[Darwin][Network.framework] Add src/platform/Darwin/system/SystemLayerImplDispatch.mm such that the unit tests runs using the dispatch mechanism instead of the socket based implementation

Author: vivien-apple

.github/workflows/lint.yml

@@ -126,6 +126,7 @@ jobs:
                      --known-failure platform/DeviceSafeQueue.h \
                      --known-failure platform/GLibTypeDeleter.h \
                      --known-failure platform/SingletonConfigurationManager.cpp \
+                     --known-failure system/SystemLayerImplDispatch.h \
                   "
                   # These ARE actually orphaned but due to dynamic-server we have code paths
                   # for them. Keeping them as a list as they still need review ...

src/inet/tests/TestInetCommonPosix.cpp

@@ -358,16 +358,22 @@ void ServiceEvents(uint32_t aSleepTimeMilliseconds)
         }
     }
 
+#if !CHIP_SYSTEM_CONFIG_USE_DISPATCH
     // Start a timer (with a no-op callback) to ensure that WaitForEvents() does not block longer than aSleepTimeMilliseconds.
     gSystemLayer.StartTimer(
         System::Clock::Milliseconds32(aSleepTimeMilliseconds), [](System::Layer *, void *) -> void {}, nullptr);
+#endif
 
-#if CHIP_SYSTEM_CONFIG_USE_SOCKETS
+#if CHIP_SYSTEM_CONFIG_USE_SOCKETS && !CHIP_SYSTEM_CONFIG_USE_DISPATCH
     gSystemLayer.PrepareEvents();
     gSystemLayer.WaitForEvents();
     gSystemLayer.HandleEvents();
 #endif
 
+#if CHIP_SYSTEM_CONFIG_USE_DISPATCH
+    gSystemLayer.HandleDispatchQueueEvents(System::Clock::Milliseconds32(aSleepTimeMilliseconds));
+#endif
+
 #if CHIP_SYSTEM_CONFIG_USE_LWIP || CHIP_SYSTEM_CONFIG_USE_OPENTHREAD_ENDPOINT
     if (gSystemLayer.IsInitialized())
     {

src/platform/Darwin/BUILD.gn

@@ -16,6 +16,7 @@ import("//build_overrides/chip.gni")
 import("//build_overrides/nlassert.gni")
 
 import("${chip_root}/src/platform/device.gni")
+import("${chip_root}/src/system/system.gni")
 
 assert(chip_device_platform == "darwin")
 
@@ -77,8 +78,14 @@ static_library("Darwin") {
     "SystemTimeSupport.cpp",
     "UserDefaults.h",
     "UserDefaults.mm",
+    "system/SystemLayerImplDispatch.h",
+    "system/SystemLayerImplDispatch.mm",
   ]
 
+  if (chip_system_config_use_sockets) {
+    sources += [ "system/SystemLayerImplDispatchSockets.mm" ]
+  }
+
   if (chip_enable_wifi) {
     sources += [
       "WiFi/ConfigurationManagerImplWiFi.cpp",

src/platform/Darwin/PlatformManagerImpl.cpp

@@ -70,7 +70,7 @@ CHIP_ERROR PlatformManagerImpl::_InitChipStack()
 
 #if CHIP_SYSTEM_CONFIG_USE_DISPATCH
     // Ensure there is a dispatch queue available
-    static_cast<System::LayerSocketsLoop &>(DeviceLayer::SystemLayer()).SetDispatchQueue(GetWorkQueue());
+    static_cast<System::LayerDispatch &>(DeviceLayer::SystemLayer()).SetDispatchQueue(GetWorkQueue());
 #endif
 
     // Call _InitChipStack() on the generic implementation base class

src/platform/Darwin/system/SystemLayerImplDispatch.h

@@ -0,0 +1,122 @@
+/*
+ *
+ *    Copyright (c) 2025 Project CHIP Authors
+ *
+ *    Licensed under the Apache License, Version 2.0 (the "License");
+ *    you may not use this file except in compliance with the License.
+ *    You may obtain a copy of the License at
+ *
+ *        http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *    Unless required by applicable law or agreed to in writing, software
+ *    distributed under the License is distributed on an "AS IS" BASIS,
+ *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *    See the License for the specific language governing permissions and
+ *    limitations under the License.
+ */
+
+/**
+ *    @file
+ *      This file declares an implementation of System::Layer using select().
+ */
+
+#pragma once
+
+#include "system/SystemConfig.h"
+
+#include <lib/support/ObjectLifeCycle.h>
+#include <system/SystemLayer.h>
+#include <system/SystemTimer.h>
+
+namespace chip {
+namespace System {
+
+class LayerImplDispatch : public LayerDispatch
+{
+public:
+    LayerImplDispatch() = default;
+    ~LayerImplDispatch() override { VerifyOrDie(mLayerState.Destroy()); }
+
+    // Layer overrides.
+    CHIP_ERROR Init() override;
+    void Shutdown() override;
+    bool IsInitialized() const override { return mLayerState.IsInitialized(); }
+    CHIP_ERROR StartTimer(Clock::Timeout delay, TimerCompleteCallback onComplete, void * appState) override;
+    CHIP_ERROR ExtendTimerTo(Clock::Timeout delay, TimerCompleteCallback onComplete, void * appState) override;
+    bool IsTimerActive(TimerCompleteCallback onComplete, void * appState) override;
+    Clock::Timeout GetRemainingTime(TimerCompleteCallback onComplete, void * appState) override;
+    void CancelTimer(TimerCompleteCallback onComplete, void * appState) override;
+    CHIP_ERROR ScheduleWork(TimerCompleteCallback onComplete, void * appState) override;
+
+    // LayerDispatch overrides.
+    void SetDispatchQueue(dispatch_queue_t dispatchQueue) override { mDispatchQueue = dispatchQueue; };
+    dispatch_queue_t GetDispatchQueue() override { return mDispatchQueue; };
+    void HandleDispatchQueueEvents(Clock::Timeout timeout) override;
+    CHIP_ERROR ScheduleWorkWithBlock(dispatch_block_t block) override;
+
+#if CHIP_SYSTEM_CONFIG_USE_SOCKETS
+    // LayerSocket overrides.
+    CHIP_ERROR StartWatchingSocket(int fd, SocketWatchToken * tokenOut) override;
+    CHIP_ERROR SetCallback(SocketWatchToken token, SocketWatchCallback callback, intptr_t data) override;
+    CHIP_ERROR RequestCallbackOnPendingRead(SocketWatchToken token) override;
+    CHIP_ERROR RequestCallbackOnPendingWrite(SocketWatchToken token) override;
+    CHIP_ERROR ClearCallbackOnPendingRead(SocketWatchToken token) override;
+    CHIP_ERROR ClearCallbackOnPendingWrite(SocketWatchToken token) override;
+    CHIP_ERROR StopWatchingSocket(SocketWatchToken * tokenInOut) override;
+    SocketWatchToken InvalidSocketWatchToken() override { return reinterpret_cast<SocketWatchToken>(nullptr); }
+#endif
+
+protected:
+#if CHIP_SYSTEM_CONFIG_USE_SOCKETS
+    struct SelectSets
+    {
+        fd_set mReadSet;
+        fd_set mWriteSet;
+        fd_set mErrorSet;
+    };
+
+    static constexpr int kSocketWatchMax = (INET_CONFIG_ENABLE_TCP_ENDPOINT ? INET_CONFIG_NUM_TCP_ENDPOINTS : 0) +
+        (INET_CONFIG_ENABLE_UDP_ENDPOINT ? INET_CONFIG_NUM_UDP_ENDPOINTS : 0);
+
+    struct SocketWatch
+    {
+        int mFD;
+        SocketEvents mPendingIO;
+        SocketWatchCallback mCallback;
+        intptr_t mCallbackData;
+
+        dispatch_source_t mRdSource = nullptr;
+        dispatch_source_t mWrSource = nullptr;
+
+        bool IsActive() const { return mFD != kInvalidFd; }
+        void PrepareEvents(SelectSets & sets, int & maxFd) const;
+        void HandleEvents(const SelectSets & sets) const;
+        void Clear();
+    };
+    SocketWatch mSocketWatchPool[kSocketWatchMax];
+    void ClearSocketWatchPool();
+    void HandleSocketsAndTimerEvents(Clock::Timeout timeout);
+    CHIP_ERROR RequestCallback(SocketWatchToken token, SocketEventFlags flag);
+    CHIP_ERROR ClearCallback(SocketWatchToken token, SocketEventFlags flag);
+#endif
+
+    TimerPool<TimerList::Node> mTimerPool;
+    TimerList mTimerList;
+    // List of expired timers being processed right now.  Stored in a member so
+    // we can cancel them.
+    TimerList mExpiredTimers;
+    timeval mNextTimeout;
+    void EnableTimer(const char * source, TimerList::Node *);
+    void DisableTimer(const char * source, TimerList::Node *);
+    CHIP_ERROR StartTimer(Clock::Timeout delay, TimerCompleteCallback onComplete, void * appState, bool shouldCancel);
+    void HandleTimerEvents(Clock::Timeout timeout);
+
+    ObjectLifeCycle mLayerState;
+
+    dispatch_queue_t mDispatchQueue = nullptr;
+};
+
+using LayerImpl = LayerImplDispatch;
+
+} // namespace System
+} // namespace chip