NetworkInterface.GetAllNetworkInterfaces() doesn't list disabled adapters on Windows

[skyoxZ]

Description

On Windows, a disabled network adapter is not listed by NetworkInterface.GetAllNetworkInterfaces().

Reproduction Steps

1. foreach (var ni in System.Net.NetworkInformation.NetworkInterface.GetAllNetworkInterfaces())
   {
       Console.WriteLine(ni.Name + ": " + ni.OperationalStatus);
   }

2. Disable a network adapter.
3. Run the code again.

Expected behavior

The disabled adapter is listed with OperationalStatus.Down.

Actual behavior

The disabled adapter is not listed.

Regression?

No response

Known Workarounds

No response

Configuration

Windows 10
.NET 6 / .NET 7

Other information

No response

[ghost]

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Issue Details

---

Description

On Windows, a disabled network adapter is not listed by NetworkInterface.GetAllNetworkInterfaces().

Reproduction Steps

1. foreach (NetworkInterface ni in NetworkInterface.GetAllNetworkInterfaces())
   {
       Console.WriteLine(ni.Name);
   }

2. Disable a network adapter.
3. Run the code again.

Expected behavior

The disabled adapter is listed with OperationalStatus.Down.

Actual behavior

The disabled adapter is not listed.

Regression?

No response

Known Workarounds

No response

Configuration

Windows 11
.NET 6 / .NET 7

Other information

No response

Author:	skyoxZ
Assignees:	-
Labels:	area-System.Net
Milestone:	-

[karelz]

.NET returns what GetAdapterAddresses OS function gives us back:

runtime/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/SystemNetworkInterface.cs

Lines 103 to 117 in e2b5936

	result = Interop.IpHlpApi.GetAdaptersAddresses(
	family, (uint)flags, IntPtr.Zero, buffer, &bufferSize);
	// If succeeded, we're going to add each new interface.
	if (result == Interop.IpHlpApi.ERROR_SUCCESS)
	{
	// Linked list of interfaces.
	Interop.IpHlpApi.IpAdapterAddresses* adapterAddresses = (Interop.IpHlpApi.IpAdapterAddresses*)buffer;
	while (adapterAddresses != null)
	{
	// Traverse the list, marshal in the native structures, and create new NetworkInterfaces.
	interfaceList.Add(new SystemNetworkInterface(in *adapterAddresses));
	adapterAddresses = adapterAddresses->next;
	}
	}

I assume that the function does not list disabled interfaces and that's why you don't see them.
I am not sure if there is other way for us to query network interfaces from the OS. @wfurt any thoughts?

Not critical for 8.0, moving to Future.

[wfurt]

We should verify what GetAdaptersAddresses returns. If anything, we should make it clear in documentation.

[MojtabaTajik]

@karelz @wfurt

It depends on the "flags" parameter we asked for "GetAdaptersAddresses" The current .Net implementation is:

runtime/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/SystemNetworkInterface.cs

Lines 88 to 91 in e2b5936

	Interop.IpHlpApi.GetAdaptersAddressesFlags flags =
	Interop.IpHlpApi.GetAdaptersAddressesFlags.IncludeGateways
	| Interop.IpHlpApi.GetAdaptersAddressesFlags.IncludeWins;

Based on Windows API docs, we need to pass "GAA_FLAG_INCLUDE_ALL_INTERFACES" as flag, if we want information of all adapters:

Then the received "IP_ADAPTER_ADDRESSES_LH" structure contains "OperStatus", which indicates the enabled state of the adapter.

[MojtabaTajik]

@wfurt I want to pick this ticket up.

[danmoseley]

What does it do on Linux/Mac?

[wfurt]

I don't think the concept is the same. You can do ifconfig down but it is not quite the same and AFAIK we still list it @danmoseley

[MojtabaTajik]

@wfurt I fixed the issue and updated one of the tests because of that change.

Based on the documentation of GetAdaptersAddresses, this change will retrieve even those addresses associated with adapters not bound to an address family specified in the Family parameter.

If the GAA_FLAG_INCLUDE_ALL_INTERFACES is set, then all NDIS adapters will be retrieved even those addresses associated with adapters not bound to an address family specified in the Family parameter. When this flag is not set, then only the addresses that are bound to an adapter enabled for the address family specified in the Family parameter are returned.

Maybe to make it more fancy, we can add an optional parameter with the default value for backward compatibility like this:

internal static unsafe NetworkInterface[] GetNetworkInterfaces(Interop.IpHlpApi.GetAdaptersAddressesFlags flags =Interop.IpHlpApi.GetAdaptersAddressesFlags.IncludeAllInterfaces)
{
		
}

This modification allows developers to choose interface types according to their preferences while ensuring backward compatibility by providing a default value for the flags parameter.