Files
nixos-router/modules/router/dns.nix
T
nilsandClaude Sonnet 5.5 c395a43a78 Add a static ULA per LAN, announced via SLAAC and RDNSS
lans.<n>.ipv6.address (a ULA /64) is assigned to the LAN, announced
with an explicit prefix (networkd only announces the delegated prefix
when prefix delegation is on) and advertised as RDNSS; Unbound listens
and answers on it. Checked at build time: valid IPv6 CIDR, /64, fc00::/7.

Covered by the onestick VM test (client SLAAC address, ping and DNS over
the ULA, RA captured on the wire), assertion cases and a unit test for
the /64 prefix helper.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
2026-10-28 15:48:47 +01:00

95 lines
3.5 KiB
Nix

{ config, lib, ... }:
let
cfg = config.router;
lans = lib.attrValues cfg.lans;
ipv4 = (import ./lib.nix { inherit lib; }).ipv4;
# Tunnels that opted into DNS: listen on each of their addresses.
dnsAddrs = lib.concatMap (w: w.addresses) (lib.filter (w: w.dns) (lib.attrValues cfg.wireguard));
addrOf = a: builtins.head (lib.splitString "/" a);
# IPv4 gets the proper network address; IPv6 netblocks are masked by Unbound.
netOf =
a:
let
parts = lib.splitString "/" a;
in
if lib.hasInfix ":" a then
a
else
ipv4.cidr (builtins.head parts) (lib.toInt (builtins.elemAt parts 1));
dns = cfg.dns;
inherit (dns) domain;
fqdn = name: if lib.hasInfix "." name || domain == null then name else "${name}.${domain}";
isV6 = lib.hasInfix ":";
rrOf = a: if isV6 a then "AAAA" else "A";
# name -> addresses: explicit hosts plus DHCP reservations (A records only).
reservations = lib.concatMap (
l: lib.mapAttrsToList (n: r: lib.nameValuePair n [ r.address ]) l.dhcp.reservations
) lans;
records =
lib.mapAttrsToList (n: a: lib.nameValuePair (fqdn n) a) dns.hosts
++ map (r: lib.nameValuePair (fqdn r.name) r.value) reservations
++ lib.mapAttrsToList (n: a: lib.nameValuePair n a) dns.overrides;
# Unbound reads these as one quoted argument.
localData = lib.concatMap (r: map (a: ''"${r.name}. ${rrOf a} ${a}"'') r.value) records;
# Reverse records for hosts and reservations (not for wildcard overrides).
ptrs = lib.concatMap (r: map (a: ''"${a} ${r.name}."'') r.value) (
lib.filter (r: !(lib.hasAttr r.name dns.overrides)) records
);
privateZones = lib.attrNames dns.forwardZones ++ lib.optional (domain != null) domain;
# Peers of tunnels that use the resolver may be remote networks with no
# address of their own on the tunnel (site-to-site); allow what they route.
dnsPeerNets = lib.filter (n: !lib.hasSuffix "/0" n) (
lib.concatMap (w: lib.concatMap (p: p.allowedIPs) (lib.attrValues w.peers)) (
lib.filter (w: w.dns) (lib.attrValues cfg.wireguard)
)
);
in
{
config = lib.mkIf cfg.enable {
services.unbound = {
enable = true;
settings = {
server = {
interface = [
"127.0.0.1"
]
++ map (l: l.ipv4.address) lans
++ map (l: addrOf l.ipv6.address) (lib.filter (l: l.ipv6.address != null) lans)
++ map addrOf dnsAddrs;
# LAN addresses are assigned by networkd, possibly after Unbound starts.
ip-freebind = true;
access-control = [
"127.0.0.0/8 allow"
]
++ map (l: "${l.ipv4.subnet} allow") lans
++ map (l: "${l.ipv6.address} allow") (lib.filter (l: l.ipv6.address != null) lans)
++ map (a: "${netOf a} allow") dnsAddrs
++ map (n: "${n} allow") dnsPeerNets;
local-zone =
lib.optional (domain != null) "${domain}. static"
++ map (n: "${n}. redirect") (lib.attrNames dns.overrides);
local-data = localData;
local-data-ptr = ptrs;
domain-insecure = privateZones ++ lib.attrNames dns.overrides;
};
}
// lib.optionalAttrs (cfg.dns.forwarders != [ ] || dns.forwardZones != { }) {
forward-zone =
lib.mapAttrsToList (name: addrs: {
inherit name;
forward-addr = addrs;
}) dns.forwardZones
++ lib.optional (cfg.dns.forwarders != [ ]) {
name = ".";
forward-addr = cfg.dns.forwarders;
};
};
};
};
}