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

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Message-ID: <CAML_gOcVWerP2keCiqeTUt5QN-gbqATpTUsK-xPX=RnJoc8OBQ@mail.gmail.com>
Date:   Tue, 27 Sep 2016 14:05:00 +0800
From:   Liping Zhang <zlpnobody@...il.com>
To:     Gao Feng <fgao@...ai8.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 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.

>
> 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