[  495.203062] Could not find device with ifindex 2000 in netnsfd 11
[  495.203208] Could not find netns with fd: 2000
[  495.203286] Cannot link a netdevsim to itself
[  495.203393] Format for linking two devices is "netnsfd_a:ifidx_a netnsfd_b:ifidx_b" (int uint int uint).