[ovs-dev] 答复: Question about ovs megaflow with move NXM_OF_IP_DST actions

[Ben Pfaff]

On Wed, Apr 04, 2018 at 07:20:05AM +0000, Lilijun (Jerry, Cloud Networking) wrote:
> In my test, add one flow to br-ovs, and running one vm connected this br-ovs:
> cookie=0x0, duration=286.272s, table=31, n_packets=2, n_bytes=196, idle_age=161, priority=61010,ip,metadata=0x2b193,dl_dst=00:00:00:04:06:03 actions=move:NXM_OF_IP_DST[]->NXM_NX_REG0[],load:0x8439ce602f->OXM_OF_METADATA[],resubmit(,32)
> 
> when sending packets with random dst ip addr from vm, I found many datapath exact flows are gernerated instead of one megaflow entry. One dst ip generated one exact flow.
> 
> What's the megaflow match policy about move:NXM_OF_IP_DST?  Why we don't using megaflow wildcard on the openflow actions of move:NXM_OF_IP_DST[]?

I think what you're seeing is that OVS sees the "move" as reading all of
the IP destination field, so that matching on it in the megaflow is
needed.  OVS isn't smart enough to notice that nothing is done with reg0
afterward.