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

Merge r254336 from user/np/cxl_tuning.

Add a last-modified timestamp to each LRO entry and provide an interface
to flush all inactive entries. Drivers decide when to flush and what
the inactivity threshold should be.

Network drivers that process an rx queue to completion can enter a
livelock type situation when the rate at which packets are received
reaches equilibrium with the rate at which the rx thread is processing
them. When this happens the final LRO flush (normally when the rx
routine is done) does not occur. Pure ACKs and segments with total
payload < 64K can get stuck in an LRO entry. Symptoms are that TCP
tx-mostly connections' performance falls off a cliff during heavy,
unrelated rx on the interface.

Flushing only inactive LRO entries works better than any of these
alternates that I tried:
- don't LRO pure ACKs
- flush _all_ LRO entries periodically (every 'x' microseconds or every
'y' descriptors)
- stop rx processing in the driver periodically and schedule remaining
work for later.

Reviewed by: andre

MFp4 bz_ipv6_fast:

Significantly update tcp_lro for mostly two things:
1) introduce basic support for IPv6 without extension headers.
2) try hard to also get the incremental checksum updates right,
especially also in the IPv4 case for the IP and TCP header.

Move variables around for better locality, factor things out into
functions, allow checksum updates to be compiled out, ...

Leave a few comments on further things to look at in the future,
though that is not the full list.

Update drivers with appropriate #includes as needed for IPv6 data
type in LRO.

Sponsored by: The FreeBSD Foundation
Sponsored by: iXsystems

Reviewed by: gnn (as part of the whole)
MFC After: 3 days

Switch to a standard 2 clause BSD license (from bsd-style-copyright).

Approved by: Myricom Inc. (gallatin)
Approved by: Intel Corporation (jfv)

Trim extra spaces before tabs.

Add generic TCP LOR into netinet