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Re: [Nbd] [Qemu-devel] Transforming stdin and stdout pair into a socket

Ciprian Dorin, Craciun wrote:
    Hello all!

    Today I've played around with NBD (Network Block Disk), and
qemu-nbd (a NBD client that exports QEMU disks as NBD's).

    My problem is the following: both NBD kernel module and qemu-nbd
implementation expect to use a socket in order to communicate.
    This means that in order to securely tunnel the connection over
SSH (OpenSSH), I need an intermediary process that creates a socket
and forwards all input / output between this socket and stdin / stdout
(which are in fact pipes received from OpenSSH).

    My question is: can I somehow make the pair of stdin / stdout seem
as a socket to the Linux syscalls (read and write)? (I would have to
make stdin / stdout pair look like a single file descriptor.) (This
would eliminate the intermediate process that just pipes data, and
thus reduce the overhead.)

Something like socat should to do the trick.

For instance, if you have qemu-nbd on localhost:1025:

ssh -l user hostname.com socat stdio tcp:localhost:1025

Alternative, you could just do ssh based port forwarding.  For instance:

ssh -l user -L 1025:localhost:1025 hostname.com

And then connect locally with nbd-client


Anthony Liguori

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