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fips/docs/reference/configuration.md
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FIPS Configuration

FIPS uses YAML-based configuration with a cascading multi-file priority system. All parameters have sensible defaults; a node can run with no configuration file at all (it will generate an ephemeral identity and listen on default addresses).

Configuration Loading

Search Paths

When started without the -c flag, FIPS searches for fips.yaml in these locations, lowest to highest priority:

Priority Path Purpose
1 (lowest) /etc/fips/fips.yaml System-wide defaults
2 ~/.config/fips/fips.yaml User preferences
3 ~/.fips.yaml Legacy user config
4 (highest) ./fips.yaml Deployment-specific overrides

All found files are loaded and merged in priority order. Values from higher priority files override those from lower priority files. This allows a system administrator to set site-wide defaults in /etc/fips/fips.yaml while individual deployments override specific values in ./fips.yaml.

CLI Option

fips -c /path/to/config.yaml

When -c is specified, only that file is loaded (search paths are skipped).

Partial Configuration

Every field has a built-in default. A configuration file only needs to specify values that differ from defaults. For example, a minimal config might contain only the identity and peer list, inheriting all other defaults.

YAML Structure

The configuration is organized into five top-level sections:

node:        # Node behavior, protocol parameters, and tuning
tun:         # TUN virtual interface
dns:         # DNS responder for .fips domain
transports:  # Network transports (UDP, Ethernet, Bluetooth, Tor, ...)
peers:       # Static peer list

Control Socket (node.control.*)

Parameter Type Default Description
node.control.enabled bool true Enable the control socket
node.control.socket_path string (auto) Linux: Socket file path. Resolved at daemon startup: $XDG_RUNTIME_DIR/fips/control.sock if XDG_RUNTIME_DIR is set, else /run/fips/control.sock if /run/fips can be created (typical when running under the shipped systemd unit), else /tmp/fips-control.sock. (Note: the fipsctl / fipstop clients use a different fallback order — /run/fips first if it already exists, then XDG_RUNTIME_DIR, then /tmp — so when both schemes apply, set this field explicitly to avoid mismatch.) Windows: TCP port number (default: 21210); the control socket listens on 127.0.0.1 at this port.

The control socket provides access to node state and runtime management via the fipsctl command-line tool. In addition to read-only status queries, fipsctl connect and fipsctl disconnect enable runtime peer management. See the fipsctl reference for the command list.

On Linux, the control socket is a Unix domain socket with filesystem permissions (mode 0770, group fips). On Windows, it is a TCP listener on localhost. TCP does not provide filesystem-level ACLs, so any local user can connect to the control port.

Security note (Windows): The TCP control socket on Windows is a known limitation. Any process running on the local machine can connect to the control port and issue commands, including disconnect, connect, and inject-config. This is acceptable for single-user workstations but may be inappropriate for shared machines. Future improvements may include named pipe support (with Windows ACLs) or an authentication token mechanism. On shared Windows systems, consider using firewall rules to restrict access to the control port.

All tunable protocol parameters live under node.*, organized as sysctl-style dotted paths. The top-level sections (tun, dns, transports, peers) handle infrastructure concerns only.

Node Parameters (node.*)

Identity (node.identity.*)

Parameter Type Default Description
node.identity.nsec string (none) Secret key in nsec (bech32) or hex format. If omitted, behavior depends on persistent.
node.identity.persistent bool false Persist identity across restarts via key file.

Identity resolution follows a three-tier priority:

  1. Explicit nsec in config — always used when present, regardless of persistent
  2. Persistent key file — when persistent: true and no nsec, loads from fips.key adjacent to the config file; if no key file exists, generates a new keypair and saves it
  3. Ephemeral — when persistent: false (default) and no nsec, generates a fresh keypair on each start

Key files (fips.key with mode 0600, fips.pub with mode 0644) are written adjacent to the highest-priority config file for operator visibility, even in ephemeral mode.

General

Parameter Type Default Description
node.leaf_only bool false Leaf-only mode: node does not forward traffic or participate in routing
node.tick_interval_secs u64 1 Periodic maintenance tick interval (retry checks, timeout cleanup, tree refresh)
node.base_rtt_ms u64 100 Initial RTT estimate for new links before measurements converge
node.heartbeat_interval_secs u64 10 Heartbeat send interval per peer for liveness detection
node.link_dead_timeout_secs u64 30 No-traffic timeout before a peer is declared dead and removed
node.log_level string "info" Tracing filter default. Case-insensitive; one of trace, debug, info, warn, error. Overridden by the RUST_LOG environment variable when set

Resource Limits (node.limits.*)

Controls capacity for connections, peers, and links.

Parameter Type Default Description
node.limits.max_connections usize 256 Max handshake-phase connections
node.limits.max_peers usize 128 Max authenticated peers
node.limits.max_links usize 256 Max active links
node.limits.max_pending_inbound usize 1000 Max pending inbound handshakes

Rate Limiting (node.rate_limit.*)

Handshake rate limiting protects against DoS on the Noise IK handshake path.

Parameter Type Default Description
node.rate_limit.handshake_burst u32 100 Token bucket burst capacity
node.rate_limit.handshake_rate f64 10.0 Tokens per second refill rate
node.rate_limit.handshake_timeout_secs u64 30 Stale handshake cleanup timeout
node.rate_limit.handshake_resend_interval_ms u64 1000 Initial handshake message resend interval
node.rate_limit.handshake_resend_backoff f64 2.0 Resend backoff multiplier (1s, 2s, 4s, 8s, 16s with defaults)
node.rate_limit.handshake_max_resends u32 5 Max resends per handshake attempt

Retry / Backoff (node.retry.*)

Connection retry with exponential backoff.

Parameter Type Default Description
node.retry.max_retries u32 5 Max connection retry attempts
node.retry.base_interval_secs u64 5 Base backoff interval
node.retry.max_backoff_secs u64 300 Cap on exponential backoff (5 minutes)

Auto-reconnect (triggered by MMP link-dead removal) uses the same backoff parameters but bypasses max_retries, retrying indefinitely. See peers[].auto_reconnect below.

Cache Parameters (node.cache.*)

Controls caching of tree coordinates and identity mappings.

Parameter Type Default Description
node.cache.coord_size usize 50000 Max entries in coordinate cache
node.cache.coord_ttl_secs u64 300 Coordinate cache entry TTL (5 minutes)
node.cache.identity_size usize 10000 Max entries in identity cache (LRU, no TTL)

Discovery Protocol (node.discovery.*)

Controls bloom-guided node discovery (LookupRequest/LookupResponse).

Parameter Type Default Description
node.discovery.ttl u8 64 Hop limit for LookupRequest forwarding
node.discovery.attempt_timeouts_secs array<u64> [1, 2, 4, 8] Per-attempt timeouts. Each entry is the deadline for one LookupRequest before sending the next attempt with a fresh request_id. Length determines total attempt count; default gives 4 attempts and a 15s total budget
node.discovery.recent_expiry_secs u64 10 Dedup cache expiry for recent request IDs
node.discovery.backoff_base_secs u64 0 Optional post-failure suppression base in seconds; doubles per consecutive failure. 0 disables (default) — the per-attempt sequence is the only retry pacing
node.discovery.backoff_max_secs u64 0 Cap on optional post-failure backoff
node.discovery.forward_min_interval_secs u64 2 Transit-side rate limiting: minimum interval between forwarded lookups for the same target

Nostr Overlay Discovery (node.discovery.nostr.*)

Optional Nostr-mediated overlay discovery. This layer publishes replaceable endpoint adverts (fips-overlay-v1), consumes advert-derived endpoint fallbacks for configured peers, and can optionally discover non-configured peers (policy: open). udp:nat remains the trigger for NAT traversal offer/answer + punch-through, after which the established UDP socket is handed into the normal FIPS transport/session stack. Inbox-relay discovery falls back to the local DM relay list if remote relay metadata cannot be fetched. The Nostr discovery runtime is compiled into every build of the crate; it is enabled at runtime via node.discovery.nostr.enabled: true and stays inert otherwise.

Parameter Type Default Description
node.discovery.nostr.enabled bool false Enable Nostr-mediated overlay discovery
node.discovery.nostr.policy string "configured_only" Advert discovery policy: disabled, configured_only, open
node.discovery.nostr.open_discovery_max_pending usize 64 Max open-discovery peers queued in outbound retry/connection state at once
node.discovery.nostr.max_concurrent_incoming_offers usize 16 Max concurrent inbound traversal offers processed at once (rate limit against offer spam)
node.discovery.nostr.advert_cache_max_entries usize 2048 Max cached overlay adverts retained from relay traffic
node.discovery.nostr.seen_sessions_max_entries usize 2048 Max seen-session IDs retained for replay detection
node.discovery.nostr.advertise bool true Publish local endpoint adverts
node.discovery.nostr.advert_relays list[string] ["wss://relay.damus.io", "wss://nos.lol", "wss://offchain.pub"] Relays used for service adverts
node.discovery.nostr.dm_relays list[string] ["wss://relay.damus.io", "wss://nos.lol", "wss://offchain.pub"] Relays used for encrypted signaling events
node.discovery.nostr.stun_servers list[string] ["stun:stun.l.google.com:19302", "stun:stun.cloudflare.com:3478", "stun:global.stun.twilio.com:3478"] STUN servers used for local reflexive address discovery
node.discovery.nostr.share_local_candidates bool false Whether to advertise local (RFC 1918 / ULA) interface addresses as host candidates in the traversal offer. Off by default: in most deployments peers aren't on the same broadcast domain, and sharing private host candidates causes misleading punch successes when an asymmetric L3 path (VPN, Tailscale subnet route, overlapping address space) makes a peer's private IP one-way reachable. Enable only when peers are on the same physical LAN
node.discovery.nostr.app string "fips-overlay-v1" Traversal application namespace, published in the advert's protocol tag (the d tag itself is hardcoded to fips-overlay-v1)
node.discovery.nostr.signal_ttl_secs u64 120 Signaling TTL in seconds
node.discovery.nostr.attempt_timeout_secs u64 10 Overall traversal attempt timeout in seconds
node.discovery.nostr.replay_window_secs u64 300 Replay tracking retention window in seconds
node.discovery.nostr.punch_start_delay_ms u64 2000 Delay before punch traffic starts
node.discovery.nostr.punch_interval_ms u64 200 Interval between punch packets
node.discovery.nostr.punch_duration_ms u64 10000 How long to keep punching before failure
node.discovery.nostr.advert_ttl_secs u64 3600 Advert TTL in seconds
node.discovery.nostr.advert_refresh_secs u64 1800 How often adverts are refreshed in seconds
node.discovery.nostr.startup_sweep_delay_secs u64 5 Settle delay after Nostr discovery starts before the one-shot startup advert sweep runs (only used under policy: open). Allows the relay subscription backlog to populate the in-memory advert cache before the sweep fires
node.discovery.nostr.startup_sweep_max_age_secs u64 3600 Maximum advert age (now - created_at) considered by the one-shot startup sweep (only used under policy: open). Adverts older than this are skipped on startup; the per-tick sweep still considers them up to valid_until_ms
node.discovery.nostr.failure_streak_threshold u32 5 Consecutive NAT-traversal failures against a peer before an extended cooldown is applied. At this threshold the daemon also actively re-fetches the peer's advert from advert_relays to evict cache entries for peers that have gone away
node.discovery.nostr.extended_cooldown_secs u64 1800 Cooldown applied to a peer once failure_streak_threshold is hit. Suppresses both open-discovery sweep enqueues and per-attempt retry firings until elapsed (30 minutes default)
node.discovery.nostr.warn_log_interval_secs u64 300 Minimum interval between NAT traversal failed WARN log lines for the same peer. Subsequent failures inside the window log at DEBUG to reduce log spam on public-test nodes with many cache-learned peers
node.discovery.nostr.failure_state_max_entries usize 4096 Maximum entries retained in the per-npub failure-state map. Bounds memory under high cache turnover; oldest entries (by last failure time) are evicted when the cap is exceeded
node.discovery.nostr.protocol_mismatch_cooldown_secs u64 86400 Cooldown applied after observing a fatal protocol mismatch on a Nostr-adopted bootstrap transport (e.g. Unknown FMP version from a peer running a different FMP-protocol version). Independent of extended_cooldown_secs and much longer (24 hours default) because the mismatch is structural — re-traversing is wasted effort until one side upgrades

If stun_servers is omitted, the built-in default list above is used. If it is specified in YAML, the configured list fully overrides the defaults. Initiators use only this local list for outbound STUN queries; peer-advertised STUN values are published for diagnostics/interoperability but are not used as arbitrary egress targets. The built-in advert and DM relay defaults point at widely-operated public relays (Damus, nos.lol, Primal) as best-effort endpoints; operators are encouraged to override them with their own relay preferences for production deployments. Advert freshness is enforced semantically: events with expired NIP-40 expiration tags are dropped, and adverts are also bounded by a created-at staleness window derived from advert_ttl_secs (with a grace multiplier). The current in-tree STUN parser handles IPv4 and IPv6 mapped-address attributes. Local traversal candidates include active non-loopback private interface addresses (RFC1918 IPv4 and IPv6 ULA) plus probed local egress addresses for the punch socket port. During punching, compatible private-subnet candidates and reflexive candidates are attempted in parallel; the first successful path wins.

LAN Discovery (node.discovery.lan.*)

Peer discovery on the local link via mDNS / DNS-SD (RFC 6762 / RFC 6763). When enabled, the node publishes a _fips._udp.local. service advert carrying its npub (and optional scope) and concurrently browses for the same service type to learn same-broadcast-domain peers. The result is sub-second peer pairing with no Nostr-relay roundtrip, STUN observation, or NAT traversal: the observed endpoint is by construction routable from the consumer's LAN.

mDNS adverts are unauthenticated, so a LAN advert is treated only as a routing hint. Identity is still proven end-to-end by the Noise XX handshake the node initiates against the observed endpoint; a spoofed advert carrying another peer's npub fails the handshake and is dropped. LAN discovery requires an active UDP transport (peers dial the advertised UDP port to begin the handshake).

Parameter Type Default Description
node.discovery.lan.enabled bool false Master switch. Opt-in: enable for sub-second same-LAN pairing. Default-off avoids reintroducing a per-LAN identity broadcast on nodes that have deliberately disabled other discovery channels
node.discovery.lan.service_type string "_fips._udp.local." DNS-SD service type. Primarily an override for integration tests running multiple isolated services on one loopback interface; leave at the default in production
node.discovery.lan.scope string (none) Optional application/network scope carried in a scope=<name> TXT entry. Browsers with a scope set only surface peers advertising the same scope, so nodes on the same physical LAN configured for different mesh networks do not cross-feed. Intentionally separate from node.discovery.nostr.app so relay-visible adverts can stay generic while LAN discovery is isolated per private network

Spanning Tree (node.tree.*)

Controls tree construction and parent selection.

Parameter Type Default Description
node.tree.announce_min_interval_ms u64 500 Per-peer TreeAnnounce rate limit
node.tree.parent_hysteresis f64 0.2 Cost improvement fraction required for same-root parent switch (0.01.0)
node.tree.hold_down_secs u64 30 Suppress non-mandatory re-evaluation after parent switch
node.tree.reeval_interval_secs u64 60 Periodic cost-based parent re-evaluation interval (0 = disabled)
node.tree.flap_threshold u32 4 Parent switches in window before dampening engages
node.tree.flap_window_secs u64 60 Sliding window for counting parent switches
node.tree.flap_dampening_secs u64 120 Extended hold-down duration when flap threshold exceeded

Bloom Filter (node.bloom.*)

Parameter Type Default Description
node.bloom.update_debounce_ms u64 500 Debounce interval for filter update propagation
node.bloom.max_inbound_fpr f64 0.20 Antipoison cap: reject inbound FilterAnnounce frames whose advertised false-positive rate exceeds this value. Valid range (0.0, 1.0). The default 0.20 corresponds to fill 0.7248 at k=5 (≈2,114 entries on the 1 KB filter); a saturated/poisoned filter is still ~100% FPR and rejected

Bloom filter size (1 KB), hash count (5), and size classes are protocol constants and not configurable.

ECN Signaling (node.ecn.*)

Controls hop-by-hop ECN (Explicit Congestion Notification) signaling. When enabled, transit nodes detect congestion on outgoing links (via MMP loss/ETX metrics or kernel buffer drops) and set the CE flag on forwarded FMP frames. Destination nodes mark ECN-capable IPv6 packets with CE before TUN delivery per RFC 3168, enabling end-host TCP congestion control to react.

Parameter Type Default Description
node.ecn.enabled bool true Enable ECN congestion signaling (CE flag relay and local congestion detection)
node.ecn.loss_threshold f64 0.05 MMP loss rate threshold for CE marking (0.01.0). When the outgoing link's loss rate meets or exceeds this value, forwarded packets are CE-marked.
node.ecn.etx_threshold f64 3.0 MMP ETX threshold for CE marking (≥1.0). When the outgoing link's ETX meets or exceeds this value, forwarded packets are CE-marked.

Congestion detection triggers on any of: outgoing link loss ≥ loss_threshold, outgoing link ETX ≥ etx_threshold, or kernel receive buffer drops detected on any local transport. CE is relayed hop-by-hop: once set on any hop, the flag stays set for all subsequent hops to the destination.

Rekey (node.rekey.*)

Controls periodic Noise rekey for forward secrecy. When enabled, both FMP (link-layer IK) and FSP (session-layer XK) sessions perform fresh Diffie-Hellman key exchanges after a time or message count threshold, whichever comes first. A 10-second drain window keeps the old session active for decryption during cutover.

Parameter Type Default Description
node.rekey.enabled bool true Enable periodic Noise rekey on all links and sessions
node.rekey.after_secs u64 120 Initiate rekey after this many seconds on a session
node.rekey.after_messages u64 65536 Initiate rekey after this many messages sent on a session

Session / Data Plane (node.session.*)

Controls end-to-end session behavior and packet queuing.

Parameter Type Default Description
node.session.default_ttl u8 64 Default SessionDatagram TTL
node.session.pending_packets_per_dest usize 16 Queue depth per destination during session establishment
node.session.pending_max_destinations usize 256 Max destinations with pending packets
node.session.idle_timeout_secs u64 90 Idle session timeout; established sessions with no application data for this duration are removed. MMP reports (SenderReport, ReceiverReport, PathMtuNotification) do not count as activity
node.session.coords_warmup_packets u8 5 Number of initial data packets per session that include the CP flag for transit cache warmup; also the reset count on CoordsRequired/PathBroken receipt
node.session.coords_response_interval_ms u64 2000 Minimum interval (ms) between standalone CoordsWarmup responses to CoordsRequired/PathBroken signals per destination

The anti-replay window size (2048 packets) is a compile-time constant and not configurable.

Metrics Measurement Protocol for per-peer link measurement. See ../design/fips-mesh-layer.md for behavioral details.

Parameter Type Default Description
node.mmp.mode string "full" Operating mode: full (sender + receiver reports), lightweight (receiver reports only), or minimal (spin bit + CE echo only, no reports)
node.mmp.log_interval_secs u64 30 Periodic operator log interval for link metrics
node.mmp.owd_window_size usize 32 One-way delay trend ring buffer size

Session-Layer MMP (node.session_mmp.*)

Metrics Measurement Protocol for end-to-end session measurement. Configured independently from link-layer MMP because session reports are routed through every transit link, consuming bandwidth proportional to path length.

Parameter Type Default Description
node.session_mmp.mode string "full" Operating mode: full, lightweight, or minimal
node.session_mmp.log_interval_secs u64 30 Periodic operator log interval for session metrics
node.session_mmp.owd_window_size usize 32 One-way delay trend ring buffer size

Internal Buffers (node.buffers.*)

Channel sizes affecting throughput and memory. Primarily useful for performance tuning under high load or on memory-constrained devices.

Parameter Type Default Description
node.buffers.packet_channel usize 1024 Transport to Node packet channel capacity
node.buffers.tun_channel usize 1024 TUN to Node outbound channel capacity
node.buffers.dns_channel usize 64 DNS to Node identity channel capacity

TUN Interface (tun.*)

Parameter Type Default Description
tun.enabled bool false Enable TUN virtual interface
tun.name string "fips0" Interface name
tun.mtu u16 1280 Interface MTU (IPv6 minimum)

DNS Responder (dns.*)

Resolves <npub>.fips queries to FIPS IPv6 addresses. Resolution is pure computation (npub to public key to address); resolved identities are registered with the node for routing.

Parameter Type Default Description
dns.enabled bool true Enable DNS responder
dns.bind_addr string "::1" Bind address. Default is IPv6 loopback only; the shipped fips-dns-setup configures systemd-resolved to forward .fips queries to [::1]:5354. To expose the responder to mesh peers (or to the gateway over IPv4), override (e.g., "::" for all interfaces).
dns.port u16 5354 Listen port
dns.ttl u32 300 AAAA record TTL in seconds

The dns.ttl value should not exceed node.cache.coord_ttl_secs to avoid stale address mappings.

Host Mapping

The DNS resolver checks a host map before falling back to direct npub resolution, enabling names like gateway.fips instead of npub1...fips. The host map is populated from two sources:

  1. Peer aliases — the alias field on configured peers in peers:.
  2. Hosts file/etc/fips/hosts, one hostname npub1... per line. Blank lines and # comments are allowed.

On conflict, hosts-file entries take precedence over peer aliases. The hosts file is auto-reloaded on modification (mtime change) without restarting the daemon. Hostnames are case-insensitive.

The installer ships /etc/fips/hosts pre-populated with the public test mesh roster (test-us01test-uk01). Operator-style guide for adding entries and the precedence rules: ../how-to/host-aliases.md.

Transports (transports.*)

UDP (transports.udp.*)

Parameter Type Default Description
transports.udp.bind_addr string "0.0.0.0:2121" UDP bind address and port. Ignored when outbound_only: true (kernel-assigned ephemeral port is used regardless).
transports.udp.mtu u16 1280 Transport MTU
transports.udp.recv_buf_size usize 2097152 UDP socket receive buffer size in bytes (2 MB). Linux kernel doubles the requested value internally. Host net.core.rmem_max must be >= this value.
transports.udp.send_buf_size usize 2097152 UDP socket send buffer size in bytes (2 MB). Host net.core.wmem_max must be >= this value.
transports.udp.advertise_on_nostr bool false Include this UDP transport in Nostr endpoint adverts. Implicitly forced false when outbound_only: true.
transports.udp.public bool false If advertised: true publishes direct host:port; false publishes udp:nat rendezvous
transports.udp.external_addr string (none) Explicit advertise-as override. Bare IP ("203.0.113.45" — bind port is appended) or full host:port. Takes precedence over the bound address and STUN autodiscovery. Useful when the public IP isn't on a local interface (cloud 1:1 NAT, EIP) or to skip STUN for a deterministic value.
transports.udp.outbound_only bool false Pure-client posture. When true, the transport binds to 0.0.0.0:0 (kernel-assigned ephemeral port) regardless of bind_addr, refuses inbound handshake msg1, and is never advertised on Nostr regardless of advertise_on_nostr.
transports.udp.accept_connections bool true Accept inbound handshake msg1 from new peers. Combine with outbound_only: false and accept_connections: false (plus auto_connect on peer entries) for a node that initiates outbound links but rejects fresh inbound handshakes. The handshake handler carves out msg1 from peers already established on this transport so rekey continues to work.

Ethernet (transports.ethernet.*)

Ethernet transport sends raw frames via AF_PACKET SOCK_DGRAM sockets. Requires CAP_NET_RAW or running as root. Linux only.

Parameter Type Default Description
interface string (required) Network interface name (e.g., "eth0", "enp3s0")
ethertype u16 0x2121 EtherType
mtu u16 (auto) Override MTU. Default: interface MTU minus 3 (for frame type + length prefix)
recv_buf_size usize 2097152 Socket receive buffer size in bytes (2 MB)
send_buf_size usize 2097152 Socket send buffer size in bytes (2 MB)
listen bool true Listen for neighbor beacons from other nodes
announce bool false Broadcast announcement beacons on the LAN
auto_connect bool false Auto-connect to discovered peers
accept_connections bool false Accept incoming connection attempts from discovered peers
beacon_interval_secs u64 30 Announcement beacon interval in seconds (minimum 10)

Named instances. Multiple Ethernet interfaces can be configured by using named sub-keys instead of flat parameters:

transports:
  ethernet:
    lan:
      interface: "eth0"
      listen: true
      announce: true
    backbone:
      interface: "eth1"
      announce: false

Each named instance operates independently with its own socket and neighbor state. The instance name is used in log messages and the name() method on the Transport trait.

TCP (transports.tcp.*)

TCP transport enables firewall traversal on networks that block UDP but allow TCP (e.g., port 443). Uses FMP header-based framing with zero overhead.

Parameter Type Default Description
transports.tcp.bind_addr string (none) Listen address (e.g., "0.0.0.0:8443"). If omitted, outbound-only mode.
transports.tcp.mtu u16 1400 Default MTU. Per-connection MTU derived from TCP_MAXSEG when available.
transports.tcp.connect_timeout_ms u64 5000 Outbound connect timeout in milliseconds
transports.tcp.nodelay bool true TCP_NODELAY (disable Nagle for low latency)
transports.tcp.keepalive_secs u64 30 TCP keepalive interval in seconds (0 = disabled)
transports.tcp.recv_buf_size usize 2097152 Socket receive buffer size in bytes (2 MB)
transports.tcp.send_buf_size usize 2097152 Socket send buffer size in bytes (2 MB)
transports.tcp.max_inbound_connections usize 256 Maximum simultaneous inbound connections
transports.tcp.advertise_on_nostr bool false Include this TCP transport in Nostr endpoint adverts
transports.tcp.external_addr string (none) Explicit advertise-as override. Bare IP or full host:port. Required when bind_addr is wildcard (e.g. "0.0.0.0:443") and advertise_on_nostr: true, since TCP has no STUN equivalent for autodiscovery. Common on cloud 1:1 NAT / EIP setups where the public IP isn't bindable on the host.

Named instances. Like other transports, multiple TCP instances can be configured with named sub-keys:

transports:
  tcp:
    public:
      bind_addr: "0.0.0.0:443"
    internal:
      bind_addr: "10.0.0.1:8443"
      max_inbound_connections: 64

Tor (transports.tor.*)

Tor transport routes FIPS traffic through the Tor network for anonymity. Requires an external Tor daemon providing a SOCKS5 proxy. Three modes: socks5 for outbound-only, control_port for outbound + monitoring, directory for outbound + inbound via Tor-managed onion service.

Parameter Type Default Description
transports.tor.mode string "socks5" Tor access mode: socks5 (outbound only), control_port (outbound + monitoring), or directory (outbound + inbound onion service)
transports.tor.socks5_addr string "127.0.0.1:9050" SOCKS5 proxy address (host:port)
transports.tor.connect_timeout_ms u64 120000 Connect timeout in milliseconds. Tor circuits take 1060s.
transports.tor.mtu u16 1400 Default MTU
transports.tor.control_addr string "/run/tor/control" Tor control port address: Unix socket path or host:port. Used in control_port mode; optional in directory mode for monitoring.
transports.tor.control_auth string "cookie" Control port authentication: "cookie", "cookie:/path/to/cookie", or "password:<secret>".
transports.tor.cookie_path string "/var/run/tor/control.authcookie" Path to Tor control cookie file. Used when control_auth is "cookie".
transports.tor.max_inbound_connections usize 64 Maximum inbound connections via onion service.
transports.tor.directory_service.hostname_file string "/var/lib/tor/fips_onion_service/hostname" Path to Tor-managed hostname file containing the .onion address.
transports.tor.directory_service.bind_addr string "127.0.0.1:8443" Local bind address for the listener that Tor forwards inbound connections to. Must match HiddenServicePort target in torrc.
transports.tor.advertised_port u16 443 Public-facing onion port published in Nostr overlay adverts. Must match the virtual port in torrc's HiddenServicePort <port> 127.0.0.1:<bind_port> directive — that is the port other peers will use to reach this onion.

Named instances. Like other transports, multiple Tor instances can be configured with named sub-keys for different SOCKS5 proxy endpoints.

Directory mode (recommended for production). Tor manages the onion service via HiddenServiceDir in torrc. FIPS reads the .onion address from the hostname file and binds a local TCP listener. This enables Tor's Sandbox 1 (seccomp-bpf). If control_addr is also set, the transport connects to the control port for daemon monitoring (non-fatal on failure).

Control port mode. Connects to the Tor daemon's control port for monitoring only (bootstrap status, circuit health, traffic stats). No inbound connections. Both control_addr and control_auth are required.

UDP + Tor Bridge Example

A node bridging clearnet (UDP) and anonymous (Tor) portions of the mesh:

node:
  identity:
    persistent: true

tun:
  enabled: true

transports:
  udp:
    bind_addr: "0.0.0.0:2121"
    mtu: 1472
  tor:
    socks5_addr: "127.0.0.1:9050"

peers:
  - npub: "npub1abc..."
    alias: "clearnet-peer"
    addresses:
      - transport: udp
        addr: "203.0.113.5:2121"
  - npub: "npub1def..."
    alias: "anonymous-peer"
    addresses:
      - transport: tor
        addr: "abc123...xyz.onion:2121"

Tor Directory Mode Example

A node accepting inbound connections via Tor-managed onion service (recommended for production — enables Sandbox 1):

node:
  identity:
    persistent: true

tun:
  enabled: true

transports:
  tor:
    mode: "directory"
    socks5_addr: "127.0.0.1:9050"
    control_addr: "/run/tor/control"    # optional, for monitoring
    control_auth: "cookie"
    directory_service:
      hostname_file: "/var/lib/tor/fips/hostname"
      bind_addr: "127.0.0.1:8444"

peers:
  - npub: "npub1abc..."
    alias: "tor-peer"
    addresses:
      - transport: tor
        addr: "abcdef...xyz.onion:8443"

Requires a corresponding torrc:

HiddenServiceDir /var/lib/tor/fips
HiddenServicePort 8443 127.0.0.1:8444

Nym (transports.nym.*)

Nym transport routes FIPS traffic through the Nym mixnet for metadata-resistant anonymity. Outbound-only: connections are made through a nym-socks5-client SOCKS5 proxy that must be running separately (e.g. as a service running alongside the fips daemon or as a container). There is no inbound listener — a Nym-only node initiates outbound links but is not reachable for unsolicited inbound handshakes.

Parameter Type Default Description
transports.nym.socks5_addr string "127.0.0.1:1080" nym-socks5-client SOCKS5 proxy address (host:port)
transports.nym.connect_timeout_ms u64 300000 Outbound connect timeout in milliseconds. Mixnet SOCKS5 connections traverse 3 mix nodes with timing obfuscation and can take several minutes, so this is generous (300s).
transports.nym.mtu u16 1400 Default MTU
transports.nym.startup_timeout_secs u64 120 Seconds to wait for nym-socks5-client to become ready at startup before giving up

Named instances. Like other transports, multiple Nym instances can be configured with named sub-keys for different SOCKS5 proxy endpoints.

BLE (transports.ble.*)

Bluetooth Low Energy transport using L2CAP Connection-Oriented Channels. Linux + glibc only — at build time, build.rs probes for the BlueZ / bluer crate dependencies and sets the bluer_available cfg; the BLE runtime is gated behind #[cfg(bluer_available)]. There is no Cargo feature flag to toggle. On non-glibc Linux (musl) or non-Linux platforms, BLE config still parses but the transport runtime is absent and config entries become no-ops. Communicates with BlueZ via D-Bus through the bluer crate.

Parameter Type Default Description
transports.ble.adapter string "hci0" HCI adapter name
transports.ble.psm u16 0x0085 (133) L2CAP Protocol/Service Multiplexer
transports.ble.mtu u16 2048 Default MTU. Actual MTU is negotiated per-link during L2CAP connection setup.
transports.ble.max_connections usize 7 Maximum concurrent BLE connections
transports.ble.connect_timeout_ms u64 10000 Outbound connect timeout in milliseconds
transports.ble.advertise bool true Broadcast BLE beacon advertisements for peer discovery
transports.ble.scan bool true Listen for BLE beacon advertisements from other nodes
transports.ble.auto_connect bool false Automatically connect to discovered peers
transports.ble.accept_connections bool true Accept incoming L2CAP connections
transports.ble.probe_cooldown_secs u64 30 Cooldown before re-probing the same BLE address

Address format. BLE peer addresses use the form "adapter/device_address" — for example, "hci0/AA:BB:CC:DD:EE:FF".

Advertising and scanning. When advertise is enabled, the transport advertises the FIPS service UUID continuously so that nearby nodes can discover and connect via L2CAP. When scan is enabled, the transport continuously scans for other FIPS nodes' advertisements. Discovered peers are probed immediately (L2CAP connect + pubkey exchange) with a cooldown (probe_cooldown_secs) to prevent rapid re-probing of the same address. If two nodes probe each other at the same time (cross-probe), a deterministic tie-breaker based on NodeAddr comparison ensures only one connection is established.

Connection pool. The max_connections parameter limits the number of concurrent BLE connections. When the pool is full, the least-recently-used connection is evicted to make room for new connections.

BLE Example

A node using BLE for local mesh discovery alongside UDP for internet peers:

node:
  identity:
    persistent: true

tun:
  enabled: true

transports:
  udp:
    bind_addr: "0.0.0.0:2121"
  ble:
    adapter: "hci0"
    advertise: true
    scan: true
    auto_connect: true
    accept_connections: true

peers:
  - npub: "npub1abc..."
    alias: "internet-peer"
    addresses:
      - transport: udp
        addr: "203.0.113.5:2121"
    connect_policy: auto_connect

BLE peers on the local radio range are discovered automatically via beacons — no static peer entries needed. Internet peers still require explicit configuration.

Peers (peers[])

Static peer list. Each entry defines a peer to connect to.

Parameter Type Default Description
peers[].npub string (required) Peer's Nostr public key (npub-encoded)
peers[].alias string (none) Human-readable name for logging
peers[].addresses list [] Transport addresses for the peer. May be left empty (or omitted) when via_nostr: true, in which case the daemon resolves endpoints from the peer's Nostr advert at dial time.
peers[].addresses[].transport string (required) Transport type: udp, tcp, ethernet, tor, or ble
peers[].addresses[].addr string (required) Transport address. UDP/TCP: "host:port" (IP or DNS hostname). Ethernet: "interface/mac" (e.g., "eth0/aa:bb:cc:dd:ee:ff"). BLE: "adapter/device_address" (e.g., "hci0/AA:BB:CC:DD:EE:FF"). Tor: ".onion:port" or "host:port"
peers[].addresses[].priority u8 100 Address priority (lower = preferred)
peers[].connect_policy string "auto_connect" Connection policy: auto_connect, on_demand, or manual. Note: on_demand and manual are reserved for future use; the only policy currently honored at runtime is auto_connect.
peers[].auto_reconnect bool true Automatically reconnect after MMP link-dead removal (exponential backoff, unlimited retries)
peers[].via_nostr bool false Append Nostr advert-derived endpoints after static addresses for this peer

Gateway (gateway.*)

The gateway.* block configures the optional fips-gateway service, which lets unmodified LAN hosts reach mesh destinations through DNS proxy + virtual-IP NAT (and, optionally, exposes LAN-side services back into the mesh through inbound port forwards). The gateway is a separate service from the FIPS daemon but reads the same fips.yaml file. The block is read only when fips-gateway is running; the fips daemon ignores it. Linux only — the field is gated behind #[cfg(target_os = "linux")]. For setup, see ../how-to/deploy-gateway.md; for the end-to-end design, see ../design/fips-gateway.md.

Parameter Type Default Description
gateway.enabled bool false Enable the gateway. Must be true for fips-gateway to start.
gateway.pool string (required) Virtual IPv6 pool CIDR (e.g., "fd01::/112"). Must not overlap with the FIPS mesh address space (fd00::/8) or any address space already in use on the LAN. The /112 size yields 65 536 virtual IPs, which is the gateway's hard cap regardless of CIDR width.
gateway.lan_interface string (required) LAN-facing network interface name (e.g., "enp3s0"). Used for proxy-NDP entry installation so LAN clients can resolve the link-layer address of allocated virtual IPs.
gateway.pool_grace_period u64 60 Seconds a virtual-IP allocation is retained after its last referencing session ends, before the address is returned to the free pool. Larger values reduce churn for short-lived flows; smaller values reclaim addresses faster.

Gateway DNS (gateway.dns.*)

Settings for the gateway's DNS listener and its upstream link to the FIPS daemon's .fips resolver. The gateway proxies .fips queries to the daemon's resolver, which returns mesh addresses; the gateway then allocates a virtual IP from the pool and rewrites the response. Non-.fips queries are answered with REFUSED.

Parameter Type Default Description
gateway.dns.listen string "[::1]:5353" DNS listen address. The default binds IPv6 loopback on an unprivileged port, matching the canonical deployment where another resolver on the host (dnsmasq, systemd-resolved, BIND) holds port 53 and forwards .fips queries to the gateway over loopback. Bind on the LAN-side IP (e.g., "192.168.1.1:53") or wildcard ("[::]:53") only on hosts with no other resolver on 53 and where LAN clients query the gateway directly. See ../how-to/troubleshoot-gateway.md.
gateway.dns.upstream string "[::1]:5354" Upstream FIPS daemon resolver. Must match the daemon's dns.bind_addr and dns.port. Defaults match the daemon defaults (::1:5354). A v4 upstream ("127.0.0.1:5354") cannot reach a daemon bound on [::1]:5354 — Linux IPv6 sockets bound to explicit ::1 do not accept v4-mapped traffic. If you change the daemon's dns.bind_addr, update this field accordingly.
gateway.dns.ttl u32 60 TTL in seconds on AAAA responses returned to LAN clients. Smaller values let the gateway recycle pool addresses faster; larger values reduce LAN-side query traffic.

Conntrack (gateway.conntrack.*)

Linux conntrack timeout overrides for the gateway's NAT table. These adjust the kernel-default timeouts for NAT sessions installed by the gateway. All values are in seconds; omit any field to inherit the gateway's built-in default (which itself usually matches the kernel default for that protocol).

Parameter Type Default Description
gateway.conntrack.tcp_established u64 432000 TCP established-state timeout (5 days). Long-lived TCP flows (SSH, persistent HTTP) keep their NAT mapping alive for at least this long without traffic.
gateway.conntrack.udp_timeout u64 30 UDP unreplied timeout. Applied until reply traffic is observed in the reverse direction.
gateway.conntrack.udp_assured u64 180 UDP assured (bidirectional) timeout. Applied once reply traffic has been observed.
gateway.conntrack.icmp_timeout u64 30 ICMP echo / error timeout.

Inbound Port Forwards (gateway.port_forwards[])

Optional list of inbound port-forward rules. Each rule maps a TCP or UDP port on the gateway's fips0 mesh-side address to a host:port on the LAN. Mesh peers connect to the gateway's mesh address on the listen port; the gateway terminates the connection and forwards the payload to the LAN target. This is the inverse of the outbound mode: the LAN service is exposed to the mesh, not the other way around. See ../how-to/deploy-gateway.md for the operator recipe.

Parameter Type Default Description
gateway.port_forwards[].listen_port u16 (required) Port on fips0 that mesh peers connect to. Must be non-zero. The (listen_port, proto) pair must be unique across the list.
gateway.port_forwards[].proto string (required) Transport protocol: tcp or udp.
gateway.port_forwards[].target string (required) LAN destination as IPv6 [addr]:port (e.g., "[fd12:3456::10]:80"). IPv4 targets are rejected at config-load time.

Gateway Example

A typical gateway with both outbound (LAN-to-mesh) and inbound (mesh-to-LAN) modes enabled:

gateway:
  enabled: true
  pool: "fd01::/112"
  lan_interface: "enp3s0"
  dns:
    listen: "[::1]:5353"
    upstream: "[::1]:5354"
    ttl: 60
  pool_grace_period: 60
  conntrack:
    tcp_established: 432000
    udp_assured: 180
  port_forwards:
    - listen_port: 8080
      proto: tcp
      target: "[fd12:3456::10]:80"
    - listen_port: 5353
      proto: udp
      target: "[fd12:3456::10]:53"

Minimal Example

A typical node configuration enabling TUN, DNS, and a single peer:

node:
  identity:
    nsec: "0102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f20"

tun:
  enabled: true
  name: fips0
  mtu: 1280

dns:
  enabled: true
  bind_addr: "127.0.0.1"
  port: 53

transports:
  udp:
    bind_addr: "0.0.0.0:2121"
    mtu: 1472

peers:
  - npub: "npub1tdwa4vjrjl33pcjdpf2t4p027nl86xrx24g4d3avg4vwvayr3g8qhd84le"
    alias: "node-b"
    addresses:
      - transport: udp
        addr: "172.20.0.11:2121"
    connect_policy: auto_connect

Mixed UDP + Ethernet Example

A node bridging internet peers (UDP) and a local Ethernet segment with neighbor beacons:

node:
  identity:
    nsec: "0102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f20"

tun:
  enabled: true

transports:
  udp:
    bind_addr: "0.0.0.0:2121"
    mtu: 1472
  ethernet:
    interface: "eth0"
    listen: true
    announce: true
    auto_connect: true
    accept_connections: true

peers:
  - npub: "npub1tdwa4vjrjl33pcjdpf2t4p027nl86xrx24g4d3avg4vwvayr3g8qhd84le"
    alias: "internet-peer"
    addresses:
      - transport: udp
        addr: "203.0.113.5:2121"
    connect_policy: auto_connect

Ethernet peers on the local segment are discovered automatically via beacons — no static peer entries needed. Internet peers still require explicit configuration.

All node.* parameters use their defaults. To override specific values, add only the relevant sections:

node:
  identity:
    nsec: "..."
  limits:
    max_peers: 64
  retry:
    max_retries: 10
    max_backoff_secs: 600
  cache:
    coord_size: 100000

Complete Reference

The full YAML structure with all defaults:

node:
  identity:
    nsec: null                       # secret key in nsec or hex (null = depends on persistent)
    persistent: false                # true = load/save fips.key; false = ephemeral each start
  leaf_only: false
  tick_interval_secs: 1
  base_rtt_ms: 100
  heartbeat_interval_secs: 10
  link_dead_timeout_secs: 30
  limits:
    max_connections: 256
    max_peers: 128
    max_links: 256
    max_pending_inbound: 1000
  rate_limit:
    handshake_burst: 100
    handshake_rate: 10.0
    handshake_timeout_secs: 30
    handshake_resend_interval_ms: 1000
    handshake_resend_backoff: 2.0
    handshake_max_resends: 5
  retry:
    max_retries: 5
    base_interval_secs: 5
    max_backoff_secs: 300
  cache:
    coord_size: 50000
    coord_ttl_secs: 300
    identity_size: 10000
  discovery:
    ttl: 64
    attempt_timeouts_secs: [1, 2, 4, 8]
    recent_expiry_secs: 10
    backoff_base_secs: 0
    backoff_max_secs: 0
    forward_min_interval_secs: 2
    # lan:                             # uncomment to enable mDNS LAN discovery
    #   enabled: true                  # opt-in, default false
    #   scope: "my-mesh"               # optional per-network scope filter
  tree:
    announce_min_interval_ms: 500
    parent_hysteresis: 0.2              # cost improvement fraction for parent switch
    hold_down_secs: 30                  # suppress re-evaluation after switch
    reeval_interval_secs: 60            # periodic cost-based re-evaluation (0 = disabled)
    flap_threshold: 4                    # parent switches before dampening
    flap_window_secs: 60                 # sliding window for flap detection
    flap_dampening_secs: 120             # extended hold-down on flap
  bloom:
    update_debounce_ms: 500
    max_inbound_fpr: 0.20            # antipoison cap on inbound FilterAnnounce FPR
  session:
    default_ttl: 64
    pending_packets_per_dest: 16
    pending_max_destinations: 256
    idle_timeout_secs: 90
    coords_warmup_packets: 5
    coords_response_interval_ms: 2000
  mmp:
    mode: full                       # full | lightweight | minimal
    log_interval_secs: 30
    owd_window_size: 32
  session_mmp:
    mode: full                       # full | lightweight | minimal
    log_interval_secs: 30
    owd_window_size: 32
  ecn:
    enabled: true                    # ECN congestion signaling (CE flag relay)
    loss_threshold: 0.05             # MMP loss rate threshold for CE marking (5%)
    etx_threshold: 3.0               # MMP ETX threshold for CE marking
  rekey:
    enabled: true                    # periodic Noise rekey for forward secrecy
    after_secs: 120                  # rekey interval (seconds)
    after_messages: 65536            # rekey after N messages sent
  control:
    enabled: true
    socket_path: null                # null = auto ($XDG_RUNTIME_DIR → /run/fips → /tmp fallback)
  buffers:
    packet_channel: 1024
    tun_channel: 1024
    dns_channel: 64

tun:
  enabled: false
  name: "fips0"
  mtu: 1280

dns:
  enabled: true
  bind_addr: "::1"
  port: 5354
  ttl: 300

transports:
  udp:
    bind_addr: "0.0.0.0:2121"
    mtu: 1280
    recv_buf_size: 2097152           # 2 MB (kernel doubles to 4 MB actual)
    send_buf_size: 2097152           # 2 MB
  # ethernet:                        # uncomment to enable (requires CAP_NET_RAW)
  #   interface: "eth0"              # required: network interface name
  #   ethertype: 0x2121              # default EtherType
  #   mtu: null                      # null = interface MTU - 3 (typically 1497)
  #   recv_buf_size: 2097152         # 2 MB
  #   send_buf_size: 2097152         # 2 MB
  #   listen: true                   # listen for beacons
  #   announce: false                # broadcast beacons
  #   auto_connect: false            # connect to discovered peers
  #   accept_connections: false      # accept inbound handshakes
  #   beacon_interval_secs: 30       # beacon interval (min 10)
  # tcp:                             # uncomment to enable TCP transport
  #   bind_addr: "0.0.0.0:8443"     # listen address (omit for outbound-only)
  #   mtu: 1400                      # default MTU
  #   connect_timeout_ms: 5000       # outbound connect timeout
  #   nodelay: true                  # TCP_NODELAY
  #   keepalive_secs: 30             # keepalive interval (0 = disabled)
  #   recv_buf_size: 2097152         # 2 MB
  #   send_buf_size: 2097152         # 2 MB
  #   max_inbound_connections: 256   # resource protection limit
  # tor:                             # uncomment to enable Tor transport
  #   mode: "socks5"                 # "socks5", "control_port", or "directory"
  #   socks5_addr: "127.0.0.1:9050" # SOCKS5 proxy address
  #   connect_timeout_ms: 120000    # connect timeout (120s for Tor circuits)
  #   mtu: 1400                     # default MTU
  #   # monitoring (control_port mode, or optional in directory mode):
  #   # control_addr: "/run/tor/control"   # Unix socket or host:port
  #   # control_auth: "cookie"             # "cookie" or "password:<secret>"
  #   # cookie_path: "/var/run/tor/control.authcookie"
  #   # directory mode (inbound via Tor-managed onion service):
  #   # directory_service:
  #   #   hostname_file: "/var/lib/tor/fips_onion_service/hostname"
  #   #   bind_addr: "127.0.0.1:8443"
  #   # max_inbound_connections: 64
  #   # advertised_port: 443           # public-facing onion port for Nostr adverts
  # nym:                              # uncomment to enable Nym mixnet transport (outbound-only)
  #   socks5_addr: "127.0.0.1:1080" # nym-socks5-client SOCKS5 proxy address
  #   connect_timeout_ms: 300000    # connect timeout (300s for mixnet)
  #   mtu: 1400                     # default MTU
  #   startup_timeout_secs: 120     # wait for nym-socks5-client to be ready
  # ble:                              # uncomment to enable BLE transport (Linux only, requires BlueZ)
  #   adapter: "hci0"                 # HCI adapter name
  #   psm: 0x0085                     # L2CAP PSM (133)
  #   mtu: 2048                       # default MTU (negotiated per-link)
  #   max_connections: 7              # max concurrent BLE connections
  #   connect_timeout_ms: 10000       # outbound connect timeout
  #   advertise: true                 # broadcast BLE beacons
  #   scan: true                      # listen for BLE beacons
  #   auto_connect: false             # connect to discovered peers
  #   accept_connections: true         # accept incoming L2CAP connections
  #   probe_cooldown_secs: 30         # cooldown before re-probing same address

peers:                               # static peer list
  # - npub: "npub1..."
  #   alias: "node-b"
  #   addresses:
  #     - transport: udp
  #       addr: "10.0.0.2:2121"
  #       priority: 100
  #   connect_policy: auto_connect
  #   auto_reconnect: true           # reconnect after link-dead removal