Do not have a stack-wide linkAddressCache

Link addresses are cached on a per NIC basis so instead of having a
single cache that includes the NIC ID for neighbor entry lookups,
use a single cache per NIC.

PiperOrigin-RevId: 352684111

10 files changed, 85 insertions, 73 deletions

diff --git a/pkg/tcpip/network/arp/arp.go b/pkg/tcpip/network/arp/arp.go
index 1d4d2966e..9255a4f6a 100644
--- a/pkg/tcpip/network/arp/arp.go
+++ b/pkg/tcpip/network/arp/arp.go
@@ -147,7 +147,7 @@ func (e *endpoint) HandlePacket(pkt *stack.PacketBuffer) {
 		remoteLinkAddr := tcpip.LinkAddress(h.HardwareAddressSender())
 
 		if e.nud == nil {
-			e.linkAddrCache.AddLinkAddress(e.nic.ID(), remoteAddr, remoteLinkAddr)
+			e.linkAddrCache.AddLinkAddress(remoteAddr, remoteLinkAddr)
 		} else {
 			e.nud.HandleProbe(remoteAddr, ProtocolNumber, remoteLinkAddr, e.protocol)
 		}
@@ -191,7 +191,7 @@ func (e *endpoint) HandlePacket(pkt *stack.PacketBuffer) {
 		linkAddr := tcpip.LinkAddress(h.HardwareAddressSender())
 
 		if e.nud == nil {
-			e.linkAddrCache.AddLinkAddress(e.nic.ID(), addr, linkAddr)
+			e.linkAddrCache.AddLinkAddress(addr, linkAddr)
 			return
 		}
 
diff --git a/pkg/tcpip/network/ipv6/icmp.go b/pkg/tcpip/network/ipv6/icmp.go
index 47e8aa11a..ae5179d93 100644
--- a/pkg/tcpip/network/ipv6/icmp.go
+++ b/pkg/tcpip/network/ipv6/icmp.go
@@ -290,7 +290,7 @@ func (e *endpoint) handleICMP(pkt *stack.PacketBuffer, hasFragmentHeader bool) {
 		} else if e.nud != nil {
 			e.nud.HandleProbe(srcAddr, header.IPv6ProtocolNumber, sourceLinkAddr, e.protocol)
 		} else {
-			e.linkAddrCache.AddLinkAddress(e.nic.ID(), srcAddr, sourceLinkAddr)
+			e.linkAddrCache.AddLinkAddress(srcAddr, sourceLinkAddr)
 		}
 
 		// As per RFC 4861 section 7.1.1:
@@ -445,7 +445,7 @@ func (e *endpoint) handleICMP(pkt *stack.PacketBuffer, hasFragmentHeader bool) {
 		// address cache with the link address for the target of the message.
 		if e.nud == nil {
 			if len(targetLinkAddr) != 0 {
-				e.linkAddrCache.AddLinkAddress(e.nic.ID(), targetAddr, targetLinkAddr)
+				e.linkAddrCache.AddLinkAddress(targetAddr, targetLinkAddr)
 			}
 			return
 		}
diff --git a/pkg/tcpip/network/ipv6/icmp_test.go b/pkg/tcpip/network/ipv6/icmp_test.go
index a660a1cea..defea46b0 100644
--- a/pkg/tcpip/network/ipv6/icmp_test.go
+++ b/pkg/tcpip/network/ipv6/icmp_test.go
@@ -95,7 +95,7 @@ var _ stack.LinkAddressCache = (*stubLinkAddressCache)(nil)
 
 type stubLinkAddressCache struct{}
 
-func (*stubLinkAddressCache) AddLinkAddress(tcpip.NICID, tcpip.Address, tcpip.LinkAddress) {}
+func (*stubLinkAddressCache) AddLinkAddress(tcpip.Address, tcpip.LinkAddress) {}
 
 type stubNUDHandler struct {
 	probeCount        int
diff --git a/pkg/tcpip/stack/forwarding_test.go b/pkg/tcpip/stack/forwarding_test.go
index 9f2fd8181..d29c9a49b 100644
--- a/pkg/tcpip/stack/forwarding_test.go
+++ b/pkg/tcpip/stack/forwarding_test.go
@@ -368,10 +368,6 @@ func fwdTestNetFactory(t *testing.T, proto *fwdTestNetworkProtocol, useNeighborC
 		UseNeighborCache: useNeighborCache,
 	})
 
-	if !useNeighborCache {
-		proto.addrCache = s.linkAddrCache
-	}
-
 	// Enable forwarding.
 	s.SetForwarding(proto.Number(), true)
 
@@ -401,13 +397,15 @@ func fwdTestNetFactory(t *testing.T, proto *fwdTestNetworkProtocol, useNeighborC
 		t.Fatal("AddAddress #2 failed:", err)
 	}
 
+	nic, ok := s.nics[2]
+	if !ok {
+		t.Fatal("NIC 2 does not exist")
+	}
 	if useNeighborCache {
 		// Control the neighbor cache for NIC 2.
-		nic, ok := s.nics[2]
-		if !ok {
-			t.Fatal("failed to get the neighbor cache for NIC 2")
-		}
 		proto.neigh = nic.neigh
+	} else {
+		proto.addrCache = nic.linkAddrCache
 	}
 
 	// Route all packets to NIC 2.
@@ -493,7 +491,7 @@ func TestForwardingWithFakeResolver(t *testing.T) {
 				addrResolveDelay: 500 * time.Millisecond,
 				onLinkAddressResolved: func(cache *linkAddrCache, neigh *neighborCache, addr tcpip.Address, _ tcpip.LinkAddress) {
 					// Any address will be resolved to the link address "c".
-					cache.add(tcpip.FullAddress{NIC: 2, Addr: addr}, "c")
+					cache.AddLinkAddress(addr, "c")
 				},
 			},
 		},
@@ -619,7 +617,7 @@ func TestForwardingWithFakeResolverPartialTimeout(t *testing.T) {
 					// Only packets to address 3 will be resolved to the
 					// link address "c".
 					if addr == "\x03" {
-						cache.add(tcpip.FullAddress{NIC: 2, Addr: addr}, "c")
+						cache.AddLinkAddress(addr, "c")
 					}
 				},
 			},
@@ -704,7 +702,7 @@ func TestForwardingWithFakeResolverTwoPackets(t *testing.T) {
 				addrResolveDelay: 500 * time.Millisecond,
 				onLinkAddressResolved: func(cache *linkAddrCache, neigh *neighborCache, addr tcpip.Address, _ tcpip.LinkAddress) {
 					// Any packets will be resolved to the link address "c".
-					cache.add(tcpip.FullAddress{NIC: 2, Addr: addr}, "c")
+					cache.AddLinkAddress(addr, "c")
 				},
 			},
 		},
@@ -780,7 +778,7 @@ func TestForwardingWithFakeResolverManyPackets(t *testing.T) {
 				addrResolveDelay: 500 * time.Millisecond,
 				onLinkAddressResolved: func(cache *linkAddrCache, neigh *neighborCache, addr tcpip.Address, _ tcpip.LinkAddress) {
 					// Any packets will be resolved to the link address "c".
-					cache.add(tcpip.FullAddress{NIC: 2, Addr: addr}, "c")
+					cache.AddLinkAddress(addr, "c")
 				},
 			},
 		},
@@ -870,7 +868,7 @@ func TestForwardingWithFakeResolverManyResolutions(t *testing.T) {
 				addrResolveDelay: 500 * time.Millisecond,
 				onLinkAddressResolved: func(cache *linkAddrCache, neigh *neighborCache, addr tcpip.Address, _ tcpip.LinkAddress) {
 					// Any packets will be resolved to the link address "c".
-					cache.add(tcpip.FullAddress{NIC: 2, Addr: addr}, "c")
+					cache.AddLinkAddress(addr, "c")
 				},
 			},
 		},
diff --git a/pkg/tcpip/stack/linkaddrcache.go b/pkg/tcpip/stack/linkaddrcache.go
index b600a1cab..3c4fa341e 100644
--- a/pkg/tcpip/stack/linkaddrcache.go
+++ b/pkg/tcpip/stack/linkaddrcache.go
@@ -24,6 +24,8 @@ import (
 
 const linkAddrCacheSize = 512 // max cache entries
 
+var _ LinkAddressCache = (*linkAddrCache)(nil)
+
 // linkAddrCache is a fixed-sized cache mapping IP addresses to link addresses.
 //
 // The entries are stored in a ring buffer, oldest entry replaced first.
@@ -43,7 +45,7 @@ type linkAddrCache struct {
 
 	cache struct {
 		sync.Mutex
-		table map[tcpip.FullAddress]*linkAddrEntry
+		table map[tcpip.Address]*linkAddrEntry
 		lru   linkAddrEntryList
 	}
 }
@@ -81,7 +83,7 @@ type linkAddrEntry struct {
 	// mu protects the fields below.
 	mu sync.RWMutex
 
-	addr       tcpip.FullAddress
+	addr       tcpip.Address
 	linkAddr   tcpip.LinkAddress
 	expiration time.Time
 	s          entryState
@@ -125,7 +127,7 @@ func (e *linkAddrEntry) changeStateLocked(ns entryState, expiration time.Time) {
 }
 
 // add adds a k -> v mapping to the cache.
-func (c *linkAddrCache) add(k tcpip.FullAddress, v tcpip.LinkAddress) {
+func (c *linkAddrCache) AddLinkAddress(k tcpip.Address, v tcpip.LinkAddress) {
 	// Calculate expiration time before acquiring the lock, since expiration is
 	// relative to the time when information was learned, rather than when it
 	// happened to be inserted into the cache.
@@ -150,7 +152,7 @@ func (c *linkAddrCache) add(k tcpip.FullAddress, v tcpip.LinkAddress) {
 // reset to state incomplete, and returned. If no matching entry exists and the
 // cache is not full, a new entry with state incomplete is allocated and
 // returned.
-func (c *linkAddrCache) getOrCreateEntryLocked(k tcpip.FullAddress) *linkAddrEntry {
+func (c *linkAddrCache) getOrCreateEntryLocked(k tcpip.Address) *linkAddrEntry {
 	if entry, ok := c.cache.table[k]; ok {
 		c.cache.lru.Remove(entry)
 		c.cache.lru.PushFront(entry)
@@ -181,7 +183,7 @@ func (c *linkAddrCache) getOrCreateEntryLocked(k tcpip.FullAddress) *linkAddrEnt
 }
 
 // get reports any known link address for k.
-func (c *linkAddrCache) get(k tcpip.FullAddress, linkRes LinkAddressResolver, localAddr tcpip.Address, nic NetworkInterface, onResolve func(tcpip.LinkAddress, bool)) (tcpip.LinkAddress, <-chan struct{}, *tcpip.Error) {
+func (c *linkAddrCache) get(k tcpip.Address, linkRes LinkAddressResolver, localAddr tcpip.Address, nic NetworkInterface, onResolve func(tcpip.LinkAddress, bool)) (tcpip.LinkAddress, <-chan struct{}, *tcpip.Error) {
 	c.cache.Lock()
 	defer c.cache.Unlock()
 	entry := c.getOrCreateEntryLocked(k)
@@ -214,11 +216,11 @@ func (c *linkAddrCache) get(k tcpip.FullAddress, linkRes LinkAddressResolver, lo
 	}
 }
 
-func (c *linkAddrCache) startAddressResolution(k tcpip.FullAddress, linkRes LinkAddressResolver, localAddr tcpip.Address, nic NetworkInterface, done <-chan struct{}) {
+func (c *linkAddrCache) startAddressResolution(k tcpip.Address, linkRes LinkAddressResolver, localAddr tcpip.Address, nic NetworkInterface, done <-chan struct{}) {
 	for i := 0; ; i++ {
 		// Send link request, then wait for the timeout limit and check
 		// whether the request succeeded.
-		linkRes.LinkAddressRequest(k.Addr, localAddr, "" /* linkAddr */, nic)
+		linkRes.LinkAddressRequest(k, localAddr, "" /* linkAddr */, nic)
 
 		select {
 		case now := <-time.After(c.resolutionTimeout):
@@ -234,7 +236,7 @@ func (c *linkAddrCache) startAddressResolution(k tcpip.FullAddress, linkRes Link
 // checkLinkRequest checks whether previous attempt to resolve address has
 // succeeded and mark the entry accordingly. Returns true if request can stop,
 // false if another request should be sent.
-func (c *linkAddrCache) checkLinkRequest(now time.Time, k tcpip.FullAddress, attempt int) bool {
+func (c *linkAddrCache) checkLinkRequest(now time.Time, k tcpip.Address, attempt int) bool {
 	c.cache.Lock()
 	defer c.cache.Unlock()
 	entry, ok := c.cache.table[k]
@@ -268,6 +270,6 @@ func newLinkAddrCache(ageLimit, resolutionTimeout time.Duration, resolutionAttem
 		resolutionTimeout:  resolutionTimeout,
 		resolutionAttempts: resolutionAttempts,
 	}
-	c.cache.table = make(map[tcpip.FullAddress]*linkAddrEntry, linkAddrCacheSize)
+	c.cache.table = make(map[tcpip.Address]*linkAddrEntry, linkAddrCacheSize)
 	return c
 }
diff --git a/pkg/tcpip/stack/linkaddrcache_test.go b/pkg/tcpip/stack/linkaddrcache_test.go
index d7ac6cf5f..8c35067c6 100644
--- a/pkg/tcpip/stack/linkaddrcache_test.go
+++ b/pkg/tcpip/stack/linkaddrcache_test.go
@@ -26,7 +26,7 @@ import (
 )
 
 type testaddr struct {
-	addr     tcpip.FullAddress
+	addr     tcpip.Address
 	linkAddr tcpip.LinkAddress
 }
 
@@ -35,7 +35,7 @@ var testAddrs = func() []testaddr {
 	for i := 0; i < 4*linkAddrCacheSize; i++ {
 		addr := fmt.Sprintf("Addr%06d", i)
 		addrs = append(addrs, testaddr{
-			addr:     tcpip.FullAddress{NIC: 1, Addr: tcpip.Address(addr)},
+			addr:     tcpip.Address(addr),
 			linkAddr: tcpip.LinkAddress("Link" + addr),
 		})
 	}
@@ -59,8 +59,8 @@ func (r *testLinkAddressResolver) LinkAddressRequest(targetAddr, _ tcpip.Address
 
 func (r *testLinkAddressResolver) fakeRequest(addr tcpip.Address) {
 	for _, ta := range testAddrs {
-		if ta.addr.Addr == addr {
-			r.cache.add(ta.addr, ta.linkAddr)
+		if ta.addr == addr {
+			r.cache.AddLinkAddress(ta.addr, ta.linkAddr)
 			break
 		}
 	}
@@ -77,7 +77,7 @@ func (*testLinkAddressResolver) LinkAddressProtocol() tcpip.NetworkProtocolNumbe
 	return 1
 }
 
-func getBlocking(c *linkAddrCache, addr tcpip.FullAddress, linkRes LinkAddressResolver) (tcpip.LinkAddress, *tcpip.Error) {
+func getBlocking(c *linkAddrCache, addr tcpip.Address, linkRes LinkAddressResolver) (tcpip.LinkAddress, *tcpip.Error) {
 	var attemptedResolution bool
 	for {
 		got, ch, err := c.get(addr, linkRes, "", nil, nil)
@@ -97,13 +97,13 @@ func TestCacheOverflow(t *testing.T) {
 	c := newLinkAddrCache(1<<63-1, 1*time.Second, 3)
 	for i := len(testAddrs) - 1; i >= 0; i-- {
 		e := testAddrs[i]
-		c.add(e.addr, e.linkAddr)
+		c.AddLinkAddress(e.addr, e.linkAddr)
 		got, _, err := c.get(e.addr, nil, "", nil, nil)
 		if err != nil {
-			t.Errorf("insert %d, c.get(%q)=%q, got error: %v", i, string(e.addr.Addr), got, err)
+			t.Errorf("insert %d, c.get(%s, nil, '', nil, nil): %s", i, e.addr, err)
 		}
 		if got != e.linkAddr {
-			t.Errorf("insert %d, c.get(%q)=%q, want %q", i, string(e.addr.Addr), got, e.linkAddr)
+			t.Errorf("insert %d, got c.get(%s, nil, '', nil, nil) = %s, want = %s", i, e.addr, got, e.linkAddr)
 		}
 	}
 	// Expect to find at least half of the most recent entries.
@@ -111,10 +111,10 @@ func TestCacheOverflow(t *testing.T) {
 		e := testAddrs[i]
 		got, _, err := c.get(e.addr, nil, "", nil, nil)
 		if err != nil {
-			t.Errorf("check %d, c.get(%q)=%q, got error: %v", i, string(e.addr.Addr), got, err)
+			t.Errorf("check %d, c.get(%s, nil, '', nil, nil): %s", i, e.addr, err)
 		}
 		if got != e.linkAddr {
-			t.Errorf("check %d, c.get(%q)=%q, want %q", i, string(e.addr.Addr), got, e.linkAddr)
+			t.Errorf("check %d, got c.get(%s, nil, '', nil, nil) = %s, want = %s", i, e.addr, got, e.linkAddr)
 		}
 	}
 	// The earliest entries should no longer be in the cache.
@@ -123,7 +123,7 @@ func TestCacheOverflow(t *testing.T) {
 	for i := len(testAddrs) - 1; i >= len(testAddrs)-linkAddrCacheSize; i-- {
 		e := testAddrs[i]
 		if entry, ok := c.cache.table[e.addr]; ok {
-			t.Errorf("unexpected entry at c.cache.table[%q]: %#v", string(e.addr.Addr), entry)
+			t.Errorf("unexpected entry at c.cache.table[%s]: %#v", e.addr, entry)
 		}
 	}
 }
@@ -137,7 +137,7 @@ func TestCacheConcurrent(t *testing.T) {
 		wg.Add(1)
 		go func() {
 			for _, e := range testAddrs {
-				c.add(e.addr, e.linkAddr)
+				c.AddLinkAddress(e.addr, e.linkAddr)
 			}
 			wg.Done()
 		}()
@@ -150,17 +150,17 @@ func TestCacheConcurrent(t *testing.T) {
 	e := testAddrs[len(testAddrs)-1]
 	got, _, err := c.get(e.addr, linkRes, "", nil, nil)
 	if err != nil {
-		t.Errorf("c.get(%q)=%q, got error: %v", string(e.addr.Addr), got, err)
+		t.Errorf("c.get(%s, _, '', nil, nil): %s", e.addr, err)
 	}
 	if got != e.linkAddr {
-		t.Errorf("c.get(%q)=%q, want %q", string(e.addr.Addr), got, e.linkAddr)
+		t.Errorf("got c.get(%s, _, '', nil, nil) = %s, want = %s", e.addr, got, e.linkAddr)
 	}
 
 	e = testAddrs[0]
 	c.cache.Lock()
 	defer c.cache.Unlock()
 	if entry, ok := c.cache.table[e.addr]; ok {
-		t.Errorf("unexpected entry at c.cache.table[%q]: %#v", string(e.addr.Addr), entry)
+		t.Errorf("unexpected entry at c.cache.table[%s]: %#v", e.addr, entry)
 	}
 }
 
@@ -169,10 +169,10 @@ func TestCacheAgeLimit(t *testing.T) {
 	linkRes := &testLinkAddressResolver{cache: c}
 
 	e := testAddrs[0]
-	c.add(e.addr, e.linkAddr)
+	c.AddLinkAddress(e.addr, e.linkAddr)
 	time.Sleep(50 * time.Millisecond)
 	if _, _, err := c.get(e.addr, linkRes, "", nil, nil); err != tcpip.ErrWouldBlock {
-		t.Errorf("got c.get(%q) = %s, want = ErrWouldBlock", string(e.addr.Addr), err)
+		t.Errorf("got c.get(%s, _, '', nil, nil) = %s, want = ErrWouldBlock", e.addr, err)
 	}
 }
 
@@ -180,22 +180,22 @@ func TestCacheReplace(t *testing.T) {
 	c := newLinkAddrCache(1<<63-1, 1*time.Second, 3)
 	e := testAddrs[0]
 	l2 := e.linkAddr + "2"
-	c.add(e.addr, e.linkAddr)
+	c.AddLinkAddress(e.addr, e.linkAddr)
 	got, _, err := c.get(e.addr, nil, "", nil, nil)
 	if err != nil {
-		t.Errorf("c.get(%q)=%q, got error: %v", string(e.addr.Addr), got, err)
+		t.Errorf("c.get(%s, nil, '', nil, nil): %s", e.addr, err)
 	}
 	if got != e.linkAddr {
-		t.Errorf("c.get(%q)=%q, want %q", string(e.addr.Addr), got, e.linkAddr)
+		t.Errorf("got c.get(%s, nil, '', nil, nil) = %s, want = %s", e.addr, got, e.linkAddr)
 	}
 
-	c.add(e.addr, l2)
+	c.AddLinkAddress(e.addr, l2)
 	got, _, err = c.get(e.addr, nil, "", nil, nil)
 	if err != nil {
-		t.Errorf("c.get(%q)=%q, got error: %v", string(e.addr.Addr), got, err)
+		t.Errorf("c.get(%s, nil, '', nil, nil): %s", e.addr, err)
 	}
 	if got != l2 {
-		t.Errorf("c.get(%q)=%q, want %q", string(e.addr.Addr), got, l2)
+		t.Errorf("got c.get(%s, nil, '', nil, nil) = %s, want = %s", e.addr, got, l2)
 	}
 }
 
@@ -211,10 +211,10 @@ func TestCacheResolution(t *testing.T) {
 	for i, ta := range testAddrs {
 		got, err := getBlocking(c, ta.addr, linkRes)
 		if err != nil {
-			t.Errorf("check %d, c.get(%q)=%q, got error: %v", i, string(ta.addr.Addr), got, err)
+			t.Errorf("check %d, getBlocking(_, %s, _): %s", i, ta.addr, err)
 		}
 		if got != ta.linkAddr {
-			t.Errorf("check %d, c.get(%q)=%q, want %q", i, string(ta.addr.Addr), got, ta.linkAddr)
+			t.Errorf("check %d, got getBlocking(_, %s, _) = %s, want = %s", i, ta.addr, got, ta.linkAddr)
 		}
 	}
 
@@ -223,10 +223,10 @@ func TestCacheResolution(t *testing.T) {
 		e := testAddrs[len(testAddrs)-1]
 		got, _, err := c.get(e.addr, linkRes, "", nil, nil)
 		if err != nil {
-			t.Errorf("c.get(%q)=%q, got error: %v", string(e.addr.Addr), got, err)
+			t.Errorf("c.get(%s, _, '', nil, nil): %s", e.addr, err)
 		}
 		if got != e.linkAddr {
-			t.Errorf("c.get(%q)=%q, want %q", string(e.addr.Addr), got, e.linkAddr)
+			t.Errorf("got c.get(%s, _, '', nil, nil) = %s, want = %s", e.addr, got, e.linkAddr)
 		}
 	}
 }
@@ -244,17 +244,17 @@ func TestCacheResolutionFailed(t *testing.T) {
 	e := testAddrs[0]
 	got, err := getBlocking(c, e.addr, linkRes)
 	if err != nil {
-		t.Errorf("c.get(%q)=%q, got error: %v", string(e.addr.Addr), got, err)
+		t.Errorf("getBlocking(_, %s, _): %s", e.addr, err)
 	}
 	if got != e.linkAddr {
-		t.Errorf("c.get(%q)=%q, want %q", string(e.addr.Addr), got, e.linkAddr)
+		t.Errorf("got getBlocking(_, %s, _) = %s, want = %s", e.addr, got, e.linkAddr)
 	}
 
 	before := atomic.LoadUint32(&requestCount)
 
-	e.addr.Addr += "2"
+	e.addr += "2"
 	if a, err := getBlocking(c, e.addr, linkRes); err != tcpip.ErrTimeout {
-		t.Errorf("got getBlocking(_, %#v, _) = (%s, %s), want = (_, %s)", e.addr, a, err, tcpip.ErrTimeout)
+		t.Errorf("got getBlocking(_, %s, _) = (%s, %s), want = (_, %s)", e.addr, a, err, tcpip.ErrTimeout)
 	}
 
 	if got, want := int(atomic.LoadUint32(&requestCount)-before), c.resolutionAttempts; got != want {
@@ -270,6 +270,6 @@ func TestCacheResolutionTimeout(t *testing.T) {
 
 	e := testAddrs[0]
 	if a, err := getBlocking(c, e.addr, linkRes); err != tcpip.ErrTimeout {
-		t.Errorf("got getBlocking(_, %#v, _) = (%s, %s), want = (_, %s)", e.addr, a, err, tcpip.ErrTimeout)
+		t.Errorf("got getBlocking(_, %s, _) = (%s, %s), want = (_, %s)", e.addr, a, err, tcpip.ErrTimeout)
 	}
 }
diff --git a/pkg/tcpip/stack/ndp_test.go b/pkg/tcpip/stack/ndp_test.go
index 61636cae5..270f5fb1a 100644
--- a/pkg/tcpip/stack/ndp_test.go
+++ b/pkg/tcpip/stack/ndp_test.go
@@ -2808,6 +2808,7 @@ func stackAndNdpDispatcherWithDefaultRoute(t *testing.T, nicID tcpip.NICID, useN
 		autoGenAddrC: make(chan ndpAutoGenAddrEvent, 1),
 	}
 	e := channel.New(0, 1280, linkAddr1)
+	e.LinkEPCapabilities |= stack.CapabilityResolutionRequired
 	s := stack.New(stack.Options{
 		NetworkProtocols: []stack.NetworkProtocolFactory{ipv6.NewProtocolWithOptions(ipv6.Options{
 			NDPConfigs: ipv6.NDPConfigurations{
@@ -2827,10 +2828,15 @@ func stackAndNdpDispatcherWithDefaultRoute(t *testing.T, nicID tcpip.NICID, useN
 		Gateway:     llAddr3,
 		NIC:         nicID,
 	}})
+
 	if useNeighborCache {
-		s.AddStaticNeighbor(nicID, llAddr3, linkAddr3)
+		if err := s.AddStaticNeighbor(nicID, llAddr3, linkAddr3); err != nil {
+			t.Fatalf("s.AddStaticNeighbor(%d, %s, %s): %s", nicID, llAddr3, linkAddr3, err)
+		}
 	} else {
-		s.AddLinkAddress(nicID, llAddr3, linkAddr3)
+		if err := s.AddLinkAddress(nicID, llAddr3, linkAddr3); err != nil {
+			t.Fatalf("s.AddLinkAddress(%d, %s, %s): %s", nicID, llAddr3, linkAddr3, err)
+		}
 	}
 	return ndpDisp, e, s
 }
diff --git a/pkg/tcpip/stack/nic.go b/pkg/tcpip/stack/nic.go
index 0f545f255..f2bca93d3 100644
--- a/pkg/tcpip/stack/nic.go
+++ b/pkg/tcpip/stack/nic.go
@@ -53,6 +53,8 @@ type NIC struct {
 	// complete.
 	linkResQueue packetsPendingLinkResolution
 
+	linkAddrCache *linkAddrCache
+
 	mu struct {
 		sync.RWMutex
 		spoofing    bool
@@ -137,6 +139,7 @@ func newNIC(stack *Stack, id tcpip.NICID, name string, ep LinkEndpoint, ctx NICC
 		context:          ctx,
 		stats:            makeNICStats(),
 		networkEndpoints: make(map[tcpip.NetworkProtocolNumber]NetworkEndpoint),
+		linkAddrCache:    newLinkAddrCache(ageLimit, resolutionTimeout, resolutionAttempts),
 	}
 	nic.linkResQueue.init()
 	nic.mu.packetEPs = make(map[tcpip.NetworkProtocolNumber]*packetEndpointList)
@@ -167,7 +170,7 @@ func newNIC(stack *Stack, id tcpip.NICID, name string, ep LinkEndpoint, ctx NICC
 	for _, netProto := range stack.networkProtocols {
 		netNum := netProto.Number()
 		nic.mu.packetEPs[netNum] = new(packetEndpointList)
-		nic.networkEndpoints[netNum] = netProto.NewEndpoint(nic, stack, nud, nic)
+		nic.networkEndpoints[netNum] = netProto.NewEndpoint(nic, nic.linkAddrCache, nud, nic)
 	}
 
 	nic.LinkEndpoint.Attach(nic)
@@ -558,7 +561,7 @@ func (n *NIC) getNeighborLinkAddress(addr, localAddr tcpip.Address, linkRes Link
 		return entry.LinkAddr, ch, err
 	}
 
-	return n.stack.linkAddrCache.get(tcpip.FullAddress{NIC: n.ID(), Addr: addr}, linkRes, localAddr, n, onResolve)
+	return n.linkAddrCache.get(addr, linkRes, localAddr, n, onResolve)
 }
 
 func (n *NIC) neighbors() ([]NeighborEntry, *tcpip.Error) {
diff --git a/pkg/tcpip/stack/registration.go b/pkg/tcpip/stack/registration.go
index 34c122728..33df192aa 100644
--- a/pkg/tcpip/stack/registration.go
+++ b/pkg/tcpip/stack/registration.go
@@ -850,7 +850,7 @@ type LinkAddressResolver interface {
 // A LinkAddressCache caches link addresses.
 type LinkAddressCache interface {
 	// AddLinkAddress adds a link address to the cache.
-	AddLinkAddress(nicID tcpip.NICID, addr tcpip.Address, linkAddr tcpip.LinkAddress)
+	AddLinkAddress(addr tcpip.Address, linkAddr tcpip.LinkAddress)
 }
 
 // RawFactory produces endpoints for writing various types of raw packets.
diff --git a/pkg/tcpip/stack/stack.go b/pkg/tcpip/stack/stack.go
index b4878669c..4685fa4cf 100644
--- a/pkg/tcpip/stack/stack.go
+++ b/pkg/tcpip/stack/stack.go
@@ -382,8 +382,6 @@ type Stack struct {
 
 	stats tcpip.Stats
 
-	linkAddrCache *linkAddrCache
-
 	mu   sync.RWMutex
 	nics map[tcpip.NICID]*NIC
 
@@ -636,7 +634,6 @@ func New(opts Options) *Stack {
 		linkAddrResolvers:  make(map[tcpip.NetworkProtocolNumber]LinkAddressResolver),
 		nics:               make(map[tcpip.NICID]*NIC),
 		cleanupEndpoints:   make(map[TransportEndpoint]struct{}),
-		linkAddrCache:      newLinkAddrCache(ageLimit, resolutionTimeout, resolutionAttempts),
 		PortManager:        ports.NewPortManager(),
 		clock:              clock,
 		stats:              opts.Stats.FillIn(),
@@ -1516,12 +1513,18 @@ func (s *Stack) SetSpoofing(nicID tcpip.NICID, enable bool) *tcpip.Error {
 	return nil
 }
 
-// AddLinkAddress adds a link address to the stack link cache.
-func (s *Stack) AddLinkAddress(nicID tcpip.NICID, addr tcpip.Address, linkAddr tcpip.LinkAddress) {
-	fullAddr := tcpip.FullAddress{NIC: nicID, Addr: addr}
-	s.linkAddrCache.add(fullAddr, linkAddr)
-	// TODO: provide a way for a transport endpoint to receive a signal
-	// that AddLinkAddress for a particular address has been called.
+// AddLinkAddress adds a link address for the neighbor on the specified NIC.
+func (s *Stack) AddLinkAddress(nicID tcpip.NICID, neighbor tcpip.Address, linkAddr tcpip.LinkAddress) *tcpip.Error {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	nic, ok := s.nics[nicID]
+	if !ok {
+		return tcpip.ErrUnknownNICID
+	}
+
+	nic.linkAddrCache.AddLinkAddress(neighbor, linkAddr)
+	return nil
 }
 
 // GetLinkAddress finds the link address corresponding to a neighbor's address.