Tcp listen limit.

[Damien Miller]

Fabio Yasusi Yamamoto wrote:
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> Hi folks.
> 
> Please, someone confirm if i'm right. if i'm wrong, please forgive-me.
> 
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> I've developed a little tool to stress test tcp connections.( Sending
> syn and answer ack-syn ). that simuates a real tcp connection. (
> http://www.hostname.org/fake_connect  )
> 
> And i notice that severals programs have a little tcp ( listen
> backlog? ) limit.
> 
> One of these program was OpenSSH.  With this i can cause a temporary
> DoS on  SSHd preventing any user to log-on. ( sometimes the real
> connection is closed , somethimes it does't response  at all ( there
> is no SYN-ACK ).
> 
> My target plataform was LINUX and FreeBSD.
> 
> - -
> Here is my question:
> ~    It is possible in the configuration, to increase the connection
> limit / listen backlog?

See the MaxStartups config parameter and the SSH_LISTEN_BACKLOG limit
in ssh.h

-d