src/connectivity/bluetooth/core/bt-host/hci/acl_data_packet.cc

// Copyright 2017 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "acl_data_packet.h"

#include <endian.h>
#include <zircon/assert.h>

#include "slab_allocators.h"
#include "src/connectivity/bluetooth/core/bt-host/common/log.h"

namespace bt::hci {
namespace slab_allocators {

// Slab-allocator traits for ACL data packets.
using LargeACLTraits =
    PacketTraits<ACLDataHeader, kLargeACLDataPacketSize, kNumLargeACLDataPackets>;
using MediumACLTraits =
    PacketTraits<ACLDataHeader, kMediumACLDataPacketSize, kNumMediumACLDataPackets>;
using SmallACLTraits =
    PacketTraits<ACLDataHeader, kSmallACLDataPacketSize, kNumSmallACLDataPackets>;

using LargeACLAllocator = fbl::SlabAllocator<LargeACLTraits>;
using MediumACLAllocator = fbl::SlabAllocator<MediumACLTraits>;
using SmallACLAllocator = fbl::SlabAllocator<SmallACLTraits>;

}  // namespace slab_allocators

namespace {

// Type containing both a fixed packet storage buffer and a ACLDataPacket interface to the buffer.
// Does not deallocate from a slab buffer when destroyed (unlike SlabPacket).
using LargeACLDataPacket =
    slab_allocators::internal::FixedSizePacket<ACLDataHeader,
                                               slab_allocators::kLargeACLDataPacketSize>;

ACLDataPacketPtr NewACLDataPacket(size_t payload_size) {
  ZX_ASSERT_MSG(payload_size <= slab_allocators::kLargeACLDataPayloadSize,
                "payload size %zu too large (allowed = %zu)", payload_size,
                slab_allocators::kLargeACLDataPayloadSize);

  if (payload_size <= slab_allocators::kSmallACLDataPayloadSize) {
    auto buffer = slab_allocators::SmallACLAllocator::New(payload_size);
    if (buffer) {
      return buffer;
    }

    // Fall back to the next allocator.
  }

  if (payload_size <= slab_allocators::kMediumACLDataPayloadSize) {
    auto buffer = slab_allocators::MediumACLAllocator::New(payload_size);
    if (buffer) {
      return buffer;
    }

    // Fall back to the next allocator.
  }

  auto buffer = slab_allocators::LargeACLAllocator::New(payload_size);
  if (buffer) {
    return buffer;
  }

  bt_log(TRACE, "hci", "ACLDataPacket slab allocators capacity exhausted");

  // Fall back to system allocator.
  return std::make_unique<LargeACLDataPacket>(payload_size);
}

}  // namespace

// static
ACLDataPacketPtr ACLDataPacket::New(uint16_t payload_size) {
  return NewACLDataPacket(payload_size);
}

// static
ACLDataPacketPtr ACLDataPacket::New(ConnectionHandle connection_handle,
                                    ACLPacketBoundaryFlag packet_boundary_flag,
                                    ACLBroadcastFlag broadcast_flag, uint16_t payload_size) {
  auto packet = NewACLDataPacket(payload_size);
  if (!packet)
    return nullptr;

  packet->WriteHeader(connection_handle, packet_boundary_flag, broadcast_flag);
  return packet;
}

ConnectionHandle ACLDataPacket::connection_handle() const {
  // Return the lower 12-bits of the first two octets.
  return le16toh(ACLDataPacket::view().header().handle_and_flags) & 0x0FFF;
}

ACLPacketBoundaryFlag ACLDataPacket::packet_boundary_flag() const {
  // Return bits 4-5 in the higher octet of |handle_and_flags| or
  // "0b00xx000000000000".
  return static_cast<ACLPacketBoundaryFlag>(
      (le16toh(ACLDataPacket::view().header().handle_and_flags) >> 12) & 0x0003);
}

ACLBroadcastFlag ACLDataPacket::broadcast_flag() const {
  // Return bits 6-7 in the higher octet of |handle_and_flags| or
  // "0bxx00000000000000".
  return static_cast<ACLBroadcastFlag>(le16toh(view().header().handle_and_flags) >> 14);
}

void ACLDataPacket::InitializeFromBuffer() {
  mutable_view()->Resize(le16toh(view().header().data_total_length));
}

void ACLDataPacket::WriteHeader(ConnectionHandle connection_handle,
                                ACLPacketBoundaryFlag packet_boundary_flag,
                                ACLBroadcastFlag broadcast_flag) {
  // Must fit inside 12-bits.
  ZX_DEBUG_ASSERT(connection_handle <= 0x0FFF);

  // Must fit inside 2-bits.
  ZX_DEBUG_ASSERT(static_cast<uint8_t>(packet_boundary_flag) <= 0x03);
  ZX_DEBUG_ASSERT(static_cast<uint8_t>(broadcast_flag) <= 0x03);

  uint16_t handle_and_flags = connection_handle |
                              (static_cast<uint16_t>(packet_boundary_flag) << 12) |
                              (static_cast<uint16_t>(broadcast_flag) << 14);
  mutable_view()->mutable_header()->handle_and_flags = htole16(handle_and_flags);
  mutable_view()->mutable_header()->data_total_length = htole16(view().payload_size());
}

}  // namespace bt::hci

DECLARE_STATIC_SLAB_ALLOCATOR_STORAGE(bt::hci::slab_allocators::LargeACLTraits,
                                      bt::hci::slab_allocators::kMaxNumSlabs, true);
DECLARE_STATIC_SLAB_ALLOCATOR_STORAGE(bt::hci::slab_allocators::MediumACLTraits,
                                      bt::hci::slab_allocators::kMaxNumSlabs, true);
DECLARE_STATIC_SLAB_ALLOCATOR_STORAGE(bt::hci::slab_allocators::SmallACLTraits,
                                      bt::hci::slab_allocators::kMaxNumSlabs, true);