Windows API for DNS change notification

Question

I am looking for a way to receive a notification whenever the configured DNS server address of a network interface changes, using native Windows APIs (C/C++). For both performance and reaction time reasons, I'd obviously want to avoid polling.

There is, for example, the NotifyIpInterfaceChange API in Iphlpapi.dll. In my tests, it reliably triggers a notification when the host's IP address, subnet mask, or default gateway changes, but not at all when only the DNS addresses change.

My only "solution" up to this point is using WMI event queries, but it actually polls in the background, so to avoid hogging down the system, the polling interval (WQL WITHIN clause) needs to be set to several seconds, which results in a long and annoying delay for my application. Also, for various reasons (which are not the topic of this discussion), I prefer to avoid WMI usage anyway, resorting to it only when there is no other way.

Answer 1

Actual credit for this answer should go to RbMm, but he's not posting the answer and seems to have gone MIA.

To receive DNS change notifications, the only non-polling solution seems to be using the RegNotifyChangeKeyValue WinApi to monitor for changes under the HKLM\SYSTEM\CurrentControlSet\Services\Tcpip[6]\Parameters\Interfaces key. Note that there's separate Tcpip and Tcpip6 keys for IPv4 and IPv6 respectively. Anyway, I've implemented and thoroughly tested the solution since the original suggestion and it works without problems.

A semi-related warning: RegNotifyChangeKeyValue has its non-intuitive peculiarities, and it is unlike most other notification APIs, so be sure to study its docs.