MySQL – Warning: IP Address Could Not Be Resolved

MySQL

I've got MySQL Master/Slave setup and I've noticed the following warnings in the mysql log files on both servers:

[Warning] IP address 'xxx.xxx.xxx.xxx' could not be resolved: Name or service not known

I've checked and the DNS lookups works fine and most of these IPs are from China.

I planning to limit access on port 3306 on the firewall however could you please help me to understand what they are trying to do. Are they just trying to connect to the MySQL server. Where I can look for some more details.

Thanks

Best Answer

When you create a MySQL user username@example.com MySQL has to do a reverse lookup on every IP address connecting to it to determine whether they are part of example.com.

Of course, there's no restriction on creating reverse lookups, so I can quite happily ask my provider to set the reverse lookup for my IP address to be google.com if I want... or example.com if I happen to know that's what the users in your database have. This won't let me in, as MySQL then does a forward lookup on the returned domain to make sure it matches the same IP address that's connecting.

You can switch this off with skip_name_resolve in your my.cnf. There are many good reasons for doing this.

The reason you are getting this error is that the IP address in question has no reverse lookup at all.

You also have malicious attackers from China trying to brute force their way into your database. That should be your top priority.

Related Solutions

Mysql replications: slave is not readonly

It is quite common to not have the slave in read_only mode..

in fact, if you do not set it yourself, then it never is enabled..

A good question, is why you would actually want to set it...???

Are you trying to protect mistakes? or errors made my admin users??? or the application?
Considering MANY admins are using MySQL as root anyways, where is the protection here??
You cant exactly protect your data as you would imagine ( as everything replicated into the slave anyway )

You do know that any user with super privileges and the replication thread do not abide by the read_only??

A strong structured approach to users and privileges is the correct way to deal with replication issues, not a read_only configuration on the slave

In my honest opinion, it actually does not protect very much...or useful for anything besides stopping a few users not write.. ( which on production systems - should never happen anyways )

As an example, In Mysql-Multi-Master ( read_only is set by the scripts ) This in theory is only to simply decide which server is the "True Master" in the master-master configuration..

All in all.. Forget about read_only ( its really unneccesary, and probably wont protect you from what you imagine it will )

Mysql – Setup a thesql replication, but new data are not updated

I think I see the problem

You have the following in your question:

Replicate_Do_DB: db1; db2

That is not supposed to be a semicolon-separated list. It is supposed to be a comma-separated list.

My guess is your have this in your slave's /etc/my.cnf

replicate-do-db=db1; db2

The correct way to set this up is

replicate-do-db=db1
replicate-do-db=db2

Please adjust this in the slave's /etc/my.cnf and restart mysql on the slave

Give it a Try !!!

UPDATE 2011-10-31 15:20 EDT

You may want to clear out the relay log by doing this

STOP SLAVE;
CHANGE MASTER TO master_log_file='mysql-bin.000008',master_log_pos-98;
START SLAVE;

then run SHOW SLAVE STATUS\G and make sure replication is running by making sure you see this

Slave_IO_Running: Yes
Slave_SQL_Running: Yes

just as you posted in your question

Best Answer

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Mysql replications: slave is not readonly

Mysql – Setup a thesql replication, but new data are not updated

UPDATE 2011-10-31 15:20 EDT

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