applied patch from Thomas Buchanan containing bugfixes and some re-factoring

http://seclists.org/nmap-dev/2010/q4/447

scripts/upnp-info.nse

@@ -6,6 +6,11 @@ Attempts to extract system information from the UPnP service.
 -- @output
 -- |  upnp-info:  System/1.0 UPnP/1.0 IGD/1.0
 -- |_ Location: http://192.168.1.1:80/UPnP/IGD.xml
+--
+-- @args upnp-info.override Controls whether we override the IP address information
+--                          returned by the UPNP service for the location of the XML
+--                          file that describes the device.  Defaults to true for 
+--                          unicast hosts.
 
 -- 2010-10-05 - add prerule support <patrik@cqure.net>
 -- 2010-10-10 - add newtarget support <patrik@cqure.net>
@@ -17,6 +22,7 @@ license = "Same as Nmap--See http://nmap.org/book/man-legal.html"
 
 categories = {"default", "discovery", "safe"}
 
+require("stdnse")
 require("shortport")
 require("upnp")
 
@@ -28,7 +34,13 @@ portrule = shortport.portnumber(1900, "udp", {"open", "open|filtered"})
 -- Sends UPnP discovery packet to host, 
 -- and extracts service information from results
 action = function(host, port)
+	local override = stdnse.get_script_args("upnp-info.override")
 	local helper = upnp.Helper:new( host, port )
+	if ( override ~= nil ) and ( string.lower(override) == "false" ) then
+		helper:setOverride( false )
+	else
+		helper:setOverride( true )
+	end
 	local status, result = helper:queryServices()
 
 	if ( status ) then