Attempting to build a test image with virt-builder fails when installing
packages in the image. As an example, by default libvirt-tck will build a
fedora34 based image to use for its various tests with something like

virt-builder --install dsniff --selinux-relabel --root-password password:123456
--ssh-inject root:file:/var/cache/libvirt-tck/ssh/id_rsa.pub --output
/var/cache/libvirt-tck/os-x86_64-hvm/disk-fedora-34.img --memsize 1024
fedora-34

Them image build process fails when trying to install the dsniff package

error: Curl error (6): Couldn't resolve host name for
https://mirrors.fedoraproject.org/metalink?repo=fedora-cisco-
openh264-34&arch=x86_64 [Could not resolve host: mirrors.fedoraproject.org]
...
virt-builder: error: dnf --verbose -y install 'dsniff': command exited with 
an error

Apparently there is a network problem within the libguestfs appliance used to
install packages in the image. The verbose output of the virt-builder command
contains this suspect line from the appliance

[    1.691749] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
[    2.099182] NET: Registered protocol family 17
/sbin/netconfig: line 52: /dev/fd/63: No such file or directory

Although eth0 in the appliance did received a configuration

2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP
group default qlen 1000
    link/ether 52:54:00:12:34:56 brd ff:ff:ff:ff:ff:ff
    inet 169.254.2.15/16 brd 169.254.255.255 scope global eth0
       valid_lft forever preferred_lft forever

The same issue is observed on SLE15 SP3, but not on SLE15 SP2.