Update link address for targets of Neighbor Adverts

Get the link address for the target of an NDP Neighbor Advertisement
from the NDP Target Link Layer Address option.

Tests:
- ipv6.TestNeighorAdvertisementWithTargetLinkLayerOption
- ipv6.TestNeighorAdvertisementWithInvalidTargetLinkLayerOption
PiperOrigin-RevId: 293632609

3 files changed, 346 insertions, 162 deletions

diff --git a/pkg/tcpip/network/ipv6/icmp.go b/pkg/tcpip/network/ipv6/icmp.go
index 60817d36d..45dc757c7 100644
--- a/pkg/tcpip/network/ipv6/icmp.go
+++ b/pkg/tcpip/network/ipv6/icmp.go
@@ -15,6 +15,8 @@
 package ipv6
 
 import (
+	"log"
+
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
@@ -194,7 +196,11 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, pkt tcpip.P
 		// TODO(b/148429853): Properly process the NS message and do Neighbor
 		// Unreachability Detection.
 		for {
-			opt, done, _ := it.Next()
+			opt, done, err := it.Next()
+			if err != nil {
+				// This should never happen as Iter(true) above did not return an error.
+				log.Fatalf("unexpected error when iterating over NDP options: %s", err)
+			}
 			if done {
 				break
 			}
@@ -253,21 +259,25 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, pkt tcpip.P
 		}
 
 		na := header.NDPNeighborAdvert(h.NDPPayload())
+		it, err := na.Options().Iter(true)
+		if err != nil {
+			// If we have a malformed NDP NA option, drop the packet.
+			received.Invalid.Increment()
+			return
+		}
+
 		targetAddr := na.TargetAddress()
 		stack := r.Stack()
 		rxNICID := r.NICID()
 
-		isTentative, err := stack.IsAddrTentative(rxNICID, targetAddr)
-		if err != nil {
+		if isTentative, err := stack.IsAddrTentative(rxNICID, targetAddr); err != nil {
 			// We will only get an error if rxNICID is unrecognized,
 			// which should not happen. For now short-circuit this
 			// packet.
 			//
 			// TODO(b/141002840): Handle this better?
 			return
-		}
-
-		if isTentative {
+		} else if isTentative {
 			// We just got an NA from a node that owns an address we
 			// are performing DAD on, implying the address is not
 			// unique. In this case we let the stack know so it can
@@ -283,13 +293,29 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, pkt tcpip.P
 		// scenario is beyond the scope of RFC 4862. As such, we simply
 		// ignore such a scenario for now and proceed as normal.
 		//
+		// If the NA message has the target link layer option, update the link
+		// address cache with the link address for the target of the message.
+		//
 		// TODO(b/143147598): Handle the scenario described above. Also
 		// inform the netstack integration that a duplicate address was
 		// detected outside of DAD.
+		//
+		// TODO(b/148429853): Properly process the NA message and do Neighbor
+		// Unreachability Detection.
+		for {
+			opt, done, err := it.Next()
+			if err != nil {
+				// This should never happen as Iter(true) above did not return an error.
+				log.Fatalf("unexpected error when iterating over NDP options: %s", err)
+			}
+			if done {
+				break
+			}
 
-		e.linkAddrCache.AddLinkAddress(e.nicID, targetAddr, r.RemoteLinkAddress)
-		if targetAddr != r.RemoteAddress {
-			e.linkAddrCache.AddLinkAddress(e.nicID, r.RemoteAddress, r.RemoteLinkAddress)
+			switch opt := opt.(type) {
+			case header.NDPTargetLinkLayerAddressOption:
+				e.linkAddrCache.AddLinkAddress(e.nicID, targetAddr, opt.EthernetAddress())
+			}
 		}
 
 	case header.ICMPv6EchoRequest:
diff --git a/pkg/tcpip/network/ipv6/icmp_test.go b/pkg/tcpip/network/ipv6/icmp_test.go
index d0e930e20..50c4b6474 100644
--- a/pkg/tcpip/network/ipv6/icmp_test.go
+++ b/pkg/tcpip/network/ipv6/icmp_test.go
@@ -121,21 +121,60 @@ func TestICMPCounts(t *testing.T) {
 	}
 	defer r.Release()
 
+	var tllData [header.NDPLinkLayerAddressSize]byte
+	header.NDPOptions(tllData[:]).Serialize(header.NDPOptionsSerializer{
+		header.NDPTargetLinkLayerAddressOption(linkAddr1),
+	})
+
 	types := []struct {
-		typ  header.ICMPv6Type
-		size int
+		typ       header.ICMPv6Type
+		size      int
+		extraData []byte
 	}{
-		{header.ICMPv6DstUnreachable, header.ICMPv6DstUnreachableMinimumSize},
-		{header.ICMPv6PacketTooBig, header.ICMPv6PacketTooBigMinimumSize},
-		{header.ICMPv6TimeExceeded, header.ICMPv6MinimumSize},
-		{header.ICMPv6ParamProblem, header.ICMPv6MinimumSize},
-		{header.ICMPv6EchoRequest, header.ICMPv6EchoMinimumSize},
-		{header.ICMPv6EchoReply, header.ICMPv6EchoMinimumSize},
-		{header.ICMPv6RouterSolicit, header.ICMPv6MinimumSize},
-		{header.ICMPv6RouterAdvert, header.ICMPv6HeaderSize + header.NDPRAMinimumSize},
-		{header.ICMPv6NeighborSolicit, header.ICMPv6NeighborSolicitMinimumSize},
-		{header.ICMPv6NeighborAdvert, header.ICMPv6NeighborAdvertSize},
-		{header.ICMPv6RedirectMsg, header.ICMPv6MinimumSize},
+		{
+			typ:  header.ICMPv6DstUnreachable,
+			size: header.ICMPv6DstUnreachableMinimumSize,
+		},
+		{
+			typ:  header.ICMPv6PacketTooBig,
+			size: header.ICMPv6PacketTooBigMinimumSize,
+		},
+		{
+			typ:  header.ICMPv6TimeExceeded,
+			size: header.ICMPv6MinimumSize,
+		},
+		{
+			typ:  header.ICMPv6ParamProblem,
+			size: header.ICMPv6MinimumSize,
+		},
+		{
+			typ:  header.ICMPv6EchoRequest,
+			size: header.ICMPv6EchoMinimumSize,
+		},
+		{
+			typ:  header.ICMPv6EchoReply,
+			size: header.ICMPv6EchoMinimumSize,
+		},
+		{
+			typ:  header.ICMPv6RouterSolicit,
+			size: header.ICMPv6MinimumSize,
+		},
+		{
+			typ:  header.ICMPv6RouterAdvert,
+			size: header.ICMPv6HeaderSize + header.NDPRAMinimumSize,
+		},
+		{
+			typ:  header.ICMPv6NeighborSolicit,
+			size: header.ICMPv6NeighborSolicitMinimumSize},
+		{
+			typ:       header.ICMPv6NeighborAdvert,
+			size:      header.ICMPv6NeighborAdvertMinimumSize,
+			extraData: tllData[:],
+		},
+		{
+			typ:  header.ICMPv6RedirectMsg,
+			size: header.ICMPv6MinimumSize,
+		},
 	}
 
 	handleIPv6Payload := func(hdr buffer.Prependable) {
@@ -154,10 +193,13 @@ func TestICMPCounts(t *testing.T) {
 	}
 
 	for _, typ := range types {
-		hdr := buffer.NewPrependable(header.IPv6MinimumSize + typ.size)
+		extraDataLen := len(typ.extraData)
+		hdr := buffer.NewPrependable(header.IPv6MinimumSize + typ.size + extraDataLen)
+		extraData := buffer.View(hdr.Prepend(extraDataLen))
+		copy(extraData, typ.extraData)
 		pkt := header.ICMPv6(hdr.Prepend(typ.size))
 		pkt.SetType(typ.typ)
-		pkt.SetChecksum(header.ICMPv6Checksum(pkt, r.LocalAddress, r.RemoteAddress, buffer.VectorisedView{}))
+		pkt.SetChecksum(header.ICMPv6Checksum(pkt, r.LocalAddress, r.RemoteAddress, extraData.ToVectorisedView()))
 
 		handleIPv6Payload(hdr)
 	}
@@ -372,97 +414,104 @@ func TestLinkResolution(t *testing.T) {
 }
 
 func TestICMPChecksumValidationSimple(t *testing.T) {
+	var tllData [header.NDPLinkLayerAddressSize]byte
+	header.NDPOptions(tllData[:]).Serialize(header.NDPOptionsSerializer{
+		header.NDPTargetLinkLayerAddressOption(linkAddr1),
+	})
+
 	types := []struct {
 		name        string
 		typ         header.ICMPv6Type
 		size        int
+		extraData   []byte
 		statCounter func(tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter
 	}{
 		{
-			"DstUnreachable",
-			header.ICMPv6DstUnreachable,
-			header.ICMPv6DstUnreachableMinimumSize,
-			func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
+			name: "DstUnreachable",
+			typ:  header.ICMPv6DstUnreachable,
+			size: header.ICMPv6DstUnreachableMinimumSize,
+			statCounter: func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
 				return stats.DstUnreachable
 			},
 		},
 		{
-			"PacketTooBig",
-			header.ICMPv6PacketTooBig,
-			header.ICMPv6PacketTooBigMinimumSize,
-			func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
+			name: "PacketTooBig",
+			typ:  header.ICMPv6PacketTooBig,
+			size: header.ICMPv6PacketTooBigMinimumSize,
+			statCounter: func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
 				return stats.PacketTooBig
 			},
 		},
 		{
-			"TimeExceeded",
-			header.ICMPv6TimeExceeded,
-			header.ICMPv6MinimumSize,
-			func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
+			name: "TimeExceeded",
+			typ:  header.ICMPv6TimeExceeded,
+			size: header.ICMPv6MinimumSize,
+			statCounter: func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
 				return stats.TimeExceeded
 			},
 		},
 		{
-			"ParamProblem",
-			header.ICMPv6ParamProblem,
-			header.ICMPv6MinimumSize,
-			func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
+			name: "ParamProblem",
+			typ:  header.ICMPv6ParamProblem,
+			size: header.ICMPv6MinimumSize,
+			statCounter: func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
 				return stats.ParamProblem
 			},
 		},
 		{
-			"EchoRequest",
-			header.ICMPv6EchoRequest,
-			header.ICMPv6EchoMinimumSize,
-			func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
+			name: "EchoRequest",
+			typ:  header.ICMPv6EchoRequest,
+			size: header.ICMPv6EchoMinimumSize,
+			statCounter: func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
 				return stats.EchoRequest
 			},
 		},
 		{
-			"EchoReply",
-			header.ICMPv6EchoReply,
-			header.ICMPv6EchoMinimumSize,
-			func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
+			name: "EchoReply",
+			typ:  header.ICMPv6EchoReply,
+			size: header.ICMPv6EchoMinimumSize,
+			statCounter: func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
 				return stats.EchoReply
 			},
 		},
 		{
-			"RouterSolicit",
-			header.ICMPv6RouterSolicit,
-			header.ICMPv6MinimumSize,
-			func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
+			name: "RouterSolicit",
+			typ:  header.ICMPv6RouterSolicit,
+			size: header.ICMPv6MinimumSize,
+			statCounter: func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
 				return stats.RouterSolicit
 			},
 		},
 		{
-			"RouterAdvert",
-			header.ICMPv6RouterAdvert,
-			header.ICMPv6HeaderSize + header.NDPRAMinimumSize,
-			func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
+			name: "RouterAdvert",
+			typ:  header.ICMPv6RouterAdvert,
+			size: header.ICMPv6HeaderSize + header.NDPRAMinimumSize,
+			statCounter: func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
 				return stats.RouterAdvert
 			},
 		},
 		{
-			"NeighborSolicit",
-			header.ICMPv6NeighborSolicit,
-			header.ICMPv6NeighborSolicitMinimumSize,
-			func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
+			name: "NeighborSolicit",
+			typ:  header.ICMPv6NeighborSolicit,
+			size: header.ICMPv6NeighborSolicitMinimumSize,
+			statCounter: func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
 				return stats.NeighborSolicit
 			},
 		},
 		{
-			"NeighborAdvert",
-			header.ICMPv6NeighborAdvert,
-			header.ICMPv6NeighborAdvertSize,
-			func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
+			name:      "NeighborAdvert",
+			typ:       header.ICMPv6NeighborAdvert,
+			size:      header.ICMPv6NeighborAdvertMinimumSize,
+			extraData: tllData[:],
+			statCounter: func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
 				return stats.NeighborAdvert
 			},
 		},
 		{
-			"RedirectMsg",
-			header.ICMPv6RedirectMsg,
-			header.ICMPv6MinimumSize,
-			func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
+			name: "RedirectMsg",
+			typ:  header.ICMPv6RedirectMsg,
+			size: header.ICMPv6MinimumSize,
+			statCounter: func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
 				return stats.RedirectMsg
 			},
 		},
@@ -494,16 +543,19 @@ func TestICMPChecksumValidationSimple(t *testing.T) {
 				)
 			}
 
-			handleIPv6Payload := func(typ header.ICMPv6Type, size int, checksum bool) {
-				hdr := buffer.NewPrependable(header.IPv6MinimumSize + size)
-				pkt := header.ICMPv6(hdr.Prepend(size))
-				pkt.SetType(typ)
+			handleIPv6Payload := func(checksum bool) {
+				extraDataLen := len(typ.extraData)
+				hdr := buffer.NewPrependable(header.IPv6MinimumSize + typ.size + extraDataLen)
+				extraData := buffer.View(hdr.Prepend(extraDataLen))
+				copy(extraData, typ.extraData)
+				pkt := header.ICMPv6(hdr.Prepend(typ.size))
+				pkt.SetType(typ.typ)
 				if checksum {
-					pkt.SetChecksum(header.ICMPv6Checksum(pkt, lladdr1, lladdr0, buffer.VectorisedView{}))
+					pkt.SetChecksum(header.ICMPv6Checksum(pkt, lladdr1, lladdr0, extraData.ToVectorisedView()))
 				}
 				ip := header.IPv6(hdr.Prepend(header.IPv6MinimumSize))
 				ip.Encode(&header.IPv6Fields{
-					PayloadLength: uint16(size),
+					PayloadLength: uint16(typ.size + extraDataLen),
 					NextHeader:    uint8(header.ICMPv6ProtocolNumber),
 					HopLimit:      header.NDPHopLimit,
 					SrcAddr:       lladdr1,
@@ -528,7 +580,7 @@ func TestICMPChecksumValidationSimple(t *testing.T) {
 
 			// Without setting checksum, the incoming packet should
 			// be invalid.
-			handleIPv6Payload(typ.typ, typ.size, false)
+			handleIPv6Payload(false)
 			if got := invalid.Value(); got != 1 {
 				t.Fatalf("got invalid = %d, want = 1", got)
 			}
@@ -538,7 +590,7 @@ func TestICMPChecksumValidationSimple(t *testing.T) {
 			}
 
 			// When checksum is set, it should be received.
-			handleIPv6Payload(typ.typ, typ.size, true)
+			handleIPv6Payload(true)
 			if got := typStat.Value(); got != 1 {
 				t.Fatalf("got %s = %d, want = 1", typ.name, got)
 			}
diff --git a/pkg/tcpip/network/ipv6/ndp_test.go b/pkg/tcpip/network/ipv6/ndp_test.go
index bd732f93f..c9395de52 100644
--- a/pkg/tcpip/network/ipv6/ndp_test.go
+++ b/pkg/tcpip/network/ipv6/ndp_test.go
@@ -70,76 +70,29 @@ func setupStackAndEndpoint(t *testing.T, llladdr, rlladdr tcpip.Address) (*stack
 	return s, ep
 }
 
-// TestNeighorSolicitationWithSourceLinkLayerOption tests that receiving an
-// NDP NS message with the Source Link Layer Address option results in a
+// TestNeighorSolicitationWithSourceLinkLayerOption tests that receiving a
+// valid NDP NS message with the Source Link Layer Address option results in a
 // new entry in the link address cache for the sender of the message.
 func TestNeighorSolicitationWithSourceLinkLayerOption(t *testing.T) {
 	const nicID = 1
 
-	s := stack.New(stack.Options{
-		NetworkProtocols: []stack.NetworkProtocol{NewProtocol()},
-	})
-	e := channel.New(0, 1280, linkAddr0)
-	if err := s.CreateNIC(nicID, e); err != nil {
-		t.Fatalf("CreateNIC(%d, _) = %s", nicID, err)
-	}
-	if err := s.AddAddress(nicID, ProtocolNumber, lladdr0); err != nil {
-		t.Fatalf("AddAddress(%d, %d, %s) = %s", nicID, ProtocolNumber, lladdr0, err)
-	}
-
-	ndpNSSize := header.ICMPv6NeighborSolicitMinimumSize + header.NDPLinkLayerAddressSize
-	hdr := buffer.NewPrependable(header.IPv6MinimumSize + ndpNSSize)
-	pkt := header.ICMPv6(hdr.Prepend(ndpNSSize))
-	pkt.SetType(header.ICMPv6NeighborSolicit)
-	ns := header.NDPNeighborSolicit(pkt.NDPPayload())
-	ns.SetTargetAddress(lladdr0)
-	ns.Options().Serialize(header.NDPOptionsSerializer{
-		header.NDPSourceLinkLayerAddressOption(linkAddr1),
-	})
-	pkt.SetChecksum(header.ICMPv6Checksum(pkt, lladdr1, lladdr0, buffer.VectorisedView{}))
-	payloadLength := hdr.UsedLength()
-	ip := header.IPv6(hdr.Prepend(header.IPv6MinimumSize))
-	ip.Encode(&header.IPv6Fields{
-		PayloadLength: uint16(payloadLength),
-		NextHeader:    uint8(header.ICMPv6ProtocolNumber),
-		HopLimit:      255,
-		SrcAddr:       lladdr1,
-		DstAddr:       lladdr0,
-	})
-	e.InjectInbound(ProtocolNumber, tcpip.PacketBuffer{
-		Data: hdr.View().ToVectorisedView(),
-	})
-
-	linkAddr, c, err := s.GetLinkAddress(nicID, lladdr1, lladdr0, ProtocolNumber, nil)
-	if err != nil {
-		t.Errorf("s.GetLinkAddress(%d, %s, %s, %d, nil): %s", nicID, lladdr1, lladdr0, ProtocolNumber, err)
-	}
-	if c != nil {
-		t.Errorf("got unexpected channel")
-	}
-	if linkAddr != linkAddr1 {
-		t.Errorf("got link address = %s, want = %s", linkAddr, linkAddr1)
-	}
-}
-
-// TestNeighorSolicitationWithInvalidSourceLinkLayerOption tests that receiving
-// an NDP NS message with an invalid Source Link Layer Address option does not
-// result in a new entry in the link address cache for the sender of the
-// message.
-func TestNeighorSolicitationWithInvalidSourceLinkLayerOption(t *testing.T) {
-	const nicID = 1
-
 	tests := []struct {
-		name    string
-		optsBuf []byte
+		name             string
+		optsBuf          []byte
+		expectedLinkAddr tcpip.LinkAddress
 	}{
 		{
+			name:             "Valid",
+			optsBuf:          []byte{1, 1, 2, 3, 4, 5, 6, 7},
+			expectedLinkAddr: "\x02\x03\x04\x05\x06\x07",
+		},
+		{
 			name:    "Too Small",
-			optsBuf: []byte{1, 1, 1, 2, 3, 4, 5},
+			optsBuf: []byte{1, 1, 2, 3, 4, 5, 6},
 		},
 		{
 			name:    "Invalid Length",
-			optsBuf: []byte{1, 2, 1, 2, 3, 4, 5, 6},
+			optsBuf: []byte{1, 2, 2, 3, 4, 5, 6, 7},
 		},
 	}
 
@@ -186,20 +139,138 @@ func TestNeighorSolicitationWithInvalidSourceLinkLayerOption(t *testing.T) {
 				Data: hdr.View().ToVectorisedView(),
 			})
 
-			// Invalid count should have increased.
-			if got := invalid.Value(); got != 1 {
-				t.Fatalf("got invalid = %d, want = 1", got)
+			linkAddr, c, err := s.GetLinkAddress(nicID, lladdr1, lladdr0, ProtocolNumber, nil)
+			if linkAddr != test.expectedLinkAddr {
+				t.Errorf("got link address = %s, want = %s", linkAddr, test.expectedLinkAddr)
 			}
 
-			linkAddr, c, err := s.GetLinkAddress(nicID, lladdr1, lladdr0, ProtocolNumber, nil)
-			if err != tcpip.ErrWouldBlock {
-				t.Errorf("got s.GetLinkAddress(%d, %s, %s, %d, nil) = (_, _, %v), want = (_, _, %s)", nicID, lladdr1, lladdr0, ProtocolNumber, err, tcpip.ErrWouldBlock)
+			if test.expectedLinkAddr != "" {
+				if err != nil {
+					t.Errorf("s.GetLinkAddress(%d, %s, %s, %d, nil): %s", nicID, lladdr1, lladdr0, ProtocolNumber, err)
+				}
+				if c != nil {
+					t.Errorf("got unexpected channel")
+				}
+
+				// Invalid count should not have increased.
+				if got := invalid.Value(); got != 0 {
+					t.Errorf("got invalid = %d, want = 0", got)
+				}
+			} else {
+				if err != tcpip.ErrWouldBlock {
+					t.Errorf("got s.GetLinkAddress(%d, %s, %s, %d, nil) = (_, _, %v), want = (_, _, %s)", nicID, lladdr1, lladdr0, ProtocolNumber, err, tcpip.ErrWouldBlock)
+				}
+				if c == nil {
+					t.Errorf("expected channel from call to s.GetLinkAddress(%d, %s, %s, %d, nil)", nicID, lladdr1, lladdr0, ProtocolNumber)
+				}
+
+				// Invalid count should have increased.
+				if got := invalid.Value(); got != 1 {
+					t.Errorf("got invalid = %d, want = 1", got)
+				}
+			}
+		})
+	}
+}
+
+// TestNeighorAdvertisementWithTargetLinkLayerOption tests that receiving a
+// valid NDP NA message with the Target Link Layer Address option results in a
+// new entry in the link address cache for the target of the message.
+func TestNeighorAdvertisementWithTargetLinkLayerOption(t *testing.T) {
+	const nicID = 1
+
+	tests := []struct {
+		name             string
+		optsBuf          []byte
+		expectedLinkAddr tcpip.LinkAddress
+	}{
+		{
+			name:             "Valid",
+			optsBuf:          []byte{2, 1, 2, 3, 4, 5, 6, 7},
+			expectedLinkAddr: "\x02\x03\x04\x05\x06\x07",
+		},
+		{
+			name:    "Too Small",
+			optsBuf: []byte{2, 1, 2, 3, 4, 5, 6},
+		},
+		{
+			name:    "Invalid Length",
+			optsBuf: []byte{2, 2, 2, 3, 4, 5, 6, 7},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			s := stack.New(stack.Options{
+				NetworkProtocols: []stack.NetworkProtocol{NewProtocol()},
+			})
+			e := channel.New(0, 1280, linkAddr0)
+			if err := s.CreateNIC(nicID, e); err != nil {
+				t.Fatalf("CreateNIC(%d, _) = %s", nicID, err)
+			}
+			if err := s.AddAddress(nicID, ProtocolNumber, lladdr0); err != nil {
+				t.Fatalf("AddAddress(%d, %d, %s) = %s", nicID, ProtocolNumber, lladdr0, err)
+			}
+
+			ndpNASize := header.ICMPv6NeighborAdvertMinimumSize + len(test.optsBuf)
+			hdr := buffer.NewPrependable(header.IPv6MinimumSize + ndpNASize)
+			pkt := header.ICMPv6(hdr.Prepend(ndpNASize))
+			pkt.SetType(header.ICMPv6NeighborAdvert)
+			ns := header.NDPNeighborAdvert(pkt.NDPPayload())
+			ns.SetTargetAddress(lladdr1)
+			opts := ns.Options()
+			copy(opts, test.optsBuf)
+			pkt.SetChecksum(header.ICMPv6Checksum(pkt, lladdr1, lladdr0, buffer.VectorisedView{}))
+			payloadLength := hdr.UsedLength()
+			ip := header.IPv6(hdr.Prepend(header.IPv6MinimumSize))
+			ip.Encode(&header.IPv6Fields{
+				PayloadLength: uint16(payloadLength),
+				NextHeader:    uint8(header.ICMPv6ProtocolNumber),
+				HopLimit:      255,
+				SrcAddr:       lladdr1,
+				DstAddr:       lladdr0,
+			})
+
+			invalid := s.Stats().ICMP.V6PacketsReceived.Invalid
+
+			// Invalid count should initially be 0.
+			if got := invalid.Value(); got != 0 {
+				t.Fatalf("got invalid = %d, want = 0", got)
 			}
-			if c == nil {
-				t.Errorf("expected channel from call to s.GetLinkAddress(%d, %s, %s, %d, nil)", nicID, lladdr1, lladdr0, ProtocolNumber)
+
+			e.InjectInbound(ProtocolNumber, tcpip.PacketBuffer{
+				Data: hdr.View().ToVectorisedView(),
+			})
+
+			linkAddr, c, err := s.GetLinkAddress(nicID, lladdr1, lladdr0, ProtocolNumber, nil)
+			if linkAddr != test.expectedLinkAddr {
+				t.Errorf("got link address = %s, want = %s", linkAddr, test.expectedLinkAddr)
 			}
-			if linkAddr != "" {
-				t.Errorf("got s.GetLinkAddress(%d, %s, %s, %d, nil) = (%s, _, ), want = ('', _, _)", nicID, lladdr1, lladdr0, ProtocolNumber, linkAddr)
+
+			if test.expectedLinkAddr != "" {
+				if err != nil {
+					t.Errorf("s.GetLinkAddress(%d, %s, %s, %d, nil): %s", nicID, lladdr1, lladdr0, ProtocolNumber, err)
+				}
+				if c != nil {
+					t.Errorf("got unexpected channel")
+				}
+
+				// Invalid count should not have increased.
+				if got := invalid.Value(); got != 0 {
+					t.Errorf("got invalid = %d, want = 0", got)
+				}
+			} else {
+				if err != tcpip.ErrWouldBlock {
+					t.Errorf("got s.GetLinkAddress(%d, %s, %s, %d, nil) = (_, _, %v), want = (_, _, %s)", nicID, lladdr1, lladdr0, ProtocolNumber, err, tcpip.ErrWouldBlock)
+				}
+				if c == nil {
+					t.Errorf("expected channel from call to s.GetLinkAddress(%d, %s, %s, %d, nil)", nicID, lladdr1, lladdr0, ProtocolNumber)
+				}
+
+				// Invalid count should have increased.
+				if got := invalid.Value(); got != 1 {
+					t.Errorf("got invalid = %d, want = 1", got)
+				}
 			}
 		})
 	}
@@ -238,27 +309,59 @@ func TestHopLimitValidation(t *testing.T) {
 		})
 	}
 
+	var tllData [header.NDPLinkLayerAddressSize]byte
+	header.NDPOptions(tllData[:]).Serialize(header.NDPOptionsSerializer{
+		header.NDPTargetLinkLayerAddressOption(linkAddr1),
+	})
+
 	types := []struct {
 		name        string
 		typ         header.ICMPv6Type
 		size        int
+		extraData   []byte
 		statCounter func(tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter
 	}{
-		{"RouterSolicit", header.ICMPv6RouterSolicit, header.ICMPv6MinimumSize, func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
-			return stats.RouterSolicit
-		}},
-		{"RouterAdvert", header.ICMPv6RouterAdvert, header.ICMPv6HeaderSize + header.NDPRAMinimumSize, func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
-			return stats.RouterAdvert
-		}},
-		{"NeighborSolicit", header.ICMPv6NeighborSolicit, header.ICMPv6NeighborSolicitMinimumSize, func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
-			return stats.NeighborSolicit
-		}},
-		{"NeighborAdvert", header.ICMPv6NeighborAdvert, header.ICMPv6NeighborAdvertSize, func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
-			return stats.NeighborAdvert
-		}},
-		{"RedirectMsg", header.ICMPv6RedirectMsg, header.ICMPv6MinimumSize, func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
-			return stats.RedirectMsg
-		}},
+		{
+			name: "RouterSolicit",
+			typ:  header.ICMPv6RouterSolicit,
+			size: header.ICMPv6MinimumSize,
+			statCounter: func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
+				return stats.RouterSolicit
+			},
+		},
+		{
+			name: "RouterAdvert",
+			typ:  header.ICMPv6RouterAdvert,
+			size: header.ICMPv6HeaderSize + header.NDPRAMinimumSize,
+			statCounter: func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
+				return stats.RouterAdvert
+			},
+		},
+		{
+			name: "NeighborSolicit",
+			typ:  header.ICMPv6NeighborSolicit,
+			size: header.ICMPv6NeighborSolicitMinimumSize,
+			statCounter: func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
+				return stats.NeighborSolicit
+			},
+		},
+		{
+			name:      "NeighborAdvert",
+			typ:       header.ICMPv6NeighborAdvert,
+			size:      header.ICMPv6NeighborAdvertMinimumSize,
+			extraData: tllData[:],
+			statCounter: func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
+				return stats.NeighborAdvert
+			},
+		},
+		{
+			name: "RedirectMsg",
+			typ:  header.ICMPv6RedirectMsg,
+			size: header.ICMPv6MinimumSize,
+			statCounter: func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
+				return stats.RedirectMsg
+			},
+		},
 	}
 
 	for _, typ := range types {
@@ -270,10 +373,13 @@ func TestHopLimitValidation(t *testing.T) {
 			invalid := stats.Invalid
 			typStat := typ.statCounter(stats)
 
-			hdr := buffer.NewPrependable(header.IPv6MinimumSize + typ.size)
+			extraDataLen := len(typ.extraData)
+			hdr := buffer.NewPrependable(header.IPv6MinimumSize + typ.size + extraDataLen)
+			extraData := buffer.View(hdr.Prepend(extraDataLen))
+			copy(extraData, typ.extraData)
 			pkt := header.ICMPv6(hdr.Prepend(typ.size))
 			pkt.SetType(typ.typ)
-			pkt.SetChecksum(header.ICMPv6Checksum(pkt, r.LocalAddress, r.RemoteAddress, buffer.VectorisedView{}))
+			pkt.SetChecksum(header.ICMPv6Checksum(pkt, r.LocalAddress, r.RemoteAddress, extraData.ToVectorisedView()))
 
 			// Invalid count should initially be 0.
 			if got := invalid.Value(); got != 0 {