// remoteServerListFetcher fetches an out-of-band list of server entries
// for more tunnel candidates. It fetches when signalled, with retries
// on failure.
func (controller *Controller) remoteServerListFetcher() {
	defer controller.runWaitGroup.Done()

	if controller.config.RemoteServerListUrl == "" {
		NoticeAlert("remote server list URL is blank")
		return
	}
	if controller.config.RemoteServerListSignaturePublicKey == "" {
		NoticeAlert("remote server list signature public key blank")
		return
	}

	var lastFetchTime monotime.Time

fetcherLoop:
	for {
		// Wait for a signal before fetching
		select {
		case <-controller.signalFetchRemoteServerList:
		case <-controller.shutdownBroadcast:
			break fetcherLoop
		}

		// Skip fetch entirely (i.e., send no request at all, even when ETag would save
		// on response size) when a recent fetch was successful
		if lastFetchTime != 0 &&
			lastFetchTime.Add(FETCH_REMOTE_SERVER_LIST_STALE_PERIOD).After(monotime.Now()) {
			continue
		}

	retryLoop:
		for {
			// Don't attempt to fetch while there is no network connectivity,
			// to avoid alert notice noise.
			if !WaitForNetworkConnectivity(
				controller.config.NetworkConnectivityChecker,
				controller.shutdownBroadcast) {
				break fetcherLoop
			}

			// Pick any active tunnel and make the next fetch attempt. If there's
			// no active tunnel, the untunneledDialConfig will be used.
			tunnel := controller.getNextActiveTunnel()

			err := FetchRemoteServerList(
				controller.config,
				tunnel,
				controller.untunneledDialConfig)

			if err == nil {
				lastFetchTime = monotime.Now()
				break retryLoop
			}

			NoticeAlert("failed to fetch remote server list: %s", err)

			timeout := time.After(
				time.Duration(*controller.config.FetchRemoteServerListRetryPeriodSeconds) * time.Second)
			select {
			case <-timeout:
			case <-controller.shutdownBroadcast:
				break fetcherLoop
			}
		}
	}

	NoticeInfo("exiting remote server list fetcher")
}
// upgradeDownloader makes periodic attemps to complete a client upgrade
// download. DownloadUpgrade() is resumable, so each attempt has potential for
// getting closer to completion, even in conditions where the download or
// tunnel is repeatedly interrupted.
// An upgrade download is triggered by either a handshake response indicating
// that a new version is available; or after failing to connect, in which case
// it's useful to check, out-of-band, for an upgrade with new circumvention
// capabilities.
// Once the download operation completes successfully, the downloader exits
// and is not run again: either there is not a newer version, or the upgrade
// has been downloaded and is ready to be applied.
// We're assuming that the upgrade will be applied and the entire system
// restarted before another upgrade is to be downloaded.
//
// TODO: refactor upgrade downloader and remote server list fetcher to use
// common code (including the resumable download routines).
//
func (controller *Controller) upgradeDownloader() {
	defer controller.runWaitGroup.Done()

	var lastDownloadTime monotime.Time

downloadLoop:
	for {
		// Wait for a signal before downloading
		var handshakeVersion string
		select {
		case handshakeVersion = <-controller.signalDownloadUpgrade:
		case <-controller.shutdownBroadcast:
			break downloadLoop
		}

		// Unless handshake is explicitly advertizing a new version, skip
		// checking entirely when a recent download was successful.
		if handshakeVersion == "" &&
			lastDownloadTime != 0 &&
			lastDownloadTime.Add(DOWNLOAD_UPGRADE_STALE_PERIOD).After(monotime.Now()) {
			continue
		}

	retryLoop:
		for {
			// Don't attempt to download while there is no network connectivity,
			// to avoid alert notice noise.
			if !WaitForNetworkConnectivity(
				controller.config.NetworkConnectivityChecker,
				controller.shutdownBroadcast) {
				break downloadLoop
			}

			// Pick any active tunnel and make the next download attempt. If there's
			// no active tunnel, the untunneledDialConfig will be used.
			tunnel := controller.getNextActiveTunnel()

			err := DownloadUpgrade(
				controller.config,
				handshakeVersion,
				tunnel,
				controller.untunneledDialConfig)

			if err == nil {
				lastDownloadTime = monotime.Now()
				break retryLoop
			}

			NoticeAlert("failed to download upgrade: %s", err)

			timeout := time.After(
				time.Duration(*controller.config.DownloadUpgradeRetryPeriodSeconds) * time.Second)
			select {
			case <-timeout:
			case <-controller.shutdownBroadcast:
				break downloadLoop
			}
		}
	}

	NoticeInfo("exiting upgrade downloader")
}
Exemplo n.º 3
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// remoteServerListFetcher fetches an out-of-band list of server entries
// for more tunnel candidates. It fetches when signalled, with retries
// on failure.
func (controller *Controller) remoteServerListFetcher(
	name string,
	fetcher RemoteServerListFetcher,
	signal <-chan struct{},
	retryPeriod, stalePeriod time.Duration) {

	defer controller.runWaitGroup.Done()

	var lastFetchTime monotime.Time

fetcherLoop:
	for {
		// Wait for a signal before fetching
		select {
		case <-signal:
		case <-controller.shutdownBroadcast:
			break fetcherLoop
		}

		// Skip fetch entirely (i.e., send no request at all, even when ETag would save
		// on response size) when a recent fetch was successful
		if lastFetchTime != 0 &&
			lastFetchTime.Add(stalePeriod).After(monotime.Now()) {
			continue
		}

	retryLoop:
		for {
			// Don't attempt to fetch while there is no network connectivity,
			// to avoid alert notice noise.
			if !WaitForNetworkConnectivity(
				controller.config.NetworkConnectivityChecker,
				controller.shutdownBroadcast) {
				break fetcherLoop
			}

			// Pick any active tunnel and make the next fetch attempt. If there's
			// no active tunnel, the untunneledDialConfig will be used.
			tunnel := controller.getNextActiveTunnel()

			err := fetcher(
				controller.config,
				tunnel,
				controller.untunneledDialConfig)

			if err == nil {
				lastFetchTime = monotime.Now()
				break retryLoop
			}

			NoticeAlert("failed to fetch %s remote server list: %s", name, err)

			timeout := time.After(retryPeriod)
			select {
			case <-timeout:
			case <-controller.shutdownBroadcast:
				break fetcherLoop
			}
		}
	}

	NoticeInfo("exiting %s remote server list fetcher", name)
}