Re: [net v6 1/2] net: core: set skb useful vars in __bpf_tx_skb

[Alexei Starovoitov <alexei.starovoitov@gmail.com>]

On Thu, Mar 24, 2022 at 6:57 AM <xiangxia.m.yue@gmail.com> wrote:
>
> From: Tonghao Zhang <xiangxia.m.yue@gmail.com>
>
> We may use bpf_redirect to redirect the packets to other
> netdevice (e.g. ifb) in ingress or egress path.
>
> The target netdevice may check the *skb_iif, *redirected
> and *from_ingress. For example, if skb_iif or redirected
> is 0, ifb will drop the packets.
>
> Fixes: a70b506efe89 ("bpf: enforce recursion limit on redirects")
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Jakub Kicinski <kuba@kernel.org>
> Cc: Alexei Starovoitov <ast@kernel.org>
> Cc: Daniel Borkmann <daniel@iogearbox.net>
> Cc: Andrii Nakryiko <andrii@kernel.org>
> Cc: Martin KaFai Lau <kafai@fb.com>
> Cc: Song Liu <songliubraving@fb.com>
> Cc: Yonghong Song <yhs@fb.com>
> Cc: John Fastabend <john.fastabend@gmail.com>
> Cc: KP Singh <kpsingh@kernel.org>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Antoine Tenart <atenart@kernel.org>
> Cc: Alexander Lobakin <alexandr.lobakin@intel.com>
> Cc: Wei Wang <weiwan@google.com>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>
> ---
>  net/core/filter.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/net/core/filter.c b/net/core/filter.c
> index a7044e98765e..c1f45d2e6b0a 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -2107,7 +2107,15 @@ static inline int __bpf_tx_skb(struct net_device *dev, struct sk_buff *skb)
>         }
>
>         skb->dev = dev;
> +       /* The target netdevice (e.g. ifb) may use the:
> +        * - redirected
> +        * - from_ingress
> +        */
> +#ifdef CONFIG_NET_CLS_ACT
> +       skb_set_redirected(skb, skb->tc_at_ingress);
> +#else
>         skb_clear_tstamp(skb);
> +#endif

I thought Daniel Nacked it a couple times already.
Please stop this spam.