From owner-freebsd-net@FreeBSD.ORG Tue Apr 29 16:17:19 2008
Return-Path: <owner-freebsd-net@FreeBSD.ORG>
Delivered-To: freebsd-net@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
by hub.freebsd.org (Postfix) with ESMTP id AB2EC1065686;
Tue, 29 Apr 2008 16:17:19 +0000 (UTC) (envelope-from sam@freebsd.org)
Received: from ebb.errno.com (ebb.errno.com [69.12.149.25])
by mx1.freebsd.org (Postfix) with ESMTP id 5AD478FC19;
Tue, 29 Apr 2008 16:17:19 +0000 (UTC) (envelope-from sam@freebsd.org)
Received: from trouble.errno.com (trouble.errno.com [10.0.0.248])
(authenticated bits=0)
by ebb.errno.com (8.13.6/8.12.6) with ESMTP id m3TGHHLE048179
(version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO);
Tue, 29 Apr 2008 09:17:18 -0700 (PDT) (envelope-from sam@freebsd.org)
Message-ID: <48174A0D.1090302@freebsd.org>
Date: Tue, 29 Apr 2008 09:17:17 -0700
From: Sam Leffler <sam@freebsd.org>
Organization: FreeBSD Project
User-Agent: Thunderbird 2.0.0.9 (X11/20071125)
MIME-Version: 1.0
To: Yehonatan Yossef <yoniy@mellanox.co.il>
References: <6C2C79E72C305246B504CBA17B5500C903E6C3B1@mtlexch01.mtl.com>
In-Reply-To: <6C2C79E72C305246B504CBA17B5500C903E6C3B1@mtlexch01.mtl.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
X-DCC--Metrics: ebb.errno.com; whitelist
Cc: Tom Judge <tom@tomjudge.com>, freebsd-net@freebsd.org,
Liran Liss <liranl@mellanox.co.il>,
freebsd-questions@freebsd.org, Mr Y <yonyossef.lists@gmail.com>
Subject: Re: OS throws away large packets
X-BeenThere: freebsd-net@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Networking and TCP/IP with FreeBSD <freebsd-net.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/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: Tue, 29 Apr 2008 16:17:19 -0000
Yehonatan Yossef wrote:
>
>
>
>> -----Original Message-----
>> From: Tom Judge [mailto:tom@tomjudge.com]
>> Sent: Monday, April 28, 2008 8:21 PM
>> To: Mr Y
>> Cc: freebsd-questions@freebsd.org; freebsd-net@freebsd.org
>> Subject: Re: OS throws away large packets
>>
>> Mr Y wrote:
>>
>>> Hi all,
>>>
>>> I'm trying to implement Large Recieve Offload for an
>>>
>> Ethernet driver
>>
>>> on FreeBSD 6.3, but all my >MTU packets are being thrown by the OS.
>>> I'm using mbuf chains in this imlpementation, each mbuf is
>>>
>> a cluster
>>
>>> of MCLBYTES bytes. They are linked by the m_next pointer.
>>> The first packet being thrown away is 2945 bytes long.
>>>
>> Wireshark shows
>>
>>> the packet that is being passed to the OS is correct.
>>>
>>> Do I need to set some OS parameter to make it recieve mbuf chains?
>>>
>>> Please help.
>>>
>>>
>> Hi Yony,
>>
>> I seem to remember some discussion about this list last year
>> see the following threads:
>>
>>
>>
> http://lists.freebsd.org/pipermail/freebsd-net/2007-September/015250.htm
> l
>
> http://lists.freebsd.org/pipermail/freebsd-net/2007-September/015350.htm
> l
>
> >From my limited reading of these threads just now and possibly bad
> memory. It would seem that the MRU to MTU relationship is defined in
> the nic driver rather than
>
>> enforced further up the stack or at least that seamed to be the case
>>
> with the bce driver.
>
>> Hope this is helpful,
>>
>> Tom
>>
>
> Hi Tom,
>
> >From what I understand these threads are referring to the bce hardware
> configuration (bus configuration) and driver mbuf allocation size. Am I
> correct?
> In my case I'm not trying to receive packets >MTU from the HW, but to
> chain mbuf clusters, each is MCLBYTES long, and pass the mbuf chain to
> the OS.
> Since tcpdump (analyzed by wireshark) catches the packets above the
> driver and reports a good packet (and 2945 bytes long), I assume my
> driver functionality is ok. From what I know tcpdump is supposed to
> immitate the way the stack sees the packet, yet it is discarded.
> My logic says there is an OS parameter handled by the driver (at net
> device init time for example) that will set the OS to receive large mbuf
> chains, or a kernel tcp parameter. Is the tcp stack submitted to the mtu
> somehow?
>
>
I don't see where you've identified what version of the os you're
working with. There's a check in the 802.3 input path on earlier
systems to discard frames >mtu. This was removed not too long ago with
LRO in mind; check the history of sys/net/if_ethersubr.c.
Sam