netdev - Re: [PATCH v2] skmsg: lose offset info in sk_psock_skb

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Date:   Sun, 19 Sep 2021 18:14:05 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Liu Jian <liujian56@...wei.com>
Cc:     John Fastabend <john.fastabend@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jakub Sitnicki <jakub@...udflare.com>,
        Lorenz Bauer <lmb@...udflare.com>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH v2] skmsg: lose offset info in sk_psock_skb_ingress

On Fri, Sep 17, 2021 at 3:05 AM Liu Jian <liujian56@...wei.com> wrote:
> @@ -624,6 +635,13 @@ static void sk_psock_backlog(struct work_struct *work)
>         while ((skb = skb_dequeue(&psock->ingress_skb))) {
>                 len = skb->len;
>                 off = 0;
> +#if IS_ENABLED(CONFIG_BPF_STREAM_PARSER)
> +               if (psock->sk->sk_data_ready == sk_psock_strp_data_ready) {
> +                       stm = strp_msg(skb);
> +                       off = stm->offset;
> +                       len = stm->full_len;
> +               }
> +#endif

How does this work? You are testing psock->sk->sk_data_ready here
but it is already the dest sock here, so, if we redirect a strp_msg() from
strp socket to non-strp socket, this does not work at all?

And this code looks ugly itself. If you want to distinguish this type of
packet from others, you can add a bit in, for example skb->_sk_redir.

Thanks.