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wgengine/router: provide explicit hook to signal Android when VPN needs to be reconfigured

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This allows clients to avoid establishing their VPN multiple times when
both routes and DNS are changing in rapid succession.

Updates tailscale/corp#18928

Signed-off-by: Percy Wegmann <percy@tailscale.com>
This commit is contained in:
Percy Wegmann 2024-04-04 09:32:17 -05:00 committed by Percy Wegmann
parent 1a38d2a3b4
commit 853e3e29a0
1 changed files with 25 additions and 2 deletions
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25
wgengine/userspace.go
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@ -126,6 +126,7 @@ type userspaceEngine struct {
sentActivityAt map[netip.Addr]*mono.Time // value is accessed atomically
destIPActivityFuncs map[netip.Addr]func()
lastStatusPollTime mono.Time // last time we polled the engine status
reconfigureVPN func() error // or nil
mu sync.Mutex // guards following; see lock order comment below
netMap *netmap.NetworkMap // or nil
@ -175,6 +176,13 @@ type Config struct {
// If nil, a fake OSConfigurator that does nothing is used.
DNS dns.OSConfigurator
// ReconfigureVPN provides an optional hook for platforms like Android to
// know when it's time to reconfigure their VPN implementation. Such
// platforms can only set their entire VPN configuration (routes, DNS, etc)
// at all once and can't make piecemeal incremental changes, so this
// provides a hook to "flush" a batch of Router and/or DNS changes.
ReconfigureVPN func() error
// NetMon optionally provides an existing network monitor to re-use.
// If nil, a new network monitor is created.
NetMon *netmon.Monitor
@ -283,6 +291,7 @@ func NewUserspaceEngine(logf logger.Logf, conf Config) (_ Engine, reterr error)
confListenPort: conf.ListenPort,
birdClient: conf.BIRDClient,
controlKnobs: conf.ControlKnobs,
reconfigureVPN: conf.ReconfigureVPN,
}
if e.birdClient != nil {
@ -956,6 +965,9 @@ func (e *userspaceEngine) Reconfig(cfg *wgcfg.Config, routerCfg *router.Config,
if err != nil {
return err
}
if err := e.reconfigureVPNIfNecessary(); err != nil {
return err
}
}
// Shutdown the network logger.
@ -1161,10 +1173,12 @@ func (e *userspaceEngine) linkChange(delta *netmon.ChangeDelta) {
}
}
// Hacky workaround for Linux DNS issue 2458: on
// Hacky workaround for Unix DNS issue 2458: on
// suspend/resume or whenever NetworkManager is started, it
// nukes all systemd-resolved configs. So reapply our DNS
// config on major link change.
// TODO: explain why this is ncessary not just on Linux but also android
// and Apple platforms.
if changed {
switch runtime.GOOS {
case "linux", "android", "ios", "darwin":
@ -1174,6 +1188,8 @@ func (e *userspaceEngine) linkChange(delta *netmon.ChangeDelta) {
if dnsCfg != nil {
if err := e.dns.Set(*dnsCfg); err != nil {
e.logf("wgengine: error setting DNS config after major link change: %v", err)
} else if err := e.reconfigureVPNIfNecessary(); err != nil {
e.logf("wgengine: error reconfiguring VPN after major link change: %v", err)
} else {
e.logf("wgengine: set DNS config again after major link change")
}
@ -1528,3 +1544,10 @@ func (e *userspaceEngine) InstallCaptureHook(cb capture.Callback) {
e.tundev.InstallCaptureHook(cb)
e.magicConn.InstallCaptureHook(cb)
}
func (e *userspaceEngine) reconfigureVPNIfNecessary() error {
if e.reconfigureVPN == nil {
return nil
}
return e.reconfigureVPN()
}