Initial scaffolding and layout

Set up the modules of the flake. At this time, the flake is split into
modules and machines. Considering that additional top-level sections --
such as packages and shells -- will also be added, it might make sense
to keep all nix related things in one top-level directory, alongside the
flake.nix file.

This is all under the assumption that later amendments to the project
will introduce other tech, such as terraform.

1 files changed, 69 insertions, 0 deletions

diff --git a/modules/xnet/net/default.nix b/modules/xnet/net/default.nix
new file mode 100644
index 0000000..143f189
--- /dev/null
+++ b/modules/xnet/net/default.nix
@@ -0,0 +1,69 @@
+{ config, lib, ... }:
+let
+  cfg = config.xnet.net;
+  inherit (lib) mkOption mkIf types;
+  prefix = "10.26.4";
+in
+{
+  options.xnet.net = {
+    interface = mkOption {
+      type = types.str;
+      default = "";
+      description = "Network interface connecting to xnet.";
+    };
+
+    addr = mkOption {
+      type = types.ints.between 0 255;
+      description = "Final octet for xnet address.";
+      example = 4;
+    };
+
+    sshd = mkOption {
+      type = types.bool;
+      default = false;
+      description = "Enable hardened SSH service.";
+    };
+  };
+
+  # TODO:
+  #   - Add assertion that each address is only used once across config
+  #   - Add each host to each other hosts dns configuration
+  config = mkIf (builtins.stringLength cfg.interface > 0) {
+    networking.vlans = {
+      "${cfg.interface}.4" = {
+        inherit (cfg) interface;
+        id = 4;
+      };
+    };
+
+    networking.interfaces = {
+      "${cfg.interface}.4".ipv4.addresses = [{
+        address = "${prefix}.${toString cfg.addr}";
+        prefixLength = 24;
+      }];
+    };
+
+    services.openssh = {
+      enable = cfg.sshd;
+      startWhenNeeded = true;
+      settings = {
+        X11Forwarding = false;
+        UsePAM = false;
+        PermitRootLogin = "prohibit-password";
+      };
+      extraConfig =
+        let
+          p = [
+            "sk-ssh-ed25519-cert-v01@openssh.com"
+            "ssh-ed25519-cert-v01@openssh.com"
+            "ssh-ed25519"
+          ];
+        in
+        "PubkeyAcceptedKeyTypes ${lib.strings.concatStringsSep "," p}";
+      hostKeys = [{
+        path = "/certs/ssh/ssh_host_ed25519_key";
+        type = "ed25519";
+      }];
+    };
+  };
+}