netdev - Re: broken behaviour of TC filter delete

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Message-ID: <85sh33zqkh.fsf@mojatatu.com>
Date:   Fri, 24 Aug 2018 12:18:06 -0400
From:   Roman Mashak <mrv@...atatu.com>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     netdev@...r.kernel.org, jiri@...lanox.com,
        Jamal Hadi Salim <jhs@...atatu.com>
Subject: Re: broken behaviour of TC filter delete

Jiri Pirko <jiri@...nulli.us> writes:

> Thu, Aug 23, 2018 at 11:39:22PM CEST, mrv@...atatu.com wrote:
>>
>>
>>It appears that the following commit changed the behaviour of scenario where a
>>filter is deleted twice:
>>
>>commit f71e0ca4db187af7c44987e9d21e9042c3046070
>>Author: Jiri Pirko <jiri@...lanox.com>
>>Date:   Mon Jul 23 09:23:05 2018 +0200
>>
>>    net: sched: Avoid implicit chain 0 creation
>>
>>
>>Steps to reproduce :
>>
>>1) create dummy device
>>   $ ip link add dev dummy0 type dummy
>>
>>2) create qdisc
>>   $ tc qdisc add dev dummy0 ingress
>>
>>3) create simple u32 filter with action attached
>>   $ tc filter add dev dummy0 parent ffff: protocol ip prio 1 u32 match ip src 10.10.10.1/32 action ok
>>
>>4) list the filter
>>   $ tc filter ls dev dummy0 parent ffff:
>>
>>5) delete the filter with the given protocol and priority
>>   $ tc filter del dev dummy0 parent ffff: protocol ip prio 1
>>
>>6) repeat step 5, this will return -ENOENT ("Error: Filter with specified priority/protocol not found.")
>>However, before the change at step 6 we would get -EINVAL (Error: Cannot find specified filter chain.)
>>and that makes sense.
>
> Wait, this now returns:
> Error: Cannot find specified filter chain.
> So you want it to return -EINVAL (Error: Cannot find specified filter chain.) ?
> How about for other chains?
>

I must've mixed up the return codes and messages while typing the
message.

So _before_ commit f71e0ca4db187af7c44987e9d21e9042c3046070 step 6 would
return -ENOENT with "Error: Filter with specified priority/protocol not
found." and _after_ the commit it returns -EINVAL (Error: Cannot find
specified filter chain.)

ENOENT seems to be more logical to return when there's no more filter to delete.