Nix: add shell and test script

run-test

@@ -0,0 +1,6 @@
+#!/usr/bin/env bash
+
+set -eu
+
+sudo ls
+sudo sockdump --format pcap /nix/var/nix/daemon-socket/socket | wireshark -X lua_script:"${PWD}"/nix-packet.lua -k -i -

shell.nix

@@ -0,0 +1,13 @@
+{ pkgs ? import <nixpkgs> {} }:
+let
+  sockdump = pkgs.sockdump.overrideAttrs(old: {
+    src = pkgs.fetchFromGitHub {
+      owner = "NinjaTrappeur";
+      repo = "sockdump";
+      rev = "5a45e06bc73938334de1375127e82d240b1d7477";
+      hash = "sha256-q6jdwFhl2G9o2C0BVU6Xz7xizO00yaSQ2KSR/z4fixY=";
+    };
+  });
+in pkgs.mkShell {
+  nativeBuildInputs = [ sockdump pkgs.wireshark ];
+}