STM32H743ZI2 UDP via Ethernet, jumbo frames

[oguh]

Using H743 ETH example from how-to-create-a-project-for-stm32h7-with-ethernet-and-lwip-stack .

I want to use jumbo frames to avoid IP fragmentation while streaming audio via UDP. So, no jumbo frames have to be received. I only care about transmitting.

Below is my StartDefaultTask function, which is called in main(). Normal transmissions under 1500bytes MTU work fine when MAX_UDP_PAYLOAD_SIZE is adjusted.

I understand work needs to be done. I've tried changing buffer sizes and adjusting values in low_level_init(), but I'm unable to get it to work.

Currently, with ^^ at 2000bytes the debugger ends up here:

void StartDefaultTask(void *argument)
{
  /* init code for LWIP */
  MX_LWIP_Init();
  /* USER CODE BEGIN 5 */
  
  #define MAX_UDP_PAYLOAD_SIZE 2000
  uint8_t large_data[MAX_UDP_PAYLOAD_SIZE];
  const char* message1 = "Hello UDP message!\n\r";

  osDelay(1000);

  ip_addr_t PC_IPADDR;
  IP_ADDR4(&PC_IPADDR, 192, 168, 1, 1);

  struct udp_pcb* my_udp = udp_new();
  udp_connect(my_udp, &PC_IPADDR, 55151);
  struct pbuf* udp_buffer = NULL;

  memset(large_data, 0xAA, MAX_UDP_PAYLOAD_SIZE);

  /* Infinite loop */
  for (;;) {
    osDelay(1000);
    /* !! PBUF_RAM is critical for correct operation !! */
    udp_buffer = pbuf_alloc(PBUF_TRANSPORT, strlen(message1), PBUF_RAM);

    if (udp_buffer != NULL) {
      memcpy(udp_buffer->payload, message1, strlen(message1));
      udp_send(my_udp, udp_buffer);
      pbuf_free(udp_buffer);
    }

    udp_buffer = pbuf_alloc(PBUF_TRANSPORT, MAX_UDP_PAYLOAD_SIZE, PBUF_RAM);

    if (udp_buffer != NULL) {
        // 5. Fill the pbuf payload with the data from our source buffer
        memcpy(udp_buffer->payload, large_data, MAX_UDP_PAYLOAD_SIZE);

        // 6. Send the packet
        udp_send(my_udp, udp_buffer);

        // 7. Free the buffer
        pbuf_free(udp_buffer);
    }

  }
  /* USER CODE END 5 */
}