system: op-mode: T3334: allow delayed getty restart when configuring …

…serial ports

* Relocated service control to op-mode command "restart serial-console"
* Checking for logged-in serial sessions that may be affected by getty reconfig
* Warning the user when changes are committed and serial sessions are active,
  otherwise restart services as normal. No prompts issued during commit,
  all config gen/commit steps still occur except for the service restarts
  (everything remains consistent)
* To apply committed changes, user will need to run "restart serial-console"
  to complete the process or reboot the whole router

op-mode-definitions/restart-serial.xml.in

@@ -0,0 +1,13 @@
+<?xml version="1.0"?>
+<interfaceDefinition>
+  <node name="restart">
+    <children>
+      <node name="serial-console">
+        <properties>
+          <help>Restart serial console service</help>
+        </properties>
+        <command>${vyos_op_scripts_dir}/restart_serial.py</command>
+      </node>
+    </children>
+  </node>
+</interfaceDefinition>

src/conf_mode/system_console.py

@@ -74,7 +74,6 @@ def generate(console):
     for root, dirs, files in os.walk(base_dir):
         for basename in files:
             if 'serial-getty' in basename:
-                call(f'systemctl stop {basename}')
                 os.unlink(os.path.join(root, basename))
 
     if not console or 'device' not in console:
@@ -129,12 +128,8 @@ def apply(console):
         # Configure screen blank powersaving on VGA console
         call('/usr/bin/setterm -blank 15 -powersave powerdown -powerdown 60 -term linux </dev/tty1 >/dev/tty1 2>&1')
 
-    # Start getty process on configured serial interfaces
-    for device in console['device']:
-        # Only start console if it exists on the running system. If a user
-        # detaches a USB serial console and reboots - it should not fail!
-        if os.path.exists(f'/dev/{device}'):
-            call(f'systemctl restart serial-getty@{device}.service')
+    # Service control moved to op_mode/restart_serial.py to unify checks and prompts. 
+    call('/usr/libexec/vyos/op_mode/restart_serial.py --quiet')
 
     return None
 

src/op_mode/restart_serial.py

@@ -0,0 +1,83 @@
+#!/usr/bin/env python3
+#
+# Copyright (C) 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
+# 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/>.
+
+import sys, os, re, json
+
+from vyos.base import Warning
+from vyos.utils.io import ask_yes_no
+from vyos.utils.process import cmd
+
+GLOB_GETTY_UNITS = 'serial-getty@*.service'
+RE_GETTY_DEVICES = re.compile(r'.+@(.+).service$')
+
+SD_UNIT_PATH = '/run/systemd/system'
+UTMP_PATH = '/run/utmp'
+
+def get_serial_units():
+    # Since we cannot depend on the current config for decommissioned ports, 
+    # we just grab everything that systemd knows about. 
+    tmp = cmd(f'sudo systemctl list-units {GLOB_GETTY_UNITS} --all --output json --no-pager')
+    getty_units = json.loads(tmp)
+
+    for sdunit in getty_units:
+        m = RE_GETTY_DEVICES.search(sdunit['unit'])
+        if m is None:
+            Warning(f'Serial console unit name "{sdunit["unit"]}" is malformed and cannot be checked for activity!')
+        else:
+            sdunit['device'] = m.group(1)
+
+    return getty_units
+
+def get_connected_ports(units):
+    connected = []
+
+    ports = [ x['device'] for x in units if 'device' in x ]
+    for line in cmd(f'utmpdump {UTMP_PATH}').splitlines():
+        row = line.split('] [')
+        user_name = row[3].strip()
+        user_term = row[4].strip()
+        if user_name and user_name != 'LOGIN' and user_term in ports:
+            connected.append(user_term)
+
+    return connected
+
+if __name__ == '__main__':
+    no_prompt = '--quiet' in sys.argv # don't need a full argparse for this. 
+    units = get_serial_units()
+    connected = get_connected_ports(units)
+
+    if connected:
+        print('There are user sessions connected via serial console that will be terminated\n' \
+              'when serial console settings are changed.\n') # extra newline is deliberate. 
+
+        if no_prompt:
+            # This flag is used by conf_mode/system_console.py to reset things, if there's
+            # a problem, the user should issue a manual restart for serial-getty. 
+            print('Please ensure all settings are committed and saved before issuing a\n' \
+                  '"restart serial-console" command to apply new configuration.')
+            sys.exit(0)
+
+        if not ask_yes_no('Any uncommitted changes from these sessions will be lost and in-progress actions\n' \
+                          'may be left in an inconsistent state. Continue?'):
+            sys.exit(1)
+
+    for unit in units:
+        unit_name = unit['unit']
+        if os.path.exists(os.path.join(SD_UNIT_PATH, unit_name)):
+            cmd(f'sudo systemctl restart {unit_name}')
+        else:
+            # Deleted stubs don't need to be restarted, just shut them down.
+            cmd(f'sudo systemctl stop {unit_name}')