blob: dc0ee5e8cc59703dc57caf8ae9b71232ce2c32fe [file] [log] [blame]
* Copyright (c) 2021 The WebRTC project authors. All Rights Reserved.
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
#include <cstdint>
#include <memory>
#include <string>
#include <unordered_set>
#include <utility>
#include <vector>
#include "absl/strings/string_view.h"
#include "absl/types/optional.h"
#include "api/array_view.h"
#include "net/dcsctp/common/internal_types.h"
#include "net/dcsctp/packet/chunk/reconfig_chunk.h"
#include "net/dcsctp/packet/parameter/incoming_ssn_reset_request_parameter.h"
#include "net/dcsctp/packet/parameter/outgoing_ssn_reset_request_parameter.h"
#include "net/dcsctp/packet/parameter/reconfiguration_response_parameter.h"
#include "net/dcsctp/packet/sctp_packet.h"
#include "net/dcsctp/public/dcsctp_socket.h"
#include "net/dcsctp/rx/data_tracker.h"
#include "net/dcsctp/rx/reassembly_queue.h"
#include "net/dcsctp/socket/context.h"
#include "net/dcsctp/timer/timer.h"
#include "net/dcsctp/tx/retransmission_queue.h"
namespace dcsctp {
// StreamResetHandler handles sending outgoing stream reset requests (to close
// an SCTP stream, which translates to closing a data channel).
// It also handles incoming "outgoing stream reset requests", when the peer
// wants to close its data channel.
// Resetting streams is an asynchronous operation where the client will request
// a request a stream to be reset, but then it might not be performed exactly at
// this point. First, the sender might need to discard all messages that have
// been enqueued for this stream, or it may select to wait until all have been
// sent. At least, it must wait for the currently sending fragmented message to
// be fully sent, because a stream can't be reset while having received half a
// message. In the stream reset request, the "sender's last assigned TSN" is
// provided, which is simply the TSN for which the receiver should've received
// all messages before this value, before the stream can be reset. Since
// fragments can get lost or sent out-of-order, the receiver of a request may
// not have received all the data just yet, and then it will respond to the
// sender: "In progress". In other words, try again. The sender will then need
// to start a timer and try the very same request again (but with a new sequence
// number) until the receiver successfully performs the operation.
// All this can take some time, and may be driven by timers, so the client will
// ultimately be notified using callbacks.
// In this implementation, when a stream is reset, the queued but not-yet-sent
// messages will be discarded, but that may change in the future. RFC8831 allows
// both behaviors.
class StreamResetHandler {
StreamResetHandler(absl::string_view log_prefix,
Context* context,
TimerManager* timer_manager,
DataTracker* data_tracker,
ReassemblyQueue* reassembly_queue,
RetransmissionQueue* retransmission_queue)
: log_prefix_(std::string(log_prefix) + "reset: "),
[this]() { return OnReconfigTimerExpiry(); },
ReconfigRequestSN(*ctx_->peer_initial_tsn() - 1)) {}
// Initiates reset of the provided streams. While there can only be one
// ongoing stream reset request at any time, this method can be called at any
// time and also multiple times. It will enqueue requests that can't be
// directly fulfilled, and will asynchronously process them when any ongoing
// request has completed.
void ResetStreams(rtc::ArrayView<const StreamID> outgoing_streams);
// Creates a Reset Streams request that must be sent if returned. Will start
// the reconfig timer. Will return absl::nullopt if there is no need to
// create a request (no streams to reset) or if there already is an ongoing
// stream reset request that hasn't completed yet.
absl::optional<ReConfigChunk> MakeStreamResetRequest();
// Called when handling and incoming RE-CONFIG chunk.
void HandleReConfig(ReConfigChunk chunk);
// Represents a stream request operation. There can only be one ongoing at
// any time, and a sent request may either succeed, fail or result in the
// receiver signaling that it can't process it right now, and then it will be
// retried.
class CurrentRequest {
CurrentRequest(TSN sender_last_assigned_tsn, std::vector<StreamID> streams)
: req_seq_nbr_(absl::nullopt),
streams_(std::move(streams)) {}
// Returns the current request sequence number, if this request has been
// sent (check `has_been_sent` first). Will return 0 if the request is just
// prepared (or scheduled for retransmission) but not yet sent.
ReconfigRequestSN req_seq_nbr() const {
return req_seq_nbr_.value_or(ReconfigRequestSN(0));
// The sender's last assigned TSN, from the retransmission queue. The
// receiver uses this to know when all data up to this TSN has been
// received, to know when to safely reset the stream.
TSN sender_last_assigned_tsn() const { return sender_last_assigned_tsn_; }
// The streams that are to be reset.
const std::vector<StreamID>& streams() const { return streams_; }
// If this request has been sent yet. If not, then it's either because it
// has only been prepared and not yet sent, or because the received couldn't
// apply the request, and then the exact same request will be retried, but
// with a new sequence number.
bool has_been_sent() const { return req_seq_nbr_.has_value(); }
// If the receiver can't apply the request yet (and answered "In Progress"),
// this will be called to prepare the request to be retransmitted at a later
// time.
void PrepareRetransmission() { req_seq_nbr_ = absl::nullopt; }
// If the request hasn't been sent yet, this assigns it a request number.
void PrepareToSend(ReconfigRequestSN new_req_seq_nbr) {
req_seq_nbr_ = new_req_seq_nbr;
// If this is set, this request has been sent. If it's not set, the request
// has been prepared, but has not yet been sent. This is typically used when
// the peer responded "in progress" and the same request (but a different
// request number) must be sent again.
absl::optional<ReconfigRequestSN> req_seq_nbr_;
// The sender's (that's us) last assigned TSN, from the retransmission
// queue.
TSN sender_last_assigned_tsn_;
// The streams that are to be reset in this request.
const std::vector<StreamID> streams_;
// Called to validate an incoming RE-CONFIG chunk.
bool Validate(const ReConfigChunk& chunk);
// Processes a stream stream reconfiguration chunk and may either return
// absl::nullopt (on protocol errors), or a list of responses - either 0, 1
// or 2.
absl::optional<std::vector<ReconfigurationResponseParameter>> Process(
const ReConfigChunk& chunk);
// Creates the actual RE-CONFIG chunk. A request (which set `current_request`)
// must have been created prior.
ReConfigChunk MakeReconfigChunk();
// Called to validate the `req_seq_nbr`, that it's the next in sequence. If it
// fails to validate, and returns false, it will also add a response to
// `responses`.
bool ValidateReqSeqNbr(
ReconfigRequestSN req_seq_nbr,
std::vector<ReconfigurationResponseParameter>& responses);
// Called when this socket receives an outgoing stream reset request. It might
// either be performed straight away, or have to be deferred, and the result
// of that will be put in `responses`.
void HandleResetOutgoing(
const ParameterDescriptor& descriptor,
std::vector<ReconfigurationResponseParameter>& responses);
// Called when this socket receives an incoming stream reset request. This
// isn't really supported, but a successful response is put in `responses`.
void HandleResetIncoming(
const ParameterDescriptor& descriptor,
std::vector<ReconfigurationResponseParameter>& responses);
// Called when receiving a response to an outgoing stream reset request. It
// will either commit the stream resetting, if the operation was successful,
// or will schedule a retry if it was deferred. And if it failed, the
// operation will be rolled back.
void HandleResponse(const ParameterDescriptor& descriptor);
// Expiration handler for the Reconfig timer.
absl::optional<DurationMs> OnReconfigTimerExpiry();
const std::string log_prefix_;
Context* ctx_;
DataTracker* data_tracker_;
ReassemblyQueue* reassembly_queue_;
RetransmissionQueue* retransmission_queue_;
const std::unique_ptr<Timer> reconfig_timer_;
// Outgoing streams that have been requested to be reset, but hasn't yet
// been included in an outgoing request.
std::unordered_set<StreamID, StreamID::Hasher> streams_to_reset_;
// The next sequence number for outgoing stream requests.
ReconfigRequestSN next_outgoing_req_seq_nbr_;
// The current stream request operation.
absl::optional<CurrentRequest> current_request_;
// For incoming requests - last processed request sequence number.
ReconfigRequestSN last_processed_req_seq_nbr_;
} // namespace dcsctp