drivers/bluetooth/lib/l2cap/recombiner.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 "recombiner.h"

#include "lib/fxl/logging.h"

namespace btlib {
namespace l2cap {
namespace {

const BasicHeader& GetBasicHeader(const hci::ACLDataPacket& fragment) {
  FXL_DCHECK(fragment.packet_boundary_flag() !=
             hci::ACLPacketBoundaryFlag::kContinuingFragment);
  return fragment.view().payload<BasicHeader>();
}

}  // namespace

Recombiner::Recombiner() : ready_(false), frame_length_(0u), cur_length_(0u) {}

bool Recombiner::AddFragment(hci::ACLDataPacketPtr&& fragment) {
  FXL_DCHECK(fragment);

  if (ready())
    return false;

  if (empty()) {
    if (!ProcessFirstFragment(*fragment))
      return false;
    FXL_DCHECK(!empty());
  } else {
    if (fragment->packet_boundary_flag() !=
        hci::ACLPacketBoundaryFlag::kContinuingFragment) {
      FXL_VLOG(2) << "Expected continuing fragment!";
      return false;
    }

    if (cur_length_ + fragment->view().payload_size() > frame_length_) {
      FXL_VLOG(2) << "Continuing fragment too long!";
      return false;
    }
  }

  cur_length_ += fragment->view().payload_size();
  if (frame_length_ == cur_length_) {
    // The PDU is complete.
    ready_ = true;
  }

  pdu_->AppendFragment(std::move(fragment));
  return true;
}

bool Recombiner::Release(PDU* out_pdu) {
  if (empty() || !ready())
    return false;

  FXL_DCHECK(out_pdu);

  *out_pdu = std::move(*pdu_);
  Drop();

  return true;
}

void Recombiner::Drop() {
  ready_ = false;
  frame_length_ = 0u;
  cur_length_ = 0u;
  pdu_.Reset();
}

bool Recombiner::ProcessFirstFragment(const hci::ACLDataPacket& fragment) {
  FXL_DCHECK(!ready());
  FXL_DCHECK(!frame_length_);
  FXL_DCHECK(!cur_length_);

  // The first fragment needs to at least contain the Basic L2CAP header and
  // should not be a continuation fragment.
  if (fragment.packet_boundary_flag() ==
          hci::ACLPacketBoundaryFlag::kContinuingFragment ||
      fragment.view().payload_size() < sizeof(BasicHeader)) {
    FXL_VLOG(2) << "Bad first fragment";
    return false;
  }

  uint16_t frame_length =
      le16toh(GetBasicHeader(fragment).length) + sizeof(BasicHeader);

  if (fragment.view().payload_size() > frame_length) {
    FXL_VLOG(2) << "Fragment too long!";
    return false;
  }

  pdu_ = PDU();
  frame_length_ = frame_length;

  return true;
}

}  // namespace l2cap
}  // namespace btlib