To fix the various problems noted before, a rewrite of the uml_netjig was done. The rewrite includes a command mode - the result is that the switch controller is now just another I/O from the expect script.
The major thing to note in contrasting this diagram with the previous diagram is that the expect script is now in control. The expect script starts up a copy of the switch emulator (uml_netjig), asks it to create three virtual switches: eastnet, westnet and publicnet.
These are connected to the User-Mode-Linux systems in turn.
Initialization scripts are then run on the two user-mode-linux systems.
At the completion of the initialization, the expect script can then command the uml_netjig to play back captured packets on appropriate interfaces, while recording packets from other interfaces.
In the simplest test case, basic-pluto-01 packets are played on the eastnet, addressed from sunrise (a node on eastnet), to sunset (a node on westnet). The two machines have negotiated a VPN connection using pluto across the public network.
The expect script asks the uml_netjig to signal it when all the packets have been played, and can then shutdown the machines properly.
The are a number of other advantages to this situation:
The startup and shutdown is under the control of the expect script. This means that the systems can be interrogated about the state after the packets have occured.
As the startup/shutdown is no longer contigent on the packet flows - this means that various tests can be done without requiring any packets to flow.
The final advantage of this system is that the expect script is only 209 lines long, of which 106 lines are argument processing. A slightly abridged version is presented below:
spawn -noecho -open [open "|$netjig_prog --cmdproto" w+] newswitch $netjig1 "$arpreply east" newswitch $netjig1 "public" newswitch $netjig1 "$arpreply west" trace variable expect_out(buffer) w log_by_tracing startuml east startuml west loginuml east loginuml west inituml east inituml west record $netjig1 east $recordeast record $netjig1 west $recordwest setupplay $netjig1 east $playeast setupplay $netjig1 west $playwest runuml $netjig1 send -i $umlid(east,spawnid) "^C\r" send -i $umlid(west,spawnid) "^C\r" send -i $umlid(east,spawnid) "halt\r" expect -i $umlid(east,spawnid) eof send -i $umlid(west,spawnid) "halt\r" expect -i $umlid(west,spawnid) eof
![\includegraphics[height=2in,width=3in]{multi_netjig.eps}](img6.png)