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Date: Tue, 13 Oct 2009 00:41:40 +0200 From: lkml@...ubi.at To: Arnd Bergmann <arndbergmann@...glemail.com> Cc: linux-kernel@...r.kernel.org Subject: Re: DHCP and iptables Well, but for example ICMP also uses raw sockets and gets blocked if I do not explicit allow it, doesn't it? > On Monday 12 October 2009, 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. > > Ah, right. I confused it with the way that the ancient RARP protocol did > this before DHCP. > > Sorry for the confusion. > >> Could you answer me more in detail, why I get an IP, but block >> everything with iptables? > > The dhcp client opens a raw packet socket at the ethernet device > (if I'm not mistaken again), because there is no IP address assigned > with the netdev at that time. This allows it to send and receive > ethernet frames, bypassing the TCP/IP stack. > > Arnd <>< > -- > 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/ > -- 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/
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