Socket buffer

[Leon Pollak]

Hello, all.

I searched WEB and Wiki - was not able to find an answer...:-(
--
I see the message "not delivered. Socket buffer full" in 
rtems_bsdnet_show_udp_stats report.

Ok, I now tried to increase the socket buffer (from 1MB to 2MB) by the command 
setsockopt(so,SOL_SOCKET,SO_RCVBUF,&Size,sizeof(Size)).

 - failed. 

Debugging shows that function sbreserve fails in the first check:
/*
 * Allot mbufs to a sockbuf.
 * Attempt to scale mbmax so that mbcnt doesn't become limiting
 * if buffering efficiency is near the normal case.
 */
int
sbreserve(sb, cc)
	struct sockbuf *sb;
	u_long cc;
{

	if (cc > sb_max * MCLBYTES / (MSIZE + MCLBYTES))
		return (0);
......

Now, when I set sb_max to be 1MB, the max socket buffer size may be also not 
more then 1MB.
And I cannot set it higher to 2MB, as the calculation of sb_max * MCLBYTES 
(which is 2048) exits the 32bit limit.

This makes me think that increasing the socket buffer to such extend is 
incorrect. If so, what can I do to avoid this error?

I thought that the cause may be in the lack of CPU time, but 
rtems_cpu_usage_report shows that about 35% CPU spends in IDLE task...

Thanks a lot for any hint.
-- 
Leon