sys: Automated cleanup of cdefs and other formatting

Apply the following automated changes to try to eliminate
no-longer-needed sys/cdefs.h includes as well as now-empty
blank lines in a row.

Remove /^#if.*\n#endif.*\n#include\s+<sys/cdefs.h>.*\n/
Remove /\n+#include\s+<sys/cdefs.h>.*\n+#if.*\n#endif.*\n+/
Remove /\n+#if.*\n#endif.*\n+/
Remove /^#if.*\n#endif.*\n/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/types.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/param.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/capsicum.h>/

Sponsored by: Netflix

sys: Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\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spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD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

Introduce the 'n' flag for the geli attach command.

If the 'n' flag is provided the provided key number will be used to
decrypt device. This can be used combined with dryrun to verify if the key
is set correctly. This can be also used to determine which key slot we want to
change on already attached device.

Reviewed by: allanjude
Differential Revision: https://reviews.freebsd.org/D15309

sys/geom: 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.

sys/geom/eli: Switch bzero() to explicit_bzero() for sensitive data

In GELI, anywhere we are zeroing out possibly sensitive data, like
the metadata struct, the metadata sector (both contain the encrypted
master key), the user key, or the master key, use explicit_bzero.

Didn't touch the bzero() used to initialize structs.

Reviewed by: delphij, oshogbo
Sponsored by: ScaleEngine Inc.
Differential Revision: https://reviews.freebsd.org/D9809

Correct a comment and correct style of a flag check.

MFC after: 3 days

Instead of allocating memory for all the keys at device attach,
create reasonably large cache for the keys that is filled when
needed. The previous version was problematic for very large providers
(hundreds of terabytes or serval petabytes). Every terabyte of data
needs around 256kB for keys. Make the default cache limit big enough
to fit all the keys needed for 4TB providers, which will eat at most
1MB of memory.

MFC after: 2 weeks

Move sc_akeyctx and sc_ivctx initialization to the g_eli_mkey_propagate()
function which eliminates code duplication and will ensure proper order
of operation.

A new jail(8) with a configuration file, to replace the work currently done
by /etc/rc.d/jail.

Update copyright years.

MFC after: 1 week

Implement switching of data encryption key every 2^20 blocks.
This ensures the same encryption key won't be used for more than
2^20 blocks (sectors). This will be the default now.

MFC after: 1 week

Remove pointless assignment.

Found with: clang

- Import the HEAD csup code which is the basis for the cvsmode work.

Implement data integrity verification (data authentication) for geli(8).

Supported by: Wheel Sp. z o.o. (http://www.wheel.pl)

Remove trailing spaces.

Add GEOM_ELI class which provides GEOM providers encryption.
For features list and usage see manual page: geli(8).

Sponsored by: Wheel Sp. z o.o.
http://www.wheel.pl
MFC after: 1 week