It's normal, but not necessarily something thee dog will grow out of or that you should tolerate. Barking is self rewarding, so it can be a hard habit to train.
Don't tell him off and definitely don't shout at him, the chances are he will just believe you are joining in with his really fun game of saying hello really loudly to the new dogs/people, so it would only make him worse anyway.
There are a couple of ways to train this. One is to put 'speak' on command and then never use the command. To do this, get a clicker, wait for the dog to bark, click - treat. Once he is barking to get a click i.e he understands what you are doing, add the cue speak as soon as he starts to bark, click-treat. After a few goes he should bark when you say "Speak". To teach "Quiet" give the speak cue, wait for him to stop, click-treat. Continue as you did with speak until he is "quiet" on cue.
Another way would be to remove the fun as soon as he starts barking, so he can longer see it as something rewarding. If he starts barking to get to another dog, turn on your heel and walk away, once he stops barking turn around again. Repeat until he learns that barking stops the fun stuff happening. The same when he does it while people are petting him. Take him away straight away. Don't worry about appearing to be rude, you can always go back and explain once he has stopped barking.
I'd use both methods together if I was training this. Good luck with that and puppy classes 