[  499.696876] Could not find device with ifindex 2000 in netnsfd 11
[  499.697025] Could not find netns with fd: 2000
[  499.697094] Cannot link a netdevsim to itself
[  499.697182] Format for linking two devices is "netnsfd_a:ifidx_a netnsfd_b:ifidx_b" (int uint int uint).