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

* Created op-mode command "restart serial console"
* Relocated service control to vyos.utils.serial helpers, used by conf- and
  op-mode serial console handling
  * 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
  * Added additional flags and target filtering for generic use of helpers.

3 files changed, 70 insertions, 8 deletions

diff --git a/src/completion/list_login_ttys.py b/src/completion/list_login_ttys.py
new file mode 100644
index 000000000..4d77a1b8b
--- /dev/null
+++ b/src/completion/list_login_ttys.py
@@ -0,0 +1,25 @@
+#!/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/>.
+
+from vyos.utils.serial import get_serial_units
+
+if __name__ == '__main__':
+    # Autocomplete uses runtime state rather than the config tree, as a manual 
+    # restart/cleanup may be needed for deleted devices. 
+    tty_completions = [ '<text>' ] + [ x['device'] for x in get_serial_units() if 'device' in x ]
+    print(' '.join(tty_completions))
+
+
diff --git a/src/conf_mode/system_console.py b/src/conf_mode/system_console.py
index 19bbb8875..27bf92e0b 100755
--- a/src/conf_mode/system_console.py
+++ b/src/conf_mode/system_console.py
@@ -19,8 +19,10 @@ from pathlib import Path
 
 from vyos.config import Config
 from vyos.utils.process import call
+from vyos.utils.serial import restart_login_consoles
 from vyos.system import grub_util
 from vyos.template import render
+from vyos.defaults import directories
 from vyos import ConfigError
 from vyos import airbag
 airbag.enable()
@@ -74,7 +76,6 @@ 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:
@@ -122,6 +123,11 @@ def apply(console):
     # Reload systemd manager configuration
     call('systemctl daemon-reload')
 
+    # Service control moved to vyos.utils.serial to unify checks and prompts. 
+    # If users are connected, we want to show an informational message on completing 
+    # the process, but not halt configuration processing with an interactive prompt. 
+    restart_login_consoles(prompt_user=False, quiet=False)
+
     if not console:
         return None
 
@@ -129,13 +135,6 @@ 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')
-
     return None
 
 if __name__ == '__main__':
diff --git a/src/op_mode/serial.py b/src/op_mode/serial.py
new file mode 100644
index 000000000..a5864872b
--- /dev/null
+++ b/src/op_mode/serial.py
@@ -0,0 +1,38 @@
+#!/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, typing
+
+import vyos.opmode
+from vyos.utils.serial import restart_login_consoles as _restart_login_consoles
+
+def restart_console(device_name: typing.Optional[str]):
+    # Service control moved to vyos.utils.serial to unify checks and prompts. 
+    # If users are connected, we want to show an informational message and a prompt
+    # to continue, verifying that the user acknowledges possible interruptions. 
+    if device_name:
+        _restart_login_consoles(prompt_user=True, quiet=False, devices=[device_name])
+    else:
+        _restart_login_consoles(prompt_user=True, quiet=False)
+
+if __name__ == '__main__':
+    try:
+        res = vyos.opmode.run(sys.modules[__name__])
+        if res:
+            print(res)
+    except (ValueError, vyos.opmode.Error) as e:
+        print(e)
+        sys.exit(1)