code: func (*protocol) LinkAddressRequest(addr, localAddr tcpip.Address, linkEP stack.LinkEndpoint) *tcpip.Error {
  	r := &stack.Route{
  		RemoteLinkAddress: broadcastMAC,
  	}
  
  	hdr := buffer.NewPrependable(int(linkEP.MaxHeaderLength()) + header.ARPSize)
  	h := header.ARP(hdr.Prepend(header.ARPSize))
  	h.SetIPv4OverEthernet()
  	h.SetOp(header.ARPRequest)
  	copy(h.HardwareAddressSender(), linkEP.LinkAddress())
  	copy(h.ProtocolAddressSender(), localAddr)
  	copy(h.ProtocolAddressTarget(), addr)
  
  	return linkEP.WritePacket(r, nil /* gso */, hdr, buffer.VectorisedView{}, ProtocolNumber)
  }
docs: // LinkAddressRequest implements stack.LinkAddressResolver.