[Dnsmasq-discuss] DHCPOFFER rejected?

[Simon Kelley]

On 12/06/14 04:01, Bill Johnson wrote:
> A new wifi enabled thermostat has me baffled.
> 
> dnsmasq provides dhcp and dns services to my home network, on a machine
> named "wardrobe" at 192.168.1.1.  Wardrobe also does routing for the
> network.  Wardrobe runs Ubuntu 12.04 and dnsmasq 2.59.  Wifi "routers"
> do no routing. They are access points only.
> 
> I recently acquired a wifi enabled thermostat.  Out of the box, this
> thing starts up its own wifi net with a unique SSID, and advertises a
> web server at 192.168.1.1.  The server allows the user to tell the
> device which SSID to connect to, and to provide a password for that
> network.  So, this thing broadcasts DHCPDISCOVER, wardrobe responds with
> DHCPOFFER, and the dance breaks off, then repeats for a while, then the
> thermostat reports "No IP Address", then starts trying again.
> Here's what dnsmasq logs, over and over again:
> 
> Jun 11 22:22:32 wardrobe dnsmasq-dhcp[17562]: 162797508 available DHCP
> range: 192.168.1.100 -- 192.168.1.199
> Jun 11 22:22:32 wardrobe dnsmasq-dhcp[17562]: 162797508 client provides
> name: Gateway3CDA93
> Jun 11 22:22:32 wardrobe dnsmasq-dhcp[17562]: 162797508
> DHCPDISCOVER(eth1) 00:d0:2d:3c:da:93
> Jun 11 22:22:32 wardrobe dnsmasq-dhcp[17562]: 162797508 tags: eth1
> Jun 11 22:22:32 wardrobe dnsmasq-dhcp[17562]: 162797508 DHCPOFFER(eth1)
> 192.168.1.191 00:d0:2d:3c:da:93
> Jun 11 22:22:32 wardrobe dnsmasq-dhcp[17562]: 162797508 requested
> options: 1:netmask, 3:router, 6:dns-server
> Jun 11 22:22:32 wardrobe dnsmasq-dhcp[17562]: 162797508 next server:
> 192.168.1.1
> Jun 11 22:22:32 wardrobe dnsmasq-dhcp[17562]: 162797508 broadcast response
> Jun 11 22:22:32 wardrobe dnsmasq-dhcp[17562]: 162797508 sent size:  1
> option: 53:message-type  02
> Jun 11 22:22:32 wardrobe dnsmasq-dhcp[17562]: 162797508 sent size:  4
> option: 54:server-identifier  192.168.1.1
> Jun 11 22:22:32 wardrobe dnsmasq-dhcp[17562]: 162797508 sent size:  4
> option: 51:lease-time  00:00:a8:c0
> Jun 11 22:22:32 wardrobe dnsmasq-dhcp[17562]: 162797508 sent size:  4
> option: 58:T1  00:00:54:60
> Jun 11 22:22:32 wardrobe dnsmasq-dhcp[17562]: 162797508 sent size:  4
> option: 59:T2  00:00:93:a8
> Jun 11 22:22:32 wardrobe dnsmasq-dhcp[17562]: 162797508 sent size:  4
> option:  1:netmask  255.255.0.0
> Jun 11 22:22:32 wardrobe dnsmasq-dhcp[17562]: 162797508 sent size:  4
> option: 28:broadcast  192.168.255.255
> Jun 11 22:22:32 wardrobe dnsmasq-dhcp[17562]: 162797508 sent size:  4
> option:  3:router  192.168.1.1
> Jun 11 22:22:32 wardrobe dnsmasq-dhcp[17562]: 162797508 sent size:  4
> option:  6:dns-server  192.168.1.1
> 
> I'm mystified.  dnsmasq seems to be sending everything the thermostat
> has requested, but the thermostat never sends DHCPREQUEST.  The
> thermostat is something of a black box, and "technical support" is
> useless.  Any ideas would be very welcome.
> 

Can you make it work with another DHCP server (ie, does the useless
technical support specify a server to use? If you can get it to work
with that server and grab the packets, we could see what's missing from
dnsmasq's answer and work out how to configure it to please the thermostat.


Simon.