Move IsInternal() method to extension

DearFTP/Connection/Commands/PassiveCommand.cs

@@ -1,4 +1,5 @@
-using System;
+using DearFTP.Utils.Extensions;
+using System;
 using System.Linq;
 using System.Net;
 
@@ -20,7 +21,7 @@ namespace DearFTP.Connection.Commands
 
             string remote;
 
-            if (IsInternal(session.RemoteIP))
+            if (session.RemoteIP.IsInternal())
             {
                 remote = string.Join(',', session.LocalIP.ToString().Split('.').Concat(portBytes));
             }
@@ -33,27 +34,5 @@ namespace DearFTP.Connection.Commands
 
             session.DataConnection.AcceptClient();
         }
-
-        // Source: https://stackoverflow.com/a/39120248
-        /// <summary>
-        /// An extension method to determine if an IP address is internal, as specified in RFC1918
-        /// </summary>
-        /// <param name="toTest">The IP address that will be tested</param>
-        /// <returns>Returns true if the IP is internal, false if it is external</returns>
-        public bool IsInternal(IPAddress toTest)
-        {
-            byte[] bytes = toTest.GetAddressBytes();
-            switch (bytes[0])
-            {
-                case 10:
-                    return true;
-                case 172:
-                    return bytes[1] < 32 && bytes[1] >= 16;
-                case 192:
-                    return bytes[1] == 168;
-                default:
-                    return false;
-            }
-        }
     }
 }

DearFTP/Utils/Extensions/IPAddressExtensions.cs

@@ -0,0 +1,32 @@
+using System;
+using System.Collections.Generic;
+using System.Net;
+using System.Text;
+
+namespace DearFTP.Utils.Extensions
+{
+    public static class IPAddressExtensions
+    {
+        // Source: https://stackoverflow.com/a/39120248
+        /// <summary>
+        /// An extension method to determine if an IP address is internal, as specified in RFC1918
+        /// </summary>
+        /// <param name="toTest">The IP address that will be tested</param>
+        /// <returns>Returns true if the IP is internal, false if it is external</returns>
+        public static bool IsInternal(this IPAddress toTest)
+        {
+            byte[] bytes = toTest.GetAddressBytes();
+            switch (bytes[0])
+            {
+                case 10:
+                    return true;
+                case 172:
+                    return bytes[1] < 32 && bytes[1] >= 16;
+                case 192:
+                    return bytes[1] == 168;
+                default:
+                    return false;
+            }
+        }
+    }
+}