Re: [lvs-users] ipvsadm and packets leaving a gre tunnel

To: " users mailing list." <lvs-users@xxxxxxxxxxxxxxxxxxxxxx>
Subject: Re: [lvs-users] ipvsadm and packets leaving a gre tunnel
From: Joseph Mack NA3T <jmack@xxxxxxxx>
Date: Wed, 30 Jul 2008 06:13:19 -0700 (PDT)
On Wed, 30 Jul 2008, Marco Lorig wrote:

> I found out something interesting:
> The Realserver is responding and transferring data correctly if the transfer 
> is initiated by the client:
> "Client ->scp put file -> Server" works perfectly.
> "Client ->scp get file -> Server" still hangs.

hmm (don't have a clue at the moment).

are there any assymetries involved? Like a "get" needs to 
open a connection (identd?) that "put" doesn't (I can't 
imagine it, but something assymetric seems to be going on). 
I don't expect there's any assymetry in the scp tcp 
connection itself (it's just a single port connection, and 
tcp won't know whether there's a get or a put going on 

I think you're using LVS-NAT, so you have the same route for 
packets in both directions. Do you have any iptables rules 
that might affect what's going on? (even so they're at the 
tcp level and will affect a get and put the same).

And the problem is gre tunnel dependant? ie it works 
fine if you have two directors connected by a regular 
non-gre path.

Can you do try an alternate protocol to see if it's 
something in scp? I hate to suggest ftp, since it's 
problematic with LVS (it works OK if you set it up properly 
- see the HOWTO - but it's easy to not set it up properly), 
but I can't think of another protocol that's not based on 
the sxxx protocol.

Joseph Mack NA3T EME(B,D), FM05lw North Carolina
jmack (at) wm7d (dot) net - azimuthal equidistant map
generator at
Homepage It's GNU/Linux!

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