Date: Thu, 30 Jul 2015 03:34:36 +0800 From: Julian Elischer <julian@freebsd.org> To: bycn82 <bycn82@gmail.com> Cc: freebsd-ipfw <freebsd-ipfw@freebsd.org> Subject: Re: keep-state and in-kernel NAT exposes local ip on external interface Message-ID: <55B92ACC.6090505@freebsd.org> In-Reply-To: <CAC%2BJH2yYuJ92=zZ8%2BrEMh8ofSyPSyGVa6_VdcZ1eKSkmtHrfzQ@mail.gmail.com> References: <1435692039.18121.12.camel@yahoo.com> <5594395D.6050103@FreeBSD.org> <20150728150845.V17327@sola.nimnet.asn.au> <55B7DB52.7010504@FreeBSD.org> <55B8833B.3030205@freebsd.org> <CAC%2BJH2ybB_9W-okDbdvERRq=VE_9cAENj=rJDyky3OAAN--19Q@mail.gmail.com> <55B8DD3D.1030900@freebsd.org> <CAC%2BJH2yYuJ92=zZ8%2BrEMh8ofSyPSyGVa6_VdcZ1eKSkmtHrfzQ@mail.gmail.com>
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On 7/29/15 10:23 PM, bycn82 wrote:
> /Hi,/
> /But I dont understand why you said C->D is already in the dynamic
> table? which line create the dynamic rule for it?/
/it happened on a previous packet at some other rule, for example
30 allow ip from any to D 80 keep-state
/
> /
> /
> /Regards,/
> /bycn82/
>
> On 29 July 2015 at 22:03, Julian Elischer <julian@freebsd.org
> <mailto:julian@freebsd.org>> wrote:
>
> On 7/29/15 5:26 PM, bycn82 wrote:
>> /Hi Julian,/
>> /
>> /
>> /So below are the rules in your example/
>> /
>> /
>> /5 skipto 10 from A to B
>> /
>> /6 skipto 11 from any to any/
>> /10{action} from A to B keep-state/
>> /11{action} from C to D/
>> /
>> /
>> /
>> /
>> /If I remove the "skipto" rules they will become/
>> //
>> /10 {action} from A to B keep-state/
>> /11 {action} from C to D /
>> /
>> /
>> /Correct me if I was wrong, but in my opinion, the rule 5 and
>> 10 are almost the same, so I dont see the benefit by
>> introducing the "skipto" rulees. //IMHO, the "check-state" is
>> to speed-up some selected packets, it will slow-down all other
>> unexpected packets at the same time./
>> /
>> /
> /so because C -D is already in the dynamic table it triggers on
> 10 and never reaches 11.
> see? you fell for it too.
>
> /
>>
>> /Regards,/
>> /bycn82/
>>
>>
>>
>>
>> On 29 July 2015 at 15:39, Julian Elischer <julian@freebsd.org
>> <mailto:julian@freebsd.org>> wrote:
>>
>> On 7/29/15 3:43 AM, Lev Serebryakov wrote:
>>
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA512
>>
>> On 28.07.2015 08:30, Ian Smith wrote:
>>
>> I have global lack of any spare time (and all my
>> FreeBSD activity is
>> only a hobby) for last ~2 months. I see the end of this
>> unfortunate
>> state of affairs in near future and I remember about
>> these examples.
>>
>>
>> there are some simple examples of things this patch addresses..
>> For example in the current code, the following (extemely
>> simplified) set of
>> rules will not do what you would think when you are working
>> with a tcp
>> session from A to B and another from C to D *which has
>> previously been**
>> **accepted with a keep-state at some other point in the
>> ruleset*
>>
>>
>> 10 {any action} from A to B keep-state
>> 20 {any action} tcp from C to D
>>
>> because despite the fact that you are only triggering on a
>> 'setup' packet for A to B, any rule
>> that includes "keep-state" does a "check-state" implicitly.
>> so the packet from C to D never gets past rule 10.
>> the only way you can do this is to prefix rule 10 by
>> something like
>>
>> 5 skipto 10 from A to B
>> 6 skipto 11 from any to any
>>
>> to make sure packets that are not A to B do not hit the
>> hidden 'check-state' .
>>
>> this is a very simple example and yes there are ways to
>> get around it,
>> but it complicates the ruleset and increases errors
>>
>> that reminds me I'd also like to be able to put a "not" at the
>> front of the rule matching to negate the whole test but it
>> doesn't seem to like that.
>>
>>
>>
>>
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>
>
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