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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// A server side dispatcher which dispatches a given client's data to their
// stream.
#include <cstddef>
#include <cstdint>
#include <list>
#include <memory>
#include <optional>
#include <string>
#include <vector>
#include "absl/container/flat_hash_map.h"
#include "absl/container/flat_hash_set.h"
#include "absl/strings/string_view.h"
#include "quiche/quic/core/connection_id_generator.h"
#include "quiche/quic/core/crypto/quic_compressed_certs_cache.h"
#include "quiche/quic/core/frames/quic_rst_stream_frame.h"
#include "quiche/quic/core/frames/quic_stop_sending_frame.h"
#include "quiche/quic/core/quic_alarm.h"
#include "quiche/quic/core/quic_alarm_factory.h"
#include "quiche/quic/core/quic_blocked_writer_interface.h"
#include "quiche/quic/core/quic_buffered_packet_store.h"
#include "quiche/quic/core/quic_connection.h"
#include "quiche/quic/core/quic_connection_id.h"
#include "quiche/quic/core/quic_crypto_server_stream_base.h"
#include "quiche/quic/core/quic_error_codes.h"
#include "quiche/quic/core/quic_packet_writer.h"
#include "quiche/quic/core/quic_packets.h"
#include "quiche/quic/core/quic_process_packet_interface.h"
#include "quiche/quic/core/quic_session.h"
#include "quiche/quic/core/quic_time_wait_list_manager.h"
#include "quiche/quic/core/quic_types.h"
#include "quiche/quic/core/quic_version_manager.h"
#include "quiche/quic/core/quic_versions.h"
#include "quiche/quic/platform/api/quic_export.h"
#include "quiche/quic/platform/api/quic_socket_address.h"
#include "quiche/common/platform/api/quiche_logging.h"
#include "quiche/common/quiche_callbacks.h"
#include "quiche/common/quiche_linked_hash_map.h"
namespace quic {
namespace test {
class QuicDispatcherPeer;
} // namespace test
class QuicConfig;
class QuicCryptoServerConfig;
class QUICHE_EXPORT QuicDispatcher
: public QuicTimeWaitListManager::Visitor,
public ProcessPacketInterface,
public QuicBufferedPacketStore::VisitorInterface {
// Ideally we'd have a linked_hash_set: the boolean is unused.
using WriteBlockedList =
quiche::QuicheLinkedHashMap<QuicBlockedWriterInterface*, bool>;
const QuicConfig* config, const QuicCryptoServerConfig* crypto_config,
QuicVersionManager* version_manager,
std::unique_ptr<QuicConnectionHelperInterface> helper,
std::unique_ptr<QuicCryptoServerStreamBase::Helper> session_helper,
std::unique_ptr<QuicAlarmFactory> alarm_factory,
uint8_t expected_server_connection_id_length,
ConnectionIdGeneratorInterface& connection_id_generator);
QuicDispatcher(const QuicDispatcher&) = delete;
QuicDispatcher& operator=(const QuicDispatcher&) = delete;
~QuicDispatcher() override;
// Takes ownership of |writer|.
void InitializeWithWriter(QuicPacketWriter* writer);
// Process the incoming packet by creating a new session, passing it to
// an existing session, or passing it to the time wait list.
void ProcessPacket(const QuicSocketAddress& self_address,
const QuicSocketAddress& peer_address,
const QuicReceivedPacket& packet) override;
// Called when the socket becomes writable to allow queued writes to happen.
virtual void OnCanWrite();
// Returns true if there's anything in the blocked writer list.
virtual bool HasPendingWrites() const;
// Sends ConnectionClose frames to all connected clients.
void Shutdown();
// QuicSession::Visitor interface implementation (via inheritance of
// QuicTimeWaitListManager::Visitor):
// Ensure that the closed connection is cleaned up asynchronously.
void OnConnectionClosed(QuicConnectionId server_connection_id,
QuicErrorCode error, const std::string& error_details,
ConnectionCloseSource source) override;
// QuicSession::Visitor interface implementation (via inheritance of
// QuicTimeWaitListManager::Visitor):
// Queues the blocked writer for later resumption.
void OnWriteBlocked(QuicBlockedWriterInterface* blocked_writer) override;
// QuicSession::Visitor interface implementation (via inheritance of
// QuicTimeWaitListManager::Visitor):
// Collects reset error code received on streams.
void OnRstStreamReceived(const QuicRstStreamFrame& frame) override;
// QuicSession::Visitor interface implementation (via inheritance of
// QuicTimeWaitListManager::Visitor):
// Collects reset error code received on streams.
void OnStopSendingReceived(const QuicStopSendingFrame& frame) override;
// QuicSession::Visitor interface implementation (via inheritance of
// QuicTimeWaitListManager::Visitor):
// Try to add the new connection ID to the session map. Returns true on
// success.
bool TryAddNewConnectionId(
const QuicConnectionId& server_connection_id,
const QuicConnectionId& new_connection_id) override;
// QuicSession::Visitor interface implementation (via inheritance of
// QuicTimeWaitListManager::Visitor):
// Remove the retired connection ID from the session map.
void OnConnectionIdRetired(
const QuicConnectionId& server_connection_id) override;
void OnServerPreferredAddressAvailable(
const QuicSocketAddress& /*server_preferred_address*/) override {
// QuicTimeWaitListManager::Visitor interface implementation
// Called whenever the time wait list manager adds a new connection to the
// time-wait list.
void OnConnectionAddedToTimeWaitList(
QuicConnectionId server_connection_id) override;
using ReferenceCountedSessionMap =
absl::flat_hash_map<QuicConnectionId, std::shared_ptr<QuicSession>,
size_t NumSessions() const;
// Deletes all sessions on the closed session list and clears the list.
virtual void DeleteSessions();
// Clear recent_stateless_reset_addresses_.
void ClearStatelessResetAddresses();
using ConnectionIdMap =
absl::flat_hash_map<QuicConnectionId, QuicConnectionId,
// QuicBufferedPacketStore::VisitorInterface implementation.
void OnExpiredPackets(QuicConnectionId server_connection_id,
early_arrived_packets) override;
// Create connections for previously buffered CHLOs as many as allowed.
virtual void ProcessBufferedChlos(size_t max_connections_to_create);
// Return true if there is CHLO buffered.
virtual bool HasChlosBuffered() const;
// Start accepting new ConnectionIds.
void StartAcceptingNewConnections();
// Stop accepting new ConnectionIds, either as a part of the lame
// duck process or because explicitly configured.
void StopAcceptingNewConnections();
// Apply an operation for each session.
void PerformActionOnActiveSessions(
quiche::UnretainedCallback<void(QuicSession*)> operation) const;
// Get a snapshot of all sessions.
std::vector<std::shared_ptr<QuicSession>> GetSessionsSnapshot() const;
bool accept_new_connections() const { return accept_new_connections_; }
uint64_t num_packets_received() const { return num_packets_received_; }
// Creates a QUIC session based on the given information.
// |alpn| is the selected ALPN from |parsed_chlo.alpns|.
virtual std::unique_ptr<QuicSession> CreateQuicSession(
QuicConnectionId server_connection_id,
const QuicSocketAddress& self_address,
const QuicSocketAddress& peer_address, absl::string_view alpn,
const ParsedQuicVersion& version, const ParsedClientHello& parsed_chlo,
ConnectionIdGeneratorInterface& connection_id_generator) = 0;
// Tries to validate and dispatch packet based on available information.
// Returns true if packet is dropped or successfully dispatched (e.g.,
// processed by existing session, processed by time wait list, etc.),
// otherwise, returns false and the packet needs further processing.
virtual bool MaybeDispatchPacket(const ReceivedPacketInfo& packet_info);
// Values to be returned by ValidityChecks() to indicate what should be done
// with a packet. Fates with greater values are considered to be higher
// priority. ValidityChecks should return fate based on the priority order
// (i.e., returns higher priority fate first)
enum QuicPacketFate {
// Process the packet normally, which is usually to establish a connection.
// Put the connection ID into time-wait state and send a public reset.
// Drop the packet.
// This method is called by ProcessHeader on packets not associated with a
// known connection ID. It applies validity checks and returns a
// QuicPacketFate to tell what should be done with the packet.
// TODO(fayang): Merge ValidityChecks into MaybeDispatchPacket.
virtual QuicPacketFate ValidityChecks(const ReceivedPacketInfo& packet_info);
// Extra validity checks after the full Client Hello is parsed, this allows
// subclasses to reject a connection based on sni or alpn.
// Only called if ValidityChecks returns kFateProcess.
virtual QuicPacketFate ValidityChecksOnFullChlo(
const ReceivedPacketInfo& /*packet_info*/,
const ParsedClientHello& /*parsed_chlo*/) const {
return kFateProcess;
// Create and return the time wait list manager for this dispatcher, which
// will be owned by the dispatcher as time_wait_list_manager_
virtual QuicTimeWaitListManager* CreateQuicTimeWaitListManager();
// Buffers packet until it can be delivered to a connection.
void BufferEarlyPacket(const ReceivedPacketInfo& packet_info);
// Called when |packet_info| is the last received packet of the client hello.
// |parsed_chlo| is the parsed version of the client hello. Creates a new
// connection and delivers any buffered packets for that connection id.
void ProcessChlo(ParsedClientHello parsed_chlo,
ReceivedPacketInfo* packet_info);
QuicTimeWaitListManager* time_wait_list_manager() {
return time_wait_list_manager_.get();
const ParsedQuicVersionVector& GetSupportedVersions();
const QuicConfig& config() const { return *config_; }
const QuicCryptoServerConfig* crypto_config() const { return crypto_config_; }
QuicCompressedCertsCache* compressed_certs_cache() {
return &compressed_certs_cache_;
QuicConnectionHelperInterface* helper() { return helper_.get(); }
QuicCryptoServerStreamBase::Helper* session_helper() {
return session_helper_.get();
const QuicCryptoServerStreamBase::Helper* session_helper() const {
return session_helper_.get();
QuicAlarmFactory* alarm_factory() { return alarm_factory_.get(); }
QuicPacketWriter* writer() { return writer_.get(); }
// Returns true if a session should be created for a connection with an
// unknown version.
virtual bool ShouldCreateSessionForUnknownVersion(
const ReceivedPacketInfo& packet_info);
void SetLastError(QuicErrorCode error);
// Called by MaybeDispatchPacket when current packet cannot be dispatched.
// Used by subclasses to conduct specific logic to dispatch packet. Returns
// true if packet is successfully dispatched.
virtual bool OnFailedToDispatchPacket(const ReceivedPacketInfo& packet_info);
bool HasBufferedPackets(QuicConnectionId server_connection_id);
// Called when BufferEarlyPacket() fail to buffer the packet.
virtual void OnBufferPacketFailure(
QuicBufferedPacketStore::EnqueuePacketResult result,
QuicConnectionId server_connection_id);
// Removes the session from the write blocked list, and adds the ConnectionId
// to the time-wait list. The caller needs to manually remove the session
// from the map after that.
void CleanUpSession(QuicConnectionId server_connection_id,
QuicConnection* connection, QuicErrorCode error,
const std::string& error_details,
ConnectionCloseSource source);
// Called to terminate a connection statelessly. Depending on |format|, either
// 1) send connection close with |error_code| and |error_details| and add
// connection to time wait list or 2) directly add connection to time wait
// list with |action|.
// |self_address| and |peer_address| are passed to
// |OnStatelessConnectionCloseSent| when a connection close is sent.
void StatelesslyTerminateConnection(
const QuicSocketAddress& self_address,
const QuicSocketAddress& peer_address,
QuicConnectionId server_connection_id, PacketHeaderFormat format,
bool version_flag, bool use_length_prefix, ParsedQuicVersion version,
QuicErrorCode error_code, const std::string& error_details,
QuicTimeWaitListManager::TimeWaitAction action);
// Save/Restore per packet context.
virtual std::unique_ptr<QuicPerPacketContext> GetPerPacketContext() const;
virtual void RestorePerPacketContext(
std::unique_ptr<QuicPerPacketContext> /*context*/) {}
// If true, our framer will change its expected connection ID length
// to the received destination connection ID length of all IETF long headers.
void SetShouldUpdateExpectedServerConnectionIdLength(
bool should_update_expected_server_connection_id_length) {
should_update_expected_server_connection_id_length_ =
// If true, the dispatcher will allow incoming initial packets that have
// destination connection IDs shorter than 64 bits.
void SetAllowShortInitialServerConnectionIds(
bool allow_short_initial_server_connection_ids) {
allow_short_initial_server_connection_ids_ =
// Called if a packet from an unseen connection is reset or rejected.
virtual void OnNewConnectionRejected() {}
// Called by |StatelesslyTerminateConnection| when a connection close packet
// is generated.
virtual void OnStatelessConnectionCloseGenerated(
const QuicSocketAddress& /*self_address*/,
const QuicSocketAddress& /*peer_address*/,
QuicConnectionId /*connection_id*/, ParsedQuicVersion /*version*/,
QuicErrorCode /*error_code*/, const std::string& /*error_details*/) {}
// Selects the preferred ALPN from a vector of ALPNs.
// This runs through the list of ALPNs provided by the client and picks the
// first one it supports. If no supported versions are found, the first
// element of the vector is returned.
std::string SelectAlpn(const std::vector<std::string>& alpns);
// Sends public/stateless reset packets with no version and unknown
// connection ID according to the packet's size.
virtual void MaybeResetPacketsWithNoVersion(
const quic::ReceivedPacketInfo& packet_info);
// Called on packets with unsupported versions.
virtual void MaybeSendVersionNegotiationPacket(
const ReceivedPacketInfo& packet_info);
virtual ConnectionIdGeneratorInterface& ConnectionIdGenerator() {
return connection_id_generator_;
friend class test::QuicDispatcherPeer;
// TODO(fayang): Consider to rename this function to
// ProcessValidatedPacketWithUnknownConnectionId.
void ProcessHeader(ReceivedPacketInfo* packet_info);
struct ExtractChloResult {
// If set, a full client hello has been successfully parsed.
std::optional<ParsedClientHello> parsed_chlo;
// If set, the TLS alert that will cause a connection close.
// Always empty for Google QUIC.
std::optional<uint8_t> tls_alert;
// Try to extract information(sni, alpns, ...) if the full Client Hello has
// been parsed.
// Returns the parsed client hello in ExtractChloResult.parsed_chlo, if the
// full Client Hello has been successfully parsed.
// Returns the TLS alert in ExtractChloResult.tls_alert, if the extraction of
// Client Hello failed due to that alert.
// Otherwise returns a default-constructed ExtractChloResult and either buffer
// or (rarely) drop the packet.
ExtractChloResult TryExtractChloOrBufferEarlyPacket(
const ReceivedPacketInfo& packet_info);
// Deliver |packets| to |session| for further processing.
void DeliverPacketsToSession(
const std::list<QuicBufferedPacketStore::BufferedPacket>& packets,
QuicSession* session);
// Returns true if |version| is a supported protocol version.
bool IsSupportedVersion(const ParsedQuicVersion version);
// Returns true if a server connection ID length is below all the minima
// required by various parameters.
bool IsServerConnectionIdTooShort(QuicConnectionId connection_id) const;
// Core CHLO processing logic.
std::shared_ptr<QuicSession> CreateSessionFromChlo(
QuicConnectionId original_connection_id,
const ParsedClientHello& parsed_chlo, ParsedQuicVersion version,
QuicSocketAddress self_address, QuicSocketAddress peer_address,
ConnectionIdGeneratorInterface* connection_id_generator);
const QuicConfig* config_;
const QuicCryptoServerConfig* crypto_config_;
// The cache for most recently compressed certs.
QuicCompressedCertsCache compressed_certs_cache_;
// The list of connections waiting to write.
WriteBlockedList write_blocked_list_;
ReferenceCountedSessionMap reference_counted_session_map_;
// Entity that manages connection_ids in time wait state.
std::unique_ptr<QuicTimeWaitListManager> time_wait_list_manager_;
// The list of closed but not-yet-deleted sessions.
std::vector<std::shared_ptr<QuicSession>> closed_session_list_;
// The helper used for all connections.
std::unique_ptr<QuicConnectionHelperInterface> helper_;
// The helper used for all sessions.
std::unique_ptr<QuicCryptoServerStreamBase::Helper> session_helper_;
// Creates alarms.
std::unique_ptr<QuicAlarmFactory> alarm_factory_;
// An alarm which deletes closed sessions.
std::unique_ptr<QuicAlarm> delete_sessions_alarm_;
// The writer to write to the socket with.
std::unique_ptr<QuicPacketWriter> writer_;
// Packets which are buffered until a connection can be created to handle
// them.
QuicBufferedPacketStore buffered_packets_;
// Used to get the supported versions based on flag. Does not own.
QuicVersionManager* version_manager_;
// The last error set by SetLastError().
// TODO(fayang): consider removing last_error_.
QuicErrorCode last_error_;
// Number of unique session in session map.
size_t num_sessions_in_session_map_ = 0;
// Total number of packets received.
uint64_t num_packets_received_ = 0;
// A backward counter of how many new sessions can be create within current
// event loop. When reaches 0, it means can't create sessions for now.
int16_t new_sessions_allowed_per_event_loop_;
// True if this dispatcher is accepting new ConnectionIds (new client
// connections), false otherwise.
bool accept_new_connections_;
// If false, the dispatcher follows the IETF spec and rejects packets with
// invalid destination connection IDs lengths below 64 bits.
// If true they are allowed.
bool allow_short_initial_server_connection_ids_;
// IETF short headers contain a destination connection ID but do not
// encode its length. This variable contains the length we expect to read.
// This is also used to signal an error when a long header packet with
// different destination connection ID length is received when
// should_update_expected_server_connection_id_length_ is false and packet's
// version does not allow variable length connection ID.
uint8_t expected_server_connection_id_length_;
// Records client addresses that have been recently reset.
absl::flat_hash_set<QuicSocketAddress, QuicSocketAddressHash>
// An alarm which clear recent_stateless_reset_addresses_.
std::unique_ptr<QuicAlarm> clear_stateless_reset_addresses_alarm_;
// If true, change expected_server_connection_id_length_ to be the received
// destination connection ID length of all IETF long headers.
bool should_update_expected_server_connection_id_length_;
ConnectionIdGeneratorInterface& connection_id_generator_;
} // namespace quic