Update

vendor/tailscale.com/ipn/ipnlocal/captiveportal.go

@@ -0,0 +1,186 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build !ts_omit_captiveportal
+
+package ipnlocal
+
+import (
+	"context"
+	"time"
+
+	"tailscale.com/health"
+	"tailscale.com/net/captivedetection"
+	"tailscale.com/util/clientmetric"
+)
+
+func init() {
+	hookCaptivePortalHealthChange.Set(captivePortalHealthChange)
+	hookCheckCaptivePortalLoop.Set(checkCaptivePortalLoop)
+}
+
+var metricCaptivePortalDetected = clientmetric.NewCounter("captiveportal_detected")
+
+// captivePortalDetectionInterval is the duration to wait in an unhealthy state with connectivity broken
+// before running captive portal detection.
+const captivePortalDetectionInterval = 2 * time.Second
+
+func captivePortalHealthChange(b *LocalBackend, state *health.State) {
+	isConnectivityImpacted := false
+	for _, w := range state.Warnings {
+		// Ignore the captive portal warnable itself.
+		if w.ImpactsConnectivity && w.WarnableCode != captivePortalWarnable.Code {
+			isConnectivityImpacted = true
+			break
+		}
+	}
+
+	// captiveCtx can be changed, and is protected with 'mu'; grab that
+	// before we start our select, below.
+	//
+	// It is guaranteed to be non-nil.
+	b.mu.Lock()
+	ctx := b.captiveCtx
+	b.mu.Unlock()
+
+	// If the context is canceled, we don't need to do anything.
+	if ctx.Err() != nil {
+		return
+	}
+
+	if isConnectivityImpacted {
+		b.logf("health: connectivity impacted; triggering captive portal detection")
+
+		// Ensure that we select on captiveCtx so that we can time out
+		// triggering captive portal detection if the backend is shutdown.
+		select {
+		case b.needsCaptiveDetection <- true:
+		case <-ctx.Done():
+		}
+	} else {
+		// If connectivity is not impacted, we know for sure we're not behind a captive portal,
+		// so drop any warning, and signal that we don't need captive portal detection.
+		b.health.SetHealthy(captivePortalWarnable)
+		select {
+		case b.needsCaptiveDetection <- false:
+		case <-ctx.Done():
+		}
+	}
+}
+
+// captivePortalWarnable is a Warnable which is set to an unhealthy state when a captive portal is detected.
+var captivePortalWarnable = health.Register(&health.Warnable{
+	Code:  "captive-portal-detected",
+	Title: "Captive portal detected",
+	// High severity, because captive portals block all traffic and require user intervention.
+	Severity:            health.SeverityHigh,
+	Text:                health.StaticMessage("This network requires you to log in using your web browser."),
+	ImpactsConnectivity: true,
+})
+
+func checkCaptivePortalLoop(b *LocalBackend, ctx context.Context) {
+	var tmr *time.Timer
+
+	maybeStartTimer := func() {
+		// If there's an existing timer, nothing to do; just continue
+		// waiting for it to expire. Otherwise, create a new timer.
+		if tmr == nil {
+			tmr = time.NewTimer(captivePortalDetectionInterval)
+		}
+	}
+	maybeStopTimer := func() {
+		if tmr == nil {
+			return
+		}
+		if !tmr.Stop() {
+			<-tmr.C
+		}
+		tmr = nil
+	}
+
+	for {
+		if ctx.Err() != nil {
+			maybeStopTimer()
+			return
+		}
+
+		// First, see if we have a signal on our "healthy" channel, which
+		// takes priority over an existing timer. Because a select is
+		// nondeterministic, we explicitly check this channel before
+		// entering the main select below, so that we're guaranteed to
+		// stop the timer before starting captive portal detection.
+		select {
+		case needsCaptiveDetection := <-b.needsCaptiveDetection:
+			if needsCaptiveDetection {
+				maybeStartTimer()
+			} else {
+				maybeStopTimer()
+			}
+		default:
+		}
+
+		var timerChan <-chan time.Time
+		if tmr != nil {
+			timerChan = tmr.C
+		}
+		select {
+		case <-ctx.Done():
+			// All done; stop the timer and then exit.
+			maybeStopTimer()
+			return
+		case <-timerChan:
+			// Kick off captive portal check
+			b.performCaptiveDetection()
+			// nil out timer to force recreation
+			tmr = nil
+		case needsCaptiveDetection := <-b.needsCaptiveDetection:
+			if needsCaptiveDetection {
+				maybeStartTimer()
+			} else {
+				// Healthy; cancel any existing timer
+				maybeStopTimer()
+			}
+		}
+	}
+}
+
+// shouldRunCaptivePortalDetection reports whether captive portal detection
+// should be run. It is enabled by default, but can be disabled via a control
+// knob. It is also only run when the user explicitly wants the backend to be
+// running.
+func (b *LocalBackend) shouldRunCaptivePortalDetection() bool {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	return !b.ControlKnobs().DisableCaptivePortalDetection.Load() && b.pm.prefs.WantRunning()
+}
+
+// performCaptiveDetection checks if captive portal detection is enabled via controlknob. If so, it runs
+// the detection and updates the Warnable accordingly.
+func (b *LocalBackend) performCaptiveDetection() {
+	if !b.shouldRunCaptivePortalDetection() {
+		return
+	}
+
+	d := captivedetection.NewDetector(b.logf)
+	b.mu.Lock() // for b.hostinfo
+	cn := b.currentNode()
+	dm := cn.DERPMap()
+	preferredDERP := 0
+	if b.hostinfo != nil {
+		if b.hostinfo.NetInfo != nil {
+			preferredDERP = b.hostinfo.NetInfo.PreferredDERP
+		}
+	}
+	ctx := b.ctx
+	netMon := b.NetMon()
+	b.mu.Unlock()
+	found := d.Detect(ctx, netMon, dm, preferredDERP)
+	if found {
+		if !b.health.IsUnhealthy(captivePortalWarnable) {
+			metricCaptivePortalDetected.Add(1)
+		}
+		b.health.SetUnhealthy(captivePortalWarnable, health.Args{})
+	} else {
+		b.health.SetHealthy(captivePortalWarnable)
+	}
+}