netdev - Re: [PATCH nf-next] netfilter: xt_osf: Use explicit member assignment to avoid implicit no padding rule

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Message-ID: <CA+6hz4rCM=PSdzS9LTsVahg=hBHtQEExn86Tn+1HV4XX_LGurA@mail.gmail.com>
Date:   Tue, 27 Sep 2016 14:10:44 +0800
From:   Gao Feng <fgao@...ai8.com>
To:     Liping Zhang <zlpnobody@...il.com>
Cc:     Pablo Neira Ayuso <pablo@...filter.org>,
        Patrick McHardy <kaber@...sh.net>,
        Netfilter Developer Mailing List 
        <netfilter-devel@...r.kernel.org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH nf-next] netfilter: xt_osf: Use explicit member assignment
 to avoid implicit no padding rule

Hi Liping,

On Tue, Sep 27, 2016 at 2:05 PM, Liping Zhang <zlpnobody@...il.com> wrote:
> Hi Feng,
>
> 2016-09-27 14:00 GMT+08:00 Gao Feng <fgao@...ai8.com>:
>> Hi Liping,
>>
>>>
>>> This xt_osf_user_finger{} is carefully designed, no padding now, and
>>> will not be changed in the future, otherwise backward compatibility will
>>> be broken.
>>
>> Yes, there is no padding now. So it is ok to use memcmp now.
>> I am afraid the struct would be modified for other requirements.
>
> This is structure was passed by netlink attribute, so modify it will
> break backward compatibility.

Reasonable.
Thanks Liping.

Regards
Feng

>
>>
>> If it is never changed forever, it is ok certainly.
>>
>>>
>>> I don't think this convert is necessary, actually it is a little ugly, and will
>>> increase the maintenance burden.
>>
>> I just want the codes don't depend any implicit rule.
>>
>> It is a tradeoff. If never change, needn't do any convert.
>> If may change, the memcmp is a little dangerous.
>>
>> Regards
>> Feng