[ovs-discuss] Packets not forwarded to queues after hitting flows in OVS QoS

Ben Pfaff blp at ovn.org
Wed Dec 14 17:20:47 UTC 2016


Open vSwitch has no control over how Linux does IP masquerading.  I
don't know what IP masquerading does to a packet's skb_priority, nor do
I know how you configured IP masquerading, so I don't know the answer.

On Wed, Dec 14, 2016 at 11:36:05AM +0100, Santhosh R P wrote:
> Hi Ben,
> 
> In the case where IP masquerading takes place, the packet from VM1 at
> in_port(3)
> is forwarded to enp0s25 at in_port(2) for masquerading, and then after
> masquerading, the packet leaves from in_port(2) to in_port(1) for egress
> queues and then transmission.
> 
> If there is no masquerading, will the packet from VM1 at in_port(3) be
> directly forwarded to in_port(1) ?
> 
> I am new to OVS to suggest you anything now and have to make another setup
> without masquerading to verify this, so asking you to confirm if this is
> how it should be. Thanks for your help.
> 
> Best Regards,
> Santhosh.
> 
> On Tue, Dec 13, 2016 at 9:54 PM, Ben Pfaff <blp at ovn.org> wrote:
> 
> > On Tue, Dec 13, 2016 at 08:40:41PM +0100, Santhosh R P wrote:
> > > When I add a flow like this,
> > >
> > > ovs-ofctl add-flow test priority=2000,in_port=2,
> > actions=set_queue:1,normal
> > >
> > > ovs-dpctl dump-flows shows this (captured during the test):
> > >
> > > recirc_id(0),skb_priority(0),in_port(3),eth(src=52:54:00:
> > 3e:2c:cf,dst=90:1b:0e:06:0e:c4),eth_type(0x0800),ipv4(frag=no),
> > > packets:21617, bytes:904012530, used:0.000s, flags:SP.,
> > > actions:set(skb_priority(0x10002)),2
> > > recirc_id(0),in_port(2),eth(src=90:1b:0e:06:0e:c4,dst=00:
> > 00:5e:00:01:01),eth_type(0x0800),ipv4(frag=no),
> > > packets:21652, bytes:904023433, used:0.000s, flags:SP., actions:1
> > >
> > > I see that the packet from VM1 in in_port(3) is set with
> > > skb_priority(0x10002) and sent to port 2. Here, masquerading takes place
> > > and the packet is sent out from the host at port 1. Before the packet
> > > reaches the created egress queues, the skb_priority is reset. The
> > > masqueraded packet reaches the default queue and no QoS takes place.
> >
> > If you have IP masquerading configured, and masquerading resets the
> > skb_priority, then I'm not sure what OVS can do about that.  What do you
> > suggest?
> >


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