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From:   Eric Dumazet <edumazet@google.com>
Date:   Fri, 27 Jul 2018 20:06:09 -0700
Message-ID: <CANn89iJ=Ad7sVWr3zBmXNSyePJJZaxgnMymN8S7x6fCSvG2jTQ@mail.gmail.com>
Subject: Re: [PATCH net-next 1/2] tcp: call tcp_drop() in tcp collapse
To:     Yafang Shao <laoar.shao@gmail.com>
Cc:     David Miller <davem@davemloft.net>,
        netdev <netdev@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Fri, Jul 27, 2018 at 8:02 PM Yafang Shao <laoar.shao@gmail.com> wrote:
>
> When this SKB is dropped, we should add the counter sk_drops.
> That could help us better tracking this behavior.
>
> Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> ---
>  net/ipv4/tcp_input.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
> index d51fa35..90f83eb 100644
> --- a/net/ipv4/tcp_input.c
> +++ b/net/ipv4/tcp_input.c
> @@ -4802,7 +4802,7 @@ static struct sk_buff *tcp_collapse_one(struct sock *sk, struct sk_buff *skb,
>         else
>                 rb_erase(&skb->rbnode, root);
>
> -       __kfree_skb(skb);
> +       tcp_drop(sk, skb);


Absolutely not.

We do not drop the packet, we have simply lowered the memory overhead.