[System.Net] Introduce CIDR IPNetwork

src/libraries/System.Net.Primitives/ref/System.Net.Primitives.cs

@@ -287,6 +287,32 @@ public IPEndPoint(System.Net.IPAddress address, int port) { }
         public static bool TryParse(System.ReadOnlySpan<char> s, [System.Diagnostics.CodeAnalysis.NotNullWhenAttribute(true)] out System.Net.IPEndPoint? result) { throw null; }
         public static bool TryParse(string s, [System.Diagnostics.CodeAnalysis.NotNullWhenAttribute(true)] out System.Net.IPEndPoint? result) { throw null; }
     }
+    public readonly partial struct IPNetwork : System.IEquatable<System.Net.IPNetwork>, System.IFormattable, System.IParsable<System.Net.IPNetwork>, System.ISpanFormattable, System.ISpanParsable<System.Net.IPNetwork>
+    {
+        private readonly object _dummy;
+        private readonly int _dummyPrimitive;
+        public IPNetwork(System.Net.IPAddress baseAddress, int prefixLength) { throw null; }
+        public System.Net.IPAddress BaseAddress { get { throw null; } }
+        public int PrefixLength { get { throw null; } }
+        public bool Contains(System.Net.IPAddress address) { throw null; }
+        public bool Equals(System.Net.IPNetwork other) { throw null; }
+        public override bool Equals([System.Diagnostics.CodeAnalysis.NotNullWhenAttribute(true)] object? obj) { throw null; }
+        public override int GetHashCode() { throw null; }
+        public static bool operator ==(System.Net.IPNetwork left, System.Net.IPNetwork right) { throw null; }
+        public static bool operator !=(System.Net.IPNetwork left, System.Net.IPNetwork right) { throw null; }
+        public static System.Net.IPNetwork Parse(System.ReadOnlySpan<char> s) { throw null; }
+        public static System.Net.IPNetwork Parse(string s) { throw null; }
+        string System.IFormattable.ToString(string? format, System.IFormatProvider? provider) { throw null; }
+        static System.Net.IPNetwork System.IParsable<System.Net.IPNetwork>.Parse([System.Diagnostics.CodeAnalysis.NotNullAttribute] string s, System.IFormatProvider? provider) { throw null; }
+        static bool System.IParsable<System.Net.IPNetwork>.TryParse([System.Diagnostics.CodeAnalysis.NotNullWhenAttribute(true)] string? s, System.IFormatProvider? provider, out System.Net.IPNetwork result) { throw null; }
+        bool System.ISpanFormattable.TryFormat(System.Span<char> destination, out int charsWritten, System.ReadOnlySpan<char> format, System.IFormatProvider? provider) { throw null; }
+        static System.Net.IPNetwork System.ISpanParsable<System.Net.IPNetwork>.Parse(System.ReadOnlySpan<char> s, System.IFormatProvider? provider) { throw null; }
+        static bool System.ISpanParsable<System.Net.IPNetwork>.TryParse(System.ReadOnlySpan<char> s, System.IFormatProvider? provider, out System.Net.IPNetwork result) { throw null; }
+        public override string ToString() { throw null; }
+        public bool TryFormat(System.Span<char> destination, out int charsWritten) { throw null; }
+        public static bool TryParse(System.ReadOnlySpan<char> s, out System.Net.IPNetwork result) { throw null; }
+        public static bool TryParse(string? s, out System.Net.IPNetwork result) { throw null; }
+    }
     public partial interface IWebProxy
     {
         System.Net.ICredentials? Credentials { get; set; }

src/libraries/System.Net.Primitives/src/Resources/Strings.resx

@@ -78,6 +78,15 @@
   <data name="dns_bad_ip_address" xml:space="preserve">
     <value>An invalid IP address was specified.</value>
   </data>
+  <data name="net_bad_ip_network" xml:space="preserve">
+    <value>An invalid IP network was specified.</value>
+  </data>
+  <data name="net_bad_ip_network_invalid_baseaddress" xml:space="preserve">
+    <value>The specified baseAddress has non-zero bits after the network prefix.</value>
+  </data>
+  <data name="net_uninitialized_ip_network_instance" xml:space="preserve">
+    <value>Uninitialized IPNetwork instance.</value>
+  </data>
   <data name="net_container_add_cookie" xml:space="preserve">
     <value>An error occurred when adding a cookie to the container.</value>
   </data>

src/libraries/System.Net.Primitives/src/System.Net.Primitives.csproj

@@ -28,6 +28,7 @@
     <Compile Include="System\Net\ICredentials.cs" />
     <Compile Include="System\Net\ICredentialsByHost.cs" />
     <Compile Include="System\Net\IPAddress.cs" />
+    <Compile Include="System\Net\IPNetwork.cs" />
     <Compile Include="System\Net\IPAddressParser.cs" />
     <Compile Include="System\Net\IPEndPoint.cs" />
     <Compile Include="$(CommonPath)System\Net\IPv4AddressHelper.Common.cs"

src/libraries/System.Net.Primitives/src/System/Net/IPAddress.cs

@@ -69,14 +69,14 @@ private bool IsIPv6
             get { return _numbers != null; }
         }
 
-        private uint PrivateAddress
+        internal uint PrivateAddress
         {
             get
             {
                 Debug.Assert(IsIPv4);
                 return _addressOrScopeId;
             }
-            set
+            private set
             {
                 Debug.Assert(IsIPv4);
                 _toString = null;