The rules have changed since our last cruise in December. NOW, you are limited to ONE bottle per person. Before the quantity was unspecified. Here is the exact wording along with the link to Carnival's site. Don't worry about that corkage fee for wine you consume in your cabin.
Bringing Alcohol On Board - Embarkation
Guests are prohibited from bringing alcoholic and non-alcoholic beverages onboard. However, guests (21 years and older only) may bring one bottle of wine or champagne per person on board only during embarkation at the beginning of the cruise. A $10 corkage fee per bottle will be charged should you wish to consume this wine in the dining room or a $14 corkage fee per bottle in the Supper Club.
Any additional quantity of wine/champagne or any alcoholic and non-alcoholic beverages will be confiscated and discarded without compensation. Guests may purchase a variety of beverages on board the ship. Alcoholic beverages will not be sold or served to anyone under the age of 21. We reserve the right to refuse the sale of alcoholic beverages to anyone. Alcoholic beverages purchased in the ship’s gift shops or in ports of call will be retained by Carnival until the end of the voyage.