Yep, it's a bug (I came across it a few weeks ago).  Update your
usr/src/sys/netinet/in_var.h from -current.  The INADDR_TO_IA macro has
been fixed.  I hope we'll see a patch/announcement for this soon (it is
obviously a pretty serious bug for a release version).

Rick

Chris Jones wrote:
> 
> This certainly looks like a bug, but I wanted to make sure I wasn't
> missing something obvious before I sent in a pr.
> 
> I have a machine which is acting as a gateway and firewall.
> (Currently, the only ipf rules it's using are the default ones
> generated by the mkfilters perl script, which are pretty minimal.)
> It's configured thusly:
> 
> ne0: flags=8863<UP,BROADCAST,NOTRAILERS,RUNNING,SIMPLEX,MULTICAST> mtu 1500
>         address: 00:80:c8:37:b3:75
>         media: Ethernet manual
>         inet 208.132.31.254 netmask 0xffffff80 broadcast 208.132.31.255
>         inet alias 10.1.1.1 netmask 0xffffff00 broadcast 10.1.1.255
> ne1: flags=8863<UP,BROADCAST,NOTRAILERS,RUNNING,SIMPLEX,MULTICAST> mtu 1500
>         address: 00:80:c8:37:b6:ec
>         media: Ethernet manual
>         inet 208.128.130.5 netmask 0xffffff00 broadcast 208.128.130.255
> lo0: flags=8009<UP,LOOPBACK,MULTICAST> mtu 32976
>         inet 127.0.0.1 netmask 0xff000000
> 
> There's another machine on the ne0 ethernet with an IP of 10.1.1.2,
> which is a gateway into a network at 208.132.31.128/28.
> 
> When a machine in that network sends a packet to www.acceltech.com, my
> firewall responds.  It will respond to a ping or even a TCP packet as
> if they were addressed to it.  However, it routes other traffic just
> fine.  The people behind this firewall claim that there are a few
> other addresses which behave the same way, too.
> 
> The firewall machine in question is NetBSD/i386 1.4.
> 
> Chris
> 
> --
> -----------------------------------------------------cjones@math.montana.edu
> Chris Jones                                          cjones@honors.montana.edu
>            Mad scientist at large                    cjones@nervana.montana.edu
> "Is this going to be a stand-up programming session, sir, or another bug hunt?"

-- 
=========================================================================
Rick Byers                       University of Waterloo, Computer
Science
rickb@iaw.on.ca                              
http://www.iaw.on.ca/rickb/