why vimage?

Julian Elischer julian at elischer.org
Sat Mar 1 01:41:11 UTC 2008

Jeremie Le Hen wrote:
> Hi Julian,
> On Tue, Feb 26, 2008 at 08:53:52AM -0800, Julian Elischer wrote:
>>  I can give a very simple example of something you can do trivially on 
>>  vimage:
>>  Make three virtual machines on yhour laptop:
>>  The base machine and two others.
>>  Have the first 'other' machine be assigned an IP address on
>>  your HOME LAN.
>>  have the second virtual machine have an IP adddress on
>>  your WORK LAN.
>>  use the base machine to run encrypted tunnels from where-ever
>>  you happen to be to your work and home.. when you put the laptop to sleep 
>>  (assuming the tcp sessions are quiescent (no keepalives))
>>  then when you wake it up say an hour later.. as soon as the base machine has 
>>  an IP address.. viola, your session on the virtual
>>  machines are still alive.
> On this post [1], Marko states:
> % Each NICs is logically attached to one and only one network stack
> % instance at a time, and it receives data from upper layers and feeds
> % the upper layers with mbufs in exactly the same manner as it does on
> % the standard kernel.  It is the link layer that demultiplexes the
> % incoming traffic to the appropriate stack instance...
> As I understand it, there is only one vimage per interface.  I'm surely
> wrong or the setup you described wouldn't be possible.

physical interfaces can be forked out to several virtual interfaces 
which can be in different virtual machines..
Or the virtual interfaces could be connected to tunnels.

> Any explanation will be welcome :).
> Thanks,
> [1] http://lists.freebsd.org/pipermail/freebsd-current/2008-February/083908.html
> Regards,

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