[dhcp_relay] Add dhcp6relay runtime reconfiguration tests

tests/dhcp_relay/test_dhcpv6_relay_runtime_config.py

@@ -0,0 +1,336 @@
+"""
+DHCPv6 relay runtime reconfiguration tests.
+
+These tests validate that the SONiC-native ``dhcp6relay`` applies configuration
+changes at runtime, without restarting the ``dhcp_relay`` container. The
+behaviours under test are:
+
+  * ``dhcp6relay`` is started unconditionally, even when no ``dhcpv6_servers``
+    are configured;
+  * ``dhcpv6_servers`` added or removed through CONFIG_DB are applied without a
+    container restart (the process PID is unchanged and the ``need restart
+    container to take effect`` log is no longer emitted);
+  * a VLAN whose DHCPv6 relay becomes active or inactive at runtime (its IPv6
+    address added or removed) is added to / removed from the running relay
+    without a container restart.
+
+Every configuration change is driven through CONFIG_DB (``sonic-db-cli`` /
+``config`` CLI). The tests never pass arguments to the ``dhcp6relay`` binary
+directly and never drive ``supervisorctl`` to start or stop the agent.
+"""
+import logging
+import time
+
+import pytest
+
+from tests.common.utilities import wait_until
+from tests.common.helpers.assertions import pytest_assert
+
+pytestmark = [
+    pytest.mark.topology('t0', 'm0', 'mx', 't0-2vlans'),
+    pytest.mark.device_type('vs')
+]
+
+logger = logging.getLogger(__name__)
+
+DHCP_RELAY_CONTAINER = "dhcp_relay"
+# CONFIG_DB stores list-typed fields with a trailing '@'; the relay sees the
+# field without the suffix once swss deserialises the list.
+DHCPV6_SERVERS_FIELD = "dhcpv6_servers@"
+NEED_RESTART_LOG = "need restart container to take effect"
+
+
+def _dhcp6relay_pid(duthost):
+    """Return the dhcp6relay PID inside the dhcp_relay container as a string, or
+    an empty string if it is not running."""
+    return duthost.shell(
+        "docker exec {} pidof dhcp6relay".format(DHCP_RELAY_CONTAINER),
+        module_ignore_errors=True
+    )["stdout"].strip()
+
+
+def _dhcp6relay_running(duthost):
+    return _dhcp6relay_pid(duthost) != ""
+
+
+def _supervisor_lists_dhcp6relay(duthost):
+    """True if supervisord knows about the dhcp6relay program (it is listed in
+    the dhcp-relay group), regardless of dhcpv6_servers being configured."""
+    out = duthost.shell(
+        "docker exec {} supervisorctl status dhcp-relay:dhcp6relay".format(DHCP_RELAY_CONTAINER),
+        module_ignore_errors=True
+    )["stdout"]
+    return "dhcp6relay" in out and "no such process" not in out.lower()
+
+
+def _write_syslog_marker(duthost):
+    """Write a unique marker into syslog and return it, so a later read can be
+    scoped to only the lines produced after this point."""
+    marker = "dhcp6relay_rt_test_{}".format(int(time.time() * 1000))
+    duthost.shell("logger {}".format(marker))
+    return marker
+
+
+def _syslog_since(duthost, marker):
+    """Return syslog text from the marker line onward."""
+    return duthost.shell(
+        "sudo sed -n '/{}/,$p' /var/log/syslog".format(marker),
+        module_ignore_errors=True
+    )["stdout"]
+
+
+def _restart_dhcp_relay(duthost):
+    """Restart the dhcp_relay container (re-renders supervisord from CONFIG_DB)
+    and wait for dhcp6relay to come back up."""
+    duthost.shell("sudo systemctl reset-failed {}".format(DHCP_RELAY_CONTAINER))
+    duthost.shell("sudo systemctl restart {}".format(DHCP_RELAY_CONTAINER))
+    pytest_assert(
+        wait_until(90, 3, 5, _dhcp6relay_running, duthost),
+        "dhcp6relay did not come up after dhcp_relay restart"
+    )
+
+
+@pytest.fixture(scope="function")
+def no_dhcpv6_servers(duthost):
+    """Snapshot every DHCP_RELAY row's dhcpv6_servers list, clear them all so the
+    DUT has no DHCPv6 relay server configured, restart the container to re-render
+    supervisord, then restore the original configuration on teardown."""
+    keys = duthost.shell(
+        'sonic-db-cli CONFIG_DB KEYS "DHCP_RELAY|*"'
+    )["stdout"].splitlines()
+    saved = {}
+    for key in keys:
+        servers = duthost.shell(
+            'sonic-db-cli CONFIG_DB HGET "{}" "{}"'.format(key, DHCPV6_SERVERS_FIELD)
+        )["stdout"].strip()
+        if servers:
+            saved[key] = servers
+            duthost.shell(
+                'sonic-db-cli CONFIG_DB HDEL "{}" "{}"'.format(key, DHCPV6_SERVERS_FIELD)
+            )
+    _restart_dhcp_relay(duthost)
+
+    yield
+
+    for key, servers in saved.items():
+        duthost.shell(
+            'sonic-db-cli CONFIG_DB HSET "{}" "{}" "{}"'.format(key, DHCPV6_SERVERS_FIELD, servers)
+        )
+    _restart_dhcp_relay(duthost)
+
+
+@pytest.fixture(scope="function")
+def first_relay_vlan(duthost):
+    """Return the name of the first VLAN that has a DHCPv6 relay configured, or
+    skip the test if none exists."""
+    keys = duthost.shell(
+        'sonic-db-cli CONFIG_DB KEYS "DHCP_RELAY|*"'
+    )["stdout"].splitlines()
+    relay_vlan = None
+    for key in keys:
+        servers = duthost.shell(
+            'sonic-db-cli CONFIG_DB HGET "{}" "{}"'.format(key, DHCPV6_SERVERS_FIELD)
+        )["stdout"].strip()
+        if servers:
+            relay_vlan = key.split("|", 1)[1]
+            break
+    if relay_vlan is None:
+        pytest.skip("No DHCP_RELAY VLAN with dhcpv6_servers configured on the DUT")
+    return relay_vlan
+
+
+@pytest.fixture(scope="function")
+def runtime_added_vlan(duthost):
+    """Create a fresh VLAN that has a DHCPv6 relay configured but NO IPv6 address
+    on its interface yet, while dhcp6relay is already running. Yields the VLAN
+    name and the IPv6 address to add at runtime. Cleans everything up on teardown.
+    All operations go through the config CLI / CONFIG_DB; no container restart."""
+    vlan_id = 4002
+    vlan = "Vlan{}".format(vlan_id)
+    vlan_ipv6 = "fc02:4002::1/64"
+    servers = "2000::100,2000::200"
+
+    # Start clean in case a previous aborted run left this VLAN behind.
+    duthost.shell("sudo config interface ip remove {} {}".format(vlan, vlan_ipv6),
+                  module_ignore_errors=True)
+    duthost.shell('sonic-db-cli CONFIG_DB DEL "DHCP_RELAY|{}"'.format(vlan),
+                  module_ignore_errors=True)
+    duthost.shell("sudo config vlan del {}".format(vlan_id), module_ignore_errors=True)
+
+    # Create the VLAN (no IPv6 address yet) and give it a DHCPv6 relay config.
+    duthost.shell("sudo config vlan add {}".format(vlan_id))
+    duthost.shell('sonic-db-cli CONFIG_DB HSET "DHCP_RELAY|{}" "{}" "{}"'
+                  .format(vlan, DHCPV6_SERVERS_FIELD, servers))
+
+    yield vlan, vlan_ipv6
+
+    duthost.shell("sudo config interface ip remove {} {}".format(vlan, vlan_ipv6),
+                  module_ignore_errors=True)
+    duthost.shell('sonic-db-cli CONFIG_DB DEL "DHCP_RELAY|{}"'.format(vlan),
+                  module_ignore_errors=True)
+    duthost.shell("sudo config vlan del {}".format(vlan_id), module_ignore_errors=True)
+
+
+@pytest.fixture(scope="function")
+def runtime_active_vlan(duthost):
+    """Create a fresh VLAN that has BOTH a DHCPv6 relay AND an IPv6 address on
+    its interface, so the relay adds it at runtime and it is fully active. Yields
+    the VLAN name and the IPv6 address (so a test can remove it again). Cleans
+    everything up on teardown. All operations go through the config CLI /
+    CONFIG_DB; no container restart."""
+    vlan_id = 4003
+    vlan = "Vlan{}".format(vlan_id)
+    vlan_ipv6 = "fc02:4003::1/64"
+    servers = "2000::100,2000::200"
+
+    # Start clean in case a previous aborted run left this VLAN behind.
+    duthost.shell("sudo config interface ip remove {} {}".format(vlan, vlan_ipv6),
+                  module_ignore_errors=True)
+    duthost.shell('sonic-db-cli CONFIG_DB DEL "DHCP_RELAY|{}"'.format(vlan),
+                  module_ignore_errors=True)
+    duthost.shell("sudo config vlan del {}".format(vlan_id), module_ignore_errors=True)
+
+    # Create the VLAN, give it a DHCPv6 relay config and an IPv6 address so the
+    # relay activates it.
+    duthost.shell("sudo config vlan add {}".format(vlan_id))
+    duthost.shell('sonic-db-cli CONFIG_DB HSET "DHCP_RELAY|{}" "{}" "{}"'
+                  .format(vlan, DHCPV6_SERVERS_FIELD, servers))
+    duthost.shell("sudo config interface ip add {} {}".format(vlan, vlan_ipv6))
+
+    yield vlan, vlan_ipv6
+
+    duthost.shell("sudo config interface ip remove {} {}".format(vlan, vlan_ipv6),
+                  module_ignore_errors=True)
+    duthost.shell('sonic-db-cli CONFIG_DB DEL "DHCP_RELAY|{}"'.format(vlan),
+                  module_ignore_errors=True)
+    duthost.shell("sudo config vlan del {}".format(vlan_id), module_ignore_errors=True)
+
+
+def test_dhcp6relay_starts_without_dhcpv6_servers(duthost, no_dhcpv6_servers):
+    """dhcp6relay must start unconditionally, even when no VLAN has any
+    dhcpv6_servers configured. The no_dhcpv6_servers fixture clears all server
+    lists and restarts the container, so supervisord re-renders with no DHCPv6
+    relay servers present; the agent must still be listed and running."""
+    pytest_assert(
+        wait_until(60, 3, 0, _supervisor_lists_dhcp6relay, duthost),
+        "dhcp6relay is not registered in supervisord when no dhcpv6_servers are configured"
+    )
+    pytest_assert(
+        _dhcp6relay_running(duthost),
+        "dhcp6relay is not running when no dhcpv6_servers are configured"
+    )
+
+
+def test_dhcp6relay_runtime_ipv6_added_after_start(duthost, runtime_added_vlan):
+    """A VLAN that has a DHCPv6 relay configured but no IPv6 address on its
+    interface must not be relayed; once an IPv6 address is configured on that
+    VLAN interface at runtime (after the agent is already running), the relay
+    must add the relay instance without a container restart."""
+    vlan, vlan_ipv6 = runtime_added_vlan
+    add_log = "Add relay config for {} at runtime".format(vlan)
+
+    pid_before = _dhcp6relay_pid(duthost)
+    pytest_assert(pid_before != "", "dhcp6relay is not running")
+
+    # With no IPv6 on the VLAN interface, the relay must not add a relay config
+    # for it (build_desired_config skips VLANs without an IPv6 address).
+    marker_noip = _write_syslog_marker(duthost)
+    time.sleep(3)
+    pytest_assert(
+        add_log not in _syslog_since(duthost, marker_noip),
+        "dhcp6relay added a relay config for {} before it had an IPv6 address".format(vlan)
+    )
+
+    # Configure an IPv6 address on the VLAN interface at runtime.
+    marker_add = _write_syslog_marker(duthost)
+    duthost.shell("sudo config interface ip add {} {}".format(vlan, vlan_ipv6))
+
+    # The relay must now add the relay config for this VLAN at runtime, without
+    # restarting the container.
+    pytest_assert(
+        wait_until(30, 2, 0, lambda: add_log in _syslog_since(duthost, marker_add)),
+        "dhcp6relay did not add the relay config for {} after its IPv6 address was configured".format(vlan)
+    )
+    pytest_assert(
+        pid_before == _dhcp6relay_pid(duthost),
+        "dhcp6relay restarted when an IPv6 address was added at runtime"
+    )
+    pytest_assert(
+        NEED_RESTART_LOG not in _syslog_since(duthost, marker_add),
+        "dhcp6relay emitted '{}' when an IPv6 address was added at runtime".format(NEED_RESTART_LOG)
+    )
+
+
+def test_dhcp6relay_runtime_server_change_no_restart(duthost, first_relay_vlan):
+    """Adding and removing a dhcpv6_server through CONFIG_DB must be applied at
+    runtime: the dhcp6relay process PID is unchanged (no container restart) and
+    the legacy 'need restart container to take effect' log is not emitted."""
+    vlan = first_relay_vlan
+    key = "DHCP_RELAY|{}".format(vlan)
+    original = duthost.shell(
+        'sonic-db-cli CONFIG_DB HGET "{}" "{}"'.format(key, DHCPV6_SERVERS_FIELD)
+    )["stdout"].strip()
+
+    pid_before = _dhcp6relay_pid(duthost)
+    pytest_assert(pid_before != "", "dhcp6relay is not running")
+    marker = _write_syslog_marker(duthost)
+
+    updated = original + ",2000::dead:beef"
+    try:
+        duthost.shell(
+            'sonic-db-cli CONFIG_DB HSET "{}" "{}" "{}"'.format(key, DHCPV6_SERVERS_FIELD, updated)
+        )
+        pytest_assert(
+            wait_until(30, 2, 0,
+                       lambda: "Update relay config for {} at runtime".format(vlan)
+                       in _syslog_since(duthost, marker)),
+            "dhcp6relay did not apply the runtime server change for {}".format(vlan)
+        )
+        pid_after = _dhcp6relay_pid(duthost)
+        pytest_assert(
+            pid_before == pid_after,
+            "dhcp6relay restarted on a runtime server change (pid {} -> {})".format(pid_before, pid_after)
+        )
+        pytest_assert(
+            NEED_RESTART_LOG not in _syslog_since(duthost, marker),
+            "dhcp6relay emitted '{}' on a runtime config change".format(NEED_RESTART_LOG)
+        )
+    finally:
+        duthost.shell(
+            'sonic-db-cli CONFIG_DB HSET "{}" "{}" "{}"'.format(key, DHCPV6_SERVERS_FIELD, original)
+        )
+
+
+def test_dhcp6relay_runtime_relay_removed_no_restart(duthost, runtime_active_vlan):
+    """Mirror of the runtime-add test (the removal half of the diff path): once a
+    VLAN's DHCPv6 relay is active, removing its IPv6 address at runtime makes the
+    VLAN drop out of the desired config, so the relay must remove that relay
+    instance (logging 'Remove relay config for <vlan> at runtime') without a
+    container restart and without the legacy 'need restart' log."""
+    vlan, vlan_ipv6 = runtime_active_vlan
+    remove_log = "Remove relay config for {} at runtime".format(vlan)
+
+    pid_before = _dhcp6relay_pid(duthost)
+    pytest_assert(pid_before != "", "dhcp6relay is not running")
+
+    # The fixture configured the VLAN with an IPv6 + relay; give the relay a
+    # moment to have added it before we exercise removal.
+    time.sleep(3)
+
+    # Remove the IPv6 address at runtime -> the VLAN no longer has an address to
+    # bind, so build_desired_config drops it and the relay must remove it.
+    marker = _write_syslog_marker(duthost)
+    duthost.shell("sudo config interface ip remove {} {}".format(vlan, vlan_ipv6))
+
+    pytest_assert(
+        wait_until(30, 2, 0, lambda: remove_log in _syslog_since(duthost, marker)),
+        "dhcp6relay did not remove the relay config for {} after its IPv6 was removed".format(vlan)
+    )
+    pytest_assert(
+        pid_before == _dhcp6relay_pid(duthost),
+        "dhcp6relay restarted when an IPv6 address was removed at runtime"
+    )
+    pytest_assert(
+        NEED_RESTART_LOG not in _syslog_since(duthost, marker),
+        "dhcp6relay emitted '{}' when an IPv6 address was removed at runtime".format(NEED_RESTART_LOG)
+    )