host/hci/low_energy_connector.cc

// Copyright 2023 The Pigweed Authors
//
// 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.

#include "pw_bluetooth_sapphire/internal/host/hci/low_energy_connector.h"

#include <endian.h>

#include "pw_bluetooth_sapphire/internal/host/common/assert.h"
#include "pw_bluetooth_sapphire/internal/host/common/log.h"
#include "pw_bluetooth_sapphire/internal/host/hci-spec/defaults.h"
#include "pw_bluetooth_sapphire/internal/host/hci-spec/protocol.h"
#include "pw_bluetooth_sapphire/internal/host/hci/local_address_delegate.h"
#include "pw_bluetooth_sapphire/internal/host/hci/util.h"
#include "pw_bluetooth_sapphire/internal/host/transport/transport.h"

namespace bt::hci {

LowEnergyConnector::PendingRequest::PendingRequest(
    const DeviceAddress& peer_address, StatusCallback status_callback)
    : peer_address(peer_address), status_callback(std::move(status_callback)) {}

LowEnergyConnector::LowEnergyConnector(
    Transport::WeakPtr hci,
    LocalAddressDelegate* local_addr_delegate,
    pw::async::Dispatcher& dispatcher,
    IncomingConnectionDelegate delegate)
    : pw_dispatcher_(dispatcher),
      hci_(std::move(hci)),
      local_addr_delegate_(local_addr_delegate),
      delegate_(std::move(delegate)),
      weak_self_(this) {
  BT_DEBUG_ASSERT(hci_.is_alive());
  BT_DEBUG_ASSERT(local_addr_delegate_);
  BT_DEBUG_ASSERT(delegate_);

  auto self = weak_self_.GetWeakPtr();
  event_handler_id_ = hci_->command_channel()->AddLEMetaEventHandler(
      hci_spec::kLEConnectionCompleteSubeventCode,
      [self](const EmbossEventPacket& event) {
        if (self.is_alive()) {
          return self->OnConnectionCompleteEvent(event);
        }
        return CommandChannel::EventCallbackResult::kRemove;
      });

  request_timeout_task_.set_function(
      [this](pw::async::Context& /*ctx*/, pw::Status status) {
        if (status.ok()) {
          OnCreateConnectionTimeout();
        }
      });
}

LowEnergyConnector::~LowEnergyConnector() {
  if (hci_.is_alive() && hci_->command_channel()) {
    hci_->command_channel()->RemoveEventHandler(event_handler_id_);
  }
  if (request_pending())
    Cancel();
}

bool LowEnergyConnector::CreateConnection(
    bool use_accept_list,
    const DeviceAddress& peer_address,
    uint16_t scan_interval,
    uint16_t scan_window,
    const hci_spec::LEPreferredConnectionParameters& initial_parameters,
    StatusCallback status_callback,
    pw::chrono::SystemClock::duration timeout) {
  BT_DEBUG_ASSERT(status_callback);
  BT_DEBUG_ASSERT(timeout.count() > 0);

  if (request_pending())
    return false;

  BT_DEBUG_ASSERT(!request_timeout_task_.is_pending());
  pending_request_ = PendingRequest(peer_address, std::move(status_callback));

  local_addr_delegate_->EnsureLocalAddress(
      [this,
       use_accept_list,
       peer_address,
       scan_interval,
       scan_window,
       initial_parameters,
       callback = std::move(status_callback),
       timeout](const auto& address) mutable {
        // Use the identity address if privacy override was enabled.
        CreateConnectionInternal(use_local_identity_address_
                                     ? local_addr_delegate_->identity_address()
                                     : address,
                                 use_accept_list,
                                 peer_address,
                                 scan_interval,
                                 scan_window,
                                 initial_parameters,
                                 std::move(callback),
                                 timeout);
      });

  return true;
}

void LowEnergyConnector::CreateConnectionInternal(
    const DeviceAddress& local_address,
    bool use_accept_list,
    const DeviceAddress& peer_address,
    uint16_t scan_interval,
    uint16_t scan_window,
    const hci_spec::LEPreferredConnectionParameters& initial_parameters,
    StatusCallback status_callback,
    pw::chrono::SystemClock::duration timeout) {
  if (!hci_.is_alive()) {
    return;
  }
  // Check if the connection request was canceled via Cancel().
  if (!pending_request_ || pending_request_->canceled) {
    bt_log(DEBUG,
           "hci-le",
           "connection request was canceled while obtaining local address");
    pending_request_.reset();
    return;
  }

  BT_DEBUG_ASSERT(!pending_request_->initiating);

  pending_request_->initiating = true;
  pending_request_->local_address = local_address;

  auto request = EmbossCommandPacket::New<
      pw::bluetooth::emboss::LECreateConnectionCommandWriter>(
      hci_spec::kLECreateConnection);
  auto params = request.view_t();
  params.le_scan_interval().Write(scan_interval);
  params.le_scan_window().Write(scan_window);
  params.initiator_filter_policy().Write(
      use_accept_list ? pw::bluetooth::emboss::GenericEnableParam::ENABLE
                      : pw::bluetooth::emboss::GenericEnableParam::DISABLE);

  // TODO(armansito): Use the resolved address types for <5.0 LE Privacy.
  params.peer_address_type().Write(
      peer_address.IsPublic() ? pw::bluetooth::emboss::LEAddressType::PUBLIC
                              : pw::bluetooth::emboss::LEAddressType::RANDOM);
  params.peer_address().CopyFrom(peer_address.value().view());

  params.own_address_type().Write(
      local_address.IsPublic()
          ? pw::bluetooth::emboss::LEOwnAddressType::PUBLIC
          : pw::bluetooth::emboss::LEOwnAddressType::RANDOM);

  params.connection_interval_min().Write(initial_parameters.min_interval());
  params.connection_interval_max().Write(initial_parameters.max_interval());
  params.max_latency().Write(initial_parameters.max_latency());
  params.supervision_timeout().Write(initial_parameters.supervision_timeout());
  params.min_connection_event_length().Write(0x0000);
  params.max_connection_event_length().Write(0x0000);

  // HCI Command Status Event will be sent as our completion callback.
  auto self = weak_self_.GetWeakPtr();
  auto complete_cb = [self, timeout](auto id, const EventPacket& event) {
    BT_DEBUG_ASSERT(event.event_code() == hci_spec::kCommandStatusEventCode);

    if (!self.is_alive())
      return;

    Result<> result = event.ToResult();
    if (result.is_error()) {
      self->OnCreateConnectionComplete(result, nullptr);
      return;
    }

    // The request was started but has not completed; initiate the command
    // timeout period. NOTE: The request will complete when the controller
    // asynchronously notifies us of with a LE Connection Complete event.
    self->request_timeout_task_.Cancel();
    self->request_timeout_task_.PostAfter(timeout);
  };

  hci_->command_channel()->SendCommand(
      std::move(request), complete_cb, hci_spec::kCommandStatusEventCode);
}

void LowEnergyConnector::Cancel() { CancelInternal(false); }

void LowEnergyConnector::CancelInternal(bool timed_out) {
  BT_DEBUG_ASSERT(request_pending());

  if (pending_request_->canceled) {
    bt_log(WARN, "hci-le", "connection attempt already canceled!");
    return;
  }

  // At this point we do not know whether the pending connection request has
  // completed or not (it may have completed in the controller but that does not
  // mean that we have processed the corresponding LE Connection Complete
  // event). Below we mark the request as canceled and tell the controller to
  // cancel its pending connection attempt.
  pending_request_->canceled = true;
  pending_request_->timed_out = timed_out;

  request_timeout_task_.Cancel();

  // Tell the controller to cancel the connection initiation attempt if a
  // request is outstanding. Otherwise there is no need to talk to the
  // controller.
  if (pending_request_->initiating && hci_.is_alive()) {
    bt_log(
        DEBUG, "hci-le", "telling controller to cancel LE connection attempt");
    auto complete_cb = [](auto id, const EventPacket& event) {
      hci_is_error(
          event, WARN, "hci-le", "failed to cancel connection request");
    };
    auto cancel = EmbossCommandPacket::New<
        pw::bluetooth::emboss::LECreateConnectionCancelCommandView>(
        hci_spec::kLECreateConnectionCancel);
    hci_->command_channel()->SendCommand(std::move(cancel), complete_cb);

    // A connection complete event will be generated by the controller after
    // processing the cancel command.
    return;
  }

  bt_log(DEBUG, "hci-le", "connection initiation aborted");
  OnCreateConnectionComplete(ToResult(HostError::kCanceled), nullptr);
}

CommandChannel::EventCallbackResult
LowEnergyConnector::OnConnectionCompleteEvent(const EmbossEventPacket& event) {
  BT_DEBUG_ASSERT(event.event_code() == hci_spec::kLEMetaEventCode);
  BT_DEBUG_ASSERT(event.view<pw::bluetooth::emboss::LEMetaEventView>()
                      .subevent_code()
                      .Read() == hci_spec::kLEConnectionCompleteSubeventCode);

  auto params =
      event.view<pw::bluetooth::emboss::LEConnectionCompleteSubeventView>();

  // First check if this event is related to the currently pending request.
  const bool matches_pending_request =
      pending_request_ && (pending_request_->peer_address.value() ==
                           DeviceAddressBytes{params.peer_address()});

  if (Result<> result = event.ToResult(); result.is_error()) {
    if (matches_pending_request) {
      // The "Unknown Connect Identifier" error code is returned if this event
      // was sent due to a successful cancelation via the
      // HCI_LE_Create_Connection_Cancel command (sent by Cancel()).
      if (pending_request_->timed_out) {
        result = ToResult(HostError::kTimedOut);
      } else if (params.status().Read() ==
                 pw::bluetooth::emboss::StatusCode::UNKNOWN_CONNECTION_ID) {
        result = ToResult(HostError::kCanceled);
      }
      OnCreateConnectionComplete(result, nullptr);
    } else {
      bt_log(WARN,
             "hci-le",
             "unexpected connection complete event with error received: %s",
             bt_str(result));
    }
    return CommandChannel::EventCallbackResult::kContinue;
  }

  hci_spec::ConnectionHandle handle = params.connection_handle().Read();
  DeviceAddress peer_address(
      DeviceAddress::LePeerAddrToDeviceAddr(params.peer_address_type().Read()),
      DeviceAddressBytes(params.peer_address()));
  hci_spec::LEConnectionParameters connection_params(
      params.connection_interval().UncheckedRead(),
      params.peripheral_latency().UncheckedRead(),
      params.supervision_timeout().UncheckedRead());

  // If the connection did not match a pending request then we pass the
  // information down to the incoming connection delegate.
  if (!matches_pending_request) {
    delegate_(handle, params.role().Read(), peer_address, connection_params);
    return CommandChannel::EventCallbackResult::kContinue;
  }

  // A new link layer connection was created. Create an object to track this
  // connection. Destroying this object will disconnect the link.
  auto connection =
      std::make_unique<LowEnergyConnection>(handle,
                                            pending_request_->local_address,
                                            peer_address,
                                            connection_params,
                                            params.role().Read(),
                                            hci_);

  Result<> result = fit::ok();
  if (pending_request_->timed_out) {
    result = ToResult(HostError::kTimedOut);
  } else if (pending_request_->canceled) {
    result = ToResult(HostError::kCanceled);
  }

  // If we were requested to cancel the connection after the logical link
  // is created we disconnect it.
  if (result.is_error()) {
    connection = nullptr;
  }

  OnCreateConnectionComplete(result, std::move(connection));
  return CommandChannel::EventCallbackResult::kContinue;
}

void LowEnergyConnector::OnCreateConnectionComplete(
    Result<> result, std::unique_ptr<LowEnergyConnection> link) {
  BT_DEBUG_ASSERT(pending_request_);

  bt_log(DEBUG, "hci-le", "connection complete - status: %s", bt_str(result));

  request_timeout_task_.Cancel();

  auto status_cb = std::move(pending_request_->status_callback);
  pending_request_.reset();

  status_cb(result, std::move(link));
}

void LowEnergyConnector::OnCreateConnectionTimeout() {
  BT_DEBUG_ASSERT(pending_request_);
  bt_log(INFO, "hci-le", "create connection timed out: canceling request");

  // TODO(armansito): This should cancel the connection attempt only if the
  // connection attempt isn't using the filter accept list.
  CancelInternal(true);
}

}  // namespace bt::hci