Re: [Qemu-devel] Question on unixsocket-based chardevs and vhost-user

["Daniel P. Berrange" <berrange@redhat.com>]

On Wed, Sep 28, 2016 at 05:30:24PM +0000, Felipe Franciosi wrote:
> 
> > On 28 Sep 2016, at 18:03, Felipe Franciosi <felipe@nutanix.com> wrote:
> > 
> > Hi Paolo,
> > 
> >> On 28 Sep 2016, at 17:59, Paolo Bonzini <pbonzini@redhat.com> wrote:
> >> 
> >> On 28/09/2016 18:56, Felipe Franciosi wrote:
> >>> Hi Daniel/Paolo,
> >>> 
> >>> 
> >>> 
> >>> I have a question regarding this commit:
> >>> 
> >>> -------------8<-------------
> >>> Author:     Daniel P. Berrange <berrange@redhat.com>
> >>> AuthorDate: Tue Jan 19 11:14:29 2016 +0000
> >>> Commit:     Paolo Bonzini <pbonzini@redhat.com>
> >>> CommitDate: Tue Jan 26 15:58:11 2016 +0100
> >>> -------------8<-------------
> >>> 
> >>> One of the hunks replace unix_send_msgfds() with io_channel_send_full():
> >>> 
> >>> According to the code (qemu-char.c:968), io_channel_send_full() is just
> >>> ignoring the s->write_msgfds parameter.
> >> 
> >> Hmm, no, it's passing it down:
> >> 
> >>       ret = qio_channel_writev_full(
> >>           ioc, &iov, 1,
> >>           fds, nfds, NULL);
> >> 
> >> See the implementation of qio_channel_socket_writev in io/channel-socket.c.
> > 
> > Ah, so my socket has been plumbed with qio_channel_file_writev() for some reason. That's definitely ignoring the fds. I'll look into why it's not qio_channel_socket_writev().
> 
> Got to the bottom of it. So I was basing myself on this example:
> http://git.qemu.org/?p=qemu.git;a=blob;f=qemu-char.c;h=fb456cec345b10b12a051d44067cce29cb1bdf44;hb=HEAD#l1117
> 
> It says "open a character device to a unix fd" and then uses the QIO File API. Worth checking if that's correct.

That comment is misleading - when it says "unix fd" is really means a POSIX
file descriptor, as distinct from a Win32 file descriptor. It has nothing
todo with UNIX sockets.


Regards,
Daniel
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