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tony.chamberlain | 4 Aug 22:37

timeout

I am using pptp which calls pppd.  I use ip-up.local to add routes.

Problem is, when connecting, after only 10 or 15 seconds the link gets dropped
by the peer due to inactivity (I think it is the peer and not me).

Anyway I can make a stupid script to ping the other side every 5 seconds, which keeps the link up.  But there
should be a better way.  I thought lcp-echo-request set to 5 would do it, but that sends only if it hasn't
heard from the peer in 5 seconds, and by then it is too late.

Any suggestions?

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Bill Unruh | 4 Aug 22:44
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Re: timeout

On Mon, 4 Aug 2008, tony.chamberlain <at> lemko.com wrote:

> I am using pptp which calls pppd.  I use ip-up.local to add routes.
>
> Problem is, when connecting, after only 10 or 15 seconds the link gets dropped
> by the peer due to inactivity (I think it is the peer and not me).

Who is the peer? Are you sure you do not have a timeout where you thought
the time was in minutes but really is in seconds?

>
> Anyway I can make a stupid script to ping the other side every 5 seconds, which keeps the link up.  But there
should be a better way.  I thought lcp-echo-request set to 5 would do it, but that sends only if it hasn't
heard from the peer in 5 seconds, and by then it is too late.
>
> Any suggestions?
>
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-ppp" in
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>

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James Cameron | 5 Aug 03:00
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Re: timeout

On Mon, Aug 04, 2008 at 08:37:55PM +0000, tony.chamberlain <at> lemko.com wrote:
> I am using pptp which calls pppd.  I use ip-up.local to add routes.
> 
> Problem is, when connecting, after only 10 or 15 seconds the link gets
> dropped by the peer due to inactivity (I think it is the peer and not
> me).

If you have added routes that change the route used by pptp for the GRE
packet stream, then the peer will drop the connection because the LCP
echo requests are not replied to.

Does the same problem occur without your route changes?

Which version of pppd?  Which version of pptp?

> Anyway I can make a stupid script to ping the other side every 5
> seconds, which keeps the link up.

I'm surprised.

It would be more useful to see a "debug dump" log posted on a web page
for us to look at.

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PPTP Client Project, Release Engineer http://pptpclient.sourceforge.net/
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Marshall Crocker | 11 Aug 01:06
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How to fix continuous ConfReq's on celluar internet connection

Hi all,

For over a year now I've been having problems with ConfReq's resetting 
my ppp connection to my cellular EvDO internet provider.  I can connect 
with no problems but usually the connection will only stay up for a few 
minutes (sometimes a few seconds) before I receive a ConfReq.  I think 
the ConfReq is sent because I'm in a fringe area of service and my 
connection is switching between EvDO (3G broadband speeds) and 1xRTT 
(144 Kbps 2.5G).  It may also be that I'm between two towers and the 
connection is bouncing between the two thereby requiring my host to 
reconfigure.

The biggest problem with this behavior is that the ppp0 interface is 
brought down after the ConfReq is received.  Any TCP connections that 
were in progress get closed.  In Windows, the connection is reconfigured 
but either the interface isn't completely brought down or a "no route to 
host" isn't sent  for each open connection and the packets just get 
dropped during the reconfigure and then retransmitted once the 
connection comes back up so actions such as browsing  web pages only get 
stalled briefly.

So my questions are

1) Has anyone else seen this behavior or is it specific to my internet 
provider?

2) Is there some pppd option that I'm missing that could solve this problem?

3) Should I block these ConfReq's once the connection is established 
using iptables or some other method?  I assume not since the tower may
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James Cameron | 11 Aug 01:11
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Re: How to fix continuous ConfReq's on celluar internet connection

Have you tried the demand option?  This keeps the network interface
present over a reconfiguration.

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James Cameron | 11 Aug 01:21
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Re: How to fix continuous ConfReq's on celluar internet connection

Oh, and something else that springs to mind ... when I had this problem
that you report with 1x RTT modems, an analysis of the packet stream
with pppdump and tcpdump resulted in a correlation between certain
packets and a reconfiguration event.

I could force it to occur by emitting packets to the modem with IP
addresses that were incorrect.  The provider's back-end NAT equipment
was closing the session when it saw such invalid packets.

The host was multi-homed, and when the 1x RTT link came up the default
route was swung onto the link.  Existing connections began to emit
packets to the modem link with a source IP corresponding to the previous
default route.  It was these packets which caused the reconfiguration.

In the end what solved the problem for me was filtering the packets
before they reached the modem ... by adding the following to an ip-up
script:

        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}

In my case, 10.0/16 was a local LAN, and 192.168/16 was the satellite
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Marshall Crocker | 11 Aug 01:28

Re: How to fix continuous ConfReq's on celluar internet connection

James Cameron wrote:
> Have you tried the demand option?  This keeps the network interface
> present over a reconfiguration.
Doh...after sending my original email I decided to add idle and demand
options to my peers file so the connection wouldn't be up all the time
(been meaning to that for a while anyway).  I read the man pages to see
what arguments they needed and saw that demand keeps the network
interface in between connections.  That appears to be working although
the ConfReq's are still coming and the connection is averaging about 0.2
minutes up.

I had no idea that the demand option would keep the ppp interface.  I
feel silly for putting up with this for over a year and the whole time a
simple pppd option would work around it.

Marshall

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Marshall Crocker | 11 Aug 02:04

Re: How to fix continuous ConfReq's on celluar internet connection

>
> The host was multi-homed, and when the 1x RTT link came up the default
> route was swung onto the link.  Existing connections began to emit
> packets to the modem link with a source IP corresponding to the previous
> default route.  It was these packets which caused the reconfiguration.
>   
I'm not doing any sort of multihoming so there is no default route until 
the ppp connection comes up. No invalid packets should be making it to 
the ISP but I'll do a capture and see what comes up...

> It looks like I've said all this before:
>
> http://osdir.com/ml/linux.ppp/2007-10/msg00011.html
>   
Sorry....I did a search on the Nabble archive for ConfReq but that 
thread wasn't returned or at least I didn't see it. 

Thanks for your help.

Marshall

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Bill Unruh | 11 Aug 02:06
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Re: How to fix continuous ConfReq's on celluar internet connection

On Sun, 10 Aug 2008, Marshall Crocker wrote:

> Hi all,
>
> For over a year now I've been having problems with ConfReq's resetting my ppp 
> connection to my cellular EvDO internet provider.  I can connect with no 
> problems but usually the connection will only stay up for a few minutes 
> (sometimes a few seconds) before I receive a ConfReq.  I think the ConfReq is 
> sent because I'm in a fringe area of service and my connection is switching 
> between EvDO (3G broadband speeds) and 1xRTT (144 Kbps 2.5G).  It may also be 
> that I'm between two towers and the connection is bouncing between the two 
> thereby requiring my host to reconfigure.
>
> The biggest problem with this behavior is that the ppp0 interface is brought 
> down after the ConfReq is received.  Any TCP connections that were in 
> progress get closed.  In Windows, the connection is reconfigured but either 
> the interface isn't completely brought down or a "no route to host" isn't 
> sent  for each open connection and the packets just get dropped during the 
> reconfigure and then retransmitted once the connection comes back up so 
> actions such as browsing  web pages only get stalled briefly.
>
> So my questions are
>
> 1) Has anyone else seen this behavior or is it specific to my internet 
> provider?
>
> 2) Is there some pppd option that I'm missing that could solve this problem?
>
> 3) Should I block these ConfReq's once the connection is established using 
> iptables or some other method?  I assume not since the tower may drop my
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Marshall Crocker | 11 Aug 07:03

Re: How to fix continuous ConfReq's on celluar internet connection


>> The host was multi-homed, and when the 1x RTT link came up the default
>> route was swung onto the link.  Existing connections began to emit
>> packets to the modem link with a source IP corresponding to the previous
>> default route.  It was these packets which caused the reconfiguration.
>>   
> I'm not doing any sort of multihoming so there is no default route 
> until the ppp connection comes up. No invalid packets should be making 
> it to the ISP but I'll do a capture and see what comes up...

What comes up are packets from a host in my local network getting sent 
out over ppp!  Every time a packet with the source from my internal 
network gets sent over ppp, the connection reconfigures. You were 
exactly right!  What I'm seeing is packets being sent out over ppp such as

192.168.0.10 -> google.com

Which means that my iptables NAT script isn't doing its job. I've never 
claimed to be an iptables expert which is why I've always used 
MonMotha's iptables firewall.  I guess its time to learn....

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