[  491.205729] Could not find device with ifindex 2000 in netnsfd 11
[  491.205895] Could not find netns with fd: 2000
[  491.205985] Cannot link a netdevsim to itself
[  491.206104] Format for linking two devices is "netnsfd_a:ifidx_a netnsfd_b:ifidx_b" (int uint int uint).