I sent a series that adds these features:
https://patchwork.ozlabs.org/project/openvswitch/list/?series=24270
On Thu, Jan 18, 2018 at 09:34:40AM +1300, Brad Cowie wrote:
> We've had a bit of a think about this, variable length probably isn't too
> important (static 64b is probably fine), but yes, being able to set those
> 64 bytes will be quite useful with say with an extra "payload=0xC0FEFE"
> argument on ofproto/trace.
>
> Brad
>
> On 18 January 2018 at 07:17, Ben Pfaff <[email protected]> wrote:
>
> > OK, sounds good.
> >
> > Do you think you need the ability to inject payloads of a specific
> > length or content? It's easy to, for example, always generate 64 bytes
> > of payload, but it would be a little more challenging to plumb through
> > extra data or metadata.
> >
> > On Mon, Jan 15, 2018 at 01:48:10PM +1300, Brad Cowie wrote:
> > > Hi Ben,
> > >
> > > We looked a bit closer at this problem, and turns out the packet header
> > > size we were getting back from Ryu wasn't what we were expecting. We're
> > now
> > > calculating this correctly ourselves (instead of relying on Ryu) which
> > > removes the need for disabling the IP header length check in the tutorial
> > > (I've send another patch towards [email protected] that does this).
> > >
> > > As for being able to inject payload into ofproto/trace generated packets
> > I
> > > think this would be quite useful for folks like us. We are looking at
> > > moving our test suite to using ofproto/trace to generate packets (instead
> > > of scapy) for throwing at test scenarios because it's considerably more
> > > lightweight and we are already using openvswitch as the core of our test
> > > suite.
> > >
> > > Brad
> > >
> > > On 9 January 2018 at 05:51, Ben Pfaff <[email protected]> wrote:
> > >
> > > > [dropping OP, who probably doesn't care]
> > > >
> > > > On Sat, Jan 06, 2018 at 12:07:09PM +1300, Brad Cowie wrote:
> > > > > What happened is that in faucet 1.6.12 we added a bunch of new packet
> > > > > handling sanity checks to help improve security of faucet's packet
> > > > > handling. Packets made by ofproto/trace -generate will have a
> > zero-length
> > > > > payload which trips some of our sanity checks which will cause us to
> > drop
> > > > > the packet.
> > > >
> > > > If OVS generated a packet with some nonzero size payload, would that
> > fix
> > > > the problem? It's easy for us to change the details, we would just add
> > > > some code to flow_compose_l4() in lib/flow.c to put some L7 data into
> > > > the UDP packet.
> > > >
> > > > I suspect that changing the tutorial from using UDP to TCP might also
> > > > work around the issue? After all, TCP packets with empty payloads are
> > > > pretty common, at least (off the top of my head) if they have SYN or
> > FIN
> > > > or RST attached.
> > > >
> >
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