DNS lookups for devices on the local network

Allow for the ability for the Eero router to provide DNS resolution of local devices.

In other words, a DNS query sent to the Eero router requesting a hostname or IP of a device on the local network would be handled locally rather than just passing the request to the upstream DNS server.

With the Eero acting as the network's DHCP server, it already knows which device MAC addresses have which IPs.  It can also obtain a hostname from the host during DHCP negotiations or, at minimum, get a hostname from the DHCP reservations section. Then, a request by hostname or IP - presuming such an entry for that pair existed - would return the appropriate information.

Requests for FQDNs or IPs outside of the local network would get passed along to the upstream DNS servers.

Being able to access local network devices by name is a lot easier than referencing the Eero app for IP assignments or maintaining a spreadsheet.  It also covers environments or devices that don't support Bonjour/mDNS.

This should work whether Secure(+) features are enabled or not.