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Date:      Thu, 10 Mar 2016 12:29:23 -0800
From:      Julian Elischer <>
To:        Don Lewis <>,
Subject:   Re: ipwf dummynet vs. kernel NAT and firewall rules
Message-ID:  <>
In-Reply-To: <>
References:  <>

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On 9/03/2016 9:32 AM, Don Lewis wrote:
> I'm trying to add FQ-CoDEL AQM to my FreeBSD 10 firewall box using this
> patch: <>, but I'm
> running into a problem that I think is caused by an interaction between
> in-kernel NAT and dummynet.  I've set up two dummynet pipe/sched/queue
> instances using example 3.3a from this document
> <>; with the
> appropriate bandwidths, but otherwise default tunings to shape both
> inbound and outbound traffic.  My inside network is a /24 and I have an
> external /29 (ext/29) network that I don't want to rate limit.  My
> outside network interface is re0.  I'm using the /etc/rc.firewall
> "simple" firewall configuration.
> The problem that I'm having crops up when I actually try to add the
> firewall rules to select the traffic that I want to rate limit.  The
> first rule in the list is:
> 	100 allow ip from any to any via lo0
> The second rule is numbered 200 and is first anti-spoofing rule.  If
> I add *either* of these two rules, then I'm no longer able to
> communicate between hosts on my internal network and the rest of the
> world:
>    ipfw 110 add queue 1 ip from not ext/29 to any in recv re0
>    ipfw 120 add queue 2 ip from any to not ext/29 out xmit re0
> It seems like the inbound rule should be early in the rule list so that
> any inbound traffic that gets dropped by the firewall rules gets counted
> even if it is dropped by later rules.  It also seems like the outbound
> rule needs to be before any allow rules since an allow rule would skip
> the remaining rules and would not count that traffic.  Unfortunately the
> ipfw documentation doesn't really describe the interaction between
> dummynet, NAT, and other firewall rules.
> Unfortunately this is a live system, so it is difficult to do controlled
> experiments and look at the ipfw counters to see where things might be
> going into the weeds ...

ok so you need to do what I always tell people.. split your rules into 
separate incoming and outgoing rule sets.
so your first rule should be:
   skipto 10000 all from any to any in.

and have separate sets of rules for incoming and outgoing packets.

Then you should always set one_pass to 0  and expect your packets to 
come back to the firewall at the next number.

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