Move MAX_CHAIN_LEN constants to constants file

Two constants: MAX_CHAIN_LEN_{WRAP,NOWRAP} are now moved
to common.constants file and renamed to
MAX_IPTABLES_CHAIN_LEN_{WRAP,NOWRAP}.

It is done because at least one of them might be now used
outside iptables_manager module (in port_forwarding
extensions)

Change-Id: I9b7a24b0264631e74b3c05b73a22a6a9c2752e82

neutron/agent/l3/extensions/port_forwarding.py

@@ -24,6 +24,7 @@ from neutron.api.rpc.callbacks.consumer import registry
 from neutron.api.rpc.callbacks import events
 from neutron.api.rpc.callbacks import resources
 from neutron.api.rpc.handlers import resources_rpc
+from neutron.common import constants
 from neutron.common import rpc as n_rpc
 from neutron_lib.agent import l3_extension
 from neutron_lib import constants as lib_consts
@@ -32,10 +33,6 @@ LOG = logging.getLogger(__name__)
 DEFAULT_PORT_FORWARDING_CHAIN = 'fip-pf'
 PORT_FORWARDING_PREFIX = 'fip_portforwarding-'
 PORT_FORWARDING_CHAIN_PREFIX = 'pf-'
-# TODO(bzhao) If there are other files use this constant, and move it into
-# constants file. This line will be removed and get the value from constants
-# file.
-MAX_CHAIN_LEN_WRAP = 11
 
 
 class RouterFipPortForwardingMapping(object):
@@ -379,7 +376,7 @@ class PortForwardingAgentExtension(l3_extension.L3AgentExtension):
 
     def _get_port_forwarding_chain_name(self, pf_id):
         chain_name = PORT_FORWARDING_CHAIN_PREFIX + pf_id
-        return chain_name[:MAX_CHAIN_LEN_WRAP]
+        return chain_name[:constants.MAX_IPTABLES_CHAIN_LEN_WRAP]
 
     def _install_default_rules(self, iptables_manager):
         default_rule = '-j %s-%s' % (iptables_manager.wrap_name,

neutron/agent/linux/iptables_manager.py

@@ -35,6 +35,7 @@ from neutron._i18n import _
 from neutron.agent.linux import ip_lib
 from neutron.agent.linux import iptables_comments as ic
 from neutron.agent.linux import utils as linux_utils
+from neutron.common import constants
 from neutron.common import exceptions as n_exc
 from neutron.conf.agent import common as config
 
@@ -54,11 +55,6 @@ def get_binary_name():
 
 binary_name = get_binary_name()
 
-# A length of a chain name must be less than or equal to 11 characters.
-# <max length of iptables chain name> - (<binary_name> + '-') = 28-(16+1) = 11
-MAX_CHAIN_LEN_WRAP = 11
-MAX_CHAIN_LEN_NOWRAP = 28
-
 # Number of iptables rules to print before and after a rule that causes a
 # a failure during iptables-restore
 IPTABLES_ERROR_LINES_OF_CONTEXT = 5
@@ -88,9 +84,9 @@ def comment_rule(rule, comment):
 
 def get_chain_name(chain_name, wrap=True):
     if wrap:
-        return chain_name[:MAX_CHAIN_LEN_WRAP]
+        return chain_name[:constants.MAX_IPTABLES_CHAIN_LEN_WRAP]
     else:
-        return chain_name[:MAX_CHAIN_LEN_NOWRAP]
+        return chain_name[:constants.MAX_IPTABLES_CHAIN_LEN_NOWRAP]
 
 
 class IptablesRule(object):

neutron/common/constants.py

@@ -134,6 +134,12 @@ IPTABLES_PROTOCOL_NAME_MAP = {lib_constants.PROTO_NAME_IPV6_ENCAP: 'ipv6',
                               '141': 'wesp',
                               '142': 'rohc'}
 
+# A length of a iptables chain name must be less than or equal to 11
+# characters.
+# <max length of iptables chain name> - (<binary_name> + '-') = 28-(16+1) = 11
+MAX_IPTABLES_CHAIN_LEN_WRAP = 11
+MAX_IPTABLES_CHAIN_LEN_NOWRAP = 28
+
 # Timeout in seconds for getting an IPv6 LLA
 LLA_TASK_TIMEOUT = 40
 

neutron/tests/unit/agent/l3/extensions/test_port_forwarding.py

@@ -26,6 +26,7 @@ from neutron.agent.linux import iptables_manager
 from neutron.api.rpc.callbacks.consumer import registry
 from neutron.api.rpc.callbacks import resources
 from neutron.api.rpc.handlers import resources_rpc
+from neutron.common import constants
 from neutron.objects import port_forwarding as pf_obj
 from neutron.objects import router
 from neutron.tests import base
@@ -144,7 +145,8 @@ class FipPortForwardingExtensionTestCase(PortForwardingExtensionBaseTestCase):
 
     def _get_chainrule_tag_from_pf_obj(self, target_obj):
         rule_tag = 'fip_portforwarding-' + target_obj.id
-        chain_name = ('pf-' + target_obj.id)[:pf.MAX_CHAIN_LEN_WRAP]
+        chain_name = (
+            'pf-' + target_obj.id)[:constants.MAX_IPTABLES_CHAIN_LEN_WRAP]
         chain_rule = (chain_name,
                       '-d %s/32 -p %s -m %s --dport %s '
                       '-j DNAT --to-destination %s:%s' % (
@@ -235,7 +237,7 @@ class FipPortForwardingExtensionTestCase(PortForwardingExtensionBaseTestCase):
         mock_ip_device.return_value = mock_delete
         self.fip_pf_ext.update_router(self.context, self.router)
         current_chain = ('pf-' + self.portforwarding1.id)[
-                        :pf.MAX_CHAIN_LEN_WRAP]
+                        :constants.MAX_IPTABLES_CHAIN_LEN_WRAP]
         mock_remove_chain.assert_called_once_with(current_chain)
         mock_delete.delete_socket_conntrack_state.assert_called_once_with(
             str(self.portforwarding1.floating_ip_address),
@@ -266,7 +268,7 @@ class FipPortForwardingExtensionTestCase(PortForwardingExtensionBaseTestCase):
         mock_ip_device.return_value = mock_device
         self.fip_pf_ext.update_router(self.context, self.router)
         current_chain = ('pf-' + self.portforwarding1.id)[
-                        :pf.MAX_CHAIN_LEN_WRAP]
+                        :constants.MAX_IPTABLES_CHAIN_LEN_WRAP]
         mock_remove_chain.assert_called_once_with(current_chain)
         mock_device.delete_socket_conntrack_state.assert_called_once_with(
             str(self.portforwarding1.floating_ip_address),