ifupdown/policymanager.py

   1 #!/usr/bin/python
   2 #
   3 # Copyright 2015 Cumulus Networks, Inc. All rights reserved.
   4 #
   5 #
   6 '''
   7 The PolicyManager should be subclassed by addon modules
   8 to read a JSON policy config file that is later used to
   9 set defaults:
  10
  11 Initialize: This module defines a list of config file location based
  12           on module.  There are defined in the __init__():  All the
  13           addon modules need to do is import the policymanager module.
  14
  15           import ifupdown.policymanager as policymanager
  16
  17
  18 Provides: an API to retrieve link attributes based on addon module name,
  19           interface name, and attribute.
  20
  21         The ifupdown.policymanager module provides a global object policymanager_api
  22         that can be called like so:
  23
  24         speed_default = policymanager.policymanager_api.get_default(
  25             module_name='ethtool',
  26             ifname=ifaceobj.name,
  27             attr='link-speed'
  28             )
  29 '''
  30
  31 import json
  32 import logging
  33 import glob
  34
  35 class policymanager():
  36     def __init__(self):
  37         # we should check for these files in order
  38         # so that customers can override the /var/lib file settings
  39         self.logger = logging.getLogger('ifupdown.' +
  40                             self.__class__.__name__)
  41
  42         # we grab the json files from a known location and make sure that
  43         # the defaults_policy is checked first
  44         user_files = glob.glob('/etc/network/ifupdown2/policy.d/*.json')
  45         # grab the default module files
  46         default_files = glob.glob('/var/lib/ifupdown2/policy.d/*.json')
  47         # keep an array of defaults indexed by module name
  48         self.system_policy_array = {}
  49         for filename in default_files:
  50             system_array  = {}
  51             try:
  52                 fd = open(filename,'r')
  53                 system_array = json.load(fd)
  54                 self.logger.debug('reading %s system policy defaults config' \
  55                                   % filename)
  56             except Exception, e:
  57                 self.logger.debug('could not read %s system policy defaults config' \
  58                                   % filename)
  59                 self.logger.debug('    exception is %s' % str(e))
  60             for module in system_array.keys():
  61                 if self.system_policy_array.has_key(module):
  62                     self.logger.debug('warning: overwriting system module %s from file %s' \
  63                                       % (module,filename))
  64                 self.system_policy_array[module] = system_array[module]
  65
  66         # take care of user defined policy defaults
  67         self.user_policy_array = {}
  68         for filename in user_files:
  69             user_array  = {}
  70             try:
  71                 fd = open(filename,'r')
  72                 user_array = json.load(fd)
  73                 self.logger.debug('reading %s policy user defaults config' \
  74                                   % filename)
  75             except Exception, e:
  76                 self.logger.debug('could not read %s user policy defaults config' \
  77                                   % filename)
  78                 self.logger.debug('    exception is %s' % str(e))
  79             # customer added module attributes
  80             for module in user_array.keys():
  81                 if self.system_policy_array.has_key(module):
  82                     # warn user that we are overriding the system module setting
  83                     self.logger.debug('warning: overwriting system with user module %s from file %s' \
  84                                       % (module,filename))
  85                 self.user_policy_array[module] = user_array[module]
  86         return
  87
  88     def get_iface_default(self,module_name=None,ifname=None,attr=None):
  89         '''
  90         get_iface_default: Addon modules must use one of two types of access methods to
  91         the default configs.   In this method, we expect the default to be
  92         either in
  93             [module]['iface_defaults'][ifname][attr] or
  94             [module]['defaults'][attr]
  95         We first check the user_policy_array and return that value. But if
  96         the user did not specify an override, we use the system_policy_array.
  97         '''
  98         # make sure we have an index
  99         if (not ifname or not attr or not module_name):
 100             return None
 101
 102         val = None
 103         # users can specify defaults to override the systemwide settings
 104         # look for user specific interface attribute iface_defaults first
 105         try:
 106             # looks for user specified value
 107             val = self.user_policy_array[module_name]['iface_defaults'][ifname][attr]
 108             return val
 109         except:
 110             pass
 111         try:
 112             # failing that, there may be a user default for all intefaces
 113             val = self.user_policy_array[module_name]['defaults'][attr]
 114             return val
 115         except:
 116             pass
 117         try:
 118             # failing that, look for  system setting for the interface
 119             val = self.system_policy_array[module_name]['iface_defaults'][ifname][attr]
 120             return val
 121         except:
 122             pass
 123         try:
 124             # failing that, look for  system setting for all interfaces
 125             val = self.system_policy_array[module_name]['defaults'][attr]
 126             return val
 127         except:
 128             pass
 129
 130         # could not find any system or user default so return Non
 131         return val
 132
 133     def get_attr_default(self,module_name=None,attr=None):
 134         '''
 135         get_attr_default: Addon modules must use one of two types of access methods to
 136         the default configs.   In this method, we expect the default to be in
 137
 138         [module][attr]
 139
 140         We first check the user_policy_array and return that value. But if
 141         the user did not specify an override, we use the system_policy_array.
 142         '''
 143         if (not attr or not module_name):
 144             return None
 145         # users can specify defaults to override the systemwide settings
 146         # look for user specific interface attribute iface_defaults first
 147         val = None
 148         if self.user_policy_array.get(module_name):
 149             val = self.user_policy_array[module_name].get(attr)
 150
 151         if not val:
 152             if self.system_policy_array.get(module_name):
 153                 val = self.system_policy_array[module_name].get(attr)
 154
 155         return val
 156
 157     def get_module_default(self,module_name=None):
 158         '''
 159         get_module_default: Addon modules can also access the entire config
 160         This method returns indexed by "system" and "user": these are the
 161         system-wide and user-defined policy arrays for a specific module.
 162         '''
 163         if not module_name:
 164             return None
 165         if self.system_policy_array.get(module_name) and \
 166            self.user_policy_array.get(module_name):
 167             mod_array = {"system":self.system_policy_array[module_name],
 168                          "user":self.user_policy_array[module_name]}
 169         else:
 170             # the module must not have these defined, return None
 171             mod_array = None
 172
 173         return mod_array
 174
 175 policymanager_api = policymanager()