[  487.215833] Could not find device with ifindex 2000 in netnsfd 11
[  487.215995] Could not find netns with fd: 2000
[  487.216086] Cannot link a netdevsim to itself
[  487.216186] Format for linking two devices is "netnsfd_a:ifidx_a netnsfd_b:ifidx_b" (int uint int uint).