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From: Neal Cardwell <ncardwell@google.com>
To: David Miller <davem@davemloft.net>
Cc: phind.uet@gmail.com, yhs@fb.com, edumazet@google.com,
	yoshfuji@linux-ipv6.org, dsahern@kernel.org, kuba@kernel.org,
	ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
	kafai@fb.com, songliubraving@fb.com, john.fastabend@gmail.com,
	kpsingh@kernel.org, ycheng@google.com, yyd@google.com,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	bpf@vger.kernel.org,
	linux-kernel-mentees@lists.linuxfoundation.org,
	syzbot+f1e24a0594d4e3a895d3@syzkaller.appspotmail.com
Subject: Re: [PATCH v4] tcp: fix tcp_init_transfer() to not reset icsk_ca_initialized
Date: Sun, 4 Jul 2021 10:03:08 -0400	[thread overview]
Message-ID: <CADVnQykHuUTw82Fu6XNXJaX-vmep3UN0kvxdwvqcE--2+xAs5A@mail.gmail.com> (raw)
In-Reply-To: <20210703.144945.1327654903412498334.davem@davemloft.net>

On Sat, Jul 3, 2021 at 5:49 PM David Miller <davem@davemloft.net> wrote:
>
> From: Nguyen Dinh Phi <phind.uet@gmail.com>
> Date: Sat,  3 Jul 2021 17:34:17 +0800
>
> > diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
> > index 7d5e59f688de..855ada2be25e 100644
> > --- a/net/ipv4/tcp_input.c
> > +++ b/net/ipv4/tcp_input.c
> > @@ -5922,7 +5922,6 @@ void tcp_init_transfer(struct sock *sk, int bpf_op, struct sk_buff *skb)
> >               tp->snd_cwnd = tcp_init_cwnd(tp, __sk_dst_get(sk));
> >       tp->snd_cwnd_stamp = tcp_jiffies32;
> >
> > -     icsk->icsk_ca_initialized = 0;
> >       bpf_skops_established(sk, bpf_op, skb);
> >       if (!icsk->icsk_ca_initialized)
> >               tcp_init_congestion_control(sk);
>
> Don't you have to make the tcp_init_congestion_control() call unconditional now?

I think we want to keep it conditional, to avoid double-initialization
if the BPF code sets the congestion control algorithm and initializes
it. But that's relatively new and subtle, so it might be nice for this
patch to add a comment about that, since it's touching this part of
the code anyway:

-       icsk->icsk_ca_initialized = 0;
        bpf_skops_established(sk, bpf_op, skb);
+       /* Initialize congestion control unless BPF initialized it already: */
        if (!icsk->icsk_ca_initialized)
                tcp_init_congestion_control(sk);

neal

  reply	other threads:[~2021-07-04 14:03 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-03  9:34 [PATCH v4] tcp: fix tcp_init_transfer() to not reset icsk_ca_initialized Nguyen Dinh Phi
2021-07-03 21:49 ` David Miller
2021-07-04 14:03   ` Neal Cardwell [this message]
     [not found]   ` <CADVnQynxFKthexWRFRGN_9enRt7cmgrNo7mpNOMpNVm_jJpt4w@mail.gmail.com>
2021-07-05 16:34     ` Phi Nguyen

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