fix(hip): from_data no longer reads alias before _info is set (#1184)

pcapkit/protocols/internet/hip.py

@@ -592,6 +592,11 @@ def read(self, length: 'Optional[int]' = None, *, extension: bool = False, **kwa
 
         if extension:
             return hip
+
+        # NOTE: ``_decode_next_layer`` builds the protocol chain from
+        # :attr:`self.alias <HIP.alias>`, which reads ``self._info``, and
+        # ``__post_init__`` assigns that only once this method returns.
+        self._info = hip
         return self._decode_next_layer(hip, schema.next, length - hip.length)
 
     def make(self,

tests/protocols/internet/test_hip_from_data_alias_unit.py

@@ -0,0 +1,87 @@
+# -*- coding: utf-8 -*-
+"""HIP's ``alias`` is readable while the header is still being decoded.
+
+GitHub issue #1184: :attr:`HIP.alias <pcapkit.protocols.internet.hip.HIP.alias>`
+read ``self._info.version``. Outside an IPv6 extension chain,
+:meth:`HIP.read <pcapkit.protocols.internet.hip.HIP.read>` ends in
+``_decode_next_layer``, which reads ``alias`` for the protocol chain, but
+``_info`` is assigned only once ``read`` has returned. So parsing or
+constructing a standalone HIP header, and
+:meth:`~pcapkit.protocols.protocol.ProtocolBase.from_data` over a parsed one,
+raised ``AttributeError: 'HIP' object has no attribute '_info'``.
+
+Every case builds its own octets in memory and reads no capture. :class:`HIP`
+is imported inside each test, after
+:func:`~tests._support.reimport_once_per_class`, not at module load.
+
+"""
+
+import importlib.util
+import unittest
+
+from tests._support import reimport_once_per_class
+
+RUNTIME_DEPS = ('tbtrim', 'aenum', 'chardet', 'dictdumper')
+HAS_RUNTIME = all(importlib.util.find_spec(name) is not None for name in RUNTIME_DEPS)
+
+#: Header fields shared by every HIP packet built here, as in
+#: :data:`examples.generators.options.HIP_BASE`.
+HIP_BASE = {
+    'next': 59, 'packet': 1, 'checksum': b'\x00\x00',
+    'controls_anonymous': False, 'shit': 0, 'rhit': 0, 'payload': b'',
+}
+
+
+@unittest.skipUnless(HAS_RUNTIME, 'runtime dependencies not installed')
+class TestHIPFromDataAlias(unittest.TestCase):
+    """Pin ``alias`` on the paths that decode a next layer."""
+
+    def setUp(self) -> None:
+        reimport_once_per_class(self)
+
+    @staticmethod
+    def _parameters() -> 'list':
+        from pcapkit.const.hip.parameter import Parameter
+
+        return [(Parameter.R1_COUNTER, {'counter': 0x0123456789abcdef})]
+
+    def _octets(self, version: 'int') -> 'bytes':
+        from pcapkit.protocols.internet.hip import HIP
+
+        return HIP(parameters=self._parameters(), extension=True,
+                   version=version, **HIP_BASE).data
+
+    def test_construct_standalone_header(self) -> None:
+        from pcapkit.protocols.internet.hip import HIP
+
+        for version in (1, 2):
+            with self.subTest(version=version):
+                proto = HIP(parameters=self._parameters(), version=version, **HIP_BASE)
+                self.assertEqual(proto.alias, f'HIPv{version}')
+                self.assertEqual(proto.data, self._octets(version))
+
+    def test_parse_standalone_header(self) -> None:
+        from pcapkit.protocols.internet.hip import HIP
+
+        for version in (1, 2):
+            with self.subTest(version=version):
+                octets = self._octets(version)
+                proto = HIP(octets, len(octets))
+                self.assertEqual(proto.alias, f'HIPv{version}')
+                self.assertEqual(str(proto.protochain).split(':')[0], f'HIPv{version}')
+
+    def test_from_data_rebuilds_extension_header_byte_for_byte(self) -> None:
+        from pcapkit.protocols.internet.hip import HIP
+
+        for version in (1, 2):
+            with self.subTest(version=version):
+                octets = self._octets(version)
+                parsed = HIP(octets, len(octets), extension=True)
+                rebuilt = HIP.from_data(parsed.info)
+                self.assertEqual(rebuilt.data, octets)
+                self.assertEqual(rebuilt.alias, f'HIPv{version}')
+                self.assertEqual(rebuilt.info.version, version)
+
+
+if __name__ == '__main__':
+    unittest.main()