op-mode: T6175: "renew dhcp interface <name>" does not check for DHCP interface

The current op-mode script simply calls sudo systemctl restart "dhclient@$4.service"
with no additional information about a client interface at all.

This results in useless dhclient processes
root  47812  4.7  0.0   5848  3584 ?  Ss 00:30   0:00 /sbin/dhclient -4 -d
root  48121  0.0  0.0   4188  3072 ?  S  00:30   0:00  \_ /bin/sh /sbin/dhclient-script
root  48148 50.0  0.2  18776 11264 ?  R  00:30   0:00      \_ python3 -

Which also assign client leases to all local interfaces, if we receive one
valid DHCPOFFER

vyos@vyos:~$ show interfaces
Codes: S - State, L - Link, u - Up, D - Down, A - Admin Down
Interface    IP Address         MAC                VRF        MTU  S/L    Description
-----------  -----------------  -----------------  -------  -----  -----  -------------
eth0         -                  00:50:56:bf:c5:6d  default   1500  u/u
eth0.10      172.16.33.102/24   00:50:56:bf:c5:6d  default   1500  u/u
eth1         172.16.33.131/24   00:50:56:b3:38:c5  default   1500  u/u

172.16.33.102/24 and 172.16.33.131/24 are stray DHCP addresses.

This commit moved the renew command to the DHCP op-mode script to properly
validate if the interface we request a renew for, has actually a dhcp address
configured. In additional this exposes the renew feature to the API.

2 files changed, 32 insertions, 1 deletions

diff --git a/src/op_mode/dhcp.py b/src/op_mode/dhcp.py
index d27e1baf7..a2f947400 100755
--- a/src/op_mode/dhcp.py
+++ b/src/op_mode/dhcp.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env python3
 #
-# Copyright (C) 2022-2023 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
@@ -33,6 +33,7 @@ from vyos.kea import kea_get_leases
 from vyos.kea import kea_get_pool_from_subnet_id
 from vyos.kea import kea_delete_lease
 from vyos.utils.process import is_systemd_service_running
+from vyos.utils.process import call
 
 time_string = "%a %b %d %H:%M:%S %Z %Y"
 
@@ -309,6 +310,25 @@ def _verify(func):
         return func(*args, **kwargs)
     return _wrapper
 
+def _verify_client(func):
+    """Decorator checks if interface is configured as DHCP client"""
+    from functools import wraps
+    from vyos.ifconfig import Section
+
+    @wraps(func)
+    def _wrapper(*args, **kwargs):
+        config = ConfigTreeQuery()
+        family = kwargs.get('family')
+        v = 'v6' if family == 'inet6' else ''
+        interface = kwargs.get('interface')
+        interface_path = Section.get_config_path(interface)
+        unconf_message = f'DHCP{v} client not configured on interface {interface}!'
+
+        # Check if config does not exist
+        if not config.exists(f'interfaces {interface_path} address dhcp{v}'):
+            raise vyos.opmode.UnconfiguredSubsystem(unconf_message)
+        return func(*args, **kwargs)
+    return _wrapper
 
 @_verify
 def show_pool_statistics(raw: bool, family: ArgFamily, pool: typing.Optional[str]):
@@ -474,6 +494,16 @@ def show_client_leases(raw: bool, family: ArgFamily, interface: typing.Optional[
     else:
         return _get_formatted_client_leases(lease_data, family=family)
 
+@_verify_client
+def renew_client_lease(raw: bool, family: ArgFamily, interface: str):
+    if not raw:
+        v = 'v6' if family == 'inet6' else ''
+        print(f'Restarting DHCP{v} client on interface {interface}...')
+    if family == 'inet6':
+        call(f'systemctl restart dhcp6c@{interface}.service')
+    else:
+        call(f'systemctl restart dhclient@{interface}.service')
+
 if __name__ == '__main__':
     try:
         res = vyos.opmode.run(sys.modules[__name__])
diff --git a/src/systemd/dhclient@.service b/src/systemd/dhclient@.service
index 099f7ed52..d430d8868 100644
--- a/src/systemd/dhclient@.service
+++ b/src/systemd/dhclient@.service
@@ -3,6 +3,7 @@ Description=DHCP client on %i
 Documentation=man:dhclient(8)
 StartLimitIntervalSec=0
 After=vyos-router.service
+ConditionPathExists=/run/dhclient/dhclient_%i.conf
 
 [Service]
 Type=exec