def check_blackholes(simulation):
'''Do any switches:
- send packets into a down link?
- drop packets that are supposed to go out their in_port?
This method double checks whether it's possible for any
packets to fall into the blackhole in the first place.
Slightly different than check_connectivity. blackholes imply no
connectivity, but not vice versa. No connectivity could also be due to:
- a loop
- PacketIn-based reactive routing
'''
# TODO(cs): just realized -- the C-version of Hassell might be configured to
# *stop* as soon as it gets to an edge port. At least, this is the
# behavior of the find_reachability function in python Hassell. So we'd
# have to do an iterative computation: all switches that are one
# hop away, then two hops, etc. Otherwise we wouldn't find blackholes in
# the middle of the network.
# For now, use a python method that explicitly
# finds blackholes rather than inferring them from check_reachability
# Warning! depends on python Hassell -- may be really slow!
NTF = hsa_topo.generate_NTF(simulation.topology.live_switches)
TTF = hsa_topo.generate_TTF(simulation.topology.live_links)
blackholes = hsa.find_blackholes(NTF, TTF, simulation.topology.access_links)
return blackholes
def test_blackhole(self):
switch1 = create_switch(1, 2)
flow_mod = ofp_flow_mod(xid=124, priority=1, match=ofp_match(in_port=1, nw_src="1.2.3.4"), action=ofp_action_output(port=2))
switch1.table.process_flow_mod(flow_mod)
switch2 = create_switch(2, 2)
network_links = [Link(switch1, switch1.ports[2], switch2, switch2.ports[2]),
Link(switch2, switch2.ports[2], switch1, switch1.ports[2])]
NTF = hsa_topo.generate_NTF([switch1, switch2])
TTF = hsa_topo.generate_TTF(network_links)
access_links = [MockAccessLink(switch1, switch1.ports[1]),
MockAccessLink(switch2, switch2.ports[1])]
blackholes = hsa.find_blackholes(NTF, TTF, access_links)
self.assertEqual([(100002, [100001, 100002])], blackholes)
