = 15
torrentPeersHighWater = 200
torrentPeersLowWater = 50
// Limit how long handshake can take. This is to reduce the lingering
// impact of a few bad apples. 4s loses 1% of successful handshakes that
// are obtained with 60s timeout, and 5% of unsuccessful handshakes.
btHandshakeTimeout = 4 * time.Second
handshakesTimeout = 20 * time.Second
// These are our extended message IDs.
metadataExtendedId = iota + 1 // 0 is reserved for deleting keys
pexExtendedId
// Updated occasionally to when there's been some changes to client
// behaviour in case other clients are assuming anything of us. See also
// `bep20`.
extendedHandshakeClientVersion = "go.torrent dev 20150624"
)
// Currently doesn't really queue, but should in the future.
func (cl *Client) queuePieceCheck(t *torrent, pieceIndex int) {
piece := &t.Pieces[pieceIndex]
if piece.QueuedForHash {
return
}
piece.QueuedForHash = true
t.publishPieceChange(int(pieceIndex))
go cl.verifyPiece(t, int(pieceIndex))
}
// Queue a piece check if one isn't already queued, and the piece has never
// been checked before.
func (cl *Client) queueFirstHash(t *torrent, piece int) {
p := &t.Pieces[piece]
if p.EverHashed || p.Hashing || p.QueuedForHash || t.pieceComplete(piece) {
return
}
cl.queuePieceCheck(t, piece)
}
// Clients contain zero or more Torrents. A client manages a blocklist, the
// TCP/UDP protocol ports, and DHT as desired.
type Client struct {
halfOpenLimit int
peerID [20]byte
listeners []net.Listener
utpSock *utp.Socket
dHT *dht.Server
ipBlockList iplist.Ranger
bannedTorrents map[InfoHash]struct{}
config Config
pruneTimer *time.Timer
extensionBytes peerExtensionBytes
// Set of addresses that have our client ID. This intentionally will
// include ourselves if we end up trying to connect to our own address
// through legitimate channels.
dopplegangerAddrs map[string]struct{}
torrentDataOpener TorrentDataOpener
mu sync.RWMutex
event sync.Cond
closed missinggo.Event
torrents map[InfoHash]*torrent
}
func (me *Client) IPBlockList() iplist.Ranger {
me.mu.Lock()
defer me.mu.Unlock()
return me.ipBlockList
}
func (me *Client) SetIPBlockList(list iplist.Ranger) {
me.mu.Lock()
defer me.mu.Unlock()
me.ipBlockList = list
if me.dHT != nil {
me.dHT.SetIPBlockList(list)
}
}
func (me *Client) PeerID() string {
return string(me.peerID[:])
}
func (me *Client) ListenAddr() (addr net.Addr) {
for _, l := range me.listeners {
addr = l.Addr()
break
}
return
}
type hashSorter struct {
Hashes []InfoHash
}
func (me hashSorter) Len() int {
return len(me.Hashes)
}
func (me hashSorter) Less(a, b int) bool {
return (&big.Int{}).SetBytes(me.Hashes[a][:]).Cmp((&big.Int{}).SetBytes(me.Hashes[b][:])) < 0
}
func (me hashSorter) Swap(a, b int) {
me.Hashes[a], me.Hashes[b] = me.Hashes[b], me.Hashes[a]
}
func (cl *Client) sortedTorrents() (ret []*torrent) {
var hs hashSorter
for ih := range cl.torrents {
hs.Hashes = append(hs.Hashes, ih)
}
sort.Sort(hs)
for _, ih := range hs.Hashes {
ret = append(ret, cl.torrent(ih))
}
return
}
// Writes out a human readable status of the client, such as for writing to a
// HTTP status page.
func (cl *Client) WriteStatus(_w io.Writer) {
cl.mu.RLock()
defer cl.mu.RUnlock()
w := bufio.NewWriter(_w)
defer w.Flush()
if addr := cl.ListenAddr(); addr != nil {
fmt.Fprintf(w, "Listening on %s\n", cl.ListenAddr())
} else {
fmt.Fprintln(w, "Not listening!")
}
fmt.Fprintf(w, "Peer ID: %+q\n", cl.peerID)
if cl.dHT != nil {
dhtStats := cl.dHT.Stats()
fmt.Fprintf(w, "DHT nodes: %d (%d good, %d banned)\n", dhtStats.Nodes, dhtStats.GoodNodes, dhtStats.BadNodes)
fmt.Fprintf(w, "DHT Server ID: %x\n", cl.dHT.ID())
fmt.Fprintf(w, "DHT port: %d\n", missinggo.AddrPort(cl.dHT.Addr()))
fmt.Fprintf(w, "DHT announces: %d\n", dhtStats.ConfirmedAnnounces)
fmt.Fprintf(w, "Outstanding transactions: %d\n", dhtStats.OutstandingTransactions)
}
fmt.Fprintf(w, "# Torrents: %d\n", len(cl.torrents))
fmt.Fprintln(w)
for _, t := range cl.sortedTorrents() {
if t.Name() == "" {
fmt.Fprint(w, "<unknown name>")
} else {
fmt.Fprint(w, t.Name())
}
fmt.Fprint(w, "\n")
if t.haveInfo() {
fmt.Fprintf(w, "%f%% of %d bytes", 100*(1-float64(t.bytesLeft())/float64(t.length)), t.length)
} else {
w.WriteString("<missing metainfo>")
}
fmt.Fprint(w, "\n")
t.writeStatus(w, cl)
fmt.Fprintln(w)
}
}
// Calculates the number of pieces to set to Readahead priority, after the
// Now, and Next pieces.
func readaheadPieces(readahead, pieceLength int64) (ret int) {
// Expand the readahead to fit any partial pieces. Subtract 1 for the
// "next" piece that is assigned.
ret = int((readahead+pieceLength-1)/pieceLength - 1)
// Lengthen the "readahead tail" to smooth blockiness that occurs when the
// piece length is much larger than the readahead.
if ret < 2 {
ret++
}
return
}
func (cl *Client) configDir() string {
if cl.config.ConfigDir == "" {
return filepath.Join(os.Getenv("HOME"), ".config/torrent")
}
return cl.config.ConfigDir
}
// The directory where the Client expects to find and store configuration
// data. Defaults to $HOME/.config/torrent.
func (cl *Client) ConfigDir() string {
return cl.configDir()
}
func loadPackedBlocklist(filename string) (ret iplist.Ranger, err error) {
f, err := os.Open(filename)
if os.IsNotExist(err) {
err = nil
return
}
if err != nil {
return
}
defer f.Close()
mm, err := mmap.Map(f, mmap.RDONLY, 0)
if err != nil {
return
}
ret = iplist.NewFromPacked(mm)
return
}
func (cl *Client) setEnvBlocklist() (err error) {
filename := os.Getenv("TORRENT_BLOCKLIST_FILE")
defaultBlocklist := filename == ""
if defaultBlocklist {
cl.ipBlockList, err = loadPackedBlocklist(filepath.Join(cl.configDir(), "packed-blocklist"))
if err != nil {
return
}
if cl.ipBlockList != nil {
return
}
filename = filepath.Join(cl.configDir(), "blocklist")
}
f, err := os.Open(filename)
if err != nil {
if defaultBlocklist {
err = nil
}
return
}
defer f.Close()
cl.ipBlockList, err = iplist.NewFromReader(f)
return
}
func (cl *Client) initBannedTorrents() error {
f, err := os.Open(filepath.Join(cl.configDir(), "banned_infohashes"))
if err != nil {
if os.IsNotExist(err) {
return nil
}
return fmt.Errorf("error opening banned infohashes file: %s", err)
}
defer f.Close()
scanner := bufio.NewScanner(f)
cl.bannedTorrents = make(map[InfoHash]struct{})
for scanner.Scan() {
if strings.HasPrefix(strings.TrimSpace(scanner.Text()), "#") {
continue
}
var ihs string
n, err := fmt.Sscanf(scanner.Text(), "%x", &ihs)
if err != nil {
return fmt.Errorf("error reading infohash: %s", err)
}
if n != 1 {
continue
}
if len(ihs) != 20 {
return errors.New("bad infohash")
}
var ih InfoHash
CopyExact(&ih, ihs)
cl.bannedTorrents[ih] = struct{}{}
}
if err := scanner.Err(); err != nil {
return fmt.Errorf("error scanning file: %s", err)
}
return nil
}
// Creates a new client.
func NewClient(cfg *Config) (cl *Client, err error) {
if cfg == nil {
cfg = &Config{}
}
defer func() {
if err != nil {
cl = nil
}
}()
cl = &Client{
halfOpenLimit: socketsPerTorrent,
config: *cfg,
torrentDataOpener: func(md *metainfo.Info) Data {
return filePkg.TorrentData(md, cfg.DataDir)
},
dopplegangerAddrs: make(map[string]struct{}),
torrents: make(map[InfoHash]*torrent),
}
CopyExact(&cl.extensionBytes, defaultExtensionBytes)
cl.event.L = &cl.mu
if cfg.TorrentDataOpener != nil {
cl.torrentDataOpener = cfg.TorrentDataOpener
}
if cfg.IPBlocklist != nil {
cl.ipBlockList = cfg.IPBlocklist
} else if !cfg.NoDefaultBlocklist {
err = cl.setEnvBlocklist()
if err != nil {
return
}
}
if err = cl.initBannedTorrents(); err != nil {
err = fmt.Errorf("error initing banned torrents: %s", err)
return
}
if cfg.PeerID != "" {
CopyExact(&cl.peerID, cfg.PeerID)
} else {
o := copy(cl.peerID[:], bep20)
_, err = rand.Read(cl.peerID[o:])
if err != nil {
panic("error generating peer id")
}
}
// Returns the laddr string to listen on for the next Listen call.
listenAddr := func() string {
if addr := cl.ListenAddr(); addr != nil {
return addr.String()
}
if cfg.ListenAddr == "" {
return ":50007"
}
return cfg.ListenAddr
}
if !cl.config.DisableTCP {
var l net.Listener
l, err = net.Listen(func() string {
if cl.config.DisableIPv6 {
return "tcp4"
} else {
return "tcp"
}
}(), listenAddr())
if err != nil {
return
}
cl.listeners = append(cl.listeners, l)
go cl.acceptConnections(l, false)
}
if !cl.config.DisableUTP {
cl.utpSock, err = utp.NewSocket(func() string {
if cl.config.DisableIPv6 {
return "udp4"
} else {
return "udp"
}
}(), listenAddr())
if err != nil {
return
}
cl.listeners = append(cl.listeners, cl.utpSock)
go cl.acceptConnections(cl.utpSock, true)
}
if !cfg.NoDHT {
dhtCfg := cfg.DHTConfig
if dhtCfg.IPBlocklist == nil {
dhtCfg.IPBlocklist = cl.ipBlockList
}
if dhtCfg.Addr == "" {
dhtCfg.Addr = listenAddr()
}
if dhtCfg.Conn == nil && cl.utpSock != nil {
dhtCfg.Conn = cl.utpSock
}
cl.dHT, err = dht.NewServer(&dhtCfg)
if err != nil {
return
}
}
return
}
// Stops the client. All connections to peers are closed and all activity will
// come to a halt.
func (me *Client) Close() {
me.mu.Lock()
defer me.mu.Unlock()
me.closed.Set()
if me.dHT != nil {
me.dHT.Close()
}
for _, l := range me.listeners {
l.Close()
}
for _, t := range me.torrents {
t.close()
}
me.event.Broadcast()
}
var ipv6BlockRange = iplist.Range{Description: "non-IPv4 address"}
func (cl *Client) ipBlockRange(ip net.IP) (r iplist.Range, blocked bool) {
if cl.ipBlockList == nil {
return
}
ip4 := ip.To4()
// If blocklists are enabled, then block non-IPv4 addresses, because
// blocklists do not yet support IPv6.
if ip4 == nil {
if missinggo.CryHeard() {
log.Printf("blocking non-IPv4 address: %s", ip)
}
r = ipv6BlockRange
blocked = true
return
}
return cl.ipBlockList.Lookup(ip4)
}
func (cl *Client) waitAccept() {
cl.mu.Lock()
defer cl.mu.Unlock()
for {
for _, t := range cl.torrents {
if cl.wantConns(t) {
return
}
}
if cl.closed.IsSet() {
return
}
cl.event.Wait()
}
}
func (cl *Client) acceptConnections(l net.Listener, utp bool) {
for {
cl.waitAccept()
conn, err := l.Accept()
conn = pproffd.WrapNetConn(conn)
if cl.closed.IsSet() {
if conn != nil {
conn.Close()
}
return
}
if err != nil {
log.Print(err)
// I think something harsher should happen here? Our accept
// routine just fucked off.
return
}
if utp {
acceptUTP.Add(1)
} else {
acceptTCP.Add(1)
}
cl.mu.RLock()
doppleganger := cl.dopplegangerAddr(conn.RemoteAddr().String())
_, blocked := cl.ipBlockRange(AddrIP(conn.RemoteAddr()))
cl.mu.RUnlock()
if blocked || doppleganger {
acceptReject.Add(1)
// log.Printf("inbound connection from %s blocked by %s", conn.RemoteAddr(), blockRange)
conn.Close()
continue
}
go cl.incomingConnection(conn, utp)
}
}
func (cl *Client) incomingConnection(nc net.Conn, utp bool) {
defer nc.Close()
if tc, ok := nc.(*net.TCPConn); ok {
tc.SetLinger(0)
}
c := newConnection()
c.conn = nc
c.rw = nc
c.Discovery = peerSourceIncoming
c.uTP = utp
err := cl.runReceivedConn(c)
if err != nil {
// log.Print(err)
}
}
// Returns a handle to the given torrent, if it's present in the client.
func (cl *Client) Torrent(ih InfoHash) (T Torrent, ok bool) {
cl.mu.Lock()
defer cl.mu.Unlock()
t, ok := cl.torrents[ih]
if !ok {
return
}
T = Torrent{cl, t}
return
}
func (me *Client) torrent(ih InfoHash) *torrent {
return me.torrents[ih]
}
type dialResult struct {
Conn net.Conn
UTP bool
}
func doDial(dial func(addr string, t *torrent) (net.Conn, error), ch chan dialResult, utp bool, addr string, t *torrent) {
conn, err := dial(addr, t)
if err != nil {
if conn != nil {
conn.Close()
}
conn = nil // Pedantic
}
ch <- dialResult{conn, utp}
if err == nil {
successfulDials.Add(1)
return
}
unsuccessfulDials.Add(1)
}
func reducedDialTimeout(max time.Duration, halfOpenLimit int, pendingPeers int) (ret time.Duration) {
ret = max / time.Duration((pendingPeers+halfOpenLimit)/halfOpenLimit)
if ret < minDialTimeout {
ret = minDialTimeout
}
return
}
// Returns whether an address is known to connect to a client with our own ID.
func (me *Client) dopplegangerAddr(addr string) bool {
_, ok := me.dopplegangerAddrs[addr]
return ok
}
// Start the process of connecting to the given peer for the given torrent if
// appropriate.
func (me *Client) initiateConn(peer Peer, t *torrent) {
if peer.Id == me.peerID {
return
}
addr := net.JoinHostPort(peer.IP.String(), fmt.Sprintf("%d", peer.Port))
if me.dopplegangerAddr(addr) || t.addrActive(addr) {
duplicateConnsAvoided.Add(1)
return
}
if r, ok := me.ipBlockRange(peer.IP); ok {
log.Printf("outbound connect to %s blocked by IP blocklist rule %s", peer.IP, r)
return
}
t.HalfOpen[addr] = struct{}{}
go me.outgoingConnection(t, addr, peer.Source)
}
func (me *Client) dialTimeout(t *torrent) time.Duration {
me.mu.Lock()
pendingPeers := len(t.Peers)
me.mu.Unlock()
return reducedDialTimeout(nominalDialTimeout, me.halfOpenLimit, pendingPeers)
}
func (me *Client) dialTCP(addr string, t *torrent) (c net.Conn, err error) {
c, err = net.DialTimeout("tcp", addr, me.dialTimeout(t))
if err == nil {
c.(*net.TCPConn).SetLinger(0)
}
return
}
func (me *Client) dialUTP(addr string, t *torrent) (c net.Conn, err error) {
return me.utpSock.DialTimeout(addr, me.dialTimeout(t))
}
// Returns a connection over UTP or TCP, whichever is first to connect.
func (me *Client) dialFirst(addr string, t *torrent) (conn net.Conn, utp bool) {
// Initiate connections via TCP and UTP simultaneously. Use the first one
// that succeeds.
left := 0
if !me.config.DisableUTP {
left++
}
if !me.config.DisableTCP {
left++
}
resCh := make(chan dialResult, left)
if !me.config.DisableUTP {
go doDial(me.dialUTP, resCh, true, addr, t)
}
if !me.config.DisableTCP {
go doDial(me.dialTCP, resCh, false, addr, t)
}
var res dialResult
// Wait for a successful connection.
for ; left > 0 && res.Conn == nil; left-- {
res = <-resCh
}
if left > 0 {
// There are still incompleted dials.
go func() {
for ; left > 0; left-- {
conn := (<-resCh).Conn
if conn != nil {
conn.Close()
}
}
}()
}
conn = res.Conn
utp = res.UTP
return
}
func (me *Client) noLongerHalfOpen(t *torrent, addr string) {
if _, ok := t.HalfOpen[addr]; !ok {
panic("invariant broken")
}
delete(t.HalfOpen, addr)
me.openNewConns(t)
}
// Performs initiator handshakes and returns a connection. Returns nil
// *connection if no connection for valid reasons.
func (me *Client) handshakesConnection(nc net.Conn, t *torrent, encrypted, utp bool) (c *connection, err error) {
c = newConnection()
c.conn = nc
c.rw = nc
c.encrypted = encrypted
c.uTP = utp
err = nc.SetDeadline(time.Now().Add(handshakesTimeout))
if err != nil {
return
}
ok, err := me.initiateHandshakes(c, t)
if !ok {
c = nil
}
return
}
// Returns nil connection and nil error if no connection could be established
// for valid reasons.
func (me *Client) establishOutgoingConn(t *torrent, addr string) (c *connection, err error) {
nc, utp := me.dialFirst(addr, t)
if nc == nil {
return
}
c, err = me.handshakesConnection(nc, t, !me.config.DisableEncryption, utp)
if err != nil {
nc.Close()
return
} else if c != nil {
return
}
nc.Close()
if me.config.DisableEncryption {
// We already tried without encryption.
return
}
// Try again without encryption, using whichever protocol type worked last
// time.
if utp {
nc, err = me.dialUTP(addr, t)
} else {
nc, err = me.dialTCP(addr, t)
}
if err != nil {
err = fmt.Errorf("error dialing for unencrypted connection: %s", err)
return
}
c, err = me.handshakesConnection(nc, t, false, utp)
if err != nil || c == nil {
nc.Close()
}
return
}
// Called to dial out and run a connection. The addr we're given is already
// considered half-open.
func (me *Client) outgoingConnection(t *torrent, addr string, ps peerSource) {
c, err := me.establishOutgoingConn(t, addr)
me.mu.Lock()
defer me.mu.Unlock()
// Don't release lock between here and addConnection, unless it's for
// failure.
me.noLongerHalfOpen(t, addr)
if err != nil {
if me.config.Debug {
log.Printf("error establishing outgoing connection: %s", err)
}
return
}
if c == nil {
return
}
defer c.Close()
c.Discovery = ps
err = me.runInitiatedHandshookConn(c, t)
if err != nil {
if me.config.Debug {
log.Printf("error in established outgoing connection: %s", err)
}
}
}
// The port number for incoming peer connections. 0 if the client isn't
// listening.
func (cl *Client) incomingPeerPort() int {
listenAddr := cl.ListenAddr()
if listenAddr == nil {
return 0
}
return missinggo.AddrPort(listenAddr)
}
// Convert a net.Addr to its compact IP representation. Either 4 or 16 bytes
// per "yourip" field of http://www.bittorrent.org/beps/bep_0010.html.
func addrCompactIP(addr net.Addr) (string, error) {
host, _, err := net.SplitHostPort(addr.String())
if err != nil {
return "", err
}
ip := net.ParseIP(host)
if v4 := ip.To4(); v4 != nil {
if len(v4) != 4 {
panic(v4)
}
return string(v4), nil
}
return string(ip.To16()), nil
}
func handshakeWriter(w io.Writer, bb <-chan []byte, done chan<- error) {
var err error
for b := range bb {
_, err = w.Write(b)
if err != nil {
break
}
}
done <- err
}
type (
peerExtensionBytes [8]byte
peerID [20]byte
)
func (me *peerExtensionBytes) SupportsExtended() bool {
return me[5]&0x10 != 0
}
func (me *peerExtensionBytes) SupportsDHT() bool {
return me[7]&0x01 != 0
}
func (me *peerExtensionBytes) SupportsFast() bool {
return me[7]&0x04 != 0
}
type handshakeResult struct {
peerExtensionBytes
peerID
InfoHash
}
// ih is nil if we expect the peer to declare the InfoHash, such as when the
// peer initiated the connection. Returns ok if the handshake was successful,
// and err if there was an unexpected condition other than the peer simply
// abandoning the handshake.
func handshake(sock io.ReadWriter, ih *InfoHash, peerID [20]byte, extensions peerExtensionBytes) (res handshakeResult, ok bool, err error) {
// Bytes to be sent to the peer. Should never block the sender.
postCh := make(chan []byte, 4)
// A single error value sent when the writer completes.
writeDone := make(chan error, 1)
// Performs writes to the socket and ensures posts don't block.
go handshakeWriter(sock, postCh, writeDone)
defer func() {
close(postCh) // Done writing.
if !ok {
return
}
if err != nil {
panic(err)
}
// Wait until writes complete before returning from handshake.
err = <-writeDone
if err != nil {
err = fmt.Errorf("error writing: %s", err)
}
}()
post := func(bb []byte) {
select {
case postCh <- bb:
default:
panic("mustn't block while posting")
}
}
post([]byte(pp.Protocol))
post(extensions[:])
if ih != nil { // We already know what we want.
post(ih[:])
post(peerID[:])
}
var b [68]byte
_, err = io.ReadFull(sock, b[:68])
if err != nil {
err = nil
return
}
if string(b[:20]) != pp.Protocol {
return
}
CopyExact(&res.peerExtensionBytes, b[20:28])
CopyExact(&res.InfoHash, b[28:48])
CopyExact(&res.peerID, b[48:68])
peerExtensions.Add(hex.EncodeToString(res.peerExtensionBytes[:]), 1)
// TODO: Maybe we can just drop peers here if we're not interested. This
// could prevent them trying to reconnect, falsely believing there was
// just a problem.
if ih == nil { // We were waiting for the peer to tell us what they wanted.
post(res.InfoHash[:])
post(peerID[:])
}
ok = true
return
}
// Wraps a raw connection and provides the interface we want for using the
// connection in the message loop.
type deadlineReader struct {
nc net.Conn
r io.Reader
}
func (me deadlineReader) Read(b []byte) (n int, err error) {
// Keep-alives should be received every 2 mins. Give a bit of gracetime.
err = me.nc.SetReadDeadline(time.Now().Add(150 * time.Second))
if err != nil {
err = fmt.Errorf("error setting read deadline: %s", err)
}
n, err = me.r.Read(b)
// Convert common errors into io.EOF.
// if err != nil {
// if opError, ok := err.(*net.OpError); ok && opError.Op == "read" && opError.Err == syscall.ECONNRESET {
// err = io.EOF
// } else if netErr, ok := err.(net.Error); ok && netErr.Timeout() {
// if n != 0 {
// panic(n)
// }
// err = io.EOF
// }
// }
return
}
type readWriter struct {
io.Reader
io.Writer
}
func maybeReceiveEncryptedHandshake(rw io.ReadWriter, skeys [][]byte) (ret io.ReadWriter, encrypted bool, err error) {
var protocol [len(pp.Protocol)]byte
_, err = io.ReadFull(rw, protocol[:])
if err != nil {
return
}
ret = readWriter{
io.MultiReader(bytes.NewReader(protocol[:]), rw),
rw,
}
if string(protocol[:]) == pp.Protocol {
return
}
encrypted = true
ret, err = mse.ReceiveHandshake(ret, skeys)
return
}
func (cl *Client) receiveSkeys() (ret [][]byte) {
for ih := range cl.torrents {
ret = append(ret, ih[:])
}
return
}
func (me *Client) initiateHandshakes(c *connection, t *torrent) (ok bool, err error) {
if c.encrypted {
c.rw, err = mse.InitiateHandshake(c.rw, t.InfoHash[:], nil)
if err != nil {
return
}
}
ih, ok, err := me.connBTHandshake(c, &t.InfoHash)
if ih != t.InfoHash {
ok = false
}
return
}