In my previous patches I enabled the IFF_MULTI_QUEUE flag every
time the user requested multiqueue TAP device. However, this
works only at runtime. During build time the flag may be
undeclared.

In order to learn libvirt multiqueue several things must be done:

1) The '/dev/net/tun' device needs to be opened multiple times with
IFF_MULTI_QUEUE flag passed to ioctl(fd, TUNSETIFF, &ifr);

2) Similarly, '/dev/vhost-net' must be opened as many times as in 1)
in order to keep 1:1 ratio recommended by qemu and kernel folks.

3) The command line construction code needs to switch from 'fd=X' to
'fds=X:Y:...:Z' and from 'vhostfd=X' to 'vhostfds=X:Y:...:Z'.

4) The monitor handling code needs to learn to pass multiple FDs.

Currently, we have one huge function to construct qemu command line.
This is very ineffective esp. if there's a fault somewhere.

This attribute is going to represent number of queues for
multique vhost network interface. This commit implements XML
extension part of the feature and add one test as well. For now,
we can only do xml2xml test as qemu command line generation code
is not adapted yet.

example: qemu ${otherargs} \
             -vnc 127.0.0.1:0,share=allow-exclusive

 -vnc :5900,share=allow-exclusive
allows clients to ask for exclusive access which is
implemented by dropping other connections Connecting
multiple clients in parallel requires all clients asking
for a shared session (vncviewer: -shared switch)

 -vnc :5900,share=force-shared
disables exclusive client access.  Useful for shared
desktop sessions, where you don't want someone forgetting
specify -shared disconnect everybody else.

 -vnc :5900,share=ignore
completely ignores the shared flag and allows everybody
connect unconditionally

QEMU_CAPS_VNC_SHARE_POLICY (qemu >= 1.1)

In my review of 31532cab I missed the fact that VIR_STRDUP
now returns 1 on success, and 0 if the source was NULL.

(This still doesn't add proper OOM error handling.)

Only a few cases are allowed:

1) The expression is empty for "for" loop, E.g.

  for (i = 0; ; i++)

2) An empty statement

  while (write(statuswrite, &status, 1) == -1 &&
         errno == EINTR)
      ; /* empty */

3) ";" is inside double-quote, I.e, as part of const string. E.g.

  vshPrint(ctl, "a ; b ; cd;\n");

The "for" loop in src/rpc/virnettlscontext.c is the special case,
1) applies for it, so change it together in this patch.

The more common habit is to add the comment after the statements.

Introduced by commit 7ac2c4fe, pushed under build-breaker rule.

virConnectListAllInterfaces should support to list all of
interfaces when the value of flags is 0. The behaviour is
consistent with other virConnectListAll* APIs

https://bugzilla.redhat.com/show_bug.cgi?id=965169 documents a
problem starting domains when cgroups are enabled; I was able
to reliably reproduce the race about 5% of the time when I added
hooks to domain startup by 3 seconds (as that seemed to be about
the length of time that qemu created and then closed a temporary
thread, probably related to aio handling of initially opening
a disk image).  The problem has existed since we introduced
virCgroupMoveTask in commit 91028296 (v0.10.0).

There are some inherent TOCTTOU races when moving tasks between
kernel cgroups, precisely because threads can be created or
completed in the window between when we read a thread id from the
source and when we write to the destination.  As the goal of
virCgroupMoveTask is merely to move ALL tasks into the new
cgroup, it is sufficient to iterate until no more threads are
being created in the old group, and ignoring any threads that
die before we can move them.

It would be nicer to start the threads in the right cgroup to
begin with, but by default, all child threads are created in
the same cgroup as their parent, and we don't want vcpu child
threads in the emulator cgroup, so I don't see any good way
of avoiding the move.  It would also be nice if the kernel were
to implement something like rename() as a way to atomically move
a group of threads from one cgroup to another, instead of forcing
a window where we have to read and parse the source, then format
and write back into the destination.

* src/util/vircgroup.c (virCgroupAddTaskStrController): Ignore
ESRCH, because a thread ended between read and write attempts.
(virCgroupMoveTask): Loop until all threads have moved.
Signed-off-by: NEric Blake <eblake@redhat.com>

Introduce use of a virDomainDefPtr in the domain coredump
APIs to simplify introduction of ACL security checks.
The virDomainPtr cannot be safely used, since the app
may have supplied mis-matching name/uuid/id fields. eg
the name points to domain X, while the uuid points to
domain Y. Resolving the virDomainPtr to a virDomainDefPtr
ensures a consistent name/uuid/id set.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>