/******************************************************************************
*
* 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.
*
******************************************************************************/
#include <string.h>
#include "common/bt_trace.h"
#include "common/bt_defs.h"
#include "device/controller.h"
#include "hci/hci_internals.h"
#include "hci/hci_layer.h"
#include "hci/packet_fragmenter.h"
#include "osi/hash_map.h"
#include "osi/hash_functions.h"
#include "common/bt_trace.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 controller_t *controller;
static const packet_fragmenter_callbacks_t *callbacks;
static hash_map_t *partial_packets;
static BT_HDR *current_fragment_packet;
static void init(const packet_fragmenter_callbacks_t *result_callbacks)
{
current_fragment_packet = NULL;
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 BT_HDR *fragment_get_current_packet()
{
return current_fragment_packet;
}
static void fragment_and_dispatch(BT_HDR *packet)
{
uint16_t continuation_handle;
uint16_t max_data_size, max_packet_size, remaining_length;
uint16_t event = packet->event & MSG_EVT_MASK;
uint8_t *stream = packet->data + packet->offset;
assert(packet != NULL);
// We only fragment ACL packets
if (event != MSG_STACK_TO_HC_HCI_ACL) {
callbacks->fragmented(packet, true);
return;
}
max_data_size =
SUB_EVENT(packet->event) == LOCAL_BR_EDR_CONTROLLER_ID ?
controller->get_acl_data_size_classic() :
controller->get_acl_data_size_ble();
max_packet_size = max_data_size + HCI_ACL_PREAMBLE_SIZE;
remaining_length = packet->len;
STREAM_TO_UINT16(continuation_handle, stream);
continuation_handle = APPLY_CONTINUATION_FLAG(continuation_handle);
if (remaining_length > max_packet_size) {
current_fragment_packet = packet;
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;
/* The remain packet will send back to the l2cap layer when controller buffer is not enough
current_fragment_packet must be NULL, otherwise hci_host_thread_handler() will
connitue handle the remain packet. then the remain packet will be freed.
*/
current_fragment_packet = NULL;
callbacks->transmit_finished(packet, false);
return;
}
}
} else {
current_fragment_packet = NULL;
callbacks->fragmented(packet, true);
}
}
static void reassemble_and_dispatch(BT_HDR *packet)
{
HCI_TRACE_DEBUG("reassemble_and_dispatch\n");
if ((packet->event & MSG_EVT_MASK) == MSG_HC_TO_STACK_HCI_ACL) {
uint8_t *stream = packet->data + packet->offset;
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) {
HCI_TRACE_WARNING("%s found unfinished packet for handle with start packet. Dropping old.\n", __func__);
hash_map_erase(partial_packets, (void *)(uintptr_t)handle);
osi_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) {
HCI_TRACE_WARNING("%s found l2cap full length %d less than the hci length %d.\n", __func__, l2cap_length, packet->len);
}
callbacks->reassembled(packet);
return;
}
partial_packet = (BT_HDR *)osi_calloc(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->offset, 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
osi_free(packet);
} else {
if (!partial_packet) {
HCI_TRACE_ERROR("%s got continuation for unknown packet. Dropping it.\n", __func__);
osi_free(packet);
return;
}
packet->offset += HCI_ACL_PREAMBLE_SIZE; // skip ACL preamble
packet->len -= HCI_ACL_PREAMBLE_SIZE;
uint16_t projected_offset = partial_packet->offset + packet->len;
if (projected_offset > partial_packet->len) { // len stores the expected length
HCI_TRACE_ERROR("%s got packet which would exceed expected length of %d. Truncating.\n", __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
);
// Free the old packet buffer, since we don't need it anymore
osi_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_get_current_packet,
fragment_and_dispatch,
reassemble_and_dispatch
};
const packet_fragmenter_t *packet_fragmenter_get_interface()
{
controller = controller_get_interface();
return &interface;
}