Remove linkAddrCache

It was replaced by NUD/neighborCache.

Fixes #4658.

PiperOrigin-RevId: 356085221

3 files changed, 467 insertions, 1004 deletions

diff --git a/pkg/tcpip/network/arp/arp_test.go b/pkg/tcpip/network/arp/arp_test.go
index 24357e15d..c8b9ff9fc 100644
--- a/pkg/tcpip/network/arp/arp_test.go
+++ b/pkg/tcpip/network/arp/arp_test.go
@@ -17,7 +17,6 @@ package arp_test
 import (
 	"context"
 	"fmt"
-	"strconv"
 	"testing"
 	"time"
 
@@ -155,7 +154,7 @@ type testContext struct {
 	nudDisp *arpDispatcher
 }
 
-func newTestContext(t *testing.T, useNeighborCache bool) *testContext {
+func newTestContext(t *testing.T) *testContext {
 	c := stack.DefaultNUDConfigurations()
 	// Transition from Reachable to Stale almost immediately to test if receiving
 	// probes refreshes positive reachability.
@@ -173,7 +172,6 @@ func newTestContext(t *testing.T, useNeighborCache bool) *testContext {
 		TransportProtocols: []stack.TransportProtocolFactory{icmp.NewProtocol4},
 		NUDConfigs:         c,
 		NUDDisp:            &d,
-		UseNeighborCache:   useNeighborCache,
 	})
 
 	ep := channel.New(defaultChannelSize, defaultMTU, stackLinkAddr)
@@ -191,15 +189,6 @@ func newTestContext(t *testing.T, useNeighborCache bool) *testContext {
 	if err := s.AddAddress(nicID, ipv4.ProtocolNumber, stackAddr); err != nil {
 		t.Fatalf("AddAddress for ipv4 failed: %v", err)
 	}
-	if !useNeighborCache {
-		// The remote address needs to be assigned to the NIC so we can receive and
-		// verify outgoing ARP packets. The neighbor cache isn't concerned with
-		// this; the tests that use linkAddrCache expect the ARP responses to be
-		// received by the same NIC.
-		if err := s.AddAddress(nicID, ipv4.ProtocolNumber, remoteAddr); err != nil {
-			t.Fatalf("AddAddress for ipv4 failed: %v", err)
-		}
-	}
 
 	s.SetRouteTable([]tcpip.Route{{
 		Destination: header.IPv4EmptySubnet,
@@ -217,86 +206,8 @@ func (c *testContext) cleanup() {
 	c.linkEP.Close()
 }
 
-func TestDirectRequest(t *testing.T) {
-	c := newTestContext(t, false /* useNeighborCache */)
-	defer c.cleanup()
-
-	const senderMAC = "\x01\x02\x03\x04\x05\x06"
-	const senderIPv4 = "\x0a\x00\x00\x02"
-
-	v := make(buffer.View, header.ARPSize)
-	h := header.ARP(v)
-	h.SetIPv4OverEthernet()
-	h.SetOp(header.ARPRequest)
-	copy(h.HardwareAddressSender(), senderMAC)
-	copy(h.ProtocolAddressSender(), senderIPv4)
-
-	inject := func(addr tcpip.Address) {
-		copy(h.ProtocolAddressTarget(), addr)
-		c.linkEP.InjectInbound(arp.ProtocolNumber, stack.NewPacketBuffer(stack.PacketBufferOptions{
-			Data: v.ToVectorisedView(),
-		}))
-	}
-
-	for i, address := range []tcpip.Address{stackAddr, remoteAddr} {
-		t.Run(strconv.Itoa(i), func(t *testing.T) {
-			expectedPacketsReceived := c.s.Stats().ARP.PacketsReceived.Value() + 1
-			expectedRequestsReceived := c.s.Stats().ARP.RequestsReceived.Value() + 1
-			expectedRepliesSent := c.s.Stats().ARP.OutgoingRepliesSent.Value() + 1
-
-			inject(address)
-			pi, _ := c.linkEP.ReadContext(context.Background())
-			if pi.Proto != arp.ProtocolNumber {
-				t.Fatalf("expected ARP response, got network protocol number %d", pi.Proto)
-			}
-			rep := header.ARP(pi.Pkt.NetworkHeader().View())
-			if !rep.IsValid() {
-				t.Fatalf("invalid ARP response: len = %d; response = %x", len(rep), rep)
-			}
-			if got := rep.Op(); got != header.ARPReply {
-				t.Fatalf("got Op = %d, want = %d", got, header.ARPReply)
-			}
-			if got, want := tcpip.LinkAddress(rep.HardwareAddressSender()), stackLinkAddr; got != want {
-				t.Errorf("got HardwareAddressSender = %s, want = %s", got, want)
-			}
-			if got, want := tcpip.Address(rep.ProtocolAddressSender()), tcpip.Address(h.ProtocolAddressTarget()); got != want {
-				t.Errorf("got ProtocolAddressSender = %s, want = %s", got, want)
-			}
-			if got, want := tcpip.LinkAddress(rep.HardwareAddressTarget()), tcpip.LinkAddress(h.HardwareAddressSender()); got != want {
-				t.Errorf("got HardwareAddressTarget = %s, want = %s", got, want)
-			}
-			if got, want := tcpip.Address(rep.ProtocolAddressTarget()), tcpip.Address(h.ProtocolAddressSender()); got != want {
-				t.Errorf("got ProtocolAddressTarget = %s, want = %s", got, want)
-			}
-
-			if got := c.s.Stats().ARP.PacketsReceived.Value(); got != expectedPacketsReceived {
-				t.Errorf("got c.s.Stats().ARP.PacketsReceived.Value() = %d, want = %d", got, expectedPacketsReceived)
-			}
-			if got := c.s.Stats().ARP.RequestsReceived.Value(); got != expectedRequestsReceived {
-				t.Errorf("got c.s.Stats().ARP.PacketsReceived.Value() = %d, want = %d", got, expectedRequestsReceived)
-			}
-			if got := c.s.Stats().ARP.OutgoingRepliesSent.Value(); got != expectedRepliesSent {
-				t.Errorf("got c.s.Stats().ARP.OutgoingRepliesSent.Value() = %d, want = %d", got, expectedRepliesSent)
-			}
-		})
-	}
-
-	inject(unknownAddr)
-	// Sleep tests are gross, but this will only potentially flake
-	// if there's a bug. If there is no bug this will reliably
-	// succeed.
-	ctx, cancel := context.WithTimeout(context.Background(), 100*time.Millisecond)
-	defer cancel()
-	if pkt, ok := c.linkEP.ReadContext(ctx); ok {
-		t.Errorf("stackAddrBad: unexpected packet sent, Proto=%v", pkt.Proto)
-	}
-	if got := c.s.Stats().ARP.RequestsReceivedUnknownTargetAddress.Value(); got != 1 {
-		t.Errorf("got c.s.Stats().ARP.RequestsReceivedUnKnownTargetAddress.Value() = %d, want = 1", got)
-	}
-}
-
 func TestMalformedPacket(t *testing.T) {
-	c := newTestContext(t, false)
+	c := newTestContext(t)
 	defer c.cleanup()
 
 	v := make(buffer.View, header.ARPSize)
@@ -315,7 +226,7 @@ func TestMalformedPacket(t *testing.T) {
 }
 
 func TestDisabledEndpoint(t *testing.T) {
-	c := newTestContext(t, false)
+	c := newTestContext(t)
 	defer c.cleanup()
 
 	ep, err := c.s.GetNetworkEndpoint(nicID, header.ARPProtocolNumber)
@@ -340,7 +251,7 @@ func TestDisabledEndpoint(t *testing.T) {
 }
 
 func TestDirectReply(t *testing.T) {
-	c := newTestContext(t, false)
+	c := newTestContext(t)
 	defer c.cleanup()
 
 	const senderMAC = "\x01\x02\x03\x04\x05\x06"
@@ -370,8 +281,8 @@ func TestDirectReply(t *testing.T) {
 	}
 }
 
-func TestDirectRequestWithNeighborCache(t *testing.T) {
-	c := newTestContext(t, true /* useNeighborCache */)
+func TestDirectRequest(t *testing.T) {
+	c := newTestContext(t)
 	defer c.cleanup()
 
 	tests := []struct {
diff --git a/pkg/tcpip/network/ipv6/icmp_test.go b/pkg/tcpip/network/ipv6/icmp_test.go
index 4dbfb80da..69c1e4bea 100644
--- a/pkg/tcpip/network/ipv6/icmp_test.go
+++ b/pkg/tcpip/network/ipv6/icmp_test.go
@@ -175,168 +175,9 @@ func handleICMPInIPv6(ep stack.NetworkEndpoint, src, dst tcpip.Address, icmp hea
 }
 
 func TestICMPCounts(t *testing.T) {
-	tests := []struct {
-		name             string
-		useNeighborCache bool
-	}{
-		{
-			name:             "linkAddrCache",
-			useNeighborCache: false,
-		},
-		{
-			name:             "neighborCache",
-			useNeighborCache: true,
-		},
-	}
-
-	for _, test := range tests {
-		t.Run(test.name, func(t *testing.T) {
-			s := stack.New(stack.Options{
-				NetworkProtocols:   []stack.NetworkProtocolFactory{NewProtocol},
-				TransportProtocols: []stack.TransportProtocolFactory{icmp.NewProtocol6},
-				UseNeighborCache:   test.useNeighborCache,
-			})
-			if err := s.CreateNIC(nicID, &stubLinkEndpoint{}); err != nil {
-				t.Fatalf("CreateNIC(_, _) = %s", err)
-			}
-			{
-				subnet, err := tcpip.NewSubnet(lladdr1, tcpip.AddressMask(strings.Repeat("\xff", len(lladdr1))))
-				if err != nil {
-					t.Fatal(err)
-				}
-				s.SetRouteTable(
-					[]tcpip.Route{{
-						Destination: subnet,
-						NIC:         nicID,
-					}},
-				)
-			}
-
-			netProto := s.NetworkProtocolInstance(ProtocolNumber)
-			if netProto == nil {
-				t.Fatalf("cannot find protocol instance for network protocol %d", ProtocolNumber)
-			}
-			ep := netProto.NewEndpoint(&testInterface{}, &stubDispatcher{})
-			defer ep.Close()
-
-			if err := ep.Enable(); err != nil {
-				t.Fatalf("ep.Enable(): %s", err)
-			}
-
-			addressableEndpoint, ok := ep.(stack.AddressableEndpoint)
-			if !ok {
-				t.Fatalf("expected network endpoint to implement stack.AddressableEndpoint")
-			}
-			addr := lladdr0.WithPrefix()
-			if ep, err := addressableEndpoint.AddAndAcquirePermanentAddress(addr, stack.CanBePrimaryEndpoint, stack.AddressConfigStatic, false /* deprecated */); err != nil {
-				t.Fatalf("addressableEndpoint.AddAndAcquirePermanentAddress(%s, CanBePrimaryEndpoint, AddressConfigStatic, false): %s", addr, err)
-			} else {
-				ep.DecRef()
-			}
-
-			var tllData [header.NDPLinkLayerAddressSize]byte
-			header.NDPOptions(tllData[:]).Serialize(header.NDPOptionsSerializer{
-				header.NDPTargetLinkLayerAddressOption(linkAddr1),
-			})
-
-			types := []struct {
-				typ       header.ICMPv6Type
-				size      int
-				extraData []byte
-			}{
-				{
-					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,
-				},
-				{
-					typ:  header.ICMPv6MulticastListenerQuery,
-					size: header.MLDMinimumSize + header.ICMPv6HeaderSize,
-				},
-				{
-					typ:  header.ICMPv6MulticastListenerReport,
-					size: header.MLDMinimumSize + header.ICMPv6HeaderSize,
-				},
-				{
-					typ:  header.ICMPv6MulticastListenerDone,
-					size: header.MLDMinimumSize + header.ICMPv6HeaderSize,
-				},
-				{
-					typ:  255, /* Unrecognized */
-					size: 50,
-				},
-			}
-
-			for _, typ := range types {
-				icmp := header.ICMPv6(buffer.NewView(typ.size + len(typ.extraData)))
-				copy(icmp[typ.size:], typ.extraData)
-				icmp.SetType(typ.typ)
-				icmp.SetChecksum(header.ICMPv6Checksum(icmp[:typ.size], lladdr0, lladdr1, buffer.View(typ.extraData).ToVectorisedView()))
-				handleICMPInIPv6(ep, lladdr1, lladdr0, icmp)
-			}
-
-			// Construct an empty ICMP packet so that
-			// Stats().ICMP.ICMPv6ReceivedPacketStats.Invalid is incremented.
-			handleICMPInIPv6(ep, lladdr1, lladdr0, header.ICMPv6(buffer.NewView(header.IPv6MinimumSize)))
-
-			icmpv6Stats := s.Stats().ICMP.V6.PacketsReceived
-			visitStats(reflect.ValueOf(&icmpv6Stats).Elem(), func(name string, s *tcpip.StatCounter) {
-				if got, want := s.Value(), uint64(1); got != want {
-					t.Errorf("got %s = %d, want = %d", name, got, want)
-				}
-			})
-			if t.Failed() {
-				t.Logf("stats:\n%+v", s.Stats())
-			}
-		})
-	}
-}
-
-func TestICMPCountsWithNeighborCache(t *testing.T) {
 	s := stack.New(stack.Options{
 		NetworkProtocols:   []stack.NetworkProtocolFactory{NewProtocol},
 		TransportProtocols: []stack.TransportProtocolFactory{icmp.NewProtocol6},
-		UseNeighborCache:   true,
 	})
 	if err := s.CreateNIC(nicID, &stubLinkEndpoint{}); err != nil {
 		t.Fatalf("CreateNIC(_, _) = %s", err)
@@ -770,135 +611,116 @@ func TestICMPChecksumValidationSimple(t *testing.T) {
 		},
 	}
 
-	tests := []struct {
-		name             string
-		useNeighborCache bool
-	}{
-		{
-			name:             "linkAddrCache",
-			useNeighborCache: false,
-		},
-		{
-			name:             "neighborCache",
-			useNeighborCache: true,
-		},
-	}
+	for _, typ := range types {
+		for _, isRouter := range []bool{false, true} {
+			name := typ.name
+			if isRouter {
+				name += " (Router)"
+			}
+			t.Run(name, func(t *testing.T) {
+				e := channel.New(0, 1280, linkAddr0)
 
-	for _, test := range tests {
-		t.Run(test.name, func(t *testing.T) {
-			for _, typ := range types {
-				for _, isRouter := range []bool{false, true} {
-					name := typ.name
-					if isRouter {
-						name += " (Router)"
+				// Indicate that resolution for link layer addresses is required to
+				// send packets over this link. This is needed so the NIC knows to
+				// allocate a neighbor table.
+				e.LinkEPCapabilities |= stack.CapabilityResolutionRequired
+
+				s := stack.New(stack.Options{
+					NetworkProtocols: []stack.NetworkProtocolFactory{NewProtocol},
+				})
+				if isRouter {
+					// Enabling forwarding makes the stack act as a router.
+					s.SetForwarding(ProtocolNumber, true)
+				}
+				if err := s.CreateNIC(nicID, e); err != nil {
+					t.Fatalf("CreateNIC(_, _) = %s", err)
+				}
+
+				if err := s.AddAddress(nicID, ProtocolNumber, lladdr0); err != nil {
+					t.Fatalf("AddAddress(_, %d, %s) = %s", ProtocolNumber, lladdr0, err)
+				}
+				{
+					subnet, err := tcpip.NewSubnet(lladdr1, tcpip.AddressMask(strings.Repeat("\xff", len(lladdr1))))
+					if err != nil {
+						t.Fatal(err)
+					}
+					s.SetRouteTable(
+						[]tcpip.Route{{
+							Destination: subnet,
+							NIC:         nicID,
+						}},
+					)
+				}
+
+				handleIPv6Payload := func(checksum bool) {
+					icmp := header.ICMPv6(buffer.NewView(typ.size + len(typ.extraData)))
+					copy(icmp[typ.size:], typ.extraData)
+					icmp.SetType(typ.typ)
+					if checksum {
+						icmp.SetChecksum(header.ICMPv6Checksum(icmp, lladdr1, lladdr0, buffer.View{}.ToVectorisedView()))
 					}
-					t.Run(name, func(t *testing.T) {
-						e := channel.New(0, 1280, linkAddr0)
-
-						// Indicate that resolution for link layer addresses is required to
-						// send packets over this link. This is needed so the NIC knows to
-						// allocate a neighbor table.
-						e.LinkEPCapabilities |= stack.CapabilityResolutionRequired
-
-						s := stack.New(stack.Options{
-							NetworkProtocols: []stack.NetworkProtocolFactory{NewProtocol},
-							UseNeighborCache: test.useNeighborCache,
-						})
-						if isRouter {
-							// Enabling forwarding makes the stack act as a router.
-							s.SetForwarding(ProtocolNumber, true)
-						}
-						if err := s.CreateNIC(nicID, e); err != nil {
-							t.Fatalf("CreateNIC(_, _) = %s", err)
-						}
-
-						if err := s.AddAddress(nicID, ProtocolNumber, lladdr0); err != nil {
-							t.Fatalf("AddAddress(_, %d, %s) = %s", ProtocolNumber, lladdr0, err)
-						}
-						{
-							subnet, err := tcpip.NewSubnet(lladdr1, tcpip.AddressMask(strings.Repeat("\xff", len(lladdr1))))
-							if err != nil {
-								t.Fatal(err)
-							}
-							s.SetRouteTable(
-								[]tcpip.Route{{
-									Destination: subnet,
-									NIC:         nicID,
-								}},
-							)
-						}
-
-						handleIPv6Payload := func(checksum bool) {
-							icmp := header.ICMPv6(buffer.NewView(typ.size + len(typ.extraData)))
-							copy(icmp[typ.size:], typ.extraData)
-							icmp.SetType(typ.typ)
-							if checksum {
-								icmp.SetChecksum(header.ICMPv6Checksum(icmp, lladdr1, lladdr0, buffer.View{}.ToVectorisedView()))
-							}
-							ip := header.IPv6(buffer.NewView(header.IPv6MinimumSize))
-							ip.Encode(&header.IPv6Fields{
-								PayloadLength:     uint16(len(icmp)),
-								TransportProtocol: header.ICMPv6ProtocolNumber,
-								HopLimit:          header.NDPHopLimit,
-								SrcAddr:           lladdr1,
-								DstAddr:           lladdr0,
-							})
-							pkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
-								Data: buffer.NewVectorisedView(len(ip)+len(icmp), []buffer.View{buffer.View(ip), buffer.View(icmp)}),
-							})
-							e.InjectInbound(ProtocolNumber, pkt)
-						}
-
-						stats := s.Stats().ICMP.V6.PacketsReceived
-						invalid := stats.Invalid
-						routerOnly := stats.RouterOnlyPacketsDroppedByHost
-						typStat := typ.statCounter(stats)
-
-						// Initial stat counts should be 0.
-						if got := invalid.Value(); got != 0 {
-							t.Fatalf("got invalid = %d, want = 0", got)
-						}
-						if got := routerOnly.Value(); got != 0 {
-							t.Fatalf("got RouterOnlyPacketsReceivedByHost = %d, want = 0", got)
-						}
-						if got := typStat.Value(); got != 0 {
-							t.Fatalf("got %s = %d, want = 0", typ.name, got)
-						}
-
-						// Without setting checksum, the incoming packet should
-						// be invalid.
-						handleIPv6Payload(false)
-						if got := invalid.Value(); got != 1 {
-							t.Fatalf("got invalid = %d, want = 1", got)
-						}
-						// Router only count should not have increased.
-						if got := routerOnly.Value(); got != 0 {
-							t.Fatalf("got RouterOnlyPacketsReceivedByHost = %d, want = 0", got)
-						}
-						// Rx count of type typ.typ should not have increased.
-						if got := typStat.Value(); got != 0 {
-							t.Fatalf("got %s = %d, want = 0", typ.name, got)
-						}
-
-						// When checksum is set, it should be received.
-						handleIPv6Payload(true)
-						if got := typStat.Value(); got != 1 {
-							t.Fatalf("got %s = %d, want = 1", typ.name, got)
-						}
-						// Invalid count should not have increased again.
-						if got := invalid.Value(); got != 1 {
-							t.Fatalf("got invalid = %d, want = 1", got)
-						}
-						if !isRouter && typ.routerOnly && test.useNeighborCache {
-							// Router only count should have increased.
-							if got := routerOnly.Value(); got != 1 {
-								t.Fatalf("got RouterOnlyPacketsReceivedByHost = %d, want = 1", got)
-							}
-						}
+					ip := header.IPv6(buffer.NewView(header.IPv6MinimumSize))
+					ip.Encode(&header.IPv6Fields{
+						PayloadLength:     uint16(len(icmp)),
+						TransportProtocol: header.ICMPv6ProtocolNumber,
+						HopLimit:          header.NDPHopLimit,
+						SrcAddr:           lladdr1,
+						DstAddr:           lladdr0,
 					})
+					pkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
+						Data: buffer.NewVectorisedView(len(ip)+len(icmp), []buffer.View{buffer.View(ip), buffer.View(icmp)}),
+					})
+					e.InjectInbound(ProtocolNumber, pkt)
 				}
-			}
-		})
+
+				stats := s.Stats().ICMP.V6.PacketsReceived
+				invalid := stats.Invalid
+				routerOnly := stats.RouterOnlyPacketsDroppedByHost
+				typStat := typ.statCounter(stats)
+
+				// Initial stat counts should be 0.
+				if got := invalid.Value(); got != 0 {
+					t.Fatalf("got invalid = %d, want = 0", got)
+				}
+				if got := routerOnly.Value(); got != 0 {
+					t.Fatalf("got RouterOnlyPacketsReceivedByHost = %d, want = 0", got)
+				}
+				if got := typStat.Value(); got != 0 {
+					t.Fatalf("got %s = %d, want = 0", typ.name, got)
+				}
+
+				// Without setting checksum, the incoming packet should
+				// be invalid.
+				handleIPv6Payload(false)
+				if got := invalid.Value(); got != 1 {
+					t.Fatalf("got invalid = %d, want = 1", got)
+				}
+				// Router only count should not have increased.
+				if got := routerOnly.Value(); got != 0 {
+					t.Fatalf("got RouterOnlyPacketsReceivedByHost = %d, want = 0", got)
+				}
+				// Rx count of type typ.typ should not have increased.
+				if got := typStat.Value(); got != 0 {
+					t.Fatalf("got %s = %d, want = 0", typ.name, got)
+				}
+
+				// When checksum is set, it should be received.
+				handleIPv6Payload(true)
+				if got := typStat.Value(); got != 1 {
+					t.Fatalf("got %s = %d, want = 1", typ.name, got)
+				}
+				// Invalid count should not have increased again.
+				if got := invalid.Value(); got != 1 {
+					t.Fatalf("got invalid = %d, want = 1", got)
+				}
+				if !isRouter && typ.routerOnly {
+					// Router only count should have increased.
+					if got := routerOnly.Value(); got != 1 {
+						t.Fatalf("got RouterOnlyPacketsReceivedByHost = %d, want = 1", got)
+					}
+				}
+			})
+		}
 	}
 }
 
@@ -1762,7 +1584,6 @@ func TestCallsToNeighborCache(t *testing.T) {
 			s := stack.New(stack.Options{
 				NetworkProtocols:   []stack.NetworkProtocolFactory{NewProtocol},
 				TransportProtocols: []stack.TransportProtocolFactory{icmp.NewProtocol6},
-				UseNeighborCache:   true,
 			})
 			{
 				if err := s.CreateNIC(nicID, &stubLinkEndpoint{}); err != nil {
diff --git a/pkg/tcpip/network/ipv6/ndp_test.go b/pkg/tcpip/network/ipv6/ndp_test.go
index 104fe2139..5ff247653 100644
--- a/pkg/tcpip/network/ipv6/ndp_test.go
+++ b/pkg/tcpip/network/ipv6/ndp_test.go
@@ -33,13 +33,12 @@ import (
 // setupStackAndEndpoint creates a stack with a single NIC with a link-local
 // address llladdr and an IPv6 endpoint to a remote with link-local address
 // rlladdr
-func setupStackAndEndpoint(t *testing.T, llladdr, rlladdr tcpip.Address, useNeighborCache bool) (*stack.Stack, stack.NetworkEndpoint) {
+func setupStackAndEndpoint(t *testing.T, llladdr, rlladdr tcpip.Address) (*stack.Stack, stack.NetworkEndpoint) {
 	t.Helper()
 
 	s := stack.New(stack.Options{
 		NetworkProtocols:   []stack.NetworkProtocolFactory{NewProtocol},
 		TransportProtocols: []stack.TransportProtocolFactory{icmp.NewProtocol6},
-		UseNeighborCache:   useNeighborCache,
 	})
 
 	if err := s.CreateNIC(1, &stubLinkEndpoint{}); err != nil {
@@ -237,107 +236,6 @@ func TestNeighborSolicitationWithSourceLinkLayerOption(t *testing.T) {
 				Data: hdr.View().ToVectorisedView(),
 			}))
 
-			ch := make(chan stack.LinkResolutionResult, 1)
-			err := s.GetLinkAddress(nicID, lladdr1, lladdr0, ProtocolNumber, func(r stack.LinkResolutionResult) {
-				ch <- r
-			})
-
-			wantInvalid := uint64(0)
-			wantSucccess := true
-			if len(test.expectedLinkAddr) == 0 {
-				wantInvalid = 1
-				wantSucccess = false
-				if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
-					t.Errorf("got s.GetLinkAddress(%d, %s, %s, %d, _) = %s, want = %s", nicID, lladdr1, lladdr0, ProtocolNumber, err, &tcpip.ErrWouldBlock{})
-				}
-			} else {
-				if err != nil {
-					t.Errorf("got s.GetLinkAddress(%d, %s, %s, %d, _) = %s, want = nil", nicID, lladdr1, lladdr0, ProtocolNumber, err)
-				}
-			}
-
-			if diff := cmp.Diff(stack.LinkResolutionResult{LinkAddress: test.expectedLinkAddr, Success: wantSucccess}, <-ch); diff != "" {
-				t.Errorf("linkResolutionResult mismatch (-want +got):\n%s", diff)
-			}
-			if got := invalid.Value(); got != wantInvalid {
-				t.Errorf("got invalid = %d, want = %d", got, wantInvalid)
-			}
-		})
-	}
-}
-
-// TestNeighborSolicitationWithSourceLinkLayerOptionUsingNeighborCache 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 TestNeighborSolicitationWithSourceLinkLayerOptionUsingNeighborCache(t *testing.T) {
-	const nicID = 1
-
-	tests := []struct {
-		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, 2, 3, 4, 5, 6},
-		},
-		{
-			name:    "Invalid Length",
-			optsBuf: []byte{1, 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.NetworkProtocolFactory{NewProtocol},
-				UseNeighborCache: true,
-			})
-			e := channel.New(0, 1280, linkAddr0)
-			e.LinkEPCapabilities |= stack.CapabilityResolutionRequired
-			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 + len(test.optsBuf)
-			hdr := buffer.NewPrependable(header.IPv6MinimumSize + ndpNSSize)
-			pkt := header.ICMPv6(hdr.Prepend(ndpNSSize))
-			pkt.SetType(header.ICMPv6NeighborSolicit)
-			ns := header.NDPNeighborSolicit(pkt.MessageBody())
-			ns.SetTargetAddress(lladdr0)
-			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),
-				TransportProtocol: header.ICMPv6ProtocolNumber,
-				HopLimit:          255,
-				SrcAddr:           lladdr1,
-				DstAddr:           lladdr0,
-			})
-
-			invalid := s.Stats().ICMP.V6.PacketsReceived.Invalid
-
-			// Invalid count should initially be 0.
-			if got := invalid.Value(); got != 0 {
-				t.Fatalf("got invalid = %d, want = 0", got)
-			}
-
-			e.InjectInbound(ProtocolNumber, stack.NewPacketBuffer(stack.PacketBufferOptions{
-				Data: hdr.View().ToVectorisedView(),
-			}))
-
 			neighbors, err := s.Neighbors(nicID, ProtocolNumber)
 			if err != nil {
 				t.Fatalf("s.Neighbors(%d, %d): %s", nicID, ProtocolNumber, err)
@@ -392,20 +290,6 @@ func TestNeighborSolicitationResponse(t *testing.T) {
 	remoteLinkAddr0 := linkAddr1
 	remoteLinkAddr1 := linkAddr2
 
-	stacks := []struct {
-		name             string
-		useNeighborCache bool
-	}{
-		{
-			name:             "linkAddrCache",
-			useNeighborCache: false,
-		},
-		{
-			name:             "neighborCache",
-			useNeighborCache: true,
-		},
-	}
-
 	tests := []struct {
 		name                   string
 		nsOpts                 header.NDPOptionsSerializer
@@ -564,229 +448,44 @@ func TestNeighborSolicitationResponse(t *testing.T) {
 		},
 	}
 
-	for _, stackTyp := range stacks {
-		t.Run(stackTyp.name, func(t *testing.T) {
-			for _, test := range tests {
-				t.Run(test.name, func(t *testing.T) {
-					s := stack.New(stack.Options{
-						NetworkProtocols: []stack.NetworkProtocolFactory{NewProtocol},
-						UseNeighborCache: stackTyp.useNeighborCache,
-					})
-					e := channel.New(1, 1280, nicLinkAddr)
-					e.LinkEPCapabilities |= stack.CapabilityResolutionRequired
-					if err := s.CreateNIC(nicID, e); err != nil {
-						t.Fatalf("CreateNIC(%d, _) = %s", nicID, err)
-					}
-					if err := s.AddAddress(nicID, ProtocolNumber, nicAddr); err != nil {
-						t.Fatalf("AddAddress(%d, %d, %s) = %s", nicID, ProtocolNumber, nicAddr, err)
-					}
-
-					s.SetRouteTable([]tcpip.Route{
-						{
-							Destination: header.IPv6EmptySubnet,
-							NIC:         1,
-						},
-					})
-
-					ndpNSSize := header.ICMPv6NeighborSolicitMinimumSize + test.nsOpts.Length()
-					hdr := buffer.NewPrependable(header.IPv6MinimumSize + ndpNSSize)
-					pkt := header.ICMPv6(hdr.Prepend(ndpNSSize))
-					pkt.SetType(header.ICMPv6NeighborSolicit)
-					ns := header.NDPNeighborSolicit(pkt.MessageBody())
-					ns.SetTargetAddress(nicAddr)
-					opts := ns.Options()
-					opts.Serialize(test.nsOpts)
-					pkt.SetChecksum(header.ICMPv6Checksum(pkt, test.nsSrc, test.nsDst, buffer.VectorisedView{}))
-					payloadLength := hdr.UsedLength()
-					ip := header.IPv6(hdr.Prepend(header.IPv6MinimumSize))
-					ip.Encode(&header.IPv6Fields{
-						PayloadLength:     uint16(payloadLength),
-						TransportProtocol: header.ICMPv6ProtocolNumber,
-						HopLimit:          255,
-						SrcAddr:           test.nsSrc,
-						DstAddr:           test.nsDst,
-					})
-
-					invalid := s.Stats().ICMP.V6.PacketsReceived.Invalid
-
-					// Invalid count should initially be 0.
-					if got := invalid.Value(); got != 0 {
-						t.Fatalf("got invalid = %d, want = 0", got)
-					}
-
-					e.InjectLinkAddr(ProtocolNumber, test.nsSrcLinkAddr, stack.NewPacketBuffer(stack.PacketBufferOptions{
-						Data: hdr.View().ToVectorisedView(),
-					}))
-
-					if test.nsInvalid {
-						if got := invalid.Value(); got != 1 {
-							t.Fatalf("got invalid = %d, want = 1", got)
-						}
-
-						if p, got := e.Read(); got {
-							t.Fatalf("unexpected response to an invalid NS = %+v", p.Pkt)
-						}
-
-						// If we expected the NS to be invalid, we have nothing else to check.
-						return
-					}
-
-					if got := invalid.Value(); got != 0 {
-						t.Fatalf("got invalid = %d, want = 0", got)
-					}
-
-					if test.performsLinkResolution {
-						p, got := e.ReadContext(context.Background())
-						if !got {
-							t.Fatal("expected an NDP NS response")
-						}
-
-						respNSDst := header.SolicitedNodeAddr(test.nsSrc)
-						var want stack.RouteInfo
-						want.NetProto = ProtocolNumber
-						want.RemoteLinkAddress = header.EthernetAddressFromMulticastIPv6Address(respNSDst)
-						if diff := cmp.Diff(want, p.Route, cmp.AllowUnexported(want)); diff != "" {
-							t.Errorf("route info mismatch (-want +got):\n%s", diff)
-						}
-
-						checker.IPv6(t, stack.PayloadSince(p.Pkt.NetworkHeader()),
-							checker.SrcAddr(nicAddr),
-							checker.DstAddr(respNSDst),
-							checker.TTL(header.NDPHopLimit),
-							checker.NDPNS(
-								checker.NDPNSTargetAddress(test.nsSrc),
-								checker.NDPNSOptions([]header.NDPOption{
-									header.NDPSourceLinkLayerAddressOption(nicLinkAddr),
-								}),
-							))
-
-						ser := header.NDPOptionsSerializer{
-							header.NDPTargetLinkLayerAddressOption(linkAddr1),
-						}
-						ndpNASize := header.ICMPv6NeighborAdvertMinimumSize + ser.Length()
-						hdr := buffer.NewPrependable(header.IPv6MinimumSize + ndpNASize)
-						pkt := header.ICMPv6(hdr.Prepend(ndpNASize))
-						pkt.SetType(header.ICMPv6NeighborAdvert)
-						na := header.NDPNeighborAdvert(pkt.MessageBody())
-						na.SetSolicitedFlag(true)
-						na.SetOverrideFlag(true)
-						na.SetTargetAddress(test.nsSrc)
-						na.Options().Serialize(ser)
-						pkt.SetChecksum(header.ICMPv6Checksum(pkt, test.nsSrc, nicAddr, buffer.VectorisedView{}))
-						payloadLength := hdr.UsedLength()
-						ip := header.IPv6(hdr.Prepend(header.IPv6MinimumSize))
-						ip.Encode(&header.IPv6Fields{
-							PayloadLength:     uint16(payloadLength),
-							TransportProtocol: header.ICMPv6ProtocolNumber,
-							HopLimit:          header.NDPHopLimit,
-							SrcAddr:           test.nsSrc,
-							DstAddr:           nicAddr,
-						})
-						e.InjectLinkAddr(ProtocolNumber, "", stack.NewPacketBuffer(stack.PacketBufferOptions{
-							Data: hdr.View().ToVectorisedView(),
-						}))
-					}
-
-					p, got := e.ReadContext(context.Background())
-					if !got {
-						t.Fatal("expected an NDP NA response")
-					}
-
-					if p.Route.LocalAddress != test.naSrc {
-						t.Errorf("got p.Route.LocalAddress = %s, want = %s", p.Route.LocalAddress, test.naSrc)
-					}
-					if p.Route.LocalLinkAddress != nicLinkAddr {
-						t.Errorf("p.Route.LocalLinkAddress = %s, want = %s", p.Route.LocalLinkAddress, nicLinkAddr)
-					}
-					if p.Route.RemoteAddress != test.naDst {
-						t.Errorf("got p.Route.RemoteAddress = %s, want = %s", p.Route.RemoteAddress, test.naDst)
-					}
-					if p.Route.RemoteLinkAddress != test.naDstLinkAddr {
-						t.Errorf("got p.Route.RemoteLinkAddress = %s, want = %s", p.Route.RemoteLinkAddress, test.naDstLinkAddr)
-					}
-
-					checker.IPv6(t, stack.PayloadSince(p.Pkt.NetworkHeader()),
-						checker.SrcAddr(test.naSrc),
-						checker.DstAddr(test.naDst),
-						checker.TTL(header.NDPHopLimit),
-						checker.NDPNA(
-							checker.NDPNASolicitedFlag(test.naSolicited),
-							checker.NDPNATargetAddress(nicAddr),
-							checker.NDPNAOptions([]header.NDPOption{
-								header.NDPTargetLinkLayerAddressOption(nicLinkAddr[:]),
-							}),
-						))
-				})
-			}
-		})
-	}
-}
-
-// TestNeighborAdvertisementWithTargetLinkLayerOption 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 TestNeighborAdvertisementWithTargetLinkLayerOption(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},
-		},
-		{
-			name: "Multiple",
-			optsBuf: []byte{
-				2, 1, 2, 3, 4, 5, 6, 7,
-				2, 1, 2, 3, 4, 5, 6, 8,
-			},
-		},
-	}
-
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
 			s := stack.New(stack.Options{
 				NetworkProtocols: []stack.NetworkProtocolFactory{NewProtocol},
-				UseLinkAddrCache: true,
 			})
-			e := channel.New(0, 1280, linkAddr0)
+			e := channel.New(1, 1280, nicLinkAddr)
 			e.LinkEPCapabilities |= stack.CapabilityResolutionRequired
 			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)
+			if err := s.AddAddress(nicID, ProtocolNumber, nicAddr); err != nil {
+				t.Fatalf("AddAddress(%d, %d, %s) = %s", nicID, ProtocolNumber, nicAddr, 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.MessageBody())
-			ns.SetTargetAddress(lladdr1)
+			s.SetRouteTable([]tcpip.Route{
+				{
+					Destination: header.IPv6EmptySubnet,
+					NIC:         1,
+				},
+			})
+
+			ndpNSSize := header.ICMPv6NeighborSolicitMinimumSize + test.nsOpts.Length()
+			hdr := buffer.NewPrependable(header.IPv6MinimumSize + ndpNSSize)
+			pkt := header.ICMPv6(hdr.Prepend(ndpNSSize))
+			pkt.SetType(header.ICMPv6NeighborSolicit)
+			ns := header.NDPNeighborSolicit(pkt.MessageBody())
+			ns.SetTargetAddress(nicAddr)
 			opts := ns.Options()
-			copy(opts, test.optsBuf)
-			pkt.SetChecksum(header.ICMPv6Checksum(pkt, lladdr1, lladdr0, buffer.VectorisedView{}))
+			opts.Serialize(test.nsOpts)
+			pkt.SetChecksum(header.ICMPv6Checksum(pkt, test.nsSrc, test.nsDst, buffer.VectorisedView{}))
 			payloadLength := hdr.UsedLength()
 			ip := header.IPv6(hdr.Prepend(header.IPv6MinimumSize))
 			ip.Encode(&header.IPv6Fields{
 				PayloadLength:     uint16(payloadLength),
 				TransportProtocol: header.ICMPv6ProtocolNumber,
 				HopLimit:          255,
-				SrcAddr:           lladdr1,
-				DstAddr:           lladdr0,
+				SrcAddr:           test.nsSrc,
+				DstAddr:           test.nsDst,
 			})
 
 			invalid := s.Stats().ICMP.V6.PacketsReceived.Invalid
@@ -796,44 +495,116 @@ func TestNeighborAdvertisementWithTargetLinkLayerOption(t *testing.T) {
 				t.Fatalf("got invalid = %d, want = 0", got)
 			}
 
-			e.InjectInbound(ProtocolNumber, stack.NewPacketBuffer(stack.PacketBufferOptions{
+			e.InjectLinkAddr(ProtocolNumber, test.nsSrcLinkAddr, stack.NewPacketBuffer(stack.PacketBufferOptions{
 				Data: hdr.View().ToVectorisedView(),
 			}))
 
-			ch := make(chan stack.LinkResolutionResult, 1)
-			err := s.GetLinkAddress(nicID, lladdr1, lladdr0, ProtocolNumber, func(r stack.LinkResolutionResult) {
-				ch <- r
-			})
+			if test.nsInvalid {
+				if got := invalid.Value(); got != 1 {
+					t.Fatalf("got invalid = %d, want = 1", got)
+				}
 
-			wantInvalid := uint64(0)
-			wantSucccess := true
-			if len(test.expectedLinkAddr) == 0 {
-				wantInvalid = 1
-				wantSucccess = false
-				if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
-					t.Errorf("got s.GetLinkAddress(%d, %s, %s, %d, _) = %s, want = %s", nicID, lladdr1, lladdr0, ProtocolNumber, err, &tcpip.ErrWouldBlock{})
+				if p, got := e.Read(); got {
+					t.Fatalf("unexpected response to an invalid NS = %+v", p.Pkt)
 				}
-			} else {
-				if err != nil {
-					t.Errorf("got s.GetLinkAddress(%d, %s, %s, %d, _) = %s, want = nil", nicID, lladdr1, lladdr0, ProtocolNumber, err)
+
+				// If we expected the NS to be invalid, we have nothing else to check.
+				return
+			}
+
+			if got := invalid.Value(); got != 0 {
+				t.Fatalf("got invalid = %d, want = 0", got)
+			}
+
+			if test.performsLinkResolution {
+				p, got := e.ReadContext(context.Background())
+				if !got {
+					t.Fatal("expected an NDP NS response")
+				}
+
+				respNSDst := header.SolicitedNodeAddr(test.nsSrc)
+				var want stack.RouteInfo
+				want.NetProto = ProtocolNumber
+				want.RemoteLinkAddress = header.EthernetAddressFromMulticastIPv6Address(respNSDst)
+				if diff := cmp.Diff(want, p.Route, cmp.AllowUnexported(want)); diff != "" {
+					t.Errorf("route info mismatch (-want +got):\n%s", diff)
+				}
+
+				checker.IPv6(t, stack.PayloadSince(p.Pkt.NetworkHeader()),
+					checker.SrcAddr(nicAddr),
+					checker.DstAddr(respNSDst),
+					checker.TTL(header.NDPHopLimit),
+					checker.NDPNS(
+						checker.NDPNSTargetAddress(test.nsSrc),
+						checker.NDPNSOptions([]header.NDPOption{
+							header.NDPSourceLinkLayerAddressOption(nicLinkAddr),
+						}),
+					))
+
+				ser := header.NDPOptionsSerializer{
+					header.NDPTargetLinkLayerAddressOption(linkAddr1),
 				}
+				ndpNASize := header.ICMPv6NeighborAdvertMinimumSize + ser.Length()
+				hdr := buffer.NewPrependable(header.IPv6MinimumSize + ndpNASize)
+				pkt := header.ICMPv6(hdr.Prepend(ndpNASize))
+				pkt.SetType(header.ICMPv6NeighborAdvert)
+				na := header.NDPNeighborAdvert(pkt.MessageBody())
+				na.SetSolicitedFlag(true)
+				na.SetOverrideFlag(true)
+				na.SetTargetAddress(test.nsSrc)
+				na.Options().Serialize(ser)
+				pkt.SetChecksum(header.ICMPv6Checksum(pkt, test.nsSrc, nicAddr, buffer.VectorisedView{}))
+				payloadLength := hdr.UsedLength()
+				ip := header.IPv6(hdr.Prepend(header.IPv6MinimumSize))
+				ip.Encode(&header.IPv6Fields{
+					PayloadLength:     uint16(payloadLength),
+					TransportProtocol: header.ICMPv6ProtocolNumber,
+					HopLimit:          header.NDPHopLimit,
+					SrcAddr:           test.nsSrc,
+					DstAddr:           nicAddr,
+				})
+				e.InjectLinkAddr(ProtocolNumber, "", stack.NewPacketBuffer(stack.PacketBufferOptions{
+					Data: hdr.View().ToVectorisedView(),
+				}))
 			}
 
-			if diff := cmp.Diff(stack.LinkResolutionResult{LinkAddress: test.expectedLinkAddr, Success: wantSucccess}, <-ch); diff != "" {
-				t.Errorf("linkResolutionResult mismatch (-want +got):\n%s", diff)
+			p, got := e.ReadContext(context.Background())
+			if !got {
+				t.Fatal("expected an NDP NA response")
 			}
-			if got := invalid.Value(); got != wantInvalid {
-				t.Errorf("got invalid = %d, want = %d", got, wantInvalid)
+
+			if p.Route.LocalAddress != test.naSrc {
+				t.Errorf("got p.Route.LocalAddress = %s, want = %s", p.Route.LocalAddress, test.naSrc)
 			}
+			if p.Route.LocalLinkAddress != nicLinkAddr {
+				t.Errorf("p.Route.LocalLinkAddress = %s, want = %s", p.Route.LocalLinkAddress, nicLinkAddr)
+			}
+			if p.Route.RemoteAddress != test.naDst {
+				t.Errorf("got p.Route.RemoteAddress = %s, want = %s", p.Route.RemoteAddress, test.naDst)
+			}
+			if p.Route.RemoteLinkAddress != test.naDstLinkAddr {
+				t.Errorf("got p.Route.RemoteLinkAddress = %s, want = %s", p.Route.RemoteLinkAddress, test.naDstLinkAddr)
+			}
+
+			checker.IPv6(t, stack.PayloadSince(p.Pkt.NetworkHeader()),
+				checker.SrcAddr(test.naSrc),
+				checker.DstAddr(test.naDst),
+				checker.TTL(header.NDPHopLimit),
+				checker.NDPNA(
+					checker.NDPNASolicitedFlag(test.naSolicited),
+					checker.NDPNATargetAddress(nicAddr),
+					checker.NDPNAOptions([]header.NDPOption{
+						header.NDPTargetLinkLayerAddressOption(nicLinkAddr[:]),
+					}),
+				))
 		})
 	}
 }
 
-// TestNeighborAdvertisementWithTargetLinkLayerOptionUsingNeighborCache tests
-// that receiving a valid NDP NA message with the Target Link Layer Address
-// option does not result in a new entry in the neighbor cache for the target
-// of the message.
-func TestNeighborAdvertisementWithTargetLinkLayerOptionUsingNeighborCache(t *testing.T) {
+// TestNeighborAdvertisementWithTargetLinkLayerOption tests that receiving a
+// valid NDP NA message with the Target Link Layer Address option does not
+// result in a new entry in the neighbor cache for the target of the message.
+func TestNeighborAdvertisementWithTargetLinkLayerOption(t *testing.T) {
 	const nicID = 1
 
 	tests := []struct {
@@ -867,7 +638,6 @@ func TestNeighborAdvertisementWithTargetLinkLayerOptionUsingNeighborCache(t *tes
 		t.Run(test.name, func(t *testing.T) {
 			s := stack.New(stack.Options{
 				NetworkProtocols: []stack.NetworkProtocolFactory{NewProtocol},
-				UseNeighborCache: true,
 			})
 			e := channel.New(0, 1280, linkAddr0)
 			e.LinkEPCapabilities |= stack.CapabilityResolutionRequired
@@ -944,235 +714,216 @@ func TestNeighborAdvertisementWithTargetLinkLayerOptionUsingNeighborCache(t *tes
 }
 
 func TestNDPValidation(t *testing.T) {
-	stacks := []struct {
-		name             string
-		useNeighborCache bool
+	setup := func(t *testing.T) (*stack.Stack, stack.NetworkEndpoint) {
+		t.Helper()
+
+		// Create a stack with the assigned link-local address lladdr0
+		// and an endpoint to lladdr1.
+		s, ep := setupStackAndEndpoint(t, lladdr0, lladdr1)
+
+		return s, ep
+	}
+
+	handleIPv6Payload := func(payload buffer.View, hopLimit uint8, atomicFragment bool, ep stack.NetworkEndpoint) {
+		var extHdrs header.IPv6ExtHdrSerializer
+		if atomicFragment {
+			extHdrs = append(extHdrs, &header.IPv6SerializableFragmentExtHdr{})
+		}
+		extHdrsLen := extHdrs.Length()
+
+		ip := buffer.NewView(header.IPv6MinimumSize + extHdrsLen)
+		header.IPv6(ip).Encode(&header.IPv6Fields{
+			PayloadLength:     uint16(len(payload) + extHdrsLen),
+			TransportProtocol: header.ICMPv6ProtocolNumber,
+			HopLimit:          hopLimit,
+			SrcAddr:           lladdr1,
+			DstAddr:           lladdr0,
+			ExtensionHeaders:  extHdrs,
+		})
+		vv := ip.ToVectorisedView()
+		vv.AppendView(payload)
+		ep.HandlePacket(stack.NewPacketBuffer(stack.PacketBufferOptions{
+			Data: vv,
+		}))
+	}
+
+	var tllData [header.NDPLinkLayerAddressSize]byte
+	header.NDPOptions(tllData[:]).Serialize(header.NDPOptionsSerializer{
+		header.NDPTargetLinkLayerAddressOption(linkAddr1),
+	})
+
+	var sllData [header.NDPLinkLayerAddressSize]byte
+	header.NDPOptions(sllData[:]).Serialize(header.NDPOptionsSerializer{
+		header.NDPSourceLinkLayerAddressOption(linkAddr1),
+	})
+
+	types := []struct {
+		name        string
+		typ         header.ICMPv6Type
+		size        int
+		extraData   []byte
+		statCounter func(tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter
+		routerOnly  bool
 	}{
 		{
-			name:             "linkAddrCache",
-			useNeighborCache: false,
+			name: "RouterSolicit",
+			typ:  header.ICMPv6RouterSolicit,
+			size: header.ICMPv6MinimumSize,
+			statCounter: func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
+				return stats.RouterSolicit
+			},
+			routerOnly: true,
 		},
 		{
-			name:             "neighborCache",
-			useNeighborCache: true,
+			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,
+			extraData: sllData[:],
+			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 _, stackTyp := range stacks {
-		t.Run(stackTyp.name, func(t *testing.T) {
-			setup := func(t *testing.T) (*stack.Stack, stack.NetworkEndpoint) {
-				t.Helper()
-
-				// Create a stack with the assigned link-local address lladdr0
-				// and an endpoint to lladdr1.
-				s, ep := setupStackAndEndpoint(t, lladdr0, lladdr1, stackTyp.useNeighborCache)
+	subTests := []struct {
+		name           string
+		atomicFragment bool
+		hopLimit       uint8
+		code           header.ICMPv6Code
+		valid          bool
+	}{
+		{
+			name:           "Valid",
+			atomicFragment: false,
+			hopLimit:       header.NDPHopLimit,
+			code:           0,
+			valid:          true,
+		},
+		{
+			name:           "Fragmented",
+			atomicFragment: true,
+			hopLimit:       header.NDPHopLimit,
+			code:           0,
+			valid:          false,
+		},
+		{
+			name:           "Invalid hop limit",
+			atomicFragment: false,
+			hopLimit:       header.NDPHopLimit - 1,
+			code:           0,
+			valid:          false,
+		},
+		{
+			name:           "Invalid ICMPv6 code",
+			atomicFragment: false,
+			hopLimit:       header.NDPHopLimit,
+			code:           1,
+			valid:          false,
+		},
+	}
 
-				return s, ep
+	for _, typ := range types {
+		for _, isRouter := range []bool{false, true} {
+			name := typ.name
+			if isRouter {
+				name += " (Router)"
 			}
 
-			handleIPv6Payload := func(payload buffer.View, hopLimit uint8, atomicFragment bool, ep stack.NetworkEndpoint) {
-				var extHdrs header.IPv6ExtHdrSerializer
-				if atomicFragment {
-					extHdrs = append(extHdrs, &header.IPv6SerializableFragmentExtHdr{})
-				}
-				extHdrsLen := extHdrs.Length()
+			t.Run(name, func(t *testing.T) {
+				for _, test := range subTests {
+					t.Run(test.name, func(t *testing.T) {
+						s, ep := setup(t)
 
-				ip := buffer.NewView(header.IPv6MinimumSize + extHdrsLen)
-				header.IPv6(ip).Encode(&header.IPv6Fields{
-					PayloadLength:     uint16(len(payload) + extHdrsLen),
-					TransportProtocol: header.ICMPv6ProtocolNumber,
-					HopLimit:          hopLimit,
-					SrcAddr:           lladdr1,
-					DstAddr:           lladdr0,
-					ExtensionHeaders:  extHdrs,
-				})
-				vv := ip.ToVectorisedView()
-				vv.AppendView(payload)
-				ep.HandlePacket(stack.NewPacketBuffer(stack.PacketBufferOptions{
-					Data: vv,
-				}))
-			}
+						if isRouter {
+							// Enabling forwarding makes the stack act as a router.
+							s.SetForwarding(ProtocolNumber, true)
+						}
 
-			var tllData [header.NDPLinkLayerAddressSize]byte
-			header.NDPOptions(tllData[:]).Serialize(header.NDPOptionsSerializer{
-				header.NDPTargetLinkLayerAddressOption(linkAddr1),
-			})
+						stats := s.Stats().ICMP.V6.PacketsReceived
+						invalid := stats.Invalid
+						routerOnly := stats.RouterOnlyPacketsDroppedByHost
+						typStat := typ.statCounter(stats)
 
-			var sllData [header.NDPLinkLayerAddressSize]byte
-			header.NDPOptions(sllData[:]).Serialize(header.NDPOptionsSerializer{
-				header.NDPSourceLinkLayerAddressOption(linkAddr1),
-			})
+						icmp := header.ICMPv6(buffer.NewView(typ.size + len(typ.extraData)))
+						copy(icmp[typ.size:], typ.extraData)
+						icmp.SetType(typ.typ)
+						icmp.SetCode(test.code)
+						icmp.SetChecksum(header.ICMPv6Checksum(icmp[:typ.size], lladdr0, lladdr1, buffer.View(typ.extraData).ToVectorisedView()))
 
-			types := []struct {
-				name        string
-				typ         header.ICMPv6Type
-				size        int
-				extraData   []byte
-				statCounter func(tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter
-				routerOnly  bool
-			}{
-				{
-					name: "RouterSolicit",
-					typ:  header.ICMPv6RouterSolicit,
-					size: header.ICMPv6MinimumSize,
-					statCounter: func(stats tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
-						return stats.RouterSolicit
-					},
-					routerOnly: true,
-				},
-				{
-					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,
-					extraData: sllData[:],
-					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
-					},
-				},
-			}
+						// Rx count of the NDP message should initially be 0.
+						if got := typStat.Value(); got != 0 {
+							t.Errorf("got %s = %d, want = 0", typ.name, got)
+						}
 
-			subTests := []struct {
-				name           string
-				atomicFragment bool
-				hopLimit       uint8
-				code           header.ICMPv6Code
-				valid          bool
-			}{
-				{
-					name:           "Valid",
-					atomicFragment: false,
-					hopLimit:       header.NDPHopLimit,
-					code:           0,
-					valid:          true,
-				},
-				{
-					name:           "Fragmented",
-					atomicFragment: true,
-					hopLimit:       header.NDPHopLimit,
-					code:           0,
-					valid:          false,
-				},
-				{
-					name:           "Invalid hop limit",
-					atomicFragment: false,
-					hopLimit:       header.NDPHopLimit - 1,
-					code:           0,
-					valid:          false,
-				},
-				{
-					name:           "Invalid ICMPv6 code",
-					atomicFragment: false,
-					hopLimit:       header.NDPHopLimit,
-					code:           1,
-					valid:          false,
-				},
-			}
+						// Invalid count should initially be 0.
+						if got := invalid.Value(); got != 0 {
+							t.Errorf("got invalid = %d, want = 0", got)
+						}
 
-			for _, typ := range types {
-				for _, isRouter := range []bool{false, true} {
-					name := typ.name
-					if isRouter {
-						name += " (Router)"
-					}
+						// RouterOnlyPacketsReceivedByHost count should initially be 0.
+						if got := routerOnly.Value(); got != 0 {
+							t.Errorf("got RouterOnlyPacketsReceivedByHost = %d, want = 0", got)
+						}
+
+						if t.Failed() {
+							t.FailNow()
+						}
+
+						handleIPv6Payload(buffer.View(icmp), test.hopLimit, test.atomicFragment, ep)
+
+						// Rx count of the NDP packet should have increased.
+						if got := typStat.Value(); got != 1 {
+							t.Errorf("got %s = %d, want = 1", typ.name, got)
+						}
 
-					t.Run(name, func(t *testing.T) {
-						for _, test := range subTests {
-							t.Run(test.name, func(t *testing.T) {
-								s, ep := setup(t)
-
-								if isRouter {
-									// Enabling forwarding makes the stack act as a router.
-									s.SetForwarding(ProtocolNumber, true)
-								}
-
-								stats := s.Stats().ICMP.V6.PacketsReceived
-								invalid := stats.Invalid
-								routerOnly := stats.RouterOnlyPacketsDroppedByHost
-								typStat := typ.statCounter(stats)
-
-								icmp := header.ICMPv6(buffer.NewView(typ.size + len(typ.extraData)))
-								copy(icmp[typ.size:], typ.extraData)
-								icmp.SetType(typ.typ)
-								icmp.SetCode(test.code)
-								icmp.SetChecksum(header.ICMPv6Checksum(icmp[:typ.size], lladdr0, lladdr1, buffer.View(typ.extraData).ToVectorisedView()))
-
-								// Rx count of the NDP message should initially be 0.
-								if got := typStat.Value(); got != 0 {
-									t.Errorf("got %s = %d, want = 0", typ.name, got)
-								}
-
-								// Invalid count should initially be 0.
-								if got := invalid.Value(); got != 0 {
-									t.Errorf("got invalid = %d, want = 0", got)
-								}
-
-								// RouterOnlyPacketsReceivedByHost count should initially be 0.
-								if got := routerOnly.Value(); got != 0 {
-									t.Errorf("got RouterOnlyPacketsReceivedByHost = %d, want = 0", got)
-								}
-
-								if t.Failed() {
-									t.FailNow()
-								}
-
-								handleIPv6Payload(buffer.View(icmp), test.hopLimit, test.atomicFragment, ep)
-
-								// Rx count of the NDP packet should have increased.
-								if got := typStat.Value(); got != 1 {
-									t.Errorf("got %s = %d, want = 1", typ.name, got)
-								}
-
-								want := uint64(0)
-								if !test.valid {
-									// Invalid count should have increased.
-									want = 1
-								}
-								if got := invalid.Value(); got != want {
-									t.Errorf("got invalid = %d, want = %d", got, want)
-								}
-
-								want = 0
-								if test.valid && !isRouter && typ.routerOnly {
-									// RouterOnlyPacketsReceivedByHost count should have increased.
-									want = 1
-								}
-								if got := routerOnly.Value(); got != want {
-									t.Errorf("got RouterOnlyPacketsReceivedByHost = %d, want = %d", got, want)
-								}
-
-							})
+						want := uint64(0)
+						if !test.valid {
+							// Invalid count should have increased.
+							want = 1
 						}
+						if got := invalid.Value(); got != want {
+							t.Errorf("got invalid = %d, want = %d", got, want)
+						}
+
+						want = 0
+						if test.valid && !isRouter && typ.routerOnly {
+							// RouterOnlyPacketsReceivedByHost count should have increased.
+							want = 1
+						}
+						if got := routerOnly.Value(); got != want {
+							t.Errorf("got RouterOnlyPacketsReceivedByHost = %d, want = %d", got, want)
+						}
+
 					})
 				}
-			}
-		})
+			})
+		}
 	}
-
 }
 
 // TestNeighborAdvertisementValidation tests that the NIC validates received
@@ -1218,7 +969,6 @@ func TestNeighborAdvertisementValidation(t *testing.T) {
 		t.Run(test.name, func(t *testing.T) {
 			s := stack.New(stack.Options{
 				NetworkProtocols: []stack.NetworkProtocolFactory{NewProtocol},
-				UseNeighborCache: true,
 			})
 			e := channel.New(0, header.IPv6MinimumMTU, linkAddr0)
 			e.LinkEPCapabilities |= stack.CapabilityResolutionRequired
@@ -1291,20 +1041,6 @@ func TestNeighborAdvertisementValidation(t *testing.T) {
 // NDP Router Advertisement packets, it validates the Router Advertisement
 // properly before handling them.
 func TestRouterAdvertValidation(t *testing.T) {
-	stacks := []struct {
-		name             string
-		useNeighborCache bool
-	}{
-		{
-			name:             "linkAddrCache",
-			useNeighborCache: false,
-		},
-		{
-			name:             "neighborCache",
-			useNeighborCache: true,
-		},
-	}
-
 	tests := []struct {
 		name            string
 		src             tcpip.Address
@@ -1426,67 +1162,62 @@ func TestRouterAdvertValidation(t *testing.T) {
 		},
 	}
 
-	for _, stackTyp := range stacks {
-		t.Run(stackTyp.name, func(t *testing.T) {
-			for _, test := range tests {
-				t.Run(test.name, func(t *testing.T) {
-					e := channel.New(10, 1280, linkAddr1)
-					e.LinkEPCapabilities |= stack.CapabilityResolutionRequired
-					s := stack.New(stack.Options{
-						NetworkProtocols: []stack.NetworkProtocolFactory{NewProtocol},
-						UseNeighborCache: stackTyp.useNeighborCache,
-					})
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			e := channel.New(10, 1280, linkAddr1)
+			e.LinkEPCapabilities |= stack.CapabilityResolutionRequired
+			s := stack.New(stack.Options{
+				NetworkProtocols: []stack.NetworkProtocolFactory{NewProtocol},
+			})
 
-					if err := s.CreateNIC(1, e); err != nil {
-						t.Fatalf("CreateNIC(_) = %s", err)
-					}
+			if err := s.CreateNIC(1, e); err != nil {
+				t.Fatalf("CreateNIC(_) = %s", err)
+			}
 
-					icmpSize := header.ICMPv6HeaderSize + len(test.ndpPayload)
-					hdr := buffer.NewPrependable(header.IPv6MinimumSize + icmpSize)
-					pkt := header.ICMPv6(hdr.Prepend(icmpSize))
-					pkt.SetType(header.ICMPv6RouterAdvert)
-					pkt.SetCode(test.code)
-					copy(pkt.MessageBody(), test.ndpPayload)
-					payloadLength := hdr.UsedLength()
-					pkt.SetChecksum(header.ICMPv6Checksum(pkt, test.src, header.IPv6AllNodesMulticastAddress, buffer.VectorisedView{}))
-					ip := header.IPv6(hdr.Prepend(header.IPv6MinimumSize))
-					ip.Encode(&header.IPv6Fields{
-						PayloadLength:     uint16(payloadLength),
-						TransportProtocol: icmp.ProtocolNumber6,
-						HopLimit:          test.hopLimit,
-						SrcAddr:           test.src,
-						DstAddr:           header.IPv6AllNodesMulticastAddress,
-					})
+			icmpSize := header.ICMPv6HeaderSize + len(test.ndpPayload)
+			hdr := buffer.NewPrependable(header.IPv6MinimumSize + icmpSize)
+			pkt := header.ICMPv6(hdr.Prepend(icmpSize))
+			pkt.SetType(header.ICMPv6RouterAdvert)
+			pkt.SetCode(test.code)
+			copy(pkt.MessageBody(), test.ndpPayload)
+			payloadLength := hdr.UsedLength()
+			pkt.SetChecksum(header.ICMPv6Checksum(pkt, test.src, header.IPv6AllNodesMulticastAddress, buffer.VectorisedView{}))
+			ip := header.IPv6(hdr.Prepend(header.IPv6MinimumSize))
+			ip.Encode(&header.IPv6Fields{
+				PayloadLength:     uint16(payloadLength),
+				TransportProtocol: icmp.ProtocolNumber6,
+				HopLimit:          test.hopLimit,
+				SrcAddr:           test.src,
+				DstAddr:           header.IPv6AllNodesMulticastAddress,
+			})
 
-					stats := s.Stats().ICMP.V6.PacketsReceived
-					invalid := stats.Invalid
-					rxRA := stats.RouterAdvert
+			stats := s.Stats().ICMP.V6.PacketsReceived
+			invalid := stats.Invalid
+			rxRA := stats.RouterAdvert
 
-					if got := invalid.Value(); got != 0 {
-						t.Fatalf("got invalid = %d, want = 0", got)
-					}
-					if got := rxRA.Value(); got != 0 {
-						t.Fatalf("got rxRA = %d, want = 0", got)
-					}
+			if got := invalid.Value(); got != 0 {
+				t.Fatalf("got invalid = %d, want = 0", got)
+			}
+			if got := rxRA.Value(); got != 0 {
+				t.Fatalf("got rxRA = %d, want = 0", got)
+			}
 
-					e.InjectInbound(header.IPv6ProtocolNumber, stack.NewPacketBuffer(stack.PacketBufferOptions{
-						Data: hdr.View().ToVectorisedView(),
-					}))
+			e.InjectInbound(header.IPv6ProtocolNumber, stack.NewPacketBuffer(stack.PacketBufferOptions{
+				Data: hdr.View().ToVectorisedView(),
+			}))
 
-					if got := rxRA.Value(); got != 1 {
-						t.Fatalf("got rxRA = %d, want = 1", got)
-					}
+			if got := rxRA.Value(); got != 1 {
+				t.Fatalf("got rxRA = %d, want = 1", got)
+			}
 
-					if test.expectedSuccess {
-						if got := invalid.Value(); got != 0 {
-							t.Fatalf("got invalid = %d, want = 0", got)
-						}
-					} else {
-						if got := invalid.Value(); got != 1 {
-							t.Fatalf("got invalid = %d, want = 1", got)
-						}
-					}
-				})
+			if test.expectedSuccess {
+				if got := invalid.Value(); got != 0 {
+					t.Fatalf("got invalid = %d, want = 0", got)
+				}
+			} else {
+				if got := invalid.Value(); got != 1 {
+					t.Fatalf("got invalid = %d, want = 1", got)
+				}
 			}
 		})
 	}