def solve(self, topo, requirement_dags):
# a list of tuples with info on the node to be attracted,
# the forwarding address, the cost to be set in the fake LSA,
# and the respective destinations
self.fake_ospf_lsas = []
self.reqs = requirement_dags
self.igp_graph = topo
self.igp_paths = ssu.all_shortest_paths(self.igp_graph)
# process input forwarding DAGs, one at the time
for dest, dag in requirement_dags.iteritems():
logger.debug('Solving DAG for dest %s', dest)
self.dest, self.dag = dest, dag
self.add_dest_to_graphs(dest, dag)
if dest not in topo:
sinks = dag.predecessors(dest)
for s in sinks:
logger.info('Adding edge (%s, %s) in the graph',
s, self.dest)
topo.add_edge(s, dest, weight=self.new_edge_weight)
for n in topo.nodes_iter():
if n == dest: # dest is a path in itself
self.igp_paths[n] = ([[n]], 0)
continue
paths = []
cost = sys.maxint
for s in sinks:
if s not in self.igp_paths[n][0]: # no path to sink
continue
c = self.igp_paths[n][1][s]
p = self.igp_paths[n][0][s]
if c < cost: # new spt
paths = list(ssu.extend_paths_list(p, dest))
cost = c
if c == cost: # ecmp
paths.extend(ssu.extend_paths_list(p, dest))
if paths:
_t = self.igp_paths[n]
_t[0][dest] = paths
_t[1][dest] = cost
self.complete_dag()
# Add temporarily the destination to the igp graph and/or req dags
if not self.solvable(dest, dag):
continue
for node in nx.topological_sort(dag, reverse=True)[1:]:
nhs, original_nhs = self.nhs_for(node, dag, dest)
if not self.require_fake_node(nhs, original_nhs):
logger.debug('%s does not require a fake node (%s - %s)',
node, nhs, original_nhs)
continue
for req_nh in nhs:
logger.debug('Placing a fake node for nh %s', req_nh)
self.fake_ospf_lsas.append(ssu.LSA(node=node,
nh=req_nh,
cost=-1,
dest=dest))
return self.fake_ospf_lsas
def check_dest(self):
"""Check that the destination is present in the DAG and the graph"""
dest_in_graph = self.dest in self.g
log.debug('Checking for %s in the graph: %s', self.dest, dest_in_graph)
if not dest_in_graph:
log.info('Adding %s in the graph', self.dest)
self.g.add_node(self.dest, data=Node())
new_paths = {}
new_paths_cost = {n: sys.maxint for n in self.g.nodes_iter()}
dest_in_dag = self.dest in self.dag
log.debug('Checking for the presence of %s the the DAG: %s',
self.dest, dest_in_dag)
if not dest_in_dag or not dest_in_graph:
if not dest_in_dag:
sinks = ssu.find_sink(self.dag)
else:
sinks = self.dag.predecessors(self.dest)
for s in sinks:
if not dest_in_dag:
log.info('Adding %s to %s in the dag', self.dest, s)
self.dag.add_edge(s, self.dest)
if not dest_in_graph:
log.info('Adding edge (%s, %s) in the graph',
s, self.dest)
self.g.add_edge(s, self.dest, weight=self.new_edge_weight)
log.debug('Updating spt/cost accordingly')
for n in self.g.nodes_iter():
if n == self.dest:
new_paths[n] = [[n]]
new_paths_cost[n] = 0
continue
if not self.has_path(n, s):
continue
ns_cost = self.cost(n, s) + self.new_edge_weight
if ns_cost < new_paths_cost[n]: # Created a new SP
ns_path = self.path(n, s)
new_paths_cost[n] = ns_cost
new_paths[n] = list(ssu.extend_paths_list(ns_path,
self.dest
))
elif ns_cost == new_paths_cost: # Created ECMP
ns_path = self.path(n, s)
new_paths[n].extend(ssu.extend_paths_list(ns_path,
self.dest
))
for n, p in new_paths.iteritems(): # Incrementally update the SPT
self.register_path(n, self.dest, p, new_paths_cost[n])
