datapath: refactor ovs flow extract API.

OVS flow extract is called on packet receive or packet
execute code path.  Following patch defines separate API
for extracting flow-key in packet execute code path.

Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Acked-by: Andy Zhou <azhou@nicira.com>
datapath: Avoid using wrong metadata for recic action.

Recirc action needs to extract flow key from packet, it uses tun_info
from OVS_CB for setting tunnel meta data in flow key. But tun_info
can be overwritten by tunnel send action. This would result in wrong
flow key for the recirculation.
Following patch copies flow-key meta data from OVS_CB packet key
itself thus avoids this bug.

Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Acked-by: Andy Zhou <azhou@nicira.com>
datapath: Optimize Flow mask cache hash collision case.

In case hash collision on mask cache, OVS does extra flow lookup.
Following patch avoid it.

Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Acked-by: Jarno Rajahalme <jrajahalme@nicira.com>
datapath: Simplify flow mask cache delete.

Currently on mask delete OVS moves last mask to the deleted
place to keep flow cache consistent and compact for per cpu
cache. But that generate duplicate entries in mask cache array
which results in multiple flow lookups in case we miss flow
cache.
Following patch simply sets NULL for deleted entry.

Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Acked-by: Andy Zhou <azhou@nicira.com>