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Date:      Wed, 9 Mar 2016 13:00:58 -0800 (PST)
From:      Don Lewis <truckman@FreeBSD.org>
To:        fjwcash@gmail.com
Cc:        freebsd-ipfw@freebsd.org
Subject:   Re: ipwf dummynet vs. kernel NAT and firewall rules
Message-ID:  <201603092101.u29L0wwH011694@gw.catspoiler.org>

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On  9 Mar, Don Lewis wrote:
> On  9 Mar, Don Lewis wrote:
>> On  9 Mar, Freddie Cash wrote:

>>> 
>>> ?Do you have the sysctl net.inet.ip.fw.one_pass set to 0 or 1?
>> 
>> Aha, I've got it set to 1.
>> 
>>> If set to 1, the a dummynet match ends the trip through the rules, and the
>>> packet never gets to the NAT rules.  Or, if a NAT rule matches, the trip
>>> through the rules ends, and it never get to the dummynet rules.  Depending
>>> on which you have first.
>> 
>> Dummynet is first.
>> 
>>> You'll need to set net.inet.ip.fw.one_pass?=0 in order to re-inject the
>>> packet into the rules after it matches a dummynet or NAT rule.  Or, do the
>>> NAT and dummynet rules on different interfaces to match different traffic.
>> 
>> How do I prevent the re-injected packets from being sent back into
>> dummynet?  My NAT rule looks like it could have the same problem, but
>> that looks fixable.
> 
> I just read the fine man page and is says that after re-injection the
> packet starts with the next rule ... cool!

Ignoring dummynet for a moment since I haven't added those rules back
... DNS lookups break when I set net.inet.ip.fw.one_pass=0.  This
machine is running BIND as a DNS forwarder and I have this rule to
allow DNS lookups in and out:
  pass udp from me to any 53 out via re0 keep-state

If BIND has the results of a lookup cached, then I get the expected
query results from an internal host when I set
net.inet.ip.fw.one_pass=0, but if the results are not cached I get
";; connection timed out; no servers could be reached" when I do a
lookup on an internal host, and running the query on the firewall
machine also does not work.  If BIND has the query cached, I am able
to download from servers on the internet to an internal host, so that
indicates that NAT is functioning, but it shouldn't be involved in DNS
lookups.





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