Add IPAddress.IsPrivate() extension method

src/Primitives/Primitives/src/ClickView.Extensions.Primitives.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>netstandard2.0</TargetFramework>
+    <TargetFrameworks>netstandard2.0;net6.0</TargetFrameworks>
     <PackageTags>primitives</PackageTags>
   </PropertyGroup>
 

src/Primitives/Primitives/src/Extensions/IpAddressExtensions.cs

@@ -0,0 +1,64 @@
+namespace ClickView.Extensions.Primitives.Extensions;
+
+using System;
+using System.Collections.Generic;
+using System.Net;
+using System.Net.Sockets;
+
+public static class IpAddressExtensions
+{
+    // Source: https://gist.github.com/angularsen/f77b53ee9966fcd914025e25a2b3a085 (thank you!)
+    /// <summary>
+    /// Returns true if the IP address is in a private range.<br/>
+    /// IPv4: Loopback, link local ("169.254.x.x"), class A ("10.x.x.x"), class B ("172.16.x.x" to "172.31.x.x") and class C ("192.168.x.x").<br/>
+    /// IPv6: Loopback, link local, site local, unique local and private IPv4 mapped to IPv6.<br/>
+    /// </summary>
+    /// <param name="ip">The IP address.</param>
+    /// <returns>True if the IP address was in a private range.</returns>
+    /// <exception cref="NotSupportedException">Thrown if the ip address is not <see cref="AddressFamily.InterNetwork"/> or <see cref="AddressFamily.InterNetworkV6"/></exception>
+    /// <example><code>bool isPrivate = IPAddress.Parse("127.0.0.1").IsPrivate();</code></example>
+    public static bool IsPrivate(this IPAddress ip)
+    {
+        // Map back to IPv4 if mapped to IPv6, for example "::ffff:1.2.3.4" to "1.2.3.4".
+        if (ip.IsIPv4MappedToIPv6)
+            ip = ip.MapToIPv4();
+
+        // Checks loopback ranges for both IPv4 and IPv6.
+        if (IPAddress.IsLoopback(ip))
+            return true;
+
+        // IPv4
+        if (ip.AddressFamily == AddressFamily.InterNetwork)
+            return IsPrivateIPv4(ip.GetAddressBytes());
+
+        // IPv6
+        if (ip.AddressFamily == AddressFamily.InterNetworkV6)
+        {
+            return ip.IsIPv6LinkLocal ||
+#if NET6_0_OR_GREATER
+                   ip.IsIPv6UniqueLocal ||
+#endif
+                   ip.IsIPv6SiteLocal;
+        }
+
+        throw new NotSupportedException(
+            $"IP address family {ip.AddressFamily} is not supported, expected only IPv4 (InterNetwork) or IPv6 (InterNetworkV6).");
+    }
+
+    private static bool IsPrivateIPv4(IReadOnlyList<byte> ipv4Bytes)
+    {
+        return IsLinkLocal() || IsClassA() || IsClassC() || IsClassB();
+
+        // Class C private range: 192.168.0.0 – 192.168.255.255 (192.168.0.0/16)
+        bool IsClassC() => ipv4Bytes[0] == 192 && ipv4Bytes[1] == 168;
+
+        // Class B private range: 172.16.0.0 – 172.31.255.255 (172.16.0.0/12)
+        bool IsClassB() => ipv4Bytes[0] == 172 && ipv4Bytes[1] >= 16 && ipv4Bytes[1] <= 31;
+
+        // Class A private range: 10.0.0.0 – 10.255.255.255 (10.0.0.0/8)
+        bool IsClassA() => ipv4Bytes[0] == 10;
+
+        // Link local (no IP assigned by DHCP): 169.254.0.0 to 169.254.255.255 (169.254.0.0/16)
+        bool IsLinkLocal() => ipv4Bytes[0] == 169 && ipv4Bytes[1] == 254;
+    }
+}

src/Primitives/Primitives/test/Extensions/IpAddressExtensionsTests.cs

@@ -0,0 +1,113 @@
+namespace ClickView.Extensions.Primitives.Tests.Extensions;
+
+using System.Net;
+using Primitives.Extensions;
+using Xunit;
+
+// Thanks https://gist.github.com/angularsen/f77b53ee9966fcd914025e25a2b3a085
+public class IpAddressExtensionsTests
+{
+    [Theory]
+    [InlineData("1.1.1.1")] // Cloudflare DNS
+    [InlineData("8.8.8.8")] // Google DNS
+    [InlineData("20.112.52.29")] // microsoft.com
+    public void IsPrivate_PublicIPv4_ReturnsFalse(string ip)
+    {
+        var ipAddress = IPAddress.Parse(ip);
+
+        Assert.False(ipAddress.IsPrivate());
+    }
+
+    [Theory]
+    [InlineData("::ffff:1.1.1.1")] // Cloudflare DNS
+    [InlineData("::ffff:8.8.8.8")] // Google DNS
+    [InlineData("::ffff:20.112.52.29")] // microsoft.com
+    public void IsPrivate_PublicIPv4MappedToIPv6_ReturnsFalse(string ip)
+    {
+        var ipAddress = IPAddress.Parse(ip);
+
+        Assert.False(ipAddress.IsPrivate());
+    }
+
+    [Theory]
+    // Loopback IPv4 127.0.0.1 - 127.255.255.255 (127.0.0.0/8)
+    [InlineData("127.0.0.1")]
+    [InlineData("127.10.20.30")]
+    [InlineData("127.255.255.255")]
+    // Class A private IP 10.0.0.0 – 10.255.255.255 (10.0.0.0/8)
+    [InlineData("10.0.0.0")]
+    [InlineData("10.20.30.40")]
+    [InlineData("10.255.255.255")]
+    // Class B private IP 172.16.0.0 – 172.31.255.255 (172.16.0.0/12)
+    [InlineData("172.16.0.0")]
+    [InlineData("172.20.30.40")]
+    [InlineData("172.31.255.255")]
+    // Class C private IP 192.168.0.0 – 192.168.255.255 (192.168.0.0/16)
+    [InlineData("192.168.0.0")]
+    [InlineData("192.168.30.40")]
+    [InlineData("192.168.255.255")]
+    // Link local (169.254.x.x)
+    [InlineData("169.254.0.0")]
+    [InlineData("169.254.30.40")]
+    [InlineData("169.254.255.255")]
+    public void IsPrivate_PrivateIPv4_ReturnsTrue(string ip)
+    {
+        var ipAddress = IPAddress.Parse(ip);
+
+        Assert.True(ipAddress.IsPrivate());
+    }
+
+    [Theory]
+    // Loopback IPv4 127.0.0.1 - 127.255.255.254 (127.0.0.0/8)
+    [InlineData("::ffff:127.0.0.1")]
+    [InlineData("::ffff:127.10.20.30")]
+    [InlineData("::ffff:127.255.255.254")]
+    // Class A private IP 10.0.0.0 – 10.255.255.255 (10.0.0.0/8)
+    [InlineData("::ffff:10.0.0.0")]
+    [InlineData("::ffff:10.20.30.40")]
+    [InlineData("::ffff:10.255.255.255")]
+    // Class B private IP 172.16.0.0 – 172.31.255.255 (172.16.0.0/12)
+    [InlineData("::ffff:172.16.0.0")]
+    [InlineData("::ffff:172.20.30.40")]
+    [InlineData("::ffff:172.31.255.255")]
+    // Class C private IP 192.168.0.0 – 192.168.255.255 (192.168.0.0/16)
+    [InlineData("::ffff:192.168.0.0")]
+    [InlineData("::ffff:192.168.30.40")]
+    [InlineData("::ffff:192.168.255.255")]
+    // Link local (169.254.x.x)
+    [InlineData("::ffff:169.254.0.0")]
+    [InlineData("::ffff:169.254.30.40")]
+    [InlineData("::ffff:169.254.255.255")]
+    public void IsPrivate_PrivateIPv4MappedToIPv6_ReturnsTrue(string ip)
+    {
+        var ipAddress = IPAddress.Parse(ip);
+
+        Assert.True(ipAddress.IsPrivate());
+    }
+
+    [Theory]
+    [InlineData("::1")] // Loopback
+    [InlineData("fe80::")] // Link local
+    [InlineData("fe80:1234:5678::1")] // Link local
+    [InlineData("fc00::")] // Unique local, globally assigned.
+    [InlineData("fc00:1234:5678::1")] // Unique local, globally assigned.
+    [InlineData("fd00::")] // Unique local, locally assigned.
+    [InlineData("fd12:3456:789a::1")] // Unique local, locally assigned.
+    public void IsPrivate_PrivateIPv6_ReturnsTrue(string ip)
+    {
+        var ipAddress = IPAddress.Parse(ip);
+
+        Assert.True(ipAddress.IsPrivate());
+    }
+
+    [Theory]
+    [InlineData("2606:4700:4700::64")] // Cloudflare DNS
+    [InlineData("2001:4860:4860::8888")] // Google DNS
+    [InlineData("2001:0db8:85a3:0000:0000:8a2e:0370:7334")] // Commonly used example.
+    public void IsPrivate_PublicIPv6_ReturnsFalse(string ip)
+    {
+        var ipAddress = IPAddress.Parse(ip);
+
+        Assert.False(ipAddress.IsPrivate());
+    }
+}