[  487.497299] Could not find device with ifindex 2000 in netnsfd 11
[  487.497464] Could not find netns with fd: 2000
[  487.497577] Cannot link a netdevsim to itself
[  487.497683] Format for linking two devices is "netnsfd_a:ifidx_a netnsfd_b:ifidx_b" (int uint int uint).