Block port update from unbound DHCP agent
Current DHCP port management in Neutron makes the server to clear the device_id while the agent is responsible for setting it. This may cause a potential race condition, for example during network rescheduling. The server aims to clear the device_id on a DHCP port and assign the network to another agent while the old agent might just be taking possession of the port. If the DHCP agent takes possession of the port (i.e., update port...set the device_id) before the server clears it, then there is no issue. However, if this happens after the clear operation by server then the DHCP port would be updated/marked to be owned by the old agent. When the new agent takes over the network scheduled to it, it won't be able to find a port to reuse so that an extra port might need to be created. This leads to two issues: 1) an extra port is created and never deleted; 2) the extra port creation may fail if there are no available IP addresses. This patch proposes a validation check to prevent an agent from updating a DHCP port unless the network is bound to that agent. Co-authored-by: Allain Legacy <Allain.legacy@windriver.com> Closes-Bug: #1795126 Story: 2003919 Change-Id: Ie619516c07fb3dc9d025f64c0e1e59d5d808cb6f (cherry picked from commitb70ee4df88
) (cherry picked from commitb9f9c021c9
)
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@ -260,6 +260,13 @@ class DhcpRpcCallback(object):
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plugin = directory.get_plugin()
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return self._port_action(plugin, context, port, 'create_port')
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def _is_dhcp_agent_hosting_network(self, plugin, context, host,
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network_id):
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"""Check whether a DHCP agent (host) is hosting a network."""
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agents = plugin.get_dhcp_agents_hosting_networks(context, [network_id],
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hosts=[host])
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return len(agents) != 0
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@db_api.retry_db_errors
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def update_dhcp_port(self, context, **kwargs):
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"""Update the dhcp port."""
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@ -269,11 +276,14 @@ class DhcpRpcCallback(object):
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port['port'][portbindings.HOST_ID] = host
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plugin = directory.get_plugin()
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try:
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network_id = port['port']['network_id']
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old_port = plugin.get_port(context, port['id'])
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if (old_port['device_id'] != n_const.DEVICE_ID_RESERVED_DHCP_PORT
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and old_port['device_id'] !=
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utils.get_dhcp_agent_device_id(port['port']['network_id'],
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host)):
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if (old_port['device_id'] !=
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n_const.DEVICE_ID_RESERVED_DHCP_PORT and
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old_port['device_id'] !=
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utils.get_dhcp_agent_device_id(network_id, host) or
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not self._is_dhcp_agent_hosting_network(plugin, context, host,
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network_id)):
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raise n_exc.DhcpPortInUse(port_id=port['id'])
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LOG.debug('Update dhcp port %(port)s '
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'from %(host)s.',
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@ -43,6 +43,10 @@ class TestDhcpRpcCallback(base.BaseTestCase):
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self.mock_set_dirty = set_dirty_p.start()
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self.utils_p = mock.patch('neutron.plugins.common.utils.create_port')
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self.utils = self.utils_p.start()
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self.agent_hosting_network_p = mock.patch.object(self.callbacks,
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'_is_dhcp_agent_hosting_network')
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self.mock_agent_hosting_network = self.agent_hosting_network_p.start()
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self.mock_agent_hosting_network.return_value = True
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self.segment_plugin = mock.MagicMock()
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directory.add_plugin('segments', self.segment_plugin)
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@ -311,6 +315,38 @@ class TestDhcpRpcCallback(base.BaseTestCase):
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self.plugin.assert_has_calls([
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mock.call.update_port(mock.ANY, 'foo_port_id', expected_port)])
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def test_update_dhcp_port_with_agent_not_hosting_network(self):
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port = {'port': {'network_id': 'foo_network_id',
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'device_owner': constants.DEVICE_OWNER_DHCP,
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'fixed_ips': [{'subnet_id': 'foo_subnet_id'}]}
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}
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self.plugin.get_port.return_value = {
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'device_id': n_const.DEVICE_ID_RESERVED_DHCP_PORT}
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self.mock_agent_hosting_network.return_value = False
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self.assertRaises(exceptions.DhcpPortInUse,
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self.callbacks.update_dhcp_port,
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mock.Mock(),
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host='foo_host',
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port_id='foo_port_id',
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port=port)
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def test__is_dhcp_agent_hosting_network(self):
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self.agent_hosting_network_p.stop()
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agent = mock.Mock()
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with mock.patch.object(self.plugin, 'get_dhcp_agents_hosting_networks',
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return_value=[agent]):
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ret = self.callbacks._is_dhcp_agent_hosting_network(self.plugin,
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mock.Mock(), host='foo_host', network_id='foo_network_id')
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self.assertTrue(ret)
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def test__is_dhcp_agent_hosting_network_false(self):
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self.agent_hosting_network_p.stop()
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with mock.patch.object(self.plugin, 'get_dhcp_agents_hosting_networks',
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return_value=[]):
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ret = self.callbacks._is_dhcp_agent_hosting_network(self.plugin,
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mock.Mock(), host='foo_host', network_id='foo_network_id')
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self.assertFalse(ret)
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def test_release_dhcp_port(self):
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port_retval = dict(id='port_id', fixed_ips=[dict(subnet_id='a')])
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self.plugin.get_ports.return_value = [port_retval]
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