Module l2tp 

L2TP (Layer 2 Tunneling Protocol) layer implementation.

Implements L2TPv2 as defined in RFC 2661.

Header Format

Bits:  0 1 2 3 4 5 6 7 | 8 9 10 11 12 13 14 15
       T L X X S X X O | P X  X  X  X  Ver(4 bits)

Where:

• T (bit 0): Message type: 0=data, 1=control
• L (bit 1): Length bit; if set, Length field is present
• S (bit 4): Sequence bit; if set, Ns and Nr fields are present
• O (bit 6): Offset bit; if set, Offset Size/Pad fields are present
• P (bit 8): Priority (data messages only)
• Ver (12-15): Must be 2 for L2TPv2

Fields present in order:

1. Flags+Version (2 bytes, always)
2. Length (2 bytes, only if L=1)
3. Tunnel ID (2 bytes, always)
4. Session ID (2 bytes, always)
5. Ns (2 bytes, only if S=1)
6. Nr (2 bytes, only if S=1)
7. Offset Size (2 bytes, only if O=1)
8. Offset Pad (variable, only if O=1)

Re-exports

pub use builder::L2tpBuilder;

Modules

builder

L2TP packet builder.

Structs

L2tpLayer

L2TP layer — a zero-copy view into a packet buffer.

Constants

L2TP_MIN_HEADER_LEN

Minimum L2TP header: flags+version (2) + tunnel_id (2) + session_id (2) = 6 bytes.

L2TP_PORT

L2TP UDP port.

L2TP_VERSION

L2TP version number (bits 12-15 of the flags word).

Statics

L2TP_FIELD_NAMES

Field names exported for Python/generic access.