[OpenAFS] Misconfigured Windows client hangs Linux server

[Rainer Toebbicke]

Jeffrey Altman wrote:
> I don't see how that could hang the server running on linux.
> A failure to support digital signatures will prevent the
> Windows AFS Client service from being able to process the
> requests and send a response that the Windows CIFS client
> will respond to.
> 

Having a fileserver dump with a similar case on my desk I can confirm 
that a windows client can indeed "hang" an AFS server (although I don't 
know if that had anything to do with digital signatures).

The scenario: all threads blocked in h_Lock_r on the same host, 
triggered by a SRXAFS_GetTime call. Except the one holding the lock who 
is waiting for RXAFSCB_WhoAreYou (to that host). Sure, it will 
eventually time out if there is no response but if the GetTime RPCs are 
sufficiently frequent this will do the job.

Shows that we still need some hardening effort in the fileserver, 
perhaps a quota of simultaneous calls/host or similar, with a VBUSY 
return whenever that quota is exceeded. We already do this automatically 
when a particular volume has more users than 1/2 the threads and there 
are calls waiting - happens frequently with a farm behind.

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Rainer Toebbicke
European Laboratory for Particle Physics(CERN) - Geneva, Switzerland
Phone: +41 22 767 8985       Fax: +41 22 767 7155