commetn test

reassembly/tcpassembly_test.go

@@ -1199,13 +1199,20 @@ func TestKeepWithFlush(t *testing.T) {
 	})
 }
 
-func TestKeepWithManualFlush(t *testing.T) {
+func TestKeepWithOutOfOrderPacketAndManualFlush(t *testing.T) {
 	makePayload := func(length int) []byte {
 		data := make([]byte, length)
 		rand.Read(data)
 		return data
 	}
 
+	// The first packet is received out of order. It contains `pageBytes + 1`
+	// number of bytes, so it spans 2 pages.
+	// The second packet carries a single byte before the first packet, and we
+	// request to keep `pageBytes` bytes. Then trigger a flush.
+	// Prior to a fix, this would result in an slice bounds out of range panic
+	// when the code tries to incorrectly skip the leading bytes on the second
+	// page of the first packet.
 	testKeep(t, []testKeepSequence{
 		{
 			tcp: layers.TCP{
@@ -1223,13 +1230,11 @@ func TestKeepWithManualFlush(t *testing.T) {
 				Seq:       1000,
 				BaseLayer: layers.BaseLayer{Payload: []byte{1}},
 			},
-			keep:  3,
+			keep:  pageBytes,
 			want:  []byte{},
 			flush: true,
 		},
 	})
-
-	t.Errorf("fake error")
 }
 
 /*