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Date: Fri, 29 Aug 2003 19:02:06 +0100
From: Bruce M Simpson <bms@spc.org>
To: "Khoa A. To" <takhoa@rice.edu>
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cc: FreeBSD_Net <freebsd-net@FreeBSD.ORG>
Subject: Re: Reversed MAC lookup inside FreeBSD kernel?
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On Fri, Aug 29, 2003 at 11:17:16AM -0500, Khoa A. To wrote:
> I need to get a translation of MAC addresses to IP addresses in the kernel.
> I saw some postings about how to translate MAC to IP in the user level, but
> they seem to require the host to send a packet to that MAC address and some
> other ways that also require the host to actually send some request packets
> out.  All my MAC-IP addresses are already set statically using "arp -s" in
> the ARP table.  When I'm in the kernel, how do I get a hold of the ARP table
> and do some kind of reversed search to get the IP address out?

ARP information is held in the routing table.
Look at the output of netstat -arn and look for routes containing the L
flag (LLINFO). If you need to walk through the routing table, look at how
rtalloc() does it. 'struct rtentry' should be pretty self explanatory...

BMS