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fix(mh): give LMAA the code its address family needs (#2280) #2350

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Merged
JarryShaw merged 1 commit into from
Oct 27, 2026
Merged

fix(mh): give LMAA the code its address family needs (#2280) #2350

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32 changes: 27 additions & 5 deletions pcapkit/protocols/internet/mh.py
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Original file line number Diff line number Diff line change
Expand Up @@ -9470,7 +9470,7 @@ def _make_opt_cr(self, type: 'Enum_Option', option: 'Optional[Data_ContextReques
)

def _make_opt_lmaa(self, type: 'Enum_Option', option: 'Optional[Data_LMAAddressOption]' = None, *,
code: 'LMAAddressCode | StdlibEnum | AenumEnum | str | int' = LMAAddressCode.IPv6_LMAA,
code: 'Optional[LMAAddressCode | StdlibEnum | AenumEnum | str | int]' = None,
code_default: 'Optional[int]' = None,
code_namespace: 'Optional[dict[str, int] | dict[int, str] | Type[StdlibEnum] | Type[AenumEnum]]' = None, # pylint: disable=line-too-long
code_reversed: 'bool' = False,
Expand All @@ -9483,7 +9483,8 @@ def _make_opt_lmaa(self, type: 'Enum_Option', option: 'Optional[Data_LMAAddressO
type: Option type.
option: Option data model.
code: Option code, see
:class:`~pcapkit.protocols.internet.mh.LMAAddressCode`.
:class:`~pcapkit.protocols.internet.mh.LMAAddressCode`. If not
given, the code of the address family of ``address``.
code_default: Default option code.
code_namespace: Option code namespace.
code_reversed: Reverse option code namespace.
Expand All @@ -9495,17 +9496,27 @@ def _make_opt_lmaa(self, type: 'Enum_Option', option: 'Optional[Data_LMAAddressO
Returns:
Constructed option schema.

Raises:
ProtocolError: If an explicit ``code`` is not the code
:rfc:`5949#section-6.2.2` gives the address family of
``address`` (:issue:`2280`).

Note:
The option length is derived from the address family rather than from
``code``, so that the two cannot be emitted disagreeing.
``code``, so that the two cannot be emitted disagreeing. A data model
passed as ``option`` keeps its code as captured, even where it
disagrees with the family, so that the capture rebuilds byte for byte.

"""
if option is not None:
reserved = getattr(option, 'reserved', b'\x00')
code_val = int(option.code)
code_val = int(option.code) # type: Optional[int]
address = option.address
elif code is None:
code_val = None
else:
code_val = self._make_index(code, code_default, namespace=code_namespace,
code_val = self._make_index(code, code_default,
namespace=code_namespace if code_namespace is not None else LMAAddressCode,
reversed=code_reversed, pack=False)

if isinstance(address, bytes) and len(address) not in (4, 16):
Expand All @@ -9522,6 +9533,17 @@ def _make_opt_lmaa(self, type: 'Enum_Option', option: 'Optional[Data_LMAAddressO
addr = parse_ip_address(
address, f'{self.alias}: [OptNo {type}] invalid address')

# NOTE: RFC 5949 ties each code to one address family, so a code the
# caller did not choose is the family's own, and one they did choose has
# to agree with it (#2280). A data model passed as ``option`` skips the
# check, so that a captured mismatch still rebuilds byte for byte.
family_code = LMAAddressCode.IPv4_LMAA if addr.version == 4 else LMAAddressCode.IPv6_LMAA
if code_val is None:
code_val = int(family_code)
elif option is None and code_val != family_code:
raise ProtocolError(f'{self.alias}: [OptNo {type}] invalid code: '
f'code does not match address family: {code_val}')

return Schema_LMAAddressOption(
type=type,
length=6 if addr.version == 4 else 18,
Expand Down
60 changes: 60 additions & 0 deletions tests/protocols/internet/test_mh_unit.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3067,6 +3067,66 @@ def test_mh_lmaa_rejects_a_bytes_address_of_the_wrong_width(self) -> None:
self.assertEqual(schema.length, length)
self.assertEqual(schema.address, expected)

def test_mh_lmaa_code_follows_the_address_family(self) -> None:
"""The LMAA code is the one :rfc:`5949#section-6.2.2` gives the family. See #2280.

The maker derives the length from the address, but the code defaulted
to ``IPv6_LMAA`` regardless, so ``address='10.0.0.1'`` packed
``290601000a000001``: an IPv4 length with the IPv6 code.
"""
from pcapkit.const.mh.option import Option
from pcapkit.protocols.internet.mh import MH, LMAAddressCode
from pcapkit.protocols.schema.internet.mh import LMAAddressOption
from pcapkit.utilities.exceptions import BaseError, ProtocolError

proto = object.__new__(MH)
lmaa = Option.Local_Mobility_Anchor_Address_Option

for address, octets in (
('10.0.0.1', '290602000a000001'),
('2001:db8::1', '291201' '00' '20010db8' + '00' * 10 + '0001'),
):
with self.subTest(address=address, code='derived'):
schema = proto._make_opt_lmaa(lmaa, address=address) # type: ignore[arg-type]
self.assertEqual(schema.pack().hex(), octets)
with self.subTest(address=address, code='explicit, matching'):
code = LMAAddressCode.IPv4_LMAA if '.' in address else LMAAddressCode.IPv6_LMAA
schema = proto._make_opt_lmaa(lmaa, address=address, code=code) # type: ignore[arg-type]
self.assertEqual(schema.pack().hex(), octets)
with self.subTest(address=address, code='explicit, matching, by name'):
# #2280: a str code name has to resolve against LMAAddressCode even
# when code_namespace is not given, as every sibling _make_opt_*
# does -- _make_index's str resolution needs an enum default.
name = 'IPv4_LMAA' if '.' in address else 'IPv6_LMAA'
schema = proto._make_opt_lmaa(lmaa, address=address, code=name) # type: ignore[arg-type]
self.assertEqual(schema.pack().hex(), octets)

for address, code in (('10.0.0.1', LMAAddressCode.IPv6_LMAA),
('2001:db8::1', LMAAddressCode.IPv4_LMAA),
('10.0.0.1', LMAAddressCode.Reserved)):
with self.subTest(address=address, code=code):
with self.assertRaises(ProtocolError) as context:
proto._make_opt_lmaa(lmaa, address=address, code=code) # type: ignore[arg-type]
self.assertIsInstance(context.exception, BaseError)
self.assertIn(f'invalid code: code does not match address family: {int(code)}',
str(context.exception))

for address, name in (('10.0.0.1', 'IPv6_LMAA'), ('2001:db8::1', 'IPv4_LMAA')):
with self.subTest(address=address, code=name):
with self.assertRaises(ProtocolError) as context:
proto._make_opt_lmaa(lmaa, address=address, code=name) # type: ignore[arg-type]
self.assertIsInstance(context.exception, BaseError)
self.assertIn('invalid code: code does not match address family:',
str(context.exception))

# a captured mismatch is data, not a request, so it still rebuilds as read
captured = bytes.fromhex('290601000a000001')
data = proto._read_opt_lmaa( # type: ignore[arg-type]
LMAAddressOption.unpack(captured), options=None)
self.assertEqual(data.code, LMAAddressCode.IPv6_LMAA)
rebuilt = proto._make_opt_lmaa(lmaa, data) # type: ignore[arg-type]
self.assertEqual(rebuilt.pack(), captured)

def test_mh_target_careof_address_suboption_round_trips_both_families(self) -> None:
"""The sub-option length is derived from the family, so both widths need pinning.

Expand Down
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