windows c++ change windows DNS server with SetInterfaceDnsSettings/GetInterfaceDnsSettings?

Question

I'm looking for a way to change DNS using C++.

The official document I came across is https://learn.microsoft.com/en-us/windows/win32/api/netioapi/nf-netioapi-setinterfacednssettings

But it gives no examples.

The other method I found is

change registry C++ Add DNS entry into network adapter

Not what I need.
C# example How do I change/set DNS with c++?

Funy, there is even a C# example, but no c++.
This method kinda execute some system commands I guess, https://github.com/w123l123h/netConfig

Not what I want neither.

I know I can easily achieve the goal by calling netsh command.

But, is there some workable examples for SetInterfaceDnsSettings/GetInterfaceDnsSettings

This is my sample code, the returned ret value is always 87, NameServer is NULl.

The interfaceGUID is got from GetAdaptersInfo() api.

void get_dns()
{
     GUID interfaceGUID = {0xFD113810, 0x2F5A, 0x4947, {0xA1, 0x19, 0xA5, 0xC9, 0x74, 0x15, 0x88, 0x26}};

     DNS_INTERFACE_SETTINGS *settings;
     DWORD ret = GetInterfaceDnsSettings(interfaceGUID, settings);
     printf("result: %lu\n", ret);
     printf("NameServer: %ls\n", settings->NameServer);
}

Follow up question.

SetInterfaceDnsSettings() does not work.

This my code.

GUID interfaceGUID;
    LPCOLESTR lpsz = L"{1CA18531-B5FA-4A92-837A-AE12298FFF7F}";
    HRESULT hr = CLSIDFromString(lpsz, &interfaceGUID);
    if (hr != S_OK)
    {
        printf("get guid error!!!\n");
        exit(1);
    }

    DNS_INTERFACE_SETTINGS settings = { DNS_INTERFACE_SETTINGS_VERSION1 };
    settings.NameServer = L"8.8.8.8";
    printf("NameServer: %ls\n", settings.NameServer);

    DWORD ret = SetInterfaceDnsSettings(interfaceGUID, &settings);
    printf("result: %lu\n", ret);

The ret value returned is 0, I guess it means no error.

But it did not change the DNS of the interface. Whether it's got from GetInterfaceDnsSettings or Control Panel.

I never used this API, but I would imagine that there's nothing more to it than `Get`ting the respective settings, making modifications, and `Set`ting them back. What's the specific issue you're having? — IInspectable, Jun 21 '23 at 10:41
Passing an uninitialized pointer value isn't going to have well-defined behavior. — IInspectable, Jun 21 '23 at 11:19
That's the problem, I don't know how to init it, and there is no document about it. — Gary Allen, Jun 21 '23 at 11:33
`DNS_INTERFACE_SETTINGS settings = { DNS_INTERFACE_SETTINGS_VERSION1 }; GetInterfaceDnsSettings(interfaceGUID, &settings);` — IInspectable, Jun 21 '23 at 11:37
@IInspectable GetInterfaceDnsSettings() works, But SetInterfaceDnsSettings() doesn't. — Gary Allen, Jun 26 '23 at 03:21
The latter likely requires privileges that a regular user account doesn't hold. Try running the code under an administrative account. — IInspectable, Jun 26 '23 at 07:19
Just noticed the update to the question. There's a bug in populating the structure. When calling `SetInterfaceDnsSettings` you will have to provide `Flags` that describe the settings that hold valid data/need to be updated. In this case `Flags` needs to have the `DNS_SETTING_NAMESERVER` bit set. — IInspectable, Jun 26 '23 at 07:28

score 0 · Accepted Answer · answered Jul 06 '23 at 03:28

According to @IInspectable's comments, I summarize this question.

DNS_INTERFACE_SETTINGS needs to be properly initialized. When using SetInterfaceDnsSettings, you need to declare Flags that you need to modify property in the DNS_INTERFACE_SETTINGS.

DNS_INTERFACE_SETTINGS settings;
settings.Version = DNS_INTERFACE_SETTINGS_VERSION1;
settings.Flags = DNS_SETTING_NAMESERVER ;
settings.NameServer = L"8.8.8.8";

DWORD ret = SetInterfaceDnsSettings(interfaceGUID, &settings);
printf("result: %lu\n", ret);

windows c++ change windows DNS server with SetInterfaceDnsSettings/GetInterfaceDnsSettings?

1 Answers1