Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

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

- Updated TOE support in the kernel.

- Stateful TCP offload drivers for Terminator 3 and 4 (T3 and T4) ASICs.
These are available as t3_tom and t4_tom modules that augment cxgb(4)
and cxgbe(4) respectively. The cxgb/cxgbe drivers continue to work as
usual with or without these extra features.

- iWARP driver for Terminator 3 ASIC (kernel verbs). T4 iWARP in the
works and will follow soon.

Build-tested with make universe.

30s overview
============
What interfaces support TCP offload? Look for TOE4 and/or TOE6 in the
capabilities of an interface:
# ifconfig -m | grep TOE

Enable/disable TCP offload on an interface (just like any other ifnet
capability):
# ifconfig cxgbe0 toe
# ifconfig cxgbe0 -toe

Which connections are offloaded? Look for toe4 and/or toe6 in the
output of netstat and sockstat:
# netstat -np tcp | grep toe
# sockstat -46c | grep toe

Reviewed by: bz, gnn
Sponsored by: Chelsio communications.
MFC after: ~3 months (after 9.1, and after ensuring MFC is feasible)

Fix typos - remove duplicate "the".

PR: bin/154928
Submitted by: Eitan Adler <lists at eitanadler.com>
MFC after: 3 days

Replace struct tcpopt with a proxy toeopt struct in the TOE driver interface to
the TCP syncache. This returns struct tcpopt to being private within the TCP
implementation, thus allowing it to be modified without ABI concerns.

The patch breaks the ABI. Bump __FreeBSD_version to 800103 accordingly. The cxgb
driver is the only TOE consumer affected by this change, and needs to be
recompiled along with the kernel.

Suggested by: rwatson
Reviewed by: rwatson, kmacy
Approved by: re (kensmith), kensmith (mentor temporarily unavailable)

- Switch to INP_WLOCK macro from inp_wlock
- calling sodisconnect after tcp_twstart is both gratuitous and unsafe - remove

Submitted by: rwatson

Add versions of tcp_twstart, tcp_close, and tcp_drop that hide the acquisition the tcbinfo lock.

MFC after: 1 week

move cxgb_lt2.[ch] from NIC to TOE
move most offload functionality from NIC to TOE
factor out all socket and inpcb direct access
factor out access to locking in incpb, pcbinfo, and sockbuf

Incorporate TCP offload hooks in to core TCP code.
- Rename output routines tcp_gen_* -> tcp_output_*.
- Rename notification routines that turn in to no-ops in the absence of TOE
from tcp_gen_* -> tcp_offload_*.
- Fix some minor comment nits.
- Add a /* FALLTHROUGH */

Reviewed by: Sam Leffler, Robert Watson, and Mike Silbersack

incorporate feedback since initial commit
- rename tcp_ofld.[ch] to tcp_offload.[ch]
- document usage and locking conventions of the functions in the
toe_usrreqs function vector
- document tcpcb, inpcb, and socket fields used by toe
- widen the listen interface into 2 functions
- rename DISABLE_TCP_OFFLOAD to TCP_OFFLOAD_DISABLE
- shrink conditional compilation to reduce the likelihood of bitrot
- replace sc->sc_toepcb checks in tcp_syncache.c with TOEPCB_ISSET