Re: [LARTC] Wondershaper breaks IPSec tunnels

[Damion de Soto <damion@snapgear.com>]

Hi Jason,

> Am I silently being told that this is the wrong question to ask of this
> list?  :)

Probably.  I'll reply but I think it'll only be of statistic interest.


> | I now have a situation where I get to use traffic shaping for a client.
> | ~ We implemented the WonderShaper script on our own firewall and
> | experienced no problems.  I made some modifications to it to add IPSec
> | protocol packets into the 1:10 high priority class using the u32 filter.
> | ~ So far on our network, it's worked flawlessly, and we've received much
> | benefit from it.  Interactive SSH and VNC sessions are now much, much
> | smoother when, for example, we do an apt-get update/upgrade/install at
> | the same time or any downloading, e-mailing, etc.
Yeah, I've done the same thing.


> | However, yesterday, I installed it for a client using the same
> | modifications we have been using, and at first, I only added the
> | modifications to the client's external interface (eth1).  Within an
> | hour, the FreeS/WAN VPN connections could no longer negotiate new
> | tunnels when rekeying.  In his scenario, he has two DSL connections
> | (eth1, eth2) coming into the firewall with a single internal interface
> | (eth0).  It appears that something broke the VPN negotiation when I
> | installed the WonderShaper.  As long as the tunnels are up when I start
> | WonderShaper, they work fine, until they need to rekey.  Then they throw
> | errors saying things like "max number of retransmissions reached", and
> | "Possible authentication failure: no acceptable response to our first
> | encrypted message", etc.  The moment I 'stop' the WonderShaper, the VPN
> | tunnels can be reestablished successfully.
> |
> | I was wondering if anyone else has experienced these kinds of problems
> | with the WonderShaper and IPSec tunnels?
Nope, never seen traffic shaping cause problems like that.

> | Also, I'm attempting to prioritize RDP packets on the ipsec0 interface.
> | ~ Is this as simple as copying every line in the script except changing
> | $DEV to $DEV2 which is assigned to ipsec0 and adding a u32 match for
> | sport 3389?  That's currently what I've done.
I believe so.

> | I just can't get over the fact that it works (in almost the exact same
> | scenario, except for the 2 DSL circuits) on our firewall, but not our
> | client's.

> | These are the changes that I made to match IPSec traffic and place it
> | into the high priority class (where DEV = eth1 -- the Internet):
I've put my IPSec traffic in the middle class.

The only thing I can think of, is that the particular client has saturated one of the 
  lower priority leaf classes, and delayed the traffic in the high-priority class for 
too long for a valid key exchange.

Unless you've changed it, the wondershaper doesn't specify ceil values, which means 
they get set to the rate value, and unless you've changed the way it calculates it's 
percentage rate values, the sum of the leaf rates can exceed the parent.
which i believe can lead to weird and/or bad behaviour.




-- 
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Damion de Soto - Software Engineer  email:     damion@snapgear.com
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