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Subject: Re: need help with ipfw nat to pf nat migration
To: Victor Sudakov <vas@mpeks.tomsk.su>, freebsd-net@freebsd.org
References: <20190401033424.GA95019@admin.sibptus.ru>
From: Sergey Akhmatov <sergey@akhmatov.ru>
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Date: Mon, 1 Apr 2019 20:52:47 +0300
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Hello, Victor.

Try using "no nat".

table <limited_nat> {8.8.8.8, ..... }
nat pass on $ext_if from 192.168.3.0/24 to <limited_nat> -> $(ext_if)
no nat on ext_if from 192.168.3.0/24 to any
nat pass on $ext_if from 192.168.0.0/16 to any -> $(ext_if)

On 01/04/2019 06:34, Victor Sudakov wrote:
> Dear Colleagues,
> 
> I'm trying to migrate some firewall rules from ipfw to pf. As pf does
> NAT first and filtering after NAT, I have a problem doing the following:
> 
> 1. All 192.168.0.0/16 addresses should be translated to the real IP of
> the external interface.
> 
> 2. A subset of the 192.168.0.0/16, for example 192.168.3.0/24,
> should have access only to a limited list of addresses in the Internet,
> for example 8.8.8.8 only.
> 
> However, because the "nat" rule has already done its job before
> filtering, I cannot "block on $ext_if from 192.168.3.0/24 to any"
> because the source has already been translated.
> 
> In ipfw I can "deny ip from 192.168.3.0/24 to not 8.8.8.8" before it
> even gets into the nat rule,  but what do I do with pf?
>