classic_connection_base.h

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/*
  Copyright (c) 2020, 2025, Oracle and/or its affiliates.
 
  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License, version 2.0,
  as published by the Free Software Foundation.
 
  This program is designed to work with certain software (including
  but not limited to OpenSSL) that is licensed under separate terms,
  as designated in a particular file or component or in included license
  documentation.  The authors of MySQL hereby grant you an additional
  permission to link the program and your derivative works with the
  separately licensed software that they have either included with
  the program or referenced in the documentation.
 
  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.
 
  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/
 
#ifndef ROUTING_CLASSIC_CONNECTION_BASE_INCLUDED
#define ROUTING_CLASSIC_CONNECTION_BASE_INCLUDED
 
#include <chrono>
#include <functional>
#include <memory>
#include <optional>
#include <string>
#include <vector>
 
#include "basic_protocol_splicer.h"
#include "connection.h"  // MySQLRoutingConnectionBase
#include "mysql/harness/destination.h"
#include "mysql/harness/destination_endpoint.h"
#include "mysql/harness/net_ts/executor.h"
#include "mysql/harness/net_ts/timer.h"
#include "mysqlrouter/channel.h"
#include "mysqlrouter/classic_prepared_statement.h"
#include "mysqlrouter/classic_protocol_constants.h"
#include "mysqlrouter/classic_protocol_message.h"
#include "mysqlrouter/classic_protocol_session_track.h"
#include "mysqlrouter/classic_protocol_state.h"
#include "mysqlrouter/connection_pool.h"
#include "processor.h"
#include "sql_exec_context.h"
#include "trace_span.h"
#include "tracer.h"
#include "transport_constraints.h"
 
class MysqlRoutingClassicConnectionBase
    : public MySQLRoutingConnectionBase,
      public std::enable_shared_from_this<MysqlRoutingClassicConnectionBase> {
 protected:
  // constructor
  //
  // use ::create() instead.
  MysqlRoutingClassicConnectionBase(
      MySQLRoutingContext &context, DestinationManager *destination_manager,
      std::unique_ptr<ConnectionBase> client_connection,
      std::unique_ptr<RoutingConnectionBase> client_routing_connection,
      std::function<void(MySQLRoutingConnectionBase *)> remove_callback)
      : MySQLRoutingConnectionBase{context, std::move(remove_callback)},
        client_conn_{std::move(client_connection),
                     std::move(client_routing_connection),
                     context.source_ssl_mode(),
                     ClientSideConnection::protocol_state_type{}},
        server_conn_{nullptr, context.dest_ssl_mode(),
                     ServerSideConnection::protocol_state_type{}},
        read_timer_{client_conn_.connection()->io_ctx()},
        connect_timer_{client_conn_.connection()->io_ctx()},
        wait_for_my_writes_{context.wait_for_my_writes()},
        wait_for_my_writes_timeout_{context.wait_for_my_writes_timeout()},
        destination_manager_{destination_manager} {
    client_address(client_conn_.connection()->endpoint());
  }
 
 public:
  using ClientSideConnection =
      TlsSwitchableClientConnection<ClientSideClassicProtocolState>;
  using ServerSideConnection =
      TlsSwitchableConnection<ServerSideClassicProtocolState>;
 
  // create a new shared_ptr<ThisClass>
  //
  template <typename... Args>
  [[nodiscard]] static std::shared_ptr<MysqlRoutingClassicConnectionBase>
  create(Args &&...args) {
    // can't use make_unique<> here as the constructor is private.
    return std::shared_ptr<MysqlRoutingClassicConnectionBase>(
        new MysqlRoutingClassicConnectionBase(std::forward<Args>(args)...));
  }
 
  // get a shared-ptr that refers the same 'this'
  std::shared_ptr<MysqlRoutingClassicConnectionBase> getptr() {
    return shared_from_this();
  }
 
  static stdx::expected<size_t, std::error_code> encode_error_packet(
      std::vector<uint8_t> &error_frame, const uint8_t seq_id,
      const classic_protocol::capabilities::value_type caps,
      const uint16_t error_code, const std::string &msg,
      const std::string &sql_state);
 
  void on_handshake_received();
  void on_handshake_aborted();
 
  SslMode source_ssl_mode() const { return client_conn_.ssl_mode(); }
 
  SslMode dest_ssl_mode() const { return server_conn_.ssl_mode(); }
 
  net::impl::socket::native_handle_type get_client_fd() const override {
    return client_conn().native_handle();
  }
 
  DestinationManager *destination_manager() const {
    return destination_manager_;
  }
 
  routing_guidelines::Session_info get_session_info();
 
  void disconnect() override;
 
  virtual void async_run() {}
 
  void send_server_failed(std::error_code ec, bool call_finish = true);
 
  void recv_server_failed(std::error_code ec, bool call_finish = true);
 
  void send_client_failed(std::error_code ec, bool call_finish = true);
 
  void recv_client_failed(std::error_code ec, bool call_finish = true);
 
  void server_socket_failed(std::error_code ec, bool call_finish = true);
 
  virtual void client_socket_failed(std::error_code ec,
                                    bool call_finish = true);
 
  // resume
  //
  // A Processor may suspend by returning Result::Suspend. When woken,
  // typically using an async timer, the Processor calls resume() to execute
  // the next loop() iteration. This allows waiting asynchronously for a
  // condition other than async io.
  void resume() { call_next_function(Function::kLoop); }
 
 protected:
  enum class Function {
    kLoop,
 
    kFinish,
  };
 
  void call_next_function(Function next) {
    switch (next) {
      case Function::kFinish:
        return finish();
 
      case Function::kLoop:
        return loop();
    }
  }
 
 private:
  // a stack of processors
  //
  // take the last processor until its done.
  //
  // Flow -> Greeting | Command
  //   Greeting -> Connect -> Server::Greeting
  //     Server::Greeting -> Server::Greeting::Greeting |
  //     Server::Greeting::Error Server::Greeting::Error -> Error::Fatal
  //     Server::Greeting::Greeting -> Client::Greeting
  //     Client::Greeting -> TlsConnect | Server::Greeting::Response
  //     TlsConnect -> Client::Greeting::Full | Error::Fatal
  //     Client::Greeting::Full -> Server::Ok | Auth::Switch | Server::Error
  //     Auth::Switch -> ...
  //       Auth
  //     Server::Ok -> Command
  //   Command ->
  //
  std::vector<std::unique_ptr<BasicProcessor>> processors_;
 
 public:
  void push_processor(std::unique_ptr<BasicProcessor> processor) {
    return processors_.push_back(std::move(processor));
  }
 
  void pop_processor() { processors_.pop_back(); }
 
  stdx::expected<void, std::error_code> track_session_changes(
      net::const_buffer session_trackers,
      classic_protocol::capabilities::value_type caps,
      bool ignore_some_state_changed = false);
 
  /**
   * reset the connection's settings to the initial-values.
   */
  void reset_to_initial();
 
 private:
  void trace_and_call_function(Tracer::Event::Direction dir,
                               std::string_view stage, Function func);
 
  void async_send_client(Function next);
 
  void async_recv_client(Function next);
 
  void async_send_server(Function next);
 
  void async_recv_server(Function next);
 
  void async_recv_both(Function next);
 
  void async_send_client_and_finish();
 
  void async_wait_client_closed();
 
  void async_wait_send_server(Function next);
 
 private:
  // the client didn't send a Greeting before closing the connection.
  //
  // Generate a Greeting to be sent to the server, to ensure the router's IP
  // isn't blocked due to the server's max_connect_errors.
  void server_side_client_greeting();
 
  // main processing loop
  void loop();
 
  // after a QUIT, we should wait until the client closed the connection.
 
  // called when the connection should be closed.
  //
  // called multiple times (once per "active_work_").
  void finish();
 
  // final state.
  //
  // removes the connection from the connection-container.
  virtual void done();
 
 public:
  ClientSideConnection::protocol_state_type &client_protocol() {
    return client_conn().protocol();
  }
 
  const ClientSideConnection::protocol_state_type &client_protocol() const {
    return client_conn().protocol();
  }
 
  ServerSideConnection::protocol_state_type &server_protocol() {
    return server_conn().protocol();
  }
 
  const ServerSideConnection::protocol_state_type &server_protocol() const {
    return server_conn().protocol();
  }
 
  ClientSideConnection &client_conn() { return client_conn_; }
  const ClientSideConnection &client_conn() const { return client_conn_; }
 
  ServerSideConnection &server_conn() { return server_conn_; }
  const ServerSideConnection &server_conn() const { return server_conn_; }
 
  virtual void stash_server_conn();
 
  std::optional<mysql_harness::Destination> get_destination_id()
      const override {
    return expected_server_mode() == mysqlrouter::ServerMode::ReadOnly
               ? read_only_destination_id()
               : read_write_destination_id();
  }
 
  void destination_id(const std::optional<mysql_harness::Destination> &id) {
    expected_server_mode() == mysqlrouter::ServerMode::ReadOnly
        ? read_only_destination_id(id)
        : read_write_destination_id(id);
  }
 
  std::optional<mysql_harness::Destination> read_only_destination_id()
      const override {
    return ro_destination_id_;
  }
 
  void read_only_destination_id(
      const std::optional<mysql_harness::Destination> &destination_id) {
    ro_destination_id_ = destination_id;
  }
 
  std::optional<mysql_harness::Destination> read_write_destination_id()
      const override {
    return rw_destination_id_;
  }
  void read_write_destination_id(
      const std::optional<mysql_harness::Destination> &destination_id) {
    rw_destination_id_ = destination_id;
  }
 
  std::optional<mysql_harness::DestinationEndpoint> destination_endpoint()
      const override {
    return expected_server_mode() == mysqlrouter::ServerMode::ReadOnly
               ? read_only_destination_endpoint()
               : read_write_destination_endpoint();
  }
 
  void destination_endpoint(
      const std::optional<mysql_harness::DestinationEndpoint> &ep) {
    expected_server_mode() == mysqlrouter::ServerMode::ReadOnly
        ? read_only_destination_endpoint(ep)
        : read_write_destination_endpoint(ep);
  }
 
  std::optional<mysql_harness::DestinationEndpoint>
  read_only_destination_endpoint() const override {
    return ro_destination_endpoint_;
  }
  void read_only_destination_endpoint(
      const std::optional<mysql_harness::DestinationEndpoint> &ep) {
    ro_destination_endpoint_ = ep;
  }
 
  std::optional<mysql_harness::DestinationEndpoint>
  read_write_destination_endpoint() const override {
    return rw_destination_endpoint_;
  }
 
  void read_write_destination_endpoint(
      const std::optional<mysql_harness::DestinationEndpoint> &ep) {
    rw_destination_endpoint_ = ep;
  }
 
  void set_destination(std::unique_ptr<Destination> destination) {
    destination_ = std::move(destination);
  }
 
  /**
   * check if the connection is authenticated.
   *
   * 'true' after the initial handshake and change-user finished with "ok".
   * 'false' at connection start and after change-user is started.
   *
   * @retval true if the connection is authenticated.
   * @return false otherwise
   */
  bool authenticated() const { return authenticated_; }
  void authenticated(bool v) { authenticated_ = v; }
 
  /**
   * check if connection sharing is possible.
   *
   * - the configuration enabled it
   */
  bool connection_sharing_possible() const;
 
  /**
   * check if connection sharing is allowed.
   *
   * - connection sharing is possible.
   * - no active transaction
   * - no SET TRANSACTION
   */
  bool connection_sharing_allowed() const;
 
  /**
   * reset the connection-sharing state.
   *
   * - after COM_RESET_CONNECTION::ok
   * - after COM_CHANGE_USER::ok
   */
  void connection_sharing_allowed_reset();
 
  /**
   * @return a string representing the reason why sharing is blocked.
   */
  std::string connection_sharing_blocked_by() const;
 
 private:
  int active_work_{0};
 
  bool authenticated_{false};
 
 public:
  /**
   * if the router is sending the initial server-greeting.
   *
   * if true, the router sends the initial greeting to the client,
   * if false, the server is sending the initial greeting and router is forward
   * it.
   */
  bool greeting_from_router() const {
    return !((source_ssl_mode() == SslMode::kPassthrough) ||
             (source_ssl_mode() == SslMode::kPreferred &&
              dest_ssl_mode() == SslMode::kAsClient));
  }
 
  void expected_server_transport_constraints(TransportConstraints val) {
    expected_server_transport_constraints_ = val;
  }
 
  TransportConstraints expected_server_transport_constraints() const {
    return expected_server_transport_constraints_;
  }
 
  void some_state_changed(bool v) { some_state_changed_ = v; }
 
  void expected_server_mode(mysqlrouter::ServerMode v) {
    expected_server_mode_ = v;
  }
  mysqlrouter::ServerMode expected_server_mode() const {
    return expected_server_mode_;
  }
 
  void current_server_mode(mysqlrouter::ServerMode v) {
    current_server_mode_ = v;
  }
  mysqlrouter::ServerMode current_server_mode() const {
    return current_server_mode_;
  }
 
  void wait_for_my_writes(bool v) { wait_for_my_writes_ = v; }
  bool wait_for_my_writes() const { return wait_for_my_writes_; }
 
  void gtid_at_least_executed(const std::string &gtid) {
    gtid_at_least_executed_ = gtid;
  }
  std::string gtid_at_least_executed() const { return gtid_at_least_executed_; }
 
  std::chrono::seconds wait_for_my_writes_timeout() const {
    return wait_for_my_writes_timeout_;
  }
  void wait_for_my_writes_timeout(std::chrono::seconds timeout) {
    wait_for_my_writes_timeout_ = timeout;
  }
 
  void collation_connection_maybe_dirty(bool val) {
    collation_connection_maybe_dirty_ = val;
  }
 
  bool collation_connection_maybe_dirty() const {
    return collation_connection_maybe_dirty_;
  }
 
  std::optional<classic_protocol::session_track::TransactionCharacteristics>
  trx_characteristics() const {
    return trx_characteristics_;
  }
 
  void trx_characteristics(
      std::optional<classic_protocol::session_track::TransactionCharacteristics>
          trx_chars) {
    trx_characteristics_ = std::move(trx_chars);
  }
 
  std::optional<classic_protocol::session_track::TransactionState> trx_state()
      const {
    return trx_state_;
  }
 
  void wait_until_completed() override {
    is_completed_.wait([](auto ready) { return ready == true; });
  }
 
  void completed() override {
    is_completed_.serialize_with_cv([](auto &ready, auto &cv) {
      ready = true;
      cv.notify_all();
    });
  }
 
 private:
  ClientSideConnection client_conn_;
  ServerSideConnection server_conn_;
 
  std::optional<mysql_harness::Destination>
      rw_destination_id_;  // read-write destination-id
  std::optional<mysql_harness::Destination>
      ro_destination_id_;  // read-only destination-id
 
  std::optional<mysql_harness::DestinationEndpoint> rw_destination_endpoint_;
  std::optional<mysql_harness::DestinationEndpoint> ro_destination_endpoint_;
 
  /**
   * client side handshake isn't finished yet.
   */
  bool in_handshake_{true};
 
  std::optional<classic_protocol::session_track::TransactionState> trx_state_;
  std::optional<classic_protocol::session_track::TransactionCharacteristics>
      trx_characteristics_;
  bool some_state_changed_{false};
 
  bool collation_connection_maybe_dirty_{false};
 
  TransportConstraints expected_server_transport_constraints_{
      TransportConstraints::Constraint::kPlaintext};
 
 public:
  ExecutionContext &execution_context() { return exec_ctx_; }
  const ExecutionContext &execution_context() const { return exec_ctx_; }
 
 private:
  ExecutionContext exec_ctx_;
 
 public:
  void trace(Tracer::Event e) { tracer_.trace(e); }
 
  Tracer &tracer() { return tracer_; }
 
 private:
  Tracer tracer_{false};
 
  std::string get_routing_source() const override {
    return destination_->route_name();
  }
 
  void set_routing_source(std::string name) override {
    destination_->set_route_name(std::move(name));
  }
 
  routing_guidelines::Server_info get_server_info() const override {
    return destination_->get_server_info();
  }
 
 public:
  net::steady_timer &read_timer() { return read_timer_; }
  net::steady_timer &connect_timer() { return connect_timer_; }
 
  void connect_error_code(const std::error_code &ec) { connect_ec_ = ec; }
  std::error_code connect_error_code() const { return connect_ec_; }
 
  void diagnostic_area_changed(bool diagnostic_area_changed) {
    diagnostic_area_changed_ = diagnostic_area_changed;
  }
  bool diagnostic_area_changed() const { return diagnostic_area_changed_; }
 
  const TraceSpan &events() const { return events_; }
  TraceSpan &events() { return events_; }
 
  enum class FromEither {
    None,
    Started,
    RecvedFromClient,
    RecvedFromServer,
  };
 
  void recv_from_either(FromEither v) { recv_from_either_ = v; }
 
  FromEither recv_from_either() const { return recv_from_either_; }
 
  void has_transient_error_at_connect(bool val) {
    has_transient_error_at_connect_ = val;
  }
 
  bool has_transient_error_at_connect() const {
    return has_transient_error_at_connect_;
  }
 
 private:
  net::steady_timer read_timer_;
  net::steady_timer connect_timer_;
 
  std::error_code connect_ec_{};
 
  bool diagnostic_area_changed_{};
 
  std::unique_ptr<Destination> destination_;
 
  FromEither recv_from_either_{FromEither::None};
 
  // events for router.trace.
  TraceSpan events_;
 
  // where to target the server-connections if access_mode is kAuto
  //
  // - Unavailable -> any destination (at connect)
  // - ReadOnly    -> expect a destination in read-only mode
  //                  prefer read-only servers over read-write servers
  // - ReadWrite   -> expect a destination in read-write mode,
  //                  if none is available fail the statement/connection.
  //
  mysqlrouter::ServerMode expected_server_mode_{
      mysqlrouter::ServerMode::Unavailable};
 
  // server-mode of the server-connection.
  //
  // - Unavailable -> server mode is still unknown or ignored.
  // - ReadOnly    -> server is used as read-only. (MUST be read-only)
  // - ReadWrite   -> server is used as read-write.(MUST be read-write)
  //
  // used to pick a subset of the available destinations at connect time.
  mysqlrouter::ServerMode current_server_mode_{
      mysqlrouter::ServerMode::Unavailable};
 
  // wait for 'gtid_at_least_executed_' with switch to a read-only destination?
  bool wait_for_my_writes_;
 
  // GTID to wait for. May be overwritten by client with query attributes.
  std::string gtid_at_least_executed_;
 
  // timeout for read your own writes. Setable with query attributes.
  std::chrono::seconds wait_for_my_writes_timeout_;
 
  bool has_transient_error_at_connect_{false};
 
  WaitableMonitor<bool> is_completed_{false};
 
  DestinationManager *destination_manager_;
};
 
#endif