fix: Exempts localhost from IPLimiter. Preps testing for io_uring (#2316)

### Summary
* Exempts localhost from IPLimiter
* Updates tests to have proper sequential testing with packets
* Updates tests to clean up NetState

Projects/Server/Network/IPRateLimiter.cs

@@ -56,6 +56,12 @@ public class IPRateLimiter
 
     public bool Verify(IPAddress ip, out int totalAttempts)
     {
+        if (ip.IsPrivateNetwork())
+        {
+            totalAttempts = 0;
+            return true;
+        }
+
         var nowTicks = Core.TickCount;
         var ipStats = _ipAttempts.GetOrAdd(ip, _ => GetOrCreateIPStats());
         var added = ipStats.AttemptCount == 0;

Projects/Server/Network/NetState/NetState.cs

@@ -35,7 +35,7 @@ namespace Server.Network;
 public delegate void DecodePacket(Span<byte> buffer, ref int length);
 public delegate int EncodePacket(ReadOnlySpan<byte> inputBuffer, Span<byte> outputBuffer);
 
-public partial class NetState : IComparable<NetState>, IValueLinkListNode<NetState>
+public partial class NetState : IComparable<NetState>, IValueLinkListNode<NetState>, IDisposable
 {
     private static readonly ILogger logger = LogFactory.GetLogger(typeof(NetState));
 
@@ -1142,8 +1142,11 @@ public partial class NetState : IComparable<NetState>, IValueLinkListNode<NetSta
         }
     }
 
-    private void Dispose()
+    // Do not run this directly. Use Disconnect instead.
+    // This is available for testing cleanup only.
+    public void Dispose()
     {
+        _running = false;
         // It's possible we could queue for dispose multiple times
         if (Connection == null)
         {

Projects/Server/Utilities/NetworkUtilities.cs

@@ -0,0 +1,49 @@
+using System.Net;
+using System.Net.Sockets;
+using Server.Network;
+
+namespace Server;
+
+public static class NetworkUtilities
+{
+    public static bool IsPrivateNetwork(this IPAddress ip) =>
+        ip.AddressFamily switch
+        {
+            AddressFamily.InterNetwork   => ip.IsPrivateNetworkV4(),
+            AddressFamily.InterNetworkV6 => ip.IsPrivateNetworkV6(),
+            _                            => false
+        };
+
+    private static readonly IFirewallEntry[] _privateNetworkV4 =
+    [
+        new CidrFirewallEntry("127.0.0.1/8"),
+        new CidrFirewallEntry("192.168.0.0/16"),
+        new CidrFirewallEntry("10.0.0.0/8"),
+        new CidrFirewallEntry("172.16.0.0/12"),
+        new CidrFirewallEntry("169.254.0.0/16"),
+        new CidrFirewallEntry("100.64.0.0/10")
+    ];
+
+    private static readonly IFirewallEntry[] _privateNetworkV6 =
+    [
+        new CidrFirewallEntry("fc00::/7"),
+        new CidrFirewallEntry("fe80::/10")
+    ];
+
+    public static bool IsPrivateNetworkV4(this IPAddress ip)
+    {
+        for (var i = 0; i < _privateNetworkV4.Length; i++)
+        {
+            if (_privateNetworkV4[i].IsBlocked(ip))
+            {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    public static bool IsPrivateNetworkV6(this IPAddress ip) =>
+        _privateNetworkV6[0].IsBlocked(ip) ||
+        _privateNetworkV6[1].IsBlocked(ip);
+}