problems with IP in sending UDP packets

[Andyroc]

Spent several hours and still can't find how to do it. I can not send UDP to a custom IP address, only to the one with which a connection is established. Maybe there is some kind of filter that does not allow this, or somewhere I can change the destination IP manually in udp packet?

[JAndrassy]

try the github version.

[Andyroc]

I solved my problem, by disabling this part in uip_arp.c

if(i == UIP_ARPTAB_SIZE)
 {
    memset(BUF->ethhdr.dest.addr, 0xff, 6);
      memset(BUF->dhwaddr.addr, 0x00, 6);
      memcpy(BUF->ethhdr.src.addr, uip_ethaddr.addr, 6);
      memcpy(BUF->shwaddr.addr, uip_ethaddr.addr, 6);
    
      uip_ipaddr_copy(BUF->dipaddr, ipaddr);
      uip_ipaddr_copy(BUF->sipaddr, uip_hostaddr);
      BUF->opcode = HTONS(ARP_REQUEST); //// ARP request. 
      BUF->hwtype = HTONS(ARP_HWTYPE_ETH);
      BUF->protocol = HTONS(UIP_ETHTYPE_IP);
      BUF->hwlen = 6;
      BUF->protolen = 4;
      BUF->ethhdr.type = HTONS(UIP_ETHTYPE_ARP);

      uip_appdata = &uip_buf[UIP_TCPIP_HLEN + UIP_LLH_LEN];
    
      uip_len = sizeof(struct arp_hdr);
      return;
    }

[JAndrassy]

there is a less invasive way for this patch, I think.
instead of removing code in uip_arp.c remove the line uip_arp_out() from UIPUDP::_send in EthernertUdp.cpp

I already looked at this and I have to investigate it to understand why the switch from normal packet to arp packet is done differently for UDP than TCP