On Tue Jul 11 08:59:50 2017, kunschikov@gmail.com wrote:
> Hello,
>   we have met the following network setup problem.
> A shift of the system time to the past leads to the incorrect long sleep of
> the dhclient.
> Step by step reproduction:
> 
> 1. obtain address via dhclient at timestamp t1;
> 2. shift system time  to the past to timestamp t2;
> 3.  bug: dhclient misses renew operation. it is sleeping in 'select' for
> "lease time"/2 + (t1 - t2) seconds.
> 
> Time shift can be great, for example in setting up local time on guest
> linux OSes in some hypervisors.  It consequently leads to the losing
> address of the interface.

=> if you use ISC DHCP 4.1 you can try 4.3 which has a different
timer library. You can also try to send a signal to the server in
order to make it to break and restart the select loop.
Note I don't know for Lines but BSDs provide an option to shift
system time without stepping it. Of course it does not work
for big shifts.
To finish I am not surprise a protocol relying on timing has some
problems with a not increasing clock...