Stephen Hemminger wrote:
> On Mon, 24 Sep 2007 18:55:38 +0200
> Patrick McHardy wrote:
>
>>Eric W. Biederman wrote:
>>
>>>A really good fix would be to remove the binary side and then to
>>>modify brnf_sysctl_call_tables to allocate a temporary ctl_table and
>>>integer on the stack and only set ctl->data after we have normalized
>>>the written value. But since in practice nothing cares about
>>>the race a better fix probably isn't worth it.
>>
>>
>>I seem to be missing something, the entire brnf_sysctl_call_tables
>>thing looks purely cosmetic to me, wouldn't it be better to simply
>>remove it?
>
>
> I agree, removing seems like a better option. But probably need to go
> through a 3-6mo warning period, since sysctl's are technically an API.


I meant removing brnf_sysctl_call_tables function, not the sysctls
themselves, all it does is change values != 0 to 1. Or did you
actually mean that something in userspace might depend on reading
back the value 1 after writing a value != 0?
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On Tue, 25 Sep 2007 06:07:24 +0200
Patrick McHardy wrote:

> Stephen Hemminger wrote:
> > On Mon, 24 Sep 2007 18:55:38 +0200
> > Patrick McHardy wrote:
> >
> >>Eric W. Biederman wrote:
> >>
> >>>A really good fix would be to remove the binary side and then to
> >>>modify brnf_sysctl_call_tables to allocate a temporary ctl_table
> >>>and integer on the stack and only set ctl->data after we have
> >>>normalized the written value. But since in practice nothing cares
> >>>about the race a better fix probably isn't worth it.
> >>
> >>
> >>I seem to be missing something, the entire brnf_sysctl_call_tables
> >>thing looks purely cosmetic to me, wouldn't it be better to simply
> >>remove it?
> >
> >
> > I agree, removing seems like a better option. But probably need to
> > go through a 3-6mo warning period, since sysctl's are technically
> > an API.
>
>
> I meant removing brnf_sysctl_call_tables function, not the sysctls
> themselves, all it does is change values != 0 to 1. Or did you
> actually mean that something in userspace might depend on reading
> back the value 1 after writing a value != 0?

I was going farther, because don't really see the value of having
a sysctl for this. It seems better to just not load filters if
they aren't going to be used. Having another enable/disable hook
just adds needless complexity.
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Stephen Hemminger wrote:
> On Tue, 25 Sep 2007 06:07:24 +0200
> Patrick McHardy wrote:
>
>
>> I meant removing brnf_sysctl_call_tables function, not the sysctls
>> themselves, all it does is change values != 0 to 1. Or did you
>> actually mean that something in userspace might depend on reading
>> back the value 1 after writing a value != 0?
>>
>
> I was going farther, because don't really see the value of having
> a sysctl for this. It seems better to just not load filters if
> they aren't going to be used. Having another enable/disable hook
> just adds needless complexity.
>

These sysctls control whether bridged packets will be handled
by iptables and friends. The bridge netfilter code always
handles bridged packets, and iptables might be loaded for
different reasons. So I don't see how that would work.

I think it should be specified in the ebtables ruleset, but
the current netfilter infrastructure doesn't allow to do that
cleanly.


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