`NetworkInterface.GetAllNetworkInterfaces()` different behaviour in .net 9 / 10 comapred to .net 8 and earlier

[BornToBeRoot]

Description

Hi,

the NetworkInterface.GetAllNetworkInterfaces() has a different behaviour in .net 9 & .net 10 compared to earlier .net versions (.net 8 and lower).

It will return a lot of adapters that are not listed in ipconfig, ncpa.cpl or Get-NetAdapter, it looks like this are properties that can be configured of the real adapters. It also not possible to filter out the adpaters because they are from the type ethernet or wireless.

Reproduction Steps

using System.Net.NetworkInformation;

Console.WriteLine(".NET Version: " + Environment.Version+ "\n");

Console.WriteLine("NetworkInterface.GetAllNetworkInterfaces()\n\n");

foreach (var adapter in NetworkInterface.GetAllNetworkInterfaces())
{
    Console.WriteLine($"Name: {adapter.Name}");        
}

Compiled for .net 8 / 9 / 10

Expected behavior

Output should be the same as 8 and before. I don't think this are real adapters? At least they are not listed anywhere in the other tools....

Actual behavior

See screenshot above

Regression?

No response

Known Workarounds

No response

Configuration

No response

Other information

Maybe related to this: #89990 ?

[dotnet-policy-service]

Tagging subscribers to this area: @dotnet/ncl
See info in area-owners.md if you want to be subscribed.

[skyoxZ]

Could you try using a tool to list just all normal adapters, including those that are disabled?

[BornToBeRoot]

This is what i get with Get-NetAdapter or netsh:

I found this behaviour using my tool (no code changes in this part after migrating from .NET 8 to .NET 10):

.NET 8 version: https://github.com/BornToBeRoot/NETworkManager/releases/tag/2025.10.18.0
.NET 10 version: https://github.com/BornToBeRoot/NETworkManager/releases/tag/2025.12.20.0

Edit: For me it's reproducable with the code snipped i provided when i compile it agains .net8 & 10

[hez2010]

It's expected. Since .NET 9, GetAllNetworkInterfaces passes GAA_FLAG_INCLUDE_ALL_INTERFACES to GetAdaptersAddresses to retrieve all NDIS interfaces, instead of enabled ones only. This API returns what the OS API returns.

[BornToBeRoot]

@hez2010 thanks for the feedback. Can this be disabled with a parameter or is it possible to get the old behaviour? I don't see a property to filter for. The alternative would be to maintain a blacklist, which i want to avoid -.-

Edit: Doesn't dotnet follow the Open-close-principle? So this would be a breaking change, or?

[hez2010]

Can this be disabled with a parameter or is it possible to get the old behaviour? I don't see a property to filter for. The alternative would be to maintain a blacklist, which i want to avoid -.-

I think it's doable but it will need a new API proposal for that additional parameter.