ldn: Implement calls of UserLocalCommunicationService (#829)

* ldn: Implement calls of UserLocalCommunicationService

- Implement `IUserServiceCreator: CreateUserLocalCommunicationService` according to RE.
- Implement `IUserLocalCommunicationService` calls:
  - Every calls in this interface are layered to `NetworkInterface`.
  - `GetState` according to RE.
  - `InitializeOld`, `Initialize` and `Finalize` stubbed with the appropriate result code and some TODO according to RE.
  - `AttachStateChangeEvent` according to RE.

* Fix var name and TODO comments

* Fix review

1 files changed, 59 insertions, 0 deletions

diff --git a/Ryujinx.HLE/HOS/Services/Ldn/NetworkInterface.cs b/Ryujinx.HLE/HOS/Services/Ldn/NetworkInterface.cs
new file mode 100644
index 00000000..f06c6644
--- /dev/null
+++ b/Ryujinx.HLE/HOS/Services/Ldn/NetworkInterface.cs
@@ -0,0 +1,59 @@
+using Ryujinx.Common.Logging;
+using Ryujinx.HLE.HOS.Kernel.Threading;
+using Ryujinx.HLE.HOS.Services.Ldn.Types;
+using System.Net;
+
+namespace Ryujinx.HLE.HOS.Services.Ldn
+{
+    internal class NetworkInterface
+    {
+        public ResultCode NifmState        { get; set; }
+        public KEvent     StateChangeEvent { get; private set; }
+
+        private NetworkState _state;
+
+        public NetworkInterface(Horizon system)
+        {
+            // TODO(Ac_K): Determine where the internal state is set.
+            NifmState        = ResultCode.Success;
+            StateChangeEvent = new KEvent(system);
+
+            _state = NetworkState.None;
+        }
+
+        public ResultCode Initialize(int unknown, int version, IPAddress ipv4Address, IPAddress subnetMaskAddress)
+        {
+            // TODO(Ac_K): Call nn::nifm::InitializeSystem().
+            //             If the call failed, it returns the result code.
+            //             If the call succeed, it signal and clear an event then start a new thread named nn.ldn.NetworkInterfaceMonitor.
+
+            Logger.PrintStub(LogClass.ServiceLdn, new { version });
+
+            // NOTE: Since we don't support ldn for now, we can return this following result code to make it disabled.
+            return ResultCode.DeviceDisabled;
+        }
+
+        public ResultCode GetState(out NetworkState state)
+        {
+            // Return ResultCode.InvalidArgument if _state is null, doesn't occur in our case.
+
+            state = _state;
+
+            return ResultCode.Success;
+        }
+
+        public ResultCode Finalize()
+        {
+            // TODO(Ac_K): Finalize nifm service then kill the thread named nn.ldn.NetworkInterfaceMonitor.
+
+            _state = NetworkState.None;
+
+            StateChangeEvent.WritableEvent.Signal();
+            StateChangeEvent.WritableEvent.Clear();
+
+            Logger.PrintStub(LogClass.ServiceLdn);
+
+            return ResultCode.Success;
+        }
+    }
+}
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