nixos/tcpdump: init

(cherry picked from commit eb42ef0c24)

nixos/modules/programs/tcpdump.nix

@@ -0,0 +1,30 @@
+{ config, lib, pkgs, ... }:
+
+let
+  cfg = config.programs.tcpdump;
+in {
+  options = {
+    programs.tcpdump = {
+      enable = lib.mkOption {
+        type = lib.types.bool;
+        default = false;
+        description = ''
+          Whether to configure a setcap wrapper for tcpdump.
+          To use it, add your user to the `pcap` group.
+        '';
+      };
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+    security.wrappers.tcpdump = {
+      owner = "root";
+      group = "pcap";
+      capabilities = "cap_net_raw+p";
+      permissions = "u+rx,g+x";
+      source = lib.getExe pkgs.tcpdump;
+    };
+
+    users.groups.pcap = { };
+  };
+}