[ECOS] Re: Problems with ppp and Windows

[Kelvin Lawson <klawson at ad-holdings dot co dot uk>]

Hi Øyvind,

> > I've just had what appears to be the same problem as this. accept() 
> > wasn't returning until the client killed the telnet process. 
> > However in my case it was the same with Windows or Linux clients.
>
> When you say "client", are you referring to the machine on which the
> telnet session is launched?
>
> I find that the problem is with a Windows PPP *server*.
>
> It doesn't matter whether or not I start the telnet session from Windows
> or Linux.

By client I mean the machine from which the Telnet session is launched. 
I get the same problem using a Windows or Linux Telnet client (or FTP or 
anything that contacts an eCos server sitting in accept()). I also had 
the same problem whether the PPP session itself was between eCos and 
Win2k or between eCos and Linux. I can't imagine it makes any difference 
whether eCos "dials up" the other end, or visa versa.

I'm surprised that this is only a problem connecting with Windows via 
PPP. Was there anything different about your setup when you connected to 
Linux ? Maybe on your Windows configuration the eCos target had an 
Ethernet interface up as well ? (that will use up a few network 
buffers). Or is your Linux PPPD perhaps running with the "novj" option ?


> > I'm not sure if this will be your problem, but it's worth a go. Try 
> > adding some more memory to CYGPKG_NET_MEM_USAGE. The VJC structure needs 
> > a little over 4KB on my target. You can confirm whether this is your 
> > problem by checking the result of the MALLOC in pppalloc().
>
> I've been toying with PPP on an EB40a card board, which only has
> 256kbytes of memory.
>
> I've set CYGPKG_NET_MEM_USAGE = ~90k.

If you need to save some RAM, perhaps an alternative would be to disable 
VJ compression. On a brief look in ipcp.c it looks like it's possible to 
refuse by setting neg_vj = 0. Presumably there will be a few other 
tweaks around the PPP code to handle this properly.

It would be nice to handle the failed slcompress MALLOC by refusing to 
negotiate VJ compression. Either that or a big printf/assert on the 
failed MALLOC would have saved me a few hours debugging.

Cheers,
Kelvin.


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