Merge branch 'ip-neigh-skb-reason'

Menglong Dong says:

====================
net: use kfree_skb_reason() for ip/neighbour

In the series "net: use kfree_skb_reason() for ip/udp packet receive",
reasons for skb drops are added to the packet receive process of IP
layer. Link:

https://lore.kernel.org/netdev/20220205074739.543606-1-imagedong@tencent.com/

And in the first patch of this series, skb drop reasons are added to
the packet egress path of IP layer. As kfree_skb() is not used frequent,
I commit these changes at once and didn't create a patch for every
functions that involed. Following functions are handled:

__ip_queue_xmit()
ip_finish_output()
ip_mc_finish_output()
ip6_output()
ip6_finish_output()
ip6_finish_output2()

Following new drop reasons are introduced (what they mean can be seen
in the document of them):

SKB_DROP_REASON_IP_OUTNOROUTES
SKB_DROP_REASON_BPF_CGROUP_EGRESS
SKB_DROP_REASON_IPV6DISABLED
SKB_DROP_REASON_NEIGH_CREATEFAIL

In the 2th and 3th patches, kfree_skb_reason() is used in neighbour
subsystem instead of kfree_skb(). __neigh_event_send() and
arp_error_report() are involed, and following new drop reasons are
introduced:

SKB_DROP_REASON_NEIGH_FAILED
SKB_DROP_REASON_NEIGH_QUEUEFULL
SKB_DROP_REASON_NEIGH_DEAD

Changes since v2:
- fix typo in the 1th patch of 'SKB_DROP_REASON_IPV6DSIABLED' reported
  by Roman

Changes since v1:
- introduce SKB_DROP_REASON_NEIGH_CREATEFAIL for some path in the 1th
  patch
- introduce SKB_DROP_REASON_NEIGH_DEAD in the 2th patch
- simplify the document for the new drop reasons, as David Ahern
  suggested
====================

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