[  495.027237] Could not find device with ifindex 2000 in netnsfd 11
[  495.027399] Could not find netns with fd: 2000
[  495.027484] Cannot link a netdevsim to itself
[  495.027570] Format for linking two devices is "netnsfd_a:ifidx_a netnsfd_b:ifidx_b" (int uint int uint).