bonding: fail to enslave an up interface with one netlink message

[Nicolas Dichtel]

[Impact]

After the linux upstream commit a4abfa627c38 ("net: rtnetlink: Enslave device before bringing it up"), pushed in v6.1, the following set of commands fails:
$ ip link add dummy0 type dummy
$ ip link add bond0 type bond
$ ip link set dummy0 up
$ ip link set dummy0 master bond0 down
Error: Device can not be enslaved while up.

This breaks existing scripts.

This problem has been fixed upstream with the commit ec4ffd100ffb ("Revert "net: rtnetlink: Enslave device before bringing it up""). The commit has been backported in upstream stable kernels (v6.1.75, v6.6.14, v6.7.2) but is missing the 23.10 kernel (6.5).

[Test Case]

$ ip link add dummy0 type dummy
$ ip link add bond0 type bond
$ ip link set dummy0 up
$ ip link set dummy0 master bond0 down
=> no error should happen

[Regression Potential]

The patch is a straight revert of the faulty commit, so it goes back to the original code, which has been there for decades. It has been backported successfully in upstream kernels.

[Nicolas Dichtel (nicolas-dichtel)]

https://lists.ubuntu.com/archives/kernel-team/2024-May/150771.html