[lwip-users] raw api recv callback - procedure to (temporarily) refuse data?

[Roger Kinkead]

Hi all,

I am using LWIP 1.1.0 - which appears to be performing very well indeed -
using the RAW API.

What is the correct manner to return from the recv_callback when the data
may not be processed immediately?
I have experimented with several combinations of return code/whether to call
tcp_recvd with zero and/or free the pbuf - but with no luck yet?

My receive callback is summarised as follows :-


// recv callback which places incoming data into rx queue
static err_t btcp_recv_cb(void *arg, struct tcp_pcb *tpcb, struct pbuf *p,
err_t err)
{
   btcp_t *h = (btcp_t *)arg;
   struct pbuf *q;
   int q_write_tot = 0;
   ASSERT(h != NULL);
   ASSERT(tpcb == h->pcb);
   if(p == NULL)
   {
      // closed connection?
      . . .
   }
   else
   {
      h->poll_retries = 0; // <- reset poll timer, due to rx activity

      // check data transfer size
      q_write_tot = 0;
      for(q=p; q != NULL; q=q->next) q_write_tot += q->len;
      // room?
      if( q_write_tot < q_room(h->q_rx) )
      {
         // transfer data into rx queue
         for(q=p; q != NULL; q=q->next)
            q_write(h->q_rx, q->payload, q->len);
         // indicate data has been received
         tcp_recved(tpcb, q_write_tot);
         pbuf_free(p);
      }
      else
      {
         // WHAT TO DO HERE???? not enough room (just at this moment in
queue!)
         //tcp_recved(tpcb, 0);
         pbuf_free(p);
         return(ERR_OK);
      }
   }
   return(ERR_OK);
}



Thanks!

Roger