libexec: 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

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spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD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

tftpd: Use poll() instead of alarm() + setjmp().

While there, don't log an error when timing out waiting for a possible retransmit after a successful transfer.

Sponsored by: Klara, Inc.
Reviewed by: markj
Differential Revision: https://reviews.freebsd.org/D38966

tftpd: Make the transfer functions return success / failure.

Sponsored by: Klara, Inc.
Reviewed by: markj
Differential Revision: https://reviews.freebsd.org/D38957

tftpd: whitespace cleanup

tftpd: cleanup

Sponsored by: Klara, Inc.

When receiving a file having a length, which is a mulitple of the blocksize,
close the file once it is received.

Reported by: Timo Voelker
MFC after: 1 week

Improve the counting of blocks used to transfer a file from the
server to the client in case of not using an OACK: Don't miss
the first block in case of it is not also the last one.

MFC after: 1 week

Fix the TFTP client when performing a RRQ for files smaller than 512 bytes
and the server not sending an OACK:
* Close the file.
* Report the correct the number of received blocks.

MFC after: 1 week

Abort transfer if fseeko() fails.

CID: 1420215
Reviewed by: asomers
MFC after: 1 week
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D24454

Add support for the TFTP windowsize option described in RFC 7440.

The windowsize option permits multiple blocks to be transmitted
before the receiver sends an ACK improving throughput for larger
files.

Reviewed by: asomers
MFC after: 2 weeks
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D23836

tftpd(8): when completing an WRQ, flush the file before acknowleding receipt

tftpd(8) should flush a newly written file to disk before ACKing the final DATA
packet. Otherwise there is a narrow race window when a subsequent read may not
see the file. This is somewhat related to r330710, but the race window is much
smaller. Hopefully this will fix the intermittent tests in Jenkins.

Reported by: Jenkins
MFC after: 2 weeks

tftpd: Flush files as soon as they are fully received

On an RRQ, tftpd doesn't exit as soon as it's finished receiving a file.
Instead, it waits five seconds just in case the client didn't receive the
server's last ACK and decides to resend the final DATA packet.
Unfortunately, this created a 5 second delay from when the client thinks
it's done sending the file, and when the file is available for other
processes.

Fix this bug by closing the file as soon as receipt is finished.

PR: 157700
Reported by: Barry Mishler <barry_mishler@yahoo.com>
MFC after: 3 weeks

libexec: 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.

In the old TFTP server, there was an undocumented behavior where
the block counter would rollover to 0 if a file larger
than 65535 blocks was transferred. With the default block size
of 512 octets per block, this is a file size of approximately 32 megabytes.

The new TFTP server code would report an error and stop transferring
the file if a file was larger than 65535 blocks.

This patch restores the old TFTP server's behavior to the new
TFTP server code. If a TFTP client transfers a file larger
than 65535 blocks, and does *not* specify the "rollover" option,
then automatically rollover the block counter to 0 every time
we reach 65535 blocks.

This restores interoperability with the FreeBSD 6 TFTP client.
Without this change, if a FreeBSD 6 TFTP client tried to
retrieve a file larger than 65535 blocks from a FreeBSD 9 TFTP server
, the transfer would fail.
The same file could be retrieved successfully if the same FreeBSD 6
TFTP client was used against a FreeBSD 6 TFTP server.

Approved by: re (kib)
Tested by: Pawan Gupta <pawang at juniper dot net>,
Obtained from: Juniper Networks

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

Bring in new files from edwin's tftp