def build_select_cond(p4_state, case_expr, match_list):
select_cond = []
# these casts are kind of silly but simplify the code a lot
if isinstance(case_expr, StructInstance):
case_expr = case_expr.flatten()
elif not isinstance(case_expr, list):
case_expr = [case_expr]
for idx, case_match in enumerate(case_expr):
# default implies don't care, do not add
# TODO: Verify that this assumption is right...
if isinstance(case_match, DefaultExpression):
select_cond.append(z3.BoolVal(True))
elif isinstance(case_match, P4Range):
x = case_match.min
y = case_match.max
match_key = z3.And(z3.ULE(x, match_list[idx]),
z3.UGE(y, match_list[idx]))
select_cond.append(match_key)
elif isinstance(case_match, P4Mask):
val = p4_state.resolve_expr(case_match.value)
mask = case_match.mask
match_key = (val | ~mask) == (match_list[idx] | ~mask)
select_cond.append(match_key)
else:
select_cond.append(case_match == match_list[idx])
if not select_cond:
return z3.BoolVal(False)
return z3.And(*select_cond)
def get_const_matches(self, ctx, c_keys):
matches = []
# match the constant keys with the normal table keys
# this generates the match expression for a specific constant entry
# this is a little inefficient, FIXME.
for index, (key_expr, _) in enumerate(self.keys):
c_key_expr = c_keys[index]
# default implies don't care, do not add
# TODO: Verify that this assumption is right...
if isinstance(c_key_expr, DefaultExpression):
continue
# TODO: Unclear about the role of side-effects here
key_eval = ctx.resolve_expr(key_expr)
if isinstance(c_key_expr, P4Range):
x = ctx.resolve_expr(c_key_expr.min)
y = ctx.resolve_expr(c_key_expr.max)
c_key_eval = z3.And(z3.ULE(x, key_eval), z3.UGE(y, key_eval))
matches.append(c_key_eval)
elif isinstance(c_key_expr, P4Mask):
# TODO: Unclear about the role of side-effects here
val = ctx.resolve_expr(c_key_expr.value)
mask = ctx.resolve_expr(c_key_expr.mask)
c_key_eval = (val & mask) == (key_eval & mask)
matches.append(c_key_eval)
else:
c_key_eval = ctx.resolve_expr(c_key_expr)
matches.append(key_eval == c_key_eval)
return z3.And(*matches)
def eval_keys(self, ctx):
key_pairs = []
if not self.keys:
# there is nothing to match with...
return z3.BoolVal(False)
for index, (key_expr, key_type) in enumerate(self.keys):
key_eval = ctx.resolve_expr(key_expr)
key_sort = key_eval.sort()
key_match = z3.Const(f"{self.name}_table_key_{index}", key_sort)
if key_type == "exact":
# Just a simple comparison, nothing special
key_pairs.append(key_eval == key_match)
elif key_type == "lpm":
# I think this can be arbitrarily large...
# If the shift exceeds the bit width, everything will be zero
# but that does not matter
# TODO: Test this?
mask_var = z3.BitVec(f"{self.name}_table_mask_{index}",
key_sort)
lpm_mask = z3.BitVecVal(2**key_sort.size() - 1,
key_sort) << mask_var
match = (key_eval & lpm_mask) == (key_match & lpm_mask)
key_pairs.append(match)
elif key_type == "ternary":
# Just apply a symbolic mask, any zero bit is a wildcard
# TODO: Test this?
mask = z3.Const(f"{self.name}_table_mask_{index}", key_sort)
# this is dumb...
if isinstance(key_sort, z3.BoolSortRef):
match = z3.And(key_eval, mask) == z3.And(key_match, mask)
else:
match = (key_eval & mask) == (key_match & mask)
key_pairs.append(match)
elif key_type == "range":
# Pick an arbitrary minimum and maximum within the bit range
# the minimum must be strictly lesser than the max
# I do not think a match is needed?
# TODO: Test this?
min_key = z3.Const(f"{self.name}_table_min_{index}", key_sort)
max_key = z3.Const(f"{self.name}_table_max_{index}", key_sort)
match = z3.And(z3.ULE(min_key, key_eval),
z3.UGE(max_key, key_eval))
key_pairs.append(z3.And(match, z3.ULT(min_key, max_key)))
elif key_type == "optional":
# As far as I understand this is just a wildcard for control
# plane purposes. Semantically, there is no point?
# TODO: Test this?
key_pairs.append(z3.BoolVal(True))
elif key_type == "selector":
# Selectors are a deep rabbit hole
# This rabbit hole does not yet make sense to me
# FIXME: Implement
# will intentionally fail if no implementation is present
# impl = self.properties["implementation"]
# impl_extern = self.prog_state.resolve_reference(impl)
key_pairs.append(z3.BoolVal(True))
else:
# weird key, might be some specific specification
raise RuntimeError(f"Key type {key_type} not supported!")
return z3.And(key_pairs)
def eval_const_entries(self, p4_state, action_exprs, action_matches):
context = p4_state.current_context()
forward_cond_copy = context.tmp_forward_cond
for c_keys, (action_name, action_args) in reversed(self.const_entries):
matches = []
# match the constant keys with the normal table keys
# this generates the match expression for a specific constant entry
# this is a little inefficient, fix.
# TODO: Figure out if key type matters here?
for index, (key_expr, key_type) in enumerate(self.keys):
c_key_expr = c_keys[index]
# default implies don't care, do not add
# TODO: Verify that this assumption is right...
if isinstance(c_key_expr, DefaultExpression):
continue
key_eval = p4_state.resolve_expr(key_expr)
if isinstance(c_key_expr, P4Range):
x = c_key_expr.min
y = c_key_expr.max
c_key_eval = z3.And(z3.ULE(x, key_eval),
z3.UGE(y, key_eval))
matches.append(c_key_eval)
elif isinstance(c_key_expr, P4Mask):
val = p4_state.resolve_expr(c_key_expr.mask)
mask = c_key_expr.mask
c_key_eval = (val & mask) == (key_eval & mask)
matches.append(c_key_eval)
else:
c_key_eval = p4_state.resolve_expr(c_key_expr)
matches.append(key_eval == c_key_eval)
action_match = z3.And(*matches)
log.debug("Evaluating constant action %s...", action_name)
# state forks here
var_store, contexts = p4_state.checkpoint()
cond = z3.And(self.locals["hit"], action_match)
context.tmp_forward_cond = z3.And(forward_cond_copy, cond)
self.eval_action(p4_state, action_name, action_args)
if not p4_state.has_exited:
action_exprs.append((cond, p4_state.get_attrs()))
p4_state.has_exited = False
action_matches.append(action_match)
p4_state.restore(var_store, contexts)
def operator(x, y):
# if x and y are ints we might deal with a signed value
# we need to use the normal operator in this case
if isinstance(x, int) and isinstance(y, int):
return op.ge(x, y)
return z3.UGE(x, y)