Additonal optimizations in GetProcessIdByLocalPort

Author: antrv-verto

Titanium.Web.Proxy/Helpers/NativeMethods.Tcp.cs

@@ -37,9 +37,9 @@ internal struct TcpRow
         {
             public TcpState state;
             public uint localAddr;
-            public TcpPort localPort;
+            public uint localPort; // in network byte order (order of bytes - 1,0,3,2)
             public uint remoteAddr;
-            public TcpPort remotePort;
+            public uint remotePort; // in network byte order (order of bytes - 1,0,3,2)
             public int owningPid;
         }
 
@@ -51,23 +51,12 @@ internal unsafe struct Tcp6Row
         {
             public fixed byte localAddr[16];
             public uint localScopeId;
-            public TcpPort localPort;
+            public uint localPort; // in network byte order (order of bytes - 1,0,3,2)
             public fixed byte remoteAddr[16];
             public uint remoteScopeId;
-            public TcpPort remotePort;
+            public uint remotePort; // in network byte order (order of bytes - 1,0,3,2)
             public TcpState state;
             public int owningPid;
         }
-
-        [StructLayout(LayoutKind.Sequential)]
-        internal struct TcpPort
-        {
-            public byte port1;
-            public byte port2;
-            public byte port3;
-            public byte port4;
-
-            public int Port => (port1 << 8) + port2 + (port3 << 24) + (port4 << 16);
-        }
     }
 }

Titanium.Web.Proxy/Helpers/Tcp.cs

@@ -37,14 +37,15 @@ internal static unsafe int GetProcessIdByLocalPort(IpVersion ipVersion, int loca
                             0) == 0)
                     {
                         int rowCount = *(int*)tcpTable;
+                        uint portInNetworkByteOrder = ToNetworkByteOrder((uint)localPort);
 
                         if (ipVersion == IpVersion.Ipv4)
                         {
                             NativeMethods.TcpRow* rowPtr = (NativeMethods.TcpRow*)(tcpTable + 4);
 
                             for (int i = 0; i < rowCount; ++i)
                             {
-                                if (rowPtr->localPort.Port == localPort)
+                                if (rowPtr->localPort == portInNetworkByteOrder)
                                 {
                                     return rowPtr->owningPid;
                                 }
@@ -58,7 +59,7 @@ internal static unsafe int GetProcessIdByLocalPort(IpVersion ipVersion, int loca
 
                             for (int i = 0; i < rowCount; ++i)
                             {
-                                if (rowPtr->localPort.Port == localPort)
+                                if (rowPtr->localPort == portInNetworkByteOrder)
                                 {
                                     return rowPtr->owningPid;
                                 }
@@ -80,6 +81,18 @@ internal static unsafe int GetProcessIdByLocalPort(IpVersion ipVersion, int loca
             return 0;
         }
 
+        /// <summary>
+        /// Converts 32-bit integer from native byte order (little-endian)
+        /// to network byte order for port,
+        /// switches 0th and 1st bytes, and 2nd and 3rd bytes
+        /// </summary>
+        /// <param name="port"></param>
+        /// <returns></returns>
+        private static uint ToNetworkByteOrder(uint port)
+        {
+            return ((port >> 8) & 0x00FF00FFu) | ((port << 8) & 0xFF00FF00u);
+        }
+
         /// <summary>
         ///     relays the input clientStream to the server at the specified host name and port with the given httpCmd and headers
         ///     as prefix