nixos/getaddrinfo: init (#413986)

nixos/doc/manual/release-notes/rl-2511.section.md

@@ -17,6 +17,8 @@
 
 - [FileBrowser](https://filebrowser.org/), a web application for managing and sharing files. Available as [services.filebrowser](#opt-services.filebrowser.enable).
 
+- Options under [networking.getaddrinfo](#opt-networking.getaddrinfo.enable) are now allowed to declaratively configure address selection and sorting behavior of `getaddrinfo` in dual-stack networks.
+
 - [LACT](https://github.com/ilya-zlobintsev/LACT), a GPU monitoring and configuration tool, can now be enabled through [services.lact.enable](#opt-services.lact.enable).
   Note that for LACT to work properly on AMD GPU systems, you need to enable [hardware.amdgpu.overdrive.enable](#opt-hardware.amdgpu.overdrive.enable).
 

nixos/modules/config/getaddrinfo.nix

@@ -0,0 +1,120 @@
+{
+  pkgs,
+  lib,
+  config,
+  ...
+}:
+let
+  cfg = config.networking.getaddrinfo;
+
+  formatTableEntries =
+    tableName: table:
+    if table == null then
+      [ ]
+    else
+      lib.mapAttrsToList (cidr: val: "${tableName} ${cidr} ${toString val}") table;
+
+  gaiConfText = lib.concatStringsSep "\n" (
+    [
+      "# Generated by NixOS module networking.getaddrinfo"
+      "# Do not edit manually!"
+      "reload ${if cfg.reload then "yes" else "no"}"
+    ]
+    ++ formatTableEntries "label" cfg.label
+    ++ formatTableEntries "precedence" cfg.precedence
+    ++ formatTableEntries "scopev4" cfg.scopev4
+  );
+in
+{
+  options.networking.getaddrinfo = {
+    enable = lib.mkOption {
+      type = lib.types.bool;
+      default = pkgs.stdenv.hostPlatform.libc == "glibc";
+      defaultText = lib.literalExpression ''
+        pkgs.stdenv.hostPlatform.libc == "glibc"
+      '';
+      description = ''
+        Enables custom address sorting configuration for {manpage}`getaddrinfo(3)` according to RFC 3484.
+
+        This option generates a {file}`/etc/gai.conf` file to override the default address sorting tables,
+        as described in {manpage}`gai.conf(5)`.
+
+        This setting is only applicable when using the GNU C Library (glibc).
+        It has no effect with other libc implementations.
+      '';
+    };
+
+    reload = lib.mkOption {
+      type = lib.types.bool;
+      default = false;
+      description = ''
+        Determines whether a process should detect changes to the configuration file since it was last read.
+
+        If enabled, the file is re-read automatically. This may cause issues in multithreaded applications
+        and is generally discouraged.
+      '';
+    };
+
+    label = lib.mkOption {
+      type = lib.types.nullOr (lib.types.attrsOf lib.types.int);
+      default = null;
+      description = ''
+        Adds entries to the label table, as described in section 2.1 of RFC 3484.
+
+        If any label entries are provided, the glibc’s default label table is ignored.
+      '';
+      example = {
+        "::/0" = 1;
+        "2002::/16" = 2;
+        "::/96" = 3;
+        "::ffff:0:0/96" = 4;
+        "fec0::/10" = 5;
+        "fc00::/7" = 6;
+        "2001:0::/32" = 7;
+      };
+    };
+
+    precedence = lib.mkOption {
+      type = lib.types.nullOr (lib.types.attrsOf lib.types.int);
+      default = null;
+      description = ''
+        Similar to {option}`networking.getaddrinfo.label`, but this option
+        defines entries for the precedence table instead.
+
+        See sections 2.1 and 10.3 of RFC 3484 for details.
+
+        Providing any value will disable the glibc's default precedence table.
+      '';
+      example = {
+        "::1/128" = 50;
+        "::/0" = 40;
+        "2002::/16" = 30;
+        "::/96" = 20;
+        "::ffff:0:0/96" = 10;
+      };
+    };
+
+    scopev4 = lib.mkOption {
+      type = lib.types.nullOr (lib.types.attrsOf lib.types.int);
+      default = null;
+      description = ''
+        Adds custom rules to the IPv4 scope table.
+
+        By default, the scope IDs described in section 3.2 of RFC 6724 are used.
+
+        Modifying these values is rarely necessary.
+      '';
+      example = {
+        "::ffff:169.254.0.0/112" = 2;
+        "::ffff:127.0.0.0/104" = 2;
+        "::ffff:0.0.0.0/96" = 14;
+      };
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+    environment.etc."gai.conf".text = gaiConfText;
+  };
+
+  meta.maintainers = with lib.maintainers; [ moraxyc ];
+}

nixos/modules/module-list.nix

@@ -8,6 +8,7 @@
   ./config/fonts/fontdir.nix
   ./config/fonts/ghostscript.nix
   ./config/fonts/packages.nix
+  ./config/getaddrinfo.nix
   ./config/gtk/gtk-icon-cache.nix
   ./config/i18n.nix
   ./config/iproute2.nix

nixos/tests/all-tests.nix

@@ -537,6 +537,7 @@ in
   gancio = runTest ./gancio.nix;
   garage = handleTest ./garage { };
   gatus = runTest ./gatus.nix;
+  getaddrinfo = runTest ./getaddrinfo.nix;
   gemstash = handleTest ./gemstash.nix { };
   geoclue2 = runTest ./geoclue2.nix;
   geoserver = runTest ./geoserver.nix;

nixos/tests/getaddrinfo.nix

@@ -0,0 +1,68 @@
+{ lib, ... }:
+let
+  ip4 = "192.0.2.1";
+  ip6 = "2001:db8::1";
+
+  precedence = {
+    "::1/128" = 50;
+    "::/0" = 40;
+    "2002::/16" = 30;
+    "::/96" = 20;
+    "::ffff:0:0/96" = 100;
+  };
+in
+{
+  name = "getaddrinfo";
+  meta.maintainers = with lib.maintainers; [ moraxyc ];
+
+  nodes.server = _: {
+    networking.firewall.enable = false;
+    networking.useDHCP = false;
+
+    services.dnsmasq = {
+      enable = true;
+      settings = {
+        address = [
+          "/nixos.test/${ip4}"
+          "/nixos.test/${ip6}"
+        ];
+      };
+    };
+  };
+
+  nodes.client =
+    { pkgs, nodes, ... }:
+    {
+      networking.nameservers = [
+        (lib.head nodes.server.networking.interfaces.eth1.ipv4.addresses).address
+      ];
+      networking.getaddrinfo = {
+        reload = true;
+        inherit precedence;
+      };
+      networking.useDHCP = false;
+      environment.systemPackages = [
+        (pkgs.writers.writePython3Bin "request-addr" { } ''
+          import socket
+
+          results = socket.getaddrinfo("nixos.test", None)
+          print(results[0][4][0])
+        '')
+      ];
+    };
+
+  testScript =
+    { ... }:
+    ''
+      server.wait_for_unit("dnsmasq.service")
+      client.wait_for_unit("network.target")
+
+      assert "${ip4}" in client.succeed("request-addr")
+
+      client.succeed("""
+        sed 's/100/10/' /etc/gai.conf > /etc/gai.conf.new && \
+        mv /etc/gai.conf.new /etc/gai.conf
+      """)
+      assert "${ip6}" in client.succeed("request-addr")
+    '';
+}