Remove $FreeBSD$: two-line .h pattern

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

ifconfig: remove (most of) the usages of global 'struct ifreq ifr'.

It is hard to reason about the contents of 'ifr' at any given time
as nearly every function sets random fields or pointers in this
structure.
Use local on-stack clean 'struct ifreq' for each function instead.

Reviewed by: kp
Differential Revision: https://reviews.freebsd.org/D40534
MFC after: 2 weeks

ifconfig: remove global 'name' variable.

Consistenly use newly-added 'ctx->ifname' as the name of the current
target interface.

Reviewed By: kp
Differential Revision: https://reviews.freebsd.org/D40438
MFC after: 2 weeks

ifconfig: introduce `ifconfig_context` to store current global state.

The structure consists of all current context - arguments,
open sockets, current family and so on.

Pass this structure as a first argument to most of the af_ menthods.
This allows to propagate and update shared data without using
global variables.

The diff is pretty large, but de-facto mechanical. All changes
except the structure setup in ifconfig[_netlink].c are one-line
mechanical changes.

Reviewed by: kp
Differential Revision: https://reviews.freebsd.org/D40239
MFC after: 2 weeks

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD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

various: 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.

Use strlcpy() instead of strncpy() when copying ifname to ensure
that it is NUL terminated. Additional NUL padding is not required
for short names.

Use sizeof(destination) in a few places instead of IFNAMSIZ.

Cast afp->af_ridreq and afp->af_addreq to make the intent of
the code more obvious.

Reported by: Coverity
CID: 1009628, 1009630, 1009631, 1009632, 1009633, 1009635, 1009638
CID: 1009639, 1009640, 1009641, 1009642, 1009643, 1009644, 1009645
CID: 1009646, 1009647, 1010049, 1010050, 1010051, 1010052, 1010053
CID: 1010054, 1011293, 1011294, 1011295, 1011296, 1011297, 1011298
CID: 1011299, 1305821, 1351720, 1351721
MFC after: 1 week

Replace N #defines with nitems to simplify ifconfig code slightly

MFC after: 1 week

Add new socket ioctls SIOC[SG]TUNFIB to set FIB number of encapsulated
packets on tunnel interfaces. Add support of these ioctls to gre(4),
gif(4) and me(4) interfaces. For incoming packets M_SETFIB() should use
if_fib value from ifnet structure, use proper value in gre(4) and me(4).

Differential Revision: https://reviews.freebsd.org/D2462
No objection from: #network
MFC after: 2 weeks
Sponsored by: Yandex LLC

Add infrastructure to allow all frames/packets received on an interface
to be assigned to a non-default FIB instance.

You may need to recompile world or ports due to the change of struct ifnet.

Submitted by: cjsp
Submitted by: Alexander V. Chernikov (melifaro ipfw.ru)
(original versions)
Reviewed by: julian
Reviewed by: Alexander V. Chernikov (melifaro ipfw.ru)
MFC after: 2 weeks
X-MFC: use spare in struct ifnet