ppp reconnects after receiving ConfReq id=0x3 <mru 1400>

ppp reconnects after receiving ConfReq id=0x3 <mru 1400>

[Rajkumar S]

Hi,

I am trying to connect to net via a USB CDMA device, on a debian etch
system. I can configure ppp with out any problem and also connect to
net, but after I connect ppp disconnects and reconnects frequently
after receiving this message from the peer.

rcvd [LCP ConfReq id=0x3 <mru 1400> <asyncmap 0x0> <auth chap MD5>
<magic 0xfb6a0660>]

my ppp config is:

hide-password
noauth
connect "/usr/sbin/chat -v -f /etc/chatscripts/vsnl"
debug
/dev/ttyACM0
460800
defaultroute
replacedefaultroute
noipdefault
user "internet"
ipparam vsnl
usepeerdns

This usually happens if there is a default gateway via ppp0 device.
The  connection stays online for hours if there is no default gw. I am
posting full logs at http://pastebin.ca/748250

I am sitting behind this for couple of days with out any solution, any
help to resolve this is much appreciated.

raj

Re: ppp reconnects after receiving ConfReq id=0x3 <mru 1400>

[James Carlson]

Rajkumar S writes:
> I am trying to connect to net via a USB CDMA device, on a debian etch
> system. I can configure ppp with out any problem and also connect to
> net, but after I connect ppp disconnects and reconnects frequently
> after receiving this message from the peer.
> 
> rcvd [LCP ConfReq id=0x3 <mru 1400> <asyncmap 0x0> <auth chap MD5>
> <magic 0xfb6a0660>]

That's what it's supposed to do, as described in the state machine in
RFC 1661.  A new Configure-Request message in Opened state pushes us
back to Req-Sent or Ack-Sent state, depending on the contents of the
message.  It tears down the link and starts over.

> I am sitting behind this for couple of days with out any solution, any
> help to resolve this is much appreciated.

I've looked over your logs, and I'm afraid you'll need to ask the
owner of that peer system why he's sending you an unexpected LCP
Configure-Request message.

If he doesn't know or can't fix it, then you'll probably need to find
a different peer to talk with.

-- 
James Carlson         42.703N 71.076W         <carlsonj@workingcode.com>

Re: ppp reconnects after receiving ConfReq id=0x3 <mru 1400>

[Bill Unruh]

On Wed, 24 Oct 2007, Rajkumar S wrote:

> Hi,
>
> I am trying to connect to net via a USB CDMA device, on a debian etch
> system. I can configure ppp with out any problem and also connect to
> net, but after I connect ppp disconnects and reconnects frequently
> after receiving this message from the peer.
>
> rcvd [LCP ConfReq id=0x3 <mru 1400> <asyncmap 0x0> <auth chap MD5>
> <magic 0xfb6a0660>]
>
> my ppp config is:
>
> hide-password
> noauth
> connect "/usr/sbin/chat -v -f /etc/chatscripts/vsnl"
> debug
> /dev/ttyACM0
> 460800
> defaultroute
> replacedefaultroute
> noipdefault
> user "internet"
> ipparam vsnl
> usepeerdns
>
> This usually happens if there is a default gateway via ppp0 device.

I do not understand this statement. What is the purpose of the connection?
Is that supposed to be an ISP through which you connect to the rest of the
net, or is a peer yousimply want to connect to directly. If the latter,
then why make it your default gateway? 
I assume you mean by "there is a default gateway via ppp0" that you have
that defaultroute option, and when you do not have a default gateway you
have removed the defaultroute options from the ppp config file.

If this is not true, then what do you mean by that statement?

But as Carlson says, the problem seems not to be on your end, but on the
far end of your connection and that is where the solution will have to be
implimented.



> The  connection stays online for hours if there is no default gw. I am
> posting full logs at http://pastebin.ca/748250
>
> I am sitting behind this for couple of days with out any solution, any
> help to resolve this is much appreciated.
>
> raj
> -
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>

-- 
William G. Unruh   |  Canadian Institute for|     Tel: +1(604)822-3273
Physics&Astronomy  |     Advanced Research  |     Fax: +1(604)822-5324
UBC, Vancouver,BC  |   Program in Cosmology |     unruh@physics.ubc.ca
Canada V6T 1Z1     |      and Gravity       |  www.theory.physics.ubc.ca/

Re: ppp reconnects after receiving ConfReq id=0x3 <mru 1400>

[Rajkumar S]

On 10/25/07, Bill Unruh <unruh@physics.ubc.ca> wrote:
> On Wed, 24 Oct 2007, Rajkumar S wrote:
> > This usually happens if there is a default gateway via ppp0 device.
>
> I do not understand this statement. What is the purpose of the connection?

Sorry for the confusion, It is indeed for my internet access and it is
the default gateway. But to find out why the connection is getting
resetted frequently, I removed the default route temporarly to rule
out the possibility that a low signal strength is causing the issue.
(it's a CDMA Modem)

So the ConfReq is coming only when a packet is flowing from my system
to the peer and not when connection is idle.

raj

Re: ppp reconnects after receiving ConfReq id=0x3 <mru 1400>

[Rajkumar S]

On 10/25/07, James Carlson <carlsonj@workingcode.com> wrote:
> If he doesn't know or can't fix it, then you'll probably need to find
> a different peer to talk with.

I hope I can atleast find some one from ISP who knows what ppp is  :(

raj

Re: ppp reconnects after receiving ConfReq id=0x3 <mru 1400>

[Bill Unruh]

On Thu, 25 Oct 2007, Rajkumar S wrote:

> On 10/25/07, Bill Unruh <unruh@physics.ubc.ca> wrote:
>> On Wed, 24 Oct 2007, Rajkumar S wrote:
>>> This usually happens if there is a default gateway via ppp0 device.
>>
>> I do not understand this statement. What is the purpose of the connection?
>
> Sorry for the confusion, It is indeed for my internet access and it is
> the default gateway. But to find out why the connection is getting
> resetted frequently, I removed the default route temporarly to rule
> out the possibility that a low signal strength is causing the issue.
> (it's a CDMA Modem)

Ah, so it is a wireless phone connection? In that case all bets are off.
The phones tend to work by doubling the layers-- you sign on to the cell
phone and it then makes the connection to the remote end. And the writers
of ppp for the cell phones tend to be some poor flunkeys who were handed
the job of writing a ppp with no training or prior experience, and they not
unnaturally tend to make a hash of it (ppp is a complex protocol and there
are loads of places to screw up).

So, it is probably the ppp in your phone which is constantly asking for
reauthentication.

It may well be that it has a timeout, which kicks in after x seconds. So
one thing you might be able to try is to either switch on the LCP-ECHO
provisions, or to ping the other side of the connection every 15 sec to
make sure that the connection stays open.


>
> So the ConfReq is coming only when a packet is flowing from my system
> to the peer and not when connection is idle.

If I am right then it is coming where there has been a long lull and you
start sending packets. If that is not the case, then my theory is a load of
fertiliser.


>
> raj
>

Re: ppp reconnects after receiving ConfReq id=0x3 <mru 1400>

[James Cameron]

Rajkumar,

I had this same problem persistently on a CDMA USB modem, two or three
years ago, and when I had the problem many other people had the same
problem at the same time.

I too noticed that the default route had something to do with it, as I
was running the system with multiple interfaces.  So I used pppdump and
tcpdump to capture information about the packets being sent by my
system.  

I found that I could reliably crash the remote PPP by emitting a packet
that originated from one of the other IP addresses my system had before
the connection was established or the route was switched.  Within a
second or two of the packet being sent, the LCP ConfReq arrived to
restart PPP.

It was particularly annoying because every time it happened, it cost me
another $0.50.

The fix I made to prevent it happening was to filter the packets that my
system was sending.  I added several iptables rules.  I don't have the
exact list of rules that worked, but you can derive them from examining
the packets that trigger the problem.

The simplest rule might be to drop all packets that do not come from the
IP address assigned to you by the connection.

My /etc/ppp/ip-up.d/cdma script has the following remnant rules:

        # drop anything untoward
        iptables --insert OUTPUT 1 --source 192.168.0.0/255.255.0.0 \
            --destination 0.0.0.0/0.0.0.0 --jump DROP \
            --out-interface ${PPP_IFACE}

        iptables --insert OUTPUT 1 --source 10.0.0.0/255.255.0.0 \
            --destination 0.0.0.0/0.0.0.0 --jump DROP \
            --out-interface ${PPP_IFACE}

        iptables --insert OUTPUT 1 --protocol GRE --jump DROP \
            --out-interface ${PPP_IFACE}

(192.168/16 was a satellite service, 10.0/16 was a local area network,
and the GRE packets were from prior instances of pptp that may not have
terminated cleanly.)

-- 
James Cameron                         http://quozl.netrek.org/
HP Open Source, Volunteer             http://opensource.hp.com/
PPTP Client Project, Release Engineer http://pptpclient.sourceforge.net/

Re: ppp reconnects after receiving ConfReq id=0x3 <mru 1400>

[Rajkumar S]

On 10/25/07, James Cameron <james.cameron@hp.com> wrote:
> I found that I could reliably crash the remote PPP by emitting a packet
> that originated from one of the other IP addresses my system had before
> the connection was established or the route was switched.  Within a
> second or two of the packet being sent, the LCP ConfReq arrived to
> restart PPP.

Thanks James, this is exactly my problem. I have verified this and as
soon as a packet from another ip goes via ppp connection a ConfReq
packet arrives and connection is reset.

raj