[CRIU] Simple live migration question

[Pavel Emelyanov]

On 10/10/2012 08:41 PM, hamza zia wrote:
> Hi all,
> 
> I have a simple question regarding live migration. Assuming a
> container has a pool of constantly connected tcp streams, are there
> any ip restrictions on what server I can migrate to without resetting
> those tcp connections?

No. Since container's IP address is migrated with it it doesn't matter
what's on the HN side.

The only tricky thing is how to make sure that intermediate network
routes/forwards packets via new HN. There are two options for OpenVZ
and LXC cases -- routed network to CT and bridged one.

In the former case you should manually (we'll have a script for that,
but now it's not ready yet) call the arpsend to update arp tables. In
the latter case bridges should catch up eventually themselves.

> Probably both servers need to have the same
> public ip behind an NAT, are there any more restrictions as I am
> confused on how the traffic would be routed to the server if the
> private ip is different. I am new to openvz and hence totally
> unfamiliar to live migration. I can understand the plumbings done by
> CRIU to get the tcp connections back in the right state in kernel once
> live migrated but not sure on what plumbings have to be done on the
> outside to make a smooth workflow for not loosing any tcp traffic and
> not resetting the tcp connection. I could set up a custom tcp proxy
> server to manage the transition to a new private ip but not sure if
> this is the right approach to this problem.
> 
> hamza
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