A tupperware container is neither bear nor rodent proof (I've had mice gnaw through them). It is not really odor proof, either, It will definitely not be legal if you are backpacking where a bear canister is required. It will also be more difficult to pack a rigid container in your pack than a flexible one, as I found out recently when I did have to use the bear canister.

I personally use an Ursack with an OP sack liner except for the rare occasions in which I'm in bear-canister-required territory. That's partly because the Ursack (if properly fastened) will also keep out birds and rodents, and partly because I can't throw (arthritis) so can't do a bear hang. It's also far easier to pack something flexible, rather than rigid, inside my pack. The same would be true of your dry bag without the tupperware!