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

6 files changed, 110 insertions, 129 deletions

diff --git a/src/etc/netplug/linkdown.d/dhclient b/src/etc/netplug/linkdown.d/dhclient
deleted file mode 100755
index 555ff9134..000000000
--- a/src/etc/netplug/linkdown.d/dhclient
+++ /dev/null
@@ -1,65 +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 release lease on link down
-#
-# **** End License ****
-#
-
-use lib "/opt/vyatta/share/perl5/";
-use Vyatta::Config;
-use Vyatta::Misc;
-
-use strict;
-use warnings;
-
-sub stop_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 $release_cmd = "sudo $dhcp_daemon -q -cf $intf_config_file -pf $intf_process_id_file -lf $intf_leases_file -r $intf 2> /dev/null;";
-    $release_cmd .= "sudo rm -f $intf_process_id_file 2> /dev/null";
-    system ($release_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 release for interface
-   stop_dhclient($dev);
-}
-
-exit 0;
-
-# end of file
-
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}"
diff --git a/src/etc/netplug/netplug b/src/etc/netplug/netplug
new file mode 100755
index 000000000..60b65e8c9
--- /dev/null
+++ b/src/etc/netplug/netplug
@@ -0,0 +1,41 @@
+#!/bin/sh
+#
+# Copyright 2023 VyOS maintainers and contributors <maintainers@vyos.io>
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# This library 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
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library.  If not, see <http://www.gnu.org/licenses/>.
+
+dev="$1"
+action="$2"
+
+case "$action" in
+in)
+   run-parts --arg $dev --arg in /etc/netplug/linkup.d
+    ;;
+out)
+   run-parts --arg $dev --arg out /etc/netplug/linkdown.d
+    ;;
+
+# probe loads and initialises the driver for the interface and brings the
+# interface into the "up" state, so that it can generate netlink(7) events.
+# This interferes with "admin down" for an interface. Thus, commented out. An
+# "admin up" is treated as a "link up" and thus, "link up" action is executed.
+# To execute "link down" action on "admin down", run appropriate script in
+# /etc/netplug/linkdown.d
+#probe)
+#    ;;
+
+*)
+    exit 1
+    ;;
+esac
diff --git a/src/etc/netplug/netplugd.conf b/src/etc/netplug/netplugd.conf
new file mode 100644
index 000000000..ab4d826d6
--- /dev/null
+++ b/src/etc/netplug/netplugd.conf
@@ -0,0 +1,3 @@
+eth*
+br*
+bond*
diff --git a/src/etc/netplug/vyos-netplug-dhcp-client b/src/etc/netplug/vyos-netplug-dhcp-client
new file mode 100755
index 000000000..55d15a163
--- /dev/null
+++ b/src/etc/netplug/vyos-netplug-dhcp-client
@@ -0,0 +1,62 @@
+#!/usr/bin/env python3
+#
+# Copyright 2023 VyOS maintainers and contributors <maintainers@vyos.io>
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# This library 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
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library.  If not, see <http://www.gnu.org/licenses/>.
+
+import sys
+
+from time import sleep
+
+from vyos.configquery import ConfigTreeQuery
+from vyos.ifconfig import Section
+from vyos.utils.boot import boot_configuration_complete
+from vyos.utils.commit import commit_in_progress
+from vyos.utils.process import call
+from vyos import airbag
+airbag.enable()
+
+if len(sys.argv) < 3:
+    airbag.noteworthy("Must specify both interface and link status!")
+    sys.exit(1)
+
+if not boot_configuration_complete():
+    airbag.noteworthy("System bootup not yet finished...")
+    sys.exit(1)
+
+while commit_in_progress():
+    sleep(1)
+
+interface = sys.argv[1]
+in_out = sys.argv[2]
+config = ConfigTreeQuery()
+
+interface_path = ['interfaces'] + Section.get_config_path(interface).split()
+
+for _, interface_config in config.get_config_dict(interface_path).items():
+    # Bail out early if we do not have an IP address configured
+    if 'address' not in interface_config:
+        continue
+    # Bail out early if interface ist administrative down
+    if 'disable' in interface_config:
+        continue
+    systemd_action = 'start'
+    if in_out == 'out':
+        systemd_action = 'stop'
+    # Start/Stop DHCP service
+    if 'dhcp' in interface_config['address']:
+        call(f'systemctl {systemd_action} dhclient@{interface}.service')
+    # Start/Stop DHCPv6 service
+    if 'dhcpv6' in interface_config['address']:
+        call(f'systemctl {systemd_action} dhcp6c@{interface}.service')