We are using Zentyal 3.1 (Ubuntu 12.04.2 LTS - kernel version: 188.8.131.52-generic) as proxy/firewall for our location. At the moment the firewall rules are set to allow all, however sip packets are still dropped. This is caused by the module nf_conntrack_sip.
When I manually unload the module + the module nf_nat_sip everything works as expected. The command I used for unloading is either (both work):
rmmod nf_nat_sip rmmod nf_conntrack_sip
modprobe -r nf_nat_sip modprobe -r nf_conntrack_sip
After a reboot ofcourse these modules are loaded again, so I added following lines to /etc/modprobe.d/blacklist.conf
blacklist nf_nat_sip blacklist nf_conntrack_sip
But this didn't prevent the modules from loading. I even created a new file, /etc/modprobe.d/blacklist-custom.conf with the same two lines (and a blank new line), but the modules still get loaded at boot.
Then I tried a script that unloads the modules in upstart after the network devices come up, and that works. But after some time the modules do get loaded again by some unknown trigger.
I want these modules unloaded permanently, but kinda clueless atm on any other solutions.