On Thu, Jan 14, 2021 at 12:55:58PM -0500, Jag Raman wrote:
>
>
> > On Jan 14, 2021, at 11:27 AM, Stefan Hajnoczi <stefa...@redhat.com> wrote:
> >
> > On Thu, Jan 14, 2021 at 10:40:03AM -0500, Jagannathan Raman wrote:
> >> +int qio_channel_readv_full_all(QIOChannel *ioc,
> >> + const struct iovec *iov,
> >> + size_t niov,
> >> + int **fds, size_t *nfds,
> >> + Error **errp)
> >> {
> >> - int ret = qio_channel_readv_all_eof(ioc, iov, niov, errp);
> >> + int ret = qio_channel_readv_full_all_eof(ioc, iov, niov, fds, nfds,
> >> errp);
> >>
> >> if (ret == 0) {
> >> - ret = -1;
> >> error_setg(errp,
> >> "Unexpected end-of-file before all bytes were read");
> >
> > qio_channel_readv_full_all_eof() can read file descriptors but no data
> > and return 0.
> >
> > Here that case is converted into an error and the file descriptors
> > aren't closed, freed, and fds/nfds isn't cleared.
>
> That’s a valid point. I’m wondering if the fix for this case should be in
> qio_channel_readv_full_all_eof(), instead of here.
>
> qio_channel_readv_full_all_eof() should probably return error (-1) if the
> amount of data read does not match iov_size(). If the caller is only expecting
> to read fds, and not any data, it would indicate that by setting iov to NULL
> and/or setting niov=0. If the caller is setting these parameters, it means it
> is
> expecting data.Does that sound good?
The API spec for the existing _eof() methods says:
* The function will wait for all requested data
* to be read, yielding from the current coroutine
* if required.
*
* If end-of-file occurs before any data is read,
* no error is reported; otherwise, if it occurs
* before all requested data has been read, an error
* will be reported.
IOW, return '0' is *only* valid if we've not read anything. I consider
file descriptors to be something.
IOW, qio_channel_readv_full_all_eof must only return 0, if it didn't
read any data and also didn't receive any file descriptors. So yeah,
we must return -1 in the scenario Stefan describes
Regards,
Daniel
--
|: https://berrange.com -o- https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org -o- https://fstop138.berrange.com :|
|: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
