# FIPS v0.4.0 **Released**: 2026-06-27 v0.4.0 is the throughput-and-observability release on the v0.3.x wire format. It adds two new ways for nodes to find and reach each other (the Nym mixnet transport and opt-in mDNS LAN discovery), overhauls the data plane for higher single-node throughput and lower per-packet CPU, moves the entire operator read surface off the data-plane hot path so observability stays responsive under load, ships a reworked `fipstop` TUI, and hardens FMP and FSP rekey to be hitless under packet loss in both directions. It also folds in the accumulated mesh-convergence, admission-control, and packaging fixes from the maintenance line. v0.4.0 is wire-compatible with v0.3.0. Mixed meshes interoperate; there is no flag-day upgrade. A deployed v0.3.0 node and an upgraded v0.4.0 node peer, rekey, and route normally, so you can roll the upgrade out across a mesh in any order. ## At a glance - New outbound Nym mixnet transport with a single-container demo and a new mixnet-relay example. - Opt-in mDNS / DNS-SD discovery on the local link. - Data-plane overhaul: off-task encrypt and decrypt worker pools, GSO, connected-UDP send path, copy-avoidance on receive, batched macOS receive. - The full `show_*` read surface now serves off the receive loop, so `fipsctl` and `fipstop` stay responsive on loaded nodes; a new counter-only `show_metrics` query enables a Prometheus scraper at no hot-path cost. - Reworked `fipstop` TUI on a machine-verified render-snapshot base. - Rekey is now hitless under loss and reordering in both directions. - New packaging targets: an OpenWrt `.apk` for OpenWrt 25+ and a Nix flake for reproducible from-source builds on Nix/NixOS. - Six route-class transit counters partition forwarded traffic by its tree relationship to the next hop, visible via `show_routing` and `show_status`. ## What's new ### Nym mixnet transport FIPS can now peer over the [Nym](https://nymtech.net/) mixnet for metadata-resistant connectivity. The new `transports.nym` transport makes outbound connections through a `nym-socks5-client` SOCKS5 proxy that you run alongside the daemon (for example as a service running alongside the fips daemon, or as a sidecar container). The transport waits at startup for the nym-socks5-client to become ready before giving up. This is a privacy and anonymity deployment mode chosen for its own properties. It mixes your FIPS traffic into the Nym cover-traffic network so that link-level observers cannot correlate which mesh peers are talking. A new `examples/sidecar-nostr-mixnet-relay/` demonstrates a FIPS-reachable Nostr relay peered across the mixnet end to end, and a single-container demo ships with the transport. Enable it by adding a `transports.nym` instance and pointing it at your running nym-socks5-client. See the transports reference for the field set. ### mDNS LAN discovery Nodes on a shared local link can now find each other with zero address configuration. The opt-in `node.discovery.lan` path runs an mDNS / DNS-SD responder and browser: each node advertises a FIPS service record on the link and adopts the peers it discovers. This complements the existing Nostr-mediated overlay discovery for the common case where the peers are simply on the same LAN. Turn it on with `node.discovery.lan.enabled: true`. `service_type` and `scope` tune the advertised service record and which interfaces participate. Discovery on the local link needs no relay and no STUN. ### Data-plane throughput overhaul The receive and send paths were reworked for higher single-node throughput and lower per-packet CPU, building on the v0.3.0 crypto-backend swap: - **Off-task encrypt and decrypt.** Per-peer encrypt and decrypt now run on dedicated worker tasks rather than inline on the receive loop, so a single busy peer no longer serializes the whole node's crypto. - **GSO and connected-UDP send.** The Linux send path uses generic segmentation offload and a connected-UDP socket where available, cutting syscall overhead on bulk flows. - **Copy-avoidance on receive.** The receive hot path avoids buffer copies it previously made per packet. - **Batched macOS receive.** macOS gains a `recvmsg_x` batched receive, mirroring the Linux `recvmmsg` batching from v0.3.0. - **Shared immutable-state context and an atomic metric registry.** Immutable per-node state moved into a single shared context, and counters live in an atomic metric registry that the new `show_metrics` query reads without touching the hot path. These are all internal to the data plane and require no operator action. ### Observability off the hot path Every read-only control query now renders from a snapshot published once per tick into a lock-free `ArcSwap`, served from the control accept task instead of round-tripping the data-plane receive loop. This covers `show_status`, `show_stats_*`, `show_peers`, `show_sessions`, `show_links`, `show_connections`, `show_transports`, `show_mmp`, `show_tree`, `show_bloom`, `show_cache`, `show_routing`, `show_identity_cache`, `show_acl`, `show_listening_sockets`, and the new `show_metrics`. Only the mutating `connect` and `disconnect` commands still reach the loop. The practical effect: on a loaded node where the receive loop was busy, `fipsctl` and `fipstop` queries previously stalled or timed out (the five-second query pattern operators saw). They now answer promptly regardless of data-plane load. Per-entity snapshots reuse unchanged rows by pointer, so the per-tick publish cost stays bounded as peer and session counts grow. A new **`show_metrics`** query (surfaced as `fipsctl stats metrics`) returns a counter-only snapshot of every metric family. It is the enabler for a Prometheus scraper that pulls node counters at no hot-path cost. Six **route-class transit counters** partition transit-forwarded packets by their tree relationship to the chosen next hop — tree-up, tree-down, tree-down-cross, cross-link descend, cross-link ascend, and direct-peer — and the six classes sum to `forwarded_packets`. They surface through `show_routing` and `show_status`, and the `fipstop` routing tab is reorganized so its two columns separate own/endpoint traffic from forwarded/transit traffic with the tree-down-cross line visually flagged. ### Reworked fipstop TUI `fipstop` gets a rendering, navigation, and read-surface overhaul on a machine-verified base: a render-snapshot harness asserts the exact text grid and per-cell style of every view against canned control-socket output. New daemon-resolved fields surface through the snapshots, including effective persistence, root and is-root state, a per-transport-type peer-count map, per-peer effective depth, the root npub, and the last-sent uptree filter fill ratio with the subtree size estimate. A separate fix clears a garbled-screen problem on startup and stray bytes on quit, most visible over SSH and inside tmux: startup now forces a full repaint before the first draw, and quit stops and joins the stdin-poll thread before restoring the terminal, so post-raw-mode keystrokes no longer echo onto the restored screen. ### Rekey reliability FMP and FSP session rekey are now hitless under packet loss and reordering in both directions: - Inbound frames are authenticated against the pending session before the K-bit cutover promotes it, so a spoofed or stale frame cannot derail a rekey in progress. - Rekey message-1 retransmission is bounded, and the link-dead heartbeat is rekey-aware so an in-flight rekey is not mistaken for a dead link. - FSP session rekey holds connectivity across the rekey window under loss and reordering. - Dual-initiation races (both peers starting a rekey at once on a high-latency link) are desynchronized with symmetric jitter so the two sides converge on one session rather than fighting. - An exhausted retransmission-budget abort, an expected and self-limiting outcome on lossy or high-latency links, is logged at debug rather than warn. The net operator takeaway: rekey completes cleanly without dropping traffic, even on lossy or high-latency links, and the log no longer cries wolf when a rekey gives up and retries. ### New packaging targets - **OpenWrt `.apk`.** A new `.apk` package targets OpenWrt 25+, where apk-tools is the mandatory package manager; the existing `.ipk` continues to cover OpenWrt 24.x and earlier. It is built SDK-free, reusing the `.ipk` cross-compile and installed-filesystem payload, and releases publish `.apk` artifacts and checksums alongside `.ipk`. Like the `.ipk`, the package is unsigned and installed with `apk add --allow-untrusted`. - **Nix flake.** A `flake.nix` at the project root builds all four binaries (`fips`, `fipsctl`, `fips-gateway`, `fipstop`) from source on Nix/NixOS, pinning the exact toolchain and wiring the native build dependencies so no host setup is needed beyond Nix with flakes enabled. It exposes `nix build`, `nix run`, a `nix develop` dev shell, and `nix flake check`, with `flake.lock` committed for reproducibility. ## Behavior changes worth flagging These affect operators on upgrade. - **Bloom filter antipoison cap raised.** `node.bloom.max_inbound_fpr` moves from 0.05 to 0.10, accepting filters with a higher derived false-positive rate before rejecting them. This reduces spurious filter rejections on larger meshes while keeping the antipoison protection in place. - **TCP inbound cap honors `max_connections`.** The TCP inbound accept ceiling now resolves from explicit per-transport `max_inbound_connections`, then node-wide `node.limits.max_connections`, then the built-in default of 256. Previously the TCP inbound ceiling was hardwired to 256 and ignored `max_connections`, so raising it had no effect on inbound TCP. - **Static host aliases hot-reload.** `/etc/fips/hosts` now reloads on mtime change once per tick rather than only at startup, so display names in `fipsctl` and `fipstop` reflect edits without a daemon restart. The peer ACL reloads through the same lock-free snapshot mechanism. - **Quieter logs on busy public-mesh nodes.** Routine per-peer connection-lifecycle and capacity-cap events, no-route session-datagram drops, and exhausted rekey-budget aborts are demoted to debug, so genuinely notable info and warn lines are no longer drowned out. - **More visible drops.** Receive-path silent rejections now flow through typed reject-reason counters, and discovery counts requests dropped when the dedup cache is full (`req_dedup_cache_full`, visible via `show_routing`). Drops that were previously silent are now countable. - **Tor connect-refused accounting.** The Tor transport increments its `connect_refused` statistic (the "Refused" line in `fipstop`) on an actively-refused SOCKS5 connect, instead of recording every connect failure as a generic SOCKS5 error. ## Notable bug fixes The CHANGELOG has the exhaustive list. This is the operator-relevant subset of fixes for behavior that shipped in v0.3.0. - **Symmetric peer teardown on manual disconnect.** A manual `fipsctl disconnect` now sends the peer a scoped Disconnect so both ends tear down and re-handshake cleanly. Previously a manual disconnect tore down only the local side, leaving the peer with a stale session that was never re-adopted as a child and whose bloom filter was never re-recorded. - **Gateway holds long-lived and DNS-cached mappings.** `fips-gateway` no longer drops a virtual-IP mapping while traffic is still flowing. The mapping TTL clock previously advanced only on DNS re-query, so a busy long-lived or DNS-cached client could have its mapping reclaimed mid-flow. The tick now refreshes the mapping whenever conntrack reports active sessions and recovers a draining mapping to active when traffic resumes; only genuinely idle mappings drain. - **Accurate mesh-size estimate under filter overlap.** The mesh-size estimator now estimates the cardinality of the OR-union of self plus every connected peer's inbound filter, instead of summing per-filter cardinalities of tree peers. Summing assumed the filters were disjoint, so a stale or oversized parent filter or a routing loop inflated the reported mesh size and a tree rebalance flapped the count. OR-union deduplicates overlap, equals the old result in the disjoint case, and removes the estimate's dependence on tree-declaration cache freshness. - **Single-uplink node reattaches within a round-trip.** A node with one tree peer, which has periodic parent re-evaluation disabled, was left self-rooted and unreachable if its one-shot attaching TreeAnnounce was lost, until the next periodic re-broadcast. Tree-position exchange is now self-healing on the receive path: a node that hears an announce advertising a strictly worse root echoes its own declaration back, provoking the better-rooted peer to re-push its real position immediately. - **macOS self-connections work end to end (#117).** Traffic a macOS node sends to its own `.fips` address is now delivered locally for full TCP/UDP, not just `ping6`. The point-to-point `utun` egresses self-addressed packets into the daemon with an unfinished transport checksum (macOS offloads it on the `lo0` loopback route), so re-injecting them verbatim made the local stack drop every segment the MSS-clamp rewrite did not happen to fix and self-connections half-opened and hung. The hairpin path now recomputes the TCP/UDP checksum before re-injection. Linux was unaffected. ## Upgrade notes Operator-actionable items moving from v0.3.0 to v0.4.0: - **Wire-compatible, no flag day.** v0.4.0 peers with v0.3.0. Upgrade nodes in any order. During a rolling upgrade you may see some log lines on the upgraded side as it interacts with not-yet-upgraded peers; behavior is correct, log noise only. - **Bloom antipoison cap default changed.** `node.bloom.max_inbound_fpr` now defaults to 0.10 (was 0.05). If you set this explicitly, review whether you still want the old value. - **New optional config surfaces.** `transports.nym` (outbound Nym mixnet) and `node.discovery.lan` (mDNS LAN discovery) are both opt-in and off by default. Adding them is the only way to turn the new paths on. - **TCP inbound cap.** If you relied on the old hardwired 256 inbound-TCP ceiling, note it now honors `max_inbound_connections` then `node.limits.max_connections` then 256. - **New observability query.** `fipsctl stats metrics` (the `show_metrics` control query) returns a counter-only snapshot suitable for a scraper. ## Getting v0.4.0 - **Linux x86_64 / aarch64**: `.deb` and tarball at the [v0.4.0 release page](https://github.com/jmcorgan/fips/releases/tag/v0.4.0). - **Arch Linux**: `fips` from the AUR. - **macOS**: `.pkg` at the v0.4.0 release page. - **Windows**: ZIP at the v0.4.0 release page. - **OpenWrt**: `.ipk` (OpenWrt 24.x and earlier) or `.apk` (OpenWrt 25+) at the v0.4.0 release page. - **From source**: `cargo build --release` from a checkout of the v0.4.0 tag (Rust 1.94.1 per `rust-toolchain.toml`; `libclang-dev` is a required Linux build prerequisite). - **Nix / NixOS**: `nix build .#fips` from a checkout of the v0.4.0 tag builds the binaries from source with the pinned toolchain and no manual prerequisites (see the Nix section of `packaging/README.md`). The full per-commit changelog lives in [`CHANGELOG.md`](../../CHANGELOG.md). Issues and discussion at [github.com/jmcorgan/fips](https://github.com/jmcorgan/fips). ## Contributors Thanks to everyone who contributed code, packaging work, bug reports, or reviews to this release. - [@jcorgan](https://github.com/jmcorgan): release shepherd, high-level design, control read plane, rekey hardening, admission, bug fixes, testing, packaging, PR coordination, and issue resolution. - [@mmalmi](https://github.com/mmalmi): opt-in mDNS LAN discovery and data-plane performance work. - [@Origami74](https://github.com/Origami74): macOS packaging and website coordination. - [@dskvr](https://github.com/dskvr): AUR packaging. - [@oleksky](https://github.com/oleksky): Nym mixnet transport and the single-container mixnet demo.