4 files changed, 24 insertions, 13 deletions
diff --git a/pkg/tcpip/network/arp/arp.go b/pkg/tcpip/network/arp/arp.go
index 922181ac0..6b1e854dc 100644
--- a/pkg/tcpip/network/arp/arp.go
+++ b/pkg/tcpip/network/arp/arp.go
@@ -109,7 +109,11 @@ func (e *endpoint) HandlePacket(r *stack.Route, vv buffer.VectorisedView) {
 		copy(pkt.HardwareAddressTarget(), h.HardwareAddressSender())
 		copy(pkt.ProtocolAddressTarget(), h.ProtocolAddressSender())
 		e.linkEP.WritePacket(r, nil /* gso */, hdr, buffer.VectorisedView{}, ProtocolNumber)
+		fallthrough // also fill the cache from requests
 	case header.ARPReply:
+		addr := tcpip.Address(h.ProtocolAddressSender())
+		linkAddr := tcpip.LinkAddress(h.HardwareAddressSender())
+		e.linkAddrCache.AddLinkAddress(e.nicid, addr, linkAddr)
 	}
 }
 
diff --git a/pkg/tcpip/network/ipv6/icmp.go b/pkg/tcpip/network/ipv6/icmp.go
index b5df85455..f543ceb92 100644
--- a/pkg/tcpip/network/ipv6/icmp.go
+++ b/pkg/tcpip/network/ipv6/icmp.go
@@ -121,7 +121,6 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, vv buffer.V
 
 	case header.ICMPv6NeighborSolicit:
 		received.NeighborSolicit.Increment()
-
 		if len(v) < header.ICMPv6NeighborSolicitMinimumSize {
 			received.Invalid.Increment()
 			return
@@ -131,7 +130,6 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, vv buffer.V
 			// We don't have a useful answer; the best we can do is ignore the request.
 			return
 		}
-
 		hdr := buffer.NewPrependable(int(r.MaxHeaderLength()) + header.ICMPv6NeighborAdvertSize)
 		pkt := header.ICMPv6(hdr.Prepend(header.ICMPv6NeighborAdvertSize))
 		pkt.SetType(header.ICMPv6NeighborAdvert)
@@ -154,7 +152,22 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, vv buffer.V
 		r.LocalAddress = targetAddr
 		pkt.SetChecksum(header.ICMPv6Checksum(pkt, r.LocalAddress, r.RemoteAddress, buffer.VectorisedView{}))
 
-		if err := r.WritePacket(nil /* gso */, hdr, buffer.VectorisedView{}, stack.NetworkHeaderParams{Protocol: header.ICMPv6ProtocolNumber, TTL: r.DefaultTTL(), TOS: stack.DefaultTOS}); err != nil {
+		// TODO(tamird/ghanan): there exists an explicit NDP option that is
+		// used to update the neighbor table with link addresses for a
+		// neighbor from an NS (see the Source Link Layer option RFC
+		// 4861 section 4.6.1 and section 7.2.3).
+		//
+		// Furthermore, the entirety of NDP handling here seems to be
+		// contradicted by RFC 4861.
+		e.linkAddrCache.AddLinkAddress(e.nicid, r.RemoteAddress, r.RemoteLinkAddress)
+
+		// RFC 4861 Neighbor Discovery for IP version 6 (IPv6)
+		//
+		// 7.1.2. Validation of Neighbor Advertisements
+		//
+		// The IP Hop Limit field has a value of 255, i.e., the packet
+		// could not possibly have been forwarded by a router.
+		if err := r.WritePacket(nil /* gso */, hdr, buffer.VectorisedView{}, stack.NetworkHeaderParams{Protocol: header.ICMPv6ProtocolNumber, TTL: ndpHopLimit, TOS: stack.DefaultTOS}); err != nil {
 			sent.Dropped.Increment()
 			return
 		}
@@ -178,7 +191,6 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, vv buffer.V
 			received.Invalid.Increment()
 			return
 		}
-
 		vv.TrimFront(header.ICMPv6EchoMinimumSize)
 		hdr := buffer.NewPrependable(int(r.MaxHeaderLength()) + header.ICMPv6EchoMinimumSize)
 		pkt := header.ICMPv6(hdr.Prepend(header.ICMPv6EchoMinimumSize))
diff --git a/pkg/tcpip/stack/nic.go b/pkg/tcpip/stack/nic.go
index 5993fe582..f64bbf6eb 100644
--- a/pkg/tcpip/stack/nic.go
+++ b/pkg/tcpip/stack/nic.go
@@ -632,8 +632,6 @@ func (n *NIC) DeliverNetworkPacket(linkEP LinkEndpoint, remote, _ tcpip.LinkAddr
 
 	src, dst := netProto.ParseAddresses(vv.First())
 
-	n.stack.AddLinkAddress(n.id, src, remote)
-
 	if ref := n.getRef(protocol, dst); ref != nil {
 		handlePacket(protocol, dst, src, linkEP.LinkAddress(), remote, ref, vv)
 		return
diff --git a/pkg/tcpip/tcpip.go b/pkg/tcpip/tcpip.go
index 9d3752032..678a94616 100644
--- a/pkg/tcpip/tcpip.go
+++ b/pkg/tcpip/tcpip.go
@@ -1086,15 +1086,12 @@ func (*TransportEndpointStats) IsEndpointStats() {}
 func fillIn(v reflect.Value) {
 	for i := 0; i < v.NumField(); i++ {
 		v := v.Field(i)
-		switch v.Kind() {
-		case reflect.Ptr:
-			if s := v.Addr().Interface().(**StatCounter); *s == nil {
-				*s = &StatCounter{}
+		if s, ok := v.Addr().Interface().(**StatCounter); ok {
+			if *s == nil {
+				*s = new(StatCounter)
 			}
-		case reflect.Struct:
+		} else {
 			fillIn(v)
-		default:
-			panic(fmt.Sprintf("unexpected type %s", v.Type()))
 		}
 	}
 }