tunneling: Avoid datapath-recirc by combining recirc actions at xlate.

tunneling: Avoid datapath-recirc by combining recirc actions at xlate.

This patch set removes the recirculation of encapsulated tunnel packets
if possible. It is done by computing the post tunnel actions at the time of
translation. The combined nested action set are programmed in the datapath
using CLONE action.

The following test results shows the performance improvement offered by
this optimization for tunnel encap.

          +-------------+
      dpdk0 |             |
         -->o    br-in    |
            |             o--> gre0
            +-------------+

                   --> LOCAL
            +-----------o-+
            |             | dpdk1
            |    br-p1    o-->
            |             |
            +-------------+

Test result on OVS master with DPDK 16.11.2 (Without optimization):

 # dpdk0

 RX packets         : 7037641.60  / sec
 RX packet errors   : 0  / sec
 RX packets dropped : 7730632.90  / sec
 RX rate            : 402.69 MB/sec

 # dpdk1

 TX packets         : 7037641.60  / sec
 TX packet errors   : 0  / sec
 TX packets dropped : 0  / sec
 TX rate            : 657.73 MB/sec
 TX processing cost per TX packets in nsec : 142.09

Test result on OVS master + DPDK 16.11.2 (With optimization):

 # dpdk0

 RX packets         : 9386809.60  / sec
 RX packet errors   : 0  / sec
 RX packets dropped : 5381496.40  / sec
 RX rate            : 537.11 MB/sec

 # dpdk1

 TX packets         : 9386809.60  / sec
 TX packet errors   : 0  / sec
 TX packets dropped : 0  / sec
 TX rate            : 877.29 MB/sec
 TX processing cost per TX packets in nsec : 106.53

The offered performance gain is approx 30%.

Signed-off-by: Sugesh Chandran <sugesh.chandran@intel.com>
Signed-off-by: Zoltán Balogh <zoltan.balogh@ericsson.com>
Co-authored-by: Zoltán Balogh <zoltan.balogh@ericsson.com>
Signed-off-by: Joe Stringer <joe@ovn.org>