Merge branch 'tap-XDP-support'

Merge branch 'tap-XDP-support'

Jason Wang says:

====================
XDP support for tap

This series tries to implement XDP support for tap. Two path were
implemented:

- fast path: small & non-gso packet, For performance reason we do it
  at page level and use build_skb() to create skb if necessary.
- slow path: big or gso packet, we don't want to lose the capability
  compared to generic XDP, so we export some generic xdp helpers and
  do it after skb was created.

xdp1 shows about 41% improvement, xdp_redirect shows about 60%
improvement.

Changes from V1:
- fix the race between xdp set and free
- don't hold extra refcount
- add XDP_REDIRECT support

Please review.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>