Merge branch 'ipv6-kfree_skb_reason'

Menglong Dong says:

====================
net: use kfree_skb_reason() for ip/udp packet receive

In this series patches, kfree_skb() is replaced with kfree_skb_reason()
during ipv4 and udp4 packet receiving path, and following drop reasons
are introduced:

SKB_DROP_REASON_SOCKET_FILTER
SKB_DROP_REASON_NETFILTER_DROP
SKB_DROP_REASON_OTHERHOST
SKB_DROP_REASON_IP_CSUM
SKB_DROP_REASON_IP_INHDR
SKB_DROP_REASON_IP_RPFILTER
SKB_DROP_REASON_UNICAST_IN_L2_MULTICAST
SKB_DROP_REASON_XFRM_POLICY
SKB_DROP_REASON_IP_NOPROTO
SKB_DROP_REASON_SOCKET_RCVBUFF
SKB_DROP_REASON_PROTO_MEM

TCP is more complex, so I left it in the next series.

I just figure out how __print_symbolic() works. It doesn't base on the
array index, but searching for symbols by loop. So I'm a little afraid
it's performance.

Changes since v3:
- fix some small problems in the third patch (net: ipv4: use
  kfree_skb_reason() in ip_rcv_core()), as David Ahern said

Changes since v2:
- use SKB_DROP_REASON_PKT_TOO_SMALL for a path in ip_rcv_core()

Changes since v1:
- add document for all drop reasons, as David advised
- remove unreleated cleanup
- remove EARLY_DEMUX and IP_ROUTE_INPUT drop reason
- replace {UDP, TCP}_FILTER with SOCKET_FILTER
====================

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