All of the level packs are currently free for Xbox One, Xbox 360, PS3, PS4, and PC

The packs are
China Rising
Dragon’s Teeth
Final Stand
Naval Strike
Second Assault

PSN Link
https://store.playstation.com/#!/en-us/search/f=%5Ebattlefield%2B4%7Cbucket~games

Xbox (Scroll down for Add ons)
https://www.microsoft.com/en-us/store/p/battlefield-4-premium-ed…

PC/Origin
https://www.origin.com/en-us/store/free-games/on-the-house