Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Add __FBSDID() tags.

MFC after: 3 days

Minor white space tweak.

MFC after: 3 days

Implement mac_get_peer(3) using getsockopt() with SOL_SOCKET and
SO_PEERLABEL. This provides an interface to query the label of a
socket peer without embedding implementation details of mac_t in
the application. Previously, sizeof(*mac_t) had to be specified
by an application when performing getsockopt().

Document mac_get_peer(3), and expand documentation of the other
mac_get(3) functions. Note that it's possible to get EINVAL back
from mac_get_fd(3) when pointing it at an inappropriate object.

NOTE: mac_get_fd() and mac_set_fd() support for sockets will
follow shortly, so the documentation is slightly ahead of the
code.

Obtained from: TrustedBSD Project
Sponsored by: DARPA, Network Associates Laboratories

Eliminate 61 warnings emitted at WARNS=2 (leaving 53 to go).
Only warnings that could be fixed without changing the generated object
code and without restructuring the source code have been handled.

Reviewed by: /sbin/md5

Reflect MAC kernel/user API changes into the libc MAC implementation.
This removes a lot of complexity, since we basically just reserve
space on a retrieval of a label, and pass around strings. Two new
elements: (1) consumers of the API must now declare what label
elements they are interested in retrieving, or (2) rely on the default
provided in a new configuration file, mac.conf.

Approved by: re
Obtained from: TrustedBSD Project
Sponsored by: DARPA, Network Associates Laboratories

Introduce support for Mandatory Access Control and extensible
kernel access control.

Extensions to libc to provide basic MAC label manipulation facilities
for userland. These interface will be replaced in the next month
or two with more flexible interfaces, but provide sufficient support
to allow use of the Biba and MLS policies for user applications.

libc_r wrappers to follow.

Obtained from: TrustedBSD Project
Sponsored by: DARPA, NAI Labs