Hello Paolo,
[EMAIL PROTECTED] wrote:
Hi list!
I'm having some problems using the emulation examples.
I try to use ns-2 as a forwarder: real host A send a ping to real host B,
passing through the simulator, C. After adding the correct route to A and B to
use C as a gateway, I use this script (because the one with ns-2 doesn't work
at all)
# Inside the simulator
#
# node(5)
# / \
# / \
# node(2) node(1)
set ns [new Simulator]
$ns use-scheduler RealTime
set f [open out.tr w]
$ns trace-all $f
set nf [open out.nam w]
$ns namtrace-all $nf
# Create the nodes
set n1 [$ns node]; #reading from real network
set n2 [$ns node]; #writing to the real network
set n5 [$ns node]; #nothing important
# Configure the entry node
set bpf1 [new Network/Pcap/Live]; # Create the bpf
set dev1 [$bpf1 open readonly eth0]; # Open the device
$bpf1 filter icmp and host 192.168.0.3;# put the filter
set tap1 [new Agent/Tap]; # Create the Tap Agent
$tap1 network $bpf1; # Connect bpf to Tap Agent
$ns attach-agent $n1 $tap1; # Attach Tap Agent to the node(1)
# Configure the exit node
set ipnet [new Network/IP]; # Create a Network agent
$ipnet open writeonly
set tap2 [new Agent/Tap]; # Create a Tap Agent
$tap2 network $ipnet; # Connect network agent to tap agent
$ns attach-agent $n2 $tap2; # Attach agent to the node.
# Connect the agents.
$ns simplex-connect $tap1 $tap2
#Just for debug
puts tap1: $tap1
puts tap2: $tap2
puts Node1: $n1
puts Node2: $n2
puts Node5: $n5
puts bpf1: $bpf1
puts ipnet: $ipnet
# Setup connections between the nodes
$ns simplex-link $n1 $n2 10Mb 5ms DropTail
$ns simplex-link $n5 $n2 10Mb 5ms DropTail
$ns at 10 finish
proc finish {} {
global ns f nf
$ns flush-trace
close $f
close $nf
exit 0
}
$ns run
If I run this script, the packets are forwarded, but the simulator begins to
create a very big traffic of dup packet:
...
TapAgent(_o24): sent packet (sz: 60)
TapAgent(_o24): sent packet (sz: 60)
TapAgent(_o24): sent packet (sz: 60)
TapAgent(_o24): sent packet (sz: 60)
TapAgent(_o24): sent packet (sz: 60)
TapAgent(_o24): sent packet (sz: 60)
TapAgent(_o24): sent packet (sz: 60)
TapAgent(_o24): sent packet (sz: 60)
4.835407: Tap(_o21): recvpkt, cc:60
4.835407: Tap(_o21): recvpkt, writing to target: _o13
4.835578: Tap(_o21): recvpkt, cc:60
4.835578: Tap(_o21): recvpkt, writing to target: _o13
4.835698: Tap(_o21): recvpkt, cc:60
4.835698: Tap(_o21): recvpkt, writing to target: _o13
4.835807: Tap(_o21): recvpkt, cc:60
4.835807: Tap(_o21): recvpkt, writing to target: _o13
4.835976: Tap(_o21): recvpkt, cc:60
4.835976: Tap(_o21): recvpkt, writing to target: _o13
4.836086: Tap(_o21): recvpkt, cc:60
...
I really don't understand why.
Is it possible that your
Network/IP
object wites packets back to the eth0 interface? In this case you read a
packet from eth0, pass it through ns-2, then write it back to eth0 with
the $ipnet. But the
Network/Pcap/Live
object reads this packet again, and this results in a endless
duplication cycle.
Another reason for duplication in the real network might be if you have
forgotten to disable the routing on your ns-2 host.
And if I use IPTap for the 2 tap I get:
IPTapAgent(_o21): sendpkt called while in read-only mode!
0.770541: IPTapAgent(_o21): recvpkt, cc:1
If you mean
Network/Pcap/Live
this object can not write packets back to the real network. Under linux
it can only read.
You might be interested in an extension to ns-2-emulation to read/write
packets using linux raw sockets.
http://ivs.cs.uni-magdeburg.de/EuK/forschung/projekte/nse/index.shtml
Thank you very much for any idea/suggestion/tip.
Paolo Carpo
P.S. Sorry for the poor english
Best regards,
Svilen
--
+--+
| M.Sc. Svilen Ivanov |
| Institute for Distributed Systems (IVS) |
| Otto-von-Guericke University - Magdeburg |
| http://ivs.cs.uni-magdeburg.de/~svilen/ |
+--+
