swaitsandClaude Opus 4.7
f83d4088e3
Every "Test vectors: \`corpus/...\`" mention in the spec is now a markdown link pointing at the corresponding file or directory on GitHub. Each version build resolves its links to the correct git ref: - /latest/ -> https://github.com/swaits/meshcore-spec/tree/main/corpus/... - /v0.1.0/ -> https://github.com/swaits/meshcore-spec/tree/v0.1.0/corpus/... - future /vX.Y.Z/ -> /tree/vX.Y.Z/corpus/... Two changes: 1. src/*.md (18 files): the inline-code corpus paths in each "Cross-References" section are now markdown links. Directories point at /tree/main/corpus/..., individual .json files point at /blob/main/corpus/.... CHANGELOG and other non-corpus main links are intentionally left pointing at main — the canonical history lives there regardless of which version you're reading. 2. justfile: `cut-version` now also runs a sed over the snapshot's *.md files replacing /tree/main/corpus -> /tree/<VERSION>/corpus and /blob/main/corpus -> /blob/<VERSION>/corpus. So a freshly-cut version is self-consistent. versions/v0.1.0/* regenerated by re-running `just cut-version v0.1.0` after the new src/ links + recipe sed landed. Tagging the release commit (`git tag v0.1.0`) is now REQUIRED — not "optional" — because the rendered /v0.1.0/ pages reference /tree/v0.1.0/corpus/... on GitHub. Without the tag the links 404. cut-version's output now says so. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
69 lines
2.0 KiB
Markdown
69 lines
2.0 KiB
Markdown
# MeshCore Protocol Specification
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## Section 12: Payload — Control
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### Overview
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The CONTROL payload carries control and discovery data. Control packets are raw
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byte payloads whose structure is determined by the first byte. A subset of
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control packets (those with bit 7 of the first byte set) are restricted to
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zero-hop delivery only.
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### Payload Type
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Header payload type field: `0x0B` (CONTROL)
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### Wire Format
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```
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0
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Control Byte | Data... |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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```
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### Fields
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| Field | Offset | Size | Type | Description |
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|-------|--------|------|------|-------------|
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| control_byte | 0 | 1 byte | uint8 | Control type identifier |
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| data | 1 | variable | raw | Control-specific data |
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### Zero-Hop Restriction
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When bit 7 (`0x80`) of the control byte is set, the packet is restricted to
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zero-hop delivery only. The reference implementation enforces this:
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- If `(payload[0] & 0x80) != 0` AND the packet is direct-routed:
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- It is processed only if `getPathHashCount() == 0`.
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- It is NOT forwarded to other nodes.
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### Discovery Protocols
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Control packets are commonly used for node discovery. The specific sub-protocol
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formats are application-defined, but typically include:
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- **Discovery Request**: Sent zero-hop to find nearby nodes
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- **Discovery Response**: Contains node type, name, SNR, and other metadata
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### Encoding
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1. Construct the raw control data bytes.
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2. If the control packet should be zero-hop only, set bit 7 of the first byte.
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3. Copy data to payload, set payload_len.
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### Constraints
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- Payload MUST be at least 1 byte (the control byte).
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- Maximum payload: 184 bytes (MAX_PACKET_PAYLOAD).
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### Cross-References
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- [Section 17: Routing](17-routing.md) — Zero-hop delivery
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- Test vectors: [`corpus/payloads/control/`](https://github.com/swaits/meshcore-spec/tree/v0.1.0/corpus/payloads/control/)
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### Reference Implementation
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- `Mesh::createControlData()` in `src/Mesh.cpp` — Encoding
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- `Mesh::onRecvPacket()`, CONTROL handling — Zero-hop check and delivery
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