Comment 0 for bug 1968591

[Impact]

An xfrm interface cannot be changed any more since Ubuntu-hwe-5.4-5.4.0-105. In fact, the regression has been introduced by this backport:
https://kernel.ubuntu.com/git/ubuntu/ubuntu-focal.git/commit/?id=13a02539b135

[Test Case]

root@dut-vm:~# ip link add foo type xfrm if_id 1234 dev lo
root@dut-vm:~# ip link change foo type xfrm if_id 1234 dev ntfp1
Error: if_id must be non zero.
root@dut-vm:~# uname -a
Linux dut-vm 5.4.0-107-generic #121~18.04.1-Ubuntu SMP Thu Mar 24 17:21:33 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux
root@dut-vm:~#

[Regression Potential]

The patch is trivial, the potential regressions are low.