syncthing/lib/connections/service.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 https://mozilla.org/MPL/2.0/.
package connections
import (
"context"
"crypto/tls"
"fmt"
"net"
"net/url"
"sort"
"strings"
stdsync "sync"
"time"
"github.com/syncthing/syncthing/lib/config"
"github.com/syncthing/syncthing/lib/discover"
"github.com/syncthing/syncthing/lib/events"
"github.com/syncthing/syncthing/lib/nat"
"github.com/syncthing/syncthing/lib/osutil"
"github.com/syncthing/syncthing/lib/protocol"
"github.com/syncthing/syncthing/lib/sync"
"github.com/syncthing/syncthing/lib/util"
// Registers NAT service providers
_ "github.com/syncthing/syncthing/lib/pmp"
_ "github.com/syncthing/syncthing/lib/upnp"
"github.com/pkg/errors"
"github.com/thejerf/suture"
"golang.org/x/time/rate"
)
var (
dialers = make(map[string]dialerFactory)
listeners = make(map[string]listenerFactory)
)
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var (
errDisabled = errors.New("disabled by configuration")
errDeprecated = errors.New("deprecated protocol")
)
const (
perDeviceWarningIntv = 15 * time.Minute
tlsHandshakeTimeout = 10 * time.Second
)
// From go/src/crypto/tls/cipher_suites.go
var tlsCipherSuiteNames = map[uint16]string{
// TLS 1.2
0x0005: "TLS_RSA_WITH_RC4_128_SHA",
0x000a: "TLS_RSA_WITH_3DES_EDE_CBC_SHA",
0x002f: "TLS_RSA_WITH_AES_128_CBC_SHA",
0x0035: "TLS_RSA_WITH_AES_256_CBC_SHA",
0x003c: "TLS_RSA_WITH_AES_128_CBC_SHA256",
0x009c: "TLS_RSA_WITH_AES_128_GCM_SHA256",
0x009d: "TLS_RSA_WITH_AES_256_GCM_SHA384",
0xc007: "TLS_ECDHE_ECDSA_WITH_RC4_128_SHA",
0xc009: "TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA",
0xc00a: "TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA",
0xc011: "TLS_ECDHE_RSA_WITH_RC4_128_SHA",
0xc012: "TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA",
0xc013: "TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA",
0xc014: "TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA",
0xc023: "TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256",
0xc027: "TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256",
0xc02f: "TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256",
0xc02b: "TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256",
0xc030: "TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384",
0xc02c: "TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384",
0xcca8: "TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305",
0xcca9: "TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305",
// TLS 1.3
0x1301: "TLS_AES_128_GCM_SHA256",
0x1302: "TLS_AES_256_GCM_SHA384",
0x1303: "TLS_CHACHA20_POLY1305_SHA256",
}
var tlsVersionNames = map[uint16]string{
tls.VersionTLS12: "TLS1.2",
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tls.VersionTLS13: "TLS1.3",
}
// Service listens and dials all configured unconnected devices, via supported
// dialers. Successful connections are handed to the model.
type Service interface {
suture.Service
discover.AddressLister
ListenerStatus() map[string]ListenerStatusEntry
ConnectionStatus() map[string]ConnectionStatusEntry
NATType() string
}
type ListenerStatusEntry struct {
Error *string `json:"error"`
LANAddresses []string `json:"lanAddresses"`
WANAddresses []string `json:"wanAddresses"`
}
type ConnectionStatusEntry struct {
When time.Time `json:"when"`
Error *string `json:"error"`
}
type service struct {
*suture.Supervisor
cfg config.Wrapper
myID protocol.DeviceID
model Model
tlsCfg *tls.Config
discoverer discover.Finder
conns chan internalConn
bepProtocolName string
tlsDefaultCommonName string
limiter *limiter
natService *nat.Service
natServiceToken *suture.ServiceToken
evLogger events.Logger
listenersMut sync.RWMutex
listeners map[string]genericListener
listenerTokens map[string]suture.ServiceToken
listenerSupervisor *suture.Supervisor
connectionStatusMut sync.RWMutex
connectionStatus map[string]ConnectionStatusEntry // address -> latest error/status
}
func NewService(cfg config.Wrapper, myID protocol.DeviceID, mdl Model, tlsCfg *tls.Config, discoverer discover.Finder, bepProtocolName string, tlsDefaultCommonName string, evLogger events.Logger) Service {
service := &service{
Supervisor: suture.New("connections.Service", suture.Spec{
Log: func(line string) {
l.Infoln(line)
},
PassThroughPanics: true,
}),
cfg: cfg,
myID: myID,
model: mdl,
tlsCfg: tlsCfg,
discoverer: discoverer,
conns: make(chan internalConn),
bepProtocolName: bepProtocolName,
tlsDefaultCommonName: tlsDefaultCommonName,
limiter: newLimiter(cfg),
natService: nat.NewService(myID, cfg),
evLogger: evLogger,
listenersMut: sync.NewRWMutex(),
listeners: make(map[string]genericListener),
listenerTokens: make(map[string]suture.ServiceToken),
// A listener can fail twice, rapidly. Any more than that and it
// will be put on suspension for ten minutes. Restarts and changes
// due to config are done by removing and adding services, so are
// not subject to these limitations.
listenerSupervisor: suture.New("c.S.listenerSupervisor", suture.Spec{
Log: func(line string) {
l.Infoln(line)
},
FailureThreshold: 2,
FailureBackoff: 600 * time.Second,
PassThroughPanics: true,
}),
connectionStatusMut: sync.NewRWMutex(),
connectionStatus: make(map[string]ConnectionStatusEntry),
}
cfg.Subscribe(service)
raw := cfg.RawCopy()
// Actually starts the listeners and NAT service
// Need to start this before service.connect so that any dials that
// try punch through already have a listener to cling on.
service.CommitConfiguration(raw, raw)
// There are several moving parts here; one routine per listening address
// (handled in configuration changing) to handle incoming connections,
// one routine to periodically attempt outgoing connections, one routine to
// the common handling regardless of whether the connection was
// incoming or outgoing.
service.Add(util.AsService(service.connect, fmt.Sprintf("%s/connect", service)))
service.Add(util.AsService(service.handle, fmt.Sprintf("%s/handle", service)))
service.Add(service.listenerSupervisor)
return service
}
func (s *service) Stop() {
s.cfg.Unsubscribe(s.limiter)
s.cfg.Unsubscribe(s)
s.Supervisor.Stop()
}
func (s *service) handle(ctx context.Context) {
var c internalConn
for {
select {
case <-ctx.Done():
return
case c = <-s.conns:
}
cs := c.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 at %s did not negotiate bep/1.0", c)
}
// 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 peer at %s; protocol error", cl, c)
c.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) at %s - should not happen", remoteID, c)
c.Close()
continue
}
_ = c.SetDeadline(time.Now().Add(20 * time.Second))
hello, err := protocol.ExchangeHello(c, s.model.GetHello(remoteID))
if err != nil {
if protocol.IsVersionMismatch(err) {
// The error will be a relatively user friendly description
// of what's wrong with the version compatibility. By
// default identify the other side by device ID and IP.
remote := fmt.Sprintf("%v (%v)", remoteID, c.RemoteAddr())
if hello.DeviceName != "" {
// If the name was set in the hello return, use that to
// give the user more info about which device is the
// affected one. It probably says more than the remote
// IP.
remote = fmt.Sprintf("%q (%s %s, %v)", hello.DeviceName, hello.ClientName, hello.ClientVersion, remoteID)
}
msg := fmt.Sprintf("Connecting to %s: %s", remote, err)
warningFor(remoteID, msg)
} else {
// It's something else - connection reset or whatever
l.Infof("Failed to exchange Hello messages with %s at %s: %s", remoteID, c, err)
}
c.Close()
continue
}
_ = c.SetDeadline(time.Time{})
// The Model will return an error for devices that we don't want to
// have a connection with for whatever reason, for example unknown devices.
if err := s.model.OnHello(remoteID, c.RemoteAddr(), hello); err != nil {
l.Infof("Connection from %s at %s (%s) rejected: %v", remoteID, c.RemoteAddr(), c.Type(), err)
c.Close()
continue
}
// If we have a relay connection, and the new incoming connection is
// not a relay connection, we should drop that, and prefer this one.
ct, connected := s.model.Connection(remoteID)
// Lower priority is better, just like nice etc.
if connected && ct.Priority() > c.priority {
l.Debugf("Switching connections %s (existing: %s new: %s)", remoteID, ct, c)
} else if connected {
// 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 (existing: %s new: %s)", remoteID, ct, c)
c.Close()
continue
}
deviceCfg, ok := s.cfg.Device(remoteID)
if !ok {
l.Infof("Device %s removed from config during connection attempt at %s", remoteID, c)
c.Close()
continue
}
// 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
}
if err := remoteCert.VerifyHostname(certName); 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 at %s: %v", remoteID, c, err)
c.Close()
continue
}
// Wrap the connection in rate limiters. The limiter itself will
// keep up with config changes to the rate and whether or not LAN
// connections are limited.
isLAN := s.isLAN(c.RemoteAddr())
rd, wr := s.limiter.getLimiters(remoteID, c, isLAN)
protoConn := protocol.NewConnection(remoteID, rd, wr, s.model, c.String(), deviceCfg.Compression)
modelConn := completeConn{c, protoConn}
l.Infof("Established secure connection to %s at %s", remoteID, c)
s.model.AddConnection(modelConn, hello)
continue
}
}
func (s *service) connect(ctx context.Context) {
nextDial := make(map[string]time.Time)
// Used as delay for the first few connection attempts, increases
// exponentially
initialRampup := time.Second
// Calculated from actual dialers reconnectInterval
var sleep time.Duration
for {
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cfg := s.cfg.RawCopy()
bestDialerPrio := 1<<31 - 1 // worse prio won't build on 32 bit
for _, df := range dialers {
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if df.Valid(cfg) != nil {
continue
}
if prio := df.Priority(); prio < bestDialerPrio {
bestDialerPrio = prio
}
}
l.Debugln("Reconnect loop")
now := time.Now()
var seen []string
for _, deviceCfg := range cfg.Devices {
deviceID := deviceCfg.DeviceID
if deviceID == s.myID {
continue
}
if deviceCfg.Paused {
continue
}
ct, connected := s.model.Connection(deviceID)
if connected && ct.Priority() == bestDialerPrio {
// Things are already as good as they can get.
continue
}
var addrs []string
for _, addr := range deviceCfg.Addresses {
if addr == "dynamic" {
if s.discoverer != nil {
if t, err := s.discoverer.Lookup(deviceID); err == nil {
addrs = append(addrs, t...)
}
}
} else {
addrs = append(addrs, addr)
}
}
addrs = util.UniqueTrimmedStrings(addrs)
l.Debugln("Reconnect loop for", deviceID, addrs)
dialTargets := make([]dialTarget, 0)
for _, addr := range addrs {
// Use a special key that is more than just the address, as you might have two devices connected to the same relay
nextDialKey := deviceID.String() + "/" + addr
seen = append(seen, nextDialKey)
nextDialAt, ok := nextDial[nextDialKey]
if ok && initialRampup >= sleep && nextDialAt.After(now) {
l.Debugf("Not dialing %s via %v as sleep is %v, next dial is at %s and current time is %s", deviceID, addr, sleep, nextDialAt, now)
continue
}
// If we fail at any step before actually getting the dialer
// retry in a minute
nextDial[nextDialKey] = now.Add(time.Minute)
uri, err := url.Parse(addr)
if err != nil {
s.setConnectionStatus(addr, err)
l.Infof("Parsing dialer address %s: %v", addr, err)
continue
}
if len(deviceCfg.AllowedNetworks) > 0 {
if !IsAllowedNetwork(uri.Host, deviceCfg.AllowedNetworks) {
s.setConnectionStatus(addr, errors.New("network disallowed"))
l.Debugln("Network for", uri, "is disallowed")
continue
}
}
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dialerFactory, err := getDialerFactory(cfg, uri)
if err != nil {
s.setConnectionStatus(addr, err)
}
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switch err {
case nil:
// all good
case errDisabled:
l.Debugln("Dialer for", uri, "is disabled")
continue
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case errDeprecated:
l.Debugln("Dialer for", uri, "is deprecated")
continue
default:
l.Infof("Dialer for %v: %v", uri, err)
continue
}
priority := dialerFactory.Priority()
if connected && priority >= ct.Priority() {
l.Debugf("Not dialing using %s as priority is less than current connection (%d >= %d)", dialerFactory, dialerFactory.Priority(), ct.Priority())
continue
}
dialer := dialerFactory.New(s.cfg.Options(), s.tlsCfg)
nextDial[nextDialKey] = now.Add(dialer.RedialFrequency())
// For LAN addresses, increase the priority so that we
// try these first.
switch {
case dialerFactory.AlwaysWAN():
// Do nothing.
case s.isLANHost(uri.Host):
priority -= 1
}
dialTargets = append(dialTargets, dialTarget{
addr: addr,
dialer: dialer,
priority: priority,
deviceID: deviceID,
uri: uri,
})
}
conn, ok := s.dialParallel(ctx, deviceCfg.DeviceID, dialTargets)
if ok {
s.conns <- conn
}
}
nextDial, sleep = filterAndFindSleepDuration(nextDial, seen, now)
if initialRampup < sleep {
l.Debugln("initial rampup; sleep", initialRampup, "and update to", initialRampup*2)
sleep = initialRampup
initialRampup *= 2
} else {
l.Debugln("sleep until next dial", sleep)
}
select {
case <-time.After(sleep):
case <-ctx.Done():
return
}
}
}
func (s *service) isLANHost(host string) bool {
// Probably we are called with an ip:port combo which we can resolve as
// a TCP address.
if addr, err := net.ResolveTCPAddr("tcp", host); err == nil {
return s.isLAN(addr)
}
// ... but this function looks general enough that someone might try
// with just an IP as well in the future so lets allow that.
if addr, err := net.ResolveIPAddr("ip", host); err == nil {
return s.isLAN(addr)
}
return false
}
func (s *service) isLAN(addr net.Addr) bool {
var ip net.IP
switch addr := addr.(type) {
case *net.IPAddr:
ip = addr.IP
case *net.TCPAddr:
ip = addr.IP
case *net.UDPAddr:
ip = addr.IP
default:
// From the standard library, just Unix sockets.
// If you invent your own, handle it.
return false
}
if ip.IsLoopback() {
return true
}
for _, lan := range s.cfg.Options().AlwaysLocalNets {
_, ipnet, err := net.ParseCIDR(lan)
if err != nil {
l.Debugln("Network", lan, "is malformed:", err)
continue
}
if ipnet.Contains(ip) {
return true
}
}
lans, _ := osutil.GetLans()
for _, lan := range lans {
if lan.Contains(ip) {
return true
}
}
return false
}
func (s *service) createListener(factory listenerFactory, uri *url.URL) bool {
// must be called with listenerMut held
l.Debugln("Starting listener", uri)
listener := factory.New(uri, s.cfg, s.tlsCfg, s.conns, s.natService)
listener.OnAddressesChanged(s.logListenAddressesChangedEvent)
s.listeners[uri.String()] = listener
s.listenerTokens[uri.String()] = s.listenerSupervisor.Add(listener)
return true
}
func (s *service) logListenAddressesChangedEvent(l genericListener) {
s.evLogger.Log(events.ListenAddressesChanged, map[string]interface{}{
"address": l.URI(),
"lan": l.LANAddresses(),
"wan": l.WANAddresses(),
})
}
func (s *service) VerifyConfiguration(from, to config.Configuration) error {
return nil
}
func (s *service) CommitConfiguration(from, to config.Configuration) bool {
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] {
warningLimitersMut.Lock()
delete(warningLimiters, dev.DeviceID)
warningLimitersMut.Unlock()
}
}
s.listenersMut.Lock()
seen := make(map[string]struct{})
for _, addr := range to.Options.ListenAddresses() {
if addr == "" {
// We can get an empty address if there is an empty listener
// element in the config, indicating no listeners should be
// used. This is not an error.
continue
}
if _, ok := s.listeners[addr]; ok {
seen[addr] = struct{}{}
continue
}
uri, err := url.Parse(addr)
if err != nil {
l.Infof("Parsing listener address %s: %v", addr, err)
continue
}
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factory, err := getListenerFactory(to, uri)
switch err {
case nil:
// all good
case errDisabled:
l.Debugln("Listener for", uri, "is disabled")
continue
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case errDeprecated:
l.Debugln("Listener for", uri, "is deprecated")
continue
default:
l.Infof("Listener for %v: %v", uri, err)
continue
}
s.createListener(factory, uri)
seen[addr] = struct{}{}
}
for addr, listener := range s.listeners {
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if _, ok := seen[addr]; !ok || listener.Factory().Valid(to) != nil {
l.Debugln("Stopping listener", addr)
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s.listenerSupervisor.Remove(s.listenerTokens[addr])
delete(s.listenerTokens, addr)
delete(s.listeners, addr)
}
}
s.listenersMut.Unlock()
if to.Options.NATEnabled && s.natServiceToken == nil {
l.Debugln("Starting NAT service")
token := s.Add(s.natService)
s.natServiceToken = &token
} else if !to.Options.NATEnabled && s.natServiceToken != nil {
l.Debugln("Stopping NAT service")
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s.Remove(*s.natServiceToken)
s.natServiceToken = nil
}
return true
}
func (s *service) AllAddresses() []string {
s.listenersMut.RLock()
var addrs []string
for _, listener := range s.listeners {
for _, lanAddr := range listener.LANAddresses() {
addrs = append(addrs, lanAddr.String())
}
for _, wanAddr := range listener.WANAddresses() {
addrs = append(addrs, wanAddr.String())
}
}
s.listenersMut.RUnlock()
return util.UniqueTrimmedStrings(addrs)
}
func (s *service) ExternalAddresses() []string {
s.listenersMut.RLock()
var addrs []string
for _, listener := range s.listeners {
for _, wanAddr := range listener.WANAddresses() {
addrs = append(addrs, wanAddr.String())
}
}
s.listenersMut.RUnlock()
return util.UniqueTrimmedStrings(addrs)
}
func (s *service) ListenerStatus() map[string]ListenerStatusEntry {
result := make(map[string]ListenerStatusEntry)
s.listenersMut.RLock()
for addr, listener := range s.listeners {
var status ListenerStatusEntry
if err := listener.Error(); err != nil {
errStr := err.Error()
status.Error = &errStr
}
status.LANAddresses = urlsToStrings(listener.LANAddresses())
status.WANAddresses = urlsToStrings(listener.WANAddresses())
result[addr] = status
}
s.listenersMut.RUnlock()
return result
}
func (s *service) ConnectionStatus() map[string]ConnectionStatusEntry {
result := make(map[string]ConnectionStatusEntry)
s.connectionStatusMut.RLock()
for k, v := range s.connectionStatus {
result[k] = v
}
s.connectionStatusMut.RUnlock()
return result
}
func (s *service) setConnectionStatus(address string, err error) {
if errors.Cause(err) != context.Canceled {
return
}
status := ConnectionStatusEntry{When: time.Now().UTC().Truncate(time.Second)}
if err != nil {
errStr := err.Error()
status.Error = &errStr
}
s.connectionStatusMut.Lock()
s.connectionStatus[address] = status
s.connectionStatusMut.Unlock()
}
func (s *service) NATType() string {
s.listenersMut.RLock()
defer s.listenersMut.RUnlock()
for _, listener := range s.listeners {
natType := listener.NATType()
if natType != "unknown" {
return natType
}
}
return "unknown"
}
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func getDialerFactory(cfg config.Configuration, uri *url.URL) (dialerFactory, error) {
dialerFactory, ok := dialers[uri.Scheme]
if !ok {
return nil, fmt.Errorf("unknown address scheme %q", uri.Scheme)
}
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if err := dialerFactory.Valid(cfg); err != nil {
return nil, err
}
return dialerFactory, nil
}
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func getListenerFactory(cfg config.Configuration, uri *url.URL) (listenerFactory, error) {
listenerFactory, ok := listeners[uri.Scheme]
if !ok {
return nil, fmt.Errorf("unknown address scheme %q", uri.Scheme)
}
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if err := listenerFactory.Valid(cfg); err != nil {
return nil, err
}
return listenerFactory, nil
}
func filterAndFindSleepDuration(nextDial map[string]time.Time, seen []string, now time.Time) (map[string]time.Time, time.Duration) {
newNextDial := make(map[string]time.Time)
for _, addr := range seen {
nextDialAt, ok := nextDial[addr]
if ok {
newNextDial[addr] = nextDialAt
}
}
min := time.Minute
for _, next := range newNextDial {
cur := next.Sub(now)
if cur < min {
min = cur
}
}
return newNextDial, min
}
func urlsToStrings(urls []*url.URL) []string {
strings := make([]string, len(urls))
for i, url := range urls {
strings[i] = url.String()
}
return strings
}
var warningLimiters = make(map[protocol.DeviceID]*rate.Limiter)
var warningLimitersMut = sync.NewMutex()
func warningFor(dev protocol.DeviceID, msg string) {
warningLimitersMut.Lock()
defer warningLimitersMut.Unlock()
lim, ok := warningLimiters[dev]
if !ok {
lim = rate.NewLimiter(rate.Every(perDeviceWarningIntv), 1)
warningLimiters[dev] = lim
}
if lim.Allow() {
l.Warnln(msg)
}
}
func tlsTimedHandshake(tc *tls.Conn) error {
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tc.SetDeadline(time.Now().Add(tlsHandshakeTimeout))
defer tc.SetDeadline(time.Time{})
return tc.Handshake()
}
// IsAllowedNetwork returns true if the given host (IP or resolvable
// hostname) is in the set of allowed networks (CIDR format only).
func IsAllowedNetwork(host string, allowed []string) bool {
if hostNoPort, _, err := net.SplitHostPort(host); err == nil {
host = hostNoPort
}
addr, err := net.ResolveIPAddr("ip", host)
if err != nil {
return false
}
for _, n := range allowed {
result := true
if strings.HasPrefix(n, "!") {
result = false
n = n[1:]
}
_, cidr, err := net.ParseCIDR(n)
if err != nil {
continue
}
if cidr.Contains(addr.IP) {
return result
}
}
return false
}
func (s *service) dialParallel(ctx context.Context, deviceID protocol.DeviceID, dialTargets []dialTarget) (internalConn, bool) {
// Group targets into buckets by priority
dialTargetBuckets := make(map[int][]dialTarget, len(dialTargets))
for _, tgt := range dialTargets {
dialTargetBuckets[tgt.priority] = append(dialTargetBuckets[tgt.priority], tgt)
}
// Get all available priorities
priorities := make([]int, 0, len(dialTargetBuckets))
for prio := range dialTargetBuckets {
priorities = append(priorities, prio)
}
// Sort the priorities so that we dial lowest first (which means highest...)
sort.Ints(priorities)
for _, prio := range priorities {
tgts := dialTargetBuckets[prio]
res := make(chan internalConn, len(tgts))
wg := stdsync.WaitGroup{}
for _, tgt := range tgts {
wg.Add(1)
go func(tgt dialTarget) {
conn, err := tgt.Dial(ctx)
if err == nil {
// Closes the connection on error
err = s.validateIdentity(conn, deviceID)
}
s.setConnectionStatus(tgt.addr, err)
if err != nil {
l.Debugln("dialing", deviceID, tgt.uri, "error:", err)
} else {
l.Debugln("dialing", deviceID, tgt.uri, "success:", conn)
res <- conn
}
wg.Done()
}(tgt)
}
// Spawn a routine which will unblock main routine in case we fail
// to connect to anyone.
go func() {
wg.Wait()
close(res)
}()
// Wait for the first connection, or for channel closure.
if conn, ok := <-res; ok {
// Got a connection, means more might come back, hence spawn a
// routine that will do the discarding.
l.Debugln("connected to", deviceID, prio, "using", conn, conn.priority)
go func(deviceID protocol.DeviceID, prio int) {
wg.Wait()
l.Debugln("discarding", len(res), "connections while connecting to", deviceID, prio)
for conn := range res {
conn.Close()
}
}(deviceID, prio)
return conn, ok
}
// Failed to connect, report that fact.
l.Debugln("failed to connect to", deviceID, prio)
}
return internalConn{}, false
}
func (s *service) validateIdentity(c internalConn, expectedID protocol.DeviceID) error {
cs := c.ConnectionState()
// 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 peer at %s; protocol error", cl, c)
c.Close()
return fmt.Errorf("expected 1 certificate, got %d", cl)
}
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) at %s - should not happen", remoteID, c)
c.Close()
return fmt.Errorf("connected to self")
}
// We should see the expected device ID
if !remoteID.Equals(expectedID) {
c.Close()
return fmt.Errorf("unexpected device id, expected %s got %s", expectedID, remoteID)
}
return nil
}