X-Mailer: MIME-tools 5.508 (Entity 5.508) X-RT-Interface: Web MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: binary X-RT-Original-Encoding: utf-8 Message-ID: References: In-Reply-To: Content-Disposition: inline RT-Send-CC: Content-Length: 1069 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...