Do Duplicate Address Detection on permanent IPv6 addresses.

This change adds support for Duplicate Address Detection on IPv6 addresses
as defined by RFC 4862 section 5.4.

Note, this change will not break existing uses of netstack as the default
configuration for the stack options is set in such a way that DAD will not be
performed. See `stack.Options` and `stack.NDPConfigurations` for more details.

Tests: Tests to make sure that the DAD process properly resolves or fails.
That is, tests make sure that DAD resolves only if:
  - No other node is performing DAD for the same address
  - No other node owns the same address
PiperOrigin-RevId: 275189471

1 files changed, 164 insertions, 0 deletions

diff --git a/pkg/tcpip/header/ndp_test.go b/pkg/tcpip/header/ndp_test.go
new file mode 100644
index 000000000..a431a6e61
--- /dev/null
+++ b/pkg/tcpip/header/ndp_test.go
@@ -0,0 +1,164 @@
+// Copyright 2019 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 header
+
+import (
+	"bytes"
+	"testing"
+
+	"gvisor.dev/gvisor/pkg/tcpip"
+)
+
+// TestNDPNeighborSolicit tests the functions of NDPNeighborSolicit.
+func TestNDPNeighborSolicit(t *testing.T) {
+	b := []byte{
+		0, 0, 0, 0,
+		1, 2, 3, 4,
+		5, 6, 7, 8,
+		9, 10, 11, 12,
+		13, 14, 15, 16,
+	}
+
+	// Test getting the Target Address.
+	ns := NDPNeighborSolicit(b)
+	addr := tcpip.Address("\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f\x10")
+	if got := ns.TargetAddress(); got != addr {
+		t.Fatalf("got ns.TargetAddress = %s, want %s", got, addr)
+	}
+
+	// Test updating the Target Address.
+	addr2 := tcpip.Address("\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f\x11")
+	ns.SetTargetAddress(addr2)
+	if got := ns.TargetAddress(); got != addr2 {
+		t.Fatalf("got ns.TargetAddress = %s, want %s", got, addr2)
+	}
+	// Make sure the address got updated in the backing buffer.
+	if got := tcpip.Address(b[ndpNSTargetAddessOffset:][:IPv6AddressSize]); got != addr2 {
+		t.Fatalf("got targetaddress buffer = %s, want %s", got, addr2)
+	}
+}
+
+// TestNDPNeighborAdvert tests the functions of NDPNeighborAdvert.
+func TestNDPNeighborAdvert(t *testing.T) {
+	b := []byte{
+		160, 0, 0, 0,
+		1, 2, 3, 4,
+		5, 6, 7, 8,
+		9, 10, 11, 12,
+		13, 14, 15, 16,
+	}
+
+	// Test getting the Target Address.
+	na := NDPNeighborAdvert(b)
+	addr := tcpip.Address("\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f\x10")
+	if got := na.TargetAddress(); got != addr {
+		t.Fatalf("got TargetAddress = %s, want %s", got, addr)
+	}
+
+	// Test getting the Router Flag.
+	if got := na.RouterFlag(); !got {
+		t.Fatalf("got RouterFlag = false, want = true")
+	}
+
+	// Test getting the Solicited Flag.
+	if got := na.SolicitedFlag(); got {
+		t.Fatalf("got SolicitedFlag = true, want = false")
+	}
+
+	// Test getting the Override Flag.
+	if got := na.OverrideFlag(); !got {
+		t.Fatalf("got OverrideFlag = false, want = true")
+	}
+
+	// Test updating the Target Address.
+	addr2 := tcpip.Address("\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f\x11")
+	na.SetTargetAddress(addr2)
+	if got := na.TargetAddress(); got != addr2 {
+		t.Fatalf("got TargetAddress = %s, want %s", got, addr2)
+	}
+	// Make sure the address got updated in the backing buffer.
+	if got := tcpip.Address(b[ndpNATargetAddressOffset:][:IPv6AddressSize]); got != addr2 {
+		t.Fatalf("got targetaddress buffer = %s, want %s", got, addr2)
+	}
+
+	// Test updating the Router Flag.
+	na.SetRouterFlag(false)
+	if got := na.RouterFlag(); got {
+		t.Fatalf("got RouterFlag = true, want = false")
+	}
+
+	// Test updating the Solicited Flag.
+	na.SetSolicitedFlag(true)
+	if got := na.SolicitedFlag(); !got {
+		t.Fatalf("got SolicitedFlag = false, want = true")
+	}
+
+	// Test updating the Override Flag.
+	na.SetOverrideFlag(false)
+	if got := na.OverrideFlag(); got {
+		t.Fatalf("got OverrideFlag = true, want = false")
+	}
+
+	// Make sure flags got updated in the backing buffer.
+	if got := b[ndpNAFlagsOffset]; got != 64 {
+		t.Fatalf("got flags byte = %d, want = 64")
+	}
+}
+
+// TestNDPTargetLinkLayerAddressOptionSerialize tests serializing a
+// NDPTargetLinkLayerAddressOption.
+func TestNDPTargetLinkLayerAddressOptionSerialize(t *testing.T) {
+	tests := []struct {
+		name        string
+		buf         []byte
+		expectedBuf []byte
+		addr        tcpip.LinkAddress
+	}{
+		{
+			"Ethernet",
+			make([]byte, 8),
+			[]byte{2, 1, 1, 2, 3, 4, 5, 6},
+			"\x01\x02\x03\x04\x05\x06",
+		},
+		{
+			"Padding",
+			[]byte{1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},
+			[]byte{2, 2, 1, 2, 3, 4, 5, 6, 7, 8, 0, 0, 0, 0, 0, 0},
+			"\x01\x02\x03\x04\x05\x06\x07\x08",
+		},
+		{
+			"Empty",
+			[]byte{},
+			[]byte{},
+			"",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			opts := NDPOptions(test.buf)
+			serializer := NDPOptionsSerializer{
+				NDPTargetLinkLayerAddressOption(test.addr),
+			}
+			if got, want := int(serializer.Length()), len(test.expectedBuf); got != want {
+				t.Fatalf("got Length = %d, want = %d", got, want)
+			}
+			opts.Serialize(serializer)
+			if !bytes.Equal(test.buf, test.expectedBuf) {
+				t.Fatalf("got b = %d, want = %d", test.buf, test.expectedBuf)
+			}
+		})
+	}
+}