Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

various connections to last commit

small cleanup of the code, and add support for running multiple
threads on each socket.

Oops, if we want to check from 0 to nsock, the test condition should be
< nsock, not >.

Pointy hat to: cognet
Submitted by: Olivier Cochard-Labbe <olivier AT cochard doT me>

Add IPv6 support to netblast/netsend/netreceive

PR: bin/161368
Submitted by: Olivier Cochard-Labbe <olivier AT cochard doT me>

Set default socket size for netreceive to 128k to reduce the chances
of the buffer overflowing before netreceive can be scheduled to read
the packets from the socket.

Add netrate (netreceive, netsend), a tool for generating (and sinking)
UDP packets of specified size at a fixed rate. I've been using this for
netperf-related testing.