Archived
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12 KiB
Markdown
294 lines
12 KiB
Markdown
# donglora-bridge
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[](https://github.com/swaits/donglora-bridge/actions/workflows/ci.yml)
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[](LICENSE)
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**donglora-bridge** relays raw LoRa packets over the internet. Every packet your
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radio hears is forwarded to every other bridge running the same passphrase, and
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their radios retransmit it locally. Because it operates on raw packets, it works
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with any protocol built on LoRa --
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[Meshtastic](https://meshtastic.org/),
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[MeshCore](https://github.com/rocketgithub/meshcore-firmware),
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or anything else -- simultaneously and without configuration. If your radio can
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hear it, the bridge will relay it.
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[LoRa](https://en.wikipedia.org/wiki/LoRa) is a long-range, low-power wireless
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modulation used by off-grid mesh networks. A single radio might cover a few
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kilometers. This bridge removes that limit, extending a local LoRa network
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across a larger geographic area.
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There is no central server. Bridges discover each other automatically using the
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[Mainline DHT](https://en.wikipedia.org/wiki/Mainline_DHT) and communicate
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through an encrypted peer-to-peer gossip swarm.
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## What you need
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### 1. A DongLoRa radio
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[DongLoRa](https://github.com/swaits/donglora) is open-source firmware that
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turns a supported LoRa development board (such as a Heltec WiFi LoRa 32 or
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similar ESP32+SX1262 board) into a USB LoRa dongle. You will need to:
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1. **Get a board** -- any ESP32 board with an SX1262 LoRa radio that DongLoRa
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supports. See the [DongLoRa README](https://github.com/swaits/donglora) for
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the full list.
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2. **Flash the DongLoRa firmware** onto the board. Instructions are in the
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DongLoRa repository.
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3. **Plug it in via USB**. The board appears as a serial device
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(e.g. `/dev/ttyACM0` on Linux).
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### 2. (Optional) donglora-mux
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The bridge works fine without the mux -- it connects directly to the USB device.
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The mux is only needed if you want multiple programs to share a single DongLoRa
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radio at the same time (e.g. running two bridges with different configs, or a
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bridge alongside another donglora-client program).
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```sh
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cargo install donglora-mux
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```
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Run `donglora-mux` before starting the bridge. The bridge auto-detects the mux
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when it's running and falls back to direct USB serial when it's not.
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### 3. donglora-bridge (this project)
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Install via cargo:
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```sh
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cargo install donglora-bridge
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```
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Or via [mise](https://mise.jdx.dev/):
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```sh
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mise use -g cargo:donglora-bridge
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```
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Or build from source:
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```sh
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git clone https://github.com/swaits/donglora-bridge.git
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cd donglora-bridge
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cargo build --release
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```
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Requires Linux. macOS may work but is untested.
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## Quick start
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### 1. Plug in your DongLoRa board and (optionally) start the mux
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```sh
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donglora-mux # optional -- skip if not sharing the radio
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```
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### 2. Run the bridge
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```sh
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donglora-bridge
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```
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On first run, an interactive wizard walks you through configuration:
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- **Passphrase** (required) -- every bridge using the same passphrase joins the
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same network. Pick something unique to your group.
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- **Radio settings** -- frequency, bandwidth, spreading factor, etc. The
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defaults match MeshCore US/Canada recommended values. If you're bridging a
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MeshCore network, just press Enter through these.
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The config is saved to `~/.config/donglora-bridge/config.toml`. To change it
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later, run `donglora-bridge config`.
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### 3. That's it
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The TUI shows real-time stats. On another machine (or continent), repeat the
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same steps with the same passphrase. The two bridges will discover each other
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via DHT and start relaying packets within seconds.
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```sh
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donglora-bridge # TUI mode (default)
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donglora-bridge --log-only # headless mode (structured logs to stdout)
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donglora-bridge --config path.toml # custom config file
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donglora-bridge config # re-run setup wizard
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```
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### Running multiple bridges
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To run more than one bridge on the same machine (e.g. bridging two separate
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MeshCore networks), create a config file per bridge and run each with
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`--config`:
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```sh
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donglora-bridge --config ~/bridge-network-a.toml
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donglora-bridge --config ~/bridge-network-b.toml
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```
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Each config can specify a different passphrase, different radio settings, and
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(if using the mux) share the same radio. Without the mux, each bridge needs its
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own USB dongle and an explicit `port` in its config to avoid both trying to open
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the same device.
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## Features
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- **Gossip swarm** -- broadcast packets via [iroh-gossip](https://github.com/n0-computer/iroh), a QUIC-based overlay network
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- **Zero-config peer discovery** -- automatic bootstrapping via BitTorrent mainline DHT ([BEP44](http://bittorrent.org/beps/bep_0044.html) mutable items)
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- **Content-hash deduplication** -- blake3 hashing suppresses duplicate packets across all bridges
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- **Air-time-aware rate limiting** -- token bucket calculated from LoRa radio parameters (Semtech LoRa time-on-air formula)
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- **Real-time terminal UI** -- network status, radio config, packet log, activity sparklines
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- **Resilient radio connection** -- exponential backoff reconnection with liveness pings
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- **Headless mode** -- structured logs to stdout for servers (`--log-only`)
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- **Interactive setup wizard** -- guided first-run configuration
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- **Shared passphrase security** -- all cryptographic keys derived deterministically from a single passphrase
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## TUI overview
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| Panel | Content |
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|-------|---------|
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| **Network** | Topic ID, peer count, DHT status, last publish time |
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| **Radio** | Device, frequency, bandwidth, SF, CR, sync word, TX power, preamble, CAD |
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| **Stats** | Uptime, RF/Net RX/TX, dedup hits, rate limit drops, queue drops |
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| **Packet Log** | Scrolling log: age, hash, RF/Net direction, size, RSSI, SNR, action |
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| **Activity** | Sparkline charts: RX rate, TX rate, average SNR (1-second buckets, 5-minute window) |
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Press `q` or `Ctrl+C` to shut down gracefully.
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## Configuration
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Default location: `~/.config/donglora-bridge/config.toml`
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```toml
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[radio]
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# port = "/dev/ttyACM0" # serial port (omit for auto-detect: tries mux, then USB)
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frequency = 910525000 # Hz (default: 910.525 MHz)
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bandwidth = "62.5kHz" # 7.8kHz, 10.4kHz, 15.6kHz, 20.8kHz, 31.25kHz,
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# 41.7kHz, 62.5kHz, 125kHz, 250kHz, 500kHz
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spreading_factor = 7 # 7-12
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coding_rate = 5 # 5-8 (meaning 4/5 to 4/8)
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sync_word = 0x3444 # hex, 2 bytes
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tx_power = "22" # dBm integer or "max"
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preamble = 16 # symbols
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cad = true # channel activity detection
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[bridge]
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passphrase = "your-shared-secret" # REQUIRED: all bridges with same passphrase join the same swarm
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dedup_window_secs = 300 # duplicate suppression window (default: 5 minutes)
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tx_queue_size = 32 # max pending radio TX packets
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# rate_limit_pps = 5.0 # optional: override calculated TX rate (packets/sec)
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# log_file = "/path/to/bridge.log" # optional: override log path
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```
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Default radio settings match MeshCore US/Canada recommended parameters.
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## How it works
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### Passphrase key derivation
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A single passphrase deterministically derives three values:
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1. **Topic ID** -- `blake3(APP_PREFIX + passphrase)` -- identifies the gossip swarm
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2. **DHT signing key** -- ed25519 from `SHA-256(APP_PREFIX + "sign:" + passphrase)` -- authenticates DHT records
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3. **DHT salt** -- first 20 bytes of `SHA-256(APP_PREFIX + "salt:" + passphrase)` -- namespaces the DHT key
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All nodes with the same passphrase compute identical keys and automatically join
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the same network.
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### Gossip swarm
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Each bridge creates an ephemeral iroh endpoint (fresh ed25519 identity per
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launch) and subscribes to the derived topic. Radio packets are wrapped in a
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`GossipFrame` (32-byte sender ID + RSSI + SNR + payload) and broadcast to all
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neighbors. Received frames are decoded and queued for radio transmission.
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### DHT peer discovery
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Peers find each other through BitTorrent's mainline DHT using BEP44 mutable
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items. Peer lists are encoded as `[count:u16 LE][id:32B]...` (max 27 peers per
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record to stay under the 1000-byte value limit).
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**When alone** (no neighbors): reads DHT every 3 seconds, merge-publishes every
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30 seconds (preserves existing peers, never destructive).
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**When connected**: relaxed 5-minute heartbeat with random jitter. Publishes
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self + live neighbors only (purges stale peers).
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**On shutdown**: publishes neighbors without self, so other nodes can still
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bootstrap from live peers.
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### Deduplication
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Every packet payload is hashed with blake3 (32 bytes). A time-bounded cache
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(default 300s, pruned every 30s) suppresses duplicates from both radio and
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gossip directions.
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### Rate limiting
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A token bucket rate limiter prevents radio channel saturation. The rate is
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calculated from the LoRa air time formula (Semtech SX1276):
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```
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air_time = preamble_time + payload_symbol_count * symbol_time
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rate = 0.5 / air_time (50% duty cycle target)
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```
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Default burst allowance is 3 packets. The rate can be manually overridden with
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`rate_limit_pps` in the config.
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### Radio communication
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A dedicated blocking thread communicates with the DongLoRa hardware via
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`donglora-client`. Features:
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- **Config negotiation**: reads existing config first; only sets if needed
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- **Exponential backoff reconnection**: 250ms to 5s, resets after 5s of uptime
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- **Liveness pings**: every 2s of idle, detects silently-dead connections
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- **SNR filtering**: drops packets below the demodulation floor
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### Architecture
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```
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┌─────────────────────────────────────┐
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│ donglora-bridge │
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│ │
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DongLoRa ┌────────┐│ ┌────────┐ ┌──────┐ ┌───────┐ │ Internet
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USB dongle◄─┤ Radio ├┤◄─┤ Router ├──►│Gossip├──►│ iroh ├──┤◄──► Other
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│ Thread ││─►│ (dedup ││ │Swarm │ │ QUIC │ │ Bridges
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└────────┘│ │ rate ││ └──┬───┘ └───────┘ │
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│ │ limit)│| │ │
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│ └────────┘│ ┌──┴───┐ │
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│ ▲ │ │ DHT │ │
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│ │ │ │(peer │ │
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│ ┌──┴──┐ │ │disc.)│ │
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│ │ TUI │ │ └──────┘ │
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│ └─────┘ │ │
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└─────────────────────────────────────┘
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```
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## Testing
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```sh
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cargo test # unit tests + property tests (proptest)
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cargo clippy --all-targets # lint check (pedantic + nursery)
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cargo fmt --check # format check
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cargo mutants # mutation testing (install: cargo install cargo-mutants)
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cargo +nightly fuzz run fuzz_gossip_frame_decode # fuzz testing (requires nightly)
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cargo +nightly fuzz run fuzz_decode_peer_list
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```
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## Troubleshooting
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| Symptom | Cause | Fix |
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| "passphrase is required" | Empty or placeholder passphrase | Run `donglora-bridge config` |
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| No peers found | Passphrase mismatch or firewall | Check passphrase matches; iroh uses QUIC (UDP), DHT uses UDP |
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| Radio disconnected | USB dongle unplugged or mux crash | Check USB connection; bridge will auto-reconnect |
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| Yellow `!` on radio fields | Mux has different radio config | Another client set different params; bridge adopts mux config |
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| Log file location | Default path | `~/.local/state/donglora-bridge/bridge.log` |
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## License
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[MIT](LICENSE)
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