Comment 2 for bug 1885192

Reviewed: https://review.opendev.org/738116
Committed: https://git.openstack.org/cgit/openstack/charm-neutron-gateway/commit/?id=4bf26683d1c503f06dbf4776ece67f90970c0c21
Submitter: Zuul
Branch: master

commit 4bf26683d1c503f06dbf4776ece67f90970c0c21
Author: Mauricio Faria de Oliveira <email address hidden>
Date: Thu Jun 25 13:01:03 2020 -0300

    Add option to auto-load kernel modules for sysctl

    The nf_conntrack module is not loaded early enough on boot,
    thus when sysctl options are applied, its settings are not.

    This results in the correct sysctl settings seen on deploy
    time (because nf_conntrack was loaded previously by others)
    but not after reboot, despite configured in /etc/sysctl.d/.

    So, insert it in /etc/modules for module auto-load on boot
    (available on Trusty via /etc/init/kmod.conf, then Xenial+
    via systemd-sysctl.service).

    Since users can configure the sysctl option and thus need
    more modules, introduce the config option 'kernel-modules'
    (with 'nf_conntrack' as default.)

    It's handled before sysctl in the config-changed hook in
    case some sysctl option(s) needs not yet loaded module(s).

    In case of failure to load modules, log a warning message.

    Closes-Bug: #1885192
    Change-Id: I661a4fe2d9284455e536b073dc93696355baf122
    Signed-off-by: Mauricio Faria de Oliveira <email address hidden>