Fix memory leak

internal/turbotunnel/remotemap_leak_test.go

@@ -0,0 +1,51 @@
+package turbotunnel
+
+import (
+	"runtime"
+	"testing"
+	"time"
+)
+
+// TestQueuePacketConnCloseStopsGoroutine is the regression test for the local
+// fork's reason to exist: upstream's RemoteMap expiry goroutine runs forever,
+// so creating and discarding many QueuePacketConns (as DNSTT restart does)
+// leaks one goroutine each. After Close(), the count must return to baseline.
+func TestQueuePacketConnCloseStopsGoroutine(t *testing.T) {
+	// Let any goroutines from earlier settle.
+	settle := func() {
+		for i := 0; i < 50; i++ {
+			runtime.GC()
+			time.Sleep(2 * time.Millisecond)
+		}
+	}
+	settle()
+	base := runtime.NumGoroutine()
+
+	const n = 200
+	for i := 0; i < n; i++ {
+		// Short timeout so the goroutine is definitely started (timeout > 0).
+		c := NewQueuePacketConn(DummyAddr{}, 50*time.Millisecond)
+		if err := c.Close(); err != nil {
+			t.Fatalf("Close returned error: %v", err)
+		}
+	}
+	settle()
+
+	got := runtime.NumGoroutine()
+	// Allow a small slack for scheduler/runtime goroutines; the key point is we
+	// are nowhere near base+n (which is what the upstream leak would produce).
+	if got > base+20 {
+		t.Fatalf("goroutine leak: baseline=%d after %d create/close cycles=%d (want <= baseline+20)", base, n, got)
+	}
+}
+
+// TestRemoteMapCloseIdempotent verifies Close can be called repeatedly.
+func TestRemoteMapCloseIdempotent(t *testing.T) {
+	m := NewRemoteMap(10 * time.Millisecond)
+	if err := m.Close(); err != nil {
+		t.Fatalf("first Close: %v", err)
+	}
+	if err := m.Close(); err != nil {
+		t.Fatalf("second Close: %v", err)
+	}
+}