libvirt cannot hot insert interfaces to qemu

[Tim Epkes]

When attempting to hot insert an interface using Ubuntu 16.04.1, I get the following
$ virsh attach-interface --domain gluster1 --type direct \
> --source test0 --model virtio \
> --mac 2a:b6:b0:dc:c7:c4 --config --live
error: Failed to attach interface
error: internal error: unable to execute QEMU command 'getfd': No file descriptor supplied via SCM_RIGHTS

test0 exists:
$ ip link show test0
35: test0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN mode DEFAULT group default qlen 1000
    link/ether aa:8c:65:2e:79:61 brd ff:ff:ff:ff:ff:ff

Just in case I did it wrong with direct, I did network
$ virsh net-list
 Name State Autostart Persistent
----------------------------------------------------------
 default active yes yes
 mgmtnet0 active yes yes

$ virsh attach-interface --domain gluster1 --type network \
> --source default --model virtio \
> --mac 2a:b6:b0:dc:c7:c4 --config --live
error: Failed to attach interface
error: internal error: unable to execute QEMU command 'getfd': No file descriptor supplied via SCM_RIGHTS

This seems to be an old bug, but is still present. Other relevant information:
$ qemu-system-x86_64 --version
QEMU emulator version 2.5.0 (Debian 1:2.5+dfsg-5ubuntu10.5), Copyright (c) 2003-2008 Fabrice Bellard
$ virsh -v
1.3.1

[Thomas Huth (th-huth)]

This looks like a libvirt bug at a first glance. Have you tried to report it to the libvirt project? (See https://libvirt.org/bugs.html ) ... also, can you re-create the bug with the very latest upstream version of libvirt and qemu, or does it only occur with an (older?) version of Ubuntu?

[Christian Ehrhardt  (paelzer)]

That seems to be the Libvirt of Ubuntu in Xenial.

In the past similar issues were uncommon configs or changed behavior on updates that triggered apparmor or SELinux protection.

=> https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1747442
=> https://bugzilla.redhat.com/show_bug.cgi?id=731243

It could as well be some variant of bug 1677398.

If you are still affected by this, could you check:
1. if it also happens on newer libvirt versions e.g. do a trial run in the most recent Ubuntu
2. if it does could you check dmesg in your setup for related apparmor denials?