Don't
Just don't redirect users.
If a user is coming from Persia and wanna see EN version he won't be able to?
As Google says: "let user chooses". They did a very good article about the good way to design a homepage for international users: http://googlewebmastercentral.blogspot.fr/2014/05/creating-right-homepage-for-your.html
Moreover, redirect based on IP is dangerous. Google does not have spiders in whole countries in the world so he might not see the different behaviors.
If you really have to : 302 redirect
(client force you to do it or you just do not understand users hate to be redirected or ...)
Use a HTTP 302 status to redirect.
Why ?
Because 302 means both URLs exist. Thus Google will keep both URL indexed.