[libvirt] [Qemu-devel] [PATCH] qemu-ga: add guest-sync-delimited

Daniel P. Berrange berrange at redhat.com
Tue Feb 7 15:09:18 UTC 2012

On Mon, Feb 06, 2012 at 06:07:35PM -0600, Michael Roth wrote:
> guest-sync leaves it as an exercise to the user as to how to reliably
> obtain the response to guest-sync if the client had previously read in a
> partial response (due qemu-ga previously being restarted mid-"sentence"
> due to reboot, forced restart, etc).
> qemu-ga handles this situation on its end by having a client precede
> their guest-sync request with a 0xFF byte (invalid UTF-8), which
> qemu-ga/QEMU JSON parsers will treat as a flush event. Thus we can
> reliably flush the qemu-ga parser state in preparation for receiving
> the guest-sync request.
> guest-sync-delimited provides the same functionality for a client: when
> a guest-sync-delimited is issued, qemu-ga will precede it's response
> with a 0xFF byte that the client can use as an indicator to flush its
> buffer/parser state in preparation for reliably receiving the
> guest-sync-delimited response.
> More information available on the wiki:
> http://wiki.qemu.org/Features/QAPI/GuestAgent#QEMU_Guest_Agent_Protocol
> Signed-off-by: Michael Roth <mdroth at linux.vnet.ibm.com>

This looks good from the libvirt POV.

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