[v3,bpf-next,0/8] veth: Driver XDP

From: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>

This patch set introduces driver XDP for veth.
Basically this is used in conjunction with redirect action of another XDP
program.

  NIC -----------> veth===veth
 (XDP) (redirect)        (XDP)

In this case xdp_frame can be forwarded to the peer veth without
modification, so we can expect far better performance than generic XDP.

Envisioned use-cases
--------------------

* Container managed XDP program
Container host redirects frames to containers by XDP redirect action, and
privileged containers can deploy their own XDP programs.

* XDP program cascading
Two or more XDP programs can be called for each packet by redirecting
xdp frames to veth.

* Internal interface for an XDP bridge
When using XDP redirection to create a virtual bridge, veth can be used
to create an internal interface for the bridge.

Implementation
--------------

This changeset is making use of NAPI to implement ndo_xdp_xmit and
XDP_TX/REDIRECT. This is mainly because XDP heavily relies on NAPI
context.
 - patch 1: Export a function needed for veth XDP.
 - patch 2-3: Basic implementation of veth XDP.
 - patch 4-5: Add ndo_xdp_xmit.
 - patch 6-7: Add XDP_TX and XDP_REDIRECT.
 - patch 8: Performance optimization for multi-queue env.

Tests and performance numbers
-----------------------------

Tested with a simple XDP program which only redirects packets between
NIC and veth. I used i40e 25G NIC (XXV710) for the physical NIC. The
server has 20 of Xeon Silver 2.20 GHz cores.

  pktgen --(wire)--> XXV710 (i40e) <--(XDP redirect)--> veth===veth (XDP)

The rightmost veth loads XDP progs and just does DROP or TX. The number
of packets is measured in the XDP progs. The leftmost pktgen sends
packets at 37.1 Mpps (almost 25G wire speed).

veth XDP action    Flows    Mpps
================================
DROP                   1    10.6
DROP                   2    21.2
DROP                 100    36.0
TX                     1     5.0
TX                     2    10.0
TX                   100    31.0

I also measured netperf TCP_STREAM but was not so great performance due
to lack of tx/rx checksum offload and TSO, etc.

  netperf <--(wire)--> XXV710 (i40e) <--(XDP redirect)--> veth===veth (XDP PASS)

Direction         Flows   Gbps
==============================
external->veth        1   20.8
external->veth        2   23.5
external->veth      100   23.6
veth->external        1    9.0
veth->external        2   17.8
veth->external      100   22.9

Also tested doing ifup/down or load/unload a XDP program repeatedly
during processing XDP packets in order to check if enabling/disabling
NAPI is working as expected, and found no problems.

Note:
This patchset depends on commit d8d7218ad842 ("xdp: XDP_REDIRECT should
check IFF_UP and MTU") which is currently in DaveM's net-next tree.

v3:
- Drop skb bulk xmit patch since it makes little performance
  difference. The hotspot in TCP skb xmit at this point is checksum
  computation in skb_segment and packet copy on XDP_REDIRECT due to
  cloned/nonlinear skb.
- Fix race on closing device.
- Add extack messages in ndo_bpf.

v2:
- Squash NAPI patch with "Add driver XDP" patch.
- Remove conversion from xdp_frame to skb when NAPI is not enabled.
- Introduce per-queue XDP ring (patch 8).
- Introduce bulk skb xmit when XDP is enabled on the peer (patch 9).

Signed-off-by: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>

Toshiaki Makita (8):
  net: Export skb_headers_offset_update
  veth: Add driver XDP
  veth: Avoid drops by oversized packets when XDP is enabled
  veth: Handle xdp_frames in xdp napi ring
  veth: Add ndo_xdp_xmit
  xdp: Add a flag for disabling napi_direct of xdp_return_frame in
    xdp_mem_info
  veth: Add XDP TX and REDIRECT
  veth: Support per queue XDP ring

 drivers/net/veth.c     | 735 ++++++++++++++++++++++++++++++++++++++++++++++++-
 include/linux/skbuff.h |   1 +
 include/net/xdp.h      |   4 +
 net/core/skbuff.c      |   3 +-
 net/core/xdp.c         |   6 +-
 5 files changed, 737 insertions(+), 12 deletions(-)