Pino Toscano
2016-Dec-09 13:01 UTC
Re: [Libguestfs] [PATCH v3 2/6] v2v: ova: don't detect compressed disks, read the OVF instead
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@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 inI'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. It could look something like this: let compressed match xpath_string expr with | None -> None | Some "identity" -> Some false | Some "gzip" -> Some true | Some s -> error (f_"unsupported compression in OVF: %s") s in let compressed match compressed with | None -> (* do detection *) | Some c -> c in Thanks, -- Pino Toscano
Tomas Golembiovsky
2016-Dec-10 12:50 UTC
Re: [Libguestfs] [PATCH v3 2/6] v2v: ova: don't detect compressed disks, read the OVF instead
On Fri, 09 Dec 2016 14:01:40 +0100 Pino Toscano <ptoscano@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@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. Also the main reason for doing this check was to be able to skip the detection. The detection would be problematic because we would have to extract the header of each file, perform the check and clean the leftovers. This seems like a lot of hassle to just handle some potentially broken OVAs. Or do we know this really happened in the past? Tomas -- Tomáš Golembiovský <tgolembi@redhat.com>
Pino Toscano
2017-Jan-04 09:12 UTC
Re: [Libguestfs] [PATCH v3 2/6] v2v: ova: don't detect compressed disks, read the OVF instead
On Saturday, 10 December 2016 13:50:08 CET Tomas Golembiovsky wrote:> On Fri, 09 Dec 2016 14:01:40 +0100 > Pino Toscano <ptoscano@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@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).> Also the main reason for doing this check was to be able to skip the > detection. The detection would be problematic because we would have to > extract the header of each file, perform the check and clean the > leftovers.Consdering also your work with patch #5 (which applies only with uncompressed tar OVAs, basically) to read the offset and size of the image file within the tar, we could just read the first 512 bytes of it (like done now), and decide whether to untar+uncompress it or go ahead reading it from the tar as your implementation does. Yes, I agree it adds a bit of complexity.> This seems like a lot of hassle to just handle some > potentially broken OVAs. Or do we know this really happened in the past?The problem in this case is that, since we always extracted the tar and determined the file type of the image without looking at the compression information in the ovf, we have no way to know whether there are such OVAs around. Anyway, I guess it should be better to wait for Rich's opinion on this too, since he has more experience with this. Thanks, -- Pino Toscano
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