One of the DNS parsing probes for MySQL: DNS parsing does work

Machine A--192.168.103.94--Server

Machine B - -and 192.168.4.2--Client

Machine A =

Install Mysql-server, start; Use the root user login to see if DNS resolution is turned on, and execute the following command:

Mysql> Show variables like ' skip_name_resolve% '; +-------------------+-------+| variable_name | Value |+-------------------+-------+| Skip_name_resolve | OFF |+-------------------+-------+1 row in Set (0.00 sec)

Indicates that DNS resolution is enabled

Add in/etc/hosts:

192.168.4.2 Mysql_client_host

Add user testdns,host to 192.168.4.2 in MySQL

mysql> grant all privileges on  *.* to [email protected] ' 192.168.4.2 '  identified by  ';mysql>  ' Select user,host,password from user where user= ' Testdns ';  +---------+----------- --+-------------------------------------------+| user    | host         | password                                    |+---------+-------------+------------------------------------------ -+| testdns | 192.168.4.2 | *b66feb4cf5216d971c066eb920ec03b27a5a3f40 |+-------- -+-------------+-------------------------------------------+mysql> flush privileges; 

Machine B =

Prepare a set of JDBC test programs:

Db.driver=com.mysql.jdbc.driver

Db.url=jdbc:mysql://192.168.103.94:3306/test

Db.username=testdns

db.password=000

Execute the "SELECT 1" query statement: the query succeeded!

Machine a=> View the list of connection processes:

mysql> show processlist;+----+---------+------------------------+-------+---------+------+------- +------------------+| id | user    | host                    | db     | Command | Time | State | Info              |+----+---------+------------------------+-------+------ ---+------+-------+------------------+|  3 | root    | localhost               | mysql |  Query   |    0 | null  | show processlist  | |   4 | testdns | mysql_client_host:4192 | test  | sleep    |    2 |       | null              |+----+---------+------------------------+-------+------ ---+------+-------+------------------+

The host name shown here is Mysql_client_host, which indicates that DNS resolution is working

Continue to guess when the host of Testdns is set to mysql_client_host it is also possible to verify the following:

Test execution of the "SELECT 1" query statement on machine B: The query was successful!

A machine will comment out the 192.168.4.2 mysql_client_host in/etc/hosts, and the MySQL command line executes flush hosts, because MySQL caches DNS parsing records;

The B machine is tested again,

Java.sql.SQLException:null, message from server: "Host ' 192.168.4.2 ' isn't allowed to connect to this MySQL server"

At Com.mysql.jdbc.SQLError.createSQLException (sqlerror.java:996)

At Com.mysql.jdbc.SQLError.createSQLException (sqlerror.java:935)

At Com.mysql.jdbc.SQLError.createSQLException (sqlerror.java:924)

Section: The above test proves that the DNS parsing of MySQL is actually working

One of the DNS parsing probes for MySQL: DNS parsing does work