Filter dhcp options from various scripts instead of in dhcp.lua

[dmiller-nmap]

dhcp.dhcp_build attempts to enforce a "default" set of DHCP options, increasing to all option if verbosity is set (-v or script selected by name), but this kind of decision should be enforced by the script instead of in the library. This may require exposing the list of "actions" (DHCP options and parsing functions) to scripts.

[h4ck3rk3y]

@dmiller-nmap how about an argument only_defaults, which if set true won't enforce all options even if verbosity is set.

@@ -405,7 +405,7 @@
 --
 --@return status (true or false)
 --@return The parsed response, as a table.
-function dhcp_build(request_type, ip_address, mac_address, options, request_options, overrides, lease_time, transaction_id)
+function dhcp_build(request_type, ip_address, mac_address, options, request_options, overrides, lease_time, transaction_id, only_defaults)
   local packet = strbuf.new()

   -- Set up the default overrides
@@ -417,7 +417,7 @@
     -- Request the defaults, or there's no verbosity; otherwise, request everything!
     request_options = strbuf.new()
     for i,v in pairs(actions) do
-      if(v.default or nmap.verbosity() > 0) then
+      if(v.default or (not only_defaults and nmap.verbosity() > 0) ) then
         request_options = request_options .. string.char(i)
       end
     end
@@ -603,12 +603,12 @@
 --@param lease_time      [optional] The lease time used when requestint an IP. Default: 1 second.
 --@return status (true or false)
 --@return The parsed response, as a table.
-function make_request(target, request_type, ip_address, mac_address, options, request_options, overrides, lease_time)
+function make_request(target, request_type, ip_address, mac_address, options, request_options, overrides, lease_time, only_defaults)
   -- A unique id that identifies this particular session (and lets us filter out what we don't want to see)
   local transaction_id = overrides and overrides['xid'] or bin.pack("<I", math.random(0, 0x7FFFFFFF))

   -- Generate the packet
-  local status, packet = dhcp_build(request_type, bin.pack(">I", ipOps.todword(ip_address)), mac_address, options, request_options, overrides, lease_time, transaction_id)
+  local status, packet = dhcp_build(request_type, bin.pack(">I", ipOps.todword(ip_address)), mac_address, options, request_options, overrides, lease_time, transaction_id, only_defaults)
   if(not(status)) then
     stdnse.debug1("dhcp: Couldn't build packet: " .. packet)
     return false, "Couldn't build packet: "  .. packet