On Wed, Aug 07, 2024 at 01:16:03PM -0400, Laine Stump wrote:
> Since the default network now has autoaddr='yes', there is no need to
> waste time during %post install looking for an unused network and
> modifying the config of the default virtual network.
I think this is possibly still compelling to keep.
Consider the user has something network related that they
frequently manually start post boot (a VPN perhaps). We
have the sequence
1. Machine boots
2. User starts something on subset 192.168.122.0/24
3. User installs libvirt
4. Machine shuts down
5. Machine boots
6. Libvirt starts on boot
7. VM auto-starts
8. User starts something on subset 192.168.122.0/24
with steps 5-8 repeating every day.
Currently at step (3), we'll rewrite the default network
to 192.168.123.0, and it'll stay on 192.168.123.0 forever
which gives stability for the install.
With this patch applied, then in step 6 we'll always
start with 192.168.122.0, and then in step 8 change
to 192.168.123.0, breaking the VM from step 7.
That said in the previous patch I suggested that we should
make autoaddr=yes be incompatible with specifying address=
in the XML, which would *require* this patch as we would
no longer have any address in the network XML to modify.
This makes me think that the network driver should remember
auto-assigned networks across reboots.
ie require
<ip autoaddr="yes">
<dhcp/>
</ip>
in the default.xml file, but then have something in
/var/lib/libvirt/networks/subnets.db, where we remember
the auto-assigned subnets a virtual network previously
had. IOW, once an auto-subnet is chosen, it should never
change again, unless a new clash arises.
>
> (It would be even simpler to just install the files directly to /etc
> rather than installing to the examples and then copying to /etc, but
> if we did that then someone who had manually net-undefined the default
> network would keep getting it reinstalled every time there was an
> update to libvirt-daemon-config-network. Of course these days someone
> who wants to do that can simply dnf rm daemon-config-network if they
> didn't want the stock default network config, but nobody will be
> expecting that they have to do that, leading to hundreds of bug
> reports about "I deleted the default network and it comes back every
> time I update my packages!")
>
> Signed-off-by: Laine Stump <laine@xxxxxxxxxx>
> ---
> libvirt.spec.in | 36 +++++-------------------------------
> 1 file changed, 5 insertions(+), 31 deletions(-)
>
> diff --git a/libvirt.spec.in b/libvirt.spec.in
> index 51cecfa598..cb62e0dcdb 100644
> --- a/libvirt.spec.in
> +++ b/libvirt.spec.in
> @@ -1949,38 +1949,12 @@ exit 0
> %libvirt_systemd_config_pre virtnetworkd
>
> %post daemon-config-network
> +# Installing during %post via cp rather than directly as a part of the package manifest
> +# prevents us from reinstalling on update in cases where the user has net-undefined
> +# the default network (and so doesn't *want* it to be reinstalled)
> if test $1 -eq 1 && test ! -f %{_sysconfdir}/libvirt/qemu/networks/default.xml ; then
> - # see if the network used by default network creates a conflict,
> - # and try to resolve it
> - # NB: 192.168.122.0/24 is used in the default.xml template file;
> - # do not modify any of those values here without also modifying
> - # them in the template.
> - orig_sub=122
> - sub=${orig_sub}
> - nl='
> -'
> - routes="${nl}$(ip route show | cut -d' ' -f1)${nl}"
> - case ${routes} in
> - *"${nl}192.168.${orig_sub}.0/24${nl}"*)
> - # there was a match, so we need to look for an unused subnet
> - for new_sub in $(seq 124 254); do
> - case ${routes} in
> - *"${nl}192.168.${new_sub}.0/24${nl}"*)
> - ;;
> - *)
> - sub=$new_sub
> - break;
> - ;;
> - esac
> - done
> - ;;
> - *)
> - ;;
> - esac
> -
> - sed -e "s/${orig_sub}/${sub}/g" \
> - < %{_datadir}/libvirt/networks/default.xml \
> - > %{_sysconfdir}/libvirt/qemu/networks/default.xml
> + cp %{_datadir}/libvirt/networks/default.xml \
> + %{_sysconfdir}/libvirt/qemu/networks/default.xml
> ln -s ../default.xml %{_sysconfdir}/libvirt/qemu/networks/autostart/default.xml
> # libvirt saves this file with mode 0600
> chmod 0600 %{_sysconfdir}/libvirt/qemu/networks/default.xml
> --
> 2.45.2
>
With regards,
Daniel
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