Re: [Xen-devel] [PATCH v3 07/31] libxl_qmp: Learned to send FD through QMP to QEMU

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

On Wed, Jun 27, 2018 at 03:26:51PM +0100, Ian Jackson wrote:
> Anthony PERARD writes ("[PATCH v3 07/31] libxl_qmp: Learned to send FD 
> through QMP to QEMU"):
> > Adding the ability to send a file descriptor from libxl to QEMU via the
> > QMP interface. This will be use with the "add-fd" QMP command.
> 
> Do you know which byte of the message the fd should be attached to ?

Yes, anywhere before the last byte of the command that is going to use
the fd. QEMU is going to store any fd received until a command is using
it.

We should be able to the the fd, then sent several qmp command, then the
add-fd command, and I think that will work fine.

> What if qemu reads a partial message, discarding the fd, and then
> reads the rest of the message, finding the fd missing ?  Or something.

I don't think QEMU discards fds until a command is using it, or maybe
until a new fd comes in (I did not check this second thought).

-- 
Anthony PERARD

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