linux-kernel - Re: DHCP and iptables

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Message-ID: <20091012235013.16174ciovvwpw70g@www.kundendienste.net>
Date:	Mon, 12 Oct 2009 23:50:13 +0200
From:	lkml@...ubi.at
To:	arndbergmann@...glemail.com
Cc:	linux-kernel@...r.kernel.org
Subject: Re: DHCP and iptables

Well, I just looked for "ethernet protocol" and read some things about  
DHCP again.

What's an ethernet protocol?

I also read, that "DHCP is built directly on UDP and IP" (RFC 2131).

It uses Ports (UDP 67/68) and the source address of the DHCP server is  
an IP address.

Could you answer me more in detail, why I get an IP, but block  
everything with iptables?

Sincerely yours Mathias Kub

--------------------
12.10.2009 Mathias Kub <lkml@...ubi.at>

|   Thank you very much for that quick reply.
|
|   Yours Mathias Kub
|
|   --------------------
|   12.10.2009 Arnd Bergmann <arndbergmann@...glemail.com>
|
|   |   On Monday 12 October 2009, lkml@...ubi.at wrote:
|   |   > The last few days I have been wondering about the fact, that I get
|   |   > an IP address via
|   |   > DHCP if all chains at iptables are set to drop and no accept rules
|   |   > set.
|   |   >
|   |   > Does this happen on purpose?
|   |
|   |   DHCP is an ethernet protocol, not an IP protocol, so you have to use
|   |   ebtables instead of iptables to filter it.
|   |
|   |   	Arnd <><
|
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