This fixes a possible double free. In virNetworkAssignDef() if
virBitmapNew() fails, then virNetworkObjFree(network) is called.
However, with network->def pointing to actual @def. So if caller
frees @def again, ...
Moreover, this fixes one possible memory leak too. In
virInterfaceAssignDef() if appending to the list of interfaces
fails, we ought to call virInterfaceObjFree() instead of bare
VIR_FREE().
Although, in order to do that some array size variables needs
to be turned into size_t rather than int.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
The nwfilter conf update mutex previously serialized
updates to the internal data structures for firewall
rules, and updates to the firewall itself. The latter
was recently turned into a read/write lock, and filter
instantiation allowed to proceed in parallel. It was
believed that this was ok, since each filter is created
on a separate iptables/ebtables chain.
It turns out that there is a subtle lock ordering problem
on virNWFilterObjPtr instances. __virNWFilterInstantiateFilter
will hold a lock on the virNWFilterObjPtr it is instantiating.
This in turn invokes virNWFilterInstantiate which then invokes
virNWFilterDetermineMissingVarsRec which then invokes
virNWFilterObjFindByName. This iterates over every single
virNWFilterObjPtr in the list, locking them and checking their
name. So if 2 or more threads try to instantiate a filter in
parallel, they'll all hold 1 lock at the top level in the
__virNWFilterInstantiateFilter method which will cause the
other thread to deadlock in virNWFilterObjFindByName.
The fix is to add an exclusive mutex to serialize the
execution of __virNWFilterInstantiateFilter.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
This resolves a Coverity RESOURCE_LEAK issue introduced by commit
id 'de6fa535' where the virSCSIDeviceSetUsedBy() didn't VIR_FREE
the 'copy' or possibly VIR_STRDUP()'d values. It also ensures that
the VIR_APPEND_ELEMENT is successful...
If SELinux is compiled into libvirt but it is disabled on the host,
libvirtd logs:
error : virIdentityGetSystem:173 : Unable to lookup SELinux process
context: Invalid argument
on each and every client connection.
Use is_selinux_enabled() to skip retrieval of the process's SELinux
context if SELinux is disabled.
Signed-off-by: Michael Chapman <mike@very.puzzling.org>
When domain is started with setting that cannot be done, i.e. those
that require cgroups, there is no error reported and it succeeds
without any message whatsoever.
When setting with API, virsh, an error is reported, but only due to
the fact that no cgroups are mounted (priv->cgroup == NULL).
Given the above it seems reasonable to reject such unsupported
settings.
This patch effectively changes the error message from:
$ virsh -c qemu:///session schedinfo dummy
Scheduler : Unknown
error: Requested operation is not valid: cgroup CPU controller is not mounted
to:
$ virsh -c qemu:///session schedinfo dummy
Scheduler : Unknown
error: Operation not supported: CPU tuning is not available in session mode
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1023366
Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
As of commit 46ec5f85, the conn.lock mutex does not need to be held
when calling any vir*Dispose() function in datatypes.c (via virObjectUnref()).
Signed-off-by: Michael Chapman <mike@very.puzzling.org>
Signed-off-by: Ján Tomko <jtomko@redhat.com>
The qemuMonitorJSONBlockJob handles a few errors internally. If qemu
returns a different error we would report a rather unhelpful message:
$ virsh blockpull gluster-job vda --base /dev/null
error: internal error: Unexpected error
As the actual message from qemu contains a bit more info, let's use it
to report something a little more useful:
$ virsh blockpull gluster-job vda --base /dev/null
error: internal error: Unexpected error: (GenericError) 'Base '/dev/null' not found'
In storageVolLookupByPath the provided path is "sanitized" at first.
This removes some extra slashes and stuff. When the lookup of the volume
fails the original path is used which makes it hard to trace errors in
some cases.
Improve the error message to print the sanitized path along with the
user provided path if they are not equal.
When looking up a volume by path on a non-local filesystem don't use the
"cleaned" path that might be mangled in such a way that it will differ
from a path provided by a storage backend.
Skip the cleanup step for gluster, sheepdog and RBD.
Pools that are not backed by files in the filesystem cause problems with
some APIs. Error out when attempting to upload a volume in such a pool
as currently we expect a local file representation for it.
use_apparmor() was first designed to be called from withing libvirtd,
but libvirt_lxc also uses it. in libvirt_lxc, there is no need to check
whether to use apparmor or not: just use it if possible.
In qemuMonitorJSONExtractCPUInfo an error message hinted on missing
character device data which is wrong.
Also a comment states that only qemu-kvm tree includes the thread_id
field. This is no longer true.
https://bugzilla.redhat.com/show_bug.cgi?id=1071264
Reverting of external snapshots is not supported currently. The check
that is present doesn't properly check for all aspects that make a
snapshot external. Use virDomainSnapshotIsExternal() to do the check.
As I did previously in 4f588a1b46, libvirt needs to set virtio vectors.
Previously, we were advised to use vectors=N, where
N = 2 * (number of queues) + 1
However, just recently this advisory has changed on the Multiquue wiki
page [1] to:
N = 2 * (number of queues) + 2
1: http://www.linux-kvm.org/page/Multiqueue#Enable_MQ_feature
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
If systemd is installed, but is not the init system,
systemd-machined fails with an unhelpful error message:
Launch helper exited with unknown return code 1
Currently we only check if the "machine1" service is
available (in ListActivatableNames).
Also check if "systemd1" service is registered with DBus
(ListNames).
This fixes https://bugs.gentoo.org/show_bug.cgi?id=493246#c22
Introduce virDBusIsServiceInList which can be used to call other
methods for listing services (ListNames), not just ListActivatableNames.
No functional change, fixed the 'Retruns' typo.
Jenkins pointed out that the previous commit violates syntax
check when cppi is installed.
* src/nwfilter/nwfilter_dhcpsnoop.c (SNOOP_POLL_MAX_TIMEOUT_MS):
Update indentation.
Signed-off-by: Eric Blake <eblake@redhat.com>
Libpcap 1.5 requires a larger buffer than previous pcap versions.
Adjust the size of the buffer to 128kb.
This patch should address symptoms in BZ 1071181 and BZ 731059
Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
Cap the poll timeout in the DHCP Snooping code to a max. of 10 seconds
to not hold up the libvirt shutdown longer than this.
Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
The old semantics of virFork() violates the priciple of good
usability: it requires the caller to check the pid argument
after use, *even when virFork returned -1*, in order to properly
abort a child process that failed setup done immediately after
fork() - that is, the caller must call _exit() in the child.
While uses in virfile.c did this correctly, uses in 'virsh
lxc-enter-namespace' and 'virt-login-shell' would happily return
from the calling function in both the child and the parent,
leading to very confusing results. [Thankfully, I found the
problem by inspection, and can't actually trigger the double
return on error without an LD_PRELOAD library.]
It is much better if the semantics of virFork are impossible
to abuse. Looking at virFork(), the parent could only ever
return -1 with a non-negative pid if it misused pthread_sigmask,
but this never happens. Up until this patch series, the child
could return -1 with non-negative pid if it fails to set up
signals correctly, but we recently fixed that to make the child
call _exit() at that point instead of forcing the caller to do
it. Thus, the return value and contents of the pid argument are
now redundant (a -1 return now happens only for failure to fork,
a child 0 return only happens for a successful 0 pid, and a
parent 0 return only happens for a successful non-zero pid),
so we might as well return the pid directly rather than an
integer of whether it succeeded or failed; this is also good
from the interface design perspective as users are already
familiar with fork() semantics.
One last change in this patch: before returning the pid directly,
I found cases where using virProcessWait unconditionally on a
cleanup path of a virFork's -1 pid return would be nicer if there
were a way to avoid it overwriting an earlier message. While
such paths are a bit harder to come by with my change to a direct
pid return, I decided to keep the virProcessWait change in this
patch.
* src/util/vircommand.h (virFork): Change signature.
* src/util/vircommand.c (virFork): Guarantee that child will only
return on success, to simplify callers. Return pid rather than
status, now that the situations are always the same.
(virExec): Adjust caller, also avoid open-coding process death.
* src/util/virprocess.c (virProcessWait): Tweak semantics when pid
is -1.
(virProcessRunInMountNamespace): Adjust caller.
* src/util/virfile.c (virFileAccessibleAs, virFileOpenForked)
(virDirCreate): Likewise.
* tools/virt-login-shell.c (main): Likewise.
* tools/virsh-domain.c (cmdLxcEnterNamespace): Likewise.
* tests/commandtest.c (test23): Likewise.
Signed-off-by: Eric Blake <eblake@redhat.com>
Auditing all callers of virCommandRun and virCommandWait that
passed a non-NULL pointer for exit status turned up some
interesting observations. Many callers were merely passing
a pointer to avoid the overall command dying, but without
caring what the exit status was - but these callers would
be better off treating a child death by signal as an abnormal
exit. Other callers were actually acting on the status, but
not all of them remembered to filter by WIFEXITED and convert
with WEXITSTATUS; depending on the platform, this can result
in a status being reported as 256 times too big. And among
those that correctly parse the output, it gets rather verbose.
Finally, there were the callers that explicitly checked that
the status was 0, and gave their own message, but with fewer
details than what virCommand gives for free.
So the best idea is to move the complexity out of callers and
into virCommand - by default, we return the actual exit status
already cleaned through WEXITSTATUS and treat signals as a
failed command; but the few callers that care can ask for raw
status and act on it themselves.
* src/util/vircommand.h (virCommandRawStatus): New prototype.
* src/libvirt_private.syms (util/command.h): Export it.
* docs/internals/command.html.in: Document it.
* src/util/vircommand.c (virCommandRawStatus): New function.
(virCommandWait): Adjust semantics.
* tests/commandtest.c (test1): Test it.
* daemon/remote.c (remoteDispatchAuthPolkit): Adjust callers.
* src/access/viraccessdriverpolkit.c (virAccessDriverPolkitCheck):
Likewise.
* src/fdstream.c (virFDStreamCloseInt): Likewise.
* src/lxc/lxc_process.c (virLXCProcessStart): Likewise.
* src/qemu/qemu_command.c (qemuCreateInBridgePortWithHelper):
Likewise.
* src/xen/xen_driver.c (xenUnifiedXendProbe): Simplify.
* tests/reconnect.c (mymain): Likewise.
* tests/statstest.c (mymain): Likewise.
* src/bhyve/bhyve_process.c (virBhyveProcessStart)
(virBhyveProcessStop): Don't overwrite virCommand error.
* src/libvirt.c (virConnectAuthGainPolkit): Likewise.
* src/openvz/openvz_driver.c (openvzDomainGetBarrierLimit)
(openvzDomainSetBarrierLimit): Likewise.
* src/util/virebtables.c (virEbTablesOnceInit): Likewise.
* src/util/viriptables.c (virIpTablesOnceInit): Likewise.
* src/util/virnetdevveth.c (virNetDevVethCreate): Fix debug
message.
* src/qemu/qemu_capabilities.c (virQEMUCapsInitQMP): Add comment.
* src/storage/storage_backend_iscsi.c
(virStorageBackendISCSINodeUpdate): Likewise.
Signed-off-by: Eric Blake <eblake@redhat.com>
Right now, a caller waiting for a child process either requires
the child to have status 0, or must use WIFEXITED() and friends
itself. But in many cases, we want the middle ground of treating
fatal signals as an error, and directly accessing the normal exit
value without having to use WEXITSTATUS(), in order to easily
detect an expected non-zero exit status. This adds the middle
ground to the low-level virProcessWait; the next patch will add
it to virCommand.
* src/util/virprocess.h (virProcessWait): Alter signature.
* src/util/virprocess.c (virProcessWait): Add parameter.
(virProcessRunInMountNamespace): Adjust caller.
* src/util/vircommand.c (virCommandWait): Likewise.
* src/util/virfile.c (virFileAccessibleAs): Likewise.
* src/lxc/lxc_container.c (lxcContainerHasReboot)
(lxcContainerAvailable): Likewise.
* daemon/libvirtd.c (daemonForkIntoBackground): Likewise.
* tools/virt-login-shell.c (main): Likewise.
* tools/virsh-domain.c (cmdLxcEnterNamespace): Likewise.
* tests/testutils.c (virtTestCaptureProgramOutput): Likewise.
* tests/commandtest.c (test23): Likewise.
Signed-off-by: Eric Blake <eblake@redhat.com>
The documentation of namespace callbacks was inconsistent on whether
it preserved positive return values. Now that we have a dedicated
EXIT_CANCELED to flag all errors before getting to the callback,
it is possible to use positive return values (not that any of the
current callers do, but it is better to match the docs).
Also, while vircommand.c is careful to close fds that a child should
not have, it's still better to be in the practice of setting
FD_CLOEXEC up front.
* src/util/virprocess.c (virProcessRunInMountNamespace): Tweak
return value to pass back non-zero status. Avoid leaking pipe fds
to other threads.
* src/util/virprocess.h: Fix comment.
Signed-off-by: Eric Blake <eblake@redhat.com>
Thanks to namespaces, we have a couple of places in the code
base that want to reflect a child exit status, including the
ability to detect death by a signal, back to a grandparent.
Best to make it a reusable function.
* src/util/virprocess.h (virProcessExitWithStatus): New prototype.
* src/libvirt_private.syms (util/virprocess.h): Export it.
* src/util/virprocess.c (virProcessExitWithStatus): New function.
* tests/commandtest.c (test23): Test it.
Signed-off-by: Eric Blake <eblake@redhat.com>
When a child fails without exec'ing, we want a well-known status;
best is to match what env(1), nice(1), su(1), and other wrapper
programs do. This patch adds enum values that later patches will
use, and sets up virFork as the first client of EXIT_CANCELED
for errors detected prior to even attempting exec, as well as
virExec to distinguish between a missing executable vs. a binary
that cannot be executed.
This is a slight semantic change in the unlikely case of a child
process failing to restore its signal mask - we now kill the
child with a known status instead of relying on the caller to
notice and do an appropriate _exit(). A subsequent patch will
make further cleanups based on an audit of all callers.
* src/internal.h (EXIT_CANCELED, EXIT_CANNOT_INVOKE)
(EXIT_ENOENT): New enum.
* src/util/vircommand.c (virFork): Document specific exit value if
child aborts early.
(virExec): Distinguish between various exec failures.
* tests/commandtest.c (test1): Enhance test.
(test22): New test.
Signed-off-by: Eric Blake <eblake@redhat.com>
While auditing all callers of virCommandRun, I noticed that nwfilter
code never paid attention to commands with a non-zero status; they
were merely passing a pointer to avoid spamming the logs with a
message about commands that might indeed fail. But proving this
required chasing through a lot of code; refactoring things to
localize the decision of whether to ignore non-zero status makes
it easier to prove that later changes to virFork don't negatively
affect this code.
While at it, I also noticed that ebiptablesRemoveRules would
actually report success if the child process failed for a
reason other than non-zero status, such as OOM.
* src/nwfilter/nwfilter_ebiptables_driver.c (ebiptablesExecCLI):
Change parameter from pointer to bool.
(ebtablesApplyBasicRules, ebtablesApplyDHCPOnlyRules)
(ebtablesApplyDropAllRules, ebtablesCleanAll)
(ebiptablesApplyNewRules, ebiptablesTearNewRules)
(ebiptablesTearOldRules, ebiptablesAllTeardown)
(ebiptablesDriverInitWithFirewallD)
(ebiptablesDriverTestCLITools, ebiptablesDriverProbeStateMatch):
Adjust all clients.
(ebiptablesRemoveRules): Likewise, and fix return value on failure.
Signed-off-by: Eric Blake <eblake@redhat.com>
Openstack Nova calls virConnectBaselineCPU() during initialization
of the instance to get a full list of CPU features.
This patch adds a stub to arm-specific code to handle
this request (no actual work is done).
Signed-off-by: Oleg Strikov <oleg.strikov@canonical.com>
When probing QEMU capabilities fails for a binary generate a
log message with MESSAGE_ID==8ae2f3fb-2dbe-498e-8fbd-012d40afa361.
This can be directly queried from journald based on the UUID
instead of needing string grep. This lets tools like libguestfs'
bug reporting tool trivially do automated sanity tests on the
host they're running on.
$ journalctl MESSAGE_ID=8ae2f3fb-2dbe-498e-8fbd-012d40afa361
Feb 21 17:11:01 localhost.localdomain lt-libvirtd[9196]:
Failed to probe capabilities for /bin/qemu-system-alpha:
internal error: Child process (LC_ALL=C LD_LIBRARY_PATH=
/home/berrange/src/virt/libvirt/src/.libs PATH=/usr/lib64/
ccache:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:
/usr/bin:/root/bin HOME=/root USER=root LOGNAME=root
/bin/qemu-system-alpha -help) unexpected exit status 127:
/bin/qemu-system-alpha: error while loading shared libraries:
libglapi.so.0: cannot open shared object file: No such file
or directory
$ journalctl MESSAGE_ID=8ae2f3fb-2dbe-498e-8fbd-012d40afa361 --output=json
{ ...snip...
"LIBVIRT_SOURCE" : "file",
"PRIORITY" : "3",
"CODE_FILE" : "qemu/qemu_capabilities.c",
"CODE_LINE" : "2770",
"CODE_FUNC" : "virQEMUCapsLogProbeFailure",
"MESSAGE_ID" : "8ae2f3fb-2dbe-498e-8fbd-012d40afa361",
"LIBVIRT_QEMU_BINARY" : "/bin/qemu-system-xtensa",
"MESSAGE" : "Failed to probe capabilities for /bin/qemu-system-xtensa:
internal error: Child process (LC_ALL=C LD_LIBRARY_PATH=/home/berrange
/src/virt/libvirt/src/.libs PATH=/usr/lib64/ccache:/usr/local/sbin:
/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin HOME=/root
USER=root LOGNAME=root /bin/qemu-system-xtensa -help) unexpected
exit status 127: /bin/qemu-system-xtensa: error while loading shared
libraries: libglapi.so.0: cannot open shared object file: No such
file or directory\n" }
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
When a virError is raised, pass the error domain and code
onto the systemd journald using metadata fields.
This allows error messages to be queried by code eg
$ journalctl LIBVIRT_CODE=43
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
The systemd journal expects log record PRIORITY values to
be encoded using the syslog compatible numbering scheme,
not libvirt's own native numbering scheme. We must therefore
apply a conversion.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
The systemd journal accepts arbitrary user specified log
fields. These can be passed into virLogMessage via the
virLogMetadata structure. Allow up to 5 custom fields to
be reported by libvirt callers.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
This patch allows libvirt user to specify 'host-passthrough'
cpu mode while using qemu/kvm backend on arm (arm32).
It uses 'host' as a CPU model name instead of some other stub
(correct CPU detection is not implemented yet) to allow libvirt
user to specify 'host-model' cpu mode as well.
Signed-off-by: Oleg Strikov <oleg.strikov@canonical.com>
As of 0bd2ccdec an empty disk path for virDomainBlockStats (or the one
with Flags) is allowed meaning "get me overall summarized statistics".
However, running 'virsh domblkstat $dom' throws a misleading error:
# ./tools/virsh domblkstat dom
error: Failed to get block stats dom
error: invalid argument: invalid path:
while after this commit
# virsh domblkstat dom
error: Operation not supported: summary statistics are not supported yet
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Libvirt uses a domain name to fill in owner_name in sanlock_options in
virLockManagerSanlockAcquire. Unfortunately, owner_name is limited to
SANLK_NAME_LEN characters (including trailing '\0'), which means domains
with longer names fail to start when sanlock is enabled. However, we can
truncate the name when setting owner_name as explained by sanlock's
author:
Setting sanlk_options or the owner_name is unnecessary, and has very
little to no benefit. If you do provide something in owner_name, it can
be anything, sanlock doesn't care or use it.
If you run the command "sanlock status", the output will display a list
of clients connected to the sanlock daemon. This client list is
displayed as "pid owner_name" if the client has provided an owner_name
via sanlk_options. This debugging output is the only usage of
owner_name, so its only benefit is to potentially provide a more human
friendly output for debugging purposes.
Only tested on v7 but the v8 equivalent seems pretty obvious.
XEN_CAP_REGEX already accepts more than it should (e.g. x86_64p or x86_32be)
but I have stuck with the existing pattern.
With this I can create a guest from:
<domain type='xen'>
<name>libvirt-test</name>
<uuid>6343998e-9eda-11e3-98f6-77252a7d02f3</uuid>
<memory>393216</memory>
<currentMemory>393216</currentMemory>
<vcpu>1</vcpu>
<os>
<type arch='armv7l' machine='xenpv'>linux</type>
<kernel>/boot/vmlinuz-arm-native</kernel>
<cmdline>console=hvc0 earlyprintk debug root=/dev/xvda1</cmdline>
</os>
<clock offset='utc'/>
<on_poweroff>destroy</on_poweroff>
<on_reboot>restart</on_reboot>
<on_crash>destroy</on_crash>
<devices>
<disk type='block' device='disk'>
<source dev='/dev/marilith-n0/debian-disk'/>
<target dev='xvda1'/>
</disk>
<interface type='bridge'>
<mac address='8e:a7:8e:3c:f4:f6'/>
<source bridge='xenbr0'/>
</interface>
</devices>
</domain>
Using virsh create and I can destroy it too.
Currently virsh console fails with:
Connected to domain libvirt-test
Escape character is ^]
error: internal error: cannot find character device <null>
I haven't investigated yet.
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
According to commit b4e0299d if networkAllocateActualDevice() was
successful, it will *always* allocate an iface->data.network.actual,
so we can use this during networkReleaseActualDevice() to know if
there is really anything to undo. We were properly using this
information to only decrement the network connections counter if it
had previously been incremented, but we were unconditionally
unplugging bandwidth and calling the "unplugged" network hook for
*all* interfaces (during qemuProcessStop()) whether they had been
previously plugged or not. This caused problems if a domain failed to
start at some time prior to all interfaces being allocated. (I
encountered this when an interface had a bandwidth floor set but no
inbound QoS).
This patch changes both the call to networkUnplugBandwidth() and the
call to networkRunHook() to only be called if there was a previous
call to "plug" for the same interface.
networkAllocateActualDevice() is called for *all* interfaces, not just
those with type='network'. In that case, it will jump down to its
validate: label immediately, without allocating anything. After
validation is done, two counters are potentially updated (one for the
network, and one for any particular physical device that is chosen),
and then networkRunHook() is called.
This patch refactors that code a slight bit so that networkRunHook()
doesn't get called if netdef is NULL (i.e. type != network) and to
place the conditional increment of dev->connections inside the "if
(netdef)" as well - dev can never be non-null if netdef is null
(because "dev" is the pointer to a device in a network's pool of
devices), so this doesn't have any functional effect, it just makes
the code clearer.
While running virscsitest, it was found that valgrind pointed out the following
memory leak:
==320== 5 bytes in 1 blocks are definitely lost in loss record 4 of 37
==320== at 0x4A069EE: malloc (vg_replace_malloc.c:270)
==320== by 0x3E6CE81171: strdup (strdup.c:43)
==320== by 0x4CB28DF: virStrdup (virstring.c:554)
==320== by 0x4CAC987: virSCSIDeviceSetUsedBy (virscsi.c:289)
==320== by 0x402321: test2 (virscsitest.c:100)
==320== by 0x403231: virtTestRun (testutils.c:199)
==320== by 0x402121: mymain (virscsitest.c:180)
==320== by 0x4039AD: virtTestMain (testutils.c:782)
==320== by 0x3E6CE1ED1C: (below main) (libc-start.c:226)
==320==
Introduced by commit fd243fc.
Signed-off-by: Ján Tomko <jtomko@redhat.com>
Consider dozen of LXC domains, each of them having this type of interface:
<interface type='network'>
<mac address='52:54:00:a7:05:4b'/>
<source network='default'/>
</interface>
When starting these domain in parallel, all workers may meet in
virNetDevVethCreate() where a race starts. Race over allocating veth
pairs because allocation requires two steps:
1) find first nonexistent '/sys/class/net/vnet%d/'
2) run 'ip link add ...' command
Now consider two threads. Both of them find N as the first unused veth
index but only one of them succeeds allocating it. The other one fails.
For such cases, we are running the allocation in a loop with 10 rounds.
However this is very flaky synchronization. It should be rather used
when libvirt is competing with other process than when libvirt threads
fight each other. Therefore, internally we should use mutex to serialize
callers, and do the allocation in loop (just in case we are competing
with a different process). By the way we have something similar already
since 1cf97c87.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
