Re: Segmentation fault (core dumped)

[John Heidemann <johnh@ISI.EDU>]

On Tue, 21 Sep 1999 22:18:51 +0200, "Andr s Cs sz r" wrote: 
>Hi!
>I need a quick solution to the following problem in ns.
>I have a simple topology with CBQ to implement class/priority based queueing. I have TCP agents with traffic generators...
>Everything worked fine but yesterday I found out that it's not enough to have one TCPSink on every target node because every TCP agent needs an own TCPSink.
>My TCp agents are generated in a procedure (which is called randomly to simulate random requests...). With that problem I wanted to generate the TCP Sinks in the same procedure as it is needed. The problem is that I always get the error message in the subject. If I create on every node 60000 TCPSinks before the proc (after creating the topology) and in the procedure I just connect the sinks to the appropriate TCP agent then everything works fine. Of course to generate that much sink is too much time - but they are needed as it is possible (due to random generation of requests) that all these 60000 sinks are needed and not a single one gets freed up - although it hasn't got a great chance but still...
>
>The procedure seems to be all right, the sinks would be created, attached just like the TCP agents.
>I have lines like this in my proc:
>...
>set tcp($source,$sourceagentnumber) [new Agent/TCP]
>$ns attach-agent $n(0) $tcp...
>set tcpsink($destination,$destinationagentnumber) [new Agent/TCP]
>$ns attach-agent ...
>...
>$ns connect $tcp... $tcpsink
>
>the script runs fine and seems to be working: the first packet gets to the target but when it's there I get that error message after the last receive line in the trace file for the packet.
>If I attach the sinks before the before the procedure and in the procedure I just connect them then everything works correctly.
>
>Has anyone an idea what's wrong? The TCL script is all right: ns compiles it and as I mentioned the first packet is received.

Yes, you need one sink per source (you can't multiplex them).

You might look at tcl/ex/many_tcp.tcl as one example (of several) that
dynamically creates sources and sinks.

   -John Heidemann