Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

MFC r247104:
Fix tcp_lro_rx_ipv4() for drivers that do not set CSUM_IP_CHECKED.
Specifcially, in_cksum_hdr() returns 0 (not 0xffff) when the IPv4
checksum is correct. Without this fix, the tcp_lro code will reject
good IPv4 traffic from drivers that do not implement IPv4 header
harder csum offload.

MFC r236093:

Trim the extra $FreeBSD$ from the comment below the license. We use
the __FBSDID() macro on the file now instead.

Approved by: re

MFC r235981,236394

In case forwarding is turned on for a given address family, refuse to
queue the packet for LRO and tell the driver to directly pass it on.
This avoids re-assembly and later re-fragmentation problems when
forwarding.

It's not the best solution but the simplest and most effective for
the moment.

Make TCP LRO work properly with VIMAGE kernels rather than just panicing.
There's no VIMAGE context set there yet as this is before if_ethersubr.c.

Approved by: re

MFC r235944:

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.

Approved by: re

MFC r235474:

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

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

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Don't allow lro->len to exceed 65535, as this will result in overflow
when len is inserted back into the synthetic IP packet and cause a
multiple of 2^16 bytes of TCP "packet loss".

This improves Linux->FreeBSD netperf bandwidth by a factor of 300 in
testing on Amazon EC2.

Reviewed by: jfv
MFC after: 2 weeks

Port of the LRO fix from mxge driver to the generic
LRO code. Thanks to Andrew Gallatin for the change.

MFC after: 7 days

Trim extra spaces before tabs.

Don't calculate checksum if it has already been validated

Obtained from: Chelsio Inc.
MFC after: 3 days

Add generic TCP LOR into netinet