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Old 12-27-2010, 12:11 PM
Roland Rosier
 
Default PPTP Issues in Debian Testing/Squeeze

Hello,

I am wondering if anyone has come across a similar issue to one I am encountering with Debian Testing/Squeeze.

I have been using Debian for many years as a Firewall for my family's computers.

I have a ppp interface as the Internet interface and another Ethernet / WiFi interface within my house.

Originally, the ppp interface was a dial-up modem, but since the advent of broadband it became a PPTP tunnel forwarded from my ADSL modem.

This had been working fine on Debian system I set up many years ago, but recently that PC died.

I have built a new system and installed Debian Testing on it (because it should shortly be released as Debian Squeeze and I hoped that if I got Testing working the upgrade to Squeeze should be relatively pain-free).

Unfortunately, my network speed appears to be less than 1/10th of what it was previously, even though I believe that I copied all the ppp configuration files over accurately from the old system.

I put ppp into debug mode and have been looking at the logs.

I get a huge number of lines in my syslog saying:

Dec 27 12:51:54 xxxxx pptp[5043]: anon log[decaps_greptp_gre.c:414]: buffering packet 20895 (expecting 20894, lost or reordered)

(the packet numbers change).

I have tried leaving the MTU unset in the ppp configuration files, and I have also tried setting it to 1416, 1454, 1492 and 1500 (which seem to be common values recommended on the Internet).

I am using the Shorewall firewall with the "two-interfaces" configuration.* I have set IP_FORWARDING=On and CLAMPMSS=yes in shorewall.conf.

I am uncertain if the issue is with ppp, pptp, Shorewall or something else.

I am also uncertain if this could be an issue with the "Testing" distribution as I have never seen anything like this with any of the previous Debian distributions I have used.

I would be grateful if anyone has seen this before and could let me know what the issue could be.

Regards,
Roland Rosier

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Old 12-27-2010, 12:25 PM
"Russell L. Harris"
 
Default PPTP Issues in Debian Testing/Squeeze

* Roland Rosier <rrdebian@hotmail.co.uk> [101227 13:14]:

> I have been using Debian for many years as a Firewall for my
> family's computers.

...

> I am using the Shorewall firewall with the "two-interfaces"
> configuration.*

You might get a clue as to what is happening by installing another
system such as SmoothWall3 (www.smoothwall.org) on the machine and
then inspecting the logs and statistics.

SmoothWall takes over the entire drive, so you might wish to plug in a
spare small drive for the test. The installation and configuration of
SmoothWall can be done in about fifteen minutes, using a gui. The
system is very well documented.

RLH


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Old 12-27-2010, 04:16 PM
Roland Rosier
 
Default PPTP Issues in Debian Testing/Squeeze

Hello Russell,

Thank you for your reply,

I have got the old firewall running (possibly briefly - I think the HD is nearly dead).

It still gets full speed on my Internet connection.

I do get 2 log messages in syslog, they are a pair:
Dec 27 16:25:26 XXXXOLD pptp[4373]: anon log[ctrlp_repptp_ctrl.c:243]: Sent control packet type is 5 'Echo-Request'
Dec 27 16:25:26 XXXXOLD pptp[4373]: anon log[logechoptp_ctrl.c:659]: Echo Reply received.

I don't get any of the messages about buffering packets being lost or reordered.

ICMP type 5 is Source Route failed from RFC 792 (http://www.rfc-archive.org/getrfc.php?rfc=792)

I don't seem to have any type 5 control packet logs in the new syslog.

I wonder if Shorewall is blocking these control packets, where the firewall in my old setup didn't?

My old Debian was Debian Sarge, release 3.1. My old firewall was ipmasq.
My old kernel was 2.6.8-2-686.

My new Debian is Debian Testing/Squeeze. My new firewall is Shorewall (4.4.11.6).
My new kernel is 2.6.32-5-amd64.

Regards,
Roland Rosier

> > I am using the Shorewall firewall with the "two-interfaces"
> > configuration.
>
> You might get a clue as to what is happening by installing another
> system such as SmoothWall3 (www.smoothwall.org) on the machine and
> then inspecting the logs and statistics.
>
> SmoothWall takes over the entire drive, so you might wish to plug in a
> spare small drive for the test. The installation and configuration of
> SmoothWall can be done in about fifteen minutes, using a gui. The
> system is very well documented.
>
> RLH

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Old 12-28-2010, 08:33 AM
Pascal Hambourg
 
Default PPTP Issues in Debian Testing/Squeeze

Hello,

Roland Rosier a écrit :
> I get a huge number of lines in my syslog saying:
>
> Dec 27 12:51:54 xxxxx pptp[5043]: anon log[decaps_greptp_gre.c:414]:
> buffering packet 20895 (expecting 20894, lost or reordered)

1) It could be a packet loss issue at the link layer level. Run a packet
sniffer such as tcpdump or wireshark/tshark on the ethernet interface
connected to the modem and capture the GRE traffic (IP proto 47). Then
check whether the expected packet numbers reported in syslog during the
capture are just reordered or actually missing.

2) Check the counters in the output of ifconfig for that interface too.

3) If everything seems fine at the link layer level, try to disable the
firewall.


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Old 12-28-2010, 10:04 PM
Roland Rosier
 
Default PPTP Issues in Debian Testing/Squeeze

Hello Pascal and Russell,

> Roland Rosier a écrit :
> > I get a huge number of lines in my syslog saying:
> >
> > Dec 27 12:51:54 xxxxx pptp[5043]: anon log[decaps_greptp_gre.c:414]:
> > buffering packet 20895 (expecting 20894, lost or reordered)
>
> 1) It could be a packet loss issue at the link layer level. Run a packet
> sniffer such as tcpdump or wireshark/tshark on the ethernet interface
> connected to the modem and capture the GRE traffic (IP proto 47). Then
> check whether the expected packet numbers reported in syslog during the
> capture are just reordered or actually missing.
>
> 2) Check the counters in the output of ifconfig for that interface too.
>
> 3) If everything seems fine at the link layer level, try to disable the
> firewall.

It would appear that the issue was with the actual on-board Ethernet.

I disabled my new motherboard's on-board Ethernet and installed an old (and known-working-with-Linux) PCI 3COM 3c905.

With this new card, I got full-speed downloads and no packet loss using the kernel driver 3c95x.

I then noticed that my Motherboard was one version down on the BIOS updates available and that the BIOS update mentioned the LAN.

So I updated my Motherboard's BIOS and removed the 3COM card.

I now seem to be getting full-speed downloads and no packet loss using the kernel driver r8169.

For reference, my Motherboard is a Gigabyte GA-880GM-UD2H Revision 1.3 and the on-board Ethernet is an RTL8111D.

Thanks for all your help and suggestions.

Regards,
Roland Rosier


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