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monitor_windows.go
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monitor_windows.go
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// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package monitor
import (
"context"
"errors"
"strings"
"sync"
"time"
"golang.zx2c4.com/wireguard/windows/tunnel/winipcfg"
"tailscale.com/net/tsaddr"
"tailscale.com/types/logger"
)
var (
errClosed = errors.New("closed")
)
type eventMessage struct {
eventType string
}
func (eventMessage) ignore() bool { return false }
type winMon struct {
logf logger.Logf
ctx context.Context
cancel context.CancelFunc
messagec chan eventMessage
addressChangeCallback *winipcfg.UnicastAddressChangeCallback
routeChangeCallback *winipcfg.RouteChangeCallback
mu sync.Mutex
lastLog time.Time // time we last logged about any windows change event
// noDeadlockTicker exists just to have something scheduled as
// far as the Go runtime is concerned. Otherwise "tailscaled
// debug --monitor" thinks it's deadlocked with nothing to do,
// as Go's runtime doesn't know about callbacks registered with
// Windows.
noDeadlockTicker *time.Ticker
}
func newOSMon(logf logger.Logf, _ *Mon) (osMon, error) {
m := &winMon{
logf: logf,
messagec: make(chan eventMessage, 1),
noDeadlockTicker: time.NewTicker(5000 * time.Hour), // arbitrary
}
var err error
m.addressChangeCallback, err = winipcfg.RegisterUnicastAddressChangeCallback(m.unicastAddressChanged)
if err != nil {
m.logf("winipcfg.RegisterUnicastAddressChangeCallback error: %v", err)
return nil, err
}
m.routeChangeCallback, err = winipcfg.RegisterRouteChangeCallback(m.routeChanged)
if err != nil {
m.addressChangeCallback.Unregister()
m.logf("winipcfg.RegisterRouteChangeCallback error: %v", err)
return nil, err
}
m.ctx, m.cancel = context.WithCancel(context.Background())
return m, nil
}
func (m *winMon) IsInterestingInterface(iface string) bool { return true }
func (m *winMon) Close() (ret error) {
m.cancel()
m.noDeadlockTicker.Stop()
if m.addressChangeCallback != nil {
if err := m.addressChangeCallback.Unregister(); err != nil {
m.logf("addressChangeCallback.Unregister error: %v", err)
ret = err
} else {
m.addressChangeCallback = nil
}
}
if m.routeChangeCallback != nil {
if err := m.routeChangeCallback.Unregister(); err != nil {
m.logf("routeChangeCallback.Unregister error: %v", err)
ret = err
} else {
m.routeChangeCallback = nil
}
}
return
}
func (m *winMon) Receive() (message, error) {
if m.ctx.Err() != nil {
m.logf("Receive call on closed monitor")
return nil, errClosed
}
t0 := time.Now()
select {
case msg := <-m.messagec:
now := time.Now()
m.mu.Lock()
sinceLast := now.Sub(m.lastLog)
m.lastLog = now
m.mu.Unlock()
// If it's either been awhile since we last logged
// anything, or if this some route/addr that's not
// about a Tailscale IP ("ts" prefix), then log. This
// is mainly limited to suppress the flood about our own
// route updates after connecting to a large tailnet
// and all the IPv4 /32 routes.
if sinceLast > 5*time.Second || !strings.HasPrefix(msg.eventType, "ts") {
m.logf("got windows change event after %v: evt=%s", time.Since(t0).Round(time.Millisecond), msg.eventType)
}
return msg, nil
case <-m.ctx.Done():
return nil, errClosed
}
}
// unicastAddressChanged is the callback we register with Windows to call when unicast address changes.
func (m *winMon) unicastAddressChanged(_ winipcfg.MibNotificationType, row *winipcfg.MibUnicastIPAddressRow) {
what := "addr"
if ip := row.Address.Addr(); ip.IsValid() && tsaddr.IsTailscaleIP(ip.Unmap()) {
what = "tsaddr"
}
// start a goroutine to finish our work, to return to Windows out of this callback
go m.somethingChanged(what)
}
// routeChanged is the callback we register with Windows to call when route changes.
func (m *winMon) routeChanged(_ winipcfg.MibNotificationType, row *winipcfg.MibIPforwardRow2) {
what := "route"
ip := row.DestinationPrefix.Prefix().Addr().Unmap()
if ip.IsValid() && tsaddr.IsTailscaleIP(ip) {
what = "tsroute"
}
// start a goroutine to finish our work, to return to Windows out of this callback
go m.somethingChanged(what)
}
// somethingChanged gets called from OS callbacks whenever address or route changes.
func (m *winMon) somethingChanged(evt string) {
select {
case <-m.ctx.Done():
return
case m.messagec <- eventMessage{eventType: evt}:
return
}
}