From mboxrd@z Thu Jan  1 00:00:00 1970
From: Cong Wang <xiyou.wangcong@gmail.com>
Subject: Re: broken behaviour of TC filter delete
Date: Fri, 24 Aug 2018 11:11:07 -0700
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References: <851sao225x.fsf@mojatatu.com> <20180824081751.GA2931@nanopsycho> <85sh33zqkh.fsf@mojatatu.com>
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Cc: Jiri Pirko <jiri@resnulli.us>,
        Linux Kernel Network Developers <netdev@vger.kernel.org>,
        Jiri Pirko <jiri@mellanox.com>,
        Jamal Hadi Salim <jhs@mojatatu.com>
To: Roman Mashak <mrv@mojatatu.com>
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On Fri, Aug 24, 2018 at 9:21 AM Roman Mashak <mrv@mojatatu.com> wrote:
>
> 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.

Yeah, at least we should keep ENOENT for compatibility.

The bug here is chain 0 is gone after the last filter is gone,
so when you delete the filter again, it treats it as you specify
chain 0 which does not exist, so it hits EINVAL before ENOENT.

I am not sure how to fix this properly.