Accept response from a valid URL

I am using asp.net C# and  MVC5 

 

I have a Scenario Where I need to accept values posted from a specific URL only if any other url post the request to the same url our Action should reject .

 

 

Suppose In a case of Payment Gateway The payemnet gatway post a response to our site url where we accept the values and proces the response.

 

I want to accept the Request form a specified URL e.g.

 

www.ccavenue.com 

 

If Any other domain post the data on mysite.com/response it should reject the request after detecting.

 

How can we achieve the same