[Ns-bugs] [Bug 948] PointToPointNetDevice does not keep track of destination addresses

[code@nsnam.ece.gatech.edu]

http://www.nsnam.org/bugzilla/show_bug.cgi?id=948





--- Comment #3 from Mathieu Lacage <mathieu.lacage at sophia.inria.fr>  2010-06-23 02:05:53 EDT ---
(In reply to comment #2)
> > PointToPointNetDevice::Send ignores the 'destination' mac address. Upon
> > reception, the destination address given to the receiving layers is the address
> > of the receiver. This breaks code which uses multicast addresses.
> 
> Can you be more specific about what is the problem?  There are no mac addresses
> used in the model; some hardcoded ones are there to satisfy API requirements
> but PppHeader doesn't use them.  Are you trying to achieve layer-2 filtering of
> multicast?

The problem I am seeing here is that even though the device is not
multicast-capable and even though I report so to my linux kernel running on top
of the p2p device, I observe these ipv6 packets beeing sent over p2p:

17:49:09.326344 e6:0c:8c:c9:31:69 > 33:33:00:00:00:02, ethertype IPv6
(0x86dd), length 70: fe80::e40c:8cff:fec9:3169 > ff02::2: ICMP6,
router solicitation, length 16

Being able to convey to the receiver the destination address 33:33:00:00:00:02
is critical to allow the ipv6 neighbour discovery protocol to work because it
filters the packets it receives based on the destination address so, this is
why I put together this patch to preserve the addresses across p2p. (and this
rfc appeared the simplest way to do so)

> I thought that you were complaining that IsMulticast () returns false, but you
> do not change that behavior in your patch.  I don't understand trying to apply
> RFC 3378 here.

I guess that changing IsMulticast to return true would be trivial to do on top
of my patch but I thought that I was not exploiting the multicast capability of
the device. It might be that I was wrong though. More checking needed.

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