Updating Darwin OS detection

src/Microsoft.AspNet.Server.Kestrel/KestrelEngine.cs

@@ -44,19 +44,19 @@ namespace Microsoft.AspNet.Server.Kestrel
                         architecture, 
                         "libuv.dll");
                 }
-                else if ((int)Environment.OSVersion.Platform == 4)
+                else if (Libuv.IsDarwin)
-                {
-                    libraryPath = "libuv.so.1";
-                }
-                else
                 {
                     libraryPath = Path.Combine(
                         libraryPath,
-                        "native", 
+                        "native",
                         "darwin",
-                        "universal", 
+                        "universal",
                         "libuv.dylib");
                 }
+                else
+                {
+                    libraryPath = "libuv.so.1";
+                }
             }
             Libuv.Load(libraryPath);
         }

src/Microsoft.AspNet.Server.Kestrel/Networking/Libuv.cs

@@ -13,9 +13,15 @@ namespace Microsoft.AspNet.Server.Kestrel.Networking
         public Libuv()
         {
             IsWindows = PlatformApis.IsWindows();
+            if (!IsWindows)
+            {
+                IsDarwin = PlatformApis.IsDarwin();
+            }
         }
 
         public bool IsWindows;
+        public bool IsDarwin;
+
         public Func<string, IntPtr> LoadLibrary;
         public Func<IntPtr, bool> FreeLibrary;
         public Func<IntPtr, string, IntPtr> GetProcAddress;

src/Microsoft.AspNet.Server.Kestrel/Networking/PlatformApis.cs

@@ -10,7 +10,7 @@ namespace Microsoft.AspNet.Server.Kestrel.Networking
 {
     public static class PlatformApis
     {
-        public static bool IsWindows() 
+        public static bool IsWindows()
         {
 #if ASPNETCORE50
             return true;
@@ -20,6 +20,34 @@ namespace Microsoft.AspNet.Server.Kestrel.Networking
 #endif
         }
 
+        [DllImport("libc")]
+        static extern int uname(IntPtr buf);
+
+        static unsafe string GetUname()
+        {
+            var buffer = new byte[8192];
+            try
+            {
+                fixed (byte* buf = buffer)
+                {
+                    if (uname((IntPtr)buf) == 0)
+                    {
+                        return Marshal.PtrToStringAnsi((IntPtr)buf);
+                    }
+                }
+                return string.Empty;
+            }
+            catch
+            {
+                return string.Empty;
+            }
+        }
+
+        public static bool IsDarwin()
+        {
+            return string.Equals(GetUname(), "Darwin", StringComparison.Ordinal);
+        }
+
         public static void Apply(Libuv libuv)
         {
             if (libuv.IsWindows)
@@ -55,7 +83,7 @@ namespace Microsoft.AspNet.Server.Kestrel.Networking
         {
             [DllImport("libdl")]
             public static extern IntPtr dlopen(String fileName, int flags);
-            
+
             [DllImport("libdl")]
             public static extern IntPtr dlsym(IntPtr handle, String symbol);
 
@@ -65,17 +93,17 @@ namespace Microsoft.AspNet.Server.Kestrel.Networking
             [DllImport("libdl")]
             public static extern IntPtr dlerror();
 
-            public static IntPtr LoadLibrary(string dllToLoad) 
+            public static IntPtr LoadLibrary(string dllToLoad)
             {
                 return dlopen(dllToLoad, 2);
             }
 
-            public static bool FreeLibrary(IntPtr hModule) 
+            public static bool FreeLibrary(IntPtr hModule)
             {
                 return dlclose(hModule) == 0;
             }
 
-            public static IntPtr GetProcAddress(IntPtr hModule, string procedureName) 
+            public static IntPtr GetProcAddress(IntPtr hModule, string procedureName)
             {
                 dlerror();
                 var res = dlsym(hModule, procedureName);