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Date:      Mon, 5 Jan 2015 14:51:11 +0100
From:      Luigi Rizzo <>
To:        =?UTF-8?Q?Olivier_Cochard=2DLabb=C3=A9?= <>
Cc:        "" <>,
Subject:   Re: Why ipfw didn't filter neither log DHCP packets ?
Message-ID:  <>
In-Reply-To: <>
References:  <> <> <> <>

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On Mon, Jan 5, 2015 at 2:41 PM, Olivier Cochard-Labb=C3=A9 <olivier@cochard=

> On Mon, Jan 5, 2015 at 1:28 PM, Willy Offermans <Willy@offermans.rompen.n=
> > wrote:
>> Hello Luigi and FreeBSD friends,
>> I do top posting.
>> So there might be a chance that someting slips through the firewall
>> between the start of the firewall and after the bpf traffic of dhclient.
>> Once the NIC is configured, traffic is possible in principle.
>> Would it be better to start the bpf traffic of dhclient after the firewa=
>> runs. In the latter case, all will or can work as expected. If yes, how
>> should this be set? Should one set
>>  REQUIRE: firewall
>> in /etc/rc.d/dhclient? But there seems no firewall daemon to be present.
>> So
>> I'm not sure how this should work.
> I believe that when Luigi says "that acts before the firewall has a chanc=
> to see the packets", he was not speaking of the RC script order, but abou=
> the FreeBSD network stack layer order.
> Do you confirm Luigi ?
=E2=80=8Bcorrect, it's not a matter of time but of placement
of the modules in the stack.

injection through bpf goes just above the
device driver, so there is no chance to see
bpf-generated packets.
For incoming traffic, bpf sees a copy, so the
original still goes through the stack,
but if you want to see it with ipfw you should
probably enable layer2 firewalling.


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