Dude.
Life is too short to be unhappy, and you are gonna get unhappiness in your life from a*sholes regardless. Sorry it is that way, but it is. So why add to it yourself?
He may be gay, he may be bi.
May even be straight and shy.
Matters not to thee or me,
Hit on him and make Sweet poetry.
And yeah, he knows you are gay. Folk always make me laugh when they try to hide it - you can usually tell rapidly if they are AC, DC or universal sockets, especially if they are good friends.
Just go for it. A guy hitting on another guy is never an insult.
Good luck.
Go for it, cautiously. MM is right. Life is too short, and you deserve to be happy.
One time, many moons ago, a female friend of mine took me to a gay bar to learn how to line dance. I got hit one once - I was flattered, and it was cool but within 2 seconds of talking knew the dude knew I was straight.
I'm with MM here - he probably already knows you're gay.
He knows. Enjoy!