Benchmark for QueuePacketConn.QueueIncoming.

	$ go test -bench=BenchmarkQueueIncoming -benchtime=2s -benchmem
	BenchmarkQueueIncoming-4         7001494               342.4 ns/op          1024 B/op          2 allocs/op

common/turbotunnel/queuepacketconn_test.go

+package turbotunnel
+
+import (
+	"testing"
+	"time"
+)
+
+type emptyAddr struct{}
+
+func (_ emptyAddr) Network() string { return "empty" }
+func (_ emptyAddr) String() string  { return "empty" }
+
+// Run with -benchmem to see memory allocations.
+func BenchmarkQueueIncoming(b *testing.B) {
+	conn := NewQueuePacketConn(emptyAddr{}, 1*time.Hour)
+	defer conn.Close()
+
+	b.ResetTimer()
+	s := 500
+	for i := 0; i < b.N; i++ {
+		// Use a variable for the length to stop the compiler from
+		// optimizing out the allocation.
+		p := make([]byte, s)
+		conn.QueueIncoming(p, emptyAddr{})
+	}
+	b.StopTimer()
+}