syslog: T5367: add format option to include timezone in message

Add CLI option to include the systems timezone in the syslog message sent to
a collector. This can be enabled using:

  set system syslog host <hostname> format include-timezone

data/templates/rsyslog/rsyslog.conf.j2

@@ -54,12 +54,10 @@ $outchannel {{ file_name }},/var/log/user/{{ file_name }},{{ file_options.archiv
 {%         endif %}
 {%         if host_options.protocol is vyos_defined('tcp') %}
 {%             if host_options.format.octet_counted is vyos_defined %}
-{{ tmp | join(';') }} @@(o){{ host_name | bracketize_ipv6 }}:{{ host_options.port }};RSYSLOG_SyslogProtocol23Format
-{%             else %}
-{{ tmp | join(';') }} @@{{ host_name | bracketize_ipv6 }}:{{ host_options.port }}
+{{ tmp | join(';') }} @@{{ '(o)' if host_options.format.octet_counted is vyos_defined }}{{ host_name | bracketize_ipv6 }}:{{ host_options.port }}{{ ';RSYSLOG_SyslogProtocol23Format' if host_options.format.include_timezone is vyos_defined }}
 {%             endif %}
 {%         else %}
-{{ tmp | join(';') }} @{{ host_name | bracketize_ipv6 }}:{{ host_options.port }}{{ ';RSYSLOG_SyslogProtocol23Format' if host_options.format.octet_counted is vyos_defined }}
+{{ tmp | join(';') }} @{{ host_name | bracketize_ipv6 }}:{{ host_options.port }}{{ ';RSYSLOG_SyslogProtocol23Format' if host_options.format.include_timezone is vyos_defined }}
 {%         endif %}
 {%     endfor %}
 {% endif %}

interface-definitions/system_syslog.xml.in

@@ -66,6 +66,12 @@
                       <valueless/>
                     </properties>
                   </leafNode>
+                  <leafNode name="include-timezone">
+                    <properties>
+                      <help>Include system timezone in syslog message</help>
+                      <valueless/>
+                    </properties>
+                  </leafNode>
                 </children>
               </node>
             </children>

src/conf_mode/system_syslog.py

@@ -1,6 +1,6 @@
 #!/usr/bin/env python3
 #
-# Copyright (C) 2018-2023 VyOS maintainers and contributors
+# Copyright (C) 2018-2024 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
@@ -18,6 +18,7 @@
 
 from sys import exit
 
+from vyos.base import Warning
 from vyos.config import Config
 from vyos.configdict import is_node_changed
 from vyos.configverify import verify_vrf
@@ -58,6 +59,12 @@ def verify(syslog):
     if not syslog:
         return None
 
+    if 'host' in syslog:
+         for host, host_options in syslog['host'].items():
+             if 'protocol' in host_options and host_options['protocol'] == 'udp':
+                 if 'format' in host_options and 'octet_counted' in host_options['format']:
+                     Warning(f'Syslog UDP transport for "{host}" should not use octet-counted format!')
+
     verify_vrf(syslog)
 
 def generate(syslog):