syslog: T6719: fix the behavior of "syslog global preserve-fqdn"

(cherry picked from commit c196c6d)

data/templates/rsyslog/rsyslog.conf.j2

@@ -10,6 +10,10 @@ $MarkMessagePeriod {{ global.marker.interval }}
 $PreserveFQDN on
 {% endif %}
 
+{% if global.local_host_name is vyos_defined %}
+$LocalHostName {{ global.local_host_name }}
+{% endif %}
+
 # We always log to /var/log/messages
 $outchannel global,/var/log/messages,262144,/usr/sbin/logrotate {{ logrotate }}
 {% if global.facility is vyos_defined %}

smoketest/scripts/cli/test_system_syslog.py

@@ -20,6 +20,7 @@
 from base_vyostest_shim import VyOSUnitTestSHIM
 
 from vyos.utils.file import read_file
+from vyos.utils.process import cmd
 from vyos.utils.process import process_named_running
 
 PROCESS_NAME = 'rsyslogd'
@@ -61,19 +62,45 @@ def test_syslog_basic(self):
         self.cli_set(base_path + ['host', host2, 'facility', 'kern', 'level', 'err'])
         self.cli_set(base_path + ['console', 'facility', 'all', 'level', 'warning'])
 
-
         self.cli_commit()
         # verify log level and facilities in config file
         # *.warning /dev/console
         # *.* @198.51.100.1:999
         # kern.err @192.0.2.1:514
-        config = [get_config_value('\*.\*'), get_config_value('kern.err'), get_config_value('\*.warning')]
+        config = [
+            get_config_value('\*.\*'),
+            get_config_value('kern.err'),
+            get_config_value('\*.warning'),
+        ]
         expected = [f'@{host1}:999', f'@{host2}:514', '/dev/console']
 
-        for i in range(0,3):
+        for i in range(0, 3):
             self.assertIn(expected[i], config[i])
         # Check for running process
         self.assertTrue(process_named_running(PROCESS_NAME))
 
+    def test_syslog_global(self):
+        self.cli_set(['system', 'host-name', 'vyos'])
+        self.cli_set(['system', 'domain-name', 'example.local'])
+        self.cli_set(base_path + ['global', 'marker', 'interval', '600'])
+        self.cli_set(base_path + ['global', 'preserve-fqdn'])
+        self.cli_set(base_path + ['global', 'facility', 'kern', 'level', 'err'])
+
+        self.cli_commit()
+
+        config = cmd(f'sudo cat {RSYSLOG_CONF}')
+        expected = [
+            '$MarkMessagePeriod 600',
+            '$PreserveFQDN on',
+            'kern.err',
+            '$LocalHostName vyos.example.local',
+        ]
+
+        for e in expected:
+            self.assertIn(e, config)
+        # Check for running process
+        self.assertTrue(process_named_running(PROCESS_NAME))
+
+
 if __name__ == '__main__':
     unittest.main(verbosity=2)

src/conf_mode/system_syslog.py

@@ -52,6 +52,17 @@ def get_config(config=None):
     if syslog.from_defaults(['global']):
         del syslog['global']
 
+    if (
+        'global' in syslog
+        and 'preserve_fqdn' in syslog['global']
+        and conf.exists(['system', 'host-name'])
+        and conf.exists(['system', 'domain-name'])
+    ):
+        hostname = conf.return_value(['system', 'host-name'])
+        domain = conf.return_value(['system', 'domain-name'])
+        fqdn = f'{hostname}.{domain}'
+        syslog['global']['local_host_name'] = fqdn
+
     return syslog
 
 def verify(syslog):