fix(protocols): compose IPv6_Ext.id() from its direct concrete members (#2462)

- IPv6_Ext.id() returns the names of its direct concrete subclasses, as
  IP.id() and IPsec.id() do, so the 'IPv6_Ext' selector matches every member.
- HOPOPT, IPv6_Route, IPv6_Frag, IPv6_Opts, MH and HIP gain an id() narrowed
  to their own class name; AH and ESP already narrow theirs.
- The "must define" Warning and REQUIRED_OVERRIDES list id().
- A fallback IPv6_Ext layer no longer equals 'IPv6_Ext' with ==, as IPv4
  does not equal 'IP'; the id() docstring says so and a test pins it.
- Tests cover each member and 'IPsec' on parsed packets, and a malformed
  HOPOPT parsed by IPv6_Ext, which matches every member name.

Closes #2462

Author: JarryShaw

docs/source/pcapkit/protocols/internet/hip.rst

@@ -37,6 +37,8 @@ Octets      Bits        Name                    Description
    .. autoproperty:: protocol
    .. autoproperty:: protochain
 
+   .. automethod:: id
+
    .. automethod:: register_parameter
 
    .. automethod:: read

docs/source/pcapkit/protocols/internet/hopopt.rst

@@ -28,6 +28,8 @@ Octets      Bits        Name                    Description
    .. autoproperty:: protocol
    .. autoproperty:: protochain
 
+   .. automethod:: id
+
    .. automethod:: register_option
 
    .. automethod:: read

docs/source/pcapkit/protocols/internet/ipv6_ext.rst

@@ -45,6 +45,8 @@ instead of clipping it.
    .. autoproperty:: payload
    .. autoproperty:: protochain
 
+   .. automethod:: id
+
    .. automethod:: read
    .. automethod:: make
 

docs/source/pcapkit/protocols/internet/ipv6_frag.rst

@@ -31,6 +31,8 @@ Octets      Bits        Name                    Description
    .. autoproperty:: protocol
    .. autoproperty:: protochain
 
+   .. automethod:: id
+
    .. automethod:: read
    .. automethod:: make
 

docs/source/pcapkit/protocols/internet/ipv6_opts.rst

@@ -28,6 +28,8 @@ Octets      Bits        Name                    Description
    .. autoproperty:: protocol
    .. autoproperty:: protochain
 
+   .. automethod:: id
+
    .. automethod:: register_option
 
    .. automethod:: read

docs/source/pcapkit/protocols/internet/ipv6_route.rst

@@ -29,6 +29,8 @@ Octets      Bits        Name                    Description
    .. autoproperty:: protocol
    .. autoproperty:: protochain
 
+   .. automethod:: id
+
    .. automethod:: register_routing
 
    .. automethod:: read

docs/source/pcapkit/protocols/internet/mh.rst

@@ -36,6 +36,8 @@ Octets      Bits        Name                    Description
    .. autoproperty:: protocol
    .. autoproperty:: protochain
 
+   .. automethod:: id
+
    .. automethod:: register_message
    .. automethod:: register_option
    .. automethod:: register_extension

pcapkit/protocols/internet/hip.py

@@ -747,6 +747,16 @@ def register_parameter(cls, code: 'Enum_Parameter', meth: 'str | tuple[Parameter
             warn(f'parameter {code} already registered, overwriting', RegistryWarning)
         cls.__parameter__[code] = meth
 
+    @classmethod
+    def id(cls) -> 'tuple[Literal["HIP"]]':  # type: ignore[override]
+        """Index ID of the protocol.
+
+        Returns:
+            Index ID of the protocol.
+
+        """
+        return ('HIP',)
+
     ##########################################################################
     # Data models.
     ##########################################################################

pcapkit/protocols/internet/hopopt.py

@@ -417,6 +417,16 @@ def register_option(cls, code: 'Enum_Option', meth: 'str | tuple[OptionParser, O
             warn(f'option {code} already registered, overwriting', RegistryWarning)
         cls.__option__[code] = meth
 
+    @classmethod
+    def id(cls) -> 'tuple[Literal["HOPOPT"]]':  # type: ignore[override]
+        """Index ID of the protocol.
+
+        Returns:
+            Index ID of the protocol.
+
+        """
+        return ('HOPOPT',)
+
     ##########################################################################
     # Data models.
     ##########################################################################

pcapkit/protocols/internet/ipv6_ext.py

@@ -223,14 +223,15 @@ class keywords implement it.
 
     Warning:
         A subclass **must** define :attr:`name`, :attr:`alias`,
-        :attr:`protocol`, :attr:`length` and :meth:`__index__` itself. Each
-        carries this class's *fallback-role* answer, which is wrong for a
-        header with an identity of its own: it would report itself as
-        ``IPv6 Extension Header`` / ``IPv6-Ext``, read its length off a data
-        model that is not its own, and :meth:`__index__` would raise rather
-        than return its IANA number. The language cannot enforce the override,
-        so ``tests/protocols/internet/test_ipv6_ext_unit.py`` does, over every
-        subclass discovered at runtime.
+        :attr:`protocol`, :attr:`length`, :meth:`__index__` and :meth:`id`
+        itself. Each carries this class's *fallback-role* answer, which is
+        wrong for a header with an identity of its own: it would report itself
+        as ``IPv6 Extension Header`` / ``IPv6-Ext``, read its length off a data
+        model that is not its own, :meth:`__index__` would raise rather than
+        return its IANA number, and :meth:`id` would match every member's name
+        rather than narrow to its own class name. The language cannot enforce
+        the override, so ``tests/protocols/internet/test_ipv6_ext_unit.py``
+        does, over every subclass discovered at runtime.
 
     .. versionadded:: 1.5.0
 
@@ -379,6 +380,22 @@ def protochain(self) -> 'ProtoChain | NoReturn':
     # Methods.
     ##########################################################################
 
+    @classmethod
+    def id(cls) -> 'tuple[Literal["HOPOPT"], Literal["IPv6_Route"], Literal["IPv6_Frag"], Literal["ESP"], Literal["AH"], Literal["IPv6_Opts"], Literal["MH"], Literal["HIP"]]':  # pylint: disable=line-too-long
+        """Index ID of the protocol.
+
+        Returns:
+            Index ID of every direct concrete subclass, each of which narrows
+            its own :meth:`id` to itself. A header parsed by this class as the
+            generic fallback therefore matches every one of these names.
+
+        Note:
+            ``== 'IPv6_Ext'`` is :data:`False`, as ``== 'IP'`` is on
+            :class:`~pcapkit.protocols.internet.ipv4.IPv4`; ``== IPv6_Ext`` is :data:`True`.
+
+        """
+        return ('HOPOPT', 'IPv6_Route', 'IPv6_Frag', 'ESP', 'AH', 'IPv6_Opts', 'MH', 'HIP')
+
     def read(self, length: 'Optional[int]' = None, *,  # pylint: disable=arguments-differ
              extension: 'bool' = False, **kwargs: 'Any') -> '_PT':
         """Read a generically-parsed IPv6 extension header.