[ovs-discuss] DP_Packet Payload Modification

Ben Pfaff blp at ovn.org
Fri Jun 5 20:18:26 UTC 2020

The controller can get as much of the packet as it wants.  The number of
bytes to send is an operand of the action that sends a packet to the

Of course it's doable in OVS--but it's going to be more work and you'll
have to understand OVS internals instead of OpenFlow.

On Fri, Jun 05, 2020 at 07:47:56PM +0000, Luca Mancini wrote:
> Hi Ben,
> I thought controllers didn’t have access to the complete packet but just the (packet_in msgs), so I was told to implement this in the switches and use the controller just as the “brain”.
> I’d much rather work on a controller to be honest, however, do you not think its doable at all in OVS?
> Cheers,
> Luca
> From: Ben Pfaff<mailto:blp at ovn.org>
> Sent: Friday, June 5, 2020 21:32
> To: Luca Mancini<mailto:luca.mancini at outlook.com>
> Cc: Gregory Rose<mailto:gvrose8192 at gmail.com>; ovs-discuss at openvswitch.org<mailto:ovs-discuss at openvswitch.org>
> Subject: Re: [ovs-discuss] DP_Packet Payload Modification
> On Fri, Jun 05, 2020 at 05:56:54PM +0000, Luca Mancini wrote:
> > Basically, I’m implementing a custom action which is meant to buffer
> > an x amount of dp_packets that match a certain flow, and then send a
> > new packet directly from the switch, containing the buffer of packets,
> > as its payload. At some other switch this payload is then meant to be
> > extracted so that I can retrieve the buffer of dp_packets and send the
> > single packets contained in the buffer to the correct hosts.
> >
> > My action is implemented in userspace only for now since efficiency
> > isn’t a concern for me atm. I already implemented the buffering
> > mechanism and it works, and now I’m trying to create this custom udp
> > packet so that I can store the buffer in it. For now I’m only trying
> > to create a dummy udp packet with a “hello world” string as its
> > payload just to see if I can create this custom packet however I just
> > can’t figure out what I’m missing. My most recent attempt is the
> > following
> I'd use a local controller for this. Then you don't have to implement
> anything in OVS at all.

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