7:42 a.m.
On Wed, Jan 04, 2017 at 10:12:13AM +0100, Pino Toscano wrote:
On Saturday, 10 December 2016 13:50:08 CET Tomas Golembiovsky wrote:
> On Fri, 09 Dec 2016 14:01:40 +0100
> Pino Toscano <ptoscano(a)redhat.com> wrote:
>
> > On Wednesday, 7 December 2016 17:13:06 CET Tomáš Golembiovský wrote:
> > > The information whether the disk is gzip compressed or not is stored
> > > in the OVF. There is no reason to do the detection.
> > >
> > > Signed-off-by: Tomáš Golembiovský <tgolembi(a)redhat.com>
> > > ---
> > > v2v/input_ova.ml | 28 +++++++++++++++++-----------
> > > v2v/test-v2v-i-ova-gz.ovf | 2 +-
> > > 2 files changed, 18 insertions(+), 12 deletions(-)
> > >
> > > diff --git a/v2v/input_ova.ml b/v2v/input_ova.ml
> > > index b283629..61930f0 100644
> > > --- a/v2v/input_ova.ml
> > > +++ b/v2v/input_ova.ml
> > > @@ -275,6 +275,13 @@ object
> > > | None -> error (f_"no href in ovf:File
(id=%s)") file_ref
> > > | Some s -> s in
> > >
> > > + let expr = sprintf
"/ovf:Envelope/ovf:References/ovf:File[@ovf:id='%s']/@ovf:compression"
file_ref in
> > > + let compressed =
> > > + match xpath_string expr with
> > > + | None | Some "identity" -> false
> > > + | Some "gzip" -> true
> > > + | Some s -> error (f_"unsupported compression in OVF:
%s") s in
> >
> > I'd still do the detection when no ovf:compression attribute is found
> > (that is, the None case above).
> > After all, right now we do the detection for any ova already, so a
> > "broken ova" (with no compression attribute in the ovf but with a
> > compressed image) is already handled by the current code.
>
> I understand what you are trying to achieve here. Unfortunately
> that's not possible, missing attribute means "no compression". As the
> specification says:
>
> When a File element is compressed using gzip, the ovf:compression
> attribute shall be set to “gzip”. Otherwise, the ovf:compression
> attribute shall be set to “identity” or the entire attribute
> omitted.
Yep, I know this -- OTOH, we make extra efforts to support OVAs actually
produced, even with non-standard features (example of this: all the
extra formats -- tar.gz. tar.xz, zip -- instead of the uncompressed tar
container).
I agree we need to try to work with OVAs that exist, which may not
match the specification. Having said that I have no particular
knowledge about this subject.
But I do have a collection of OVAs from may different sources, so I
was able to look at the ovf:compression attribute and see if it
matches the file data.
* I found that in 13 OVF file references, ovf:compression="gzip" was
used. In all of those cases, the file reference was indeed to a
gzip-compressed file.
* I did not find any other use of ovf:compression (neither "identity",
not any other value except for "gzip").
* I did not find any case where there was a compressed disk, but the
ovf:compression attribute was not used.
Therefore I conclude (from a rather small sample, unfortunately), it
does look as if the ovf:compressed attribute is always used in
accordance with the specification, and so Tomas's patch looks OK.
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-p2v converts physical machines to virtual machines. Boot with a
live CD or over the network (PXE) and turn machines into KVM guests.
http://libguestfs.org/virt-v2v