strange network interface problem

[Glenn Johnson]

On Fri, May 09, 2003 at 10:53:15PM -0500, Glenn Johnson wrote:

> This is a weird one but hopefully someone can help.  I have two
> software programs that I frequently use and they each use licensing
> software that depends on the Ethernet interface.  One uses FlexLM and
> the other a node locked scheme.  They are both Linux programs, which
> may be important.  The machine in question is a dual homed machine
> with one xl interface and one fxp interface.  The xl interface is on a
> 192.168.1.0 network and the fxp is on the corporate LAN.  The hostname
> points to the 192.168.1.1 address.  The license keys were generated
> from the MAC address of the xl interface.  This worked fine as of a
> couple of days ago but because of the ffs bug I am not about to back
> my sources back in time.
>
> After updating to a recent -CURRENT,
>
> FreeBSD 5.1-BETA #0: Thu May  8 12:42:08 CDT 2003     root at node1.cluster.srrc.usda.gov:/usr/obj/usr/src/sys/CLUSTER-FW 
>
> the programs in question are getting the interfaces mixed up.  For the
> program that uses the node locked scheme I was able to get another
> license generated and so am okay for that one.  However, the program
> that uses FlexLM is locked to the 192.168.1.0 network.  The problem is
> the software is seeing the dual homed machine on the wrong interface
> and so thinks it is not on the network.

I worked on this remotely and got the problem solved but I am still 
wondering if there is a problem.

It turns out there was an entry for the IP address and its corresponding
hostname of the corporate LAN interface in the /etc/hosts file.  This is
the one on the fxp interface, not the xl interface fir the 192.168.1.0
network.  This was put there by the FreeBSD installer.  I use DNS for
host name resolution and so did not think about it.  I also run NIS on
this machine and so there was a hosts map provided by NIS.  The program
that was having a problem is a Linux program and it uses NIS before DNS,
via its default nsswitch.conf file, and so was picking up the IP address
from the NIS hosts map.

What I do not understand is how the hostname, that was _not_ in the
hosts file, got associated with a different IP address, the one that
was in the hosts file.  I deleted the entry from the /etc/hosts file
and remade the NIS maps and the problem program now gets the correct IP
address.  I could also have edited the Linux nsswitch.conf file.  After
I did this I remembered that I had updated the NIS maps about three days
ago.  No doubt that is when the crossover occurred.  I am going to put
this down as just some strangeness with NIS, DNS, and /etc/hosts going
between the FreeBSD and the Linux layer on the same machine.  It could
have just been a "glitch" because I had not had this happen before.  I
tried to reproduce the problem by putting the entry back in the hosts
file and regenerating the NIS maps but it behaves correctly now.

Thanks.

-- 
Glenn Johnson
glennpj at charter.net