Visa processing time in Canada

Hello I am travelling to China April 11th. However I will also be travelling abroad in other countries prior to that trip and therefore I can only apply for my entry permit when I return to Canada on March 23. Will this be enough time to get it? I live in New Brunswick so I will have to apply by mail. I am worried I won't have the entry permit in time since there are less than 12 business days that I am back in Canada.