netdev - Re: [PATCH net-next v6 0/7] Implement reset reason mechanism to detect

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Message-ID: <CAL+tcoCyuOsNyuuHZG_BBZ5YPNcXHu4v-3Zv4a7JMpLFWwCX5g@mail.gmail.com>
Date: Fri, 19 Apr 2024 06:40:28 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: Jakub Kicinski <kuba@...nel.org>, dsahern@...nel.org, matttbe@...nel.org, 
	martineau@...nel.org, geliang@...nel.org, pabeni@...hat.com, 
	davem@...emloft.net, rostedt@...dmis.org, mhiramat@...nel.org, 
	mathieu.desnoyers@...icios.com, atenart@...nel.org, mptcp@...ts.linux.dev, 
	netdev@...r.kernel.org, linux-trace-kernel@...r.kernel.org, 
	Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next v6 0/7] Implement reset reason mechanism to detect

On Fri, Apr 19, 2024 at 6:29 AM Jason Xing <kerneljasonxing@...il.com> wrote:
>
> On Fri, Apr 19, 2024 at 2:51 AM Eric Dumazet <edumazet@...gle.com> wrote:
> >
> > On Thu, Apr 18, 2024 at 6:24 PM Jason Xing <kerneljasonxing@...il.com> wrote:
> > >
> > > On Thu, Apr 18, 2024 at 11:46 PM Jakub Kicinski <kuba@...nel.org> wrote:
> > > >
> > > > On Thu, 18 Apr 2024 11:30:02 +0800 Jason Xing wrote:
> > > > > I'm not sure why the patch series has been changed to 'Changes
> > > > > Requested', until now I don't think I need to change something.
> > > > >
> > > > > Should I repost this series (keeping the v6 tag) and then wait for
> > > > > more comments?
> > > >
> > > > If Eric doesn't like it - it's not getting merged.
> > >
> > > I'm not a English native speaker. If I understand correctly, it seems
> > > that Eric doesn't object to the patch series. Here is the quotation
> > > [1]:
> > > "If you feel the need to put them in a special group, this is fine by me."
> > >
> > > This rst reason mechanism can cover all the possible reasons for both
> > > TCP and MPTCP. We don't need to reinvent some definitions of reset
> > > reasons which are totally the same as drop reasons. Also, we don't
> > > need to reinvent something to cover MPTCP. If people are willing to
> > > contribute more rst reasons, they can find a good place.
> > >
> > > Reset is one big complicated 'issue' in production. I spent a lot of
> > > time handling all kinds of reset reasons daily. I'm apparently not the
> > > only one. I just want to make admins' lives easier, including me. This
> > > special/separate reason group is important because we can extend it in
> > > the future, which will not get confused.
> > >
> > > I hope it can have a chance to get merged :) Thank you.
> > >
> > > [1]: https://lore.kernel.org/all/CANn89i+aLO_aGYC8dr8dkFyi+6wpzCGrogysvgR8FrfRvaa-Vg@mail.gmail.com/
> > >
> > > Thanks,
> > > Jason
> >
> > My objection was these casts between enums. Especially if hiding with (u32)
>
> So I should explicitly cast it like this:
>     tcp_v4_send_reset(rsk, skb, (enum sk_rst_reason)reason);
> ?
>
> >
> > I see no reason for adding these casts in TCP stack.
>
> Sorry, I don't know why the casts really make you so annoyed. But I
> still think it's not a bad way to handle all the cases for RST.
>
> Supposing not to add a enum sk_rst_reason{}, passing drop reasons only
> works well in TCP for passive rests. For active reset cases (in the
> tcp_send_active_reset()), it's meaningless/confusing to insist on
> reusing the drop reason because I have to add some reset reasons (that
> are only used in RST cases) in the enum skb_drop_reason{}, which is
> really weird, in my view. The same problem exists in how to handle
> MPTCP. So I prefer putting them in a separate group like now. What do
> you think about it, right now?

The description in the previous email may be too long. The key point
is that we're not supporting only for passive resets, right?

Thanks,
Jason