network-mysqld-proto.c

Mysql Proxy本身是个很好的mysql负载均衡工具,但是其本身有bug:当多个mysql 做slave的时候,如果一个slave死掉,会影响别的slave也死掉!这个文件修复了这个bug!

/* Copyright (C) 2007 MySQL AB

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 of the License.

   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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */ 

#include <string.h>
#include "network-mysqld-proto.h"

#include "sys-pedantic.h"

/** @file
 *
 * decoders and encoders for the MySQL packets
 *
 * - basic data-types
 *   - fixed length integers
 *   - variable length integers
 *   - variable length strings
 * - packet types
 *   - OK packets
 *   - EOF packets
 *   - ERR packets
 *
 */

/**
 * force a crash for gdb and valgrind to get a stacktrace
 */
#define CRASHME() do { char *_crashme = NULL; *_crashme = 0; } while(0);

/**
 * a handy marco for constant strings 
 */
#define C(x) x, sizeof(x) - 1

/** @defgroup proto MySQL Protocol
 * 
 * decoders and encoders for the MySQL packets as described in 
 * http://forge.mysql.com/wiki/MySQL_Internals_ClientServer_Protocol
 *
 * */
/*@{*/

/**
 * decode a length-encoded integer from a network packet
 *
 * _off is incremented on success 
 *
 * @param packet   the MySQL-packet to decode
 * @param _off     offset in into the packet 
 * @return the decoded number
 *
 */
guint64 network_mysqld_proto_get_lenenc_int(GString *packet, guint *_off) {
	guint off = *_off;
	guint64 ret = 0;
	unsigned char *bytestream = (unsigned char *)packet->str;

	g_assert(off < packet->len);
	
	if (bytestream[off] < 251) { /* */
		ret = bytestream[off];
	} else if (bytestream[off] == 251) { /* NULL in row-data */
		ret = bytestream[off];
	} else if (bytestream[off] == 252) { /* 2 byte length*/
		g_assert(off + 2 < packet->len);
		ret = (bytestream[off + 1] << 0) | 
			(bytestream[off + 2] << 8) ;
		off += 2;
	} else if (bytestream[off] == 253) { /* 3 byte */
		g_assert(off + 3 < packet->len);
		ret = (bytestream[off + 1]   <<  0) | 
			(bytestream[off + 2] <<  8) |
			(bytestream[off + 3] << 16);

		off += 3;
	} else if (bytestream[off] == 254) { /* 8 byte */
		g_assert(off + 8 < packet->len);
		ret = (bytestream[off + 5] << 0) |
			(bytestream[off + 6] << 8) |
			(bytestream[off + 7] << 16) |
			(bytestream[off + 8] << 24);
		ret <<= 32;

		ret |= (bytestream[off + 1] <<  0) | 
			(bytestream[off + 2] <<  8) |
			(bytestream[off + 3] << 16) |
			(bytestream[off + 4] << 24);
		

		off += 8;
	} else {
		g_error("%s.%d: bytestream[%d] is %d", 
			__FILE__, __LINE__,
			off, bytestream[off]);
	}
	off += 1;

	*_off = off;

	return ret;
}

/**
 * decode a OK packet from the network packet
 */
int network_mysqld_proto_get_ok_packet(GString *packet, guint64 *affected, guint64 *insert_id, int *server_status, int *warning_count, char **msg) {
	guint off = 0;
	guint64 dest;
	guint field_count;

	field_count = network_mysqld_proto_get_int8(packet, &off);
	g_assert(field_count == 0);

	dest = network_mysqld_proto_get_lenenc_int(packet, &off); if (affected) *affected = dest;
	dest = network_mysqld_proto_get_lenenc_int(packet, &off); if (insert_id) *insert_id = dest;

	dest = network_mysqld_proto_get_int16(packet, &off);      if (server_status) *server_status = dest;
	dest = network_mysqld_proto_get_int16(packet, &off);      if (warning_count) *warning_count = dest;

	if (msg) *msg = NULL;

	return 0;
}

int network_mysqld_proto_append_ok_packet(GString *packet, guint64 affected_rows, guint64 insert_id, guint16 server_status, guint16 warnings) {
	network_mysqld_proto_append_int8(packet, 0); /* no fields */
	network_mysqld_proto_append_lenenc_int(packet, affected_rows);
	network_mysqld_proto_append_lenenc_int(packet, insert_id);
	network_mysqld_proto_append_int16(packet, server_status); /* autocommit */
	network_mysqld_proto_append_int16(packet, warnings); /* no warnings */

	return 0;
}

/**
 * create a ERR packet
 *
 * @note the sqlstate has to match the SQL standard. If no matching SQL state is known, leave it at NULL
 *
 * @param packet      network packet
 * @param errmsg      the error message
 * @param errmsg_len  byte-len of the error-message
 * @param errorcode   mysql error-code we want to send
 * @param sqlstate    if none-NULL, 5-char SQL state to send, if NULL, default SQL state is used
 *
 * @return 0 on success
 */
int network_mysqld_proto_append_error_packet(GString *packet, const char *errmsg, gsize errmsg_len, guint errorcode, const gchar *sqlstate) {
	network_mysqld_proto_append_int8(packet, 0xff); /* ERR */
	network_mysqld_proto_append_int16(packet, errorcode); /* errorcode */
	g_string_append_c(packet, '#');
	if (!sqlstate) {
		g_string_append_len(packet, C("07000"));
	} else {
		g_string_append_len(packet, sqlstate, 5);
	}

	if (errmsg_len < 512) {
		g_string_append_len(packet, errmsg, errmsg_len);
	} else {
		/* truncate the err-msg */
		g_string_append_len(packet, errmsg, 512);
	}

	return 0;
}


/**
 * skip bytes in the network packet
 *
 * a assertion makes sure that we can't skip over the end of the packet 
 *
 * @param packet the MySQL network packet
 * @param _off   offset into the packet
 * @param size   bytes to skip
 *
 */
void network_mysqld_proto_skip(GString *packet, guint *_off, gsize size) {
	g_assert(*_off + size <= packet->len);
	
	*_off += size;
}

/**
 * get a fixed-length integer from the network packet 
 *
 * @param packet the MySQL network packet
 * @param _off   offset into the packet
 * @param size   byte-len of the integer to decode
 * @return a the decoded integer
 */
guint64 network_mysqld_proto_get_int_len(GString *packet, guint *_off, gsize size) {
	gsize i;
	int shift;
	guint64 r = 0;
	guint off = *_off;

	g_assert(*_off < packet->len);
	if (*_off + size > packet->len) {
		CRASHME();
	}
	g_assert(*_off + size <= packet->len);

	for (i = 0, shift = 0; i < size; i++, shift += 8) {
		r += (unsigned char)(packet->str[off + i]) << shift;
	}

	*_off += size;

	return r;
}

/**
 * get a 8-bit integer from the network packet
 *
 * @param packet the MySQL network packet
 * @param _off   offset into the packet
 * @return a the decoded integer
 * @see network_mysqld_proto_get_int_len()
 */
guint8 network_mysqld_proto_get_int8(GString *packet, guint *_off) {
	return network_mysqld_proto_get_int_len(packet, _off, 1);
}

/**
 * get a 16-bit integer from the network packet
 *
 * @param packet the MySQL network packet
 * @param _off   offset into the packet
 * @return a the decoded integer
 * @see network_mysqld_proto_get_int_len()
 */
guint16 network_mysqld_proto_get_int16(GString *packet, guint *_off) {
	return network_mysqld_proto_get_int_len(packet, _off, 2);
}

/**
 * get a 32-bit integer from the network packet
 *
 * @param packet the MySQL network packet
 * @param _off   offset into the packet
 * @return a the decoded integer
 * @see network_mysqld_proto_get_int_len()
 */
guint32 network_mysqld_proto_get_int32(GString *packet, guint *_off) {
	return network_mysqld_proto_get_int_len(packet, _off, 4);
}

/**
 * get a string from the network packet
 *
 * @param packet the MySQL network packet
 * @param _off   offset into the packet
 * @param len    length of the string
 * @return the string (allocated) or NULL of len is 0
 */
gchar *network_mysqld_proto_get_string_len(GString *packet, guint *_off, gsize len) {
	gchar *str;

	g_assert(*_off < packet->len);
	if (*_off + len > packet->len) {
		g_error("packet-offset out of range: %u + "F_SIZE_T" > "F_SIZE_T, *_off, len, packet->len);
	}

	str = len ? g_strndup(packet->str + *_off, len) : NULL; 

	*_off += len;

	return str;
}

/**
 * get a variable-length string from the network packet
 *
 * variable length strings are prefixed with variable-length integer defining the length of the string
 *
 * @param packet the MySQL network packet
 * @param _off   offset into the packet
 * @return the string
 * @see network_mysqld_proto_get_string_len(), network_mysqld_proto_get_lenenc_int()
 */
gchar *network_mysqld_proto_get_lenenc_string(GString *packet, guint *_off) {
	guint64 len;

	len = network_mysqld_proto_get_lenenc_int(packet, _off);
	
	g_assert(*_off < packet->len);
	g_assert(*_off + len <= packet->len);
	
	return network_mysqld_proto_get_string_len(packet, _off, len);
}

/**
 * get a NUL-terminated string from the network packet
 *
 * @param packet the MySQL network packet
 * @param _off   offset into the packet
 * @return       the string
 * @see network_mysqld_proto_get_string_len()
 */
gchar *network_mysqld_proto_get_string(GString *packet, guint *_off) {
	guint len;
	gchar *r = NULL;

	for (len = 0; *_off + len < packet->len && *(packet->str + *_off + len); len++);