Re: [gentoo-security] problem blocking udp packets with iptables

[Matt Drew]

> yes, meanwhile I also found the shorewall howto. I assumed, that the dhcpd
> does not use the normal stack. But I did not understand this behavior,
> because when I look into the RFC regarding bootp/dhcp I found that this
> service is "defined to use the udp protocol"....
>
> thank you for your assistance,
>    Martin
>


You should be able to block this traffic at the Ethernet level using
ebtables with something like this:

ebtables [-t filter] -A INPUT -i eth0 -p ipv4 --ip-protocol 17
--ip-destination-port 67 -j DROP

This drops incoming ethernet traffic to eth0 with an IPv4 protocol of
17 (UDP) destined for IP port 67.

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