netdev - Re: tipc: MTU discovery

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Message-ID: <51369A86.6040001@windriver.com>
Date:	Wed, 6 Mar 2013 09:23:18 +0800
From:	Ying Xue <ying.xue@...driver.com>
To:	Sebastian Pöhn <sebastian.poehn@...glemail.com>
CC:	Erik Hugne <erik.hugne@...csson.com>, <netdev@...r.kernel.org>,
	<jon.maloy@...csson.com>, <allan.stephens@...driver.com>
Subject: Re: tipc: MTU discovery

1. Can you dump all TIPC packets for us while TIPC link is established?

2. There has a big gap between 2.6.32 and 3.8, meaning TIPC code is also
made big changes. If you can reproduce the problem on latest kernel
version, please let us know.

Thanks,
Ying

On 03/06/2013 12:22 AM, Sebastian Pöhn wrote:
> I run a DLink DGE-528T (PCI-ID: 1186:4300). Kernel is 2.6.32
> There is a dedicated VLAN sitting over the physical device.
> 
> I even made some similar observations in a VM environment but I think
> this is even a more fragile setup.
> 
> Will install ethtool ...
> 
> On Tue, Mar 5, 2013 at 3:18 PM, Erik Hugne <erik.hugne@...csson.com> wrote:
>> On Tue, Mar 05, 2013 at 01:43:29PM +0100, Sebastian Pöhn wrote:
>>> State Messages larger than 1500 which as used for the MTU negotiation
>>> do not appear in the TIPC stack. But I am able to seen them entering
>>> the correct device.
>>> Because of that no reply with the correct max_packet field set can be
>>> send and the negotiation will always end up at 1.5k.
>>>
>>> So my questions are:
>>> # Is TIPC meant to detect and use the MTU larger than 1.5k?
>> Yes, it should probe and detect MTU's up to ~66k
>>
>>> # Why are the packets not passed to the TIPC stack?
>> TIPC just registers itself as a handler for ETH_P_TIPC through
>> dev_add_pack.
>> If link mtu probes >1.5k are not passed to TIPC, it sounds to me that the
>> NIC driver
>> is to blame. What NIC type and kernel version are you running?
>>
>> Do you see any packet drops in ethtool statistics?
>>
>> //E
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