syncthing/lib/discover/global.go
Jakob Borg 7ebf58f1bc Fix discovery in the absence of listen addresses (fixes #4418)
This makes it OK to not have any listeners working. Specifically,

- We don't complain about an empty listener address
- We don't complain about not having anything to announce to global
  discovery servers
- We don't send local discovery packets when there is nothing to
  announce.

The last point also fixes a thing where the list of addresses for local
discovery was set at startup time and never refreshed.

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4517
2017-11-17 09:12:35 +00:00

391 lines
9.3 KiB
Go

// 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 discover
import (
"bytes"
"crypto/tls"
"encoding/json"
"errors"
"io"
"io/ioutil"
"net/http"
"net/url"
"strconv"
stdsync "sync"
"time"
"github.com/syncthing/syncthing/lib/dialer"
"github.com/syncthing/syncthing/lib/events"
"github.com/syncthing/syncthing/lib/protocol"
)
type globalClient struct {
server string
addrList AddressLister
announceClient httpClient
queryClient httpClient
noAnnounce bool
stop chan struct{}
errorHolder
}
type httpClient interface {
Get(url string) (*http.Response, error)
Post(url, ctype string, data io.Reader) (*http.Response, error)
}
const (
defaultReannounceInterval = 30 * time.Minute
announceErrorRetryInterval = 5 * time.Minute
requestTimeout = 5 * time.Second
)
type announcement struct {
Addresses []string `json:"addresses"`
}
type serverOptions struct {
insecure bool // don't check certificate
noAnnounce bool // don't announce
id string // expected server device ID
}
// A lookupError is any other error but with a cache validity time attached.
type lookupError struct {
error
cacheFor time.Duration
}
func (e lookupError) CacheFor() time.Duration {
return e.cacheFor
}
func NewGlobal(server string, cert tls.Certificate, addrList AddressLister) (FinderService, error) {
server, opts, err := parseOptions(server)
if err != nil {
return nil, err
}
var devID protocol.DeviceID
if opts.id != "" {
devID, err = protocol.DeviceIDFromString(opts.id)
if err != nil {
return nil, err
}
}
// The http.Client used for announcements. It needs to have our
// certificate to prove our identity, and may or may not verify the server
// certificate depending on the insecure setting.
var announceClient httpClient = &http.Client{
Timeout: requestTimeout,
Transport: &http.Transport{
Dial: dialer.Dial,
Proxy: http.ProxyFromEnvironment,
TLSClientConfig: &tls.Config{
InsecureSkipVerify: opts.insecure,
Certificates: []tls.Certificate{cert},
},
},
}
if opts.id != "" {
announceClient = newIDCheckingHTTPClient(announceClient, devID)
}
// The http.Client used for queries. We don't need to present our
// certificate here, so lets not include it. May be insecure if requested.
var queryClient httpClient = &http.Client{
Timeout: requestTimeout,
Transport: &http.Transport{
Dial: dialer.Dial,
Proxy: http.ProxyFromEnvironment,
TLSClientConfig: &tls.Config{
InsecureSkipVerify: opts.insecure,
},
},
}
if opts.id != "" {
queryClient = newIDCheckingHTTPClient(queryClient, devID)
}
cl := &globalClient{
server: server,
addrList: addrList,
announceClient: announceClient,
queryClient: queryClient,
noAnnounce: opts.noAnnounce,
stop: make(chan struct{}),
}
cl.setError(errors.New("not announced"))
return cl, nil
}
// Lookup returns the list of addresses where the given device is available
func (c *globalClient) Lookup(device protocol.DeviceID) (addresses []string, err error) {
qURL, err := url.Parse(c.server)
if err != nil {
return nil, err
}
q := qURL.Query()
q.Set("device", device.String())
qURL.RawQuery = q.Encode()
resp, err := c.queryClient.Get(qURL.String())
if err != nil {
l.Debugln("globalClient.Lookup", qURL, err)
return nil, err
}
if resp.StatusCode != 200 {
resp.Body.Close()
l.Debugln("globalClient.Lookup", qURL, resp.Status)
err := errors.New(resp.Status)
if secs, atoiErr := strconv.Atoi(resp.Header.Get("Retry-After")); atoiErr == nil && secs > 0 {
err = lookupError{
error: err,
cacheFor: time.Duration(secs) * time.Second,
}
}
return nil, err
}
bs, err := ioutil.ReadAll(resp.Body)
if err != nil {
return nil, err
}
resp.Body.Close()
var ann announcement
err = json.Unmarshal(bs, &ann)
return ann.Addresses, err
}
func (c *globalClient) String() string {
return "global@" + c.server
}
func (c *globalClient) Serve() {
if c.noAnnounce {
// We're configured to not do announcements, only lookups. To maintain
// the same interface, we just pause here if Serve() is run.
<-c.stop
return
}
timer := time.NewTimer(0)
defer timer.Stop()
eventSub := events.Default.Subscribe(events.ListenAddressesChanged)
defer events.Default.Unsubscribe(eventSub)
for {
select {
case <-eventSub.C():
// Defer announcement by 2 seconds, essentially debouncing
// if we have a stream of events incoming in quick succession.
timer.Reset(2 * time.Second)
case <-timer.C:
c.sendAnnouncement(timer)
case <-c.stop:
return
}
}
}
func (c *globalClient) sendAnnouncement(timer *time.Timer) {
var ann announcement
if c.addrList != nil {
ann.Addresses = c.addrList.ExternalAddresses()
}
if len(ann.Addresses) == 0 {
// There are legitimate cases for not having anything to announce,
// yet still using global discovery for lookups. Do not error out
// here.
c.setError(nil)
timer.Reset(announceErrorRetryInterval)
return
}
// The marshal doesn't fail, I promise.
postData, _ := json.Marshal(ann)
l.Debugf("Announcement: %s", postData)
resp, err := c.announceClient.Post(c.server, "application/json", bytes.NewReader(postData))
if err != nil {
l.Debugln("announce POST:", err)
c.setError(err)
timer.Reset(announceErrorRetryInterval)
return
}
l.Debugln("announce POST:", resp.Status)
resp.Body.Close()
if resp.StatusCode < 200 || resp.StatusCode > 299 {
l.Debugln("announce POST:", resp.Status)
c.setError(errors.New(resp.Status))
if h := resp.Header.Get("Retry-After"); h != "" {
// The server has a recommendation on when we should
// retry. Follow it.
if secs, err := strconv.Atoi(h); err == nil && secs > 0 {
l.Debugln("announce Retry-After:", secs, err)
timer.Reset(time.Duration(secs) * time.Second)
return
}
}
timer.Reset(announceErrorRetryInterval)
return
}
c.setError(nil)
if h := resp.Header.Get("Reannounce-After"); h != "" {
// The server has a recommendation on when we should
// reannounce. Follow it.
if secs, err := strconv.Atoi(h); err == nil && secs > 0 {
l.Debugln("announce Reannounce-After:", secs, err)
timer.Reset(time.Duration(secs) * time.Second)
return
}
}
timer.Reset(defaultReannounceInterval)
}
func (c *globalClient) Stop() {
close(c.stop)
}
func (c *globalClient) Cache() map[protocol.DeviceID]CacheEntry {
// The globalClient doesn't do caching
return nil
}
// parseOptions parses and strips away any ?query=val options, setting the
// corresponding field in the serverOptions struct. Unknown query options are
// ignored and removed.
func parseOptions(dsn string) (server string, opts serverOptions, err error) {
p, err := url.Parse(dsn)
if err != nil {
return "", serverOptions{}, err
}
// Grab known options from the query string
q := p.Query()
opts.id = q.Get("id")
opts.insecure = opts.id != "" || queryBool(q, "insecure")
opts.noAnnounce = queryBool(q, "noannounce")
// Check for disallowed combinations
if p.Scheme == "http" {
if !opts.insecure {
return "", serverOptions{}, errors.New("http without insecure not supported")
}
if !opts.noAnnounce {
return "", serverOptions{}, errors.New("http without noannounce not supported")
}
} else if p.Scheme != "https" {
return "", serverOptions{}, errors.New("unsupported scheme " + p.Scheme)
}
// Remove the query string
p.RawQuery = ""
server = p.String()
return
}
// queryBool returns the query parameter parsed as a boolean. An empty value
// ("?foo") is considered true, as is any value string except false
// ("?foo=false").
func queryBool(q url.Values, key string) bool {
if _, ok := q[key]; !ok {
return false
}
return q.Get(key) != "false"
}
type idCheckingHTTPClient struct {
httpClient
id protocol.DeviceID
}
func newIDCheckingHTTPClient(client httpClient, id protocol.DeviceID) *idCheckingHTTPClient {
return &idCheckingHTTPClient{
httpClient: client,
id: id,
}
}
func (c *idCheckingHTTPClient) check(resp *http.Response) error {
if resp.TLS == nil {
return errors.New("security: not TLS")
}
if len(resp.TLS.PeerCertificates) == 0 {
return errors.New("security: no certificates")
}
id := protocol.NewDeviceID(resp.TLS.PeerCertificates[0].Raw)
if !id.Equals(c.id) {
return errors.New("security: incorrect device id")
}
return nil
}
func (c *idCheckingHTTPClient) Get(url string) (*http.Response, error) {
resp, err := c.httpClient.Get(url)
if err != nil {
return nil, err
}
if err := c.check(resp); err != nil {
return nil, err
}
return resp, nil
}
func (c *idCheckingHTTPClient) Post(url, ctype string, data io.Reader) (*http.Response, error) {
resp, err := c.httpClient.Post(url, ctype, data)
if err != nil {
return nil, err
}
if err := c.check(resp); err != nil {
return nil, err
}
return resp, nil
}
type errorHolder struct {
err error
mut stdsync.Mutex // uses stdlib sync as I want this to be trivially embeddable, and there is no risk of blocking
}
func (e *errorHolder) setError(err error) {
e.mut.Lock()
e.err = err
e.mut.Unlock()
}
func (e *errorHolder) Error() error {
e.mut.Lock()
err := e.err
e.mut.Unlock()
return err
}