John Mellencamp -- Teenage Sons Charged for Brutal Porch Attack

John Mellencamp's 2 teenage sons have been charged with felony battery in Bloomington, Indiana after allegedly beating the crap out of a 19-year-old man who was sitting on his own front porch.

According to police, the Mellencamps -- 18-year-old Speck and 19-year-old Hud -- rolled up to the victim's home on July 29, accompanied by a 3rd man ... Ty Smith (son of Indiana University baseball coach Tracy Smith.)

Cops say the trio calmly approached the victim ... and unloaded a ferocious beatdown -- with all 3 men kicking, punching and stomping on the unsuspecting porch-dweller.

Eventually, cops say, the victim's roomates heard the attack -- and raced to the scene to break up the fight ... but the damage was already done.

Cops say the victim suffered facial fractures and cuts that required stitches.

According to the Herald Times, the Mellencamps told cops the attack was a response to an incident that took place at a party earlier that night.

Cops say Speck claims he had been trying to break up a fight between two girls who were arguing over him ... when he was pushed and hit by another man. It's unclear if the "pusher" and the victim are the same person.

FYI -- According to the Herald Times, Hud is a trained boxer.

Officials say the Mellencamps and Smith were all charged with felony battery -- and the Mellencamps have already made arrangements to turn themselves in to police.