Re: Process Migration on Linux - Impossible?

Russell Coker - mailing lists account (bofh@snoopy.virtual.net.au)
Thu, 02 Oct 97 07:50:58 +1100


>>>> So you want fault tolerance, not process migration. Don't confuse the
>>>> technique with the result.
>>>
>>> That's an odd thing to say, isn't it? Re-read my first sentence again,
>>>carefully this time. If one can throw a process on another machine at will,
>>>it becomes trivial to checkpoint, yes? Fault tolerance for free.
>>
>> Nope. Not so. You can't migrate a TCP/IP connection between machines even

>I've been wondering about that. It would seem possible if the machine that
>receives the proces (let's call it B) is on the same net with ethernet. B
>would put it's card in promiscuous mode, and listen for packets that are
>meant for the port/ip adress of the application. The machine the process
>comes from (A) would stop responding to packets for that process. As long
>as the router accepts answers coming from the ethernet-adress of B
>(encapsulating perfectly good IP packets that are ok for the rest), it
>would seem that in fact B could
>take over A's network connection. A and B can compare notes ever so often
>to see whose card can best be put in promiscuous mode (maybe even both if
>there's also processes from B on A).

You could even use IPv6 and have a unique IP address for every process
which uses the network and is a candidate for migration (many things such
as NFS client daemons are not candidates for migration...).

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