Re: [lwip-users] PPP - TCP

[Sylvain Rochet]

Hi Norberto,

On Mon, Jan 18, 2016 at 08:14:17AM -0200, Norberto R. de Goes Jr. wrote:
> Hi Sylvain.
> 
> I changed the "simhost.c" file to use the pppos_input_sys function
> (attached full file) conforming your orientation.

Well, I mislead you, sorry, you have to use pppos_input_tcpip, not 
pppos_input_sys. I don't even understand how you managed to follow that, 
it's pretty clear in the header documentation that pppos_input_sys is 
an internal only function which must not be used in user application.


> "...
>   while(1) {
>       sizeRead = sio_read(ppp->ppp_sio, buffer, 1000);
>       if (sizeRead > 0) {
>          /* struct pbuf *pBuffer = pbuf_alloc(PBUF_LINK, sizeRead,
> PBUF_RAM); */
>          struct pbuf *pBuffer = pbuf_alloc(PBUF_RAW, sizeRead, PBUF_POOL);
> 
>           if (pBuffer == NULL) {
>               printf("Allocate memory fail.\n");
>               return;
>           }
>           MEMCPY(pBuffer->payload, buffer, sizeRead);

Added to that, you failed to understand how PBUF_POOL buffers are 
working, what you are doing here is a buffer overflow. PBUF_POOL are 
*chained* buffers, that's explained in the very first basic lwIP 
documentation. I have serious doubt about how you are using the stack, 
which might explain why you seem to have packet corruption.

What you need to use here is pbuf_take(), which basically do the 
following:

struct pbuf *p;
u8_t *b;
for (p = pBuffer, b = buffer; p != NULL; p = p->next) {
  MEMCPY(p->payload, b, p->len);
  b += p->len;
  if (p->tot_len == p->len) {
    break;
  }
}

Of course that's not necessary for pppos_input_tcpip, which take 
buffer+buffer_len as arguments.


>           pppos_input_sys(pBuffer, &pppos_netif);
>       }
>   }
> ..."


Sylvain

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