virNetlinkEventCallback:700 : nl_recv returned with error: No buffer space available

[GOVINDA TATTI]

We are observing the following error while creating VMs

Sep 27 14:25:47 xpl-dvt-41 libvirtd[4927]: 2018-09-27 21:25:47.387+0000: 4927: error : virNetlinkEventCallback:700 : nl_recv returned with error: No buffer space available

This message is observed with latest Bionic libvirt packages.

lab@xpl-dvt-35:~$ dpkg -l | grep libvirt
ii gir1.2-libvirt-glib-1.0:amd64 1.0.0-1 amd64 GObject introspection files for the libvirt-glib library
ii libsys-virt-perl 4.0.0-1 amd64 Perl module providing an extension for the libvirt library
ii libvirt-bin 4.0.0-1ubuntu8.5 amd64 programs for the libvirt library
ii libvirt-clients 4.0.0-1ubuntu8.5 amd64 Programs for the libvirt library
ii libvirt-daemon 4.0.0-1ubuntu8.5 amd64 Virtualization daemon
ii libvirt-daemon-system 4.0.0-1ubuntu8.5 amd64 Libvirt daemon configuration files
ii libvirt-glib-1.0-0:amd64 1.0.0-1 amd64 libvirt GLib and GObject mapping library
ii libvirt0:amd64 4.0.0-1ubuntu8.5 amd64 library for interfacing with different virtualization systems
ii python-libvirt 4.0.0-1 amd64 libvirt Python bindings

[Robie Basak (racb)]

Thank you for taking the time to report this bug and helping to make Ubuntu better.

Since there isn't enough information in your report to differentiate between a local configuration problem and a bug in Ubuntu, I'm marking this bug as Incomplete.

Specifically, please provide full steps to reproduce your problem.

If indeed this is a local configuration problem, you can find pointers to get help for this sort of problem here: http://www.ubuntu.com/support/community

Or if you believe that this is really a bug, then you may find it helpful to read "How to report bugs effectively" http://www.chiark.greenend.org.uk/~sgtatham/bugs.html. We'd be grateful if you would then provide a more complete description of the problem, explain why you believe this is a bug in Ubuntu rather than a problem specific to your system, and then change the bug status back to New.

[Christian Ehrhardt  (paelzer)]

Also the error doesn't indicate that libvirt is doing anything wrong here.
It runs nl_recv [1] in virNetlinkEventCallback which eventually will do recvmsg [2] and gets reported that it didn't fit - so it correctly relay that up the stack.

Now that is a somewhat known issue [3], but it should be fixed in libnl instead of libvirt.
Then around that time one of that kind fixed in libnl [4].
There also was a related issue with some sockets opened with special flags behaving wrong by using other sizes, but that was fixed as well.

All those fixes are known and present in Ubuntu Bionic and later (even quite some earlier).
There are now two possible cases for this IMHO:
1. you found a new reproducible case to trigger this, then we should outline it and forward to the libnl development to fix it - please report if you have a clear case or just found that in the libvirt log a few times.
2. This was just an effect of a low memory or overload (too much messages queue up) situation that can't really be avoided - and in this case it would be fine for libnl to trigger the error and for libvirt to report it in the log to make the admin aware.

For both keeping the bug as "incomplete" for now is correct.

[1]: https://www.infradead.org/~tgr/libnl/doc/api/group__send__recv.html#ga48ab5192dfa62d6b71760d43a4306d13
[2]: http://manpages.ubuntu.com/manpages/xenial/man2/recv.2.html
[3]: https://www.redhat.com/archives/libvir-list/2014-June/msg00834.html
[4]: https://www.redhat.com/archives/libvir-list/2014-June/msg00823.html

[GOVINDA TATTI (gtatti)]

As per QA, these messages were found in syslog while creating a 16GPU VM but there is no functionality loss or issue.

[Launchpad Janitor (janitor)]

[Expired for libvirt (Ubuntu) because there has been no activity for 60 days.]

[Launchpad Janitor (janitor)]

[Expired for libnl3 (Ubuntu) because there has been no activity for 60 days.]

[Anish Gupta (anish70)]

Govinda,

Is this still an issue? If yes, can you reopen the bug ..
If not, advise next steps ...

thanks,
Anish

[GOVINDA TATTI (gtatti)]

We have not seen this bug in the recent time. So, this bug can be closed.

[Christian Ehrhardt  (paelzer)]

I've dupped another case onto this, it stays an issue that from the libvirt side has been handled by
https://gitlab.com/libvirt/libvirt/-/commit/8c70d04bab7278c96390a913fa949a17cd3124f9 which is in >=Bionic.

AFAIU remaining issues as outlined in comment #2 are still considered more an libnl/driver than a libvirt issue.

[Alex Shnyrov (1993alexey)]

I'm seeing this issue. Unable to start the VM.

```
virNetlinkEventCallback:868 : nl_recv returned with error: No buffer space available
```

My setup:
Ubuntu 22.04
Two RTX 6000 Ada
CPU AMD EPYC 7742 64-Core Processor

Is there a recommended fix? Comment #8 suggests this has been solved in >= Bionic, but why am I still seeing it then?