[pd] add pd daemon service to support the automation of dhcpcd PD man…

…agement (openthread#2360)

The changes include:
- PD daemon (dhcp6_pd_daemon.py) to monitor and react to PD state
  changes between running and stopped/disabled.
- Creation of systemd service file (dhcp6_pd_daemon.service) for
  managing the daemon.
- Update of _dhcpv6_pd_ref to support pd daemon installation and
  uninstallation

This scripts essentially automate the process of setting up a machine
as a dhcpcd pd reference device, handling prefix delegation.

script/_dhcpv6_pd_ref

@@ -30,39 +30,115 @@
 #       This script manipulates DHCPv6-PD-REF configuration.
 #
 
-customise_dhcpcd_conf()
+# TODO: set the upstream interface according to the environment variables of `script/setup`.
+UPSTREAM_INTERFACE="eth0"
+
+DHCPCD_ENTER_HOOK="/etc/dhcpcd.enter-hook"
+DHCPCD_EXIT_HOOK="/etc/dhcpcd.exit-hook"
+
+PD_DAEMON_DIR="/opt/pd-daemon"
+PD_DAEMON_PATH="${PD_DAEMON_DIR}/dhcp6_pd_daemon.py"
+PD_DAEMON_SERVICE_NAME="dhcp6_pd_daemon.service"
+PD_DAEMON_SERVICE_PATH="/etc/systemd/system/${PD_DAEMON_SERVICE_NAME}"
+
+DHCP_CONFIG_PATH="/etc/dhcpcd.conf"
+DHCP_CONFIG_ORIG_PATH="/etc/dhcpcd.conf.orig"
+DHCP_CONFIG_PD_PATH="/etc/dhcpcd.conf.pd"
+DHCP_CONFIG_NO_PD_PATH="/etc/dhcpcd.conf.no-pd"
+
+# Create dhcpcd configuration file with ipv6 prefix request.
+create_dhcpcd_conf_pd()
 {
-    # This has to be run after script/_border_routing, and this will
-    # invalidate all changes to dhcpcd.conf made by script/_border_routing.
-    sudo tee /etc/dhcpcd.conf >/dev/null <<EOF
+    sudo tee ${DHCP_CONFIG_PD_PATH} >/dev/null <<EOF
 noipv6rs # disable router solicitation
-interface eth0
+interface ${UPSTREAM_INTERFACE}
   iaid 1
   ia_pd 2/::/64 -
+release
+# Disable Router Solicitations (RS) again, specifically for ${UPSTREAM_INTERFACE}.
+# This ensures that accept_ra is prevented from being set to 0, allowing
+# the interface to accepting Router Advertisements and configuring IPv6
+# based on them. The exact reason for requiring 'noipv6rs' twice
+# is not fully understood but has been observed to be necessary through 
+# experimentation.
+noipv6rs
+EOF
+}
+
+# Create dhcpcd configuration file with no prefix request.
+create_dhcpcd_conf_no_pd()
+{
+    sudo tee ${DHCP_CONFIG_NO_PD_PATH} >/dev/null <<EOF
+noipv6rs # disable router solicitation
+EOF
+}
+
+create_dhcp6_pd_daemon_service()
+{
+    sudo tee ${PD_DAEMON_SERVICE_PATH} <<EOF
+[Unit]
+Description=Daemon to manage dhcpcd based on otbr-agent's PD state change
+After=multi-user.service
+ConditionPathExists=${PD_DAEMON_PATH}
+
+[Service]
+Type=simple
+User=root
+ExecStart=/usr/bin/python3 ${PD_DAEMON_PATH}
+Restart=on-failure
+
+[Install]
+WantedBy=multi-user.target
 EOF
 }
 
 dhcpv6_pd_ref_uninstall()
 {
     with DHCPV6_PD_REF || return 0
 
-    if [[ -f "/etc/dhcpcd.conf.orig" ]]; then
-        sudo mv /etc/dhcpcd.conf.orig /etc/dhcpcd.conf
+    if have systemctl; then
+        sudo systemctl disable ${PD_DAEMON_SERVICE_NAME} || true
+        sudo systemctl stop ${PD_DAEMON_SERVICE_NAME} || true
+        sudo rm -f ${PD_DAEMON_SERVICE_PATH} || true
     fi
-    sudo systemctl restart dhcpcd
-    sudo rm -f /etc/dhcpcd.enter-hook /etc/dhcpcd.exit-hook
 
+    if [[ -f ${DHCP_CONFIG_ORIG_PATH} ]]; then
+        sudo mv ${DHCP_CONFIG_ORIG_PATH} ${DHCP_CONFIG_PATH}
+    fi
+
+    sudo rm -f ${DHCPCD_ENTER_HOOK} ${DHCPCD_EXIT_HOOK}
+    sudo rm -f ${PD_DAEMON_PATH}
+
+    if have systemctl; then
+        sudo systemctl daemon-reload
+
+        if systemctl is-active dhcpcd; then
+            sudo systemctl restart dhcpcd || true
+        fi
+    fi
 }
 
 dhcpv6_pd_ref_install()
 {
     with DHCPV6_PD_REF || return 0
 
-    if [[ -f "/etc/dhcpcd.conf" ]]; then
-        sudo mv /etc/dhcpcd.conf /etc/dhcpcd.conf.orig
+    if [[ -f ${DHCP_CONFIG_PATH} ]]; then
+        sudo mv ${DHCP_CONFIG_PATH} ${DHCP_CONFIG_ORIG_PATH}
     fi
-    customise_dhcpcd_conf
+
     # Add dhcpcd.hooks
-    sudo install -m 755 "$(dirname "$0")"/reference-device/dhcpcd.enter-hook /etc/dhcpcd.enter-hook
-    sudo install -m 755 "$(dirname "$0")"/reference-device/dhcpcd.exit-hook /etc/dhcpcd.exit-hook
+    sudo install -m 755 "$(dirname "$0")"/reference-device/dhcpcd.enter-hook ${DHCPCD_ENTER_HOOK}
+    sudo install -m 755 "$(dirname "$0")"/reference-device/dhcpcd.exit-hook ${DHCPCD_EXIT_HOOK}
+    sudo mkdir -p ${PD_DAEMON_DIR}
+    sudo install -m 755 "$(dirname "$0")"/reference-device/dhcp6_pd_daemon.py ${PD_DAEMON_PATH}
+
+    create_dhcpcd_conf_pd
+    create_dhcpcd_conf_no_pd
+    create_dhcp6_pd_daemon_service
+
+    if have systemctl; then
+        sudo systemctl daemon-reload
+        sudo systemctl enable ${PD_DAEMON_SERVICE_NAME}
+        sudo systemctl start ${PD_DAEMON_SERVICE_NAME}
+    fi
 }

script/reference-device/dhcp6_pd_daemon.py

@@ -0,0 +1,143 @@
+#!/usr/bin/env python3
+#
+#  Copyright (c) 2024, The OpenThread Authors.
+#  All rights reserved.
+#
+#  Redistribution and use in source and binary forms, with or without
+#  modification, are permitted provided that the following conditions are met:
+#  1. Redistributions of source code must retain the above copyright
+#     notice, this list of conditions and the following disclaimer.
+#  2. Redistributions in binary form must reproduce the above copyright
+#     notice, this list of conditions and the following disclaimer in the
+#     documentation and/or other materials provided with the distribution.
+#  3. Neither the name of the copyright holder nor the
+#     names of its contributors may be used to endorse or promote products
+#     derived from this software without specific prior written permission.
+#
+#  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+#  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+#  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+#  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+#  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+#  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+#  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+#  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+#  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+#  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+#  POSSIBILITY OF SUCH DAMAGE.
+#
+
+import logging
+import dbus
+import gi.repository.GLib as GLib
+import subprocess
+import threading
+import os
+
+from dbus.mainloop.glib import DBusGMainLoop
+
+DBusGMainLoop(set_as_default=True)
+
+logging.basicConfig(level=logging.INFO,
+                    format='%(asctime)s - %(levelname)s - %(message)s')
+
+bus = dbus.SystemBus()
+intended_dhcp6pd_state = None
+
+DHCP_CONFIG_PATH = "/etc/dhcpcd.conf"
+DHCP_CONFIG_PD_PATH = "/etc/dhcpcd.conf.pd"
+DHCP_CONFIG_NO_PD_PATH = "/etc/dhcpcd.conf.no-pd"
+
+
+def restart_dhcpcd_service(config_path):
+    if not os.path.isfile(config_path):
+        logging.error(f"{config_path} not found. Cannot apply configuration.")
+        return
+    try:
+        subprocess.run(["sudo", "cp", config_path, DHCP_CONFIG_PATH],
+                       check=True)
+        subprocess.run(["sudo", "systemctl", "daemon-reload"], check=True)
+        subprocess.run(["sudo", "service", "dhcpcd", "restart"], check=True)
+        logging.info(
+            f"Successfully restarted dhcpcd service with {config_path}.")
+    except subprocess.CalledProcessError as e:
+        logging.error(f"Error restarting dhcpcd service: {e}")
+
+
+def restart_dhcpcd_with_pd_config():
+    global intended_dhcp6pd_state
+    restart_dhcpcd_service(DHCP_CONFIG_PD_PATH)
+    intended_dhcp6pd_state = None
+
+
+def restart_dhcpcd_with_no_pd_config():
+    restart_dhcpcd_service(DHCP_CONFIG_NO_PD_PATH)
+
+
+def properties_changed_handler(interface_name, changed_properties,
+                               invalidated_properties):
+    global intended_dhcp6pd_state
+    if "Dhcp6PdState" not in changed_properties:
+        return
+    new_state = changed_properties["Dhcp6PdState"]
+    logging.info(f"Dhcp6PdState changed to: {new_state}")
+    if new_state == "running" and intended_dhcp6pd_state != "running":
+        intended_dhcp6pd_state = "running"
+        thread = threading.Thread(target=restart_dhcpcd_with_pd_config)
+        thread.start()
+    elif new_state in ("stopped", "idle",
+                       "disabled") and intended_dhcp6pd_state is None:
+        restart_dhcpcd_with_no_pd_config()
+
+
+def connect_to_signal():
+    try:
+        dbus_obj = bus.get_object('io.openthread.BorderRouter.wpan0',
+                                  '/io/openthread/BorderRouter/wpan0')
+        properties_dbus_iface = dbus.Interface(
+            dbus_obj, 'org.freedesktop.DBus.Properties')
+        dbus_obj.connect_to_signal(
+            "PropertiesChanged",
+            properties_changed_handler,
+            dbus_interface=properties_dbus_iface.dbus_interface)
+        logging.info("Connected to D-Bus signal.")
+        return dbus_obj
+    except dbus.DBusException as e:
+        logging.error(f"Error connecting to D-Bus: {e}")
+        return None
+
+
+def check_and_reconnect(dbus_obj):
+    if dbus_obj is None:
+        connect_to_signal()
+
+
+def main():
+    # Ensure dhcpcd is running in its last known state. This addresses a potential race condition
+    # during system startup due to the loop dependency in dhcpcd-radvd-network.target.
+    #
+    #   - network.target activation relies on the completion of dhcpcd start
+    #   - during bootup, dhcpcd tries to start radvd with PD enabled before network.target is
+    #     active, which leads to a timeout failure
+    #   - so we will prevent radvd from starting before target.network is active
+    #
+    # By restarting dhcpcd here, we ensure it runs after network.target is active, allowing
+    # radvd to start correctly and dhcpcd to configure the interface.
+    try:
+        subprocess.run(["sudo", "systemctl", "reload-or-restart", "dhcpcd"],
+                       check=True)
+        logging.info("Successfully restarting dhcpcd service.")
+    except subprocess.CalledProcessError as e:
+        logging.error(f"Error restarting dhcpcd service: {e}")
+
+    loop = GLib.MainLoop()
+
+    thread_dbus_obj = connect_to_signal()
+
+    GLib.timeout_add_seconds(5, check_and_reconnect, thread_dbus_obj)
+
+    loop.run()
+
+
+if __name__ == '__main__':
+    main()

script/reference-device/dhcpcd.enter-hook

@@ -67,9 +67,16 @@ if [ ${interface} = ${UPSTREAM_INTERFACE} ]; then
 
     case $reason in
         DELEGATED6 | REBIND6 | RENEW6 | BOUND6 )
-            logger "$LOG_TAG prefix is $new_dhcp6_ia_pd1_prefix1  length is $new_dhcp6_ia_pd1_prefix1_length pltime is  $new_dhcp6_ia_pd1_prefix1_pltime vltime is $new_dhcp6_ia_pd1_prefix1_vltime"
-            config_ra $new_dhcp6_ia_pd1_prefix1 $new_dhcp6_ia_pd1_prefix1_length $new_dhcp6_ia_pd1_prefix1_pltime  $new_dhcp6_ia_pd1_prefix1_vltime
-            sudo systemctl reload radvd || logger "$LOG_TAG Failed to reload radvd"
+            if [ -z "$new_dhcp6_ia_pd1_prefix1" ] || [ -z "$new_dhcp6_ia_pd1_prefix1_length" ] || \
+               [ -z "$new_dhcp6_ia_pd1_prefix1_pltime" ] || [ -z "$new_dhcp6_ia_pd1_prefix1_vltime" ]; then
+                logger "$LOG_TAG WARNING: Missing DHCPv6 prefix information. Skipping radvd configuration."
+            else
+                logger "$LOG_TAG prefix is $new_dhcp6_ia_pd1_prefix1  length is $new_dhcp6_ia_pd1_prefix1_length pltime is  $new_dhcp6_ia_pd1_prefix1_pltime vltime is $new_dhcp6_ia_pd1_prefix1_vltime"
+                config_ra $new_dhcp6_ia_pd1_prefix1 $new_dhcp6_ia_pd1_prefix1_length $new_dhcp6_ia_pd1_prefix1_pltime  $new_dhcp6_ia_pd1_prefix1_vltime
+                if systemctl is-active network.target; then
+                    sudo systemctl reload-or-restart radvd || logger "$LOG_TAG Failed to reload radvd"
+                fi
+            fi
             ;;
     esac
 fi

script/reference-device/dhcpcd.exit-hook

@@ -66,9 +66,14 @@ if [ ${interface} = ${UPSTREAM_INTERFACE} ]; then
 
     case $reason in
         EXPIRE6 | STOP6)
-            config_ra $old_dhcp6_ia_pd1_prefix1 $old_dhcp6_ia_pd1_prefix1_length 0 0
-            sudo systemctl reload radvd
+            if [ -z "$old_dhcp6_ia_pd1_prefix1" ] || [ -z "$old_dhcp6_ia_pd1_prefix1_length" ]; then
+                logger "$LOG_TAG WARNING: Missing DHCPv6 prefix information. Skipping radvd configuration."
+            else
+                config_ra $old_dhcp6_ia_pd1_prefix1 $old_dhcp6_ia_pd1_prefix1_length 0 0
+                if systemctl is-active network.target; then
+                    sudo systemctl reload-or-restart radvd
+                fi
+            fi
             ;;
     esac
 fi
-