lin

Overview ¶

Package lin decodes a LIN (Local Interconnect Network) bus frame — the low-cost single-wire automotive sub-bus that hangs off CAN for body electronics: door / mirror / seat modules, climate flaps, wiper and rain/light sensors, switch panels. It is a real automotive reverse-engineering / pentest surface (cheap to tap, often unauthenticated) and is distinct from the CAN family the other automotive decoders cover.

Wrap-vs-native judgement ¶

Native. A LIN frame is a fully-public fixed structure (LIN 2.x /
ISO 17987): an optional 0x55 sync byte, a Protected Identifier
(PID = 6-bit frame ID + 2 parity bits), 1-8 data bytes, and a
checksum. The PID parity is two XOR equations over the ID bits;
the checksum is the inverted carry-folded sum of the data (classic)
or of the PID + data (enhanced). All deterministic byte/bit math —
reimplemented from the standard, no new dependency, no shell-out.

What this covers ¶

• The Protected Identifier: the 6-bit frame ID, the parity bits, and a recompute of the parity (reported valid / invalid), plus a frame-class note (signal frame / master-request or slave-response diagnostic / user-defined / reserved).
• The data bytes (length inferred as frame_length − PID − checksum).
• The checksum: both the classic (data-only, LIN 1.x + diagnostics) and the enhanced (PID + data, LIN 2.x) forms are computed and the frame's checksum is reported as classic / enhanced / invalid.

Deliberately deferred ¶

The signal (DBC/LDF) interpretation of the data bytes needs the
vehicle's LIN Description File and is not attempted — the raw data
is surfaced. The break field and bit-timing are physical-layer and
upstream of the captured bytes.