[Dnsmasq-discuss] iPhones not getting proper dhcp

[Jeff Boyce]

Thanks for the response Andras

I was unfamiliar with MAC address randomization, but after learning 
about it and checking the logs over the last week I can see that the MAC 
address for an iOS client is not being changed.

I have done some more investigation and am more certain this is a dhcp 
(client?) issue, but I don't see anything indicating that it is a 
dnsmasq issue.  I will explain further what I am seeing from a Wireshark 
capture on the dnsmasq server.

1.  iPhone Client broadcasts a DHCP Discover (source IP 0.0.0.0, 
destination IP 255.255.255.255)
    a.  Client MAC address identifies it as the iPhone that has had 
previous issues connecting.

2.  DHCP Server replies to the iPhone Client with a DHCP Offer (source 
IP 192.168.112.51, destination IP 192.168.112.202)
    a.  The destination IP, lease time, and other DHCP options correctly 
match the DHCP configuration

3.  The DHCP Discover and DHCP Offer repeat numerous times during a 
1-minute period.

4.  The iPhone Client never sends a DHCP Request back to the Server.

5.  After approximately 1-minute I can see in the web interface for my 
wireless access point that the iPhone assigns itself a Link-Local 
address in the 169.254.0.0/16 address range.

I have tried assigning a static IP address in dnsmasq for this client 
based on it's MAC address and it is correctly picked up and used by 
dnsmasq for the DHCP Offer.

Watching the dhcp log files and the wireless AP web interface, I have 
seen this iPhone on a few occasions be assigned the correct LAN IP 
address (can see DHCP Requests and DHCP Acks), however it does not stay 
longer than a minute or so.  In the logs I have also seen the iPhone 
client give a DHCP Request for an address in the 10.0.0.0/24 range, and 
the DHCP Server responds with a DHCP NAK, wrong address.  The iPhone 
user does not know if the 10.0.0.0/24 address range is their home network.

Also, to be clear the issue occurs with all the iPhones in the office 
and is not just isolated to this one that I am testing with.

Any other suggestions or ideas.  Let me know if there is a better list 
to send this to, since I don't think the issue is dnsmasq related.  Thanks.

Jeff



On 8/25/2017 2:13 AM, Andras Salamon wrote:
> Jeff,
>
> On 2017-08-24 13:47:28 -0700, you wrote:
>> I have an issue in our office where the iPhones are not able to 
>> receive an internet connection through our wireless access point.
>
> Is this perhaps related to MAC address randomization that was introduced
> in iOS a while back, interacting badly with the DHCP server?
>
> -- Andras Salamon                   andras at gaon.net
>
>

-- 

Jeff Boyce
Meridian Environmental