/
listener.go
343 lines (291 loc) · 8.14 KB
/
listener.go
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// Copyright (C) 2015 Audrius Butkevicius and Contributors (see the CONTRIBUTORS file).
package main
import (
"crypto/tls"
"encoding/hex"
"log"
"net"
"sync"
"sync/atomic"
"time"
syncthingprotocol "github.com/syncthing/syncthing/lib/protocol"
"github.com/syncthing/syncthing/lib/tlsutil"
"github.com/syncthing/syncthing/lib/relay/protocol"
)
var (
outboxesMut = sync.RWMutex{}
outboxes = make(map[syncthingprotocol.DeviceID]chan interface{})
numConnections int64
)
func listener(addr string, config *tls.Config) {
tcpListener, err := net.Listen("tcp", addr)
if err != nil {
log.Fatalln(err)
}
listener := tlsutil.DowngradingListener{tcpListener, nil}
for {
conn, isTLS, err := listener.AcceptNoWrapTLS()
if err != nil {
if debug {
log.Println("Listener failed to accept connection from", conn.RemoteAddr(), ". Possibly a TCP Ping.")
}
continue
}
setTCPOptions(conn)
if debug {
log.Println("Listener accepted connection from", conn.RemoteAddr(), "tls", isTLS)
}
if isTLS {
go protocolConnectionHandler(conn, config)
} else {
go sessionConnectionHandler(conn)
}
}
}
func protocolConnectionHandler(tcpConn net.Conn, config *tls.Config) {
conn := tls.Server(tcpConn, config)
err := conn.Handshake()
if err != nil {
if debug {
log.Println("Protocol connection TLS handshake:", conn.RemoteAddr(), err)
}
conn.Close()
return
}
state := conn.ConnectionState()
if (!state.NegotiatedProtocolIsMutual || state.NegotiatedProtocol != protocol.ProtocolName) && debug {
log.Println("Protocol negotiation error")
}
certs := state.PeerCertificates
if len(certs) != 1 {
if debug {
log.Println("Certificate list error")
}
conn.Close()
return
}
id := syncthingprotocol.NewDeviceID(certs[0].Raw)
messages := make(chan interface{})
errors := make(chan error, 1)
outbox := make(chan interface{})
// Read messages from the connection and send them on the messages
// channel. When there is an error, send it on the error channel and
// return. Applies also when the connection gets closed, so the pattern
// below is to close the connection on error, then wait for the error
// signal from messageReader to exit.
go messageReader(conn, messages, errors)
pingTicker := time.NewTicker(pingInterval)
timeoutTicker := time.NewTimer(networkTimeout)
joined := false
for {
select {
case message := <-messages:
timeoutTicker.Reset(networkTimeout)
if debug {
log.Printf("Message %T from %s", message, id)
}
switch msg := message.(type) {
case protocol.JoinRelayRequest:
if atomic.LoadInt32(&overLimit) > 0 {
protocol.WriteMessage(conn, protocol.RelayFull{})
if debug {
log.Println("Refusing join request from", id, "due to being over limits")
}
conn.Close()
limitCheckTimer.Reset(time.Second)
continue
}
outboxesMut.RLock()
_, ok := outboxes[id]
outboxesMut.RUnlock()
if ok {
protocol.WriteMessage(conn, protocol.ResponseAlreadyConnected)
if debug {
log.Println("Already have a peer with the same ID", id, conn.RemoteAddr())
}
conn.Close()
continue
}
outboxesMut.Lock()
outboxes[id] = outbox
outboxesMut.Unlock()
joined = true
protocol.WriteMessage(conn, protocol.ResponseSuccess)
case protocol.ConnectRequest:
requestedPeer := syncthingprotocol.DeviceIDFromBytes(msg.ID)
outboxesMut.RLock()
peerOutbox, ok := outboxes[requestedPeer]
outboxesMut.RUnlock()
if !ok {
if debug {
log.Println(id, "is looking for", requestedPeer, "which does not exist")
}
protocol.WriteMessage(conn, protocol.ResponseNotFound)
conn.Close()
continue
}
// requestedPeer is the server, id is the client
ses := newSession(requestedPeer, id, sessionLimiter, globalLimiter)
go ses.Serve()
clientInvitation := ses.GetClientInvitationMessage()
serverInvitation := ses.GetServerInvitationMessage()
if err := protocol.WriteMessage(conn, clientInvitation); err != nil {
if debug {
log.Printf("Error sending invitation from %s to client: %s", id, err)
}
conn.Close()
continue
}
peerOutbox <- serverInvitation
if debug {
log.Println("Sent invitation from", id, "to", requestedPeer)
}
conn.Close()
case protocol.Ping:
if err := protocol.WriteMessage(conn, protocol.Pong{}); err != nil {
if debug {
log.Println("Error writing pong:", err)
}
conn.Close()
continue
}
case protocol.Pong:
// Nothing
default:
if debug {
log.Printf("Unknown message %s: %T", id, message)
}
protocol.WriteMessage(conn, protocol.ResponseUnexpectedMessage)
conn.Close()
}
case err := <-errors:
if debug {
log.Printf("Closing connection %s: %s", id, err)
}
close(outbox)
// Potentially closing a second time.
conn.Close()
if joined {
// Only delete the outbox if the client is joined, as it might be
// a lookup request coming from the same client.
outboxesMut.Lock()
delete(outboxes, id)
outboxesMut.Unlock()
// Also, kill all sessions related to this node, as it probably
// went offline. This is for the other end to realize the client
// is no longer there faster. This also helps resolve
// 'already connected' errors when one of the sides is
// restarting, and connecting to the other peer before the other
// peer even realised that the node has gone away.
dropSessions(id)
}
return
case <-pingTicker.C:
if !joined {
if debug {
log.Println(id, "didn't join within", pingInterval)
}
conn.Close()
continue
}
if err := protocol.WriteMessage(conn, protocol.Ping{}); err != nil {
if debug {
log.Println(id, err)
}
conn.Close()
}
if atomic.LoadInt32(&overLimit) > 0 && !hasSessions(id) {
if debug {
log.Println("Dropping", id, "as it has no sessions and we are over our limits")
}
protocol.WriteMessage(conn, protocol.RelayFull{})
conn.Close()
limitCheckTimer.Reset(time.Second)
}
case <-timeoutTicker.C:
// We should receive a error from the reader loop, which will cause
// us to quit this loop.
if debug {
log.Printf("%s timed out", id)
}
conn.Close()
case msg := <-outbox:
if msg == nil {
conn.Close()
return
}
if debug {
log.Printf("Sending message %T to %s", msg, id)
}
if err := protocol.WriteMessage(conn, msg); err != nil {
if debug {
log.Println(id, err)
}
conn.Close()
}
}
}
}
func sessionConnectionHandler(conn net.Conn) {
if err := conn.SetDeadline(time.Now().Add(messageTimeout)); err != nil {
if debug {
log.Println("Weird error setting deadline:", err, "on", conn.RemoteAddr())
}
return
}
message, err := protocol.ReadMessage(conn)
if err != nil {
return
}
switch msg := message.(type) {
case protocol.JoinSessionRequest:
ses := findSession(string(msg.Key))
if debug {
log.Println(conn.RemoteAddr(), "session lookup", ses, hex.EncodeToString(msg.Key)[:5])
}
if ses == nil {
protocol.WriteMessage(conn, protocol.ResponseNotFound)
conn.Close()
return
}
if !ses.AddConnection(conn) {
if debug {
log.Println("Failed to add", conn.RemoteAddr(), "to session", ses)
}
protocol.WriteMessage(conn, protocol.ResponseAlreadyConnected)
conn.Close()
return
}
if err := protocol.WriteMessage(conn, protocol.ResponseSuccess); err != nil {
if debug {
log.Println("Failed to send session join response to ", conn.RemoteAddr(), "for", ses)
}
return
}
if err := conn.SetDeadline(time.Time{}); err != nil {
if debug {
log.Println("Weird error setting deadline:", err, "on", conn.RemoteAddr())
}
conn.Close()
return
}
default:
if debug {
log.Println("Unexpected message from", conn.RemoteAddr(), message)
}
protocol.WriteMessage(conn, protocol.ResponseUnexpectedMessage)
conn.Close()
}
}
func messageReader(conn net.Conn, messages chan<- interface{}, errors chan<- error) {
atomic.AddInt64(&numConnections, 1)
defer atomic.AddInt64(&numConnections, -1)
for {
msg, err := protocol.ReadMessage(conn)
if err != nil {
errors <- err
return
}
messages <- msg
}
}