On 8/15/22 1:00 PM, Pascal wrote:
Hi,
I am a bit lost and hope someone can help me. I am running Debian
bookworm (testing) with last updates.
$ sudo apt policy libvirt-daemon
libvirt-daemon:
Installé : 8.5.0-1
Candidat : 8.5.0-1
Table de version :
*** 8.5.0-1 100
100 /var/lib/dpkg/status
I am unable to start default network , and get an error related to
iptables :
$ sudo virsh net-start default
erreur :Impossible de démarrer le réseau default
erreur :internal error: Failed to apply firewall rules
/usr/sbin/iptables -w --table filter --list-rules: libvirt: erreur :
cannot execute binary /usr/sbin/iptables: Aucun fichier ou dossier de ce
type
Sorry for the french, it says "impossible to start default network" and
"no such file or folder" at the end.
libvirt execs the iptables command to install packet filtering rules
that are part of the setup of virtual networks with forward mode of
"nat", "route", and for those virtual networks that have no forward mode
at all (aka "isolated"). libvirt's default network uses NAT to make all
virtual machines appear to be at the IP address of the host's external
ethernet interface, so it requires the iptables command
Although I've been working on patches to make it possible for libvirt to
use /usr/sbin/nft to add & remove packet filter rules, libvirt still
uses iptables to add its rules, so if have a virtual network that needs
to add packet filtering rules (or a guest that has nwfilter rules),
you'll need the iptables command, and if it's not found then libvirt
will fail at runtime (as you've seen).
Beyond that, if you install the libvirt-daemon-driver-nwfilter or
libvirt-daemon-driver-network packages, then iptables *should* be a hard
prerequisite listed in the package manifest; if your distro's packaging
system is allowing you to remove the iptables package without also
removing those libvirt packages (which is what you say you were able to
do), or allowing you to install those libvirt packages without
(semi)automatically pulling in iptables (which you also say you've
done), then that is a bug in the distro's packaging files for libvirt.
It's unclear from your original message if you really require libvirt's
default network in any of your guests. If you don't, then you can just
not install or start the libvirt-daemon-driver-network package, and
don't try to start the default network, and you should be okay without
the iptables package on your system. It's not really gaining you
anything (other than a miniscule amount of disk space) to do that though.
These days /usr/sbin/iptables is a symbolic link to either iptables-nft
(which uses the nftables API to put all the rules into special nft
tables named "filter" and "nat", so you actually see the iptables rules
as nft rules when you run "nft list ruleset") or to
/usr/sbin/iptables-legacy (which uses the old iptables API to install
rules that *don't* show up in "nft list ruleset"). In either case
though, packets are processed using the same nft packet matching code in
the kernel. There is some amount of info about these two variants here:
https://developers.redhat.com/blog/2020/08/18/iptables-the-two-variants-and-their-relationship-with-nftables
The end of it all though is that even if you have some userspace
programs that "use iptables", they are in the end using nftables in the
kernel.
It is true I removed iptables because I want to use only nftables (I
removed both ufw and iptables packages (apt remove), and enabled the
nftables service before error raises). Before this, all was fine, but
when I enabled nftables, all VMs disapeared from virt-manager).
Are the guests completely disappearing from the list? Or is it that
you're unable to start the guests? A guest would only completely
disappear spontaneously from virt-manager (i.e. be completely removed
from the list of all guests) if something went wrong while parsing the
guest config during libvirtd (or virtqemud) startup. Look in the system
logs for any errors during libvirtd startup (or virtqemud startup if
your debian has switched to modular daemons). I can't think of anything
that could/should change in the parsing of the config due to enabling
the nftables servive (which libvirt knows nothing about).
I uninstalled KVM related packages and reinstalled, still the same.
I also installed back iptables, but strangely I still get the same
error, although binary /usr/sbin/iptables is there.
Now that certainly makes no sense! :-/ Possibly /usr/sbin/iptables is a
symbolic link to a file that doesn't exist (because there was an
additional iptables package, e.g. iptables-nft or iptables-legacy, that
you didn't reinstall?)
I tried many things with no luck, restarted libvirtd service, recreated
the network, etc...
Has anyone some idea about what is happening here ? is there some
incompatibility with nftables (firewalld service is disabled) and libvirt ?
As I've said above, libvirt is still using iptables to add its rules,
but there is no incompatibility with nftables, and in fact the rules
under the hood end up being nftables rules.
