From owner-freebsd-net@FreeBSD.ORG  Mon Dec  2 21:48:08 2013
Return-Path: <owner-freebsd-net@FreeBSD.ORG>
Delivered-To: freebsd-net@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115])
 (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits))
 (No client certificate requested)
 by hub.freebsd.org (Postfix) with ESMTPS id 6DB00D8A;
 Mon,  2 Dec 2013 21:48:08 +0000 (UTC)
Received: from mail-n.franken.de (drew.ipv6.franken.de
 [IPv6:2001:638:a02:a001:20e:cff:fe4a:feaa])
 (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits))
 (No client certificate requested)
 by mx1.freebsd.org (Postfix) with ESMTPS id 2CA481AFD;
 Mon,  2 Dec 2013 21:48:08 +0000 (UTC)
Received: from [192.168.1.102] (p508F2CD2.dip0.t-ipconnect.de [80.143.44.210])
 (Authenticated sender: macmic)
 by mail-n.franken.de (Postfix) with ESMTP id 4729E1C0C0693;
 Mon,  2 Dec 2013 22:48:06 +0100 (CET)
Content-Type: text/plain; charset=us-ascii
Mime-Version: 1.0 (Mac OS X Mail 6.6 \(1510\))
Subject: Re: A small fix for if_em.c, if_igb.c, if_ixgbe.c
From: Michael Tuexen <Michael.Tuexen@lurchi.franken.de>
In-Reply-To: <20131202022338.GA3500@michelle.cdnetworks.com>
Date: Mon, 2 Dec 2013 22:48:07 +0100
Content-Transfer-Encoding: 7bit
Message-Id: <B9593E83-E687-49E9-ABDC-B2DD615180E9@lurchi.franken.de>
References: <521B9C2A-EECC-4412-9F68-2235320EF324@lurchi.franken.de>
 <20131202022338.GA3500@michelle.cdnetworks.com>
To: pyunyh@gmail.com
X-Mailer: Apple Mail (2.1510)
Cc: Jack F Vogel <jfv@freebsd.org>,
 "freebsd-net@freebsd.org list" <freebsd-net@freebsd.org>
X-BeenThere: freebsd-net@freebsd.org
X-Mailman-Version: 2.1.17
Precedence: list
List-Id: Networking and TCP/IP with FreeBSD <freebsd-net.freebsd.org>
List-Unsubscribe: <http://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: <http://lists.freebsd.org/mailman/listinfo/freebsd-net>,
 <mailto:freebsd-net-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Mon, 02 Dec 2013 21:48:08 -0000

On Dec 2, 2013, at 3:23 AM, Yonghyeon PYUN <pyunyh@gmail.com> wrote:

> On Fri, Nov 29, 2013 at 06:24:12PM +0100, Michael Tuexen wrote:
>> Dear all,
>> 
>> ifnet(9) says regarding if_transmit():
>> 
>> Transmit a packet on an interface or queue it if the interface is
>> in use.  This function will return ENOBUFS if the devices software
>> and hardware queues are both full.
>> 
>> The drivers for em, igb and ixgbe might also return an error even
>> in the case the packet was enqueued. The attached patches fix this
>> issue.
> 
> How do you know the packet is successfully enqueued but driver
> returns an error?  Do non-buf-ring-aware drivers also show the same
When debugging the issue, I saw the packet on the wire but the if_transmit()
returning ENOBUFS.
> behavior?
I don't know. I saw this issue with the igb driver.
> 
>> 
>> Any comments?
> 
> I'm afraid the patch you posted ignores any errors(i.e.
> m_defrag(9), bus_dma(9) etc) happened during TX processing.
Correct. I want to make sure that if ENOBUFS is returned, the
packet hasn't made it on the wire. The other errors can occur
for the packet provided to if_transmit() or due to packet
processing of other packets. Am I missing something?

Best regards
Michael
> 
>> 
>> Jack: What do you think? Would you prefer to commit the fix if
>> you think it is acceptable?
>> 
>> Best regards
>> Michael
>