netdev - Re: [PATCH bpf-next v2 3/4] bpf, sockmap: Fix more uncharged while msg has more

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Date:   Wed, 2 Mar 2022 22:14:38 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Wang Yufen <wangyufen@...wei.com>
Cc:     john.fastabend@...il.com, daniel@...earbox.net,
        jakub@...udflare.com, lmb@...udflare.com, davem@...emloft.net,
        edumazet@...gle.com, yoshfuji@...ux-ipv6.org, dsahern@...nel.org,
        kuba@...nel.org, ast@...nel.org, andrii@...nel.org, kafai@...com,
        songliubraving@...com, yhs@...com, kpsingh@...nel.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH bpf-next v2 3/4] bpf, sockmap: Fix more uncharged while
 msg has more_data

On Wed, Mar 02, 2022 at 10:27:54AM +0800, Wang Yufen wrote:
> In tcp_bpf_send_verdict(), if msg has more data after
> tcp_bpf_sendmsg_redir():
> 
> tcp_bpf_send_verdict()
>  tosend = msg->sg.size  //msg->sg.size = 22220
>  case __SK_REDIRECT:
>   sk_msg_return()  //uncharged msg->sg.size(22220) sk->sk_forward_alloc
>   tcp_bpf_sendmsg_redir() //after tcp_bpf_sendmsg_redir, msg->sg.size=11000
>  goto more_data;
>  tosend = msg->sg.size  //msg->sg.size = 11000
>  case __SK_REDIRECT:
>   sk_msg_return()  //uncharged msg->sg.size(11000) to sk->sk_forward_alloc
> 
> The msg->sg.size(11000) has been uncharged twice, to fix we can charge the
> remaining msg->sg.size before goto more data.

It looks like bpf_exec_tx_verdict() has the same issue.