linux-kernel - Re: [PATCH net-next 3/6] net: bridge: break if __br_mdb

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Date:   Thu, 18 May 2017 18:25:11 +0300
From:   Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
To:     Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
        netdev@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, kernel@...oirfairelinux.com,
        "David S. Miller" <davem@...emloft.net>,
        Stephen Hemminger <stephen@...workplumber.org>,
        "moderated list:ETHERNET BRIDGE" <bridge@...ts.linux-foundation.org>
Subject: Re: [PATCH net-next 3/6] net: bridge: break if __br_mdb_del fails

On 5/18/17 6:08 PM, Vivien Didelot wrote:
> Hi Nikolay,
> 
> Nikolay Aleksandrov <nikolay@...ulusnetworks.com> writes:
> 
>>>    			err = __br_mdb_del(br, entry);
>>> -			if (!err)
>>> -				__br_mdb_notify(dev, p, entry, RTM_DELMDB);
>>> +			if (err)
>>> +				break;
>>> +			__br_mdb_notify(dev, p, entry, RTM_DELMDB);
>>>    		}
>>>    	} else {
>>>    		err = __br_mdb_del(br, entry);
>>>
>>
>> This can potentially break user-space scripts that rely on the best-effort
>> behaviour, this is the normal "delete without vid & enabled vlan filtering".
>> You can check the fdb delete code which does the same, this was intentional.
>>
>> You can add an mdb entry without a vid to all vlans, add a vlan and then try
>> to remove it from all vlans where it is present - with this patch obviously
>> that will fail at the new vlan.
> 
> OK good to know. That intention wasn't obvious. I can make __br_mdb_del
> return void instead? What about the rest of the patchset if I do so?
> 
> Thanks,
> 
>          Vivien
> 

If you make it return void we will not be able to return proper error value
when doing a single operation (the else case). About the rest I see only some
minor style issues, I'll comment on the respective patches. Another minor nit is 
using switch() instead of if/else for the message types but that is really up to 
you, I don't mind either way. :-)

Cheers,
  Nik