Partially revert #125574: restore fixed buffers in networking P/Invoke structs to fix Crst level violation

src/libraries/Common/src/Interop/BSD/System.Native/Interop.TcpConnectionInfo.cs

@@ -2,17 +2,16 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Net.NetworkInformation;
-using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 
 internal static partial class Interop
 {
     internal static partial class Sys
     {
         [StructLayout(LayoutKind.Sequential)]
-        public struct IPEndPointInfo
+        public unsafe struct IPEndPointInfo
         {
-            public InlineArray16<byte> AddressBytes;
+            public fixed byte AddressBytes[16];
             public uint NumAddressBytes;
             public uint Port;
             private uint __padding; // For native struct-size padding. Does not contain useful data.

src/libraries/Common/src/Interop/Unix/System.Native/Interop.EnumerateInterfaceAddresses.cs

@@ -1,46 +1,45 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 
 internal static partial class Interop
 {
     internal static partial class Sys
     {
         [StructLayout(LayoutKind.Sequential)]
-        public struct LinkLayerAddressInfo
+        public unsafe struct LinkLayerAddressInfo
         {
             public int InterfaceIndex;
-            public InlineArray8<byte> AddressBytes;
+            public fixed byte AddressBytes[8];
             public byte NumAddressBytes;
             private byte __padding; // For native struct-size padding. Does not contain useful data.
             public ushort HardwareType;
         }
 
         [StructLayout(LayoutKind.Sequential)]
-        public struct IpAddressInfo
+        public unsafe struct IpAddressInfo
         {
             public int InterfaceIndex;
-            public InlineArray16<byte> AddressBytes;
+            public fixed byte AddressBytes[16];
             public byte NumAddressBytes;
             public byte PrefixLength;
-            private InlineArray2<byte> __padding;
+            private fixed byte __padding[2];
         }
 
         [StructLayout(LayoutKind.Sequential)]
-        public struct NetworkInterfaceInfo
+        public unsafe struct NetworkInterfaceInfo
         {
-            public InlineArray16<byte> Name;
+            public fixed byte Name[16];
             public long Speed;
             public int InterfaceIndex;
             public int Mtu;
             public ushort HardwareType;
             public byte OperationalState;
             public byte NumAddressBytes;
-            public InlineArray8<byte> AddressBytes;
+            public fixed byte AddressBytes[8];
             public byte SupportsMulticast;
-            private InlineArray3<byte> __padding;
+            private fixed byte __padding[3];
         }
 
         [LibraryImport(Libraries.SystemNative, EntryPoint = "SystemNative_EnumerateInterfaceAddresses")]

src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/AndroidNetworkInterface.cs

@@ -19,7 +19,7 @@ internal unsafe AndroidNetworkInterface(string name, Interop.Sys.NetworkInterfac
             _index = networkInterfaceInfo->InterfaceIndex;
             if (networkInterfaceInfo->NumAddressBytes > 0)
             {
-                _physicalAddress = new PhysicalAddress(((ReadOnlySpan<byte>)networkInterfaceInfo->AddressBytes)[..networkInterfaceInfo->NumAddressBytes].ToArray());
+                _physicalAddress = new PhysicalAddress(new ReadOnlySpan<byte>(networkInterfaceInfo->AddressBytes, networkInterfaceInfo->NumAddressBytes).ToArray());
             }
 
             _mtu = networkInterfaceInfo->Mtu;
@@ -33,7 +33,7 @@ internal unsafe AndroidNetworkInterface(string name, Interop.Sys.NetworkInterfac
 
         internal unsafe void AddAddress(Interop.Sys.IpAddressInfo *addressInfo)
         {
-            var address = new IPAddress(((ReadOnlySpan<byte>)addressInfo->AddressBytes)[..addressInfo->NumAddressBytes]);
+            var address = new IPAddress(new ReadOnlySpan<byte>(addressInfo->AddressBytes, addressInfo->NumAddressBytes));
             if (address.IsIPv6LinkLocal)
             {
                 address.ScopeId = addressInfo->InterfaceIndex;

src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/BsdIPGlobalProperties.cs

@@ -32,12 +32,12 @@ private unsafe TcpConnectionInformation[] GetTcpConnections(bool listeners)
                     continue;
                 }
 
-                IPAddress localIPAddress = new IPAddress(((ReadOnlySpan<byte>)nativeInfo.LocalEndPoint.AddressBytes)[..checked((int)nativeInfo.LocalEndPoint.NumAddressBytes)]);
+                IPAddress localIPAddress = new IPAddress(new ReadOnlySpan<byte>(nativeInfo.LocalEndPoint.AddressBytes, checked((int)nativeInfo.LocalEndPoint.NumAddressBytes)));
                 IPEndPoint local = new IPEndPoint(localIPAddress, (int)nativeInfo.LocalEndPoint.Port);
 
                 IPAddress remoteIPAddress = nativeInfo.RemoteEndPoint.NumAddressBytes == 0 ?
                     IPAddress.Any :
-                    new IPAddress(((ReadOnlySpan<byte>)nativeInfo.RemoteEndPoint.AddressBytes)[..checked((int)nativeInfo.RemoteEndPoint.NumAddressBytes)]);
+                    new IPAddress(new ReadOnlySpan<byte>(nativeInfo.RemoteEndPoint.AddressBytes, checked((int)nativeInfo.RemoteEndPoint.NumAddressBytes)));
 
                 IPEndPoint remote = new IPEndPoint(remoteIPAddress, (int)nativeInfo.RemoteEndPoint.Port);
                 connectionInformations[nextResultIndex++] = new SimpleTcpConnectionInformation(local, remote, state);
@@ -87,7 +87,7 @@ public override unsafe IPEndPoint[] GetActiveUdpListeners()
                 int port = (int)endPointInfo.Port;
                 IPAddress ipAddress = endPointInfo.NumAddressBytes == 0 ?
                     IPAddress.Any :
-                    new IPAddress(((ReadOnlySpan<byte>)endPointInfo.AddressBytes)[..checked((int)endPointInfo.NumAddressBytes)]);
+                    new IPAddress(new ReadOnlySpan<byte>(endPointInfo.AddressBytes, checked((int)endPointInfo.NumAddressBytes)));
 
                 endPoints[i] = new IPEndPoint(ipAddress, port);
             }

src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/BsdIpInterfaceProperties.cs

@@ -93,7 +93,7 @@ private static unsafe void OnGatewayFound(void* pContext, Interop.Sys.IpAddressI
         {
             Context* context = (Context*)pContext;
 
-            IPAddress ipAddress = new IPAddress(((ReadOnlySpan<byte>)gatewayAddressInfo->AddressBytes)[..gatewayAddressInfo->NumAddressBytes]);
+            IPAddress ipAddress = new IPAddress(new ReadOnlySpan<byte>(gatewayAddressInfo->AddressBytes, gatewayAddressInfo->NumAddressBytes));
             if (ipAddress.IsIPv6LinkLocal)
             {
                 // For Link-Local addresses add ScopeId as that is not part of the route entry.

src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/IPAddressUtil.cs

@@ -34,7 +34,7 @@ public static bool IsMulticast(IPAddress address)
         /// <returns>A new IPAddress created with the information in the native structure.</returns>
         public static unsafe IPAddress GetIPAddressFromNativeInfo(Interop.Sys.IpAddressInfo* addressInfo)
         {
-            IPAddress ipAddress = new IPAddress(((ReadOnlySpan<byte>)addressInfo->AddressBytes)[..addressInfo->NumAddressBytes]);
+            IPAddress ipAddress = new IPAddress(new ReadOnlySpan<byte>(addressInfo->AddressBytes, addressInfo->NumAddressBytes));
             return ipAddress;
         }
     }

src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/LinuxNetworkInterface.cs

@@ -95,7 +95,7 @@ public static unsafe NetworkInterface[] GetLinuxNetworkInterfaces()
 
                 for (int i = 0; i < interfaceCount; i++)
                 {
-                    var lni = new LinuxNetworkInterface(Utf8StringMarshaller.ConvertToManaged((byte*)&nii->Name)!, nii->InterfaceIndex, systemProperties);
+                    var lni = new LinuxNetworkInterface(Utf8StringMarshaller.ConvertToManaged(nii->Name)!, nii->InterfaceIndex, systemProperties);
                     lni._interfaceType = (NetworkInterfaceType)nii->HardwareType;
                     lni._speed = nii->Speed;
                     lni._operationalStatus = (OperationalStatus)nii->OperationalState;
@@ -104,7 +104,7 @@ public static unsafe NetworkInterface[] GetLinuxNetworkInterfaces()
 
                     if (nii->NumAddressBytes > 0)
                     {
-                        lni._physicalAddress = new PhysicalAddress(((ReadOnlySpan<byte>)nii->AddressBytes)[..nii->NumAddressBytes].ToArray());
+                        lni._physicalAddress = new PhysicalAddress(new ReadOnlySpan<byte>(nii->AddressBytes, nii->NumAddressBytes).ToArray());
                     }
 
                     interfaces[i] = lni;
@@ -114,7 +114,7 @@ public static unsafe NetworkInterface[] GetLinuxNetworkInterfaces()
 
                 while (addressCount != 0)
                 {
-                    var address = new IPAddress(((ReadOnlySpan<byte>)ai->AddressBytes)[..ai->NumAddressBytes]);
+                    var address = new IPAddress(new ReadOnlySpan<byte>(ai->AddressBytes, ai->NumAddressBytes));
                     if (address.IsIPv6LinkLocal)
                     {
                         address.ScopeId = ai->InterfaceIndex;

src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/NetworkInterfacePal.Android.cs

@@ -52,7 +52,7 @@ private static unsafe AndroidNetworkInterface[] ToAndroidNetworkInterfaceArray(i
             var networkInterfaceInfo = (Interop.Sys.NetworkInterfaceInfo*)networkInterfacesPtr;
             for (int i = 0; i < interfaceCount; i++, networkInterfaceInfo++)
             {
-                var name = Utf8StringMarshaller.ConvertToManaged((byte*)&networkInterfaceInfo->Name);
+                var name = Utf8StringMarshaller.ConvertToManaged(networkInterfaceInfo->Name);
                 networkInterfaces[i] = new AndroidNetworkInterface(name!, networkInterfaceInfo);
             }
 

src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/UnixNetworkInterface.cs

@@ -98,7 +98,11 @@ protected unsafe void ProcessIpv6Address(Interop.Sys.IpAddressInfo* addressInfo,
 
         protected unsafe void ProcessLinkLayerAddress(Interop.Sys.LinkLayerAddressInfo* llAddr)
         {
-            byte[] macAddress = ((ReadOnlySpan<byte>)llAddr->AddressBytes)[..llAddr->NumAddressBytes].ToArray();
+            byte[] macAddress = new byte[llAddr->NumAddressBytes];
+            fixed (byte* macAddressPtr = macAddress)
+            {
+                Buffer.MemoryCopy(llAddr->AddressBytes, macAddressPtr, llAddr->NumAddressBytes, llAddr->NumAddressBytes);
+            }
             PhysicalAddress physicalAddress = new PhysicalAddress(macAddress);
 
             _index = llAddr->InterfaceIndex;