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connections.go
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connections.go
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// Copyright (C) 2015 The Syncthing Authors.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at http://mozilla.org/MPL/2.0/.
package connections
import (
"crypto/tls"
"fmt"
"io"
"net"
"net/url"
"sync"
"time"
"github.com/juju/ratelimit"
"github.com/syncthing/syncthing/lib/config"
"github.com/syncthing/syncthing/lib/discover"
"github.com/syncthing/syncthing/lib/events"
"github.com/syncthing/syncthing/lib/model"
"github.com/syncthing/syncthing/lib/protocol"
"github.com/syncthing/syncthing/lib/relay"
"github.com/syncthing/syncthing/lib/relay/client"
"github.com/thejerf/suture"
)
type DialerFactory func(*url.URL, *tls.Config) (*tls.Conn, error)
type ListenerFactory func(*url.URL, *tls.Config, chan<- model.IntermediateConnection)
var (
dialers = make(map[string]DialerFactory, 0)
listeners = make(map[string]ListenerFactory, 0)
)
type Model interface {
protocol.Model
AddConnection(conn model.Connection)
ConnectedTo(remoteID protocol.DeviceID) bool
IsPaused(remoteID protocol.DeviceID) bool
}
// The connection service listens on TLS and dials configured unconnected
// devices. Successful connections are handed to the model.
type connectionSvc struct {
*suture.Supervisor
cfg *config.Wrapper
myID protocol.DeviceID
model Model
tlsCfg *tls.Config
discoverer discover.Finder
conns chan model.IntermediateConnection
relaySvc *relay.Svc
bepProtocolName string
tlsDefaultCommonName string
lans []*net.IPNet
writeRateLimit *ratelimit.Bucket
readRateLimit *ratelimit.Bucket
lastRelayCheck map[protocol.DeviceID]time.Time
mut sync.RWMutex
connType map[protocol.DeviceID]model.ConnectionType
relaysEnabled bool
}
func NewConnectionSvc(cfg *config.Wrapper, myID protocol.DeviceID, mdl Model, tlsCfg *tls.Config, discoverer discover.Finder, relaySvc *relay.Svc,
bepProtocolName string, tlsDefaultCommonName string, lans []*net.IPNet) suture.Service {
svc := &connectionSvc{
Supervisor: suture.NewSimple("connectionSvc"),
cfg: cfg,
myID: myID,
model: mdl,
tlsCfg: tlsCfg,
discoverer: discoverer,
relaySvc: relaySvc,
conns: make(chan model.IntermediateConnection),
bepProtocolName: bepProtocolName,
tlsDefaultCommonName: tlsDefaultCommonName,
lans: lans,
connType: make(map[protocol.DeviceID]model.ConnectionType),
relaysEnabled: cfg.Options().RelaysEnabled,
lastRelayCheck: make(map[protocol.DeviceID]time.Time),
}
cfg.Subscribe(svc)
if svc.cfg.Options().MaxSendKbps > 0 {
svc.writeRateLimit = ratelimit.NewBucketWithRate(float64(1000*svc.cfg.Options().MaxSendKbps), int64(5*1000*svc.cfg.Options().MaxSendKbps))
}
if svc.cfg.Options().MaxRecvKbps > 0 {
svc.readRateLimit = ratelimit.NewBucketWithRate(float64(1000*svc.cfg.Options().MaxRecvKbps), int64(5*1000*svc.cfg.Options().MaxRecvKbps))
}
// There are several moving parts here; one routine per listening address
// to handle incoming connections, one routine to periodically attempt
// outgoing connections, one routine to the the common handling
// regardless of whether the connection was incoming or outgoing.
// Furthermore, a relay service which handles incoming requests to connect
// via the relays.
//
// TODO: Clean shutdown, and/or handling config changes on the fly. We
// partly do this now - new devices and addresses will be picked up, but
// not new listen addresses and we don't support disconnecting devices
// that are removed and so on...
svc.Add(serviceFunc(svc.connect))
for _, addr := range svc.cfg.Options().ListenAddress {
uri, err := url.Parse(addr)
if err != nil {
l.Infoln("Failed to parse listen address:", addr, err)
continue
}
listener, ok := listeners[uri.Scheme]
if !ok {
l.Infoln("Unknown listen address scheme:", uri.String())
continue
}
l.Debugln("listening on", uri)
svc.Add(serviceFunc(func() {
listener(uri, svc.tlsCfg, svc.conns)
}))
}
svc.Add(serviceFunc(svc.handle))
if svc.relaySvc != nil {
svc.Add(serviceFunc(svc.acceptRelayConns))
}
return svc
}
func (s *connectionSvc) handle() {
next:
for c := range s.conns {
cs := c.Conn.ConnectionState()
// We should have negotiated the next level protocol "bep/1.0" as part
// of the TLS handshake. Unfortunately this can't be a hard error,
// because there are implementations out there that don't support
// protocol negotiation (iOS for one...).
if !cs.NegotiatedProtocolIsMutual || cs.NegotiatedProtocol != s.bepProtocolName {
l.Infof("Peer %s did not negotiate bep/1.0", c.Conn.RemoteAddr())
}
// We should have received exactly one certificate from the other
// side. If we didn't, they don't have a device ID and we drop the
// connection.
certs := cs.PeerCertificates
if cl := len(certs); cl != 1 {
l.Infof("Got peer certificate list of length %d != 1 from %s; protocol error", cl, c.Conn.RemoteAddr())
c.Conn.Close()
continue
}
remoteCert := certs[0]
remoteID := protocol.NewDeviceID(remoteCert.Raw)
// The device ID should not be that of ourselves. It can happen
// though, especially in the presence of NAT hairpinning, multiple
// clients between the same NAT gateway, and global discovery.
if remoteID == s.myID {
l.Infof("Connected to myself (%s) - should not happen", remoteID)
c.Conn.Close()
continue
}
// If we have a relay connection, and the new incoming connection is
// not a relay connection, we should drop that, and prefer the this one.
s.mut.RLock()
ct, ok := s.connType[remoteID]
s.mut.RUnlock()
if ok && !ct.IsDirect() && c.Type.IsDirect() {
l.Debugln("Switching connections", remoteID)
s.model.Close(remoteID, fmt.Errorf("switching connections"))
} else if s.model.ConnectedTo(remoteID) {
// We should not already be connected to the other party. TODO: This
// could use some better handling. If the old connection is dead but
// hasn't timed out yet we may want to drop *that* connection and keep
// this one. But in case we are two devices connecting to each other
// in parallel we don't want to do that or we end up with no
// connections still established...
l.Infof("Connected to already connected device (%s)", remoteID)
c.Conn.Close()
continue
} else if s.model.IsPaused(remoteID) {
l.Infof("Connection from paused device (%s)", remoteID)
c.Conn.Close()
continue
}
for deviceID, deviceCfg := range s.cfg.Devices() {
if deviceID == remoteID {
// Verify the name on the certificate. By default we set it to
// "syncthing" when generating, but the user may have replaced
// the certificate and used another name.
certName := deviceCfg.CertName
if certName == "" {
certName = s.tlsDefaultCommonName
}
err := remoteCert.VerifyHostname(certName)
if err != nil {
// Incorrect certificate name is something the user most
// likely wants to know about, since it's an advanced
// config. Warn instead of Info.
l.Warnf("Bad certificate from %s (%v): %v", remoteID, c.Conn.RemoteAddr(), err)
c.Conn.Close()
continue next
}
// If rate limiting is set, and based on the address we should
// limit the connection, then we wrap it in a limiter.
limit := s.shouldLimit(c.Conn.RemoteAddr())
wr := io.Writer(c.Conn)
if limit && s.writeRateLimit != nil {
wr = NewWriteLimiter(c.Conn, s.writeRateLimit)
}
rd := io.Reader(c.Conn)
if limit && s.readRateLimit != nil {
rd = NewReadLimiter(c.Conn, s.readRateLimit)
}
name := fmt.Sprintf("%s-%s (%s)", c.Conn.LocalAddr(), c.Conn.RemoteAddr(), c.Type)
protoConn := protocol.NewConnection(remoteID, rd, wr, s.model, name, deviceCfg.Compression)
l.Infof("Established secure connection to %s at %s", remoteID, name)
l.Debugf("cipher suite: %04X in lan: %t", c.Conn.ConnectionState().CipherSuite, !limit)
s.model.AddConnection(model.Connection{
c.Conn,
protoConn,
c.Type,
})
s.mut.Lock()
s.connType[remoteID] = c.Type
s.mut.Unlock()
continue next
}
}
if !s.cfg.IgnoredDevice(remoteID) {
events.Default.Log(events.DeviceRejected, map[string]string{
"device": remoteID.String(),
"address": c.Conn.RemoteAddr().String(),
})
}
l.Infof("Connection from %s (%s) with ignored device ID %s", c.Conn.RemoteAddr(), c.Type, remoteID)
c.Conn.Close()
}
}
func (s *connectionSvc) connect() {
delay := time.Second
for {
nextDevice:
for deviceID, deviceCfg := range s.cfg.Devices() {
if deviceID == s.myID {
continue
}
if s.model.IsPaused(deviceID) {
continue
}
connected := s.model.ConnectedTo(deviceID)
s.mut.RLock()
ct, ok := s.connType[deviceID]
relaysEnabled := s.relaysEnabled
s.mut.RUnlock()
if connected && ok && ct.IsDirect() {
continue
}
var addrs []string
var relays []discover.Relay
for _, addr := range deviceCfg.Addresses {
if addr == "dynamic" {
if s.discoverer != nil {
if t, r, err := s.discoverer.Lookup(deviceID); err == nil {
addrs = append(addrs, t...)
relays = append(relays, r...)
}
}
} else {
addrs = append(addrs, addr)
}
}
for _, addr := range addrs {
uri, err := url.Parse(addr)
if err != nil {
l.Infoln("Failed to parse connection url:", addr, err)
continue
}
dialer, ok := dialers[uri.Scheme]
if !ok {
l.Infoln("Unknown address schema", uri)
continue
}
l.Debugln("dial", deviceCfg.DeviceID, uri)
conn, err := dialer(uri, s.tlsCfg)
if err != nil {
l.Debugln("dial failed", deviceCfg.DeviceID, uri, err)
continue
}
if connected {
s.model.Close(deviceID, fmt.Errorf("switching connections"))
}
s.conns <- model.IntermediateConnection{
conn, model.ConnectionTypeDirectDial,
}
continue nextDevice
}
// Only connect via relays if not already connected
// Also, do not set lastRelayCheck time if we have no relays,
// as otherwise when we do discover relays, we might have to
// wait up to RelayReconnectIntervalM to connect again.
// Also, do not try relays if we are explicitly told not to.
if connected || len(relays) == 0 || !relaysEnabled {
continue nextDevice
}
reconIntv := time.Duration(s.cfg.Options().RelayReconnectIntervalM) * time.Minute
if last, ok := s.lastRelayCheck[deviceID]; ok && time.Since(last) < reconIntv {
l.Debugln("Skipping connecting via relay to", deviceID, "last checked at", last)
continue nextDevice
} else {
l.Debugln("Trying relay connections to", deviceID, relays)
}
s.lastRelayCheck[deviceID] = time.Now()
for _, addr := range relays {
uri, err := url.Parse(addr.URL)
if err != nil {
l.Infoln("Failed to parse relay connection url:", addr, err)
continue
}
inv, err := client.GetInvitationFromRelay(uri, deviceID, s.tlsCfg.Certificates)
if err != nil {
l.Debugf("Failed to get invitation for %s from %s: %v", deviceID, uri, err)
continue
} else {
l.Debugln("Succesfully retrieved relay invitation", inv, "from", uri)
}
conn, err := client.JoinSession(inv)
if err != nil {
l.Debugf("Failed to join relay session %s: %v", inv, err)
continue
} else {
l.Debugln("Sucessfully joined relay session", inv)
}
var tc *tls.Conn
if inv.ServerSocket {
tc = tls.Server(conn, s.tlsCfg)
} else {
tc = tls.Client(conn, s.tlsCfg)
}
err = tc.Handshake()
if err != nil {
l.Infof("TLS handshake (BEP/relay %s): %v", inv, err)
tc.Close()
continue
}
s.conns <- model.IntermediateConnection{
tc, model.ConnectionTypeRelayDial,
}
continue nextDevice
}
}
time.Sleep(delay)
delay *= 2
if maxD := time.Duration(s.cfg.Options().ReconnectIntervalS) * time.Second; delay > maxD {
delay = maxD
}
}
}
func (s *connectionSvc) acceptRelayConns() {
for {
conn := s.relaySvc.Accept()
s.conns <- model.IntermediateConnection{
Conn: conn,
Type: model.ConnectionTypeRelayAccept,
}
}
}
func (s *connectionSvc) shouldLimit(addr net.Addr) bool {
if s.cfg.Options().LimitBandwidthInLan {
return true
}
tcpaddr, ok := addr.(*net.TCPAddr)
if !ok {
return true
}
for _, lan := range s.lans {
if lan.Contains(tcpaddr.IP) {
return false
}
}
return !tcpaddr.IP.IsLoopback()
}
func (s *connectionSvc) VerifyConfiguration(from, to config.Configuration) error {
return nil
}
func (s *connectionSvc) CommitConfiguration(from, to config.Configuration) bool {
s.mut.Lock()
s.relaysEnabled = to.Options.RelaysEnabled
s.mut.Unlock()
// We require a restart if a device as been removed.
newDevices := make(map[protocol.DeviceID]bool, len(to.Devices))
for _, dev := range to.Devices {
newDevices[dev.DeviceID] = true
}
for _, dev := range from.Devices {
if !newDevices[dev.DeviceID] {
return false
}
}
return true
}
// serviceFunc wraps a function to create a suture.Service without stop
// functionality.
type serviceFunc func()
func (f serviceFunc) Serve() { f() }
func (f serviceFunc) Stop() {}