netdev - Re: [net v6 1/2] net: core: set skb useful vars in __bpf_tx

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Date:   Thu, 24 Mar 2022 08:15:53 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     xiangxia.m.yue@...il.com
Cc:     Network Development <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Antoine Tenart <atenart@...nel.org>,
        Alexander Lobakin <alexandr.lobakin@...el.com>,
        Wei Wang <weiwan@...gle.com>, Arnd Bergmann <arnd@...db.de>
Subject: Re: [net v6 1/2] net: core: set skb useful vars in __bpf_tx_skb

On Thu, Mar 24, 2022 at 6:57 AM <xiangxia.m.yue@...il.com> wrote:
>
> From: Tonghao Zhang <xiangxia.m.yue@...il.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@...emloft.net>
> Cc: Jakub Kicinski <kuba@...nel.org>
> Cc: Alexei Starovoitov <ast@...nel.org>
> Cc: Daniel Borkmann <daniel@...earbox.net>
> Cc: Andrii Nakryiko <andrii@...nel.org>
> Cc: Martin KaFai Lau <kafai@...com>
> Cc: Song Liu <songliubraving@...com>
> Cc: Yonghong Song <yhs@...com>
> Cc: John Fastabend <john.fastabend@...il.com>
> Cc: KP Singh <kpsingh@...nel.org>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Cc: Antoine Tenart <atenart@...nel.org>
> Cc: Alexander Lobakin <alexandr.lobakin@...el.com>
> Cc: Wei Wang <weiwan@...gle.com>
> Cc: Arnd Bergmann <arnd@...db.de>
> Signed-off-by: Tonghao Zhang <xiangxia.m.yue@...il.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.