[bpf-next 0/2] cleanup SOCK_DEBUG() and introduce BPF_SOCK_OPS_STATS_CB

[Yafang Shao <laoar.shao@gmail.com>]

SOCK_DEBUG is a very ancient debugging interface, and it's not very useful
for debugging.
This pacthset cleanups SOCK_DEBUG() and replace it with a new methord
based on BPF.

I cleanup SOCK_DEBUG() only for TCP, and other protocols are kept as is.

After this patchset, the SO_DEBUG interface will not take any effect for
TCP, but I still keep it in sock_{s,g}etsockopt() for TCP to avoid breaking
applications.

In the future we may extend tcp_stats() as bellow or something else to
cover all the LINUX_MIB_* and TCP_MIB_* proposaled[0] in the netconf2018.

now:
	tcp_stats(struct sock *sk, int mib_idx)
future:
	tcp_stats(struct sock *sk, int mib_idx, int packets)
	The argument packets can be 1 to indicates this is a event only;
	and skb_shinfo(skb)->gso_segs to indicates the number of packets
	are also concerned.

[0] page 14,
http://vger.kernel.org/netconf2018_files/BrendanGregg_netconf2018.pdf

Yafang Shao (2):
  tcp: replace SOCK_DEBUG() with tcp_stats()
  bpf: add BPF_SOCK_OPS_STATS_CB for tcp_stats()

 include/uapi/linux/bpf.h  |  5 +++++
 include/uapi/linux/snmp.h |  3 +++
 net/ipv4/proc.c           |  3 +++
 net/ipv4/tcp_input.c      | 27 ++++++++++++---------------
 net/ipv6/tcp_ipv6.c       |  2 --
 5 files changed, 23 insertions(+), 17 deletions(-)

-- 
1.8.3.1