[  491.235836] Could not find device with ifindex 2000 in netnsfd 11
[  491.236021] Could not find netns with fd: 2000
[  491.236149] Cannot link a netdevsim to itself
[  491.236283] Format for linking two devices is "netnsfd_a:ifidx_a netnsfd_b:ifidx_b" (int uint int uint).