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Re: linux box dropping LCP packet from win2k3 PPTP server.



Hello,

    No, i  am not getting protocol reject from pppd linux. Here is the
wireshark capture attached as pptp.ws.capture.tgz, please untar it and
open the resulting file with wireshark. the concerned packets will
appear when you apply the display filter as:
pptp || gre

I have tried to analyse the issue further and found out that this is
not in pppd issue but the problem is being observed in pptp client.
Inside,  where it tries to match the callid received from the server
and the callid expected.

file: pptp-1.7.0/pptp_gre.c
func: decaps_gre
-----------------------------------------------------------------------
    if (ntoh16(header->call_id) != pptp_gre_call_id)
        return 0;
------------------------------------------------------------------------
putting a print statement there gives me something like
call Id recvd (ntoh16(header->call_id): 8cc,
call Id  pptp_gre_call_id (expected)   : 0

and it is due to something going wrong in the function open_callmgr (
) in file pptp.c

Thanks,
Kapil U

On Thu, Feb 26, 2009 at 10:50 PM, Sriram K <ksriram29@xxxxxxxxx> wrote:
> Hi,
> Are you getting protocol reject from the linux pppd. can you send the
> ethereal/wireshark capture?
>
> Regards,
> Sriram K
>
>
> On Sat, Feb 21, 2009 at 6:37 PM, Kapil Upadhayay <kupadhay@xxxxxxxxx> wrote:
>>
>> Hello,
>>
>> i  am using pppd 2.4.4b1 on client side on linux-2.6.10 kernel with
>> mppe support enabled. My scenario is like, from my linux box I am
>> trying to connect to a win2k3 server host connected locally in my
>> subnet.  After repeated trials I  am unable to do so, though i  am
>> able to connect to linux pptp server (with mppe enabled).  Can you
>> please help me  out where exactly things are going wrong. On network
>> sniffer i  can see that the LCP Conf-Req.  packet is being sent
>> through the windows host to my linux box and my linux box's firewall
>> is not dropping it.
>>
>> I  tried to get to the root cause of the issue and  i see read_packet(
>> ) repeatedly calling  read( ) which in turn tries to read from
>> /dev/ppp. Read always returns -1 to read_packet(). Is it because the
>> driver is not writing anything to /dev/ppp and the daemon is not able
>> to read it?.  On the driver side i.e ppp_generic.c and ppp_async.c I
>> do not see  ppp_input( ) being called.  Please correct me if  I am
>> wrong as I am new to PPP.  Is it the right place to see or the issue
>> is in GRE.
>>
>> please have a look on the logs below
>>
>> pppd logs:
>> ----------
>> [pppd] pppd 2.4.4b1 started by root, uid 0
>> [pppd] Starting connection
>> [pppd] using channel 566
>> [pppd] Using interface ppp0
>> [pppd] Connect: ppp0 <--> /dev/ttyp0
>> [pptp] anon log[main:pptp.c:267]: The synchronous pptp option is NOT
>> activated_
>> [pptp] anon log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type
>> is 1 'Start-Control-Connection-Request'_
>> [pptp] anon log[ctrlp_disp:pptp_ctrl.c:738]: Received Start Control
>> Connection Reply
>> [pptp] anon log[ctrlp_disp:pptp_ctrl.c:772]: Client connection
>> established.
>> [pppd] sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0x9c77b516>
>> <pcomp> <accomp>]
>> [pptp] anon log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type
>> is 7 'Outgoing-Call-Request'_
>> [pptp] anon log[ctrlp_disp:pptp_ctrl.c:857]: Received Outgoing Call Reply.
>> [pptp] anon log[ctrlp_disp:pptp_ctrl.c:896]: Outgoing call established
>> (call ID 0, peer's call ID 28336)._
>> [pppd] sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0x9c77b516>
>> <pcomp> <accomp>]
>> [pppd] sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0x9c77b516>
>> <pcomp> <accomp>]
>> [pppd] Child process pptp 192.168.3.2 --nolaunchpppd (pid 12728)
>> terminated with signal 15
>> [pppd] Child process pppd (charshunt) (pid 12730) terminated with signal
>> 15
>> [pptp] anon log[callmgr_main:pptp_callmgr.c:255]: Closing connection
>> (shutdown)
>> [pptp] anon log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type
>> is 12 'Call-Clear-Request'_
>> [pptp] anon log[ctrlp_disp:pptp_ctrl.c:928]: Call disconnect
>> notification received (call id 0)
>> [pptp] anon log[ctrlp_error:pptp_ctrl.c:199]: Result code is 0
>> 'Unknown Result Code'. Error code is 0, Cause code
>> [pptp] anon log[call_callback:pptp_callmgr.c:78]: Closing connection
>> (call state)
>> [pppd] Modem hangup
>> [pppd] Connection terminated.
>> [pppd] Exit.
>>
>> here is the output of pppdump -p
>> --------------------------------
>> time  1.7s
>> sent  ff 03 c0 21 01 01 00 14 02 06 00 00 00 00 05 06  ...!............
>>      2d db f3 6e 07 02 08 02                                      -..n....
>> time  3.0s
>> sent  ff 03 c0 21 01 01 00 14 02 06 00 00 00 00 05 06  ...!............
>>      2d db f3 6e 07 02 08 02
>> -..n....
>>
>> here is the command used to invoke pppd/pptp:
>> ---------------------------------------------
>> pppd 0.0.0.0:0 lcp-echo-failure 10 lcp-echo-interval 5 noauth
>> nobsdcomp nodeflate defaultroute user pptp password aesgs123 mtu 1492
>> linkname 0 idle 0  pty 'pptp 192.168.3.2 --nolaunchpppd record
>> /var/pppRecOut require-mppe-128
>>
>> PS: Also can you please point me where is the starting point the where
>> the LCP packet is received by the  PPP driver, if that is the case. OR
>> ppp driver comes into picture only when link negotiation had has
>> successfully completed and actuall PPP packets can be transmitted over
>> the link.
>>
>> Thanks,
>> kapil
>> --
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>
>

Attachment: pptp.ws.capture.tgz
Description: GNU Zip compressed data


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