TUN inbound: Merge the outbound guard's check and recheck

Since the TUN starts with forwarding on the outbound interface too, check
is only called through recheck, so they are one function now.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

proxy/tun/tun_windows.go

@@ -307,12 +307,12 @@ startOver:
 		if route6 {
 			t.guard.families = append(t.guard.families, windows.AF_INET6)
 		}
-		t.guard.recheck()
+		t.guard.check()
 		// Only a registered callback goes into the fields: a nil pointer in
 		// them would not compare equal to nil in Close.
 		cbr, err := winipcfg.RegisterRouteChangeCallback(func(notificationType winipcfg.MibNotificationType, route *winipcfg.MibIPforwardRow2) {
 			updater.Update()
-			t.guard.recheck()
+			t.guard.check()
 		})
 		if err != nil {
 			return err
@@ -320,7 +320,7 @@ startOver:
 		t.cbr = cbr
 		cbi, err := winipcfg.RegisterInterfaceChangeCallback(func(notificationType winipcfg.MibNotificationType, iface *winipcfg.MibIPInterfaceRow) {
 			updater.Update()
-			t.guard.recheck()
+			t.guard.check()
 		})
 		if err != nil {
 			return err

proxy/tun/tun_windows_outbound.go

@@ -25,20 +25,20 @@ import (
 // Internet Connection Sharing need, so it is only reported.
 type outboundGuard struct {
 	sync.Mutex
-	families  []winipcfg.AddressFamily
-	luid      winipcfg.LUID            // of the interface last checked
-	turnedOff []winipcfg.AddressFamily // where weak host send was turned off on it
-	reported  string                   // the forwarding problem last seen
-	stopped   bool
+	families   []winipcfg.AddressFamily
+	luid       winipcfg.LUID            // of the interface last checked
+	turnedOff  []winipcfg.AddressFamily // where weak host send was turned off on it
+	forwarding bool                     // whether forwarding was on there
+	stopped    bool
 }
 
-// check turns weak host send off on the bound interface, and returns what is
-// wrong if forwarding is on there.
-func (g *outboundGuard) check() string {
+// check turns weak host send off on the bound interface, and warns when
+// forwarding comes on there, but not again while it stays on.
+func (g *outboundGuard) check() {
 	g.Lock()
 	defer g.Unlock()
 	if g.stopped {
-		return ""
+		return
 	}
 	var luid winipcfg.LUID
 	var name string
@@ -51,7 +51,8 @@ func (g *outboundGuard) check() string {
 		g.luid = luid
 	}
 	if luid == 0 {
-		return ""
+		g.forwarding = false
+		return
 	}
 	var forwarding []string
 	for _, family := range g.families {
@@ -74,22 +75,10 @@ func (g *outboundGuard) check() string {
 			errors.LogInfo(context.Background(), "[tun] weak host send turned off for ", familyName(family), " on ", name, " while the TUN runs, as Windows would ignore autoOutboundsInterface")
 		}
 	}
-	if len(forwarding) > 0 {
-		return "forwarding is on for " + strings.Join(forwarding, " and ") + " on " + name + " (Mobile Hotspot and Internet Connection Sharing turn it on), so Windows ignores autoOutboundsInterface there, and Xray's own connections go into the TUN and stall: turn the hotspot off, or have it share the TUN instead of " + name
-	}
-	return ""
-}
-
-// recheck runs check, and warns about forwarding when it comes up. (Windows
-// may turn forwarding on and off a few times meanwhile.)
-func (g *outboundGuard) recheck() {
-	problem := g.check()
-	g.Lock()
-	cameUp := problem != "" && g.reported == ""
-	g.reported = problem
-	g.Unlock()
-	if cameUp {
-		errors.LogWarning(context.Background(), "[tun] ", problem)
+	wasOn := g.forwarding
+	g.forwarding = len(forwarding) > 0
+	if g.forwarding && !wasOn {
+		errors.LogWarning(context.Background(), "[tun] forwarding is on for ", strings.Join(forwarding, " and "), " on ", name, " (Mobile Hotspot and Internet Connection Sharing turn it on), so Windows ignores autoOutboundsInterface there, and Xray's own connections go into the TUN and stall: turn the hotspot off, or have it share the TUN instead of ", name)
 	}
 }