ron/miniccc/minimega: improving reconnect

[jcrussell]

Add synchronization bytes to hopefully allow ron and miniccc to reconnect. Write the magic bytes in both directions to flush both sides.

Add redial to the things we do when we start a VM.

[jcrussell]

Tested with a debian VM. If you shutdown the VM and then vm start it, the connection is re-established and you can issue new commands. If you restart the VM (using the OS restart mechanism), the connection is not re-established since minimega doesn't know to call redial. We could add a listener to fix this.

One potentially problematic thing is that the miniccc state is fresh so it doesn't know what the previous command was so it reruns them all.

[mkunz7]

Can you have the agent generate a random number and save it to disk on first run? From then on out make this the agents unique identifier.

[jcrussell]

@mkunz7: is that to prevent miniccc from rerunning commands?

There are some commands that we would want to rerun (e.g. set static IP) and others that we wouldn't (e.g. run setup.bash). It's hard for us to know which those are.

I'm leaning towards letting the user figure this out -- run clear cc commands if all your commands have responses and you're shutting things down for some reason.

[mkunz7]

Yeah, that's my intent. Perhaps we can add a persistence command.

cc persistence true

If persistence is enabled it writes every command it executes to disk. On reconnect it phones home for the list of commands to run, and skips any it has done already.

[djfritz]

Yea the original intent behind having command persist like they do currently is exactly that. If a vm cycles, it can re-ingest all of the past commands.

This all looks good to me.

[djfritz]

LGTM