On Wed, May 14, 2014 at 05:24:03AM +0200, Christian Stigen Larsen wrote:
> Hi,
>
> > Den 11. mai 2014 kl. 04:19 skrev Ben Pfaff <b...@nicira.com>:
> >
> >> On Sat, May 10, 2014 at 06:11:29PM +0200, Christian Stigen Larsen wrote:
> >>
> >> Ben Pfaff <b...@nicira.com>:
> >>>> Is do_xlate_actions ("translate actions"?) the wrong place for this kind
> >>>> of
> >>>> stuff? How can I get a pointer to the raw packet data?
> >>>
> >>> Usually, ofproto-dpif-xlate should not actually implement the OpenFlow
> >>> actions.
> >>
> >> Sorry for being trigger-happy, but even if I chose to implement datapath
> >> actions, how can I inspect the packet data? For some reason I get a
> >> NULL-pointer in ctx->xin->packet, while, e.g., OFPACT_OUTPUT in
> >> do_xlate_actions gets the full packet.
> >
> > Often the packet data is not available because userspace is not
> > processing a particular packet. Instead, it is deciding what to do with
> > the entire class of packets specified by the flow data. You are only
> > guaranteed to get full packets if during processing you add a flag for
> > "slow" processing as I described earlier.
>
> Quick question: In odp-execute I call set_ether_type (cant remember the exact
> name at the moment) on the ofpbuf packet. In my example this buffer has
> size=81.
>
> That is all I do in my action, and I can clearly see that it's working -- it
> sets the correct place under offset 12 in packet->l2 w/right number of bytes.
>
> The action after mine is a simple output:1 action, and works too.
>
> However, wireshark reports that the packet is now 67 bytes (from l2 and up)
> -- and my testing shows it indeed is. Strangely enough, data is capped from
> L3, i.e. its tail is truncated. And 81-67=14, which is too much of a
> coincidence as the eth hdr is exactly 14 bytes.
>
> Again, all I do is set the ether type. Do you find this strange, or do you
> immediately know that I must have forgotten setting any magic flags or
> fields? If you can't think of anythinh it could be my code, but I've gone
> through it several times, and I don't do any bad memmoves or stuff like that.
This doesn't ring a bell for me.
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