Merge r204809 from head to stable/8:

Merge r204809 from head to stable/8:

  Add a comment to tcp_usr_accept() to indicate why it is we acquire the
  tcbinfo lock there: r175612, which re-added it, masked a race between
  sonewconn(2) and accept(2) that could allow an incompletely initialized
  address on a newly-created socket on a listen queue to be exposed.  Full
  details can be found in that commit message.

  Sponsored by:	Juniper Networks

Approved by:	re (bz)

git-svn-id: svn://svn.freebsd.org/base/stable/8@208700 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f