| /****************************************************************************** |
| * |
| * Copyright (C) 2014 Google, Inc. |
| * |
| * 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. |
| * |
| ******************************************************************************/ |
| |
| #define LOG_TAG "bt_hci_packet_fragmenter" |
| |
| #include <assert.h> |
| #include <string.h> |
| |
| #include "buffer_allocator.h" |
| #include "device/include/controller.h" |
| #include "osi/include/hash_map.h" |
| #include "hci_internals.h" |
| #include "hci_layer.h" |
| #include "packet_fragmenter.h" |
| #include "osi/include/osi.h" |
| #include "osi/include/hash_functions.h" |
| #include "osi/include/log.h" |
| |
| #define APPLY_CONTINUATION_FLAG(handle) (((handle) & 0xCFFF) | 0x1000) |
| #define APPLY_START_FLAG(handle) (((handle) & 0xCFFF) | 0x2000) |
| #define SUB_EVENT(event) ((event) & MSG_SUB_EVT_MASK) |
| #define GET_BOUNDARY_FLAG(handle) (((handle) >> 12) & 0x0003) |
| |
| #define HANDLE_MASK 0x0FFF |
| #define START_PACKET_BOUNDARY 2 |
| #define CONTINUATION_PACKET_BOUNDARY 1 |
| #define L2CAP_HEADER_SIZE 4 |
| |
| // TODO(zachoverflow): find good value for this |
| #define NUMBER_OF_BUCKETS 42 |
| |
| // Our interface and callbacks |
| static const packet_fragmenter_t interface; |
| static const allocator_t *buffer_allocator; |
| static const controller_t *controller; |
| static const packet_fragmenter_callbacks_t *callbacks; |
| |
| static hash_map_t *partial_packets; |
| |
| static void init(const packet_fragmenter_callbacks_t *result_callbacks) { |
| callbacks = result_callbacks; |
| partial_packets = hash_map_new(NUMBER_OF_BUCKETS, hash_function_naive, NULL, NULL, NULL); |
| } |
| |
| static void cleanup() { |
| if (partial_packets) |
| hash_map_free(partial_packets); |
| } |
| |
| static void fragment_and_dispatch(BT_HDR *packet) { |
| assert(packet != NULL); |
| |
| uint16_t event = packet->event & MSG_EVT_MASK; |
| uint8_t *stream = packet->data + packet->offset; |
| |
| // We only fragment ACL packets |
| if (event != MSG_STACK_TO_HC_HCI_ACL) { |
| callbacks->fragmented(packet, true); |
| return; |
| } |
| |
| uint16_t max_data_size = |
| SUB_EVENT(packet->event) == LOCAL_BR_EDR_CONTROLLER_ID ? |
| controller->get_acl_data_size_classic() : |
| controller->get_acl_data_size_ble(); |
| |
| uint16_t max_packet_size = max_data_size + HCI_ACL_PREAMBLE_SIZE; |
| uint16_t remaining_length = packet->len; |
| |
| uint16_t continuation_handle; |
| STREAM_TO_UINT16(continuation_handle, stream); |
| continuation_handle = APPLY_CONTINUATION_FLAG(continuation_handle); |
| |
| while (remaining_length > max_packet_size) { |
| // Make sure we use the right ACL packet size |
| stream = packet->data + packet->offset; |
| STREAM_SKIP_UINT16(stream); |
| UINT16_TO_STREAM(stream, max_data_size); |
| |
| packet->len = max_packet_size; |
| callbacks->fragmented(packet, false); |
| |
| packet->offset += max_data_size; |
| remaining_length -= max_data_size; |
| packet->len = remaining_length; |
| |
| // Write the ACL header for the next fragment |
| stream = packet->data + packet->offset; |
| UINT16_TO_STREAM(stream, continuation_handle); |
| UINT16_TO_STREAM(stream, remaining_length - HCI_ACL_PREAMBLE_SIZE); |
| |
| // Apparently L2CAP can set layer_specific to a max number of segments to transmit |
| if (packet->layer_specific) { |
| packet->layer_specific--; |
| |
| if (packet->layer_specific == 0) { |
| packet->event = MSG_HC_TO_STACK_L2C_SEG_XMIT; |
| callbacks->transmit_finished(packet, false); |
| return; |
| } |
| } |
| } |
| |
| callbacks->fragmented(packet, true); |
| } |
| |
| static void reassemble_and_dispatch(UNUSED_ATTR BT_HDR *packet) { |
| if ((packet->event & MSG_EVT_MASK) == MSG_HC_TO_STACK_HCI_ACL) { |
| uint8_t *stream = packet->data; |
| uint16_t handle; |
| uint16_t l2cap_length; |
| uint16_t acl_length; |
| |
| STREAM_TO_UINT16(handle, stream); |
| STREAM_TO_UINT16(acl_length, stream); |
| STREAM_TO_UINT16(l2cap_length, stream); |
| |
| assert(acl_length == packet->len - HCI_ACL_PREAMBLE_SIZE); |
| |
| uint8_t boundary_flag = GET_BOUNDARY_FLAG(handle); |
| handle = handle & HANDLE_MASK; |
| |
| BT_HDR *partial_packet = (BT_HDR *)hash_map_get(partial_packets, (void *)(uintptr_t)handle); |
| |
| if (boundary_flag == START_PACKET_BOUNDARY) { |
| if (partial_packet) { |
| LOG_WARN("%s found unfinished packet for handle with start packet. Dropping old.", __func__); |
| |
| hash_map_erase(partial_packets, (void *)(uintptr_t)handle); |
| buffer_allocator->free(partial_packet); |
| } |
| |
| uint16_t full_length = l2cap_length + L2CAP_HEADER_SIZE + HCI_ACL_PREAMBLE_SIZE; |
| if (full_length <= packet->len) { |
| if (full_length < packet->len) |
| LOG_WARN("%s found l2cap full length %d less than the hci length %d.", __func__, l2cap_length, packet->len); |
| |
| callbacks->reassembled(packet); |
| return; |
| } |
| |
| partial_packet = (BT_HDR *)buffer_allocator->alloc(full_length + sizeof(BT_HDR)); |
| partial_packet->event = packet->event; |
| partial_packet->len = full_length; |
| partial_packet->offset = packet->len; |
| |
| memcpy(partial_packet->data, packet->data, packet->len); |
| |
| // Update the ACL data size to indicate the full expected length |
| stream = partial_packet->data; |
| STREAM_SKIP_UINT16(stream); // skip the handle |
| UINT16_TO_STREAM(stream, full_length - HCI_ACL_PREAMBLE_SIZE); |
| |
| hash_map_set(partial_packets, (void *)(uintptr_t)handle, partial_packet); |
| // Free the old packet buffer, since we don't need it anymore |
| buffer_allocator->free(packet); |
| } else { |
| if (!partial_packet) { |
| LOG_WARN("%s got continuation for unknown packet. Dropping it.", __func__); |
| buffer_allocator->free(packet); |
| return; |
| } |
| |
| packet->offset = HCI_ACL_PREAMBLE_SIZE; |
| uint16_t projected_offset = partial_packet->offset + (packet->len - HCI_ACL_PREAMBLE_SIZE); |
| if (projected_offset > partial_packet->len) { // len stores the expected length |
| LOG_WARN("%s got packet which would exceed expected length of %d. Truncating.", __func__, partial_packet->len); |
| packet->len = partial_packet->len - partial_packet->offset; |
| projected_offset = partial_packet->len; |
| } |
| |
| memcpy( |
| partial_packet->data + partial_packet->offset, |
| packet->data + packet->offset, |
| packet->len - packet->offset |
| ); |
| |
| // Free the old packet buffer, since we don't need it anymore |
| buffer_allocator->free(packet); |
| partial_packet->offset = projected_offset; |
| |
| if (partial_packet->offset == partial_packet->len) { |
| hash_map_erase(partial_packets, (void *)(uintptr_t)handle); |
| partial_packet->offset = 0; |
| callbacks->reassembled(partial_packet); |
| } |
| } |
| } else { |
| callbacks->reassembled(packet); |
| } |
| } |
| |
| static const packet_fragmenter_t interface = { |
| init, |
| cleanup, |
| |
| fragment_and_dispatch, |
| reassemble_and_dispatch |
| }; |
| |
| const packet_fragmenter_t *packet_fragmenter_get_interface() { |
| controller = controller_get_interface(); |
| buffer_allocator = buffer_allocator_get_interface(); |
| return &interface; |
| } |
| |
| const packet_fragmenter_t *packet_fragmenter_get_test_interface( |
| const controller_t *controller_interface, |
| const allocator_t *buffer_allocator_interface) { |
| controller = controller_interface; |
| buffer_allocator = buffer_allocator_interface; |
| return &interface; |
| } |