swaitsandClaude Opus 4.7
44305a06db
First cut release. Snapshots ./src/ as ./versions/v0.1.0/ via `just cut-version v0.1.0` (22 files: 21 chapter MDs + SUMMARY.md). Deployed alongside `latest` at: https://swaits.github.io/meshcore-spec/v0.1.0/ Also: - CHANGELOG.md adopts Keep a Changelog-style version sections. Future entries land under [Unreleased] and graduate to a version heading when cut. The existing date-stamped pass entries stay put as a historical record of the work captured in v0.1.0. - README.md fixes a stale "per vX.Y.Z tag" mention left over from the tag-based versioning model, and links the current release explicitly. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
69 lines
1.9 KiB
Markdown
69 lines
1.9 KiB
Markdown
# MeshCore Protocol Specification
|
|
|
|
## Section 12: Payload — Control
|
|
|
|
### Overview
|
|
|
|
The CONTROL payload carries control and discovery data. Control packets are raw
|
|
byte payloads whose structure is determined by the first byte. A subset of
|
|
control packets (those with bit 7 of the first byte set) are restricted to
|
|
zero-hop delivery only.
|
|
|
|
### Payload Type
|
|
|
|
Header payload type field: `0x0B` (CONTROL)
|
|
|
|
### Wire Format
|
|
|
|
```
|
|
0
|
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
|
| Control Byte | Data... |
|
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
|
```
|
|
|
|
### Fields
|
|
|
|
| Field | Offset | Size | Type | Description |
|
|
|-------|--------|------|------|-------------|
|
|
| control_byte | 0 | 1 byte | uint8 | Control type identifier |
|
|
| data | 1 | variable | raw | Control-specific data |
|
|
|
|
### Zero-Hop Restriction
|
|
|
|
When bit 7 (`0x80`) of the control byte is set, the packet is restricted to
|
|
zero-hop delivery only. The reference implementation enforces this:
|
|
|
|
- If `(payload[0] & 0x80) != 0` AND the packet is direct-routed:
|
|
- It is processed only if `getPathHashCount() == 0`.
|
|
- It is NOT forwarded to other nodes.
|
|
|
|
### Discovery Protocols
|
|
|
|
Control packets are commonly used for node discovery. The specific sub-protocol
|
|
formats are application-defined, but typically include:
|
|
|
|
- **Discovery Request**: Sent zero-hop to find nearby nodes
|
|
- **Discovery Response**: Contains node type, name, SNR, and other metadata
|
|
|
|
### Encoding
|
|
|
|
1. Construct the raw control data bytes.
|
|
2. If the control packet should be zero-hop only, set bit 7 of the first byte.
|
|
3. Copy data to payload, set payload_len.
|
|
|
|
### Constraints
|
|
|
|
- Payload MUST be at least 1 byte (the control byte).
|
|
- Maximum payload: 184 bytes (MAX_PACKET_PAYLOAD).
|
|
|
|
### Cross-References
|
|
|
|
- [Section 17: Routing](17-routing.md) — Zero-hop delivery
|
|
- Test vectors: `corpus/payloads/control/`
|
|
|
|
### Reference Implementation
|
|
|
|
- `Mesh::createControlData()` in `src/Mesh.cpp` — Encoding
|
|
- `Mesh::onRecvPacket()`, CONTROL handling — Zero-hop check and delivery
|