dns: auto-generate zone entries from host configurations

Replace static zone file with dynamically generated records:
- Add homelab.dns module with enable/cnames options
- Extract IPs from systemd.network configs (filters VPN interfaces)
- Use git commit timestamp as zone serial number
- Move external hosts to separate external-hosts.nix

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

hosts/auth01/configuration.nix

@@ -11,6 +11,8 @@
     ../../common/vm
   ];
 
+  homelab.dns.cnames = [ "ldap" ];
+
   nixpkgs.config.allowUnfree = true;
   # Use the systemd-boot EFI boot loader.
   boot.loader.grub = {

hosts/http-proxy/configuration.nix

@@ -11,6 +11,22 @@
     ../../common/vm
   ];
 
+  homelab.dns.cnames = [
+    "nzbget"
+    "radarr"
+    "sonarr"
+    "ha"
+    "z2m"
+    "grafana"
+    "prometheus"
+    "alertmanager"
+    "jelly"
+    "auth"
+    "lldap"
+    "pyroscope"
+    "pushgw"
+  ];
+
   nixpkgs.config.allowUnfree = true;
   # Use the systemd-boot EFI boot loader.
   boot.loader.grub = {

hosts/nix-cache01/configuration.nix

@@ -11,6 +11,8 @@
     ../../common/vm
   ];
 
+  homelab.dns.cnames = [ "nix-cache" "actions1" ];
+
   fileSystems."/nix" = {
     device = "/dev/disk/by-label/nixcache";
     fsType = "xfs";

hosts/template/configuration.nix

@@ -8,6 +8,9 @@
       ../../system
     ];
 
+  # Template host - exclude from DNS zone generation
+  homelab.dns.enable = false;
+
 
   boot.loader.grub.enable = true;
   boot.loader.grub.device = "/dev/sda";

hosts/testvm01/configuration.nix

@@ -13,6 +13,9 @@
     ../../common/vm
   ];
 
+  # Test VM - exclude from DNS zone generation
+  homelab.dns.enable = false;
+
   nixpkgs.config.allowUnfree = true;
   boot.loader.grub.enable = true;
   boot.loader.grub.device = "/dev/vda";

hosts/vault01/configuration.nix

@@ -14,6 +14,8 @@
     ../../services/vault
   ];
 
+  homelab.dns.cnames = [ "vault" ];
+
   nixpkgs.config.allowUnfree = true;
   boot.loader.grub.enable = true;
   boot.loader.grub.device = "/dev/vda";

lib/dns-zone.nix

@@ -0,0 +1,160 @@
+{ lib }:
+let
+  # Pad string on the right to reach a fixed width
+  rightPad = width: str:
+    let
+      len = builtins.stringLength str;
+      padding = if len >= width then "" else lib.strings.replicate (width - len) " ";
+    in
+    str + padding;
+
+  # Extract IP address from CIDR notation (e.g., "10.69.13.5/24" -> "10.69.13.5")
+  extractIP = address:
+    let
+      parts = lib.splitString "/" address;
+    in
+    builtins.head parts;
+
+  # Check if a network interface name looks like a VPN/tunnel interface
+  isVpnInterface = ifaceName:
+    lib.hasPrefix "wg" ifaceName ||
+    lib.hasPrefix "tun" ifaceName ||
+    lib.hasPrefix "tap" ifaceName ||
+    lib.hasPrefix "vti" ifaceName;
+
+  # Extract DNS information from a single host configuration
+  # Returns null if host should not be included in DNS
+  extractHostDNS = name: hostConfig:
+    let
+      cfg = hostConfig.config;
+      # Handle cases where homelab module might not be imported
+      dnsConfig = (cfg.homelab or { }).dns or { enable = true; cnames = [ ]; };
+      hostname = cfg.networking.hostName;
+      networks = cfg.systemd.network.networks or { };
+
+      # Filter out VPN interfaces and find networks with static addresses
+      # Check matchConfig.Name instead of network unit name (which can have prefixes like "40-")
+      physicalNetworks = lib.filterAttrs
+        (netName: netCfg:
+          let
+            ifaceName = netCfg.matchConfig.Name or "";
+          in
+          !(isVpnInterface ifaceName) && (netCfg.address or [ ]) != [ ])
+        networks;
+
+      # Get addresses from physical networks only
+      networkAddresses = lib.flatten (
+        lib.mapAttrsToList
+          (netName: netCfg: netCfg.address or [ ])
+          physicalNetworks
+      );
+
+      # Get the first address, if any
+      firstAddress = if networkAddresses != [ ] then builtins.head networkAddresses else null;
+
+      # Check if host uses DHCP (no static address)
+      usesDHCP = firstAddress == null ||
+        lib.any
+          (netName: (networks.${netName}.networkConfig.DHCP or "no") != "no")
+          (lib.attrNames networks);
+    in
+    if !(dnsConfig.enable or true) || firstAddress == null then
+      null
+    else
+      {
+        inherit hostname;
+        ip = extractIP firstAddress;
+        cnames = dnsConfig.cnames or [ ];
+      };
+
+  # Generate A record line
+  generateARecord = hostname: ip:
+    "${rightPad 20 hostname}IN      A       ${ip}";
+
+  # Generate CNAME record line
+  generateCNAME = alias: target:
+    "${rightPad 20 alias}IN      CNAME   ${target}";
+
+  # Generate zone file from flake configurations and external hosts
+  generateZone =
+    { self
+    , externalHosts
+    , serial
+    , domain ? "home.2rjus.net"
+    , ttl ? 1800
+    , refresh ? 3600
+    , retry ? 900
+    , expire ? 1209600
+    , minTtl ? 120
+    , nameservers ? [ "ns1" "ns2" "ns3" ]
+    , adminEmail ? "admin.test.2rjus.net"
+    }:
+    let
+      # Extract DNS info from all flake hosts
+      nixosConfigs = self.nixosConfigurations or { };
+      hostDNSList = lib.filter (x: x != null) (
+        lib.mapAttrsToList extractHostDNS nixosConfigs
+      );
+
+      # Sort hosts by IP for consistent output
+      sortedHosts = lib.sort (a: b: a.ip < b.ip) hostDNSList;
+
+      # Generate A records for flake hosts
+      flakeARecords = lib.concatMapStringsSep "\n" (host:
+        generateARecord host.hostname host.ip
+      ) sortedHosts;
+
+      # Generate CNAMEs for flake hosts
+      flakeCNAMEs = lib.concatMapStringsSep "\n" (host:
+        lib.concatMapStringsSep "\n" (cname:
+          generateCNAME cname host.hostname
+        ) host.cnames
+      ) (lib.filter (h: h.cnames != [ ]) sortedHosts);
+
+      # Generate A records for external hosts
+      externalARecords = lib.concatStringsSep "\n" (
+        lib.mapAttrsToList (name: ip:
+          generateARecord name ip
+        ) (externalHosts.aRecords or { })
+      );
+
+      # Generate CNAMEs for external hosts
+      externalCNAMEs = lib.concatStringsSep "\n" (
+        lib.mapAttrsToList (alias: target:
+          generateCNAME alias target
+        ) (externalHosts.cnames or { })
+      );
+
+      # NS records
+      nsRecords = lib.concatMapStringsSep "\n" (ns:
+        "                    IN      NS      ${ns}.${domain}."
+      ) nameservers;
+
+      # SOA record
+      soa = ''
+        $ORIGIN ${domain}.
+        $TTL ${toString ttl}
+        @       IN      SOA     ns1.${domain}.      ${adminEmail}. (
+                                ${toString serial}                    ; serial number
+                                ${toString refresh}                    ; refresh
+                                ${toString retry}                     ; retry
+                                ${toString expire}                 ; expire
+                                ${toString minTtl}                     ; ttl
+                                )'';
+    in
+    lib.concatStringsSep "\n\n" (lib.filter (s: s != "") [
+      soa
+      nsRecords
+      "; Flake-managed hosts (auto-generated)"
+      flakeARecords
+      (if flakeCNAMEs != "" then "; Flake-managed CNAMEs\n${flakeCNAMEs}" else "")
+      "; External hosts (not managed by this flake)"
+      externalARecords
+      (if externalCNAMEs != "" then "; External CNAMEs\n${externalCNAMEs}" else "")
+      ""
+    ]);
+
+in
+{
+  inherit extractIP extractHostDNS generateARecord generateCNAME generateZone;
+}

modules/homelab/default.nix

@@ -0,0 +1,6 @@
+{ ... }:
+{
+  imports = [
+    ./dns.nix
+  ];
+}

modules/homelab/dns.nix

@@ -0,0 +1,20 @@
+{ config, lib, ... }:
+let
+  cfg = config.homelab.dns;
+in
+{
+  options.homelab.dns = {
+    enable = lib.mkOption {
+      type = lib.types.bool;
+      default = true;
+      description = "Include this host in DNS zone generation";
+    };
+
+    cnames = lib.mkOption {
+      type = lib.types.listOf lib.types.str;
+      default = [ ];
+      description = "CNAME records pointing to this host";
+      example = [ "web" "api" ];
+    };
+  };
+}

services/ns/external-hosts.nix

@@ -0,0 +1,52 @@
+# DNS records for hosts not managed by this flake
+# These are manually maintained and combined with auto-generated records
+{
+  aRecords = {
+    # 8_k8s
+    "kube-blue1" = "10.69.8.150";
+    "kube-blue2" = "10.69.8.151";
+    "kube-blue3" = "10.69.8.152";
+    "kube-blue4" = "10.69.8.153";
+    "kube-blue5" = "10.69.8.154";
+    "kube-blue6" = "10.69.8.155";
+    "kube-blue7" = "10.69.8.156";
+    "kube-blue8" = "10.69.8.157";
+    "kube-blue9" = "10.69.8.158";
+    "kube-blue10" = "10.69.8.159";
+
+    # 10
+    "gw" = "10.69.10.1";
+
+    # 12_CORE
+    "virt-mini1" = "10.69.12.11";
+    "nas" = "10.69.12.50";
+    "nzbget-jail" = "10.69.12.51";
+    "restic" = "10.69.12.52";
+    "radarr-jail" = "10.69.12.53";
+    "sonarr-jail" = "10.69.12.54";
+    "bazarr" = "10.69.12.55";
+    "mpnzb" = "10.69.12.57";
+    "pve1" = "10.69.12.75";
+    "inc1" = "10.69.12.80";
+    "inc2" = "10.69.12.81";
+
+    # 22_WLAN
+    "unifi-ctrl" = "10.69.22.5";
+
+    # 30
+    "gunter" = "10.69.30.105";
+
+    # 31
+    "media" = "10.69.31.50";
+
+    # 99_MGMT
+    "sw1" = "10.69.99.2";
+    "testing" = "10.69.33.33";
+  };
+
+  cnames = {
+    # k8s services
+    "rook" = "kube-blue4";
+    "git" = "kube-blue5";
+  };
+}

services/ns/master-authorative.nix

@@ -1,4 +1,16 @@
-{ ... }:
+{ self, lib, ... }:
+let
+  dnsLib = import ../../lib/dns-zone.nix { inherit lib; };
+  externalHosts = import ./external-hosts.nix;
+
+  # Generate zone from flake hosts + external hosts
+  # Use lastModified from git commit as serial number
+  zoneData = dnsLib.generateZone {
+    inherit self externalHosts;
+    serial = self.sourceInfo.lastModified;
+    domain = "home.2rjus.net";
+  };
+in
 {
   sops.secrets.ns_xfer_key = {
     path = "/etc/nsd/xfer.key";
@@ -26,7 +38,7 @@
       "home.2rjus.net" = {
         provideXFR = [ "10.69.13.6 xferkey" ];
         notify = [ "10.69.13.6@8053 xferkey" ];
-        data = builtins.readFile ./zones-home-2rjus-net.conf;
+        data = zoneData;
       };
     };
   };

services/ns/secondary-authorative.nix

@@ -1,4 +1,16 @@
-{ ... }:
+{ self, lib, ... }:
+let
+  dnsLib = import ../../lib/dns-zone.nix { inherit lib; };
+  externalHosts = import ./external-hosts.nix;
+
+  # Generate zone from flake hosts + external hosts
+  # Used as initial zone data before first AXFR completes
+  zoneData = dnsLib.generateZone {
+    inherit self externalHosts;
+    serial = self.sourceInfo.lastModified;
+    domain = "home.2rjus.net";
+  };
+in
 {
   sops.secrets.ns_xfer_key = {
     path = "/etc/nsd/xfer.key";
@@ -24,7 +36,7 @@
       "home.2rjus.net" = {
         allowNotify = [ "10.69.13.5 xferkey" ];
         requestXFR = [ "AXFR 10.69.13.5@8053 xferkey" ];
-        data = builtins.readFile ./zones-home-2rjus-net.conf;
+        data = zoneData;
       };
     };
   };

services/ns/zones-home-2rjus-net.conf

@@ -1,99 +0,0 @@
-$ORIGIN home.2rjus.net.
-$TTL 1800
-@       IN      SOA     ns1.home.2rjus.net.      admin.test.2rjus.net. (
-                        2066                    ; serial number
-                        3600                    ; refresh
-                        900                     ; retry
-                        1209600                 ; expire
-                        120                     ; ttl
-                        )
-
-                    IN      NS      ns1.home.2rjus.net.
-                    IN      NS      ns2.home.2rjus.net.
-                    IN      NS      ns3.home.2rjus.net.
-
-; 8_k8s
-kube-blue1          IN      A       10.69.8.150
-kube-blue2          IN      A       10.69.8.151
-kube-blue3          IN      A       10.69.8.152
-
-kube-blue4          IN      A       10.69.8.153
-rook                IN      CNAME   kube-blue4
-
-kube-blue5          IN      A       10.69.8.154
-git                 IN      CNAME   kube-blue5
-
-kube-blue6          IN      A       10.69.8.155
-kube-blue7          IN      A       10.69.8.156
-kube-blue8          IN      A       10.69.8.157
-kube-blue9          IN      A       10.69.8.158
-kube-blue10         IN      A       10.69.8.159
-
-; 10
-gw                  IN      A       10.69.10.1
-
-; 12_CORE
-virt-mini1          IN      A       10.69.12.11
-nas                 IN      A       10.69.12.50
-nzbget-jail         IN      A       10.69.12.51
-restic              IN      A       10.69.12.52
-radarr-jail         IN      A       10.69.12.53
-sonarr-jail         IN      A       10.69.12.54
-bazarr              IN      A       10.69.12.55
-mpnzb               IN      A       10.69.12.57
-pve1                IN      A       10.69.12.75
-inc1                IN      A       10.69.12.80
-inc2                IN      A       10.69.12.81
-media1              IN      A       10.69.12.82
-
-; 13_SVC
-ns1                 IN      A       10.69.13.5
-ns2                 IN      A       10.69.13.6
-ns3                 IN      A       10.69.13.7
-ns4                 IN      A       10.69.13.8
-ha1                 IN      A       10.69.13.9
-nixos-test1         IN      A       10.69.13.10
-http-proxy          IN      A       10.69.13.11
-ca                  IN      A       10.69.13.12
-monitoring01        IN      A       10.69.13.13
-jelly01             IN      A       10.69.13.14
-nix-cache01         IN      A       10.69.13.15
-nix-cache           IN      CNAME   nix-cache01
-actions1            IN      CNAME   nix-cache01
-pgdb1               IN      A       10.69.13.16
-nats1               IN      A       10.69.13.17
-auth01              IN      A       10.69.13.18
-vault01             IN      A       10.69.13.19
-vault               IN      CNAME   vault01
-vaulttest01         IN      A       10.69.13.150
-
-; http-proxy cnames
-nzbget              IN      CNAME   http-proxy
-radarr              IN      CNAME   http-proxy
-sonarr              IN      CNAME   http-proxy
-ha                  IN      CNAME   http-proxy
-z2m                 IN      CNAME   http-proxy
-grafana             IN      CNAME   http-proxy
-prometheus          IN      CNAME   http-proxy
-alertmanager        IN      CNAME   http-proxy
-jelly               IN      CNAME   http-proxy
-auth                IN      CNAME   http-proxy
-lldap               IN      CNAME   http-proxy
-pyroscope           IN      CNAME   http-proxy
-pushgw              IN      CNAME   http-proxy
-
-ldap                IN      CNAME   auth01
-
-
-; 22_WLAN
-unifi-ctrl          IN      A       10.69.22.5
-
-; 30
-gunter              IN      A       10.69.30.105
-
-; 31
-media               IN      A       10.69.31.50
-
-; 99_MGMT
-sw1                 IN      A       10.69.99.2
-testing             IN      A       10.69.33.33

system/default.nix

@@ -11,5 +11,7 @@
     ./sops.nix
     ./sshd.nix
     ./vault-secrets.nix
+
+    ../modules/homelab
   ];
 }