On June 22, 2015 11:56:24 PM MDT, Ramana Reddy [off-list ref] wrote:

Hi all,

Assume that the client has already ESTABLISHED state with one server,
and I
want to use the
same state of the client with another server with out sending syn and
syn+ack packets with the second server.  I want  to make the second
server
by default ESTABLISHED state. What are the modifications needed in the
linux kernel code and the respective files.
I am not worried about security and attacks at this moment.

I don't know the answer, but given this would be very useful in a failover cluster I assume the code is already there or it is an extremely difficult thing to achieve.

As I think about the sliding window aspect of tcp implementing a transparent socket handoff from one server to another seems rather difficult.

Basically you would need to mirror not only the sockets connection status between the 2 mirrors, but also the in queue data and the sliding window metadata.  (Ie. Data that changes millisecond to millisecond.)

I haven't been a failover cluster expert in a decade or more, but I don't recall any functionality like that ever existing.

Greg

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