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Date:      Wed, 14 Oct 2020 21:20:23 +0200
From:      "Kristof Provost" <kp@FreeBSD.org>
To:        "J David" <j.david.lists@gmail.com>
Cc:        "Andreas Longwitz" <longwitz@incore.de>, freebsd-pf@freebsd.org
Subject:   Re: Packets passed by pf don't make it out?
Message-ID:  <66EA3FE1-598F-4D42-8464-5A3A5C75CD07@FreeBSD.org>
In-Reply-To: <CABXB=RRiksXT8g34jqQx61MaRhOHMzpasmuw4_w=3x4_6EhxXw@mail.gmail.com>
References:  <CABXB=RSO2UDx2=LWx7W5SigYgJcaZ3vUTR0%2BVTDJUx2QezHK1Q@mail.gmail.com> <CABXB=RQE74yggCj6=Zizb2rQjtCi=hg155J0_u=NRK2Q3QHmqg@mail.gmail.com> <5F8336C7.5020709@incore.de> <CABXB=RRdbDYyKfXUtyc9eW-P8eoX2nUb1A1Tn46MHWv5YNjT0g@mail.gmail.com> <5F84CF18.1040905@incore.de> <0072D8A9-6ACE-47D0-AE94-124C4F955735@FreeBSD.org> <CABXB=RRYSn6eXCnkhjNKuzDPTsefEUVKEQ1vZMxYfLBromW4Nw@mail.gmail.com> <F8EE4AB3-FA3F-4B79-A054-7D885141E3F6@FreeBSD.org> <CABXB=RRiksXT8g34jqQx61MaRhOHMzpasmuw4_w=3x4_6EhxXw@mail.gmail.com>

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On 14 Oct 2020, at 21:16, J David wrote:

> On Wed, Oct 14, 2020 at 1:59 PM Kristof Provost <kp@freebsd.org> 
> wrote:
>> There’s good reason to do this, as we have to be able to match 
>> state
>> on both the pre-translation side (when processing LAN -> WAN traffic)
>> and post-translation (WAN -> LAN).
>
> So, basically, pf would need separate states for each pre-redirect
> destination address in order to have the information needed to map the
> reply packet back to the original destination address.
>
> But even if pf did that, the problem does not go away.  It just moves
> to the reply packet coming back with only the post-redirect info.
> That info matches multiple states, leaving pf no way to pick the right
> one.
>
> Is that about right?
>
Pretty much, I think.

I’ve not dug very deep yet, but I wonder if we shouldn’t have to 
teach pf to change the source port to avoid conflicting states in the 
first place.
It’s a non-trivial problem in any case.

Regards,
Kristof



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