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release: v0.1.0

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>

2026-05-12 10:04:40 -06:00

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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

Construct the raw control data bytes.
If the control packet should be zero-hop only, set bit 7 of the first byte.
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 — 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

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