Re: Q: Extract hardware address from received datagram?

From: Henrik Nordstrom
Date: Mon Aug 15 2005 - 05:14:50 EST

On Sun, 14 Aug 2005, [iso-8859-1] Albrecht Dreß wrote:

Actually, the application I need is something like a dhcp server: an embedded Linux system shall replace a really dumb 16-bit micro with an eth interface. The firmware on the micro provides access to the full header, so when the protocol was designed, noone took care to add the "vital" information to the packet, and as I have to keep compatibility... - you get the picture!

Why is the link layer important at all in the protocol if the packet is an UDP/IP (PF_INET,SOCK_DGRAM) packet? Shouldn't the source IP address be used with an ARP to get the link layer address like what is normally done for IP traffic?

Or is it like in the DHCP case that the source address is not set in the packet, and it is encoded as an IP packet only for practical reasons?

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