do not increment ARP connectionID on IP addr update

arp/handler.go

@@ -35,6 +35,14 @@ func (h *Handler) Protocol() uint64 { return uint64(ethernet.TypeARP) }
 
 func (h *Handler) ConnectionID() *uint64 { return &h.connID }
 
+func (h *Handler) UpdateProtoAddr(protoAddr []byte) error {
+	if len(protoAddr) != len(h.ourProtoAddr) {
+		return errors.New("mismatch ARP proto size")
+	}
+	copy(h.ourProtoAddr, protoAddr)
+	return nil
+}
+
 func (h *Handler) Reset(cfg HandlerConfig) error {
 	if len(cfg.HardwareAddr) == 0 || len(cfg.HardwareAddr) > 255 ||
 		len(cfg.ProtocolAddr) == 0 || len(cfg.ProtocolAddr) > 255 {

x/xnet/stack-async.go

@@ -205,7 +205,9 @@ func (s *StackAsync) SetIPAddr(addr netip.Addr) error {
 	if err != nil {
 		return err
 	}
-	return s.resetARP()
+	ip := addr.As4()
+	err = s.arp.UpdateProtoAddr(ip[:])
+	return err
 }
 
 func (s *StackAsync) Addr() netip.Addr {
@@ -456,12 +458,7 @@ func (stack *StackAsync) AssimilateDHCPResults(results *DHCPResults) error {
 	stack.mu.Lock()
 	defer stack.mu.Unlock()
 	if results.AssignedAddr.IsValid() {
-		err := stack.ip.SetAddr(results.AssignedAddr)
-		if err != nil {
-			return err
-		}
-		// Reset ARP handler with new IP address so it can respond to ARP requests.
-		err = stack.resetARP()
+		err := stack.SetIPAddr(results.AssignedAddr)
 		if err != nil {
 			return err
 		}