swaitsandClaude Opus 4.7
9232c16f7c
A frozen spec is only meaningful if it's paired with the corpus that was current at release time — otherwise a v0.1.0 reader follows "see corpus/payloads/ack/" and lands on a file whose test vectors may have changed since v0.1.0 was cut. Three changes: 1. `cut-version` now copies BOTH src/ AND corpus/ into the snapshot directory. A release is the pair, not just the text. 2. The corpus URL rewriting in cut-version now retargets /tree/main/corpus -> /tree/main/versions/<v>/corpus (and the blob variant). This lets the link resolve on GitHub from main alone — no git tag required, since the frozen copy is a real path under main. Downgrades the "tag is REQUIRED" message from last commit back to "optionally tag the commit". 3. The frozen corpus's spec_ref fields get rewritten too: from `src/04-payload-ack.md` to `versions/<v>/04-payload-ack.md`, so a reader following a test vector lands on the spec text the vector was paired with at release time. versions/v0.1.0/ regenerated from scratch via `just cut-version v0.1.0` to pick up the corpus snapshot + the new sed patterns. The release is now self-consistent: v0.1.0 spec links go to v0.1.0 corpus, which links back to v0.1.0 spec. 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/main/versions/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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