<apex:actionFunction name="callsetSource" action="{!setSource}" rerender='none'>
    <apex:param name='var3' value=''/>
    <apex:param name='var4' value=''/>
</apex:actionFunction>

Nel controller

String var3 = ApexPages.currentPage().getParameters().get('var3');
String var4 = ApexPages.currentPage().getParameters().get('var4');