This file now only contains lines to disable netfilter on bridges.
In kernel 3.18 this filtering functionality was made non-default by
moving it to br_netfilter [https://bugzilla.redhat.com/show_bug.cgi?id=512206].
Aybody who actually wants to use br_netfilter has to load it explicitly
anyway, so disabling it through sysctl isn't necessary anymore.
The reason for removal is that by default (i.e. when br_netfilter is
not loaded), we get a warning on every boot:
systemd-sysctl[210]: Couldn't write '0' to 'net/bridge/bridge-nf-call-ip6tables', ignoring: No such file or directory
systemd-sysctl[210]: Couldn't write '0' to 'net/bridge/bridge-nf-call-iptables', ignoring: No such file or directory
systemd-sysctl[210]: Couldn't write '0' to 'net/bridge/bridge-nf-call-arptables', ignoring: No such file or directory
This is confusing for users and inelegant.
The downside of removing this file is for people who load br_netfilter
for some reason *and* do no want to use it, will have to take an
additional step now (either restore the sysctl settings or remove br_netfilter
from /etc/modules-load.d or wherever). I expect the number of people affected
to be very small.
(Note that the file was overwritten on sparc and s390, so those
architectures see no change.)