[ovs-discuss] How to send all packets to userspace?

[Xuemei Liu]

Let me try to describe it. Suppose the topology is h1-s1-h2, where h1, h2
are hosts, and s1 is the ovs switch. I add policy in s1 to forward packets
with dstip of h2 to h2. Then I test in two scenarios.
1. h1 sends 9 packets (3 packet for each of 3 different flows) to h2. With
your methods, userspace in s1 can accept all the packets, and h2 can
receive all the 9 packets. Work perfect.
2. h1 sends 10000 packets to h2. In this case, h2 receives the same packets
as userspace in s1 does. However, the number of packets received is much
less than 10000. Which means many packets are lost in s1.
Is this clear now?

Thanks,
Xuemei

On Thu, Jul 23, 2015 at 4:18 PM, Ben Pfaff <blp at nicira.com> wrote:

> That's too vague for me to guess.  What packets are getting lost?
>
> On Thu, Jul 23, 2015 at 04:10:14PM -0700, Xuemei Liu wrote:
> > Hi, Ben,
> >
> > I tried your method, but the switch seems to drop some packets, as it
> does
> > not output the expected packets that I forward to send to it. Any advice?
> >
> > Thanks,
> > Xuemei
> >
> > On Thu, Jul 23, 2015 at 10:19 AM, Xuemei Liu <lxuemei3000 at gmail.com>
> wrote:
> >
> > > Hi, Ben,
> > >
> > > Thanks for your response.
> > > "You realize that this will be terrible for performance, right?"
> > > In fact, I have not got all packets sent to user space. That is the
> > > problem I am facing now. I think performance might be another problem
> after
> > > I can receive all packet in user space.
> > >
> > > Thanks,
> > > Xuemei
> > >
> > > On Thu, Jul 23, 2015 at 10:13 AM, Ben Pfaff <blp at nicira.com> wrote:
> > >
> > >> On Thu, Jul 23, 2015 at 10:04:23AM -0700, Xuemei Liu wrote:
> > >> > I am new to ovs, and I am trying to send all packets from kernel
> space
> > >> to
> > >> > user space. I comment the "unlikely(!flow)" in datapath/datapath.c.
> > >> > However, it seems I just receive the first packet of each flow (the
> > >> first
> > >> > packet that match one forwarding rule in the bridge) in user space.
> > >> Could
> > >> > anyone tell me why? and is there other way to achieve my goal?
> > >>
> > >> You realize that this will be terrible for performance, right?
> > >>
> > >> It's kind of a waste to modify the kernel module for this.  I'd just
> > >> modify userspace to send all packets to userspace, something like
> this:
> > >>
> > >> diff --git a/ofproto/ofproto-dpif-xlate.c
> b/ofproto/ofproto-dpif-xlate.c
> > >> index 52395a7..a98406a 100644
> > >> --- a/ofproto/ofproto-dpif-xlate.c
> > >> +++ b/ofproto/ofproto-dpif-xlate.c
> > >> @@ -4777,7 +4777,7 @@ xlate_actions(struct xlate_in *xin, struct
> > >> xlate_out *xout)
> > >>
> > >>      ctx.xin = xin;
> > >>      ctx.xout = xout;
> > >> -    ctx.xout->slow = 0;
> > >> +    ctx.xout->slow = SLOW_ACTION;
> > >>      ctx.xout->has_learn = false;
> > >>      ctx.xout->has_normal = false;
> > >>      ctx.xout->has_fin_timeout = false;
> > >>
> > >
> > >
>
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