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Description of problem:

The unprivileged libvirtd does not support nwfilter config, but leaves the
driver active. It is supposed to result in all APIs being an effective
no-op, but several APIs rely on driver->nwfilters being non-NULL, or they
will reference a NULL pointer. Rather than adding checks for NULL in many
places, just make sure  driver->nwfilters is always initialized.

Need to backport upstream commit id 7993554f70fd8d512dfde484490bcd1601b60b33

I can reproduce on libvirt-3.9.0-5.el7.x86_64

$ virsh nwfilter-list 

error: Disconnected from qemu:///session due to end of file
error: Failed to list node filters
error: Cannot recv data: Connection reset by peer

verify this bug on libvirt-3.9.0-6.el7.x86_64

$ virsh nwfilter-list
 UUID                                  Name                 
------------------------------------------------------------------

$ ps -ef | grep test | grep libvirt | grep -v grep 
test     26402     1 33 17:12 ?        00:00:00 /usr/sbin/libvirtd --timeout=30

This bug also affects Fedora 27 x86_64. I was able to replicate the issue by running "virsh nwfilter-list" as a non-root user and getting the same errors as originally reported.

RPM: libvirt-3.7.0-3.fc27.x86_64

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHEA-2018:0704