Fix Apple simulator and Swift 6 build plumbing

Apple/Configuration/Compiler.xcconfig

@@ -40,5 +40,4 @@ APP_GROUP_IDENTIFIER = group.$(APP_BUNDLE_IDENTIFIER)
 APP_GROUP_IDENTIFIER[sdk=macosx*] = $(DEVELOPMENT_TEAM).$(APP_BUNDLE_IDENTIFIER)
 NETWORK_EXTENSION_BUNDLE_IDENTIFIER = $(APP_BUNDLE_IDENTIFIER).network
 
-// https://github.com/grpc/grpc-swift/issues/683#issuecomment-1130118953
-OTHER_SWIFT_FLAGS = $(inherited) -Xcc -fmodule-map-file=$(GENERATED_MODULEMAP_DIR)/CNIOAtomics.modulemap -Xcc -fmodule-map-file=$(GENERATED_MODULEMAP_DIR)/CNIODarwin.modulemap -Xcc -fmodule-map-file=$(GENERATED_MODULEMAP_DIR)/CGRPCZlib.modulemap
+OTHER_SWIFT_FLAGS = $(inherited)

Apple/Configuration/Constants/Constants.swift

@@ -1,4 +1,5 @@
 @_implementationOnly import CConstants
+import Foundation
 import OSLog
 
 public enum Constants {
@@ -27,9 +28,30 @@ public enum Constants {
     private static let _groupContainerURL: Result<URL, Error> = {
         switch FileManager.default.containerURL(forSecurityApplicationGroupIdentifier: appGroupIdentifier) {
         case .some(let url): .success(url)
-        case .none: .failure(.invalidAppGroupIdentifier)
+        case .none:
+            fallbackContainerURL().mapError { _ in .invalidAppGroupIdentifier }
         }
     }()
+
+    private static func fallbackContainerURL() -> Result<URL, any Swift.Error> {
+#if targetEnvironment(simulator)
+        Result {
+            let baseURL = try FileManager.default.url(
+                for: .applicationSupportDirectory,
+                in: .userDomainMask,
+                appropriateFor: nil,
+                create: true
+            )
+            let url = baseURL
+                .appending(component: bundleIdentifier, directoryHint: .isDirectory)
+                .appending(component: "SimulatorFallback", directoryHint: .isDirectory)
+            try FileManager.default.createDirectory(at: url, withIntermediateDirectories: true)
+            return url
+        }
+#else
+        .failure(Error.invalidAppGroupIdentifier)
+#endif
+    }
 }
 
 extension Logger {

Apple/Core/Client/google/protobuf/timestamp.proto

@@ -0,0 +1,64 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+syntax = "proto3";
+
+package google.protobuf;
+
+option cc_enable_arenas = true;
+option go_package = "google.golang.org/protobuf/types/known/timestamppb";
+option java_package = "com.google.protobuf";
+option java_outer_classname = "TimestampProto";
+option java_multiple_files = true;
+option objc_class_prefix = "GPB";
+option csharp_namespace = "Google.Protobuf.WellKnownTypes";
+
+// A Timestamp represents a point in time independent of any time zone or local
+// calendar, encoded as a count of seconds and fractions of seconds at
+// nanosecond resolution. The count is relative to an epoch at UTC midnight on
+// January 1, 1970, in the proleptic Gregorian calendar which extends the
+// Gregorian calendar backwards to year one.
+//
+// All minutes are 60 seconds long. Leap seconds are "smeared" so that no leap
+// second table is needed for interpretation, using a 24-hour linear smear.
+//
+// The range is from 0001-01-01T00:00:00Z to 9999-12-31T23:59:59.999999999Z. By
+// restricting to that range, we ensure that we can convert to and from RFC
+// 3339 date strings.
+message Timestamp {
+  // Represents seconds of UTC time since Unix epoch 1970-01-01T00:00:00Z.
+  // Must be from 0001-01-01T00:00:00Z to 9999-12-31T23:59:59Z inclusive.
+  int64 seconds = 1;
+
+  // Non-negative fractions of a second at nanosecond resolution. Negative
+  // second values with fractions must still have non-negative nanos values
+  // that count forward in time. Must be from 0 to 999,999,999 inclusive.
+  int32 nanos = 2;
+}

Apple/NetworkExtension/PacketTunnelProvider.swift

@@ -5,7 +5,15 @@ import libburrow
 import NetworkExtension
 import os
 
-class PacketTunnelProvider: NEPacketTunnelProvider {
+private final class SendableCallbackBox<Callback>: @unchecked Sendable {
+    let callback: Callback
+
+    init(_ callback: Callback) {
+        self.callback = callback
+    }
+}
+
+final class PacketTunnelProvider: NEPacketTunnelProvider, @unchecked Sendable {
     enum Error: Swift.Error {
         case missingTunnelConfiguration
     }
@@ -30,27 +38,41 @@ class PacketTunnelProvider: NEPacketTunnelProvider {
         }
     }
 
-    override func startTunnel(options: [String: NSObject]? = nil) async throws {
-        do {
-            let configuration = try await Array(client.tunnelConfiguration(.init()).prefix(1)).first
-            guard let settings = configuration?.settings else {
-                throw Error.missingTunnelConfiguration
+    override func startTunnel(
+        options: [String: NSObject]?,
+        completionHandler: @escaping (Swift.Error?) -> Void
+    ) {
+        let completion = SendableCallbackBox(completionHandler)
+        Task {
+            do {
+                let configuration = try await Array(client.tunnelConfiguration(.init()).prefix(1)).first
+                guard let settings = configuration?.settings else {
+                    throw Error.missingTunnelConfiguration
+                }
+                try await setTunnelNetworkSettings(settings)
+                _ = try await client.tunnelStart(.init())
+                logger.log("Started tunnel with network settings: \(settings)")
+                completion.callback(nil)
+            } catch {
+                logger.error("Failed to start tunnel: \(error)")
+                completion.callback(error)
             }
-            try await setTunnelNetworkSettings(settings)
-            _ = try await client.tunnelStart(.init())
-            logger.log("Started tunnel with network settings: \(settings)")
-        } catch {
-            logger.error("Failed to start tunnel: \(error)")
-            throw error
         }
     }
 
-    override func stopTunnel(with reason: NEProviderStopReason) async {
-        do {
-            _ = try await client.tunnelStop(.init())
-            logger.log("Stopped client")
-        } catch {
-            logger.error("Failed to stop tunnel: \(error)")
+    override func stopTunnel(
+        with reason: NEProviderStopReason,
+        completionHandler: @escaping () -> Void
+    ) {
+        let completion = SendableCallbackBox(completionHandler)
+        Task {
+            do {
+                _ = try await client.tunnelStop(.init())
+                logger.log("Stopped client")
+            } catch {
+                logger.error("Failed to stop tunnel: \(error)")
+            }
+            completion.callback()
         }
     }
 }

Apple/NetworkExtension/libburrow/build-rust.sh

@@ -73,7 +73,21 @@ CARGO_PATH="$(dirname $PROTOC):$CARGO_PATH"
 
 # Run cargo without the various environment variables set by Xcode.
 # Those variables can confuse cargo and the build scripts it runs.
-env -i PATH="$CARGO_PATH" PROTOC="$PROTOC" CARGO_TARGET_DIR="${CONFIGURATION_TEMP_DIR}/target" IPHONEOS_DEPLOYMENT_TARGET="$IPHONEOS_DEPLOYMENT_TARGET" MACOSX_DEPLOYMENT_TARGET="$MACOSX_DEPLOYMENT_TARGET" cargo build "${CARGO_ARGS[@]}"
+CARGO_ENV=(
+    "PATH=$CARGO_PATH"
+    "PROTOC=$PROTOC"
+    "CARGO_TARGET_DIR=${CONFIGURATION_TEMP_DIR}/target"
+)
+
+if [[ -n "$IPHONEOS_DEPLOYMENT_TARGET" ]]; then
+    CARGO_ENV+=("IPHONEOS_DEPLOYMENT_TARGET=$IPHONEOS_DEPLOYMENT_TARGET")
+fi
+
+if [[ -n "$MACOSX_DEPLOYMENT_TARGET" ]]; then
+    CARGO_ENV+=("MACOSX_DEPLOYMENT_TARGET=$MACOSX_DEPLOYMENT_TARGET")
+fi
+
+env -i "${CARGO_ENV[@]}" cargo build "${CARGO_ARGS[@]}"
 
 mkdir -p "${BUILT_PRODUCTS_DIR}"