DnsApplicationAssemblyLoadContext: updated implementation to load unmanaged native dlls.

DnsServerCore/Dns/Applications/DnsApplicationAssemblyLoadContext.cs

@@ -17,20 +17,144 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 */
 
+using System;
+using System.Collections.Generic;
+using System.IO;
 using System.Reflection;
+using System.Runtime.InteropServices;
 using System.Runtime.Loader;
 
 namespace DnsServerCore.Dns
 {
     class DnsApplicationAssemblyLoadContext : AssemblyLoadContext
     {
-        public DnsApplicationAssemblyLoadContext()
+        #region variables
+
+        readonly string _applicationFolder;
+
+        readonly List<string> _unmanagedDllTempPaths = new List<string>(1);
+
+        #endregion
+
+        #region constructor
+
+        public DnsApplicationAssemblyLoadContext(string applicationFolder)
             : base(true)
-        { }
+        {
+            _applicationFolder = applicationFolder;
+
+            Unloading += delegate (AssemblyLoadContext obj)
+            {
+                foreach (string unmanagedDllTempPath in _unmanagedDllTempPaths)
+                {
+                    try
+                    {
+                        File.Delete(unmanagedDllTempPath);
+                    }
+                    catch
+                    { }
+                }
+            };
+        }
+
+        #endregion
+
+        #region overrides
 
         protected override Assembly Load(AssemblyName assemblyName)
         {
             return null;
         }
+
+        protected override IntPtr LoadUnmanagedDll(string unmanagedDllName)
+        {
+            string unmanagedDllPath = null;
+
+            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+            {
+                string runtime = "win-" + RuntimeInformation.ProcessArchitecture.ToString().ToLower();
+                string[] prefixes = new string[] { "" };
+                string[] extensions = new string[] { ".dll" };
+
+                unmanagedDllPath = FindUnmanagedDllPath(unmanagedDllName, runtime, prefixes, extensions);
+            }
+            else if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux))
+            {
+                bool isAlpine = false;
+
+                try
+                {
+                    string osReleaseFile = "/etc/os-release";
+
+                    if (File.Exists(osReleaseFile))
+                        isAlpine = File.ReadAllText(osReleaseFile).Contains("alpine", StringComparison.OrdinalIgnoreCase);
+                }
+                catch
+                { }
+
+                string runtimeAlpine = "alpine-" + RuntimeInformation.ProcessArchitecture.ToString().ToLower();
+                string runtimeLinux = "linux-" + RuntimeInformation.ProcessArchitecture.ToString().ToLower();
+                string[] prefixes = new string[] { "", "lib" };
+                string[] extensions = new string[] { ".so", ".so.1" };
+
+                if (isAlpine)
+                {
+                    unmanagedDllPath = FindUnmanagedDllPath(unmanagedDllName, runtimeAlpine, prefixes, extensions);
+                    if (unmanagedDllPath is null)
+                        unmanagedDllPath = FindUnmanagedDllPath(unmanagedDllName, runtimeLinux, prefixes, extensions);
+                }
+                else
+                {
+                    unmanagedDllPath = FindUnmanagedDllPath(unmanagedDllName, runtimeLinux, prefixes, extensions);
+                }
+            }
+            else if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
+            {
+                string runtime = "osx-" + RuntimeInformation.ProcessArchitecture.ToString().ToLower();
+                string[] prefixes = new string[] { "", "lib" };
+                string[] extensions = new string[] { ".dylib" };
+
+                unmanagedDllPath = FindUnmanagedDllPath(unmanagedDllName, runtime, prefixes, extensions);
+            }
+
+            if (unmanagedDllPath is null)
+                return IntPtr.Zero;
+
+            //copy unmanaged dll into temp file for loading to allow uninstalling/updating app at runtime.
+            string tempPath = Path.GetTempFileName();
+
+            using (FileStream srcFile = new FileStream(unmanagedDllPath, FileMode.Open, FileAccess.Read))
+            {
+                using (FileStream dstFile = new FileStream(tempPath, FileMode.Create, FileAccess.Write))
+                {
+                    srcFile.CopyTo(dstFile);
+                }
+            }
+
+            _unmanagedDllTempPaths.Add(tempPath);
+
+            return LoadUnmanagedDllFromPath(tempPath);
+        }
+
+        #endregion
+
+        #region private
+
+        private string FindUnmanagedDllPath(string unmanagedDllName, string runtime, string[] prefixes, string[] extensions)
+        {
+            foreach (string prefix in prefixes)
+            {
+                foreach (string extension in extensions)
+                {
+                    string path = Path.Combine(_applicationFolder, "runtimes", runtime, "native", prefix + unmanagedDllName + extension);
+                    if (File.Exists(path))
+                        return path;
+                }
+            }
+
+            return null;
+        }
+
+        #endregion
     }
 }