Restart the relay guard settle timer on every network transition

shared/relay/client/guard.go

@@ -223,17 +223,24 @@ func (g *Guard) waitForNetwork(ctx context.Context) bool {
 			case <-settle.C:
 				return true
 			case <-changedCh:
-				continue
+			case <-ctx.Done():
+				return false
+			}
+		} else {
+			select {
+			case <-budget.C:
+				return true
+			case <-changedCh:
 			case <-ctx.Done():
 				return false
 			}
 		}
-		select {
-		case <-budget.C:
-			return true
-		case <-changedCh:
-		case <-ctx.Done():
-			return false
+		if !settle.Stop() {
+			select {
+			case <-settle.C:
+			default:
+			}
 		}
+		settle.Reset(settleWindow)
 	}
 }

shared/relay/client/guard_test.go

@@ -0,0 +1,30 @@
+package client
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+
+	"github.com/netbirdio/netbird/client/netstate"
+)
+
+func TestWaitForNetworkSettlesAfterOutage(t *testing.T) {
+	ns := netstate.New()
+	ns.Set(false)
+	g := NewGuard(nil, 0, ns)
+
+	const outage = 2 * verdictSettleWindow
+	go func() {
+		time.Sleep(outage)
+		ns.Set(true)
+	}()
+
+	start := time.Now()
+	ok := g.waitForNetwork(context.Background())
+	elapsed := time.Since(start)
+
+	assert.True(t, ok, "recovered network must let the quick reconnect proceed")
+	assert.GreaterOrEqual(t, elapsed, outage+verdictSettleWindow, "reconnect must wait a full settle window after the network returns")
+}