Fix view.ToVectorisedView().

view.ToVectorisedView() now just returns an empty vectorised
view if the view is of zero length. Earlier it would return
a VectorisedView of zero length but with 1 empty view. This
has been a source of bugs as lower layers don't expect
zero length views in VectorisedViews.

VectorisedView.AppendView() now is a no-op if the view being
appended is of zero length.

Fixes #2658

PiperOrigin-RevId: 310942269

2 files changed, 42 insertions, 0 deletions

diff --git a/pkg/tcpip/buffer/view.go b/pkg/tcpip/buffer/view.go
index f01217c91..9a3c5d6c3 100644
--- a/pkg/tcpip/buffer/view.go
+++ b/pkg/tcpip/buffer/view.go
@@ -59,6 +59,9 @@ func (v *View) Reader() bytes.Reader {
 
 // ToVectorisedView returns a VectorisedView containing the receiver.
 func (v View) ToVectorisedView() VectorisedView {
+	if len(v) == 0 {
+		return VectorisedView{}
+	}
 	return NewVectorisedView(len(v), []View{v})
 }
 
@@ -229,6 +232,9 @@ func (vv *VectorisedView) Append(vv2 VectorisedView) {
 
 // AppendView appends the given view into this vectorised view.
 func (vv *VectorisedView) AppendView(v View) {
+	if len(v) == 0 {
+		return
+	}
 	vv.views = append(vv.views, v)
 	vv.size += len(v)
 }
diff --git a/pkg/tcpip/buffer/view_test.go b/pkg/tcpip/buffer/view_test.go
index c56795c7b..726e54de9 100644
--- a/pkg/tcpip/buffer/view_test.go
+++ b/pkg/tcpip/buffer/view_test.go
@@ -483,3 +483,39 @@ func TestPullUp(t *testing.T) {
 		}
 	}
 }
+
+func TestToVectorisedView(t *testing.T) {
+	testCases := []struct {
+		in   View
+		want VectorisedView
+	}{
+		{nil, VectorisedView{}},
+		{View{}, VectorisedView{}},
+		{View{'a'}, VectorisedView{size: 1, views: []View{{'a'}}}},
+	}
+	for _, tc := range testCases {
+		if got, want := tc.in.ToVectorisedView(), tc.want; !reflect.DeepEqual(got, want) {
+			t.Errorf("(%v).ToVectorisedView failed got: %+v, want: %+v", tc.in, got, want)
+		}
+	}
+}
+
+func TestAppendView(t *testing.T) {
+	testCases := []struct {
+		vv   VectorisedView
+		in   View
+		want VectorisedView
+	}{
+		{VectorisedView{}, nil, VectorisedView{}},
+		{VectorisedView{}, View{}, VectorisedView{}},
+		{VectorisedView{[]View{{'a', 'b', 'c', 'd'}}, 4}, nil, VectorisedView{[]View{{'a', 'b', 'c', 'd'}}, 4}},
+		{VectorisedView{[]View{{'a', 'b', 'c', 'd'}}, 4}, View{}, VectorisedView{[]View{{'a', 'b', 'c', 'd'}}, 4}},
+		{VectorisedView{[]View{{'a', 'b', 'c', 'd'}}, 4}, View{'e'}, VectorisedView{[]View{{'a', 'b', 'c', 'd'}, {'e'}}, 5}},
+	}
+	for _, tc := range testCases {
+		tc.vv.AppendView(tc.in)
+		if got, want := tc.vv, tc.want; !reflect.DeepEqual(got, want) {
+			t.Errorf("(%v).ToVectorisedView failed got: %+v, want: %+v", tc.in, got, want)
+		}
+	}
+}