[OpenAFS] OpenAFS, Cisco VPN and MAC OS and mtu
Douglas E. Engert
Wed, 27 May 2009 15:05:24 -0500
For anyone interested, I sent in a patch today for this
[grand.central.org #124880] AutoReply: Add -rxmaxmtu parameter to afsd to help avoid VPN fragmentation of UDP packets
Kim Kimball wrote:
> Have you tried setting MTU on the fileserver command line instead?
> That's what we've done, for the same reason. It has worked, and we
> don't have to fiddle with each client. The negotiation between AFS
> client and fileserver for MTU size is "fileserver wins."
> Kim Kimball
> Douglas E. Engert wrote:
>> We are having problems with Mac OS 10.4 and 10.5 using Cisco VPN
>> AFS can become unusable. Mac 10.4 is running OpenAFS 1.4.8 for sure.
>> I think the Mac 10.5 is running OpenAFS 1.5.59.
>> Using rxdebug and looking at the natMTU parameter, on most Unix systems
>> this is 1444,(1500 - 56) as expected. On Windows systems this is usually
>> 1260. And on MAC it is 1444.
>> Even if I set the interface mtu 1244, and reboot the MAC, rxdebug shows
>> the interface is using 1244 but rxdebug continues to show a natMTU =
>> as though it still assumed the mtu was 1500.
>> So it looks like the MAC client is not getting the existingMTU
>> from the OS in util/netutils.c
>> The AFS client on Windows has the RxMaxMTU (1244 appears to be the best
>> setting). Is there any equivelent option for the MAC?
>> Any thoughts on this?
Douglas E. Engert <DEEngert@anl.gov>
Argonne National Laboratory
9700 South Cass Avenue
Argonne, Illinois 60439