dns: T5959: Streamline dns forwarding service

Streamline configuration and operation of dns forwarding service in
following ways:

- Remove `dns_forwarding_reset.py` as its functionality is now covered
  by `dns.py`
- Adjust function names in `dns.py` to disambiguate between DNS
  forwarding and dynamic DNS
- Remove `dns_forwarding_restart.sh` as its functionality is inlined in
  `dns-forwarding.xml`
- Templatize systemd override for `pdns-recursor.service` and move the
  generated override files in /run. This ensures that the override files
  are always generated afresh after boot
- Simplify the systemd override file by removing the redundant overrides
- Relocate configuration path for pdns-recursor to `/run/pdns-recursor`
  and utilize the `RuntimeDirectory` default that pdns-recursor expects
- We do not need to use custom `--socket-dir` path anymore, the default
  path (viz., `/run/pdns-recursor` is fine)

(cherry picked from commit 1c1fb5fb4bd7c0d205b28caf90357ad56423464f)

3 files changed, 46 insertions, 80 deletions

diff --git a/src/op_mode/dns.py b/src/op_mode/dns.py
index 2168aef89..309bef3b9 100755
--- a/src/op_mode/dns.py
+++ b/src/op_mode/dns.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env python3
 #
-# Copyright (C) 2022 VyOS maintainers and contributors
+# Copyright (C) 2022-2024 VyOS maintainers and contributors
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License version 2 or later as
@@ -15,17 +15,16 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 
+import typing
 import sys
+import vyos.opmode
 
 from tabulate import tabulate
-
 from vyos.configquery import ConfigTreeQuery
-from vyos.utils.process import cmd
+from vyos.utils.process import cmd, rc_cmd
 
-import vyos.opmode
 
-
-def _data_to_dict(data, sep="\t") -> dict:
+def _forwarding_data_to_dict(data, sep="\t") -> dict:
     """
     Return dictionary from plain text
     separated by tab
@@ -52,15 +51,15 @@ def _data_to_dict(data, sep="\t") -> dict:
     return dictionary
 
 
-def _get_raw_forwarding_statistics() -> dict:
-    command = cmd('rec_control --socket-dir=/run/powerdns get-all')
-    data = _data_to_dict(command)
+def _get_forwarding_statistics_raw() -> dict:
+    command = cmd('rec_control get-all')
+    data = _forwarding_data_to_dict(command)
     data['cache-size'] = "{0:.2f}".format( int(
-        cmd('rec_control --socket-dir=/run/powerdns get cache-bytes')) / 1024 )
+        cmd('rec_control get cache-bytes')) / 1024 )
     return data
 
 
-def _get_formatted_forwarding_statistics(data):
+def _get_forwarding_statistics_formatted(data):
     cache_entries = data.get('cache-entries')
     max_cache_entries = data.get('max-cache-entries')
     cache_size = data.get('cache-size')
@@ -69,19 +68,48 @@ def _get_formatted_forwarding_statistics(data):
     output = tabulate(data_entries, headers, numalign="left")
     return output
 
+def _verify_forwarding(func):
+    """Decorator checks if DNS Forwarding config exists"""
+    from functools import wraps
 
-def show_forwarding_statistics(raw: bool):
-
-    config = ConfigTreeQuery()
-    if not config.exists('service dns forwarding'):
-        raise vyos.opmode.UnconfiguredSubsystem('DNS forwarding is not configured')
+    @wraps(func)
+    def _wrapper(*args, **kwargs):
+        config = ConfigTreeQuery()
+        if not config.exists('service dns forwarding'):
+            raise vyos.opmode.UnconfiguredSubsystem('DNS Forwarding is not configured')
+        return func(*args, **kwargs)
+    return _wrapper
 
-    dns_data = _get_raw_forwarding_statistics()
+@_verify_forwarding
+def show_forwarding_statistics(raw: bool):
+    dns_data = _get_forwarding_statistics_raw()
     if raw:
         return dns_data
     else:
-        return _get_formatted_forwarding_statistics(dns_data)
+        return _get_forwarding_statistics_formatted(dns_data)
 
+@_verify_forwarding
+def reset_forwarding(all: bool, domain: typing.Optional[str]):
+    """
+    Reset DNS Forwarding cache
+
+    :param all (bool): reset cache all domains
+    :param domain (str): reset cache for specified domain
+    """
+    if all:
+        rc, output = rc_cmd('rec_control wipe-cache ".$"')
+        if rc != 0:
+            print(output)
+            return None
+        print('DNS Forwarding cache reset for all domains!')
+        return output
+    elif domain:
+        rc, output = rc_cmd(f'rec_control wipe-cache "{domain}$"')
+        if rc != 0:
+            print(output)
+            return None
+        print(f'DNS Forwarding cache reset for domain "{domain}"!')
+        return output
 
 if __name__ == '__main__':
     try:
diff --git a/src/op_mode/dns_forwarding_reset.py b/src/op_mode/dns_forwarding_reset.py
deleted file mode 100755
index 55e20918f..000000000
--- a/src/op_mode/dns_forwarding_reset.py
+++ /dev/null
@@ -1,54 +0,0 @@
-#!/usr/bin/env python3
-#
-# Copyright (C) 2018 VyOS maintainers and contributors
-#
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License version 2 or later 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.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-#
-# File: vyos-show-version
-# Purpose:
-#    Displays image version and system information.
-#    Used by the "run show version" command.
-
-
-import os
-import argparse
-
-from sys import exit
-from vyos.config import Config
-from vyos.utils.process import call
-
-PDNS_CMD='/usr/bin/rec_control --socket-dir=/run/powerdns'
-
-parser = argparse.ArgumentParser()
-parser.add_argument("-a", "--all", action="store_true", help="Reset all cache")
-parser.add_argument("domain", type=str, nargs="?", help="Domain to reset cache entries for")
-
-if __name__ == '__main__':
-    args = parser.parse_args()
-
-    # Do nothing if service is not configured
-    c = Config()
-    if not c.exists_effective(['service', 'dns', 'forwarding']):
-        print("DNS forwarding is not configured")
-        exit(0)
-
-    if args.all:
-        call(f"{PDNS_CMD} wipe-cache \'.$\'")
-        exit(0)
-
-    elif args.domain:
-        call(f"{PDNS_CMD} wipe-cache \'{0}$\'".format(args.domain))
-
-    else:
-        parser.print_help()
-        exit(1)
diff --git a/src/op_mode/dns_forwarding_restart.sh b/src/op_mode/dns_forwarding_restart.sh
deleted file mode 100755
index 64cc92115..000000000
--- a/src/op_mode/dns_forwarding_restart.sh
+++ /dev/null
@@ -1,8 +0,0 @@
-#!/bin/sh
-
-if cli-shell-api existsEffective service dns forwarding; then
-    echo "Restarting the DNS forwarding service"
-    systemctl restart pdns-recursor.service
-else
-    echo "DNS forwarding is not configured"
-fi