[lwip-users] How to receive only some data

[David Vos]

I am running TCP using the callback mechanism in a single process, no threads.

In my tcp_recv() callback function, I have been doing:

for (q = p; q != NULL; q = q->next) {
 process(q->payload, q->len);
}
tcp_recved(tpcb, p->tot_len);
pbuf_free(p);


However, there are times where I am not able to process all of the
information.  What is the proper way to do it?  I assume I should
tcp_recved() the length I processed.  But, should I do a pbuf_free()
even if I didn't process all of it?  Basically, I am funnelling all
received data into a non-blocking named pipe (fifo), and I need to
push back on the stack if the fifo is full.  But when room becomes
available in the fifo, I can start processing the tcp data again.

Let's say that I am unable to process any data for awhile and my TCP
receive window is full.  Will the stack still periodically call
tcp_recv() to poll the application?  Or do I need to use tcp_poll and
somehow find the received data myself?

Thanks,
-David