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

Andrii Nakryiko
2020-07-01T05:09:53Z

On Tue, Jun 30, 2020 at 9:21 PM Hangbin Liu <liuhangbin@gmail.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@gmail.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. …