IPAddress.IsLoopBack returns false for ::ffff:127.0.0.1

[oliverholliday]

Local connections to an aspnetcore app running on win10 have the HttpContext.Connection.RemoteIpAddress property set to ::ffff:127.0.0.1.

The IPAddress.IsLoopBack() method returns false for this address - the method checks for IPv6 and IPv4 loopback addresses but doesn't check a loopback IPv4 address mapped to IPv6. I believe this is confusing.

https://github.com/dotnet/corefx/blob/master/src/System.Net.Primitives/src/System/Net/IPAddress.cs#L418

I worked around this by doing:

IPAddress.IsLoopback(address.IsIPv4MappedToIPv6 ? address.MapToIPv4() : address)