Subject: Re: [IPROUTE PATCH v2] iproute2: act_ipt fix xtables breakage on older versions.

From: Alexander Duyck <[email-masked]>
Date: Tue, 30 Apr 2013 09:07:36 -0700

On 04/30/2013 05:59 AM, Jamal Hadi Salim wrote:
>
> Hi Alex,
> Theres still some confusion on my part.
>
> On 13-04-29 11:50 AM, Alexander Duyck wrote:
>
>> The first is that xtables_merge_options only has 3 parameters.  It
>> appears
>> this is how this code was originally.
>
> what you are describing above is still not making sense:
>
>  As such for the case where the version
>> is less than 6 I am assuming it would be correct to maintain the
>> original
>> setup that only had 3 parameters being passed instead of 4.
>>
>
> More below, lets just pick one of those:
>
>> @@ -335,8 +338,7 @@ print_ipt(struct action_util *au,FILE * f, struct
>> rtattr *arg)
>>                           m->x6_options,
>>                           &m->option_offset);
>>   #else
>> -        opts = xtables_merge_options(tcipt_globals.orig_opts,
>> -                         tcipt_globals.opts,
>> +        opts = xtables_merge_options(tcipt_globals.opts,
>>                            m->extra_opts,
>>                            &m->option_offset);
>>   #endif
>>
>
>
> Here's the original equivalent change that you are updating:
> -------
> -                       tcipt_globals.opts =
> -                           xtables_merge_options(
>  #if (XTABLES_VERSION_CODE >= 6)
> -                                                
> tcipt_globals.orig_opts,
> +               opts = xtables_options_xfrm(tcipt_globals.orig_opts,
> +                                           tcipt_globals.opts,
> +                                           m->x6_options,
> +                                           &m->option_offset);
> +#else
> +               opts = xtables_merge_options(tcipt_globals.orig_opts,
> +                                            tcipt_globals.opts,
> +                                            m->extra_opts,
> +                                            &m->option_offset);
>  #endif
> -                                                 tcipt_globals.opts,
> -                                                 m->extra_opts,
> -                                                 &m->option_offset);
> ------------------
>
> I see, originally these parameters for xtables_merge_options():
> tcipt_globals.orig_opts  <---- This is what you are trying to kill
> tcipt_globals.opts
> m->extra_opts
> &m->option_offset
>
> Which says there were 4 parameters to begin with....
> Unless you are saying we had it wrong the first time. Pablo?
>
> cheers,
> jamal

Jamal,

It was 4 parameters for (XTABLES_VERSION_CODE >= 6), for versions prior
to that it was only 3 parameters.  Notice the line that is removing
tcipt_globals.orit_opts was wrapped inside the ifdef while the rest of
the function was originally past the endif.  What the original patch did
is make it so that on 1.4.10 and prior we cannot build.

Just take a look at:
https://git.netfilter.org/iptables/tree/include/xtables.h.in?id=v1.4.10#n222

In the git tree it is obvious that xtables_merge_options only takes 3
parameters.  It is not until v1.4.11 which is XTABLES_VERSION_CODE == 6
that we see xtables_merge_options take 4 parameters.

Thanks,

Alex