Howdy y'all.

Most of you probably have never messed with this but it can't hurt
to ask.

I have some Linux 2.0.x production systems that I can't upgrade, and I 
have a Linux 2.2.x (Red Hat 6.2) system that I recently installed.  I've
had a nice VPN (Virtual Private Network) running for some time using the
Linux 2.0.x tunneling driver.

To get that driver to work, you have to load the ipip.o module and the
new_tunnel.o module.  Once both of these modules are loaded, there is a
"tunl0" device in /proc/net/dev that can be ifconfiged as a point-to-point
interface.  (Just like PPP, SLIP, etc.)  With the proper routing commands,
the tunnel works fine.

Since I've had such good luck with the Linux tunnelling under Linux 2.0.35
and other such old kernels, I thought I try to extend it to this new Red Hat
Linux system.  Unfortunately the new kernel seems to want me to use GRE
encapsulation on my tunnellig packets, which my old Linux kernels don't
support.

I found the "ipip.o" kernel module for the 2.2.12 kernel, and when I load
it there is a "tunl0" interface that shows up in /proc/net/dev .  The 2.2.14 
ipip.o module appears to contain the IPIP encapsulation _and_ the tunnelling
network device; under the older kernel there were two modules for this.

However, I can't configure it as a point-to-point interface.  Whenever I
type "ifconfig tunl0 192.168.168.168 pointopoint 10.2.3.45" it gets the
IP address of 192.168.168.168, link encap IPIP, but the P-t-P is NOT,
repeat NOT, present in the ifconfig.  For some reason I canNOT set the
IFF_POINTOPOINT flag on the interface, and so my pointopoint directive
on the ifconfig line gets ignored.

And, then tunnelling doesn't work of course.

Can anyone suggest how I can continue to use my old Linux-proprietary
tunnelling encapsulation even on a 2.2.14 kernel?

A normal point-to-point interface, like ppp, looks like this:

ppp0      Link encap:Point-to-Point Protocol  
          inet addr:192.168.1.254  P-t-P:192.168.3.254  Mask:255.255.255.255
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1500  Metric:1
          RX packets:42121 errors:0 dropped:0 overruns:0 frame:0
          TX packets:41518 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:10 

The bogus tunnelling interface looks like this on my Linux 2.2.14 system:

tunl0     Link encap:IPIP Tunnel  HWaddr   
          inet addr:192.168.1.254  Mask:255.255.255.0
          UP RUNNING NOARP  MTU:1480  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 

As you can see there is no P-t-P:other.ip.address on the latter ifconfig
line.  Also in the flags it does not say "UP POINTOPOINT RUNNING NOARP"
like I want it to.  If I try to use the interface I get lots of errors
in the statistics.

I've spent the better part of an afternoon battling this and I finally
gave up.  Help...

--
Jim Ockers (ockers@ockers.net)                     Ask me about Linux!
Contact info: please see http://www.ockers.net/

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