Spawn Labs

One of my goals was to avoid maintaining rules state outside of iptables. (Restoring in the case of a shutdown, or synching to a fallback firewall would be more fragile.) To make this work, I used a strategy I called Chain Reference. Rather than inserting rules directly into the default iptables tables (PREROUTING, POSTROUTING, FORWARD, etc), I created chains of rules which could then be easily deleted as a group.

Here, then, are the iptables transactions involved in starting a playsession:

To do this, I set up some number of computers, each running a process with some number of threads (configurable) representing both a MockAppliance (MA) and an associated MockClient (MC). Each thread will be sending and receiving appropriate bi-directional traffic through the MF and back to itself (so, 640 threads).

I track packets during the test, and at the end, evaluate performance based on packets lost, on time, late, etc.

The multi-threading needs to be really efficient to simulate so much traffic.

Clients and appliances must be instantiated and readied before unleashing them all at roughly the same time, using receiversReadyIndicator (a CountdownLatch).

Here is the startup method:

private void test() throws Exception {

// prepare

prepareClients();

prepareAppliances();

sortStreamsAndReceivers();

// start

startReceivers();// spawns a new thread which blocks

receiversReadyIndicator.await();// Wait for all receivers to be ready

startStreams();// blocks main until streams terminate

Thread.sleep(postStreamSleepMs);// wait for final packets to arrive at receivers.

// Test is over once thread continues here

shutdownReceivers();

doReport(false);

}