From owner-freebsd-net@freebsd.org  Tue Sep 22 01:42:31 2015
Return-Path: <owner-freebsd-net@freebsd.org>
Delivered-To: freebsd-net@mailman.ysv.freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org
 [IPv6:2001:1900:2254:206a::19:1])
 by mailman.ysv.freebsd.org (Postfix) with ESMTP id 4E0B1A05EE5
 for <freebsd-net@mailman.ysv.freebsd.org>;
 Tue, 22 Sep 2015 01:42:31 +0000 (UTC)
 (envelope-from yongmincho82@gmail.com)
Received: from mail-io0-x230.google.com (mail-io0-x230.google.com
 [IPv6:2607:f8b0:4001:c06::230])
 (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits))
 (Client CN "smtp.gmail.com",
 Issuer "Google Internet Authority G2" (verified OK))
 by mx1.freebsd.org (Postfix) with ESMTPS id 1B14F1EC0
 for <freebsd-net@freebsd.org>; Tue, 22 Sep 2015 01:42:31 +0000 (UTC)
 (envelope-from yongmincho82@gmail.com)
Received: by ioiz6 with SMTP id z6so2365517ioi.2
 for <freebsd-net@freebsd.org>; Mon, 21 Sep 2015 18:42:30 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113;
 h=mime-version:date:message-id:subject:from:to:content-type;
 bh=83qnlPft7/XkiUmY845JfA8YC9sqOzCP84lVQsuW138=;
 b=EeQGvRkN9ho1ziMz91xSoN3qCJ2+Rgn7mmdq1pF3SDr0Fx3Z9vvH9bG3m+lndzRxZz
 OQaUZTpvmqrfyCi8r7E8J9Q8WHKf+A6no6MiUAA/zbzdx/l7SoQqO8f3MnSyhbK6p8dc
 k++qgnitOaH7Djsx7fmkTlA4EPXJBnXSS6jsURBs6I0NNpYJwcT5CFfdqOtWEJCl8MAP
 GV6joX3p6N/b89UJQh8Ax4r6zyrai8PtR9mMsUrlXzrO3Rd2lrHDWBIAk8NWBZJ/Se8e
 Sun9JlsQKoFOKiADB/jBL490wBcy16f5OpBoFjoyjP5ENxlDt4TWQheaPJ6qz5TFcueM
 0BkA==
MIME-Version: 1.0
X-Received: by 10.107.128.88 with SMTP id b85mr28543999iod.64.1442886150308;
 Mon, 21 Sep 2015 18:42:30 -0700 (PDT)
Received: by 10.64.121.230 with HTTP; Mon, 21 Sep 2015 18:42:30 -0700 (PDT)
Date: Tue, 22 Sep 2015 10:42:30 +0900
Message-ID: <CA+Vsu-+DDTaRjbwxSktJL4vnHTeoLMzQ9ygAhkRy=LULPw8aFQ@mail.gmail.com>
Subject: in case of resetting the t_dupacks in tcp_input.c
From: =?UTF-8?B?7KGw7Jqp66+8?= <yongmincho82@gmail.com>
To: freebsd-net@freebsd.org
Content-Type: text/plain; charset=UTF-8
X-Content-Filtered-By: Mailman/MimeDel 2.1.20
X-BeenThere: freebsd-net@freebsd.org
X-Mailman-Version: 2.1.20
Precedence: list
List-Id: Networking and TCP/IP with FreeBSD <freebsd-net.freebsd.org>
List-Unsubscribe: <https://lists.freebsd.org/mailman/options/freebsd-net>,
 <mailto:freebsd-net-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-net/>
List-Post: <mailto:freebsd-net@freebsd.org>
List-Help: <mailto:freebsd-net-request@freebsd.org?subject=help>
List-Subscribe: <https://lists.freebsd.org/mailman/listinfo/freebsd-net>,
 <mailto:freebsd-net-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Tue, 22 Sep 2015 01:42:31 -0000

Hi,

I have a question that reset a dupack count in tcp stack.
My company's product was tested on freebsd 10.
As far as I know The fast retransmission is triggered when the receiver is
received 3 dup acks.
Why is the t_dupack value reset, if we happen to get data or a window
update along with a duplication ack?

I checked openbsd and netbsd.
The t_dupack is not reset on the netbsd, if it receive ack that
get a window update(changed) along with a duplication ack.
The t_dupack is reset on the openbsd, if it receive ack that
get a window shrink along with a duplication ack.
I don't know why the t_dupack is reset, if to get a window update.
I think Just it is skipped(is not reset),
if we receive the ack that is window update. like netbsd.

could you explain about this?

Thank you in advance for your answers!

Best Regards,
Yongmin