How to avoid TCP 3way handshare

[greg.freemyer at gmail.com]

On June 22, 2015 11:56:24 PM MDT, Ramana Reddy <gtvrreddy at gmail.com> 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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