I'm speaking of "A Quick One While He's Away" and it's a cover of the classic Who track from the 1966 album of the same name. Green Day recorded the cover during 2009's 21st Century Breakdown sessions. This is only one of the four covers the band released via iTunes along with 21st Century Breakdown.
Funny story relating to those covers the band recorded. When fellow GDA team member, Jimmy and I were in New York City two years ago to see American Idiot: The Musical, we met Billie Joe at a bar afterwards and the band's cover of Bob Dylan's "Like A Rolling Stone" played. Billie Joe noticed the song and asked, "Is this us?" We laughed and replied with a confirmation. Billie Joe then said, "I don't even remember us recording this." So I wonder if he remembers recording "A Quick One?" Must have since the band played it live in New York City back in 2009.