Use different neighbor tables per network endpoint

This stores each protocol's neighbor state separately.

This change also removes the need for each neighbor entry to keep
track of their own link address resolver now that all the entries
in a cache will use the same resolver.

PiperOrigin-RevId: 354818155

2 files changed, 17 insertions, 5 deletions

diff --git a/pkg/tcpip/network/arp/arp.go b/pkg/tcpip/network/arp/arp.go
index 5fd4c5574..0d7fadc31 100644
--- a/pkg/tcpip/network/arp/arp.go
+++ b/pkg/tcpip/network/arp/arp.go
@@ -148,7 +148,13 @@ func (e *endpoint) HandlePacket(pkt *stack.PacketBuffer) {
 		remoteAddr := tcpip.Address(h.ProtocolAddressSender())
 		remoteLinkAddr := tcpip.LinkAddress(h.HardwareAddressSender())
 
-		e.nic.HandleNeighborProbe(remoteAddr, remoteLinkAddr, e)
+		switch err := e.nic.HandleNeighborProbe(header.IPv4ProtocolNumber, remoteAddr, remoteLinkAddr); err.(type) {
+		case nil:
+		case *tcpip.ErrNotSupported:
+			// The stack may support ARP but the NIC may not need link resolution.
+		default:
+			panic(fmt.Sprintf("unexpected error when informing NIC of neighbor probe message: %s", err))
+		}
 
 		respPkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
 			ReserveHeaderBytes: int(e.nic.MaxHeaderLength()) + header.ARPSize,
@@ -190,7 +196,7 @@ func (e *endpoint) HandlePacket(pkt *stack.PacketBuffer) {
 
 		// The solicited, override, and isRouter flags are not available for ARP;
 		// they are only available for IPv6 Neighbor Advertisements.
-		e.nic.HandleNeighborConfirmation(addr, linkAddr, stack.ReachabilityConfirmationFlags{
+		switch err := e.nic.HandleNeighborConfirmation(header.IPv4ProtocolNumber, addr, linkAddr, stack.ReachabilityConfirmationFlags{
 			// Solicited and unsolicited (also referred to as gratuitous) ARP Replies
 			// are handled equivalently to a solicited Neighbor Advertisement.
 			Solicited: true,
@@ -199,7 +205,13 @@ func (e *endpoint) HandlePacket(pkt *stack.PacketBuffer) {
 			Override: false,
 			// ARP does not distinguish between router and non-router hosts.
 			IsRouter: false,
-		})
+		}); err.(type) {
+		case nil:
+		case *tcpip.ErrNotSupported:
+		// The stack may support ARP but the NIC may not need link resolution.
+		default:
+			panic(fmt.Sprintf("unexpected error when informing NIC of neighbor confirmation message: %s", err))
+		}
 	}
 }
 
diff --git a/pkg/tcpip/network/arp/arp_test.go b/pkg/tcpip/network/arp/arp_test.go
index d753a97af..24357e15d 100644
--- a/pkg/tcpip/network/arp/arp_test.go
+++ b/pkg/tcpip/network/arp/arp_test.go
@@ -491,9 +491,9 @@ func TestDirectRequestWithNeighborCache(t *testing.T) {
 				t.Fatal(err)
 			}
 
-			neighbors, err := c.s.Neighbors(nicID)
+			neighbors, err := c.s.Neighbors(nicID, ipv4.ProtocolNumber)
 			if err != nil {
-				t.Fatalf("c.s.Neighbors(%d): %s", nicID, err)
+				t.Fatalf("c.s.Neighbors(%d, %d): %s", nicID, ipv4.ProtocolNumber, err)
 			}
 
 			neighborByAddr := make(map[tcpip.Address]stack.NeighborEntry)