inpcb: remove unused KPIs to manipulate inpcbs

These KPIs were added in 9d29c635daa69 and through 15 years had zero use.
They slightly remind what IfAPI does for struct ifnet. But IfAPI does
that for the sake of large collection of NIC drivers not being aware of
struct ifnet. For the inpcb it is unclear what could be a large
collection of externally written kernel modules that need extensively use
inpcb and not be aware of its internals at the same time. This isolation
of a structure knowledge requires a lot of work, and just throwing in a
few KPIs isn't helpful.

Reviewed by: kib, bz, markj
Differential Revision: https://reviews.freebsd.org/D44310

tcp_fill_info(): Change lock assertion on INPCB to locked only

This function actually only ever reads from the TCP PCB. Consequently,
also make the pointer to its TCP PCB parameter const.

Sponsored by: NetApp, Inc. (originally)

sys: Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.

Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix

Path MTU discovery hooks for offloaded TCP connections.

Notify the TOE driver when when an ICMP type 3 code 4 (Fragmentation
needed and DF set) message is received for an offloaded connection.
This gives the driver an opportunity to lower the path MTU for the
connection and resume transmission, much like what the kernel does for
the connections that it handles.

Reviewed by: glebius@
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D29755

Initial support for kernel offload of TLS receive.

- Add a new TCP_RXTLS_ENABLE socket option to set the encryption and
authentication algorithms and keys as well as the initial sequence
number.

- When reading from a socket using KTLS receive, applications must use
recvmsg(). Each successful call to recvmsg() will return a single
TLS record. A new TCP control message, TLS_GET_RECORD, will contain
the TLS record header of the decrypted record. The regular message
buffer passed to recvmsg() will receive the decrypted payload. This
is similar to the interface used by Linux's KTLS RX except that
Linux does not return the full TLS header in the control message.

- Add plumbing to the TOE KTLS interface to request either transmit
or receive KTLS sessions.

- When a socket is using receive KTLS, redirect reads from
soreceive_stream() into soreceive_generic().

- Note that this interface is currently only defined for TLS 1.1 and
1.2, though I believe we will be able to reuse the same interface
and structures for 1.3.

Convert TOE routing lookups to the new routing KPI.

Reviewed by: np
Differential Revision: https://reviews.freebsd.org/D24388

In order for the TCP Handshake to support ECN++, and further ECN-related
improvements, the ECN bits need to be exposed to the TCP SYNcache.
This change is a minimal modification to the function headers, without any
functional change intended.

Submitted by: Richard Scheffenegger
Reviewed by: rgrimes@, rrs@, tuexen@
Differential Revision: https://reviews.freebsd.org/D22436

Add a TOE KTLS mode and a TOE hook for allocating TLS sessions.

This adds the glue to allocate TLS sessions and invokes it from
the TLS enable socket option handler. This also adds some counters
for active TOE sessions.

The TOE KTLS mode is returned by getsockopt(TLSTX_TLS_MODE) when
TOE KTLS is in use on a socket, but cannot be set via setsockopt().

To simplify various checks, a TLS session now includes an explicit
'mode' member set to the value returned by TLSTX_TLS_MODE. Various
places that used to check 'sw_encrypt' against NULL to determine
software vs ifnet (NIC) TLS now check 'mode' instead.

Reviewed by: np, gallatin
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D21891

Extract eventfilter declarations to sys/_eventfilter.h

This allows replacing "sys/eventfilter.h" includes with "sys/_eventfilter.h"
in other header files (e.g., sys/{bus,conf,cpu}.h) and reduces header
pollution substantially.

EVENTHANDLER_DECLARE and EVENTHANDLER_LIST_DECLAREs were moved out of .c
files into appropriate headers (e.g., sys/proc.h, powernv/opal.h).

As a side effect of reduced header pollution, many .c files and headers no
longer contain needed definitions. The remainder of the patch addresses
adding appropriate includes to fix those files.

LOCK_DEBUG and LOCK_FILE_LINE_ARG are moved to sys/_lock.h, as required by
sys/mutex.h since r326106 (but silently protected by header pollution prior
to this change).

No functional change (intended). Of course, any out of tree modules that
relied on header pollution for sys/eventhandler.h, sys/lock.h, or
sys/mutex.h inclusion need to be fixed. __FreeBSD_version has been bumped.

Add a hook to allow the toedev handling an offloaded connection to
provide accurate TCP_INFO.

Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D14816

sys: general adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

No functional change intended.

* Convert TOE framework to use new routing api.
* Add fib6_lookup_nh_ext().
* Rename union structures:
nhop64_basic -> nhopu_basic,
nhop64_extended -> nhopu_extended

Correctly handle the case where an inp has already been dropped by the time
the TOE driver reports that an active open failed. toe_connect_failed is
supposed to handle this but it should be provided the inpcb instead of the
tcpcb which may no longer be around.

- 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)