sshd hanging after multiple successive logons

[Roumen Petrov]

What is value of MaxStartups in sshd_config ?

douglas.manton at uk.ibm.com wrote:

> 
> 
> Folks,
> 
> I use OpenSSH to poll a number of remote servers once every five minutes
> and obtain a number of attributes.  This is done using ssh as "sexec":
> 
>         ssh stats at remotehost getstats
> 
> This returns the output of the getstats program which is parsed, etc...
> 
> The problem is that after so many connections, the parent sshd hangs and
> does not accept any more connections.  I have reproduced the problem using
> a simple shell script on my local machine:
> 
>         while sleep 1
>         do
>                 ssh me at localhost whoami
>         done
> 
> This iterates about 4000 times before sshd hangs.  I can see that sshd is
> waiting in _pthread_waitlock when it has hung.  It actually decreases the
> CPU time when in this state.  I can conenct to the daemon on port 22 but
> it does not present the version string.
> 
> I realise that 4000 connections is not bad, but at five minute intervals
> over 100 machines this is happening every couple of days.
> 
> I am running OpenSSH 2.3.0p1 under AIX 4.3.3.0-ML6, compiled with IBM VAC
> v5.
> 
> Any ideas?  Has this been seen.  I can reproduce it every time.  When I
> get a chance I will test the build on my Ultra 10.
> 
> Many thanks,
> --------------------------------------------------------
>  Doug Manton, AT&T EMEA Firewall and Security Solutions
> 
>                    demanton at att.com
> --------------------------------------------------------
> "If privacy is outlawed, only outlaws will have privacy"