How to not keep tcp connections alive after they're done

[Ryan Westlund]

I'm working on a project that runs a webserver from inside a freebsd jail.
If I try to stop the jail shortly after a user logs in (which uses their
google account), the jail stops, but fails to unmount the filesystem with
"device busy". We think it's caused by the kernel keeping alive the
connections to google's server after they're done. If I wait about 90
seconds after the login, I can unmount the file system successfully. But is
there a way to make the kernel drop these connections after they're done?