API proposal: Mask testing for IPAddress

[huoyaoyuan]

Background and Motivation

From #42840
A weird workaround is used for mask testing. Masking should be exposed as a direct concept for ip addresses.

Proposed API

namespace System.Net
{
    public class IPAddress
    {
+        public bool IsMask(IPAddress address, int maskLength);
    }
}

Usage Examples

var mask = IPAddress.Parse("192.168.0.0");
var address = IPAddress.Parse("192.168.1.1");
Assert.True(mask.IsMask(address, 16));

Alternative Designs

Expose a separated IPAddressMask type? Then mask length doesn't needed to be passed in every call.

Risks

Is storing masks violating the IPAddress type? If so, an IPAddressMask type should be appropriate.

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[scalablecory]

Would this check if an IPAddress is exactly equal to a mask, or only that the IP address is within the mask?

[wfurt]

note that mask operations are obsolete in IPv6. There was similar CIDR proposal which did not fly.

[karelz]

Given that this is IPv4 only feature and the world is moving towards IPv6, I wonder if this makes sense at all ... should we just close it as Won't Fix?

[alrz]

Does a IPAddressRange API fit into this bucket? There's https://www.nuget.org/packages/IPAddressRange with horrendous impl that I wouldn't want to use.

[MihaZupan]

Have you considered contributing a better implementation that would be acceptable?

[alrz]

That's a complete rewrite. I did implement a simple one just to use Contains - no parsing or validation though.

[antonfirsov]

Unless there are valid concerns, I recommend to close this in favor of #79946.

[ghost]

This issue has been marked needs-author-action and may be missing some important information.

[huoyaoyuan]

Agreed to close in favor of #79946.