netdev - Re: [PATCH net] bridge: Fix ethernet header pointer before check skb forwardable

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Message-ID: <fd2a9878-aa75-ba30-26c1-17a447fd6de5@cumulusnetworks.com>
Date:   Mon, 14 Jan 2019 16:04:49 +0200
From:   Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
To:     wangyunjian <wangyunjian@...wei.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        xudingke <xudingke@...wei.com>
Subject: Re: [PATCH net] bridge: Fix ethernet header pointer before check skb
 forwardable

On 14/01/2019 15:51, Andrew Lunn wrote:
> On Mon, Jan 14, 2019 at 04:05:23AM +0000, wangyunjian wrote:
>>> -----Original Message-----
>>> From: Andrew Lunn [mailto:andrew@...n.ch]
>>> Sent: Saturday, January 12, 2019 10:55 PM
>>> To: wangyunjian <wangyunjian@...wei.com>
>>> Cc: netdev@...r.kernel.org; xudingke <xudingke@...wei.com>
>>> Subject: Re: [PATCH net] bridge: Fix ethernet header pointer before check
>>> skb forwardable
>>>
>>> On Sat, Jan 12, 2019 at 06:28:27PM +0800, wangyunjian wrote:
>>>> From: Yunjian Wang <wangyunjian@...wei.com>
>>>>
>>>> The skb header should be set to ethernet header before using
>>>> is_skb_forwardable(including dev->hard_header_len length).
>>>
>>> Hi Yunjian
>>>
>>> I don't see any recent changes in this code. Do you know why this is needed
>>> now, yet it seemed to work before? Do you have a fixes: tag for where it
>>> broke?
>>>
>>> Thanks
>>> 	Andrew
>>
>> Hi Andrew
>>
>> This change is commit f6367b4660dde412f9b7af94763efb1d89cefb74(
>> bridge: use is_skb_forwardable in forward path).
>>
>> I found it when I was testing the vNIC(virtio-net) 's mtu. 
>> I add 2 port on linux bridge br using following commands
>> brctl addbr br
>> brctl addif br eth0
>> brctl addif br eth1
>>
>> The mtu of eth0 and eth1 is 1500，so the expect result is packet larger than
>> 1500 cannot pass through eth0 and eth1.But currently, when I send a 1504
>> packet from eth0 to eth1, the packet passes through success, it means eth1's
>> mtu limit donen't take effect.
> 
> Hi Yunjian
> 
> Thanks for the explanation. Please could you improve the description
> in the patch. Also, add a Fixes tag:
> 
> Fixes: f6367b4660dd ("bridge: use is_skb_forwardable in forward path")
> 
> Thanks
> 	Andrew       
> 

I just noticed this patch thanks to the discussion, please add the
bridge maintainers to the CC list next time as well.

Thanks,
 Nik