fips/docs/how-to/deploy-gateway.md

Deploy fips-gateway (Manual Linux-Host Setup)

fips-gateway is a separate service that runs alongside the FIPS daemon and bridges a non-FIPS LAN to the FIPS mesh in two independent directions: outbound (LAN clients reach mesh services through DNS proxy + virtual-IP NAT) and inbound (mesh peers reach LAN services through 1:1 port forwards on fips0). This guide covers the manual Linux-host deployment path — wiring DNS forwarding, route distribution, and firewall integration on a server or non-OpenWrt router by hand.

Running OpenWrt? Use the tutorial instead. The OpenWrt ipk ships with the gateway: block pre-populated and the init script automates dnsmasq forwarding, RA route distribution, and the global IPv6 prefix on br-lan. The OpenWrt path is the canonical deployment of this feature; this how-to is the secondary path for operators with a different LAN-edge box (a Linux server already serving DHCP/DNS, a custom router distribution, etc.).

For the gateway design (NAT pipeline, virtual IP pool lifecycle, DNS resolution flow), see ../design/fips-gateway.md. For the full gateway.* configuration block, see the Gateway section of the configuration reference. For the fips-gateway binary's CLI flags, see ../reference/cli-fips-gateway.md.

The two halves

The gateway exposes two independent features that share a common control plane (the same binary, the same nftables table inet fips_gateway, the same control socket /run/fips/gateway.sock, the same gateway.* config block). You can configure either half on its own or both together.

• Outbound gateway (LAN → mesh). Non-FIPS LAN workstations resolve <npub>.fips names against the gateway's DNS listener and receive AAAA answers from the gateway's virtual-IP pool. Outbound traffic to those addresses is DNAT'd to the real mesh address and SNAT'd (masqueraded) onto fips0 under the gateway's mesh identity. The audience is unmodified LAN clients.

• Inbound gateway (mesh → LAN). A static (listen_port, proto) → [target_addr]:target_port table — configured in gateway.port_forwards[] — exposes selected LAN services to the mesh as <gateway-npub>.fips:<listen_port>. Mesh peers connect to the gateway's mesh address; the gateway DNATs to the LAN target and masquerades on the LAN side so return traffic flows through conntrack. The audience is mesh peers reaching a service that happens to live on this LAN.

The two halves are independent. Configure the outbound half if you want LAN clients to reach the mesh; configure the inbound half if you want mesh peers to reach into the LAN; configure both if you want both.

Common gateway-host setup

Both halves require the same host preparation. Work through this section first, then jump to whichever half (or both) you need.

FIPS daemon prerequisites

The gateway runs alongside a fips daemon on the same host:

• The daemon must be running with the TUN adapter enabled (the fips0 interface must exist).
• The daemon's DNS resolver must be enabled (dns.enabled: true, default) and reachable from fips-gateway. By default that means [::1]:5354 (IPv6 loopback). The gateway's default dns.upstream matches this; a v4 upstream like 127.0.0.1:5354 cannot reach a daemon bound on [::1]:5354 because Linux IPv6 sockets bound to explicit ::1 do not accept v4-mapped traffic.

If the daemon is not yet running with these features, set up the daemon first — see persistent-identity.md and ../reference/configuration.md.

Kernel sysctls

sudo sysctl -w net.ipv6.conf.all.forwarding=1
sudo sysctl -w net.ipv6.conf.all.proxy_ndp=1

forwarding lets the host route IPv6 packets between the LAN interface and fips0. proxy_ndp lets the gateway answer Neighbor Solicitation requests for virtual-pool addresses so LAN clients can resolve their link-layer addresses (only relevant for the outbound half, but harmless if you only run the inbound half).

Persist via a drop-in:

sudo tee /etc/sysctl.d/60-fips-gateway.conf <<'EOF'
net.ipv6.conf.all.forwarding = 1
net.ipv6.conf.all.proxy_ndp = 1
EOF
sudo sysctl --system

Capability

fips-gateway requires CAP_NET_ADMIN to manage its nftables table (inet fips_gateway) and proxy-NDP entries. The packaged systemd unit (fips-gateway.service) runs as root, which satisfies this. For non-package installs, set the file capability:

sudo setcap cap_net_admin+ep /usr/bin/fips-gateway

Pool route

At startup fips-gateway adds local <pool-cidr> dev lo to the local routing table. This tells the kernel to accept packets destined for pool addresses as locally-owned, enabling the NAT processing path. The route is cleaned up on shutdown. You do not need to install it manually; if you see "destination unreachable" errors for pool addresses on the gateway host, verify the route is present:

ip -6 route show table local | grep <pool-cidr>

Minimum configuration

In /etc/fips/fips.yaml, populate the gateway block with at minimum enabled: true, pool, and lan_interface:

gateway:
  enabled: true
  pool: "fd01::/112"
  lan_interface: "enp3s0"

Pick a pool CIDR that does not overlap with any address space in use on the LAN. The gateway routes the whole prefix to itself, so a name whose mesh address (in fd00::/8) lies inside it cannot be reached and gets SERVFAIL; a /112 makes that vanishingly unlikely. The /112 size yields 65 535 usable addresses, the most the pool uses whatever the CIDR width. The gateway holds at most 1000 live mappings at once and admits new names at up to 10 per second after a burst of 50. At 1000 live mappings, a new name replaces the oldest mapping that has never carried traffic, and gets SERVFAIL only when every mapping has carried traffic; a new name beyond the rate limit gets SERVFAIL.

This minimum config is enough to start the gateway. The dns.* block is optional and defaults to listen: "[::1]:5365" and upstream: "[::1]:5354". The full block — including dns.*, pool_grace_period, conntrack.*, and port_forwards[] — is documented in ../reference/configuration.md#gateway-gateway.

Start the service

sudo systemctl enable --now fips-gateway

Verify the unit came up:

sudo systemctl status fips-gateway
sudo journalctl -u fips-gateway -e

The startup log will report Gateway config loaded, DNS upstream is reachable, Created nftables table 'fips_gateway', and finally fips-gateway running. The unit's ExecStartPre waits up to 30 s for fips0 to appear, which covers the cold-boot race where the daemon is still bringing up its TUN.

Configure the outbound half

The outbound half lets LAN clients resolve .fips names and reach mesh destinations. Three operator decisions are involved: pool CIDR, DNS listen address, and how LAN clients learn the route to the pool and the resolver address.

Choose the pool CIDR

gateway:
  pool: "fd01::/112"

Constraints:

• Must not overlap with any LAN-side IPv6 prefix already in use.
• A name whose mesh address (in fd00::/8) lies inside the pool prefix gets SERVFAIL, since the gateway routes the whole prefix to itself; a /112 makes that vanishingly unlikely.
• /112 is the practical width — wider just wastes address space because the pool never uses more than 65 535 addresses. Narrower is fine if you want a smaller pool; one narrower than /118 (1023 usable addresses) runs out before the 1000-mapping ceiling is reached, and one smaller than 1000 + 10 x (TTL + grace) addresses (2,200 at the defaults, so any pool narrower than a /116) can be exhausted by one LAN host naming new names; the gateway warns at start. After a crash or a kill (not a clean stop or restart), a pool with fewer than 512 free addresses (a /119 or narrower, or a /118 with more than about 500 addresses in use) refuses every new name for the DNS TTL plus the grace period, 2 minutes at the defaults, while it waits out answers the previous run may have given.

Choose the DNS listen address

gateway:
  dns:
    listen: "[::1]:5365"
    upstream: "[::1]:5354"
    ttl: 60

Common cases:

• Another resolver on the host (the canonical case): the default listen: "[::1]:5365" is loopback-only on an unprivileged port, so it never conflicts with dnsmasq, systemd-resolved, or BIND holding 53. Configure the existing resolver to forward .fips queries to [::1]:5365 and you are done — this is what the OpenWrt ipk does automatically. On OpenWrt the init script reads gateway.dns.listen and points dnsmasq at whatever port it sets.
• No other resolver on the host: set listen: "[::]:53" explicitly and LAN clients can query the gateway directly. Queries that arrive on fips0 are not answered, so a wildcard listen does not serve the mesh; this includes a local resolver that forwards to the gateway's fips0 address, so forward to loopback or a LAN address instead.
• systemd-resolved is on port 53: the default already side-steps this — leave the listen address at [::1]:5365 and configure the stub or a small forwarder to delegate .fips to the gateway. If you would rather have the gateway on 53 directly, disable the systemd stub listener (DNSStubListener=no in /etc/systemd/resolved.conf) and switch listen to "[::]:53". See troubleshoot-gateway.md.
• Bind on the LAN address only: listen: "192.168.1.1:53" exposes the resolver only to LAN clients, not loopback.

The gateway returns REFUSED for any non-.fips query — clients that point at it directly need a fallback resolver, or you should front it with a stub forwarder.

Distribute the route to LAN clients

Each LAN client must route the gateway's pool CIDR to the gateway's LAN-side IPv6 address. Three options, in order of preference for production:

• RA Route Information Option (RFC 4191). If the LAN's RA daemon (radvd, dnsmasq --enable-ra, OpenWrt's odhcpd) supports publishing route options, configure it to advertise the pool CIDR with the gateway as next-hop. Clients pick this up automatically.

• Static route on the LAN router. If clients route through a central LAN router, add a static route entry there — the router then handles forwarding to the gateway. The exact syntax depends on the router OS.

• Per-host static route (testing or single-client deployments):

  sudo ip -6 route add fd01::/112 via fe80::<gateway-link-local>%<iface>
  # or, if the gateway has a stable global LAN address:
  sudo ip -6 route add fd01::/112 via <gateway-lan-addr>
  

Distribute the resolver to LAN clients

LAN clients also need to send .fips queries to the gateway. Two patterns:

• Forward .fips from the LAN's main resolver. If the LAN runs Pi-hole, Unbound, dnsmasq, or systemd-resolved as the central resolver, configure a conditional forward for fips.. Unbound example:

  forward-zone:
      name: "fips."
      forward-addr: <gateway-lan-addr>@53
  

  dnsmasq example:

  server=/fips/<gateway-lan-addr>
  

  Clients keep their existing DNS settings; only .fips queries are diverted.

• Point clients directly at the gateway. Simpler for testing, but the gateway returns REFUSED for non-.fips queries, so each client must also have a fallback resolver configured.

Verify the outbound path

From a LAN client:

dig @<gateway-lan-addr> hostname.fips AAAA
# Expect an AAAA from the pool CIDR

ping6 hostname.fips
# Should succeed via the gateway

If either step fails, see troubleshoot-gateway.md.

Configure the inbound half

The inbound half exposes a LAN-side service to mesh peers. Configured under gateway.port_forwards[]:

gateway:
  port_forwards:
    - listen_port: 8080
      proto: tcp
      target: "[fd12:3456::10]:80"
    - listen_port: 2222
      proto: tcp
      target: "[fd12:3456::20]:22"
    - listen_port: 5353
      proto: udp
      target: "[fd12:3456::10]:53"

Field reference:

• listen_port — port on the gateway's fips0 mesh-side address that mesh peers connect to. Must be non-zero. Each (listen_port, proto) pair must be unique across the list (the same port on TCP and UDP is allowed; the same port twice on the same proto is rejected at config-load time).
• proto — tcp or udp.
• target — IPv6 LAN destination as [addr]:port. IPv4 targets are rejected at parse time by the YAML deserializer (the field is typed SocketAddrV6). If the LAN host is reachable only by IPv4, put a small IPv6-aware reverse proxy in front of it on the gateway itself.

Worked example: HTTP and DNS

Suppose the gateway runs on a LAN with an HTTP server at [fd12:3456::10]:80 and a recursive resolver at [fd12:3456::10]:53, and you want mesh peers to reach them as <gateway-npub>.fips:8080 (HTTP) and <gateway-npub>.fips:5353 (DNS). Add to the gateway's fips.yaml:

gateway:
  port_forwards:
    - listen_port: 8080
      proto: tcp
      target: "[fd12:3456::10]:80"
    - listen_port: 5353
      proto: udp
      target: "[fd12:3456::10]:53"

Reload:

sudo systemctl restart fips-gateway

From any mesh peer (the host name gateway is whatever the gateway's npub maps to in the local hosts file or via Nostr advert):

curl http://gateway.fips:8080/
dig @gateway.fips -p 5353 example.com A

Each mesh-side request enters fips0 on the listen port, gets DNAT'd to the LAN target, and the LAN-side masquerade rule rewrites the source to the gateway's LAN address so return traffic flows back through conntrack.

Compose with the mesh firewall

The mesh firewall baseline (/etc/fips/fips.nft, see enable-mesh-firewall.md) has two chains. Its inbound chain, on the input hook, polices traffic addressed to the gateway itself, and the drop-ins under /etc/fips/fips.d/*.nft are included there. A port forward never reaches it: the gateway rewrites a forwarded connection's destination to the LAN target in its prerouting chain, so the kernel routes the packet through the forward hook to the LAN. The baseline's forward chain sees it there, and accepts every port-forwarded connection from the mesh unless a drop-in under /etc/fips/fips.d/forward/ refuses it. With the baseline loaded and no forward drop-in, every mesh node that can reach the gateway can reach every configured port forward, and a fips.d/*.nft rule such as ip6 saddr <addr> tcp dport 8080 accept has no effect on it.

To restrict who can use a port forward, add a file ending in .nft to /etc/fips/fips.d/forward/ (create the directory if it is missing). Its lines are included into the forward chain after replies are accepted and before port-forwarded connections are. For each forward you restrict, write one line that accepts the nodes allowed to use it and one that drops everyone else. For the worked example above, allowing one mesh node to use both forwards:

# /etc/fips/fips.d/forward/port-forwards.nft
# Rules see the packet after the gateway rewrote its destination: match the
# target address and port, not listen_port. Replace the example mesh address
# with the allowed node's; `fipsctl address` on that node prints it.
ip6 daddr fd12:3456::10 tcp dport 80 ip6 saddr { fd97:1111:2222:3333:4444:5555:6666:7777 } accept
ip6 daddr fd12:3456::10 tcp dport 80 counter drop
ip6 daddr fd12:3456::10 udp dport 53 ip6 saddr { fd97:1111:2222:3333:4444:5555:6666:7777 } accept
ip6 daddr fd12:3456::10 udp dport 53 counter drop

A forward with no lines stays open to the mesh. Keep each forward's accept and drop lines in one file: the files are included in alphabetical order and the first matching rule decides, so an accept in a later file for a forward an earlier file already drops never matches. Write addresses out rather than with define; every drop-in is read into one ruleset, and two files that define the same name make the whole load fail.

Reload the firewall to apply it:

sudo systemctl reload-or-restart fips-firewall.service

The drop counters show refused connections:

sudo nft list chain inet fips forward

A refused connection times out on the peer rather than being reset. Connections from the mesh that the gateway did not translate, and LAN clients' own connections out to the mesh and their replies, pass the chain unchanged. A drop in any chain on the forward hook is final, so the order of this table against the gateway's own inet fips_gateway table does not matter.

Two cases from earlier releases. If you load a restriction table of your own, such as inet fips_port_forwards from /etc/fips/port-forwards.nft through a fips-firewall.service drop-in, it keeps working for the same reason; to move to the packaged chain, write its accept rules in the form above, then remove the service drop-in and delete that table. If you kept an edited /etc/fips/fips.nft when upgrading, your file has no forward chain and forward drop-ins are not loaded until you merge in the packaged one; sudo nft list chain inet fips forward fails until then.

On OpenWrt the packaged firewall zone already passes port forwards through fw4's forward chain; restrict them there with a src fips rule matching the target's port instead (see packaging/openwrt-ipk/README.md).

Verify the inbound path

From a mesh peer (any FIPS node):

curl -v http://<gateway-npub>.fips:8080/

A successful response confirms the full path: mesh ingress on fips0, DNAT to the LAN target, LAN-side masquerade, and conntrack- tracked return. If it fails, see troubleshoot-gateway.md.

Operate and verify

fips-gateway exposes its own control socket at /run/fips/gateway.sock, separate from the daemon's /run/fips/control.sock. There is no fipsctl gateway subcommand — talk to it directly:

echo '{"command":"show_gateway"}' | sudo nc -U /run/fips/gateway.sock
echo '{"command":"show_mappings"}' | sudo nc -U /run/fips/gateway.sock

show_gateway returns pool counters (pool_total, pool_allocated, pool_active, pool_draining, pool_free), nat_mappings, dns_listen, uptime_secs, and the active config snapshot. show_mappings returns the per-allocation list with virtual IP, mesh address, npub-derived node_addr, dns name, state (Allocated, Active, Draining), session count, and ages. For the full schema see ../reference/control-socket.md#gateway-command-catalog.

The journal is the other primary signal:

sudo systemctl status fips-gateway
sudo journalctl -u fips-gateway -e

Expect MappingCreated/MappingRemoved debug lines as DNS-driven allocations come and go (run with --log-level debug to see them), and Final pool status on shutdown. Errors in adding NAT rules or proxy-NDP entries surface here.

See also

• ../tutorials/deploy-fips-gateway.md — the canonical, package-driven OpenWrt deployment path.
• ../design/fips-gateway.md — gateway design, NAT pipeline, virtual IP pool lifecycle, security considerations.
• Gateway section of the configuration reference — full gateway.* block.
• ../reference/cli-fips-gateway.md — fips-gateway binary CLI flags.
• Gateway command catalog in the control-socket reference — JSON schema for show_gateway and show_mappings.
• troubleshoot-gateway.md — diagnostic recipes grouped by half.
• enable-mesh-firewall.md — mesh-firewall baseline and drop-ins (needed when exposing inbound ports).