T8910: ipoe-server: expose accel-ppp idle-timeout option

Add a CLI knob to terminate idle IPoE sessions after a configurable
timeout:

  set service ipoe-server idle-timeout <0-86400>

Today there is no way to age out stale IPoE sessions: clients that go
silent (powered off, link down) leave a session record on the router
indefinitely. accel-ppp natively supports idle-timeout in its [ipoe]
section but VyOS did not expose it.

The option is added as a shared accel-ppp include so it can be reused
by other accel-ppp services in follow-up PRs.

1 files changed, 19 insertions, 0 deletions

diff --git a/smoketest/scripts/cli/test_service_ipoe-server.py b/smoketest/scripts/cli/test_service_ipoe-server.py
index 47d6cce4b..614295fd8 100755
--- a/smoketest/scripts/cli/test_service_ipoe-server.py
+++ b/smoketest/scripts/cli/test_service_ipoe-server.py
@@ -319,6 +319,25 @@ delegate={delegate_2_prefix},{delegate_mask},name={pool_name}"""
         conf.read(self._config_file)
         self.assertIn(f'start={start_session}', conf['ipoe']['interface'])
 
+    def test_ipoe_server_idle_timeout(self):
+        idle_timeout = '300'
+
+        self.basic_config()
+        self.cli_commit()
+
+        # Default: no idle-timeout emitted
+        conf = ConfigParser(allow_no_value=True, delimiters='=', strict=False)
+        conf.read(self._config_file)
+        self.assertNotIn('idle-timeout', conf['ipoe'])
+
+        # Configure idle-timeout
+        self.set(['idle-timeout', idle_timeout])
+        self.cli_commit()
+
+        conf = ConfigParser(allow_no_value=True, delimiters='=', strict=False)
+        conf.read(self._config_file)
+        self.assertEqual(conf['ipoe']['idle-timeout'], idle_timeout)
+
     @unittest.skip("PPP is not a part of IPoE")
     def test_accel_ppp_options(self):
         pass