Comment 19 for bug 565856

People using VPN software indeed face this issue. See :
http://ubuntuforums.org/showthread.php?t=1459559&highlight=module+tun+aventail&page=3

This link mentions a work-around :

sudo apt-get install build-essential linux-headers-`uname -r`
mkdir faketun
cd faketun
echo -e "#include <linux/module.h>\nstatic int start__module(void) {return 0;}\nstatic void end__module(void){return;}\nmodule_init(start__module);\nmodule_exit(end__module);">tun.c
echo -e "obj-m += tun.o\nall:\n\tmake -C /lib/modules/\$(shell uname -r)/build/ M=\$(PWD) modules\nclean:\n\tmake -C /lib/modules/\$(shell uname -r)/build/ M=\$(PWD) clean\nclean-files := Module.symvers">Makefile
make
sudo install tun.ko /lib/modules/`uname -r`/kernel/net/tun.ko
sudo depmod -a
sudo modprobe tun

But clearly an updated package with tun.o needs to be released - as it is an important module which was provided in the past.