Date:   Fri,  7 Dec 2018 12:44:24 +0100
From:   Björn Töpel <bjorn.topel@...il.com>
To:     bjorn.topel@...il.com, magnus.karlsson@...el.com,
        magnus.karlsson@...il.com, ast@...nel.org, daniel@...earbox.net,
        netdev@...r.kernel.org
Cc:     Björn Töpel <bjorn.topel@...el.com>,
        brouer@...hat.com, u9012063@...il.com, qi.z.zhang@...el.com
Subject: [PATCH bpf-next 0/7] Add XDP_ATTACH bind() flag to AF_XDP sockets

From: Björn Töpel <bjorn.topel@...el.com>

Hi!

This patch set adds support for a new XDP socket bind option,
XDP_ATTACH.

The rationale behind attach is performance and ease of use. Many XDP
socket users just need a simple way of creating/binding a socket and
receiving frames right away without loading an XDP program.

XDP_ATTACH adds a mechanism we call "builtin XDP program" that simply
is a kernel provided XDP program that is installed to the netdev when
XDP_ATTACH is being passed as a bind() flag.

The builtin program is the simplest program possible to redirect a
frame to an attached socket. In restricted C it would look like this:
    
  SEC("xdp")
  int xdp_prog(struct xdp_md *ctx)
  {
        return bpf_xsk_redirect(ctx);
  }
    
The builtin program loaded via XDP_ATTACH behaves, from an
install-to-netdev/uninstall-from-netdev point of view, differently
from regular XDP programs. The easiest way to look at it is as a
2-level hierarchy, where regular XDP programs has precedence over the
builtin one.
    
If no regular XDP program is installed to the netdev, the builtin will
be install. If the builtin program is installed, and a regular is
installed, regular XDP program will have precedence over the builtin
one.
    
Further, if a regular program is installed, and later removed, the
builtin one will automatically be installed.
    
The sxdp_flags field of struct sockaddr_xdp gets two new options
XDP_BUILTIN_SKB_MODE and XDP_BUILTIN_DRV_MODE, which maps to the
corresponding XDP netlink install flags.

The builtin XDP program functionally adds even more complexity to the
already hard to read dev_change_xdp_fd. Maybe it would be simpler to
store the program in the struct net_device together with the install
flags instead of calling the ndo_bpf multiple times?

The outline of the series is as following:
  patch 1-2: Introduce the first part of XDP_ATTACH, simply adding
             the socket to the netdev structure.
  patch 3:   Add a new BPF function, bpf_xsk_redirect, that 
             redirects a frame to an attached socket.
  patch 4-5: Preparatory commits for built in BPF programs
  patch 6:   Make XDP_ATTACH load a builtin XDP program
  patch 7:   Extend the samples application with XDP_ATTACH
             support

Patch 1 through 3 gives the performance boost and make it possible to
use AF_XDP sockets without an XSKMAP, but still requires an explicit
XDP program to be loaded.

Patch 4 through 6 make it possible to use XDP socket without explictly
loading an XDP program.

The performance numbers for rxdrop (Intel(R) Xeon(R) Gold 6154 CPU @
3.00GHz):

XDP_SKB:
XSKMAP:     2.8 Mpps
XDP_ATTACH: 2.9 Mpps

XDP_DRV - copy:
XSKMAP:     8.5 Mpps
XDP_ATTACH: 9.3 Mpps

XDP_DRV - zero-copy:
XSKMAP:     15.1 Mpps
XDP_ATTACH: 17.3 Mpps

Thanks!
Björn


Björn Töpel (7):
  xsk: simplify AF_XDP socket teardown
  xsk: add XDP_ATTACH bind() flag
  bpf: add bpf_xsk_redirect function
  bpf: prepare for builtin bpf program
  bpf: add function to load builtin BPF program
  xsk: load a builtin XDP program on XDP_ATTACH
  samples: bpf: add support for XDP_ATTACH to xdpsock

 include/linux/bpf.h         |   2 +
 include/linux/filter.h      |   4 +
 include/linux/netdevice.h   |  11 +++
 include/net/xdp_sock.h      |   2 +
 include/trace/events/xdp.h  |  61 +++++++++++++++
 include/uapi/linux/bpf.h    |  14 +++-
 include/uapi/linux/if_xdp.h |   9 ++-
 kernel/bpf/syscall.c        |  91 ++++++++++++++--------
 net/core/dev.c              |  84 +++++++++++++++++++--
 net/core/filter.c           | 100 ++++++++++++++++++++++++
 net/xdp/xsk.c               | 146 +++++++++++++++++++++++++++++-------
 samples/bpf/xdpsock_user.c  | 108 ++++++++++++++++----------
 12 files changed, 524 insertions(+), 108 deletions(-)

-- 
2.19.1

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