netdev - Re: [PATCH next] bonding: pass link-local packets to bonding master also.

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Date:   Tue, 17 Jul 2018 11:55:02 +0200
From:   Michal Soltys <soltys@....info>
To:     Mahesh Bandewar (महेश बंडेवार) <maheshb@...gle.com>,
        Stephen Hemminger <stephen@...workplumber.org>
Cc:     Mahesh Bandewar <mahesh@...dewar.net>,
        Jay Vosburgh <j.vosburgh@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>,
        Veaceslav Falico <vfalico@...il.com>,
        David Miller <davem@...emloft.net>,
        Netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH next] bonding: pass link-local packets to bonding master
 also.

On 07/17/2018 01:57 AM, Mahesh Bandewar (महेश बंडेवार) wrote:
> On Mon, Jul 16, 2018 at 4:33 PM, Stephen Hemminger
> <stephen@...workplumber.org> wrote:
>> On Sun, 15 Jul 2018 18:12:46 -0700
>> Mahesh Bandewar <mahesh@...dewar.net> wrote:
>>
>>> From: Mahesh Bandewar <maheshb@...gle.com>
>>>
>>> Commit b89f04c61efe ("bonding: deliver link-local packets with
>>> skb->dev set to link that packets arrived on") changed the behavior
>>> of how link-local-multicast packets are processed. The change in
>>> the behavior broke some legacy use cases where these packets are
>>> expected to arrive on bonding master device also.
>>>
>>> This patch passes the packet to the stack with the link it arrived
>>> on as well as passes to the bonding-master device to preserve the
>>> legacy use case.
>>>
>>> Reported-by: Michal Soltys <soltys@....info>
>>> Signed-off-by: Mahesh Bandewar <maheshb@...gle.com>
>>
>> Thanks for fixing this.
>>
>> Why not add a Fixes: tag instead of just talking about the commit?
>> That helps the stable maintainers know which versions of the kernel
>> need the patch.

> Well, I thought about it. It's definitely 'related' but not sure it
> 'fixes' in true sense. It definitely fixes the broken legacy case
> though. Is that sufficient to add 'fixes' tag?
> 

It's __not__ broken legacy case. It's normal behavior, starting with 
specification covering LLDP itself (IEEE Std 802.1AB-2016, page 18, '6.8 LLDP 
and Link Aggregation') and ending with a linux bridge actively doing stp via 
in-kernel implementation or with userspace helper (or inactively passing) and 
being blind to bpdus. Not mentioning a very recent kernel feature like 
per-port group_fwd_mask rendered useless in this case.

Unless you also consider attaching a bond to a linux bridge as a broken legacy 
use case. Among other things mentioned in the other thread.

In this context, the comment in code/log message IMHO (of the attached patch), 
should be changed - as it will be just confusing for anyone reading it in the 
future.

(and I'd very much like the fix to hit relevant stable kernels as well)