Merge branch 'vxlan-skb-drop-reasons'

Menglong Dong says:

====================
net: vxlan: add skb drop reasons support

In this series, we add skb drop reasons support to VXLAN, and following
new skb drop reasons are introduced:

  SKB_DROP_REASON_VXLAN_INVALID_HDR
  SKB_DROP_REASON_VXLAN_VNI_NOT_FOUND
  SKB_DROP_REASON_VXLAN_ENTRY_EXISTS
  SKB_DROP_REASON_VXLAN_NO_REMOTE
  SKB_DROP_REASON_MAC_INVALID_SOURCE
  SKB_DROP_REASON_IP_TUNNEL_ECN
  SKB_DROP_REASON_TUNNEL_TXINFO
  SKB_DROP_REASON_LOCAL_MAC

We add some helper functions in this series, who will capture the drop
reasons from pskb_may_pull_reason and return them:

  pskb_network_may_pull_reason()
  pskb_inet_may_pull_reason()

And we also make the following functions return skb drop reasons:

  skb_vlan_inet_prepare()
  vxlan_remcsum()
  vxlan_snoop()
  vxlan_set_mac()

Changes since v6:
- fix some typos in the document for SKB_DROP_REASON_TUNNEL_TXINFO

Changes since v5:
- fix some typos in the document for SKB_DROP_REASON_TUNNEL_TXINFO

Changes since v4:
- make skb_vlan_inet_prepare() return drop reasons, instead of introduce
  a wrapper for it in the 3rd patch.
- modify the document for SKB_DROP_REASON_LOCAL_MAC and
  SKB_DROP_REASON_TUNNEL_TXINFO.

Changes since v3:
- rename SKB_DROP_REASON_VXLAN_INVALID_SMAC to
  SKB_DROP_REASON_MAC_INVALID_SOURCE in the 6th patch

Changes since v2:
- move all the drop reasons of VXLAN to the "core", instead of introducing
  the VXLAN drop reason subsystem
- add the 6th patch, which capture the drop reasons from vxlan_snoop()
- move the commits for vxlan_remcsum() and vxlan_set_mac() after
  vxlan_rcv() to update the call of them accordingly
- fix some format problems

Changes since v1:
- document all the drop reasons that we introduce
- rename the drop reasons to make them more descriptive, as Ido advised
- remove the 2nd patch, which introduce the SKB_DR_RESET
- add the 4th patch, which adds skb_vlan_inet_prepare_reason() helper
- introduce the 6th patch, which make vxlan_set_mac return drop reasons
- introduce the 10th patch, which uses VXLAN_DROP_NO_REMOTE as the drop
  reasons, as Ido advised
====================

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