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PPTP possible bug found
- To: "Linux-IL" <linux-il(at-nospam)cs.huji.ac.il>
- Subject: PPTP possible bug found
- From: "Haim Gelfenbeyn" <rnews(at-nospam)hageltech.com>
- Date: Fri, 2 Feb 2001 12:14:56 +0300
- Importance: Normal
- Reply-To: <haim(at-nospam)hageltech.com>
- Sender: linux-il-bounce(at-nospam)cs.huji.ac.il
Hello,
I think I've found at least some of the problems with PPTP on Linux.
A agree with Dani Arbel that the problem is more likely in PPTP and non in
PPP, because PPP replies are from the remote end, and not from the ADSL
modem. So, I've used Ethereal to sniff on both Windows 2000 SP1 connecting
to Orckit ATUR3, and on Linux pptp (patched by mulix version) connecting to
the same modem. I don't want to make the sniffs public right now because
they probably contain my username/password and what else, but can discuss it
if anyone knows how to make use of them and will contact me privately.
There are some differences in nearly all packets, but the main difference I
found is this:
pptp doesnt set "Call ID" correclty on GRE (encaplulated) packets, and
because of it the modem never forwards the packets further, and the result
is that PPPD sends "LCP requests" but never receives an answer.
The fix I did:
In pptp_gre.c, function pptp_gre_copy(), changed "pptp_gre_call_id =
call_id" to "pptp_gre_call_id = peer_call_id"
Now, what happens at least on my machine: PPPD correctly negotiates MTU,
etc. via LCP, but for some reason it tries to negotiate "192.168.0.10" as IP
address with the remote server, it sends NAK and PPPD dies. I don't know
whether this is related or not. 192.168.0.10 is the other (internal LAN)
interface on my Linux box.
So, this is clearly a step forward, but more work needs to be done...
Best regards,
Haim Gelfenbeyn.
--------==============================================----------
HAGEL TECHNOLOGIES Haim Gelfenbeyn, CEO
E-mail: haim@hageltech.com Phone: +972 (54) 249593
================== http://www.hageltech.com ==================
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