Bug or misconfiguration for systemd-networkd and VXLAN?

[Lukas Wolf <lukas.e.wolf@xxxxxxxxx>]

Hi all and thanks a lot for all your work on systemd!

I'm trying to setup a VXLAN configuration with multicast with systemd-networkd but struggle to make it work. What I'm trying to replicate is the following (working command):

ip link add vxlan100 type vxlan id 100 dstport 4789 local 10.100.200.4 group 224.4.0.144 dev lo ttl 5

(this command fails without specifying 'dev lo')

My config file, vxlan100.netdev:

[NetDev]
Name=vxlan100
Kind=vxlan

[VXLAN]
VNI=100
TTL=5
DestinationPort=4789
Group=224.0.0.144
Local=10.100.200.4
Independent=true

journalctl -u systemd-networkd (debug log enabled):

systemd-networkd[1520509]: vxlan100: loaded vxlan
systemd-networkd[1520509]: vxlan100: Using MAC address: [snip XYZ]
systemd-networkd[1520509]: vxlan100: Creating

systemd-networkd[1520509]: Failed to read $container of PID 1, ignoring: Permission denied
systemd-networkd[1520509]: Found cgroup on /sys/fs/cgroup/systemd, legacy hierarchy
systemd-networkd[1520509]: Found container virtualization none.
systemd-networkd[1520509]: No virtualization found in DMI vendor table.
systemd-networkd[1520509]: Unable to read /sys/firmware/dmi/entries/0-0/raw, using the virtualization information found in DMI vendor table, ignoring: Permission d>
systemd-networkd[1520509]: UML virtualization not found in /proc/cpuinfo.
systemd-networkd[1520509]: Virtualization XEN not found, /proc/xen does not exist
systemd-networkd[1520509]: No virtualization found in CPUID
systemd-networkd[1520509]: This platform does not support /proc/device-tree
systemd-networkd[1520509]: This platform does not support /proc/sysinfo
systemd-networkd[1520509]: Found VM virtualization none
systemd-networkd[1520509]: /usr/lib/systemd/network/80-container-host0.network: Conditions in the file do not match the system environment, skipping.

[snip]

systemd-networkd[1520509]: vxlan100: netdev could not be created: Invalid argument

As seen in the last line of the log, it throws an invalid argument error and no VXLAN device is created. This does not happen if I remove the "Group=" part in the configuration.  As mentioned above, the "ip add link" command needs a "dev=" argument to work but I have not found a way to specify a device in the netdev config file...

I have also tried it without Independent=true and having a network file instead with VXLAN=vxlan100, but then it just silently fails without log output.

What am I doing wrong or is it a bug?

My system: Linux 4.18.0-372.32.1.el8_6.x86_64 #1 SMP Tue Oct 25 05:53:57 EDT 2022 x86_64 x86_64 x86_64 GNU/Linux

AlmaLinux release 8.7 (Stone Smilodon)

systemd: systemd 239 (239-68.el8)
+PAM +AUDIT +SELINUX +IMA -APPARMOR +SMACK +SYSVINIT +UTMP +LIBCRYPTSETUP +GCRYPT +GNUTLS +ACL +XZ +LZ4 +SECCOMP +BLKID +ELFUTILS +KMOD +IDN2 -IDN +PCRE2 default-hierarchy=legacy

Thanks a lot for your help and kind regards,

Lukas Wolf