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Add a generic NAT table: port forward, source NAT, masquerade

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router.firewall.nat replaces the dnat/toPort/hairpin fields of the filter
rules. Filter rules gain natOnly, and may use wan with log and rate limit
in the web UI. The Firewall page edits the NAT table and can add the
matching allow rule. Settings schema 1 (migrations/1.jq) converts old
forwards.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AeFqV9dZrK6nipHkPfyM4F
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nils
2026-10-30 15:54:29 +01:00
co-authored by Claude Sonnet 5.5
parent 3e9c2e4a7a
commit a58600823f
19 changed files with 1018 additions and 505 deletions
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PLAN.md
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@@ -105,10 +105,11 @@ Learned along the way:
- Router services stay per LAN: DNS and DHCP always, SSH only with `allowManagement`.
- Kea subnet IDs are derived from the network address, so adding or removing LANs does not shift IDs (and orphan persistent leases).
## Port forwards (confirmed)
## Port forwards and NAT (confirmed)
- Implemented by extending `router.firewall.rules` with a reserved source zone `wan` (no LAN/tunnel may use that zone name; `wan` is never a destination).
- Extra rule fields: `dnat` (IPv4 only, single host destination, tcp/udp), `toPort`, port ranges (`"9000-9002"`), `sources` allow-list (v4/v6 CIDRs), `rateLimit` (`N/second|minute|hour`, per source via nft meter), `log`, `hairpin` (NAT loopback for LANs/tunnels with `internet = true`; masquerades so replies return via the router).
- Filtering and translation are separate. `router.firewall.rules` only filter and may use the reserved source zone `wan` (no LAN/tunnel may use that zone name; `wan` is never a destination). Rule fields: port ranges (`"9000-9002"`), `sources` allow-list (v4/v6 CIDRs), `rateLimit` (`N/second|minute|hour`, per source via nft meter), `log`, `natOnly` (only connections a DNAT rule translated).
- `router.firewall.nat` is the translation table: `type` `dnat` (IPv4 only, one host `toAddress` in the `to` zone, tcp/udp, optional `toPort`, `hairpin` from `wan`: NAT loopback for LANs/tunnels with `internet = true`; masquerades so replies return via the router), `snat` (`toAddress`) and `masquerade`, matching `from`, `sources`, `destination` (default: the router's own addresses), protocol and ports.
- The web UI's NAT table can also add the matching filter rule ("also allow", a `natOnly` rule). Schema 1 (`migrations/1.jq`) converts the old rules with `dnat` into a NAT row plus such a rule.
- Safeguards: a rule from `wan` must name a destination, an explicit protocol and its ports, so a typo cannot expose a whole zone.
- IPv6 has no NAT: it is opened only by explicit pinholes (`from = "wan"`, IPv6 `destination`). The prefix is dynamic, so v6 destinations are not checked against the zone.
- Tested in `basic`/`pppoe` (source preserved, toPort, ranges, sources, rate limit, v6 pinhole, hairpin, log lines) and in `assertions`; mutation-tested (source match, hairpin masquerade, rate limit).
@@ -157,7 +158,7 @@ Open (in rough order):
3. ~~**Tunnel trust and addressing**~~ **done**: tunnels may have no address; the new `wireguard.<n>.sourceAddresses` sets the source (`PreferredSource`) for router-originated traffic into an addressless tunnel (e.g. DNS to Troisdorf; tested, mutation-tested). Antigua's blanket `trustedInterfaces` is spelled out as per-tunnel `allowManagement`/`dns` plus zone rules in `examples/home`. The default device name `wg-<name>` must fit 15 characters (caught by an assertion: `mobile-clients` became `mobile`).
4. ~~**PPP device name**~~ **done**: `ddclient` in `examples/home` uses `config.router.wan.ipv4.interface` (`pppoe-wan`) instead of a hard-coded name. DDNS has since moved into the module (`router.ddns`, a web UI page; tested in `ddns`): `examples/home` can drop its `services.ddclient` for it.
5. **Credentials**: the PPPoE password is assigned by the ISP (cannot be rotated) and is plaintext in antigua's repo/store; never copy it into a repo again. Here it is read from `/var/lib/router/pppoe-password` (delivered with `router-install --secrets`). The PPPoE username in `examples/home` is a placeholder.
6. **Services that stay on antigua** (k3s, Gitea, Syncthing, WoW, Traefik) were reachable from the WAN because antigua *was* the router. On the new router they need explicit port forwards to the host's address (`firewall.rules` with `from = "wan"`); antigua's address on the LAN also changes (k3s nodeIP and the `antigua.mch` record point at 192.168.168.254 today). **Open: needs the host's new address and the list of public ports.**
6. **Services that stay on antigua** (k3s, Gitea, Syncthing, WoW, Traefik) were reachable from the WAN because antigua *was* the router. On the new router they need explicit port forwards to the host's address (a NAT row on the Firewall page); antigua's address on the LAN also changes (k3s nodeIP and the `antigua.mch` record point at 192.168.168.254 today). **Open: needs the host's new address and the list of public ports.**
7. `examples/home` (`nixosConfigurations.home`, `packages.installer-home`) ports antigua's routing role; its toplevel builds as the `home` check. Not VM-testable as a whole (needs the real ISP); its pieces are covered by the component tests.
## Installer and image (in progress)