Strictly speaking, from an airline's perspective, you are not allowed to drink your own booze on any flight.
I personally don't see the issue with it as long as you're not being a tool and annoying other folk and/or airline crew.
If you do (not specifically you, but people in general) drink your own booze and start being a bam then people like me get to hear about it day in, day out from their missus who is a hostie and has to deal with people being @rses on flights due to drinking their own booze!
NB Flight crews know the signs to look for - people just buying loads of soft drinks/mixers and no alcohol, and may refuser to serve you so watch out for that.
Good luck!