def shared_transit(topo, policy1, policy2):
"""Try to find packet in the border of policy1 and the border of policy2.
Note that this is symmetric.
"""
p, pp, ppp, qq, qqq = Consts("p pp ppp qq qqq", Packet)
o, n = Ints("o n")
solv = Solver()
# Predicates are focused on a packet p, all other packets are fodder for
# that one. We want an input packet p or an output packet after a hop p in
# each case.
solv.add(Or(ingress(policy1, p, pp, o), And(egress(policy1, pp, ppp), transfer(topo, ppp, p))))
solv.add(Or(ingress(policy2, p, qq, n), And(egress(policy2, qq, qqq), transfer(topo, qqq, p))))
if solv.check() == unsat:
return None
else:
return solv.model(), (p,), HEADER_INDEX
def shared_inputs(policy1, policy2):
"""Try to find packet in input of policy1 and ingress of policy2."""
p, pp, qq = Consts("p pp qq", Packet)
o, n = Ints("o n")
solv = Solver()
solv.add(input(policy1, p, pp, o))
solv.add(ingress(policy2, p, qq, n))
if solv.check() == unsat:
return None
else:
return solv.model(), (p, pp, qq), HEADER_INDEX
