Created attachment 101800 [details]
bt full

I can semi-reliably hit a failed assertion when shutting down a VM:

tap0            : link 41 added
tap0            : udev initializing link...
tap0            : flags change: +MULTICAST +BROADCAST
tap0            : MAC address: fe:8d:25:75:f8:a1
br-qemu         : MAC address: fe:8d:25:75:f8:a1
tap0            : flags change: +UP +LOWER_UP +RUNNING
tap0            : gained carrier
br-qemu         : flags change: +LOWER_UP +RUNNING
br-qemu         : gained carrier
sd-rtnl: discarding 20 bytes of incoming message
tap0            : added address: fe80::fc8d:25ff:fe75:f8a1/64
tap0            : udev initialized link
tap0            : link state is up-to-date
tap0            : unmanaged
tap0            : flags change: -UP -LOWER_UP -RUNNING
tap0            : removed address: fe80::fc8d:25ff:fe75:f8a1/64
tap0            : link removed
tap0            : link 41 added
tap0            : could not find udev device
could not add new link
br-qemu         : MAC address: 00:00:00:00:00:00
br-qemu         : flags change: -LOWER_UP
tap0            : link removed
br-qemu         : flags change: -RUNNING
br-qemu         : lost carrier
sd-rtnl: discarding 20 bytes of incoming message
Assertion 'm' failed at src/network/networkd-link.c:2029, function link_rtnl_process_address(). Aborting.

The KVM is given a bridge device:

# /etc/systemd/network/br-qemu.netdev
[NetDev]
Name=br-qemu
Kind=bridge

# /etc/systemd/network/br-qemu.network
[Match]
Name=br-qemu

[Network]
Description=Qemu vlan
Address=10.0.2.1/24
Address=2001:470:736c:107::1/64


And is started with args: -netdev bridge,br=br-qemu,id=mynet0 -device virtio-net,netdev=mynet0,mac=de:ad:be:ef:00:07

I've bisected this breakage to fbbeb65a93e2f90f6576001b. Backtrace attached. It's likely a race condition somewhere -- the SIGABRT sometimes turns into a SIGSEGV when I set SYSTEMD_LOG_LEVEL=debug.