Kit: make it possible to opt-out from automatically raising the reasserting flag.

Signed-off-by: Andrej Mihajlov <and@mullvad.net>

Sources/WireGuardKit/WireGuardAdapter.swift

@@ -56,6 +56,10 @@ public class WireGuardAdapter {
     /// Adapter state.
     private var state: State = .stopped
 
+    /// Whether adapter should automatically raise the `reasserting` flag when updating
+    /// tunnel configuration.
+    private let shouldHandleReasserting: Bool
+
     /// Tunnel device file descriptor.
     private var tunnelFileDescriptor: Int32? {
         var ctlInfo = ctl_info()
@@ -128,9 +132,12 @@ public class WireGuardAdapter {
     /// Designated initializer.
     /// - Parameter packetTunnelProvider: an instance of `NEPacketTunnelProvider`. Internally stored
     ///   as a weak reference.
+    /// - Parameter shouldHandleReasserting: whether adapter should automatically raise the
+    ///   `reasserting` flag when updating tunnel configuration.
     /// - Parameter logHandler: a log handler closure.
-    public init(with packetTunnelProvider: NEPacketTunnelProvider, logHandler: @escaping LogHandler) {
+    public init(with packetTunnelProvider: NEPacketTunnelProvider, shouldHandleReasserting: Bool = true, logHandler: @escaping LogHandler) {
         self.packetTunnelProvider = packetTunnelProvider
+        self.shouldHandleReasserting = shouldHandleReasserting
         self.logHandler = logHandler
 
         setupLogHandler()
@@ -248,40 +255,68 @@ public class WireGuardAdapter {
             // Tell the system that the tunnel is going to reconnect using new WireGuard
             // configuration.
             // This will broadcast the `NEVPNStatusDidChange` notification to the GUI process.
-            self.packetTunnelProvider?.reasserting = true
-            defer {
-                self.packetTunnelProvider?.reasserting = false
+            if self.shouldHandleReasserting {
+                self.packetTunnelProvider?.reasserting = true
             }
 
-            do {
-                let settingsGenerator = try self.makeSettingsGenerator(with: tunnelConfiguration)
-                try self.setNetworkSettings(settingsGenerator.generateNetworkSettings())
-
-                switch self.state {
-                case .started(let handle, _):
-                    let (wgConfig, resolutionResults) = settingsGenerator.uapiConfiguration()
-                    self.logEndpointResolutionResults(resolutionResults)
-
-                    wgSetConfig(handle, wgConfig)
-                    #if os(iOS)
-                    wgDisableSomeRoamingForBrokenMobileSemantics(handle)
-                    #endif
-
-                    self.state = .started(handle, settingsGenerator)
-
-                case .temporaryShutdown:
-                    self.state = .temporaryShutdown(settingsGenerator)
-
-                case .stopped:
-                    fatalError()
+            defer {
+                if self.shouldHandleReasserting {
+                    self.packetTunnelProvider?.reasserting = false
                 }
+            }
 
-                completionHandler(nil)
+            let settingsGenerator: PacketTunnelSettingsGenerator
+            do {
+                settingsGenerator = try self.makeSettingsGenerator(with: tunnelConfiguration)
             } catch let error as WireGuardAdapterError {
                 completionHandler(error)
+                return
             } catch {
                 fatalError()
             }
+
+            switch self.state {
+            case .started(let handle, _):
+                do {
+                    try self.setNetworkSettings(settingsGenerator.generateNetworkSettings())
+                } catch let error as WireGuardAdapterError {
+                    completionHandler(error)
+                    return
+                } catch {
+                    fatalError()
+                }
+
+                let (wgConfig, resolutionResults) = settingsGenerator.uapiConfiguration()
+                self.logEndpointResolutionResults(resolutionResults)
+
+                wgSetConfig(handle, wgConfig)
+                #if os(iOS)
+                wgDisableSomeRoamingForBrokenMobileSemantics(handle)
+                #endif
+
+                self.state = .started(handle, settingsGenerator)
+
+            case .temporaryShutdown:
+                // On iOS 15.1 or newer, updating network settings may fail when in airplane mode.
+                // Network path monitor will retry updating settings later when connectivity is
+                // back online.
+                do {
+                    try self.setNetworkSettings(settingsGenerator.generateNetworkSettings())
+                } catch let error as WireGuardAdapterError {
+                    if case .setNetworkSettings(let systemError) = error {
+                        self.logHandler(.verbose, "Failed to set network settings while offline. Will retry when connectivity is back online. Error: \(systemError.localizedDescription)")
+                    }
+                } catch {
+                    fatalError()
+                }
+
+                self.state = .temporaryShutdown(settingsGenerator)
+
+            case .stopped:
+                fatalError()
+            }
+
+            completionHandler(nil)
         }
     }