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.

4 files changed, 38 insertions, 0 deletions

diff --git a/data/templates/accel-ppp/ipoe.config.j2 b/data/templates/accel-ppp/ipoe.config.j2
index 34dfa529a..b0f83a0d6 100644
--- a/data/templates/accel-ppp/ipoe.config.j2
+++ b/data/templates/accel-ppp/ipoe.config.j2
@@ -38,6 +38,9 @@ level={{ log.level }}
 
 [ipoe]
 verbose=1
+{% if idle_timeout is vyos_defined %}
+idle-timeout={{ idle_timeout }}
+{% endif %}
 {% if lua_file is vyos_defined %}
 lua-file={{ lua_file }}
 {% endif %}
diff --git a/interface-definitions/include/accel-ppp/idle-timeout.xml.i b/interface-definitions/include/accel-ppp/idle-timeout.xml.i
new file mode 100644
index 000000000..98af5aa85
--- /dev/null
+++ b/interface-definitions/include/accel-ppp/idle-timeout.xml.i
@@ -0,0 +1,15 @@
+<!-- include start from accel-ppp/idle-timeout.xml.i -->
+<leafNode name="idle-timeout">
+  <properties>
+    <help>Disconnect idle sessions after the specified time (in seconds)</help>
+    <valueHelp>
+      <format>u32:0-86400</format>
+      <description>Idle timeout in seconds</description>
+    </valueHelp>
+    <constraint>
+      <validator name="numeric" argument="--range 0-86400"/>
+    </constraint>
+    <constraintErrorMessage>Idle timeout must be in range 0 to 86400</constraintErrorMessage>
+  </properties>
+</leafNode>
+<!-- include end -->
diff --git a/interface-definitions/service_ipoe-server.xml.in b/interface-definitions/service_ipoe-server.xml.in
index 3093151ea..27b163001 100644
--- a/interface-definitions/service_ipoe-server.xml.in
+++ b/interface-definitions/service_ipoe-server.xml.in
@@ -233,6 +233,7 @@
           #include <include/accel-ppp/default-ipv6-pool.xml.i>
           #include <include/accel-ppp/extended-scripts.xml.i>
           #include <include/accel-ppp/gateway-address-multi.xml.i>
+          #include <include/accel-ppp/idle-timeout.xml.i>
           #include <include/accel-ppp/limits.xml.i>
           #include <include/accel-ppp/max-concurrent-sessions.xml.i>
           #include <include/accel-ppp/shaper.xml.i>
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