Add GNCBLEL2CAPConnection

PiperOrigin-RevId: 750016094

internal/platform/implementation/apple/Mediums/BLEv2/GNCBLEL2CAPConnection.h

@@ -0,0 +1,52 @@
+// Copyright 2025 Google LLC
+//
+// 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
+//
+//     https://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.
+
+#import "internal/platform/implementation/apple/Mediums/GNCMConnection.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+@class GNCBLEL2CAPStream;
+
+/**
+ * A GNCBLEL2CAPConnection implementation for BLE L2CAP.
+ * This class is thread-safe.
+ */
+@interface GNCBLEL2CAPConnection : NSObject
+@property(nonatomic) GNCMConnectionHandlers *connectionHandlers;
+
+/*
+ * Creates a |GNCBLEL2CAPConnection|.
+ *
+ * @param stream A |GNCL2CAPStream| instance.
+ * @param serviceID A string that uniquely identifies the service.
+ * @param incomingConnection A flag to indicate the connection is incoming.
+ * @param callbackQueue The queue on which all callbacks are made.
+ */
++ (instancetype)connectionWithStream:(GNCBLEL2CAPStream *)stream
+                           serviceID:(nullable NSString *)serviceID
+                 incomingConnection:(BOOL)incomingConnection
+                       callbackQueue:(dispatch_queue_t)callbackQueue;
+
+/**
+ * Sends data to the remote device.
+ *
+ * @param payload The data to send.
+ * @param completion A block that is called when the data has been sent. The block takes a BOOL
+ *        parameter indicating whether the data was sent successfully.
+ */
+- (void)sendData:(NSData *)payload completion:(void (^)(BOOL))completion;
+
+@end
+
+NS_ASSUME_NONNULL_END

internal/platform/implementation/apple/Mediums/BLEv2/GNCBLEL2CAPConnection.m

@@ -0,0 +1,158 @@
+// Copyright 2025 Google LLC
+//
+// 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
+//
+//     https://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.
+
+#import "internal/platform/implementation/apple/Mediums/BLEv2/GNCBLEL2CAPConnection.h"
+
+#import <Foundation/Foundation.h>
+
+#import "internal/platform/implementation/apple/Mediums/BLEv2/GNCBLEL2CAPStream.h"
+#import "internal/platform/implementation/apple/Mediums/Ble/GNCMBleUtils.h"
+#import "internal/platform/implementation/apple/Mediums/GNCLeaks.h"
+#import "internal/platform/implementation/apple/Mediums/GNCMConnection.h"
+#import "GoogleToolboxForMac/GTMLogger.h"
+
+enum { kL2CAPPacketLength = 4 };
+
+static char *const kGNCBLEL2CAPConnectionQueueLabel = "com.google.nearby.GNCBLEL2CAPConnection";
+
+static NSData *PrefixDataWithServiceIDHash(NSData *serviceIDHash, NSData *data) {
+  NSMutableData *combinedData = [NSMutableData dataWithCapacity:serviceIDHash.length + data.length];
+
+  [combinedData appendData:serviceIDHash];
+  [combinedData appendData:data];
+
+  return combinedData;
+}
+
+static NSData *PrefixLengthData(NSData *data) {
+  uint32_t dataLength = (uint32_t)data.length;
+  uint32_t lengthBigEndian = CFSwapInt32HostToBig(dataLength);
+
+  NSMutableData *packet = [NSMutableData dataWithCapacity:sizeof(uint32_t)];
+  [packet appendBytes:&lengthBigEndian length:sizeof(uint32_t)];
+  [packet appendData:data];
+
+  return packet;
+}
+
+@interface GNCBLEL2CAPConnection () <GNCBLEL2CAPStreamDelegate>
+@property(nonatomic) dispatch_queue_t selfQueue;
+@property(nonatomic) GNCBLEL2CAPStream *stream;
+@property(nonatomic) NSData *serviceIDHash;
+@property(nonatomic) dispatch_queue_t callbackQueue;
+@property(nonatomic) BOOL incomingConnection;
+@end
+
+@implementation GNCBLEL2CAPConnection
+
++ (instancetype)connectionWithStream:(GNCBLEL2CAPStream *)stream
+                           serviceID:(NSString *)serviceID
+                  incomingConnection:(BOOL)incomingConnection
+                       callbackQueue:(dispatch_queue_t)callbackQueue {
+  GNCBLEL2CAPConnection *connection = [[GNCBLEL2CAPConnection alloc] init];
+  [connection setStream:stream];
+  stream.delegate = connection;
+  [connection setServiceIDHash:GNCMServiceIDHash(serviceID)];
+  [connection setCallbackQueue:callbackQueue];
+  [connection
+      setSelfQueue:dispatch_queue_create(kGNCBLEL2CAPConnectionQueueLabel,
+                                         dispatch_queue_attr_make_with_qos_class(
+                                             DISPATCH_QUEUE_SERIAL, QOS_CLASS_USER_INITIATED, -1))];
+  [connection setIncomingConnection:incomingConnection];
+  return connection;
+}
+
+- (void)dealloc {
+  [_stream close];
+  GNCVerifyDealloc(_stream, 2);  // assert if not deallocated
+}
+
+#pragma mark GNCBLEL2CAPConnection
+
+- (void)sendData:(NSData *)data completion:(void (^)(BOOL))completion {
+  dispatch_async(_selfQueue, ^{
+    NSData *packet;
+
+    // Prefix the service ID hash.
+    packet = PrefixLengthData(PrefixDataWithServiceIDHash(_serviceIDHash, data));
+    GTMLoggerInfo(@"[NEARBY] GNCBLEL2CAPConnection data to be sent: %@", [packet description]);
+    [_stream sendData:packet
+        completionBlock:^(BOOL result) {
+          dispatch_async(_callbackQueue, ^{
+            completion(result);
+          });
+        }];
+  });
+}
+
+#pragma mark GNCBLEL2CAPStreamDelegate
+
+- (void)stream:(GNCBLEL2CAPStream *)stream didReceiveData:(NSData *)data {
+  GTMLoggerDebug(@"[NEARBY] BLEL2CAPConnection didReceiveData, data: %@", [data description]);
+
+  NSData *realData = [self extractRealDataFromData:data];
+  if (realData == nil) {
+    return;
+  }
+
+  // Validate the L2CAP packet.
+  // TODO: b/399815436 - Refactor the validation logic to connections layer.
+ 
+  // Extract the service ID prefix from each data packet and validate it.
+  NSUInteger prefixLength = _serviceIDHash.length;
+  if (![[realData subdataWithRange:NSMakeRange(0, prefixLength)] isEqual:_serviceIDHash]) {
+    GTMLoggerInfo(@"[NEARBY]: Received wrong data packet and discarded");
+    return;
+  }
+
+  dispatch_async(_selfQueue, ^{
+    if (_connectionHandlers.payloadHandler) {
+      dispatch_async(_callbackQueue, ^{
+        _connectionHandlers.payloadHandler([NSData
+            dataWithData:[realData subdataWithRange:NSMakeRange(prefixLength,
+                                                                realData.length - prefixLength)]]);
+      });
+    }
+  });
+}
+
+- (void)stream:(GNCBLEL2CAPStream *)stream didDisconnectWithError:(NSError *_Nullable)error {
+  dispatch_async(_selfQueue, ^{
+    if (_connectionHandlers.disconnectedHandler) {
+      dispatch_async(_callbackQueue, ^{
+        _connectionHandlers.disconnectedHandler();
+      });
+    }
+  });
+}
+
+#pragma mark Private
+
+- (NSData *_Nullable)extractRealDataFromData:(NSData *)data {
+  if (data.length < kL2CAPPacketLength) {
+    GTMLoggerError(@"[NEARBY] Packet length mismatch. Expected: > %d, Actual: %lu",
+                   kL2CAPPacketLength, data.length);
+    return nil;
+  }
+  int realDataLength = CFSwapInt32BigToHost(
+      *(int *)([[data subdataWithRange:NSMakeRange(0, kL2CAPPacketLength)] bytes]));
+  if (realDataLength != (data.length - kL2CAPPacketLength)) {
+    GTMLoggerError(@"[NEARBY] Data length mismatch. Expected: %d, Actual: %lu",
+                   realDataLength, data.length - kL2CAPPacketLength);
+    return nil;
+  }
+  return [data subdataWithRange:NSMakeRange(kL2CAPPacketLength, data.length - kL2CAPPacketLength)];
+}
+
+@end

internal/platform/implementation/apple/Mediums/BLEv2/GNCBLEL2CAPStream.h

@@ -14,6 +14,8 @@
 
 #import <Foundation/Foundation.h>
 
+@class GNCBLEL2CAPStream;
+
 NS_ASSUME_NONNULL_BEGIN
 
 /// Block invoked when the stream is closed.
@@ -22,6 +24,23 @@ typedef void (^GNCBLEL2CAPStreamClosedBlock)(void);
 /// Block invoked when |data| is received from the remote device on the L2CAP connection.
 typedef void (^GNCBLEL2CAPControllerReceivedDataBlock)(NSData *data);
 
+/** Delegate for @c GNCBLEL2CAPStream. */
+@protocol GNCBLEL2CAPStreamDelegate <NSObject>
+
+/**
+ * Called when data is received from the remote device on the L2CAP connection.
+ *
+ * @param data The data received from the remote device.
+ */
+- (void)stream:(GNCBLEL2CAPStream *)stream didReceiveData:(NSData *)data;
+
+/**
+ * Called when the stream is closed.
+ */
+- (void)stream:(GNCBLEL2CAPStream *)stream didDisconnectWithError:(NSError *_Nullable)error;
+
+@end
+            
 /**
  * Abstraction to take in two streams returned from L2CAP controller and provide a simplified
  * interface to send and receive data from the streams.
@@ -29,6 +48,9 @@ typedef void (^GNCBLEL2CAPControllerReceivedDataBlock)(NSData *data);
  */
 @interface GNCBLEL2CAPStream : NSObject
 
+/// Delegate for @c GNCBLEL2CAPStream
+@property(nonatomic, weak) id<GNCBLEL2CAPStreamDelegate> delegate;
+
 /// Returns an instance of @c GNCBLEL2CAPStream which sends and receives data on |inputStream|
 /// and |outputStream|.
 /// Invokes |closedBlock| if stream closed signal is received when reading data.

internal/platform/implementation/apple/Mediums/BLEv2/GNCBLEL2CAPStream.m

@@ -320,6 +320,8 @@
     }
 
     dispatch_async(_receivedDataQueue, ^{
+      [_delegate stream:self didReceiveData:data];
+      // TODO: b/399815436 - Remove below once the delegate is implemented.
       self->_receivedDataBlock(data);
     });
   } else if (bytesRead < 0) {
@@ -328,6 +330,7 @@
     GTMLoggerDebug(@"[NEARBY] End of stream reached. Disconnecting");
     // This indicates the L2CAP socket is closed. Notifying the owner so that it can tear down this
     // stream and update its own state.
+    [_delegate stream:self didDisconnectWithError:nil];
     _closedBlock();
   }
 }

internal/platform/implementation/apple/Mediums/BUILD

@@ -27,6 +27,7 @@ objc_library(
         "BLEv2/GNCBLEGATTClient.m",
         "BLEv2/GNCBLEGATTServer.m",
         "BLEv2/GNCBLEL2CAPClient.m",
+        "BLEv2/GNCBLEL2CAPConnection.m",
         "BLEv2/GNCBLEL2CAPServer.m",
         "BLEv2/GNCBLEL2CAPStream.m",
         "BLEv2/GNCBLEMedium.m",
@@ -55,6 +56,7 @@ objc_library(
         "BLEv2/GNCBLEGATTClient.h",
         "BLEv2/GNCBLEGATTServer.h",
         "BLEv2/GNCBLEL2CAPClient.h",
+        "BLEv2/GNCBLEL2CAPConnection.h",
         "BLEv2/GNCBLEL2CAPServer.h",
         "BLEv2/GNCBLEL2CAPStream.h",
         "BLEv2/GNCBLEMedium.h",