netdev - Re: [PATCHv5 bpf-next 1/3] xdp: add a new helper for dev map multicast support

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Message-ID: <CAEf4BzZmwDjWZJJiuiPWD+ByDqugVA3GQSe6OJDZdd0+zf-8JA@mail.gmail.com>
Date:   Tue, 30 Jun 2020 22:09:39 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Hangbin Liu <liuhangbin@...il.com>
Cc:     bpf <bpf@...r.kernel.org>, Networking <netdev@...r.kernel.org>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Jiri Benc <jbenc@...hat.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Eelco Chaudron <echaudro@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
Subject: Re: [PATCHv5 bpf-next 1/3] xdp: add a new helper for dev map
 multicast support

On Tue, Jun 30, 2020 at 9:21 PM Hangbin Liu <liuhangbin@...il.com> wrote:
>
> This patch is for xdp multicast support. In this implementation we
> add a new helper to accept two maps: forward map and exclude map.
> We will redirect the packet to all the interfaces in *forward map*, but
> exclude the interfaces that in *exclude map*.
>
> To achive this I add a new ex_map for struct bpf_redirect_info.
> in the helper I set tgt_value to NULL to make a difference with
> bpf_xdp_redirect_map()
>
> We also add a flag *BPF_F_EXCLUDE_INGRESS* incase you don't want to
> create a exclude map for each interface and just want to exclude the
> ingress interface.
>
> The general data path is kept in net/core/filter.c. The native data
> path is in kernel/bpf/devmap.c so we can use direct calls to
> get better performace.
>
> v5:
> a) Check devmap_get_next_key() return value.
> b) Pass through flags to __bpf_tx_xdp_map() instead of bool value.
> c) In function dev_map_enqueue_multi(), consume xdpf for the last
>    obj instead of the first on.
> d) Update helper description and code comments to explain that we
>    use NULL target value to distinguish multicast and unicast
>    forwarding.
> e) Update memory model, memory id and frame_sz in xdpf_clone().
>
> v4: Fix bpf_xdp_redirect_map_multi_proto arg2_type typo
>
> v3: Based on Toke's suggestion, do the following update
> a) Update bpf_redirect_map_multi() description in bpf.h.
> b) Fix exclude_ifindex checking order in dev_in_exclude_map().
> c) Fix one more xdpf clone in dev_map_enqueue_multi().
> d) Go find next one in dev_map_enqueue_multi() if the interface is not
>    able to forward instead of abort the whole loop.
> e) Remove READ_ONCE/WRITE_ONCE for ex_map.
>
> v2: Add new syscall bpf_xdp_redirect_map_multi() which could accept
> include/exclude maps directly.
>
> Signed-off-by: Hangbin Liu <liuhangbin@...il.com>
> ---
>  include/linux/bpf.h            |  20 +++++
>  include/linux/filter.h         |   1 +
>  include/net/xdp.h              |   1 +
>  include/uapi/linux/bpf.h       |  25 +++++-
>  kernel/bpf/devmap.c            | 154 +++++++++++++++++++++++++++++++++
>  kernel/bpf/verifier.c          |   6 ++
>  net/core/filter.c              | 109 +++++++++++++++++++++--
>  net/core/xdp.c                 |  29 +++++++
>  tools/include/uapi/linux/bpf.h |  25 +++++-
>  9 files changed, 363 insertions(+), 7 deletions(-)
>

[...]

> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index 0cb8ec948816..d7de6c0b32e4 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h
> @@ -3285,6 +3285,23 @@ union bpf_attr {
>   *             Dynamically cast a *sk* pointer to a *udp6_sock* pointer.
>   *     Return
>   *             *sk* if casting is valid, or NULL otherwise.
> + *
> + * int bpf_redirect_map_multi(struct bpf_map *map, struct bpf_map *ex_map, u64 flags)

We've recently converted all return types for helpers from int to
long, please update accordingly. Thanks.

[...]