MFC 304202
tcp/lro: Make # of LRO entries tunable

Reviewed by: hps, gallatin
Obtained from: rrs, gallatin
Sponsored by: Netflix (rrs, gallatin), Microsoft (sephe)
Differential Revision: https://reviews.freebsd.org/D7499

MFC 303766
tcp/lro: If timestamps mismatch or it's a FIN, force flush.

This keeps the segments/ACK/FIN delivery order.

Before this patch, it was observed: if A sent FIN immediately after
an ACK, B would deliver FIN first to the TCP stack, then the ACK.
This out-of-order delivery causes one unnecessary ACK sent from B.

Reviewed by: gallatin, hps
Obtained from: rrs, gallatin
Sponsored by: Netflix (rrs, gallatin), Microsoft (sephe)
Differential Revision: https://reviews.freebsd.org/D7415

MFC 298696,298730

298696
tcp/lro: Fix typo.

MFC after: 1 week
Sponsored by: Microsoft OSTC

298730
tcp/lro: Fix more typo

Noticed by: hiren
MFC after: 1 week
Sponsored by: Microsoft OSTC

MFC 297265

tcp/lro: Return TCP_LRO_NO_ENTRIES if we are short of LRO entries.

So that callers could react accordingly.

Reviewed by: gallatin (no objection)
MFC after: 1 week
Sponsored by: Microsoft OSTC
Differential Revision: https://reviews.freebsd.org/D5695

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

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.

Sponsored by: Myricom Inc.

MFC after: 7 days

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.

MFC after: 3 days
X-MFC with: r235981

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

MFC after: 3 days

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.

Should have been done: ages ago
Discussed with and by: many
MFC after: 3 days

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)

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