+-----------------------+-----------------------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-----------------------+-----------------------------------+------+-----+---------+-------+
| Host | char(60) | NO | PRI | | |
| User | char(16) | NO | PRI | | |
| Password | char(41) | NO | | | |
| Select_priv | enum('N','Y') | NO | | N | |
| Insert_priv | enum('N','Y') | NO | | N | |
| Update_priv | enum('N','Y') | NO | | N | |
| Delete_priv | enum('N','Y') | NO | | N | |
| Create_priv | enum('N','Y') | NO | | N | |
| Drop_priv | enum('N','Y') | NO | | N | |
| Reload_priv | enum('N','Y') | NO | | N | |
| Shutdown_priv | enum('N','Y') | NO | | N | |
| Process_priv | enum('N','Y') | NO | | N | |
| File_priv | enum('N','Y') | NO | | N | |
| Grant_priv | enum('N','Y') | NO | | N | |
| References_priv | enum('N','Y') | NO | | N | |
| Index_priv | enum('N','Y') | NO | | N | |
| Alter_priv | enum('N','Y') | NO | | N | |
| Show_db_priv | enum('N','Y') | NO | | N | |
| Super_priv | enum('N','Y') | NO | | N | |
| Create_tmp_table_priv | enum('N','Y') | NO | | N | |
| Lock_tables_priv | enum('N','Y') | NO | | N | |
| Execute_priv | enum('N','Y') | NO | | N | |
| Repl_slave_priv | enum('N','Y') | NO | | N | |
| Repl_client_priv | enum('N','Y') | NO | | N | |
| Create_view_priv | enum('N','Y') | NO | | N | |
| Show_view_priv | enum('N','Y') | NO | | N | |
| Create_routine_priv | enum('N','Y') | NO | | N | |
| Alter_routine_priv | enum('N','Y') | NO | | N | |
| Create_user_priv | enum('N','Y') | NO | | N | |
| Event_priv | enum('N','Y') | NO | | N | |
| Trigger_priv | enum('N','Y') | NO | | N | |
| ssl_type | enum('','ANY','X509','SPECIFIED') | NO | | | |
| ssl_cipher | blob | NO | | NULL | |
| x509_issuer | blob | NO | | NULL | |
| x509_subject | blob | NO | | NULL | |
| max_questions | int(11) unsigned | NO | | 0 | |
| max_updates | int(11) unsigned | NO | | 0 | |
| max_connections | int(11) unsigned | NO | | 0 | |
| max_user_connections | int(11) unsigned | NO | | 0 | |
+-----------------------+-----------------------------------+------+-----+---------+-------+
39 rows in set (0.01 sec)

mysql> select Host,User,Password from user;
+-----------+------+----------+
| Host | User | Password |
+-----------+------+----------+
| localhost | root | |
| 127.0.0.1 | root | |
| localhost | | |
+-----------+------+----------+
3 rows in set (0.00 sec)

static bool login_connection(THD *thd)
NET *net= &thd->net;
int error;
DBUG_ENTER("login_connection");
DBUG_PRINT("info", ("login_connection called by thread %lu",
thd->thread_id));
/* Use "connect_timeout" value during connection phase */
my_net_set_read_timeout(net, connect_timeout);
my_net_set_write_timeout(net, connect_timeout);
error= check_connection(thd); //此处是验证的具体函数
net_end_statement(thd);
if (error)
{ // Wrong permissions
#ifdef __NT__
if (vio_type(net->vio) == VIO_TYPE_NAMEDPIPE)
my_sleep(1000); /* must wait after eof() */
#endif
statistic_increment(aborted_connects,&LOCK_status);
DBUG_RETURN(1);
/* Connect completed, set read/write timeouts back to default */
my_net_set_read_timeout(net, thd->variables.net_read_timeout);
my_net_set_write_timeout(net, thd->variables.net_write_timeout);
DBUG_RETURN(0);

static int check_connection(THD *thd)
uint connect_errors= 0;
NET *net= &thd->net;
ulong pkt_len= 0;
char *end;
DBUG_PRINT("info",
("New connection received on %s", vio_description(net->vio)));
#ifdef SIGNAL_WITH_VIO_CLOSE
thd->set_active_vio(net->vio);
#endif
if (!thd->main_security_ctx.host) // If TCP/IP connection
char ip[30];
if (vio_peer_addr(net->vio, ip, &thd->peer_port))
my_error(ER_BAD_HOST_ERROR, MYF(0), thd->main_security_ctx.host_or_ip);
return 1;
if (!(thd->main_security_ctx.ip= my_strdup(ip,MYF(MY_WME))))
return 1; /* The error is set by my_strdup(). */
thd->main_security_ctx.host_or_ip= thd->main_security_ctx.ip;
vio_in_addr(net->vio,&thd->remote.sin_addr);
if (!(specialflag & SPECIAL_NO_RESOLVE))
vio_in_addr(net->vio,&thd->remote.sin_addr);
thd->main_security_ctx.host=
ip_to_hostname(&thd->remote.sin_addr, &connect_errors);
/* Cut very long hostnames to avoid possible overflows */
if (thd->main_security_ctx.host)
if (thd->main_security_ctx.host != my_localhost)
thd->main_security_ctx.host[min(strlen(thd->main_security_ctx.host),
HOSTNAME_LENGTH)]= 0;
thd->main_security_ctx.host_or_ip= thd->main_security_ctx.host;
if (connect_errors > max_connect_errors)
my_error(ER_HOST_IS_BLOCKED, MYF(0), thd->main_security_ctx.host_or_ip);
return 1;
...
if (acl_check_host(thd->main_security_ctx.host, thd->main_security_ctx.ip))//此处验证主机名或IP是否存在
my_error(ER_HOST_NOT_PRIVILEGED, MYF(0),
thd->main_security_ctx.host_or_ip);
return 1;
else /* Hostname given means that the connection was on a socket */
...
vio_keepalive(net->vio, TRUE);
...
char *user= end;
char *passwd= strend(user)+1;
uint user_len= passwd - user - 1;
char *db= passwd;
char db_buff[NAME_LEN + 1]; // buffer to store db in utf8
char user_buff[USERNAME_LENGTH + 1]; // buffer to store user in utf8
uint dummy_errors;
uint passwd_len= thd->client_capabilities & CLIENT_SECURE_CONNECTION ?
(uchar)(*passwd++) : strlen(passwd);
db= thd->client_capabilities & CLIENT_CONNECT_WITH_DB ?
db + passwd_len + 1 : 0;
uint db_len= db ? strlen(db) : 0;
if (passwd + passwd_len + db_len > (char *)net->read_pos + pkt_len)
inc_host_errors(&thd->remote.sin_addr);
my_error(ER_HANDSHAKE_ERROR, MYF(0), thd->main_security_ctx.host_or_ip);
return 1;
/* If username starts and ends in "'", chop them off */
if (user_len > 1 && user[0] == '\'' && user[user_len - 1] == '\'')
user[user_len-1]= 0;
user++;
user_len-= 2;
if (thd->main_security_ctx.user)
x_free(thd->main_security_ctx.user);
if (!(thd->main_security_ctx.user= my_strdup(user, MYF(MY_WME))))
return 1; /* The error is set by my_strdup(). */
return check_user(thd, COM_CONNECT, passwd, passwd_len, db, TRUE);//验证用户名和密码