[lwip-users] Implementing non-blocking lwip_sendto, UDP only

[steinarl]

Hi,

I am working on a non-blocking UDP send through the sockets interface.  
Based on what I've seen in the source I figure there are two potential  
blocking points in tcpip_apimsg:
- sys_mbox_post, easy fix: replace with sys_arch_mbox_trypost
- sys_arch_sem_wait(apimsg->msg.conn->op_completed, 0);
This one is harder I guess, but it seems an easy fix is to just not  
wait for the semaphore to be signaled.

My question is, where will I create a mess if I just ignore the signal  
and return straight away?

The sending thread won't know if the packet is ever transmitted, but  
then again UDP is unreliable.

I know other signals go through tcpip_apimsg as well, so any problems  
with those and I'll just single out the sending as a separate function  
in tcpip.h.

I'm supposed to make select work together with this non-blocking send  
as well, could that make matters more complicated?



- Steinar