alap

Assets/Mirror/Transports/KCP/kcp2k/highlevel/Common.cs

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+using System;
+using System.Net;
+using System.Net.Sockets;
+using System.Security.Cryptography;
+
+namespace kcp2k
+{
+    public static class Common
+    {
+        // helper function to resolve host to IPAddress
+        public static bool ResolveHostname(string hostname, out IPAddress[] addresses)
+        {
+            try
+            {
+                // NOTE: dns lookup is blocking. this can take a second.
+                addresses = Dns.GetHostAddresses(hostname);
+                return addresses.Length >= 1;
+            }
+            catch (SocketException exception)
+            {
+                Log.Info($"[KCP] Failed to resolve host: {hostname} reason: {exception}");
+                addresses = null;
+                return false;
+            }
+        }
+
+        // if connections drop under heavy load, increase to OS limit.
+        // if still not enough, increase the OS limit.
+        public static void ConfigureSocketBuffers(Socket socket, int recvBufferSize, int sendBufferSize)
+        {
+            // log initial size for comparison.
+            // remember initial size for log comparison
+            int initialReceive = socket.ReceiveBufferSize;
+            int initialSend    = socket.SendBufferSize;
+
+            // set to configured size
+            try
+            {
+                socket.ReceiveBufferSize = recvBufferSize;
+                socket.SendBufferSize    = sendBufferSize;
+            }
+            catch (SocketException)
+            {
+                Log.Warning($"[KCP] failed to set Socket RecvBufSize = {recvBufferSize} SendBufSize = {sendBufferSize}");
+            }
+
+
+            Log.Info($"[KCP] RecvBuf = {initialReceive}=>{socket.ReceiveBufferSize} ({socket.ReceiveBufferSize/initialReceive}x) SendBuf = {initialSend}=>{socket.SendBufferSize} ({socket.SendBufferSize/initialSend}x)");
+        }
+
+        // generate a connection hash from IP+Port.
+        //
+        // NOTE: IPEndPoint.GetHashCode() allocates.
+        //  it calls m_Address.GetHashCode().
+        //  m_Address is an IPAddress.
+        //  GetHashCode() allocates for IPv6:
+        //  https://github.com/mono/mono/blob/bdd772531d379b4e78593587d15113c37edd4a64/mcs/class/referencesource/System/net/System/Net/IPAddress.cs#L699
+        //
+        // => using only newClientEP.Port wouldn't work, because
+        //    different connections can have the same port.
+        public static int ConnectionHash(EndPoint endPoint) =>
+            endPoint.GetHashCode();
+
+        // cookies need to be generated with a secure random generator.
+        // we don't want them to be deterministic / predictable.
+        // RNG is cached to avoid runtime allocations.
+        static readonly RNGCryptoServiceProvider cryptoRandom = new RNGCryptoServiceProvider();
+        static readonly byte[] cryptoRandomBuffer = new byte[4];
+        public static uint GenerateCookie()
+        {
+            cryptoRandom.GetBytes(cryptoRandomBuffer);
+            return BitConverter.ToUInt32(cryptoRandomBuffer, 0);
+        }
+    }
+}