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

From: Jamal Hadi Salim <jhs@mojatatu.com>
To: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>,
	Roman Mashak <mrv@mojatatu.com>, David Ahern <dsahern@gmail.com>
Cc: David Miller <davem@davemloft.net>,
	Stephen Hemminger <stephen@networkplumber.org>,
	Linux Kernel Network Developers <netdev@vger.kernel.org>
Subject: Re: [PATCH net-next v2 1/1] bridge: return error code when deleting Vlan
Date: Thu, 12 Oct 2017 22:03:30 -0400	[thread overview]
Message-ID: <64292550-f043-c1f7-5b0e-004288832887@mojatatu.com> (raw)
In-Reply-To: <e4611694-4248-e796-5cca-24f3d07e0e9e@cumulusnetworks.com>

On 17-10-12 02:12 PM, Nikolay Aleksandrov wrote:
> On 12/10/17 21:07, Roman Mashak wrote:

>> 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.
> 

The issue is more subtle (per Roman above):
Try to delete a vlan (that doesnt  exist).
1) It says "success".
2) Worse: Another process listening (bridge monitor?) gets an _event_
  that  the vlan has been deleted (when it never existed in the first
  place).

> 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.
>

I think this is a bug (especially the event part).

cheers,
jamal