[Samba] Can Constant Failed Connection Attempts Crash a Server?

Andy Liebman andyliebman at aol.com
Wed Nov 24 13:03:33 MST 2010

On 11/09/2010 04:43 AM, Volker Lendecke wrote:
> On Mon, Nov 08, 2010 at 09:23:06AM -0500, Andy Liebman wrote:
>> And now I have this case.
>> I would appreciate the opinion of the Samba.org folks.  Does it make
>> sense that constant bombardment of a Samba server with failed
>> connection attempts could cause the whole server to crash?
> No, definitely not. We could certainly talk about increasing
> the debug level of that message from 0 to 1, so that it does
> not appear in syslog.
> Volker

I have another case today of constant failed connection attempts 
crashing a Samba server.  It's the same thing as the previous time -- a 
workstation continually trying to access a share using a share name 
that's missing the last character. As it happens, without the last 
character, the share name being requested ends with an underscore 
character  ("_").  Don't know if that is relevant.

We are writing a simple Windows program to reproduce the failed 
connections and to see if we can bring down our own Samba servers.   :)

You suggested previously this might be a kernel bug, or that the failed 
attempts might be using up some scarce resource (memory? open files? 
what did you have in mind?) Assuming we can reproduce this issue, what 
do you suggest would be the best way to start debugging it?  I don't 
think running Samba with more logging or debugging is going to help.  
Suppose we can continually run vmstat and write the results to a log 
file.  Anything else you can think of?

FYI, I ran into another developer this week who had the same experience 
I had a few years back when the Google desktop indexer came out.  If 
Google indexer was trying to index a Samba share and it was logging in 
with the wrong credentials, it would try to log in thousands of times 
per minute and bring down the Samba servers after a short period of 
time.  Getting rid of the Google indexer made the crashes go away.


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