[ 1251.500176][T10975] Could not find device with ifindex 2000 in netnsfd 11 [ 1251.500996][T10975] Could not find netns with fd: 2000 [ 1251.501643][T10975] Cannot link a netdevsim to itself [ 1251.502409][T10975] Format for linking two devices is "netnsfd_a:ifidx_a netnsfd_b:ifidx_b" (int uint int uint).