[Ns-bugs] [Bug 114] global routing doesn't handle multi-hop layer-2 subnets

[code@nsnam.ece.gatech.edu]

http://www.nsnam.org/bugzilla/show_bug.cgi?id=114





--- Comment #9 from Tom Henderson <tomh at tomh.org>  2008-11-22 23:02:29 EDT ---
(In reply to comment #8)
> > In my experience, bridges do not have IP addresses, but if they do, they are
> > assigned an IP address on the virtual bridge interface (not on the ports
> > themselves) and this is just used for management such as getting SNMP data 
> > out of the bridge; i.e. the bridge is not an IP forwarding device.
> 
> This code only expects IP addresses on the bridge net device interfaces.  The
> bridge ports themselves are expected *not* to have IP addresses.  This allows a
> host to bridge some of its interfaces together without needing a separate
> bridge node.

It seems to me the current code in global-router-interface.cc is handling the
case where the bridge net device has an IP address.  To get to the 
ProcessBroadcastLink() method (line 616), one has to pass the IPv4 interface
check (line 598).  Then, if someone has assigned the bridge device an IP
address, it will proceed to ProcessBridgedBroadcastLink().

> 
> > I would be inclined to disallow the above ProcessBridgedBroadcastLink and
> > perhaps to even sanity check that people are not assigning Ipv4Interfaces to
> > non-virtual devices that are in bridge groups (although I think the latter
> > will be hard to implement and it may be a job of the global routing code 
> > to detect and avoid this).  It makes it less flexible but perhaps less 
> > prone to confusion or configuration error.  Other opinions?
> 
> It would be good to try and detect bridge ports that have IP addresses since
> they are expected not to have them.  I don't really care if you want to
> disallow bridges on nodes with internet stacks.  It seems convenient, and BTW,
> Mircosoft OSes allow it.
> 

I wasn't suggesting that we disallow bridges on nodes with internet stacks;
only that if some of the devices are part of a bridge group that they are not
used as router interfaces also.


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