From: Eric Dumazet <edumazet@google.com>
To: Mao Wenan <wenan.mao@linux.alibaba.com>
Cc: David Miller <davem@davemloft.net>,
Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
Jakub Kicinski <kuba@kernel.org>, netdev <netdev@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
kernel-janitors@vger.kernel.org
Subject: Re: [PATCH net v2] net: Update window_clamp if SOCK_RCVBUF is set
Date: Mon, 9 Nov 2020 10:56:33 +0100 [thread overview]
Message-ID: <CANn89iKiNdtxaL_yMF6=_8=m001vXVaxvECMGbAiXTYZjfj3oQ@mail.gmail.com> (raw)
In-Reply-To: <1604914417-24578-1-git-send-email-wenan.mao@linux.alibaba.com>
On Mon, Nov 9, 2020 at 10:33 AM Mao Wenan <wenan.mao@linux.alibaba.com> wrote:
>
> When net.ipv4.tcp_syncookies=1 and syn flood is happened,
> cookie_v4_check or cookie_v6_check tries to redo what
> tcp_v4_send_synack or tcp_v6_send_synack did,
> rsk_window_clamp will be changed if SOCK_RCVBUF is set,
> which will make rcv_wscale is different, the client
> still operates with initial window scale and can overshot
> granted window, the client use the initial scale but local
> server use new scale to advertise window value, and session
> work abnormally.
What is not working exactly ?
Sending a 'big wscale' should not really matter, unless perhaps there
is a buggy stack at the remote end ?
>
> Signed-off-by: Mao Wenan <wenan.mao@linux.alibaba.com>
> ---
> v2: fix for ipv6.
> net/ipv4/syncookies.c | 4 ++++
> net/ipv6/syncookies.c | 5 +++++
> 2 files changed, 9 insertions(+)
>
> diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
> index 6ac473b..57ce317 100644
> --- a/net/ipv4/syncookies.c
> +++ b/net/ipv4/syncookies.c
> @@ -427,6 +427,10 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
>
> /* Try to redo what tcp_v4_send_synack did. */
> req->rsk_window_clamp = tp->window_clamp ? :dst_metric(&rt->dst, RTAX_WINDOW);
> + /* limit the window selection if the user enforce a smaller rx buffer */
> + if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
> + (req->rsk_window_clamp > tcp_full_space(sk) || req->rsk_window_clamp == 0))
> + req->rsk_window_clamp = tcp_full_space(sk);
This seems not needed to me.
We call tcp_select_initial_window() with tcp_full_space(sk) passed as
the 2nd parameter.
tcp_full_space(sk) will then apply :
space = min(*window_clamp, space);
Please cook a packetdrill test to demonstrate what you are seeing ?
next prev parent reply other threads:[~2020-11-09 9:56 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-09 9:20 [PATCH] net: Update window_clamp if SOCK_RCVBUF is set Mao Wenan
2020-11-09 9:33 ` [PATCH net v2] " Mao Wenan
2020-11-09 9:56 ` Eric Dumazet [this message]
2020-11-09 10:12 ` Mao Wenan
2020-11-09 10:19 ` Mao Wenan
2020-11-09 11:02 ` Eric Dumazet
2020-11-09 11:41 ` Eric Dumazet
2020-11-09 14:01 ` Eric Dumazet
2020-11-09 16:26 ` Mao Wenan
2020-11-09 16:53 ` [PATCH net v3] " Mao Wenan
2020-11-09 16:59 ` Eric Dumazet
2020-11-09 17:17 ` [PATCH net v4] " Mao Wenan
2020-11-09 17:28 ` Eric Dumazet
2020-11-10 0:16 ` [PATCH net v5] " Mao Wenan
2020-11-10 7:32 ` Eric Dumazet
2020-11-11 1:45 ` Jakub Kicinski
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