netdev - Re: tipc: MTU discovery

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Message-ID: <CAGUzgdLyqett=78cVYYVWi=ZRE_Z4xgp8tB+jRyEeykcPxRjOQ@mail.gmail.com>
Date:	Tue, 5 Mar 2013 17:22:05 +0100
From:	Sebastian Pöhn <sebastian.poehn@...glemail.com>
To:	Erik Hugne <erik.hugne@...csson.com>
Cc:	netdev@...r.kernel.org, jon.maloy@...csson.com,
	allan.stephens@...driver.com
Subject: Re: tipc: MTU discovery

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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