| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20091013005346.95254r0nd1pw97s4@www.kundendienste.net> Date: Tue, 13 Oct 2009 00:53:46 +0200 From: lkml@...ubi.at To: "H. Peter Anvin" <hpa@...or.com> Cc: arndbergmann@...glemail.com, linux-kernel@...r.kernel.org Subject: Re: DHCP and iptables > On 10/12/2009 02:50 PM, lkml@...ubi.at wrote: >> 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? >> > > The reason is that the DHCP client bypasses the Linux IP stack > completely (because it has special requirements.) > >> | | DHCP is an ethernet protocol, not an IP protocol, so you have to use >> | | ebtables instead of iptables to filter it. >> | | >> | | Arnd <>< > > This is actually incorrect -- DHCP is an IP (UDP, in fact) protocol. It > just has very special requirements (such as being able to use > src=0.0.0.0 dst=255.255.255.255) that aren't needed in normal operation, > so rather than slowing down the in-kernel IP stack it synthesizes raw > packets. > > -hpa > So iptables uses the in-kernel IP stack and because of that fact, it is not able to filter the DHCP packets? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists