WinHttpHandler: fix double -> uint conversions for ARM64

src/libraries/System.Net.Http.WinHttpHandler/src/System/Net/Http/WinHttpHandler.cs

@@ -962,7 +962,10 @@ private async Task StartRequestAsync(WinHttpRequestState state)
                 // Since the headers have been read, set the "receive" timeout to be based on each read
                 // call of the response body data. WINHTTP_OPTION_RECEIVE_TIMEOUT sets a timeout on each
                 // lower layer winsock read.
-                uint optionData = unchecked((uint)_receiveDataTimeout.TotalMilliseconds);
+                // Timeout.InfiniteTimeSpan will be converted to uint.MaxValue milliseconds (~ 50 days).
+                // The result a of double->uint cast is unspecified for -1 and may differ on ARM, returning 0 instead of uint.MaxValue.
+                // To handle Timeout.InfiniteTimespan correctly, we need to cast to int first.
+                uint optionData = (uint)(int)_receiveDataTimeout.TotalMilliseconds;
                 SetWinHttpOption(state.RequestHandle, Interop.WinHttp.WINHTTP_OPTION_RECEIVE_TIMEOUT, ref optionData);
 
                 HttpResponseMessage responseMessage =
@@ -1007,8 +1010,10 @@ private unsafe void SetTcpKeepalive(SafeWinHttpHandle sessionHandle)
                     onoff = 1,
 
                     // Timeout.InfiniteTimeSpan will be converted to uint.MaxValue milliseconds (~ 50 days)
-                    keepaliveinterval = (uint)_tcpKeepAliveInterval.TotalMilliseconds,
-                    keepalivetime = (uint)_tcpKeepAliveTime.TotalMilliseconds
+                    // The result a of double->uint cast is unspecified for -1 and may differ on ARM, returning 0 instead of uint.MaxValue.
+                    // To handle Timeout.InfiniteTimespan correctly, we need to cast to int first.
+                    keepaliveinterval = (uint)(int)_tcpKeepAliveInterval.TotalMilliseconds,
+                    keepalivetime = (uint)(int)_tcpKeepAliveTime.TotalMilliseconds
                 };
 
                 SetWinHttpOption(

src/libraries/System.Net.Http.WinHttpHandler/tests/UnitTests/APICallHistory.cs

@@ -66,7 +66,7 @@ public static ProxyInfo RequestProxySettings
 
         public static int? WinHttpOptionSendTimeout { get; set; }
 
-        public static int? WinHttpOptionReceiveTimeout { get; set; }
+        public static uint? WinHttpOptionReceiveTimeout { get; set; }
 
         public static List<IntPtr> WinHttpOptionClientCertContext { get { return winHttpOptionClientCertContextList; } }
 

src/libraries/System.Net.Http.WinHttpHandler/tests/UnitTests/FakeInterop.cs

@@ -507,6 +507,10 @@ public static bool WinHttpSetOption(
             {
                 APICallHistory.WinHttpOptionRedirectPolicy = optionData;
             }
+            else if (option == Interop.WinHttp.WINHTTP_OPTION_RECEIVE_TIMEOUT)
+            {
+                APICallHistory.WinHttpOptionReceiveTimeout = optionData;
+            }
 
             return true;
         }

src/libraries/System.Net.Http.WinHttpHandler/tests/UnitTests/WinHttpHandlerTest.cs

@@ -463,6 +463,16 @@ public void MaxConnectionsPerServer_SetPositiveValue_Success()
             handler.MaxConnectionsPerServer = 1;
         }
 
+        [Fact]
+        public void ReceiveDataTimeout_SetValidValue_ForwardsCorrectNativeOptionToWinHttp()
+        {
+            var handler = new WinHttpHandler();
+
+            SendRequestHelper.Send(handler, () => handler.ReceiveDataTimeout = TimeSpan.FromSeconds(13));
+
+            Assert.Equal(13_000u, APICallHistory.WinHttpOptionReceiveTimeout.Value);
+        }
+
         [Fact]
         public void ReceiveDataTimeout_SetNegativeValue_ThrowsArgumentOutOfRangeException()
         {
@@ -490,11 +500,13 @@ public void ReceiveDataTimeout_SetZeroValue_ThrowsArgumentOutOfRangeException()
         }
 
         [Fact]
-        public void ReceiveDataTimeout_SetInfiniteValue_NoExceptionThrown()
+        public void ReceiveDataTimeout_SetInfiniteTimeSpan_TranslatesToUInt32MaxValue()
         {
             var handler = new WinHttpHandler();
 
-            handler.ReceiveDataTimeout = Timeout.InfiniteTimeSpan;
+            SendRequestHelper.Send(handler, () => handler.ReceiveDataTimeout = Timeout.InfiniteTimeSpan);
+
+            Assert.Equal(uint.MaxValue, APICallHistory.WinHttpOptionReceiveTimeout.Value);
         }
 
         [Fact]