Some DNS requests on my machine take 5 seconds when a specific network interface is used.
My big apologies for the confusion. I have found the reason.
There was a scripted
tc qdisc add dev enp3s0 root netem loss 5%
in effect that I wasn't aware of while investigating.
This dropped 5% of the packets, and also explains why it was on that interface
only.
Well, at least I know very well now at which level `tc` operates.
My bad, and sorry for the noise.
