netdev - Re: [PATCH net-next v2 1/1] bridge: return error code when deleting Vlan

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Message-ID: <e4611694-4248-e796-5cca-24f3d07e0e9e@cumulusnetworks.com>
Date:   Thu, 12 Oct 2017 21:12:31 +0300
From:   Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
To:     Roman Mashak <mrv@...atatu.com>, David Ahern <dsahern@...il.com>
Cc:     David Miller <davem@...emloft.net>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next v2 1/1] bridge: return error code when deleting
 Vlan

On 12/10/17 21:07, Roman Mashak wrote:
> On Thu, Oct 12, 2017 at 10:19 AM, David Ahern <dsahern@...il.com> wrote:
>> On 10/12/17 7:51 AM, Roman Mashak wrote:
>>> v2:
>>>  Return err immediately if nbp_vlan_delete() fails (pointed by David Ahern)
>>>
>>> Signed-off-by: Roman Mashak <mrv@...atatu.com>
>>> ---
>>>  net/bridge/br_netlink.c | 8 +++++---
>>>  1 file changed, 5 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
>>> index f0e8268..1efdd48 100644
>>> --- a/net/bridge/br_netlink.c
>>> +++ b/net/bridge/br_netlink.c
>>> @@ -527,11 +527,13 @@ static int br_vlan_info(struct net_bridge *br, struct net_bridge_port *p,
>>>
>>>       case RTM_DELLINK:
>>>               if (p) {
>>> -                     nbp_vlan_delete(p, vinfo->vid);
>>> +                     err = nbp_vlan_delete(p, vinfo->vid);
>>> +                     if (err)
>>> +                             break;
>>
>> I'm not sure a break is the right thing to do. Seems like you leave it
>> in a half configured state.
>>
>>>                       if (vinfo->flags & BRIDGE_VLAN_INFO_MASTER)
>>> -                             br_vlan_delete(p->br, vinfo->vid);
>>> +                             err = br_vlan_delete(p->br, vinfo->vid);
>>>               } else {
>>> -                     br_vlan_delete(br, vinfo->vid);
>>> +                     err = br_vlan_delete(br, vinfo->vid);
>>>               }
>>>               break;
>>>       }
>>>
>>
>> Why do you want to return the error code here? Walking the code paths
>> seems like ENOENT or err from switchdev_port_obj_del are the 2 error
>> possibilities.
> 
> For example, if you attempt to delete a non-existing vlan on a port,
> the current code succeeds and also sends event :
> 
> rtnetlink_rcv_msg
>     rtnl_bridge_dellink
>        br_dellink
>           br_afspec
>              br_vlan_info
> 
> int br_dellink(..)
> {
>   ...
>   err = br_afspec()
>   if (err == 0)
>       br_ifinfo_notify(RTM_NEWLINK, p);
> }
> 
> This is misleading, so a proper errcode has to be produced.
> 

True, but you also change the expected behaviour because now a user can
clear all vlans with one request (1 - 4094), and after the change that
will fail with a partial delete if some vlan was missing.

This has been the behaviour forever and some script might depend on it.
Also IMO, and as David also mentioned, doing a partial delete is not good.