Implement virProcessRunInMountNamespace, which runs callback of type
virProcessNamespaceCallback in a container namespace. This uses a
child process to run the callback, since you can't change the mount
namespace of a thread. This implies that callbacks have to be careful
about what code they run due to async safety rules.

Idea by Dan Berrange, based on an initial report by Reco
<recoverym4n@gmail.com> at
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=732394Signed-off-by: NDaniel Berrange <berrange@redhat.com>
Signed-off-by: NEric Blake <eblake@redhat.com>
(cherry picked from commit 7c72ef6f)

Convert the type of loop iterators named 'i', 'j', k',
'ii', 'jj', 'kk', to be 'size_t' instead of 'int' or
'unsigned int', also santizing 'ii', 'jj', 'kk' to use
the normal 'i', 'j', 'k' naming
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

virProcessGetNamespaces() opens files in /proc/XXX/ns/ which will
later be passed to setns(). We have to make sure that the file
descriptors in the array are in the correct order. In particular
the 'user' namespace must be first otherwise setns() may fail
for other namespaces.

The order has been taken from util-linux's sys-utils/nsenter.c

Also we must ignore EINVAL in setns() which occurs if the
namespace associated with the fd, matches the calling process'
current namespace.
Signed-off-by: NRichard Weinberger <richard@nod.at>
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

Resolves:https://bugzilla.redhat.com/show_bug.cgi?id=927620

 #kill -STOP `pidof qemu-kvm`
 #virsh destroy $guest --graceful
 error: Failed to destroy domain testVM
 error: An error occurred, but the cause is unknown

With --graceful, SIGTERM always is emitted to kill driver
process, but it won't success till burning out waiting time
in case of process being stopped.
But domain destroy without --graceful can work, SIGKILL will
be emitted to the stopped process after 10 secs which always
kills a process even one that is currently stopped.
So report an error after burning out waiting time in this case.

Since PIDs can be reused, polkit prefers to be given
a (PID,start time) pair. If given a PID on its own,
it will attempt to lookup the start time in /proc/pid/stat,
though this is subject to races.

It is safer if the client app resolves the PID start
time itself, because as long as the app has the client
socket open, the client PID won't be reused.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

Commit 776d49f4 added a static function that is only called
conditionally; leading to this compile error on mingw:

  CC       libvirt_util_la-virprocess.lo
../../src/util/virprocess.c:624:26: error: 'struct rlimit' declared inside parameter list [-Werror]
../../src/util/virprocess.c:624:26: error: its scope is only this definition or declaration, which is probably not what you want [-Werror]
../../src/util/virprocess.c:622:1: error: 'virProcessPrLimit' defined but not used [-Werror=unused-function]

* src/util/virprocess.c (virProcessPrLimit): Only declare
virProcessPrLimit when used.
Signed-off-by: NEric Blake <eblake@redhat.com>

The source code base needs to be adapted as well. Some files
include virutil.h just for the string related functions (here,
the include is substituted to match the new file), some include
virutil.h without any need (here, the include is removed), and
some require both.

This patch adds two sets of functions:

1) lower level virProcessSet*() functions that will immediately set
the RLIMIT_MEMLOCK. RLIMIT_NPROC, or RLIMIT_NOFILE of either the
current process (using setrlimit()) or any other process (using
prlimit()). "current process" is indicated by passing a 0 for pid.

2) functions for virCommand* that will setup a virCommand object to
set those limits at a later time just after it has forked a new
process, but before it execs the new program.

configure.ac has prlimit and setrlimit added to the list of functions
to check for, and the low level functions log an "unsupported" error)
on platforms that don't support those functions.

Add some APIs for acquiring namespace file descriptors and
switching namespaces
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

virPidFileReadPathIfAlive passed in an 'int *' where a 'pid_t *'
was expected, which breaks on Mingw64 targets. Also a few places
were using '%d' for formatting pid_t, change them to '%lld' and
force a cast to the longer type as done elsewhere in the same
file.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

Win32 platforms don't have SIGKILL defined, but they do have
SIGABRT. Since our virProcess wrapper treats anything which
isn't SIGTERM/SIGINT as equivalent to SIGKILL, just use
SIGABRT on Win32.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

In the cgroups APIs we have a virCgroupKillPainfully function
which does the loop sending SIGTERM, then SIGKILL and waiting
for the process to exit. There is similar functionality for
simple processes in qemuProcessKill, but it is tangled with
the QEMU code. Untangle it to provide a virProcessKillPainfuly
function
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

Continue consolidation of process functions by moving some
helpers out of command.{c,h} into virprocess.{c,h}
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

There are a number of process related functions spread
across multiple files. Start to consolidate them by
creating a virprocess.{c,h} file
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>