Link Layer Base Protocol

pcapkit.protocols.link.link contains Link, which is a base class for link layer protocols, e.g. ARP/InARP, Ethernet, L2TP and VLAN.

class pcapkit.protocols.link.link.Link[_PT: Data, _ST: Schema](file=None, length=None, **kwargs)

Bases: ProtocolBase[_PT, _ST], Generic[_PT, _ST]

Abstract base class for link layer protocol family.

This class supports parsing of the following protocols, which are registered in the self.__proto__ attribute:

Index	Protocol
Address_Resolution_Protocol	pcapkit.protocols.link.arp.protocol.ARP
Reverse_Address_Resolution_Protocol	pcapkit.protocols.application.rarp.protocol.RARP
Customer_VLAN_Tag_Type	pcapkit.protocols.link.c_tag.protocol.C_Tag
IEEE_Std_802_1Q_Service_VLAN_tag_identifier	pcapkit.protocols.link.s_tag.protocol.S_Tag
Internet_Protocol_version_4	pcapkit.protocols.internet.ipv4.protocol.IPv4
Internet_Protocol_version_6	pcapkit.protocols.internet.ipv6.protocol.IPv6
0x8137	pcapkit.protocols.internet.ipx.protocol.IPX

__layer__: Literal['Link'] = 'Link'

Layer of protocol.

__proto__: DefaultDict[int | EtherType, ModuleDescriptor[ProtocolBase] | Type[ProtocolBase]]

Protocol index mapping for decoding next layer, see self._decode_next_layer & self._import_next_layer.

__proto_key__: ClassVar[tuple[Type[EnumRegistry], bool]]

What __proto__ is keyed by – the enum a key must be a member of, and whether a bare int is a valid key too. Declared by the class owning the registry and read by register_protocol_code(), so a code= key is checked as register_ethertype() checks its own. A class keeping its own registry, such as Loopback, declares its own pairing or none (#2268).

property layer: Literal['Link']

Protocol layer.

classmethod register(code, protocol)

Register a new protocol class.

Notes

The fully qualified class name of the new protocol class should be {protocol.module}.{protocol.name}.

Parameters:

• code (EtherType) – protocol code as in EtherType

• protocol (ModuleDescriptor[ProtocolBase] | Type[ProtocolBase]) – module descriptor or a ProtocolBase subclass

Raises:

pcapkit.utilities.exceptions.RegistryError – If protocol is not a class, or not a ProtocolBase subclass.

Warns:

pcapkit.utilities.warnings.RegistryWarning – If this EtherType is already registered, naming the displaced entry and its replacement so a caller can tell what was lost. Fires only when the incumbent differs from the replacement – see Protocol.register for the guard this shares with register_protocol, and for the shipped descriptor that a restore puts back (#1504).

Changed in version 1.3.0: Takes the protocol as one protocol argument, a ModuleDescriptor or a ProtocolBase subclass, in place of the module and class_ names.

classmethod from_data(data, **kwargs)

Create protocol instance from data.

Parameters:

• data (_PT | dict[str, Any]) – Protocol data.

• **kwargs (Any) – Construction keywords, as for Protocol.from_data.

Return type:

Self

Returns:

Protocol instance, cut back to what was captured when the header it was parsed from was cut short (#1458).

__post_init__(file=None, length=None, **kwargs)

Post initialisation hook.

Parameters:

• file (IO[bytes] | bytes | None) – Source packet stream.

• length (int | None) – Length of packet data.

• **kwargs (Any) – Arbitrary keyword arguments.

Return type:

None

Notes

A header the data ends inside keeps that in its info, so that from_data() rebuilds only what was captured (#1458).