[  493.618029] Could not find device with ifindex 2000 in netnsfd 11
[  493.618203] Could not find netns with fd: 2000
[  493.618304] Cannot link a netdevsim to itself
[  493.618432] Format for linking two devices is "netnsfd_a:ifidx_a netnsfd_b:ifidx_b" (int uint int uint).