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

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Date:   Tue, 15 Jan 2019 03:08:51 +0000
From:   wangyunjian <wangyunjian@...wei.com>
To:     Nikolay Aleksandrov <nikolay@...ulusnetworks.com>,
        Andrew Lunn <andrew@...n.ch>
CC:     "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



> -----Original Message-----
> From: Nikolay Aleksandrov [mailto:nikolay@...ulusnetworks.com]
> Sent: Monday, January 14, 2019 10:05 PM
> To: wangyunjian <wangyunjian@...wei.com>
> Cc: Andrew Lunn <andrew@...n.ch>; 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

OK, I got your point, will send the v2 later.

Thanks,
	Yunjian