[Dnsmasq-discuss] Bug-ette Android requesting excessive leases

[Carlos Carvalho]

Albert ARIBAUD (albert.aribaud at free.fr) wrote on Fri, Oct 23, 2015 at 04:58:40PM BRST:
> Hi Ed,
> 
> Le Fri, 23 Oct 2015 17:55:06 +0100, Ed W <lists at wildgooses.com> a
> écrit :
> 
> > Hi
> > 
> > I notice an anomaly with my OnePlus Android phones.  They have been 
> > acquiring additional leases for no good reason.  Here is a dump from a 
> > little app I have which monitors ARP and dhcp lease allocations:
> > 
> > 192.168.105.103/c0:ee:fb:34:64:18 - OnePlus Tech (Shenzhen) Ltd - 
> > android-a837a8c17ea54bc3 - leased until: 2015-10-26T16:34:12 - seen: 
> > 2015-10-23T16:39:00
> > 192.168.105.105/c0:ee:fb:34:64:18 - OnePlus Tech (Shenzhen) Ltd - leased 
> > until: 2015-10-24T14:31:08
> > 192.168.105.106/c0:ee:fb:34:64:18 - OnePlus Tech (Shenzhen) Ltd - leased 
> > until: 2015-10-25T16:05:49
> > 192.168.105.115/c0:ee:fb:42:63:b1 - OnePlus Tech (Shenzhen) Ltd - leased 
> > until: 2015-10-24T14:28:00
> > 192.168.105.116/c0:ee:fb:42:63:b1 - OnePlus Tech (Shenzhen) Ltd - leased 
> > until: 2015-10-24T15:34:39
> > 192.168.105.117/c0:ee:fb:42:63:b1 - OnePlus Tech (Shenzhen) Ltd - leased 
> > until: 2015-10-25T12:16:12
> > 192.168.105.118/c0:ee:fb:42:63:b1 - OnePlus Tech (Shenzhen) Ltd - 
> > android-9fe15ff2e8e65398 - leased until: 2015-10-26T15:45:48 - seen: 
> > 2015-10-23T16:39:00
> > 
> > DNSMasq 2.75, operating on a bridge br0 of two devices wlan/lan.
> > 
> > What you can see here are my two OnePlus devices have apparently 
> > acquired additional leases for no obvious reason. The "seen" shows that 
> > my arp-ping isn't seeing any answer on the other lease addresses, so we 
> > can be sure it's not a genuine case of multiple IPs per MAC
> > 
> > The relevant config is
> >      dhcp-range=192.168.105.50,192.168.105.150,72h
> >      dhcp-authoritative
> > 
> > Unfortunately I don't have the logs for the allocations (it's on a small 
> > router which logs to memory only).
> > 
> > However, my best guess on what happened is that on lease renewal the 
> > Android device is answering dnsmasq's ping (to check if the IP is free)?
> > 
> > If this is interesting/plausible I can try cranking down my lease times 
> > and record the logs to see if I can catch it in action?
> 
> Problem is, we don't see what IP is requested, nor do we see which DHCP
> requests or replies are sent.

Yes. Also, how do you know the client didn't release the address before
requesting another one?

> Can you ssh to your server from your desktop machine? If yes, then you
> should do so, then through this shell, kill the background dnsmasq and
> launch it in the foreground (with -d, and -q --log-dhcp too). Make sure
> you log your ssh session.

Good idea.