MFC r297790:
r297790 (by pfg):

libc: replace 0 with NULL for pointers.

While here also cleanup some surrounding code; particularly
drop some malloc() casts.

Found with devel/coccinelle.

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

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

Switch getifaddrs(3) to the new API introduced in r231505. Also remove
conditional code parts not used by or applicable to FreeBSD.

The new implementation is supposed to be able to cope with changes to
the 'l' versions of the msghdr structs now used as well as to if_data
allowing future changes without breaking things.

This restores carp(4) config support in HEAD after r231504.

Reviewed by: glebius, brooks
MFC After: 3 months

Backout changes from r228571. Remove if_data from struct ifa_msghdr again.
While this breaks carp on HEAD temporary, it restores the upgrade path from
stable, and head before 20111215.

Reviewed by: glebius, brooks

A major overhaul of the CARP implementation. The ip_carp.c was started
from scratch, copying needed functionality from the old implemenation
on demand, with a thorough review of all code. The main change is that
interface layer has been removed from the CARP. Now redundant addresses
are configured exactly on the interfaces, they run on.

The CARP configuration itself is, as before, configured and read via
SIOCSVH/SIOCGVH ioctls. A new prefix created with SIOCAIFADDR or
SIOCAIFADDR_IN6 may now be configured to a particular virtual host id,
which makes the prefix redundant.

ifconfig(8) semantics has been changed too: now one doesn't need
to clone carpXX interface, he/she should directly configure a vhid
on a Ethernet interface.

To supply vhid data from the kernel to an application the getifaddrs(8)
function had been changed to pass ifam_data with each address. [1]

The new implementation definitely closes all PRs related to carp(4)
being an interface, and may close several others. It also allows
to run a single redundant IP per interface.

Big thanks to Bjoern Zeeb for his help with inet6 part of patch, for
idea on using ifam_data and for several rounds of reviewing!

PR: kern/117000, kern/126945, kern/126714, kern/120130, kern/117448
Reviewed by: bz
Submitted by: bz [1]

Revert r196976, now that <machine/param.h> behaves predictably.

Add necessary include

sysctl(NET_RT_IFLIST) up to several (currently 5) times.
This will make the behavior robuster if many addresses are added
after the size estimation of storage at the first sysctl.

Reviewed by: JINMEI Tatuya <jinmei@isl.rdc.toshiba.co.jp>
MFC after: 1 week

Fix the style of the SCM ID's.
I believe have made all of libc .c's as consistent as possible.

- cope with sa_len < sizeof(struct sockaddr).
From: Patrik Lindergren <patrik@datacom.nu>
- delint (pointer cast issue). from netbsd-current

Obtained from: KAME
MFC after: 1 week

Remove _THREAD_SAFE and make libc thread-safe by default by
adding (weak definitions to) stubs for some of the pthread
functions. If the threads library is linked in, the real
pthread functions will pulled in.

Use the following convention for system calls wrapped by the
threads library:
__sys_foo - actual system call
_foo - weak definition to __sys_foo
foo - weak definition to __sys_foo

Change all libc uses of system calls wrapped by the threads
library from foo to _foo. In order to define the prototypes
for _foo(), we introduce namespace.h and un-namespace.h
(suggested by bde). All files that need to reference these
system calls, should include namespace.h before any standard
includes, then include un-namespace.h after the standard
includes and before any local includes. <db.h> is an exception
and shouldn't be included in between namespace.h and
un-namespace.h namespace.h will define foo to _foo, and
un-namespace.h will undefine foo.

Try to eliminate some of the recursive calls to MT-safe
functions in libc/stdio in preparation for adding a mutex
to FILE. We have recursive mutexes, but would like to avoid
using them if possible.

Remove uneeded includes of <errno.h> from a few files.

Add $FreeBSD$ to a few files in order to pass commitprep.

Approved by: -arch

defined HAVE_IFM_DATA for (free|net|open)bsd

Submitted by: JINMEI Tatuya <jinmei@isl.rdc.toshiba.co.jp>
Obtained from: KAME Project

add getifaddrs(3) from bsdi. this is a magic function which lets you grab
interface addresses in a portable manner, without headache of SIOCGIFCONF
or sysctl. it is in bsdi/openbsd/netbsd already.
from kame tree (actually, mandatory for latest kame tree).