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:

quoted

On Mon, 12 Jan 2026 09:40:58 +0000 Andre Carvalho wrote:  

quoted

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.