I'd like to use ConnMan in a device that connects to an Ethernet network, and 
also (optionally) can operate Wi-Fi in access point mode to provide technician 
type access to itself.

So it looks like "tethering" is the way to do a Wi-Fi access point. But in this 
use case, I don't want Wi-Fi tethering to permit access to upstream connections 
(the wired Ethernet). I can easily achieve that by adding a firewall with 
FORWARD rule set to DROP.

However, I also want to lock down DNS. Even with forwarding stopped, a Wi-Fi 
client can still do DNS look-ups through the upstream connection, thus 
providing a back channel of communication.

Secondly, I'd also like Wi-Fi clients to be able to access the device via a DNS 
name, such as my-serial-number.lan. I'm not sure how to configure a DNS server 
for the tether interface.

Related to this: maybe I could run a DNS server, getting the tether interface's 
IP address updates through D-Bus. But as I've seen with connmanctl monitor, 
tether IP address doesn't seem to be notified on D-Bus.

In summary, these questions:

1) How could the tether interface's DNS look-ups through upstream be restricted?
2) How could a DNS server be provided for the tether interface, which responds 
to my-serial-number.lan with the tether interface's current IP address?
3) How can notifications of tether interface's IP address changes be obtained 
via D-Bus?

(Note: I found an older post to this mailing list, "Connman tethering landing 
page (or single dns record pointing back to itself)". Essentially the same 
objective re DNS. Zeroconf mDNS isn't a sufficient solution, due to limited 
support in Windows and Android.)

-- 
Craig McQueen

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