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Add local DNS records, DHCP reservations and an installer ISO

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DNS and DHCP (needed to replace a dnsmasq-based router):
- router.dns.domain/hosts/overrides/forwardZones: authoritative local
  domain, split-horizon host records with reverse entries, wildcard
  overrides and per-zone forwarders (private zones skip DNSSEC).
- lans.<n>.dhcp.reservations: Kea host reservations, published in DNS.
- Tunnels with dns = true admit what their peers route, so a
  site-to-site peer without a transfer address can use the resolver.

Installer:
- router-install wipes a disk, creates an ESP and an ext4 root and
  installs a prebuilt system with its secrets; nothing is built on the
  box. installed-layout is the shared disk layout contract.
- lib.mkInstaller builds an ISO for a given nixosSystem;
  packages.installer-example is the example's ISO.

Covered by the dns and installer VM tests (the latter installs onto an
empty disk and boots it under UEFI), wireguard DNS and assertion cases.
PLAN.md records the remaining gaps for replacing the hand-written router.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
This commit is contained in:
nils
2026-10-28 12:31:44 +01:00
co-authored by Claude Sonnet 5.5
parent 0653b5cf2f
commit b5429ad876
15 changed files with 943 additions and 21 deletions
Download Patch File Download Diff File Expand all files Collapse all files
modules/router/assertions.nix
+105
View File
@@ -7,6 +7,12 @@ let
lans = lib.attrValues lansByName;
validIp = s: ipv4.parse s != null;
hostnameOk = s: builtins.match "[A-Za-z0-9]([A-Za-z0-9-]*[A-Za-z0-9])?" s != null;
# A DNS name: labels of letters, digits, dashes and underscores.
dnsNameOk =
s:
builtins.match "[A-Za-z0-9_]([A-Za-z0-9_-]*[A-Za-z0-9_])?(\\.[A-Za-z0-9_]([A-Za-z0-9_-]*[A-Za-z0-9_])?)*" s
!= null;
# Assertions about a single LAN; skipped (reported once) when its addresses
# do not even parse, so we never feed null into the integer helpers.
@@ -58,6 +64,60 @@ let
message = "router: ${where}.dhcp.pool contains the router's own address ${lan.ipv4.address}.";
}
]
)
++ lib.concatLists (
lib.mapAttrsToList (
host: r:
let
rwhere = "${where}.dhcp.reservations.${host}";
rok = validIp r.address;
in
[
{
assertion = hostnameOk host;
message = "router: ${rwhere}: `${host}` is not a valid hostname (letters, digits and dashes).";
}
{
assertion = builtins.match "([0-9a-fA-F]{2}:){5}[0-9a-fA-F]{2}" r.mac != null;
message = "router: ${rwhere}.mac `${r.mac}` is not a MAC address like aa:bb:cc:dd:ee:ff.";
}
{
assertion = rok;
message = "router: ${rwhere}.address `${r.address}` is not a valid IPv4 address.";
}
{
assertion = lan.dhcp.enable;
message = "router: ${rwhere}: reservations need dhcp.enable on the LAN.";
}
]
++ lib.optionals (rok && addrOk) [
{
assertion = ipv4.inSubnet net (ipv4.parse r.address);
message = "router: ${rwhere}.address ${r.address} is not inside ${lan.ipv4.subnet}.";
}
{
assertion = r.address != lan.ipv4.address;
message = "router: ${rwhere}.address is the router's own address.";
}
]
) lan.dhcp.reservations
)
++ (
let
rs = lib.attrValues lan.dhcp.reservations;
macs = map (r: lib.toLower r.mac) rs;
addrs = map (r: r.address) rs;
in
[
{
assertion = lib.length macs == lib.length (lib.unique macs);
message = "router: ${where}.dhcp.reservations: two reservations share a MAC address.";
}
{
assertion = lib.length addrs == lib.length (lib.unique addrs);
message = "router: ${where}.dhcp.reservations: two reservations share an address.";
}
]
);
wgs = lib.attrValues cfg.wireguard;
@@ -234,6 +294,50 @@ let
}
];
dnsCfg = cfg.dns;
anyIp = s: validIp s || v6Cidr "${s}/128";
dnsAssertions =
let
names =
lib.attrNames dnsCfg.hosts ++ lib.attrNames dnsCfg.overrides ++ lib.attrNames dnsCfg.forwardZones;
recordSets = dnsCfg.hosts // dnsCfg.overrides;
shortNames = lib.filter (n: !(lib.hasInfix "." n)) (lib.attrNames dnsCfg.hosts);
reservationNames = lib.concatMap (l: lib.attrNames l.dhcp.reservations) lans;
in
[
{
assertion = lib.all dnsNameOk names && (dnsCfg.domain == null || dnsNameOk dnsCfg.domain);
message = "router.dns: a name in domain/hosts/overrides/forwardZones is not a valid DNS name.";
}
{
assertion = lib.all (as: as != [ ] && lib.all anyIp as) (lib.attrValues recordSets);
message = "router.dns: every host/override needs at least one valid IPv4 or IPv6 address.";
}
{
assertion = lib.all (as: as != [ ] && lib.all anyIp as) (lib.attrValues dnsCfg.forwardZones);
message = "router.dns.forwardZones: every zone needs at least one valid resolver address.";
}
{
assertion = dnsCfg.domain != null || shortNames == [ ];
message = "router.dns.hosts: `${lib.concatStringsSep ", " shortNames}` has no dot, so router.dns.domain must be set.";
}
{
assertion =
lib.length (lib.attrNames dnsCfg.hosts) == lib.length (
lib.unique (
map (n: if lib.hasInfix "." n || dnsCfg.domain == null then n else "${n}.${dnsCfg.domain}") (
lib.attrNames dnsCfg.hosts
)
)
);
message = "router.dns.hosts: two names are the same once placed in the domain.";
}
{
assertion = lib.all (n: !(lib.elem n (lib.attrNames dnsCfg.hosts))) reservationNames;
message = "router.dns.hosts: a name is also a DHCP reservation, which already publishes it.";
}
];
overlapsLan = n: lib.any (l: ipv4.overlaps n l) lanNets;
wgAssertions =
@@ -347,6 +451,7 @@ in
}
]
++ lib.concatLists (lib.mapAttrsToList perLan lansByName)
++ dnsAssertions
++ lib.concatMap ruleAssertions cfg.firewall.rules
++ [
{
modules/router/dhcp.nix
+5
View File
@@ -27,6 +27,11 @@ in
inherit (l.ipv4) subnet;
interface = l.device;
pools = [ { pool = "${l.dhcp.pool.start} - ${l.dhcp.pool.end}"; } ];
reservations = lib.mapAttrsToList (hostname: r: {
hw-address = lib.toLower r.mac;
ip-address = r.address;
inherit hostname;
}) l.dhcp.reservations;
option-data = [
{
name = "routers";
modules/router/dns.nix
+47 -6
View File
@@ -17,6 +17,37 @@ let
a
else
ipv4.cidr (builtins.head parts) (lib.toInt (builtins.elemAt parts 1));
dns = cfg.dns;
inherit (dns) domain;
fqdn = name: if lib.hasInfix "." name || domain == null then name else "${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} ${r.name}."'') r.value) (
lib.filter (r: !(lib.hasAttr r.name dns.overrides)) records
);
privateZones = lib.attrNames dns.forwardZones ++ lib.optional (domain != null) domain;
# Peers of tunnels that use the resolver may be remote networks with no
# address of their own on the tunnel (site-to-site); allow what they route.
dnsPeerNets = lib.filter (n: !lib.hasSuffix "/0" n) (
lib.concatMap (w: lib.concatMap (p: p.allowedIPs) (lib.attrValues w.peers)) (
lib.filter (w: w.dns) (lib.attrValues cfg.wireguard)
)
);
in
{
config = lib.mkIf cfg.enable {
@@ -31,16 +62,26 @@ in
"127.0.0.0/8 allow"
]
++ map (l: "${l.ipv4.subnet} allow") lans
++ map (a: "${netOf a} allow") dnsAddrs;
++ map (a: "${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 != [ ]) {
forward-zone = [
{
// 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;
}
];
};
};
};
};
modules/router/options.nix
+72
View File
@@ -156,6 +156,29 @@ in
example = "192.168.10.199";
};
};
reservations = mkOption {
type = types.attrsOf (
types.submodule {
options = {
mac = mkOption {
type = types.str;
example = "a8:a1:59:0b:4b:97";
description = "Hardware address of the client.";
};
address = mkOption {
type = types.str;
example = "192.168.10.20";
description = "Address handed to the client; must lie inside the LAN.";
};
};
}
);
default = { };
description = ''
Fixed leases, keyed by hostname. The name is also sent to the
client and published in DNS (under `router.dns.domain` if set).
'';
};
};
ipv6.pd = mkOption {
@@ -415,6 +438,55 @@ in
);
};
dns.domain = mkOption {
type = types.nullOr types.str;
default = null;
example = "home.example.org";
description = ''
Local domain. It is authoritative on the router: names below it that
have no record answer NXDOMAIN and are never forwarded. Short names in
`dns.hosts` and DHCP reservation names live in it.
'';
};
dns.hosts = mkOption {
type = types.attrsOf (types.listOf types.str);
default = { };
example = {
nas = [ "192.168.10.20" ];
"git.example.org" = [
"10.43.0.50"
"fd00::50"
];
};
description = ''
Local records: name to IPv4/IPv6 addresses. A name without a dot is
placed in `dns.domain`; a full name overrides public DNS for that
name only (split horizon). Reverse records are created as well.
'';
};
dns.overrides = mkOption {
type = types.attrsOf (types.listOf types.str);
default = { };
example = {
"k8s.example.org" = [ "10.43.0.50" ];
};
description = "Like `dns.hosts`, but the name and everything below it answer with these addresses (wildcard).";
};
dns.forwardZones = mkOption {
type = types.attrsOf (types.listOf types.str);
default = { };
example = {
"branch.example.org" = [ "10.1.0.254" ];
};
description = ''
Zones answered by other resolvers (e.g. across a tunnel). DNSSEC
validation is skipped for them: they are private zones.
'';
};
dns.forwarders = mkOption {
type = types.listOf types.str;
default = [ ];