Re: Question about SCP stalling over VPN

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The problem only happens with my wireless connection. (madwifi-ng on
the server side, kernel's b43 on the laptop.) With my wired ethernet
connection, the transfers all work. Sigh. I guess there is nothing more
this mailing list can do for me? :P.

(When wired, I'm sure it doesn't matter, but the rcvd adjust
messages steady out at 114688.)


On Tue, 23 Mar 2010 21:23:49 -0400, Dennis Nezic wrote:
> Err, with "-vvv" I get those exact same debug messages:
> 
> "debug2: channel 0: rcvd adjust 131072"
> 
> Lots of them. When trying to scp a 1G file to my server it
> consistently stalls around 10MB (give or take a few).
> 
> What does that debug message mean, and why is it stalling, and why did
> it work with my earlier kernel?
> 
> To be continued.
> 
> 
> On Mon, 22 Mar 2010 13:02:47 -0400, Dennis Nezic wrote:
> > I have run into a similar problem, although I don't get any "rcvd
> > adjust" debug messages -- instead my scp transfers stall -- at a
> > pretty predictable place too (not exactly, but to within a few
> > megabytes). My problem ONLY started after I upgraded my kernel (and
> > maybe some other things :s, from 2.6.19 to 2.6.33). My NFS transfers
> > also started "stalling", for many minutes (5-15min usually),
> > although they are retried, and eventually finish. Again, I don't
> > think ANY of these problems ever happened with my old kernel for a
> > couple years.
> > 
> > During the stalls, netstat says the tcp connection is still
> > ESTABLISHED, and when I Ctrl-C the stalled scp transfer, the sshd
> > server logs a "Received disconnect" message. No other debug messages
> > are shown for me. I'll try to get a tcpdump.
> > 
> > 
> > On Fri, 12 Mar 2010 09:13:47 -0500, Matthew Case wrote:
> > > First and foremost, thank you to everyone for your responses. I
> > > checked the MTU on both sides and it's currently 1500 so I'm
> > > assuming it's not a mismatch. My VPN is a pair of old Netscreen
> > > 5xp boxes, and I can't find anything relating to MTU or packet
> > > size in the configuration, but I'm still looking.
> > > 
> > > Secondly, to answer your question John, There is no persistent 
> > > connection between the servers. I could feasibly set up an NFS
> > > share between the two but I have a sneaking suspicion that if the
> > > problem is some sort of packet mangling by the VPN during file
> > > transfers, the actual mechanism used to transfer the file will be
> > > irrelevant. However, I will set this up and test it and report
> > > back my results, most likely next Monday.
> > > 
> > > On 3/12/2010 3:41 AM, John Morrison wrote:
> > > > Matt,
> > > >
> > > > If you are using ssh do you need to use scp as well? Or is just
> > > > plain copy ok?
> > > >
> > > > On 10 March 2010 03:04, Darren Tucker<dtucker@xxxxxxxxxx>
> > > > wrote: 
> > > >> Matthew Case wrote:
> > > >> [...]
> > > >>      
> > > >>> I've looked high and low and haven't really come up with
> > > >>> anything definitive. Someone somewhere had mentioned fiddling
> > > >>> with MTU settings, but I'm not really sure what that will
> > > >>> accomplish as I am unfamiliar with what MTU is and does. If
> > > >>> this question has been answered previously, I apologize ahead
> > > >>> of time. Thanks! 
> > > >> This does sound like the MTU problem to which you refer.  See
> > > >> http://www.snailbook.com/faq/mtu-mismatch.auto.html for
> > > >> details.
> > > >>

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