New-style DNS without systemd-resolved causes lookup loops #1120
Description
On machines without systemd-resolved or with its configuration set to DNSStubListener=no, it seems like DNS lookups cause loops.
On those systems, netclient (Linux v1.1.0) inserts itself as the first nameserver entry in /etc/resolv.conf.
On a machine with active DNS traffic, the number of DNS "connections" to the netclient quickly reached a ceiling around 28k (as listed with netstat -nuap | grep netclient | wc -l ). Then, DNS lookups were slow or even failed until netclient was stopped.
On a machine with light DNS traffic, the number only rose to about 15 or so and did not affect performance.
It seems that netclient directly or indirectly asks itself recursively when its address is at the top of resolv.conf.
On the two machines with problems, activating systemd-resolved (or resetting DNSStubListener=yes, respectively) solved the problems.
netclient should perform some checks to ensure that this does not happen. (Or at least include documentation explaining how to avoid this.)