[Dnsmasq-discuss] Shut down caused by device request address.

[Colin Finnis]

I have been running dnsmasq for some time on a Raspberry PI. I had no
problems until about 18 months ago when the DNS would suddenly stop working.
I found these types of entries in the syslog.

 

Feb 21 16:14:07 pilot dnsmasq-dhcp[2061]: DHCPACK(eth0) 192.168.0.242
02:ef:dd:91:3a:f3 Wild-s-S21

Feb 21 16:14:09 pilot dnsmasq-dhcp[2061]: DHCPREQUEST(eth0) 192.168.0.242
02:ef:dd:91:3a:f3 

Feb 21 16:14:09 pilot dnsmasq-dhcp[2061]: DHCPACK(eth0) 192.168.0.242
02:ef:dd:91:3a:f3 Wild-s-S21

Feb 21 16:14:09 pilot dhcpcd[377]: eth0: hardware address 02:ef:dd:91:3a:f3
claims 192.168.0.8

Feb 21 16:14:10 pilot dhcpcd[377]: eth0: hardware address 02:ef:dd:91:3a:f3
claims 192.168.0.8

Feb 21 16:14:10 pilot dhcpcd[377]: eth0: 10 second defence failed for
192.168.0.8

Feb 21 16:14:10 pilot dhcpcd[377]: eth0: deleting route to 192.168.0.0/24

Feb 21 16:14:10 pilot dhcpcd[377]: eth0: deleting default route via
192.168.0.1

Feb 21 16:14:10 pilot avahi-daemon[279]: Withdrawing address record for
192.168.0.8 on eth0.

 

The problem always seems to be associated with Samsung phones and appears to
have started after an update to the phone around 18 months ago. I have found
what purports to be a solution which requires a setting change on the phone.
This is fine for my phone but visitors to my house can cause the same
problem and its difficult to get them all to change before the damage is
done. It dosnt always happens when the phone is brought into the house, I
think it occur when the phone is close to the property and the signal is
poor.

 

As you can see the request is made for an address and the DNS responds. The
request is made a second time and immediately the device seems to take over
the IP address of the DNS box. DHCPD then goes into some sort of defence
mode and avahi withdraws the statically assigned address. I have tried
changing the address of the DNS server in case it was just the phone using a
random address but that made no difference. I cant run a network monitor on
the traffic so I cant see what is happen during this event. It just sems
strange behaviour for the phone to suddenly decide its going to usurp the
DNS's IP address.

 

Im technically savvy having worked in the IT industry for 40 years but cant
work out away to either prevent this or stop it happening. The only way at
the moment is to reboot the PI. Any help would be appreciated.

 

Colin Finnis

 

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