Remove ARP address workaround

- Make AddressableEndpoint optional for NetworkEndpoint.
Not all NetworkEndpoints need to support addressing (e.g. ARP), so
AddressableEndpoint should only be implemented for protocols that
support addressing such as IPv4 and IPv6.

With this change, tcpip.ErrNotSupported will be returned by the stack
when attempting to modify addresses on a network endpoint that does
not support addressing.

Now that packets are fully handled at the network layer, and (with this
change) addresses are optional for network endpoints, we no longer need
the workaround for ARP where a fake ARP address was added to each NIC
that performs ARP so that packets would be delivered to the ARP layer.

PiperOrigin-RevId: 342722547

2 files changed, 24 insertions, 8 deletions

diff --git a/pkg/tcpip/network/ipv6/icmp_test.go b/pkg/tcpip/network/ipv6/icmp_test.go
index 001b9d66a..9bc02d851 100644
--- a/pkg/tcpip/network/ipv6/icmp_test.go
+++ b/pkg/tcpip/network/ipv6/icmp_test.go
@@ -205,9 +205,13 @@ func TestICMPCounts(t *testing.T) {
 				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 := ep.AddAndAcquirePermanentAddress(addr, stack.CanBePrimaryEndpoint, stack.AddressConfigStatic, false /* deprecated */); err != nil {
-				t.Fatalf("ep.AddAndAcquirePermanentAddress(%s, CanBePrimaryEndpoint, AddressConfigStatic, false): %s", addr, err)
+			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()
 			}
@@ -343,9 +347,13 @@ func TestICMPCountsWithNeighborCache(t *testing.T) {
 		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 := ep.AddAndAcquirePermanentAddress(addr, stack.CanBePrimaryEndpoint, stack.AddressConfigStatic, false /* deprecated */); err != nil {
-		t.Fatalf("ep.AddAndAcquirePermanentAddress(%s, CanBePrimaryEndpoint, AddressConfigStatic, false): %s", addr, err)
+	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()
 	}
@@ -1769,9 +1777,13 @@ func TestCallsToNeighborCache(t *testing.T) {
 				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 := ep.AddAndAcquirePermanentAddress(addr, stack.CanBePrimaryEndpoint, stack.AddressConfigStatic, false /* deprecated */); err != nil {
-				t.Fatalf("ep.AddAndAcquirePermanentAddress(%s, CanBePrimaryEndpoint, AddressConfigStatic, false): %s", addr, err)
+			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()
 			}
diff --git a/pkg/tcpip/network/ipv6/ndp_test.go b/pkg/tcpip/network/ipv6/ndp_test.go
index be83e9eb4..37e8b1083 100644
--- a/pkg/tcpip/network/ipv6/ndp_test.go
+++ b/pkg/tcpip/network/ipv6/ndp_test.go
@@ -69,9 +69,13 @@ func setupStackAndEndpoint(t *testing.T, llladdr, rlladdr tcpip.Address, useNeig
 	}
 	t.Cleanup(ep.Close)
 
+	addressableEndpoint, ok := ep.(stack.AddressableEndpoint)
+	if !ok {
+		t.Fatalf("expected network endpoint to implement stack.AddressableEndpoint")
+	}
 	addr := llladdr.WithPrefix()
-	if addressEP, err := ep.AddAndAcquirePermanentAddress(addr, stack.CanBePrimaryEndpoint, stack.AddressConfigStatic, false /* deprecated */); err != nil {
-		t.Fatalf("ep.AddAndAcquirePermanentAddress(%s, CanBePrimaryEndpoint, AddressConfigStatic, false): %s", addr, err)
+	if addressEP, err := addressableEndpoint.AddAndAcquirePermanentAddress(addr, stack.CanBePrimaryEndpoint, stack.AddressConfigStatic, false /* deprecated */); err != nil {
+		t.Fatalf("addressableEndpoint.AddAndAcquirePermanentAddress(%s, CanBePrimaryEndpoint, AddressConfigStatic, false): %s", addr, err)
 	} else {
 		addressEP.DecRef()
 	}