nixos: iscsi/target: init module

Co-authored-by: Graham Christensen <graham@floxdev.com>

nixos/modules/module-list.nix

@@ -691,6 +691,7 @@
   ./services/networking/iodine.nix
   ./services/networking/iperf3.nix
   ./services/networking/ircd-hybrid/default.nix
+  ./services/networking/iscsi/target.nix
   ./services/networking/iwd.nix
   ./services/networking/jicofo.nix
   ./services/networking/jitsi-videobridge.nix

nixos/modules/services/networking/iscsi/target.nix

@@ -0,0 +1,53 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  cfg = config.services.target;
+in
+{
+  ###### interface
+  options = {
+    services.target = with types; {
+      enable = mkEnableOption "the kernel's LIO iscsi target";
+
+      config = mkOption {
+        type = attrs;
+        default = {};
+        description = ''
+          Content of /etc/target/saveconfig.json
+          This file is normally read and written by targetcli
+        '';
+      };
+    };
+  };
+
+  ###### implementation
+  config = mkIf cfg.enable {
+    environment.etc."target/saveconfig.json" = {
+      text = builtins.toJSON cfg.config;
+      mode = "0600";
+    };
+
+    environment.systemPackages = with pkgs; [ targetcli ];
+
+    boot.kernelModules = [ "configfs" "target_core_mod" "iscsi_target_mod" ];
+
+    systemd.services.iscsi-target = {
+      enable = true;
+      after = [ "network.target" "local-fs.target" ];
+      requires = [ "sys-kernel-config.mount" ];
+      wantedBy = [ "multi-user.target" ];
+      serviceConfig = {
+        Type = "oneshot";
+        ExecStart = "${pkgs.python3.pkgs.rtslib}/bin/targetctl restore";
+        ExecStop = "${pkgs.python3.pkgs.rtslib}/bin/targetctl clear";
+        RemainAfterExit = "yes";
+      };
+    };
+
+    systemd.tmpfiles.rules = [
+      "d /etc/target 0700 root root - -"
+    ];
+  };
+}