[ovs-discuss] How does OVS ensure only the first packet of a flow is upcalled?

Ben Pfaff blp at ovn.org
Tue Aug 8 20:18:47 UTC 2017

On Fri, Jul 14, 2017 at 04:14:29PM +0800, 张克尧 wrote:
> The document of ovs says the datapath is a flow-based software
> switch. A flow consists of many packets. Datapath needs to handle
> every packet. When it does't match any datapath flows, it will do
> upcall. Vswitchd needs to handle upcalls and send netlink messages to
> datapath to install the datapath flows. But before the datapath flows
> are added, another packet of the same flow arrived, will the packet be
> upcalled? That means if I send packets at faster rate, more upcalls
> will be expected?

Yes, more than one packet in a flow can go through an upcall.  It's
unusual, though, because most flows start out with a single packet and
do not continue until they receive a response.

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