[pptp-server] a *bizarre* situation

[John Leach]

ok an update, to rule the suspicious rpms I made out of the equation I
compiled everything from source...

Now I'm using ppp 2.4.1 patched accordingly, Kernel 2.4.3-ac14 patched
with the kernel ppp mppe patch (the 2.4.4 patch ran fine), and pptpd
v1.1.2

Then, as recommended by Robert <berzerke at swbell.net> I used the win2k
configs from his website http://home.swbell.net/berzerke.  But still to
no avail.

I've used pptp quite a lot and can usually get it working from scratch
in less than half an hour!  I've had win2k working with it fine, with
and without encryption (fully tested by dumping the passing packets to
ensure they *were* encrypted).

I'm going nuts now, I'm sure I can't be missing something simple, the
vpn tunnel is doing its job!  the packets go from A to B, and arrive
safely but win2k does not seem to recognise them as the replies it
expects.  I repeat, I've sniffed the packets actually arrive fine, after
being decrypted and passing along the network interface, but they aren't
being acknowledged by some other part of win2k, arrrrgh.

If this *is* something simple, I'm going to look very relieved and very
stupid, I'll push myself to admit this publically if I do figure out its
me being silly.

John Leach.

> Ok, now this has me doing some serious swede scratching....
> 
> This is over a local lan, with no firewalls or routers in between, just
> a switch.
> 
> I have a Win2k client (actually 2, one advanced server, another pro SP2)
> connecting to pptpd v1.1.2, pppd 2.4.0 (with the relevant patches to
> make mppe work), on Linux kernel 2.4.3 again with the relevant patches.
> 
> I connect un-encrypted, everything works fine, things work superbly in
> fact.
> 
> I connect using encryption, and everything *seems* to work fine.  auths,
> connects, sets up the tunnel...  but the win2k box doesn't seem to
> actually *see* the packets it receives.  But it definately does get
> them.
> 
> A simple ping test from the win2k box to the other end of the ppp
> connection results in an outgoing icmp request which the linux server
> receives ok, which then replies with an icmp reply, which arrives at the
> other end of the tunnel fine too, but the win2k box doesn't see it.
> 
> I know the packets are being received as I've used WinEthereal and have
> captured them.  I've tried this with TCP connections too, win2k just
> doesn't see the ack packets even tho they actually get received.
> 
> To be truthful I'm faffing around with an rpm I made last month of this
> lot, which I've tested before and has been confirmed to work, I *should*
> be recompiling from source manually and re-testing, but I'd really like
> to know what is going on.
> 
> There are *no* packet filters of any kind active on either win2k box or
> the linux box.  I wanted to test via the linux pptp client but I can't
> seem to make it use mppe, it always defaults to cleartext. 
> 
> This has me stumped.  I first thought data was being corrupted
> somewhere, but ethereal should pick up on that (I beleive it checks the
> crcs).  I can see the incoming gre packets, and the resulting
> un-encapsulated packets, but win2k never seems to actually use them.
> 
> ARGH!
> 
> John Leach. MCP, CCNA, BOFH, EGO.
> 
> 
> 
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