// 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")
}
// 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)
}