[Dnsmasq-discuss] DHCPOFFER rejected?

[Bill Johnson]

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.

-- Bill Johnson