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From:Tuc at T-B-O-H Date:September 3 2005 11:08am
Subject:Re: Connections with bad DNS cause lockups
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> 
> Hello.
> 
> In my opinion, we're a little kinked in this issue. Let's start over.
>
	:( Sorry. I've been told by the GF that I have a habit of
doing it to her too. 
>
> In one of your posts you mentioned that the server runs lots
> of other services besides the database. 
>
	Yes, according to my runbook, the server :

	1) Is an NFS server to 4 other servers for web traffic
and logging. 
	2) Is the primary MX server for 7 domains (About 100
emails a day)
	3) Runs a Listproc for 4 mailing lists (About 5 messages
a day to 60 people)
	4) Runs MySQL (Approx 98 queries per hour)
	5) Runs Seti@Home (2 processes)
	6) Runs an IMAP Server for 1 user who logs on 5-10 
minutes a day

	The server pushes about 120kb/s a second 
according to MRTG for all that.
>
> Why do you think that
> the cause of the server's weird behavior is MySQL?
>
	Maybe I wasn't clear about it. The server is running
perfectly. I'm running SETI on it since its normally bored out
of its ever loving mind. When someone with a missing or bad
reverse DNS (PTR) record attempts to connect to the MySQL
server, any other connection via either the socket or the
TCP socket ends up blocking and waiting. Every other service
on the machine is fine, but MySQL becomes completely
unresponsive. When I said "DOS", I meant only against MySQL.
The rest of the machine is fine to process anything it wants.
>
> Is server still
> working, but you are unable to reach it through the network, or it
> is completely hung?
>
	No other services are affected, only attempts to connect
to MySQL via the socket or TCP. This makes what little access there
is to the database (A searchable orchid database) stop, and monitoring
detects it down and pages out. 


		Thanks, Tuc 
> 
> >> 
> >> 
> >        So if thats the way (FreeBSD ports), then besides the already suggested
> > changing to pure IP, is there any other ways to stop the DOS?
> > 
> >                Thanks, Tuc
> > 
> 
> 
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Thread
Connections with bad DNS cause lockupsTuc at T-B-O-H30 Aug
  • Re: Connections with bad DNS cause lockupsGleb Paharenko31 Aug
    • Re: Connections with bad DNS cause lockupsTuc at T-B-O-H1 Sep
      • Re: Connections with bad DNS cause lockupsSGreen1 Sep
        • Re: Connections with bad DNS cause lockupsTuc at T-B-O-H1 Sep
          • Re: Connections with bad DNS cause lockupsSGreen1 Sep
            • Re: Connections with bad DNS cause lockupsTuc at T-B-O-H1 Sep
      • Re: Connections with bad DNS cause lockupsGleb Paharenko2 Sep
        • Re: Connections with bad DNS cause lockupsTuc at T-B-O-H2 Sep
          • Re: Connections with bad DNS cause lockupsGleb Paharenko3 Sep
            • Re: Connections with bad DNS cause lockupsTuc at T-B-O-H3 Sep
              • Re: Connections with bad DNS cause lockupsGleb Paharenko3 Sep
                • Re: Connections with bad DNS cause lockupsTuc at T-B-O-H3 Sep
                  • Re: Connections with bad DNS cause lockupsGleb Paharenko5 Sep
                    • Re: Connections with bad DNS cause lockupsTuc at T-B-O-H5 Sep
                      • Re: Connections with bad DNS cause lockupsGleb Paharenko5 Sep
                        • Re: Connections with bad DNS cause lockupsTuc at T-B-O-H5 Sep
                    • Re: Connections with bad DNS cause lockupsTuc at T-B-O-H14 Sep