Re: [iptables] Effect of negating multiple source or dest IPs (-s or -d)

["U.Mutlu" <for-gmane@mutluit.com>]

Jan Engelhardt wrote, On 2011-11-08 17:44:
> On Tuesday 2011-11-08 17:19, U.Mutlu wrote:
>
>> sim@netmess.org wrote, On 2011-11-08 17:16:
>>>> What's the effect of this rule on a multihomed box
>>>> (the IPs below are just some examples, not real):
>>>>
>>>>     iptables -A INPUT ! -d 1.2.3.4,2.3.4.5 -p all -j DROP
>>>>
>>>
>>> the newest version of iptables says:
>>>
>>> iptables v1.4.12.1: ! not allowed with multiple source or destination IP
>>> addresses
>>
>> Oh, one wonders why they did so...
>
> Because it leads to a confusing result.
>
> 	! -d a,b,c
>
> could be reasonably interpreted as
>
> 	! -d a&&  ! -d b&&  ! -d c
>
> but because using "," in -s/-d means a simple rule expansion, it
> actually generates an equivalent of
>
> 	! -d a || ! -d b || ! -d c

But OR'ing them IMHO doesn't make much sense, just think about it.
I would suggest to AND them.
Look, a normal rule like this one
   iptables -A INPUT -m state --state NEW -p tcp --dport  80 -j ACCEPT
matches only if every single part of it matches (ie. AND).
Then in our negation case above it should behave similar,
and not switch to OR.