Potential fix for CBL-8382 and reachability fix port from 4.0

src/Couchbase.Lite.Shared/API/Sync/Replicator.cs

@@ -674,8 +674,8 @@ private void OnDocEndedWithConflict(List<ReplicatedDocument> replications)
 
             t.ContinueWith(task =>
             {
-                _conflictTasks.TryRemove(task, out var dummy);
-            }, cancelToken);
+                _conflictTasks.TryRemove(task, out _);
+            }, CancellationToken.None);
 
             _conflictTasks.TryAdd(t, 0);
         }
@@ -781,6 +781,11 @@ private void WaitPendingConflictTasks(C4ReplicatorStatus status)
             Task.WaitAll(array);
         } catch (TaskCanceledException) {
             WriteLog.To.Sync.I(Tag, "Conflict tasks were cancelled");
+        } catch (AggregateException e) when (e.InnerException is TaskCanceledException) {
+            // This happens on iOS on .NET 10 at least
+            WriteLog.To.Sync.I(Tag, "Conflict tasks were cancelled");
+        } catch (Exception e) {
+            WriteLog.To.Sync.W(Tag, "Exception waiting for conflict tasks", e);
         }
     }
 

src/Couchbase.Lite.Shared/Support/iOS/iOSReachability.cs

@@ -27,8 +27,6 @@
 using Couchbase.Lite.Internal.Logging;
 using Couchbase.Lite.Sync;
 
-using Foundation;
-
 using Network;
 
 namespace Couchbase.Lite.Support;
@@ -101,20 +99,57 @@ private void ValidateHostReachability(NetworkReachabilityFlags baseFlags)
             return;
         }
 
-        using var session = NSUrlSession.SharedSession;
-        var request = new NSUrlRequest(new NSUrl(Url.AbsoluteUri));
-
-        var task = session.CreateDataTask(request, (_, response, error) =>
+        var parameters = NWParameters.CreateTcp();
+        using var endpoint = NWEndpoint.Create(Url.Host, Url.Port.ToString());
+        if (endpoint == null) {
+            WriteLog.To.Sync.E(Tag, $"{Url} is not parseable for reachability check");
+            return;
+        }
+
+        var connection = new NWConnection(endpoint, parameters);
+        var flags = baseFlags;
+        var completed = false; // prevent re-entrancy / duplicate notifications after Cancel
+
+        connection.SetQueue(_queue);
+        connection.SetStateChangeHandler((state, error) =>
         {
-            var flags = baseFlags;
-            if (error.Code != 0 || response is NSHttpUrlResponse { StatusCode: >= 400 }) {
-                flags &= ~NetworkReachabilityFlags.Reachable;
+            // Ignore any subsequent callbacks once we've made a reachability decision
+            if (completed) {
+                WriteLog.To.Sync.V(Tag, $"Ignoring state after completion: {state}");
+                return;
+            }
+
+            if (error != null) {
+                WriteLog.To.Sync.W(Tag, $"Connection error to {Url}: {error}");
             }
 
-            NotifyFlagsChanged(flags);
+            switch (state) {
+                case NWConnectionState.Ready:
+                    flags |= NetworkReachabilityFlags.Reachable;
+                    NotifyFlagsChanged(flags);
+                    completed = true;
+                    // Replace handler with no-op before cancel to avoid processing Cancelled state
+                    connection.SetStateChangeHandler((_, _) => { });
+                    connection.Cancel();
+                    break;
+                case NWConnectionState.Failed:
+                    flags &= ~NetworkReachabilityFlags.Reachable;
+                    NotifyFlagsChanged(flags);
+                    completed = true;
+                    connection.SetStateChangeHandler((_, _) => { });
+                    connection.Cancel();
+                    break;
+                case NWConnectionState.Cancelled:
+                case NWConnectionState.Invalid:
+                case NWConnectionState.Waiting:
+                case NWConnectionState.Preparing:
+                default:
+                    WriteLog.To.Sync.V(Tag, $"Ignoring connection state: {state}");
+                    break;
+            }
         });
 
-        task.Resume();
+        connection.Start();
     }
 
     public void Start()