RTEMS 4.X.X gen68360 Ethernet Tx Reliability

[Bob Wisdom]

Clues and Red Herrings!
-----------------------------------
We have discovered that if we negate the code which attempts to skip empty
MBUFs we can achieve reliable transmission. Obviously, one cannot allow the
SCC to try and send a zero length buffer, so we implemented a little in-line
"scatter" function which split the previous SCC TX buffer into two, thus
filling the TX buffer which would have corresponded to the zero length MBUF.
Bingo, it all seems to work ok. Anyone got any ideas why? - we have sent
hundreds of Megabytes using buffer sizes > 1500 which was impossible before,
it hasn't failed yet.

Next problem - or maybe ignorance on my part more likely. The netdemo prog
has a TCP test. You type "t" to start it. We set up our Linux box to act as
a packet dump on the discard port and we find that we can only run the test
every couple of minutes. If we try to repeat it too quickly we get an error
which says "Can't bind to socket". Is this a TCP phenomenon?

Bob Wisdom
bobwis at ascweb.co.uk