MaxScale/include/maxscale/protocol.h

#pragma once
/*
 * Copyright (c) 2016 MariaDB Corporation Ab
 *
 * Use of this software is governed by the Business Source License included
 * in the LICENSE.TXT file and at www.mariadb.com/bsl11.
 *
 * Change Date: 2022-01-01
 *
 * On the date above, in accordance with the Business Source License, use
 * of this software will be governed by version 2 or later of the General
 * Public License.
 */

/**
 * @file protocol.h
 *
 * The protocol module interface definition.
 */

#include <maxscale/cdefs.h>
#include <maxscale/buffer.h>
#include <maxscale/jansson.h>

MXS_BEGIN_DECLS

struct dcb;
struct server;
struct session;

/**
 * Protocol module API
 */
typedef struct mxs_protocol
{
    /**
     * EPOLLIN handler, used to read available data from network socket
     *
     * @param dcb DCB to read from
     *
     * @return 1 on success, 0 on error
     */
    int32_t (*read)(struct dcb* dcb);

    /**
     * Write data to a network socket
     *
     * @param dcb    DCB to write to
     * @param buffer Buffer to write
     *
     * @return 1 on success, 0 on error
     */
    int32_t (*write)(struct dcb* dcb, GWBUF* buffer);

    /**
     * EPOLLOUT handler, used to write buffered data
     *
     * @param dcb DCB to write to
     *
     * @return 1 on success, 0 on error
     *
     * @note Currently the return value is ignored
     */
    int32_t (*write_ready)(struct dcb* dcb);

    /**
     * EPOLLERR handler
     *
     * @param dcb DCB for which the error occurred
     *
     * @return 1 on success, 0 on error
     *
     * @note Currently the return value is ignored
     */
    int32_t (*error)(struct dcb* dcb);

    /**
     * EPOLLHUP and EPOLLRDHUP handler
     *
     * @param dcb DCB for which the hangup occurred
     *
     * @return 1 on success, 0 on error
     *
     * @note Currently the return value is ignored
     */
    int32_t (*hangup)(struct dcb* dcb);

    /**
     * Accept a connection, only for client side protocol modules
     *
     * @param dcb The listener DCB
     *
     * @return 1 on success, 0 on error
     *
     * @note Currently the return value is ignored
     */
    int32_t (*accept)(struct dcb* dcb);

    /**
     * Connect to a server, only for backend side protocol modules
     *
     * @param dcb     DCB to connect
     * @param server  Server where the connection is made
     * @param session The session where the DCB should be linked to
     *
     * @return The opened file descriptor or DCBFD_CLOSED on error
     */
    int32_t (*connect)(struct dcb* dcb, struct server* server, struct session* session);

    /**
     * Free protocol data allocated in the connect handler
     *
     * @param dcb DCB to close
     *
     * @return 1 on success, 0 on error
     *
     * @note Currently the return value is ignored
     */
    int32_t (*close)(struct dcb* dcb);

    /**
     * Listen on a network socket, only for client side protocol modules
     *
     * @param dcb     DCB to listen with
     * @param address Address to listen on in `address|port` format
     *
     * @return 1 on success, 0 on error
     */
    int32_t (*listen)(struct dcb* dcb, char* address);

    /**
     * Perform user re-authentication
     *
     * @param dcb     DCB to re-authenticate
     * @param server  Server where the DCB is connected
     * @param session The session for the DCB
     * @param buffer  The buffer containing the original re-authentication request
     *
     * @return 1 on success, 0 on error
     *
     * @note Currently the return value is ignored
     */
    int32_t (*auth)(struct dcb* dcb, struct server* server, struct session* session, GWBUF* buffer);

    /**
     * Returns the name of the default authenticator module for this protocol
     *
     * @return The name of the default authenticator
     */
    char* (*auth_default)();

    /**
     * Handle connection limits
     *
     * @param dcb   DCB to handle
     * @param limit Maximum number of connections
     *
     * @return 1 on success, 0 on error
     *
     * @note Currently the return value is ignored
     */
    int32_t (*connlimit)(struct dcb* dcb, int limit);

    /**
     * Check if the connection has been fully established, used by connection pooling
     *
     * @param dcb DCB to check
     *
     * @return True if the connection is fully established and can be pooled
     */
    bool (*established)(struct dcb* );

    /**
     * Provide JSON formatted diagnostics about a DCB
     *
     * @param dcb DCB to diagnose
     *
     * @return JSON representation of the DCB
     */
    json_t* (*diagnostics_json)(struct dcb* dcb);

} MXS_PROTOCOL;

/**
 * The MXS_PROTOCOL version data. The following should be updated whenever
 * the MXS_PROTOCOL structure is changed. See the rules defined in modinfo.h
 * that define how these numbers should change.
 */
#define MXS_PROTOCOL_VERSION      {2, 0, 0}

/**
 * Specifies capabilities specific for protocol.
 *
 * @see enum routing_capability
 *
 * @note The values of the capabilities here *must* be between 0x010000000000
 *       and 0x800000000000, that is, bits 40 to 47.
 */
typedef enum protocol_capability
{
    PCAP_TYPE_NONE = 0x0 // TODO: remove once protocol capabilities are defined
} protocol_capability_t;

MXS_END_DECLS