From owner-freebsd-hackers  Fri Dec 29 05:08:45 1995
Return-Path: owner-hackers
Received: (from root@localhost)
          by freefall.freebsd.org (8.7.3/8.7.3) id FAA19539
          for hackers-outgoing; Fri, 29 Dec 1995 05:08:45 -0800 (PST)
Received: from gvr.win.tue.nl (root@gvr.win.tue.nl [131.155.210.19])
          by freefall.freebsd.org (8.7.3/8.7.3) with SMTP id FAA19531
          for <freebsd-hackers@FreeBSD.org>; Fri, 29 Dec 1995 05:08:41 -0800 (PST)
Received: by gvr.win.tue.nl (8.6.10/1.53)
    id OAA28389; Fri, 29 Dec 1995 14:08:33 +0100
From: guido@gvr.win.tue.nl (Guido van Rooij)
Message-Id: <199512291308.OAA28389@gvr.win.tue.nl>
Subject: Re: Freebsd IP alias and BIND
To: guido@gvr.win.tue.nl (Guido van Rooij)
Date: Fri, 29 Dec 1995 14:08:32 +0100 (MET)
Cc: volf@oasis.IAEhv.nl, freebsd-hackers@FreeBSD.org, bind-users@vix.com
In-Reply-To: <199512282037.VAA26377@gvr.win.tue.nl> from "Guido van Rooij" at Dec 28, 95 09:37:22 pm
X-Mailer: ELM [version 2.4 PL24]
Content-Type: text
Sender: owner-hackers@FreeBSD.org
Precedence: bulk

> I think this is caused by the netmask of the alias being set to 0xffffffff.
> When it is set to another netmask, named behaves correctly. I'll dive further
> into it.
> 

It turns out to be a bug in the FreeBSd kernel. FreeBSD wants ip aliases
on the same subnet to be set with an all one netmask. This makes
udp_input process the packet as if it is a broadcast packet, therefore
delivering it multiple times. The reason is that in_broadcast() thinks
the destination adres is a broadcast adres (when a packet is send to
the alias).

-Guido