linux-kernel - Re: [PATCH net] net: sched: act_mirred: drop skb's dst

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Date:   Mon, 14 Oct 2019 10:57:42 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Zhiyuan Hou <zhiyuan2048@...ux.alibaba.com>
Cc:     Jamal Hadi Salim <jhs@...atatu.com>, Jiri Pirko <jiri@...nulli.us>,
        "David S . Miller" <davem@...emloft.net>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net] net: sched: act_mirred: drop skb's dst_entry in
 ingress redirection

On Sat, Oct 12, 2019 at 12:16 AM Zhiyuan Hou
<zhiyuan2048@...ux.alibaba.com> wrote:
> diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c
> index 9ce073a05414..6108a64c0cd5 100644
> --- a/net/sched/act_mirred.c
> +++ b/net/sched/act_mirred.c
> @@ -18,6 +18,7 @@
>  #include <linux/gfp.h>
>  #include <linux/if_arp.h>
>  #include <net/net_namespace.h>
> +#include <net/dst.h>
>  #include <net/netlink.h>
>  #include <net/pkt_sched.h>
>  #include <net/pkt_cls.h>
> @@ -298,8 +299,10 @@ static int tcf_mirred_act(struct sk_buff *skb, const struct tc_action *a,
>
>         if (!want_ingress)
>                 err = dev_queue_xmit(skb2);
> -       else
> +       else {
> +               skb_dst_drop(skb2);
>                 err = netif_receive_skb(skb2);
> +       }

Good catch!

I don't want to be picky, but it seems this is only needed
when redirecting from egress to ingress, right? That is,
ingress to ingress, or ingress to egress is okay? If not,
please fix all the cases while you are on it?

Thanks.