Implement Stringer for Layer

Tested:
  Sample output for printing 3 different Layer structs:

  &testbench.Ether{SrcAddr:02:42:c4:77:5d:14 DstAddr:02:42:c4:77:5d:0a}
  &testbench.IPv4{SrcAddr:196.119.93.20 DstAddr:224.0.0.1}
  &testbench.UDP{SrcPort:0xc00033b260 DstPort:0xc00033b280}

  Sample output for printing a Layers struct (word-wrapped):
  [&testbench.Ether{SrcAddr:02:42:c4:77:5d:14 DstAddr:02:42:c4:77:5d:0a}
   &testbench.IPv4{SrcAddr:196.119.93.20 DstAddr:224.0.0.1}
   &testbench.UDP{SrcPort:0xc00033b260 DstPort:0xc00033b280}
   &testbench.Payload{Bytes:[104 101 108 108 111 32 119 111 114 108 100]}]

PiperOrigin-RevId: 305014376

1 files changed, 49 insertions, 0 deletions

diff --git a/test/packetimpact/testbench/layers_test.go b/test/packetimpact/testbench/layers_test.go
new file mode 100644
index 000000000..b39839625
--- /dev/null
+++ b/test/packetimpact/testbench/layers_test.go
@@ -0,0 +1,49 @@
+// Copyright 2020 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package testbench
+
+import "testing"
+
+func TestLayerMatch(t *testing.T) {
+	var nilPayload *Payload
+	noPayload := &Payload{}
+	emptyPayload := &Payload{Bytes: []byte{}}
+	fullPayload := &Payload{Bytes: []byte{1, 2, 3}}
+	emptyTCP := &TCP{SrcPort: Uint16(1234), LayerBase: LayerBase{nextLayer: emptyPayload}}
+	fullTCP := &TCP{SrcPort: Uint16(1234), LayerBase: LayerBase{nextLayer: fullPayload}}
+	for _, tt := range []struct {
+		a, b Layer
+		want bool
+	}{
+		{nilPayload, nilPayload, true},
+		{nilPayload, noPayload, true},
+		{nilPayload, emptyPayload, true},
+		{nilPayload, fullPayload, true},
+		{noPayload, noPayload, true},
+		{noPayload, emptyPayload, true},
+		{noPayload, fullPayload, true},
+		{emptyPayload, emptyPayload, true},
+		{emptyPayload, fullPayload, false},
+		{fullPayload, fullPayload, true},
+		{emptyTCP, fullTCP, true},
+	} {
+		if got := tt.a.match(tt.b); got != tt.want {
+			t.Errorf("%s.match(%s) = %t, want %t", tt.a, tt.b, got, tt.want)
+		}
+		if got := tt.b.match(tt.a); got != tt.want {
+			t.Errorf("%s.match(%s) = %t, want %t", tt.b, tt.a, got, tt.want)
+		}
+	}
+}