L2TP - Layer Two Tunnelling Protocol¶

pcapkit.protocols.link.l2tp contains L2TP only, which implements extractor for Layer Two Tunnelling Protocol (L2TP) [*], whose structure is described as below:

Octets	Bits	Name	Description
0	0	`l2tp.flags`	Flags and Version Info
0	0	`l2tp.flags.type`	Type (control / data)
0	1	`l2tp.flags.len`	Length
0	2		Reserved (must be zero `x00`)
0	4	`l2tp.flags.seq`	Sequence
0	5		Reserved (must be zero `x00`)
0	6	`l2tp.flags.offset`	Offset
0	7	`l2tp.flags.prio`	Priority
1	8		Reserved (must be zero `x00`)
1	12	`l2tp.ver`	Version (`2`)
2	16	`l2tp.length`	Length (optional by `len`)
4	32	`l2tp.tunnelid`	Tunnel ID
6	48	`l2tp.sessionid`	Session ID
8	64	`l2tp.ns`	Sequence Number (optional by `seq`)
10	80	`l2tp.nr`	Next Sequence Number (optional by `seq`)
12	96	`l2tp.offset`	Offset Size (optional by `offset`)

class pcapkit.protocols.link.l2tp.L2TP(file=None, length=None, **kwargs)[source]¶

Bases: Link[L2TP, L2TP]

This class implements Layer Two Tunnelling Protocol.

property name: Literal['Layer 2 Tunnelling Protocol']¶: Name of current protocol.

property length: int¶: Header length of current protocol.

property type: Literal['control', 'data']¶: L2TP type.

read(length=None, **kwargs)[source]¶

Read Layer Two Tunnelling Protocol.

Structure of L2TP header [RFC 2661]:

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|T|L|x|x|S|x|O|P|x|x|x|x|  Ver  |          Length (opt)         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|           Tunnel ID           |           Session ID          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|             Ns (opt)          |             Nr (opt)          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Offset Size (opt)        |    Offset pad... (opt)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Parameters:

length (Optional[int]) – Length of packet data.
**kwargs (Any) – Arbitrary keyword arguments.

Return type:

L2TP

Returns:

Parsed packet data.

make(version=2, type=<Type.Data: 1>, type_default=None, type_namespace=None, type_reversed=False, priority=False, length=None, tunnel_id=0, session_id=0, ns=None, nr=None, offset=None, payload=b'', **kwargs)[source]¶

Make (construct) packet data.

Parameters:

version (Literal[2]) – L2TP version.
type (Type | IntEnum | IntEnum | str | int) – L2TP type.
type_default (Optional[int]) – Default value of type.
type_namespace (Union[dict[str, int], dict[int, str], Type[IntEnum], Type[IntEnum], None]) – Namespace of type.
type_reversed (bool) – Reversed namespace of type.
priority (bool) – Priority flag.
length (Optional[int]) – Length of packet data.
tunnel_id (int) – Tunnel ID.
session_id (int) – Session ID.
ns (Optional[int]) – Sequence number.
nr (Optional[int]) – Acknowledgement number.
offset (Optional[int]) – Offset size.
payload (bytes | ProtocolBase | Schema) – Payload data.
**kwargs (Any) – Arbitrary keyword arguments.

Return type:

L2TP

Returns:

Constructed packet data.

classmethod _make_data(data)[source]¶

Create key-value pairs from data for protocol construction.

Parameters:: data (L2TP) – protocol data
Return type:: dict[str, Any]
Returns:: Key-value pairs for protocol construction.

classmethod __index__()[source]¶

Numeral registry index of the protocol.

Raises:: UnsupportedCall – This protocol has no registry entry.
Return type:: NoReturn

Header Schemas¶

class pcapkit.protocols.schema.link.l2tp.L2TP(dict_=None, **kwargs)[source]¶

Bases: Schema

Header schema for L2TP packet.

flags: FlagsType = <BitField flags>¶: Flags and version of L2TP packet.

length: int = <ConditionalField length>¶: Length of L2TP packet.

tunnel_id: int = <UInt16Field tunnel_id>¶: Tunnel ID of L2TP packet.

session_id: int = <UInt16Field session_id>¶: Session ID of L2TP packet.

ns: int = <ConditionalField ns>¶: Sequence number of L2TP packet.

nr: int = <ConditionalField nr>¶: Next sequence number of L2TP packet.

offset: int = <ConditionalField offset>¶: Offset size of L2TP packet.

padding: bytes = <ConditionalField padding>¶: Padding of L2TP packet.

payload: bytes = <PayloadField payload>¶: Payload of L2TP packet.

Type Stubs¶

class pcapkit.protocols.schema.link.l2tp.FlagsType[source]¶

Bases: TypedDict

Flags of L2TP packet.

type: int¶: Type of L2TP packet.

len: int¶: Length of L2TP packet.

seq: int¶: Sequence number of L2TP packet.

offset: int¶: Offset size of L2TP packet.

prio: int¶: Priority of L2TP packet.

version: Literal[2]¶: Version of L2TP packet.

Data Models¶

class pcapkit.protocols.data.link.l2tp.L2TP(*args: VT, **kwargs: VT)[source]¶

Bases: Protocol

Data model for L2TP packet.

flags: Flags¶: Flags and version info.

version: int¶: Version.

length: Optional[int]¶: Length.

tunnelid: int¶: Tunnel ID.

sessionid: int¶: Session ID.

ns: Optional[int]¶: Sequence Number.

nr: Optional[int]¶: Next Sequence Number.

offset: Optional[int]¶: Offset Size.

hdr_len: int¶: Header length.

class pcapkit.protocols.data.link.l2tp.Flags(*args: VT, **kwargs: VT)[source]¶

Bases: Data

Data model for L2TP flags and version info.

type: Type¶: Type.

len: bool¶: Length.

seq: bool¶: Sequence.

offset: bool¶: Offset.

prio: bool¶: Priority.

Footnotes