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Re: [lwip-users] TCP Retransmission when receiving consecutive packets

From: Julien Jemine
Subject: Re: [lwip-users] TCP Retransmission when receiving consecutive packets
Date: Fri, 21 Mar 2014 09:39:17 +0100

Hi Jens, hi Sergio,

Yes that's exactly my problem. Here's the patch I've came up with on my driver :

int packetCount = 0;

static void eth_notify (ARM_ETH_MAC_EVENT event) {
  /* Send notification on RX event */
  if (event == ARM_ETH_MAC_EVENT_RX_FRAME) {

void ethernetif_poll (struct netif *netif) {
  struct ethernetif *eth = netif->state;

  if (!eth->phy_ok || eth->link == ARM_ETH_LINK_DOWN) {
  while (packetCount)
    ethernetif_input (netif);

It works perfectly !

Thanks a lot for your help !


2014-03-20 19:46 GMT+01:00 Jens Nielsen <address@hidden>:
Alright, I also use the ST drivers (the ones from STM32Cube 1.0.0) on an STM32F4

I haven't verified that my fix is 100% accurate but I think it looks safe so I'm sending it to ST anyway so they can figure it out if they want to.

My fix goes something like this:

At the bottom of HAL_ETH_GetReceivedFrame_IT() I return an error code if I don't find a complete packet:

--- a/clients/embedded/source/STM32F4XX/STM32F4xx_HAL_Driver/Src/stm32f4xx_hal_eth.c
+++ b/clients/embedded/source/STM32F4XX/STM32F4xx_HAL_Driver/Src/stm32f4xx_hal_eth.c
@@ -868,7 +868,7 @@ HAL_StatusTypeDef HAL_ETH_GetReceivedFrame_IT(ETH_HandleTypeDef *heth)

   /* Return function status */
-  return HAL_OK;
+  return HAL_ERROR;


And then return NULL from low_level_input() in my ethernetif:

--- a/clients/embedded/source/lwip-1.4.1/port/STM32F4x7/FreeRTOS/ethernetif.c
+++ b/clients/embedded/source/lwip-1.4.1/port/STM32F4x7/FreeRTOS/ethernetif.c
@@ -225,7 +224,10 @@ static struct pbuf * low_level_input(struct netif *netif)
   uint32_t i=0;

   /* get received frame */
-  HAL_ETH_GetReceivedFrame_IT(&EthHandle);
+  if ( HAL_ETH_GetReceivedFrame_IT(&EthHandle) != HAL_OK )
+  {
+      return NULL;
+  }

   /* Obtain the size of the packet and put it into the "len" variable. */
   len = EthHandle.RxFrameInfos.length;

And in my receive task I have this loop (ok yeah this could be prettier...)

+            do
+            {
+                p = low_level_input(netif);
+                if (p != NULL)
+                {
+                    if (netif->input(p, netif) != ERR_OK)
+                    {
+                        pbuf_free(p);
+                    }
+                }
+            } while (p != NULL);

Hope it helps!

BR /Jens

On 2014-03-20 19:13, Sergio R. Caprile wrote:
Yes Jens, looks like you are absolutely right, missed that, there is no
frame loss here, the receiving process must be getting only the first
frame in the "chip" cue.

Julien is using some ST microcontroller, I guess it has a built-in eth
controller, probably with DMA.

I've studied the Linux drivers for the DM9000 to write my driver, and
I've seen they read all the packets out of the chip every time; then I
setup a simple test to see if interrupts would trigger on every frame or
only on empty buffer, and guess what... empty buffer only (there is no
int ack here)

Looks like we've got a different situation here, the chip seems to be
issuing an interrupt after the first one is ACKed, as you Jens described
for your case.

Julien, can you confirm this from the chip docs ?
Pitty one has to fix the drivers for a manufacturer, maybe someone in ST
can lend a hand ?

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