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Date: Mon, 08 Jan 2007 17:53:54 +0900 (JST)
Message-Id: <20070108.175354.26933985.nagao@iij.ad.jp>
To: freebsd-net@freebsd.org
From: Tadaaki Nagao <nagao@iij.ad.jp>
In-Reply-To: <20070105162022.GA1503@twilight.mbslab.kiae.ru>
References: <459D4D88.2030708@delphij.net> <20070105113442.GH37482@codelabs.ru>
	<20070105162022.GA1503@twilight.mbslab.kiae.ru>
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Cc: delphij@delphij.net, andre@FreeBSD.org
Subject: Re: Different behavior of ping'ing INADDR_BROADCAST?
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Hi,

> > When FBSD is pinging 0xffffffff it does not use the Ethernet broadcasts,
> > when the link-level destination MAC is set to 0xffffffffffff, using some
> > 'known MAC' instead. For the network broadcast address -- it does use
> > link-level broadcasts.

This seems to be the same problem as kern/99558: "FreeBSD 6.1 can't send
packets to INADDR_BROADCAST".

Maybe andre has some thoughts on how to fix this issue? (I'm CC'ing him.)

> > For me the 'known MAC' is that of our border router that serves as
> > the default destination. And my box doing the ARP request for the
> > precisely the IP of the router before pinging 255.255.255.255. You can
> > try to empty your ARP table and then ping 255.255.255.255 watching
> > for the ARP requests and the link-level header of the ICMP packets.
> 
> OK, I've found that in order to ping undirected broadcast address
> one should add some functionality to the 'ping' utility.

It seems to me from the PR above, that before patching `ping', ip_output.c
should receive some sort of fix in handling INADDR_BROADCAST.

-- 
Tadaaki Nagao <nagao@iij.ad.jp>
Applied Research and Development Department, Internet Initiative Japan Inc.