On Fri, 16 Jan 2026 21:01:22 +0000 Andre Carvalho wrote:
> On Mon, Jan 12, 2026 at 06:16:42AM -0800, Jakub Kicinski wrote:
> > On Mon, 12 Jan 2026 09:40:58 +0000 Andre Carvalho wrote:
> > > Introduce a new netconsole selftest to validate that netconsole is able
> > > to resume a deactivated target when the low level interface comes back.
> > >
> > > The test setups the network using netdevsim, creates a netconsole target
> > > and then remove/add netdevsim in order to bring the same interfaces
> > > back. Afterwards, the test validates that the target works as expected.
> > >
> > > Targets are created via cmdline parameters to the module to ensure that
> > > we are able to resume targets that were bound by mac and interface name.
> >
> > The new test seems to be failing in netdev CI:
> >
> > TAP version 13
> > 1..1
> > # timeout set to 180
> > # selftests: drivers/net: netcons_resume.sh
> > # Running with bind mode: ifname
> > not ok 1 selftests: drivers/net: netcons_resume.sh # exit=1
> > --
> > pw-bot: cr
>
> I've finally been able to reproduce this locally. The issue is caused by the
> fact that the test currently expects that mac addresses for netdevsim devices
> are
> deterministic. This is the case on my setup as systemd enforces it
> (MACAddressPolicy=persistent).
Argh, systemd strikes again :(
> I was able to disable this behaviour by setting up
> /etc/systemd/network/50-netdevsim.link, with:
>
> [Match]
> Driver=netdevsim
>
> [Link]
> MACAddressPolicy=none
>
> I'm assuming this is also the behaviour on CI hosts.
Yes, systemd changing the MAC address is racy - it does it too slowly
and some tests start doing their thing, then systemd comes in and flips
the address. So indeed:
# cat /etc/systemd/network/99-default.link
[Match]
OriginalName=*
[Link]
NamePolicy=keep kernel database onboard slot path
AlternativeNamesPolicy=database onboard slot path mac
MACAddressPolicy=none
> I have started working on a fix
> for this test and will submit v11 once that is ready. The approach I'm taking
> is saving and
> restoring the mac addresses once I reload netdevsim module. Example code
> below (needs more testing):
>
> function deactivate() {
> # Start by storing mac addresses so we can be restored in reactivate
> SAVED_DSTMAC=$(ip netns exec "${NAMESPACE}" \
> cat /sys/class/net/"$DSTIF"/address)
> SAVED_SRCMAC=$(mac_get "${SRCIF}")
> # Remove low level module
> rmmod netdevsim
> }
>
> function reactivate() {
> # Add back low level module
> modprobe netdevsim
> # Recreate namespace and two interfaces
> set_network
> # Restore MACs
> ip netns exec "${NAMESPACE}" ip link set "${DSTIF}" \
> address "${SAVED_DSTMAC}"
> if [ "${BINDMODE}" == "mac" ]; then
> ip link set dev "${SRCIF}" down
> ip link set dev "${SRCIF}" address "${SAVED_SRCMAC}"
> # Rename device in order to trigger target resume, as initial
> # when device was recreated it didnt have correct mac address.
> ip link set dev "${SRCIF}" name "${TARGET}"
> fi
> }
>
> The main annoyance is that to test resuming when a device was bound by mac I
> actually need
> to change the name of the device after restoring the mac address (since when
> the device
> is registered after deactivation the mac won't match).
Workaround sounds reasonable, FWIW.
