Subject: Re: net/pptp
To: Hubert Feyrer <>
From: Andrew Brown <>
List: tech-pkg
Date: 04/27/2001 09:39:34
>> anyone using net/pptp?  any experiences?  any caveats?  the DESCR file
>> says i have to remove gre from my kernel.  grr...
>you seem to have a different DESCR file that I have, mine doesn't mention
>GRE. Anyways, I remember someone fighting with pptp, and the deal with gre
>was that it ate the pkgs destined for pptp, even if the interface was not
>configured. I haven't looked into this (and won't :).

you that i look again, i can't find the thing that made me
think that, even if it is correct.  oh...wait.  there it is.  it's in
the man page.

     Because pptp uses GRE by using a raw IP socket, it will not work if your
     kernel has the gre(4) pseudo-device configured.

net/pptp manually does the pptp protocol, which is roughly esp packets
inside gre.  if your kernel properly ignores these packets (ie, if gre
is not in the kernel), then pptp will be fine, otherwise it fights the
kernel.  the kernel will eat gre packets if it knows what gre is,
regardless of whether or not it has anything to do with them.

it's similar to the use of ipip and gre devices in the kernel.  they
don't peacefully coexist.

|-----< "CODE WARRIOR" >-----|             * "ah!  i see you have the internet (Andrew Brown)                that goes *ping*!"       * "information is power -- share the wealth."