netplug: T5476: rewrite dhclient helper from Perl -> Python

There are two hooks called for bridge, ethernet and bond interfaces if the
link-state changes up -> down or down -> up.

The helpers are:
* /etc/netplug/linkdown.d/dhclient
* /etc/netplug/linkup.d/dhclient

As those helpers use Linux actions to start/restart the dhclient process in
Perl it's time to rewrite it. First goal is to get rid of all Perl code and the
second is that we now have a Proper Python library. Instead of checking if the
process is running the then restarting it without even systemd noticing
(yeah we might get two processes beeing alive) we should:

* Add a Python helper that can be used for both up and down (see man 8 netplugd
  FILES section)
* Query the VyOS CLI config if the interface in question has DHCP(v6)
  configured and is not disabled
* Add IPv6 DHCPv6 support

MAN page: https://linux.die.net/man/8/netplugd

2 files changed, 4 insertions, 64 deletions

diff --git a/src/etc/netplug/linkup.d/dhclient b/src/etc/netplug/linkup.d/dhclient
deleted file mode 100755
index 8e50715fd..000000000
--- a/src/etc/netplug/linkup.d/dhclient
+++ /dev/null
@@ -1,64 +0,0 @@
-#!/usr/bin/perl
-#
-# Module: dhclient
-#
-# **** License ****
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License version 2 as
-# published by the Free Software Foundation.
-#
-# This program is distributed in the hope that it will be useful, but
-# WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-# General Public License for more details.
-#
-# A copy of the GNU General Public License is available as
-# `/usr/share/common-licenses/GPL' in the Debian GNU/Linux distribution
-# or on the World Wide Web at `http://www.gnu.org/copyleft/gpl.html'.
-# You can also obtain it by writing to the Free Software Foundation,
-# Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
-# MA 02110-1301, USA.
-#
-# This code was originally developed by Vyatta, Inc.
-# Portions created by Vyatta are Copyright (C) 2008 Vyatta, Inc.
-# All Rights Reserved.
-#
-# Author: Mohit Mehta
-# Date: November 2008
-# Description: Script to renew lease on link up
-#
-# **** End License ****
-#
-
-use lib "/opt/vyatta/share/perl5/";
-use Vyatta::Config;
-use Vyatta::Misc;
-
-use strict;
-use warnings;
-
-sub run_dhclient {
-    my $intf = shift;
-    my $dhcp_daemon = '/sbin/dhclient';
-    my ($intf_config_file, $intf_process_id_file, $intf_leases_file) = Vyatta::Misc::generate_dhclient_intf_files($intf);
-    my $cmd = "sudo $dhcp_daemon -pf $intf_process_id_file -x $intf 2> /dev/null; sudo rm -f $intf_process_id_file 2> /dev/null;";
-    $cmd .= "sudo $dhcp_daemon -q -nw -cf $intf_config_file -pf $intf_process_id_file  -lf $intf_leases_file $intf 2> /dev/null &";
-    system ($cmd);
-}
-
-#
-# main
-#
-
-my $dev=shift;
-
-# only do this if interface is configured to use dhcp for getting IP address
-if (Vyatta::Misc::is_dhcp_enabled($dev, "outside_cli")) {
-   # do a dhcp lease renew for interface
-   run_dhclient($dev);
-}
-
-exit 0;
-
-# end of file
-
diff --git a/src/etc/netplug/linkup.d/vyos-python-helper b/src/etc/netplug/linkup.d/vyos-python-helper
new file mode 100755
index 000000000..9c59c58ad
--- /dev/null
+++ b/src/etc/netplug/linkup.d/vyos-python-helper
@@ -0,0 +1,4 @@
+#!/bin/sh
+PYTHON3=$(which python3)
+# Call the real python script and forward commandline arguments
+$PYTHON3 /etc/netplug/vyos-netplug-dhcp-client "${@:1}"