On-demand serial port connection

[hickeng]

To support vMotion while:

• not requiring the applianceVM be running
• not requiring a native agent on the ESX host

the only real option we have available is to toggle the connected state of the network serial port.

This will require code in the following components:

• portlayer/interaction - toggle the port on when an attach request comes in
• tether - toggle disconnection of the port if no connection established within timeout (allows for vMotion of VM in the case of appliance failure during attach flow).

To keep attach responsive under normal circumstances we should try having every VM connected as they start, dropping that connection after a couple of minutes. The primary drawback of this will be if starting large numbers of VMs that should immediately be vMotioned - should make this configuration, but with programmatic coupling with rate controls for VM start in VMfork scenarios (where single host start point is more likely),

[mdubya66]

GA feature from SSOD

[caglar10ur]

vmotion disconnects file backed serial devices after the migration hence we are potentially losing data.

[hickeng]

Some additional follow-up issues still outstanding:
#2625
#2626

[mdubya66]

Closing. Other issues are being tracked.