I am running a full-tunnel VPN using a Packet Tunnel Provider. During VPN setup, we configure DNS setting with specific DNS servers for all domains to be used by the tunnel. However, our project requires DNS resolution for every domain from both the VPN-provided DNS servers and the ISP’s DNS servers.
When I attempt to use c-ares or other third-party libraries to resolve domains via the ISP DNS servers, these libraries only detect and use the VPN DNS servers instead. As a result, all queries fail.
Is there a way on iOS to programmatically determine the ISP DNS servers while a full-tunnel VPN is active, or a system API that allows DNS queries to be explicitly resolved using the ISP’s DNS servers?