multi_interface_roam: ip_rule.py Source File

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00001 #! /usr/bin/env python
00002 
00003 from twisted.internet.defer import inlineCallbacks, DeferredLock
00004 from twisted.internet import reactor
00005 import state_publisher
00006 import system
00007 
00008 class IpRule:
00009     """Manage the ip rules for a given priority level.
00010     
00011     There are two intended uses:
00012     
00013     1. There is a single dynamic rule at that priority level. Use set to
00014     change it.
00015     
00016     2. There are multiple static rules at that level. Use add to add each
00017     one of them, and flush to remove them all.
00018     """
00019     def __init__(self, priority):
00020         self._lock = DeferredLock()
00021         self.priority = str(priority)
00022         self.is_shutdown = False
00023         self.state_pub = state_publisher.StatePublisher(())
00024         self.flush()
00025         reactor.addSystemEventTrigger('before', 'shutdown', self._shutdown)
00026 
00027     @inlineCallbacks
00028     def flush(self):
00029         self.prev = () # Won't hurt to do it here, just means we might not
00030                        # delete during ongoing set. Ensures it is set at
00031                        # end of construction.
00032         yield self._lock.acquire()
00033         try:
00034             retcode = None
00035             while not retcode:
00036                 retcode = yield system.system(system.Quiet, 'ip', 'rule', 'del', 'priority', self.priority)
00037         finally:
00038             self._lock.release()
00039     
00040     @inlineCallbacks
00041     def _set_or_add(self, remove_old, args):
00042         """Changes/adds the rule. Call with no arguments to clear the rule."""
00043         if self.is_shutdown:
00044             return
00045         yield self._lock.acquire()
00046         try:
00047             # Are we replacing a rule with itself?
00048             if remove_old and self.prev and args == self.prev:
00049                 return
00050             # Add new rule
00051             if args:
00052                 yield system.system('ip', 'rule', 'add', "priority", self.priority, *args)
00053             # Add remove old rule
00054             if self.prev and remove_old:
00055                 yield system.system('ip', 'rule', 'del', "priority", self.priority, *self.prev)
00056             self.prev = args
00057             self.state_pub.set(args)
00058 
00059         finally:
00060             self._lock.release()
00061 
00062     def set(self, *args):
00063         """Changes/adds the rule. Call with no arguments to clear the rule."""
00064         self._set_or_add(True, args)
00065 
00066     def add(self, *args):
00067         """Adds a rule without removing the existing one."""
00068         self._set_or_add(False, args)
00069 
00070     @inlineCallbacks
00071     def _shutdown(self):
00072         yield self.flush()
00073         self.is_shutdown = True