Merge pull request 'Add coredns module' (#4837) from coredns into main

Reviewed-on: https://git.clan.lol/clan/clan-core/pulls/4837

clanServices/coredns/README.md

@@ -0,0 +1,68 @@
+This module enables hosting clan-internal services easily, which can be resolved
+inside your VPN. This allows defining a custom top-level domain (e.g. `.clan`)
+and exposing endpoints from a machine to others, which will be
+accessible under `http://<service>.clan` in your browser.
+
+The service consists of two roles:
+
+- A `server` role: This is the DNS-server that will be queried when trying to
+  resolve clan-internal services. It defines the top-level domain.
+- A `default` role: This does two things. First, it sets up the nameservers so
+  thatclan-internal queries are resolved via the `server` machine, while
+  external queries are resolved as normal via DHCP. Second, it allows exposing
+  services (see example below).
+
+## Example Usage
+
+Here the machine `dnsserver` is designated as internal DNS-server for the TLD
+`.foo`. `server01` will host an application that shall be reachable at
+`http://one.foo` and `server02` is going to be reachable at `http://two.foo`.
+`client` is any other machine that is part of the clan but does not host any
+services.
+
+When `client` tries to resolve `http://one.foo`, the DNS query will be
+routed to `dnsserver`, which will answer with `192.168.1.3`. If it tries to
+resolve some external domain (e.g. `https://clan.lol`), the query will not be
+routed to `dnsserver` but resolved as before, via the nameservers advertised by
+DHCP.
+
+```nix
+inventory = {
+
+  machines = {
+    dnsserver = { }; # 192.168.1.2
+    server01 = { };  # 192.168.1.3
+    server02 = { };  # 192.168.1.4
+    client = { };    # 192.168.1.5
+  };
+
+  instances = {
+    coredns = {
+
+      module.name = "@clan/coredns";
+      module.input = "self";
+
+      # Add the default role to all machines, including `client`
+      roles.default.tags.all = { };
+
+      # DNS server
+      roles.server.machines."dnsserver".settings = {
+        ip = "192.168.1.2";
+        tld = "foo";
+      };
+
+      # First service
+      roles.default.machines."server01".settings = {
+        ip = "192.168.1.3";
+        services = [ "one" ];
+      };
+
+      # Second service
+      roles.default.machines."server02".settings = {
+        ip = "192.168.1.4";
+        services = [ "two" ];
+      };
+    };
+  };
+};
+```

clanServices/coredns/default.nix

@@ -0,0 +1,157 @@
+{ ... }:
+{
+  _class = "clan.service";
+  manifest.name = "coredns";
+  manifest.description = "Clan-internal DNS and service exposure";
+  manifest.categories = [ "Network" ];
+  manifest.readme = builtins.readFile ./README.md;
+
+  roles.server = {
+
+    interface =
+      { lib, ... }:
+      {
+        options.tld = lib.mkOption {
+          type = lib.types.str;
+          default = "clan";
+          description = ''
+            Top-level domain for this instance. All services below this will be
+            resolved internally.
+          '';
+        };
+
+        options.ip = lib.mkOption {
+          type = lib.types.str;
+          # TODO: Set a default
+          description = "IP for the DNS to listen on";
+        };
+      };
+
+    perInstance =
+      {
+        roles,
+        settings,
+        ...
+      }:
+      {
+        nixosModule =
+          {
+            lib,
+            pkgs,
+            ...
+          }:
+          {
+
+            networking.firewall.allowedTCPPorts = [ 53 ];
+            networking.firewall.allowedUDPPorts = [ 53 ];
+
+            services.coredns =
+              let
+
+                # Get all service entries for one host
+                hostServiceEntries =
+                  host:
+                  lib.strings.concatStringsSep "\n" (
+                    map (
+                      service: "${service} IN A ${roles.default.machines.${host}.settings.ip}   ; ${host}"
+                    ) roles.default.machines.${host}.settings.services
+                  );
+
+                zonefile = pkgs.writeTextFile {
+                  name = "db.${settings.tld}";
+                  text = ''
+                    $TTL 3600
+                    @   IN SOA  ns.${settings.tld}. admin.${settings.tld}. 1 7200 3600 1209600 3600
+                        IN NS   ns.${settings.tld}.
+                    ns  IN A    ${settings.ip}   ; DNS server
+
+                  ''
+                  + (lib.strings.concatStringsSep "\n" (
+                    map (host: hostServiceEntries host) (lib.attrNames roles.default.machines)
+                  ));
+                };
+
+              in
+              {
+                enable = true;
+                config = ''
+                  . {
+                      forward . 1.1.1.1
+                      cache 30
+                  }
+
+                  ${settings.tld} {
+                      file ${zonefile}
+                  }
+                '';
+              };
+          };
+      };
+  };
+
+  roles.default = {
+    interface =
+      { lib, ... }:
+      {
+        options.services = lib.mkOption {
+          type = lib.types.listOf lib.types.str;
+          default = [ ];
+          description = ''
+            Service endpoints this host exposes (without TLD). Each entry will
+            be resolved to <entry>.<tld> using the configured top-level domain.
+          '';
+        };
+
+        options.ip = lib.mkOption {
+          type = lib.types.str;
+          # TODO: Set a default
+          description = "IP on which the services will listen";
+        };
+      };
+
+    perInstance =
+      { roles, ... }:
+      {
+        nixosModule =
+          { lib, ... }:
+          {
+
+            networking.nameservers = map (m: "127.0.0.1:5353#${roles.server.machines.${m}.settings.tld}") (
+              lib.attrNames roles.server.machines
+            );
+
+            services.resolved.domains = map (m: "~${roles.server.machines.${m}.settings.tld}") (
+              lib.attrNames roles.server.machines
+            );
+
+            services.unbound = {
+              enable = true;
+              settings = {
+                server = {
+                  port = 5353;
+                  verbosity = 2;
+                  interface = [ "127.0.0.1" ];
+                  access-control = [ "127.0.0.0/8 allow" ];
+                  do-not-query-localhost = "no";
+                  domain-insecure = map (m: "${roles.server.machines.${m}.settings.tld}.") (
+                    lib.attrNames roles.server.machines
+                  );
+                };
+
+                # Default: forward everything else to DHCP-provided resolvers
+                forward-zone = [
+                  {
+                    name = ".";
+                    forward-addr = "127.0.0.53@53"; # Forward to systemd-resolved
+                  }
+                ];
+                stub-zone = map (m: {
+                  name = "${roles.server.machines.${m}.settings.tld}.";
+                  stub-addr = "${roles.server.machines.${m}.settings.ip}";
+                }) (lib.attrNames roles.server.machines);
+              };
+            };
+          };
+      };
+  };
+}

clanServices/coredns/flake-module.nix

@@ -0,0 +1,18 @@
+{ lib, ... }:
+let
+  module = lib.modules.importApply ./default.nix { };
+in
+{
+  clan.modules = {
+    coredns = module;
+  };
+  perSystem =
+    { ... }:
+    {
+      clan.nixosTests.coredns = {
+        imports = [ ./tests/vm/default.nix ];
+
+        clan.modules."@clan/coredns" = module;
+      };
+    };
+}

clanServices/coredns/tests/vm/default.nix

@@ -0,0 +1,113 @@
+{
+  ...
+}:
+{
+  name = "coredns";
+
+  clan = {
+    directory = ./.;
+    test.useContainers = true;
+    inventory = {
+
+      machines = {
+        dns = { }; # 192.168.1.2
+        server01 = { }; # 192.168.1.3
+        server02 = { }; # 192.168.1.4
+        client = { }; # 192.168.1.1
+      };
+
+      instances = {
+        coredns = {
+
+          module.name = "@clan/coredns";
+          module.input = "self";
+
+          roles.default.tags.all = { };
+
+          # First service
+          roles.default.machines."server01".settings = {
+            ip = "192.168.1.3";
+            services = [ "one" ];
+          };
+
+          # Second service
+          roles.default.machines."server02".settings = {
+            ip = "192.168.1.4";
+            services = [ "two" ];
+          };
+
+          # DNS server
+          roles.server.machines."dns".settings = {
+            ip = "192.168.1.2";
+            tld = "foo";
+          };
+        };
+      };
+    };
+  };
+
+  nodes = {
+    dns =
+      { pkgs, ... }:
+      {
+        environment.systemPackages = [ pkgs.net-tools ];
+      };
+
+    client =
+      { pkgs, ... }:
+      {
+        environment.systemPackages = [ pkgs.net-tools ];
+      };
+
+    server01 = {
+      services.nginx = {
+        enable = true;
+        virtualHosts."one.foo" = {
+          locations."/" = {
+            return = "200 'test server response one'";
+            extraConfig = "add_header Content-Type text/plain;";
+          };
+        };
+      };
+    };
+    server02 = {
+      services.nginx = {
+        enable = true;
+        virtualHosts."two.foo" = {
+          locations."/" = {
+            return = "200 'test server response two'";
+            extraConfig = "add_header Content-Type text/plain;";
+          };
+        };
+      };
+    };
+  };
+
+  testScript = ''
+    import json
+    start_all()
+
+    machines = [server01, server02, dns, client]
+
+    for m in machines:
+        m.systemctl("start network-online.target")
+
+    for m in machines:
+        m.wait_for_unit("network-online.target")
+
+    # import time
+    # time.sleep(2333333)
+
+    # This should work, but is borken in tests i think? Instead we dig directly
+
+    # client.succeed("curl -k -v http://one.foo")
+    # client.succeed("curl -k -v http://two.foo")
+
+    answer = client.succeed("dig @192.168.1.2 one.foo")
+    assert "192.168.1.3" in answer, "IP not found"
+
+    answer = client.succeed("dig @192.168.1.2 two.foo")
+    assert "192.168.1.4" in answer, "IP not found"
+
+  '';
+}

clanServices/coredns/tests/vm/sops/users/admin/key.json

@@ -0,0 +1,4 @@
+{
+  "publickey": "age1qm0p4vf9jvcnn43s6l4prk8zn6cx0ep9gzvevxecv729xz540v8qa742eg",
+  "type": "age"
+}

docs/mkdocs.yml

@@ -94,6 +94,7 @@ nav:
               - reference/clanServices/index.md
               - reference/clanServices/admin.md
               - reference/clanServices/borgbackup.md
+              - reference/clanServices/coredns.md
               - reference/clanServices/data-mesher.md
               - reference/clanServices/dyndns.md
               - reference/clanServices/emergency-access.md