TUN device for VPN - File descriptor in bad state

[drbob <drbob@gmx.co.uk>]

Hello,

I'm trying to implement an opevpn server on my debian box. The first 
step was to recompile my kernel (2.4.32) with TUN?TAP support built in. 
I did this and created the /dev/net/tun device however it does not work. 
cat /dev/net/tun returns:

cat: /dev/net/tun: File descriptor in bad state

Searching the web for a debian specific solution has been a fruitless 
exercise. It seems the problem stems from a mismatch between the kernel 
and the installed headers. A similar question has been asked on the list 
before and the poster was pointed to the vtun list archives, however the 
only suggestion there is to link /usr/include/linux and /usr/include/asm 
to the current kernel source directory, afaik this is not the debian way 
and I don't know what else I'd break if I did this. Is there a better 
way to solve the problem?

regards,

drbob