Re: [RFC PATCH 0/5] Add driver bpf hook for early packet drop

[Tom Herbert <tom@herbertland.com>]

On Fri, Apr 1, 2016 at 9:21 PM, Brenden Blanco <bblanco@plumgrid.com> wrote:
> This patch set introduces new infrastructure for programmatically
> processing packets in the earliest stages of rx, as part of an effort
> others are calling Express Data Path (XDP) [1]. Start this effort by
> introducing a new bpf program type for early packet filtering, before even
> an skb has been allocated.
>
> With this, hope to enable line rate filtering, with this initial
> implementation providing drop/allow action only.
>
> Patch 1 introduces the new prog type and helpers for validating the bpf
> program. A new userspace struct is defined containing only len as a field,
> with others to follow in the future.
> In patch 2, create a new ndo to pass the fd to support drivers.
> In patch 3, expose a new rtnl option to userspace.
> In patch 4, enable support in mlx4 driver. No skb allocation is required,
> instead a static percpu skb is kept in the driver and minimally initialized
> for each driver frag.
> In patch 5, create a sample drop and count program. With single core,
> achieved ~14.5 Mpps drop rate on a 40G mlx4. This includes packet data
> access, bpf array lookup, and increment.
>
Very nice! Do you think this hook will be sufficient to implement a
fast forward patch also?

Tom

> Interestingly, accessing packet data from the program did not have a
> noticeable impact on performance. Even so, future enhancements to
> prefetching / batching / page-allocs should hopefully improve the
> performance in this path.
>
> [1] https://github.com/iovisor/bpf-docs/blob/master/Express_Data_Path.pdf
>
> Brenden Blanco (5):
>   bpf: add PHYS_DEV prog type for early driver filter
>   net: add ndo to set bpf prog in adapter rx
>   rtnl: add option for setting link bpf prog
>   mlx4: add support for fast rx drop bpf program
>   Add sample for adding simple drop program to link
>
>  drivers/net/ethernet/mellanox/mlx4/en_netdev.c |  61 ++++++++++
>  drivers/net/ethernet/mellanox/mlx4/en_rx.c     |  18 +++
>  drivers/net/ethernet/mellanox/mlx4/mlx4_en.h   |   2 +
>  include/linux/netdevice.h                      |   8 ++
>  include/uapi/linux/bpf.h                       |   5 +
>  include/uapi/linux/if_link.h                   |   1 +
>  kernel/bpf/verifier.c                          |   1 +
>  net/core/dev.c                                 |  12 ++
>  net/core/filter.c                              |  68 +++++++++++
>  net/core/rtnetlink.c                           |  10 ++
>  samples/bpf/Makefile                           |   4 +
>  samples/bpf/bpf_load.c                         |   8 ++
>  samples/bpf/netdrvx1_kern.c                    |  26 +++++
>  samples/bpf/netdrvx1_user.c                    | 155 +++++++++++++++++++++++++
>  14 files changed, 379 insertions(+)
>  create mode 100644 samples/bpf/netdrvx1_kern.c
>  create mode 100644 samples/bpf/netdrvx1_user.c
>
> --
> 2.8.0
>