Fixup option handling after r293778 by wrapping MK_INET6_SUPPORT in a
KERNBUILDDIR check.

Sponsored by: Limelight Networks

Fix LINT-NOINET kernels

- Generate opt_inet.h appropriately according to MK_INET_SUPPORT
- Only add in_gif.c to SRCS if MK_INET_SUPPORT != no

This is a surgical fix since the build infrastructure has diverged sufficiently
between stable/10 and head.

This change will likely be reverted if and when imp's changes to config.mk have
been backported to ^/stable/10 .

Reviewed by: ae (no serious objections)
Differential Revision: https://reviews.freebsd.org/D4864
MFC after: 1 week
Sponsored by: EMCC / Isilon Storage Division

MFC r274246:
Overhaul if_gre(4).

Split it into two modules: if_gre(4) for GRE encapsulation and
if_me(4) for minimal encapsulation within IP.

gre(4) changes:
* convert to if_transmit;
* rework locking: protect access to softc with rmlock,
protect from concurrent ioctls with sx lock;
* correct interface accounting for outgoing datagramms (count only payload size);
* implement generic support for using IPv6 as delivery header;
* make implementation conform to the RFC 2784 and partially to RFC 2890;
* add support for GRE checksums - calculate for outgoing datagramms and check
for inconming datagramms;
* add support for sending sequence number in GRE header;
* remove support of cached routes. This fixes problem, when gre(4) doesn't
work at system startup. But this also removes support for having tunnels with
the same addresses for inner and outer header.
* deprecate support for various GREXXX ioctls, that doesn't used in FreeBSD.
Use our standard ioctls for tunnels.

me(4):
* implementation conform to RFC 2004;
* use if_transmit;
* use the same locking model as gre(4);

PR: 164475

MFC r274289 (by bz):
gcc requires variables to be initialised in two places. One of them
is correctly used only under the same conditional though.

For module builds properly check if the kernel supports INET or INET6,
as otherwise various mips kernels without IPv6 support would fail to build.

MFC r274964:
Add ip_gre.h to ObsoleteFiles.inc.

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

Remove opt_mac.h generation for various kernel modules that no longer
require it.

Submitted by: pjd

Reimplementation of world/kernel build options. For details, see:

http://lists.freebsd.org/pipermail/freebsd-current/2006-March/061725.html

The src.conf(5) manpage is to follow in a few days.

Brought to you by: imp, jhb, kris, phk, ru (all bugs are mine)

When compiling with the kernel, detect if INET6 support should be disabled.

In this case, disable wrapping of fake opt_*.h targets in
"if defined(KERNBUILDDIR)" for now since the new way of
building modules with the kernel can't handle dynamic SRCS
depending on build options yet.

Let modules use the kernel's opt_*.h files if built along with
the kernel by wrapping all targets for fake opt_*.h files in
.if defined(KERNBUILDDIR). Thus, such fake files won't be
created at all if modules are built with the kernel.

Some modules undergo cleanup like removing unused or unneeded
options or .h files, without which they wouldn't build this way
or the other.

Reviewed by: ru
Tested by: no binary changes in modules built alone
Tested on: i386 sparc64 amd64

NOINET6 -> NO_INET6

kmod.mk knows how to create empty opt_*.h files so let it deal with the
NOINET6 case.

Reported by: ru

Allow the gif module to be built without IPv6 support when NOINET6 is
defined.

Submitted by: mitrohin a.s. <swp at uni-altai dot ru>

Depend on opt_mac.h.

Drop <bsd.man.mk> support from <bsd.kmod.mk>.

Not objected to by: -current

gif(4) and stf(4) modernization:

- Remove gif dependencies from stf.
- Make gif and stf into modules
- Make gif cloneable.

PR: kern/27983
Reviewed by: ru, ume
Obtained from: NetBSD
MFC after: 1 week