I don't think you can do that.
Try this:
1. Deploy something into same CRM server under ISV folder that will be called by your javascript.
2. Using the one that you just deployed into ISV folder to relay your jquery to "http://外部ip/webservice/getextinfo.php?ext=8017&json=1";
That way, you don't break the CRM security such as cross domain scripting and you get what you want because the access is not from the client side, it's on server
side from your ISV sub folder.