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Johnathan Corgan
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Everything the release needs except the version number, which stays at 0.5.0-dev until the tag. The changelog entry covers only the work that is new on this line. The point release's forty-six entries arrived under their own heading with the forward merge and are left alone; the twenty that remained are regrouped by topic and eight more added for changes no entry covered. Three of those eight matter to someone upgrading. Five root modules and four re-exports left the public library surface and Node::connections narrowed, none of it recorded anywhere; the entry names what to use instead and distinguishes the removed connection-phase enum from the Noise type of the same name, which is a different type that still exists. Tracing targets moved, so an existing RUST_LOG filter stops matching rather than erroring. And the handshake resend interval key no longer governs the first resend, which is now a constant, though it still governs later ones. Seven more entries cover the work that landed after the first content pass was written: the experimental native datagram API, the fipsctl probe diagnostic, per-instance transport addressing, the app-owned UDP socket seam, and the connect, disconnect and path-MTU fixes. The four bug fixes among them all reach the deployed line, so the release notes no longer claim this release carries exactly one fix for a shipped bug; it carries four. There is no security section, because after the split every security entry belongs to the point release. The release notes say so plainly rather than leaving a reader upgrading across both releases to conclude this one carries no security work. The notes are organized by audience, since the release spans OpenWrt routers, embedders, FreeBSD, and the existing platforms, and a single list serves none of them. The native datagram API is given a section of its own rather than folded into the embedding seam: it is a client-facing API rather than a way to host a node, and its one rule with no Berkeley-socket counterpart, that the v1 wire carries no half-close, needs to be somewhere a client author will read it. FreeBSD is advertised as supported on x86_64 only, stated wherever the platform appears. Android is advertised as an embedding seam and not as a supported platform: a compile-gated library surface with no artifact and no host application guide. The configuration table rename is carried through every shipped file that taught the old spelling: nine documentation files, the OpenWrt sample config and a test generator, twenty-two sites in all. Guides written this same cycle were among them, which is how the omission was found. The documentation that arrived with the native API was checked for the same omission and was already clean. The compatibility tests keep the old spelling deliberately, since they exist to test the fold. The changelog section is the fold of master's [Unreleased], not a snapshot of it. An earlier version of this commit took a copy that then drifted, so each section ended up holding a bullet the other did not and re-folding them would have picked a winner silently. Both causes were fixed on master instead — the NixOS module had never been recorded there, and the pre-release batch of fixes was new — so [Unreleased] is a strict superset and this is a copy rather than a merge. [0.5.0] carries all forty-six bullets byte for byte, [Unreleased] is empty, and [0.4.2] is untouched, checked by hashing it against master's copy. The BLE work landed after the content pass and gets one summary entry in the changelog and one section in the release notes rather than nine bullets: the ble_available gate replacing target_os = "linux", packet-boundary recovery for stream-oriented backends, peer recognition by node identity instead of a rotating link address, the L2CAP PSM moving into the backend seam and onto the advertisement, the embedder-supplied Android radio, bounded probe retry, and inbound handshakes moved off the accept loop. The two release-notes copies no longer share their link paths. Relative links resolve from one directory only, so the seven written for docs/releases/ all 404ed from the root copy. The root copy now uses paths from the repository root and the versioned copy keeps the ../ form; both sets were resolved against the tree. The same two links are broken the same way in the v0.4.0 through v0.4.2 notes, left as shipped history. The contributor tallies are re-derived against maint..HEAD rather than adjusted: twenty commits from outside the project and 171 from me, with Arjen at fifteen and fr34aky at two. An earlier count of twelve and 138 was carried from a measurement taken three days before this content was written, and the BLE branch widened the gap after it. Arjen's NixOS flake module, the UDP sin6_scope_id fix and most of the BLE rework were uncredited, as was fr34aky's L2CAP PSM seam. They want one last re-derive at tag time if anything lands before the tag. A sweep of all 99 tracked markdown files against the tree corrected fifty-three of them. Four told the reader to run a build.sh that does not exist; the only harness builder is testing/scripts/build.sh. The BLE build prerequisites were described as optional on the strength of a probe that build.rs does not perform, and bluez was named a build prerequisite when libdbus-sys asks only for libdbus-1-dev and pkg-config and bluez is the runtime daemon. Link cost is the primary sort key in next-hop ranking, not reserved for future use; Ethernet runs on macOS as well as Linux; the BLE MTU is the L2CAP CoC MTU rather than a negotiated ATT_MTU; effective Ethernet MTU is 1497; the LAN discovery subsystem is src/mdns and eight citations still named a src/discovery that never existed here. The connectivity states in three tutorials were invented, and their jq filters matched nothing including healthy peers. One command filtered on a literal fd97: address prefix, which only the first byte of fixes, so it returned empty for all but one reader in 256 and every later step using the variable failed silently. transports.tor.advertise_on_nostr was undocumented despite being validated against node.rendezvous.nostr.enabled. The transport design document gains the BLE section it never had, written from the source: the backend cascade and its compile_error tripwire, the platform gate, the PSM advertisement wire layout and the byte budget that forces a 16-bit service-data key, and the probe and admission bounds. Three source files carried the same class of staleness and are corrected with the documentation: the OpenWrt ipk usage line and Makefile error text both named a packaging/openwrt that does not exist, and chaos.sh parsed --subnet without listing it. Folded in with the content commit, having been prepared alongside it: The three GitHub Action pins that had gone stale. Every third-party action is pinned to a commit SHA, nothing reports that a pin has aged, and re-resolving all ten against their tags found dorny/test-reporter@v2, taiki-e/install-action@v2 and vmactions/freebsd-vm@v1 had moved. The three install-action@nextest references stay unpinned, since that action reads the tool to install from the ref name. check-action-pins.sh passes at 75 references and all nine workflow files parse. The lockfile refresh, which is the mutating half of the dependency sweep. Thirty-six packages move to their latest semver-compatible versions and every one is transitive; nothing declared in Cargo.toml changes version. No advisory forces any of them. It was taken before the validation battery, because a gate run against a lockfile that later moves proves nothing about what ships. The sha2 0.10 to 0.11, hkdf 0.12 to 0.13 and bech32 0.11 to 0.12 majors, three of the four deferred at v0.4.0 for change surface rather than security. All three land with no source change. sha2 and hkdf must move together, since both depend on digest 0.11, and neither changes an algorithm. That matters because the chaining-key KDF in the Noise handshake is built on Hkdf::<Sha256>, where an output change would be a wire break rather than a compile error; no known-answer vectors exist for that path, so the wire-compatibility gate is what covers it. secp256k1 0.31 is deliberately absent, since nostr's own requirement would leave two copies of the ECC library in the tree. The README support matrix, rebuilt as one feature table broken out by Linux variety. A single Linux column hid that Debian, Ubuntu, Arch and NixOS are one glibc build differing in packaging, that OpenWrt is musl and drops BLE, and that Android is not a daemon platform. Transport rows sort by how many platforms carry them. A Native API row reads its platform set from the cfg gates. The installer row becomes a package format row naming the artifact, and only the .deb is exercised per release. Four changelog and release-note gaps the BLE re-walk found: a Bluetooth LE bullet stranded inside the released 0.4.2 section, a missing Fixed entry for the scan and probe loop counting a pool-refused connection as an established link, the unnamed embedder call that installs an application-owned radio, and the fact that stopping the transport now stops scanning as well as advertising. Three release-document gaps found walking the unsurveyed commits: the UDP reuse-flag fix stated in the direction opposite to the one it was made, with the silent second-daemon bind it prevents left unsaid; the corrected native-API socket paragraph carried into both release-note copies, which still named SOCK_SEQPACKET on FreeBSD and two kernels where three are handled; and the coordinate-cache hardening, which shipped with no text anywhere despite adding four operator-visible status fields. That last entry states plainly that the checks are mitigations and not a closure, since the coordinate is still not authenticated. Also folded in, the documentation pass that followed the content commit: A stage-pipeline diagram for the probe, embedded in the fipsctl reference under the five-stage list. It draws the five stages left to right with each stage's failure reasons below it, and the bypass that skips both lookup stages when the coordinates are cached or the target is a direct peer. Its branches come from the probe state machine rather than from the report, so the path stage is drawn as the one failure that does not stop the probe. A rewrite of the README's "What FIPS does" section. It now opens with what a machine running FIPS gets, rather than with the two deployment modes, and gives the self-organizing and permissionless property its own paragraph since it holds for both modes. A regrouping of the README's feature list into the mesh, getting traffic onto it, and running a node, with a bullet added for the native datagram API, which had none despite sitting in the support matrix. The Quick start now leads with the released packages rather than a source build. It also fixes a real defect: the package enables fips.service and fips-dns.service and starts neither on a fresh install, so .fips name resolution was silently dead until the next reboot and neither page said to start the service. A rewrite of the release notes. They opened with seven subsections of upgrade caveats and reached the first feature two hundred lines in; they now open with a summary of the release and elaborate below it in the same order. Android is stated as supported through an embedded crate rather than as a standalone daemon, consistently across all three documents. The OpenWrt pair is corrected: it is 802.11s between routers with FIPS supplying encryption, authentication and routing, plus a convention of an open !FIPS SSID a client joins over WiFi, not meshing over a router's own radios. The probe's path output is described as the least-common-ancestor walk, which is the worst-case fallback route rather than the route a packet takes. Detail that did not change what a reader does was cut from the notes and kept in the changelog.
301 lines
9.6 KiB
Markdown
301 lines
9.6 KiB
Markdown
# Set Up a Bluetooth (BLE) Peer Link
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FIPS supports Bluetooth Low Energy as a transport for short-range
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mesh extension — same room, same building, no IP infrastructure
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between the two endpoints. The BLE transport runs as L2CAP
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Connection-Oriented Channels on a configurable PSM and reports
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per-link MTU back to the mesh layer for path-MTU computation.
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For the design rationale and per-link MTU model, see
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[../design/fips-transport-layer.md](../design/fips-transport-layer.md).
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For all `transports.ble.*` configuration keys, see
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[../reference/configuration.md](../reference/configuration.md).
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> **Experimental.** The BLE transport works but is still maturing.
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> Expect rougher edges than UDP or TCP — particularly around link
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> stability under interference and MTU negotiation on older
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> controllers. Treat it as you would any experimental transport in a
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> production deployment.
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## When to use
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BLE is the right transport when:
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- Two nodes are within roughly 10 metres line-of-sight (more with
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external antennas, less through walls).
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- You want a self-contained mesh segment with no shared WiFi or
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Ethernet between the participants.
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- You can work within practical L2CAP CoC throughput (1-2 Mbps in
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good conditions, often substantially less under interference or
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at range) and the higher latency variance compared to WiFi.
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It is **not** the right transport for backbone links between rooms
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where WiFi or Ethernet exists, for high-throughput data, or for any
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deployment where range matters more than infrastructure-freedom.
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## Platform support
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The BLE transport is **Linux-only** in the current implementation.
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The runtime depends on BlueZ via the `bluer` crate, which in turn
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needs `glibc` (musl builds skip BLE; the build script gates the
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crate accordingly).
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| Platform | BLE transport |
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| -------- | -------------- |
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| Linux (glibc) | Supported. |
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| Linux (musl, OpenWrt) | Disabled at build time. |
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| macOS | Not supported. |
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| Windows | Not supported. |
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The Debian package `Recommends: bluez`; install it explicitly if you
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opted out:
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```sh
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sudo apt install bluez
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```
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## Prerequisites
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Both endpoints need:
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1. A BLE-capable HCI adapter visible to BlueZ. Confirm with:
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```sh
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sudo bluetoothctl show
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```
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Note the controller name (typically `hci0`).
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2. The `bluetoothd` service running and the adapter powered on:
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```sh
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sudo systemctl enable --now bluetooth
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sudo bluetoothctl power on
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```
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3. Sufficient privileges for the FIPS daemon. There are two
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independent privilege concerns; the BLE-only deployment case
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(mesh router with `tun.enabled: false`) needs only the second.
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- **TUN adapter (always required when `tun.enabled: true`).**
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The daemon needs `CAP_NET_ADMIN` to create and configure the
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TUN device. The shipped systemd unit handles this by running
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as root; if you prefer to drop privileges, see
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[run-as-unprivileged-user.md](run-as-unprivileged-user.md).
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- **BLE access (required for this how-to).** BlueZ exposes
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L2CAP and D-Bus paths under either group membership or
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`CAP_NET_RAW`. Pick one:
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- Run the daemon as root. The shipped systemd unit takes
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this route.
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- Run as an unprivileged user that is a member of the
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`bluetooth` group. No additional capability is needed for
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the BLE side.
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- Run as an unprivileged user with no group membership, and
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grant the binary `CAP_NET_RAW`:
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```sh
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sudo setcap cap_net_raw+ep $(which fips)
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```
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This bypasses BlueZ's polkit/group check by holding
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`CAP_NET_RAW` directly. If you also need `CAP_NET_ADMIN`
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for TUN, combine them:
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```sh
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sudo setcap cap_net_admin,cap_net_raw+ep $(which fips)
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```
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4. The same L2CAP PSM on both endpoints. The default is `0x0085`
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(133); override only if you need to coexist with another L2CAP
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service on that PSM.
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## Configuration
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Add a `ble` block under `transports` in `fips.yaml`. A minimum BLE-
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active node looks like this:
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```yaml
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transports:
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ble:
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adapter: "hci0"
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advertise: true
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scan: true
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auto_connect: true
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accept_connections: true
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```
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Note: `auto_connect: true` is intentionally non-default (the default
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is `false`). For a symmetric ground-up discovery flow where either
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side may dial, both ends must opt in explicitly.
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| Key | Purpose |
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| --- | ------- |
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| `adapter` | HCI controller name. Default: `hci0`. |
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| `psm` | L2CAP PSM. Default: `0x0085` (must match on both ends). |
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| `mtu` | Default L2CAP CoC MTU. Default: `2048`. The kernel may negotiate lower per link. |
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| `max_connections` | Concurrent BLE connections. Default: `7` (Bluetooth controllers typically support up to ~7 simultaneous L2CAP CoCs). |
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| `advertise` | Broadcast our BLE adverts so other FIPS nodes discover us. Default: `true`. |
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| `scan` | Listen for other FIPS nodes' BLE adverts. Default: `true`. |
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| `auto_connect` | Initiate a BLE connection to discovered FIPS adverts. Default: `false`. |
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| `accept_connections` | Accept inbound L2CAP connections. Default: `true`. |
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| `connect_timeout_ms` | Outbound L2CAP connect timeout. Default: `10000`. |
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| `probe_cooldown_secs` | After probing a BD_ADDR (success or failure), wait this long before probing it again. Default: `30`. |
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Two pairing patterns are common:
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**Symmetric auto-discovery.** Both nodes advertise, scan, and
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auto-connect. Whichever side completes the L2CAP connection first
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wins; the other side aborts its in-flight attempt. This is the
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"toss two devices in the same room" setup.
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```yaml
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# Both nodes
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transports:
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ble:
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adapter: "hci0"
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advertise: true
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scan: true
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auto_connect: true
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accept_connections: true
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```
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**Asymmetric peripheral / central.** One node only listens
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(peripheral), the other actively dials (central). Useful when one
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endpoint is a dedicated bootstrap and the other is mobile.
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```yaml
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# Listener
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transports:
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ble:
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adapter: "hci0"
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advertise: true
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scan: false
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auto_connect: false
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accept_connections: true
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```
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```yaml
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# Dialer
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transports:
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ble:
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adapter: "hci0"
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advertise: false
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scan: true
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auto_connect: true
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accept_connections: false
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```
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After editing, restart the daemon on each side:
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```sh
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sudo systemctl restart fips
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```
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## Verify
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On each endpoint, confirm the transport came up:
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```sh
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fipsctl show transports
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```
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Look for an entry of type `ble` in the `state: Running` (or
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equivalent) state. The `mtu` field reports the configured default;
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per-link MTU is reported separately.
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Confirm the link is established:
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```sh
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fipsctl show peers
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```
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The peer entry for the BLE-attached neighbour should report
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`transport_type: "ble"` and a non-zero `last_seen_ms`.
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BLE peering is auto-discovery only: there is no `fipsctl connect`
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path for BLE (the command accepts `udp`, `tcp`, `tor`, and
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`ethernet` only). Links come up via advert/scan; if you don't see
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the peer here, the configuration above is the only knob.
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To watch the link in real time, use `fipstop`'s **Peers** and
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**Transports** tabs:
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```sh
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fipstop
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```
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The Performance tab reports the per-link MMP metrics — SRTT, loss
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rate, ETX — which on BLE typically run an order of magnitude worse
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than over UDP, with much higher jitter.
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## Troubleshooting
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### Transport never comes up
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Check the BlueZ side first:
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```sh
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systemctl status bluetooth
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sudo bluetoothctl show
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```
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If `bluetoothctl show` reports `Powered: no`, fix that before
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debugging FIPS. The FIPS daemon will log a warning if it cannot
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acquire the adapter.
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If the FIPS log contains `bluer` D-Bus errors, the daemon usually
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lacks permission. Run as root, add the fips user to the
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`bluetooth` group, or grant the binary `CAP_NET_RAW`.
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### Peers see each other but never connect
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Verify `accept_connections` is true on at least one side and
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`auto_connect` is true on at least one side. Two listen-only nodes
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will discover each other but never establish an L2CAP connection.
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Check `psm` matches on both ends. A mismatch presents as adverts
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visible (in `fipstop` discovery counters) but every connect attempt
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fails.
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### Link comes up but throughput is poor
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Practical L2CAP CoC throughput in good conditions reaches
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1-2 Mbps, but interference, range, and controller capability all
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push it lower. FIPS carries BLE over an L2CAP connection-oriented
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channel rather than GATT, so there is no ATT_MTU to negotiate: the
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per-connection L2CAP CoC MTU applies, defaulting to 2048. The
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measured path MTU is the `path_mtu` field of `fipsctl show mmp`,
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under the session layer; `show peers` omits it and `show
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transports` carries only the transport-wide default.
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If MTU is unexpectedly low, both endpoints must support and have
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negotiated the BlueZ L2CAP `cocmode=2` extension. Older Bluetooth
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controllers cap MTU regardless.
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### Unstable links / repeated reconnects
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Bluetooth in busy 2.4 GHz environments suffers from WiFi
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interference. Switch the adapter to a less crowded channel (kernel
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side, not configurable from FIPS) or add an external antenna. The
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`probe_cooldown_secs` tunable backs off retry attempts; raise it if
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the daemon log shows many short-lived probes.
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### Permission errors on socket open
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Most modern systemd installs do not allow non-root processes to
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open raw L2CAP sockets without an explicit policy. Run the daemon
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as root (the shipped systemd unit does this) or add a `polkit`
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rule for the `bluetooth` group.
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## See also
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- [../design/fips-transport-layer.md](../design/fips-transport-layer.md)
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— per-transport MTU reporting and the BLE row of the supported-
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transports table.
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- [../reference/configuration.md](../reference/configuration.md) —
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full `transports.ble.*` reference.
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- [run-as-unprivileged-user.md](run-as-unprivileged-user.md) —
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adjacent privilege handling for the daemon process.
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