Index: nmap.cc
===================================================================
--- nmap.cc	(revision 16019)
+++ nmap.cc	(working copy)
@@ -253,6 +253,7 @@
 	   "  --script-args=<n1=v1,[n2=v2,...]>: provide arguments to scripts\n"
        "  --script-trace: Show all data sent and received\n"
        "  --script-updatedb: Update the script database.\n"
+       "  --script-autoadd: Automatically add missing dependencies to run"
 #endif
        "OS DETECTION:\n"
        "  -O: Enable OS detection\n"
@@ -711,6 +712,8 @@
       {"script_updatedb", no_argument, 0, 0},
       {"script-args",required_argument,0,0},
       {"script_args",required_argument,0,0},
+      {"script-autoadd",no_argument,0,0},
+      {"script_autoadd",no_argument,0,0},
 #endif
       {"ip_options", required_argument, 0, 0},
       {"ip-options", required_argument, 0, 0},
@@ -756,6 +759,8 @@
               o.scripttrace = 1;
       } else if (optcmp(long_options[option_index].name, "script-updatedb") == 0){
               o.scriptupdatedb = 1;
+      } else if (optcmp(long_options[option_index].name, "script-autoadd") == 0){
+              o.scriptautoadd = 1;
       } else
 #endif
       if (optcmp(long_options[option_index].name, "max-os-tries") == 0) {
Index: NmapOps.cc
===================================================================
--- NmapOps.cc	(revision 16019)
+++ NmapOps.cc	(working copy)
@@ -305,6 +305,7 @@
   scriptversion = 0;
   scripttrace = 0;
   scriptupdatedb = 0;
+  scriptautoadd = 0;
 #endif
   memset(&sourcesock, 0, sizeof(sourcesock));
   sourcesocklen = 0;
Index: nse_main.cc
===================================================================
--- nse_main.cc	(revision 16019)
+++ nse_main.cc	(working copy)
@@ -236,6 +236,8 @@
   lua_setfield(L, -2, "default");
   lua_pushboolean(L, o.scriptversion == 1);
   lua_setfield(L, -2, "scriptversion");
+  lua_pushboolean(L, o.scriptautoadd == 1);
+  lua_setfield(L, -2, "scriptautoadd");
   lua_pushliteral(L, SCRIPT_ENGINE_LUA_DIR SCRIPT_ENGINE_DATABASE);
   lua_setfield(L, -2, "script_dbpath");
   lua_pushstring(L, o.scriptargs);
Index: NmapOps.h
===================================================================
--- NmapOps.h	(revision 16019)
+++ NmapOps.h	(working copy)
@@ -327,6 +327,7 @@
   int scriptversion;
   int scripttrace;
   int scriptupdatedb;
+  int scriptautoadd;
   void chooseScripts(char* argument);
   std::vector<std::string> chosenScripts;
 #endif
Index: nse_main.lua
===================================================================
--- nse_main.lua	(revision 16019)
+++ nse_main.lua	(working copy)
@@ -66,6 +66,8 @@
 
 local traceback = debug.traceback;
 
+local max = math.max;
+
 local byte = string.byte;
 local find = string.find;
 local format = string.format;
@@ -74,6 +76,7 @@
 local match = string.match;
 local sub = string.sub;
 
+local concat = table.concat;
 local insert = table.insert;
 local remove = table.remove;
 local sort = table.sort;
@@ -202,7 +205,6 @@
     if not self[rule] then return nil end -- No rule for this script?
     local file_closure = self.file_closure;
     local env = setmetatable({
-        runlevel = 1,
         filename = self.filename,
       }, {__index = _G});
     setfenv(file_closure, env);
@@ -224,7 +226,6 @@
       local thread = setmetatable({
         co = co,
         env = env,
-        runlevel = tonumber(rawget(env, "runlevel")) or 1,
         identifier = tostring(co),
         info = format("'%s' (%s)", self.short_basename, tostring(co));
         type = rule == "hostrule" and "host" or "port",
@@ -246,6 +247,8 @@
     description = "string",
     action = "function",
     categories = "table",
+    dependencies = "table",
+    weak_dependencies = "table",
   };
   -- script = Script.new(filename)
   -- Creates a new Script Class for the script.
@@ -264,7 +267,8 @@
     -- Give the closure its own environment, with global access
     local env = setmetatable({
       filename = filename,
-      runlevel = 1,
+      dependencies = {},
+      weak_dependencies = {},
     }, {__index = _G});
     setfenv(file_closure, env);
     local co = create(file_closure); -- Create a garbage thread
@@ -288,6 +292,16 @@
       assert(type(category) == "string", 
         filename.." has non-string entries in the 'categories' array");
     end
+    -- Assert that dependencies is an array of strings
+    for i, dependency in ipairs(rawget(env, "dependencies")) do
+      assert(type(dependency) == "string", 
+        filename.." has non-string entries in the 'dependencies' array");
+    end
+    -- Assert that weak_dependencies is an array of strings
+    for i, dependency in ipairs(rawget(env, "weak_dependencies")) do
+      assert(type(dependency) == "string", 
+        filename.." has non-string entries in the 'weak_dependencies' array");
+    end
     -- Return the script
     return setmetatable({
       filename = filename,
@@ -303,7 +317,8 @@
       categories = rawget(env, "categories"),
       author = rawget(env, "author"),
       license = rawget(env, "license"),
-      runlevel = tonumber(rawget(env, "runlevel")) or 1,
+      dependencies = rawget(env, "dependencies"),
+      weak_dependencies = rawget(env, "weak_dependencies"),
       threads = {},
       selected_by_name = false,
     }, {__index = Script, __metatable = Script});
@@ -468,6 +483,69 @@
       end
     end
   end
+
+  -- calculate runlevels
+  local name_script = {};
+  for i, script in ipairs(chosen_scripts) do
+    assert(name_script[script.short_basename] == nil);
+    name_script[script.short_basename] = script;
+  end
+  local chain = {}; -- chain of script names
+  setmetatable(name_script, {
+    __index = function (t, k)
+      chain[#chain+1] = k;
+      if cnse.scriptautoadd then
+        local t, path = cnse.fetchfile_absolute(k);
+        if t == nil then -- omitted extension?
+          t, path = cnse.fetchfile_absolute(k..".nse");
+        end
+        if t == "file" then
+          local script = Script.new(path);
+          chosen_scripts[#chosen_scripts+1] = script;
+          name_script[script.short_basename] = script;
+          print_verbose(1,
+              "Script dependency '%s' in chain `%s` added automatically.",
+              script.filename, concat(chain, "->"));
+          chain[#chain] = nil;
+          return script;
+        else
+          error("could not locate script dependency in chain `"..
+              concat(chain, "->").."`");
+        end
+      else
+        error("missing dependency in chain `"..concat(chain, "->").."`\n"..
+            "(use --script-autoadd to automatically add missing dependencies)");
+      end
+    end
+  });
+  local function calculate_runlevel (script)
+    chain[#chain+1] = script.short_basename;
+    if script.runlevel == false then -- circular dependency 
+      error("circular dependency in chain `"..concat(chain, "->").."`");
+    else
+      script.runlevel = false; -- placeholder
+    end
+    local runlevel = 1;
+    for i, dependency in ipairs(script.dependencies) do
+      local s = name_script[dependency];
+      local r = tonumber(s.runlevel) or calculate_runlevel(s);
+      runlevel = max(runlevel, r+1);
+    end
+    for i, weak_dependency in ipairs(script.weak_dependencies) do
+      local s = rawget(name_script, weak_dependency);
+      if s then
+        local r = tonumber(s.runlevel) or calculate_runlevel(s);
+        runlevel = max(runlevel, r+1);
+      end
+    end
+    chain[#chain] = nil;
+    script.runlevel = runlevel;
+    return runlevel;
+  end
+  for i, script in ipairs(chosen_scripts) do
+    local _ = script.runlevel or calculate_runlevel(script);
+  end
+
   return chosen_scripts;
 end
 
@@ -743,7 +821,8 @@
 
   sort(runlevels);
   for i, runlevel in ipairs(runlevels) do
-    print_verbose(1, "Starting runlevel %g scan", runlevel);
+    print_verbose(1, "Starting runlevel %u (of %u) scan.", runlevel,
+        #runlevels);
     run(threads[runlevel]);
   end