a packet inside a packet inside a packet

[Sjoerd Janssen <s.a.janssen@student.utwente.nl>]

Hi there,

I'm really stuck and could use any input available.

I'll illustrate my problem with the following topology:

node1 ------ node2--------node3-------node4---------node5

Say there is a Tcp sender at node5 transmitting a Packet A.. Upon
entering node4, Packet A is packed into the data field of a newly
created Packet B. Packet B on its turn is also packed into the data
field of another newly created Packet C. (don't ask me the reasons for
this..). Packet C is transmitted to node3. There, Packet B is taken out
and passed to node2 towards node1. At node1, Packet A is taken out (and
delivered to the Tcp sink)..

My problem is that this used to work  but not anymore. Each Packet
contains some of my own headers and as long as I used 'simple' types for
my header fields, e.g:  int seqno_;  everything works fine. When I start
using more complex types for my header fields  , e.g: A seqno_;  where A
is a class, things go wrong...

If I transmit only one Packet from node5 to node1 there's no problem, a
few more will also work. When I start transmitting many more Packets,
e.g. > 5, things get screwed up (segfaults) and it seems that the data
fields of the Packets get corrupted. My guess was that it had something
to do with the way new Packets are allocated (i.e. using the free
store)  but I can't seem to find a problem in there.

Does anybody know whether this can be caused by the fact that I've
included complex types in my header fields, or is my 'packing' approach
wrong in the sense that I have just been lucky that it didn't srew up
before?

I need to use ns-2.1b5 (although I've seen ns-2.1b6 handles data
somewhat differntly... would that be a solution...?)

Regards, Sjoerd.