v2v: ova: check libvirt version before OVA import

Libvirt < 3.1.0 lacks enough support for json: pseudo-URLs. Notably it
does not allow use of "raw" driver that we need.

Signed-off-by: Tomáš Golembiovský <tgolembi@redhat.com>

v2v/Makefile.am

@@ -63,10 +63,10 @@ SOURCES_MLI = \
 SOURCES_ML = \
 	types.ml \
 	uefi.ml \
+	domainxml.ml \
 	utils.ml \
 	name_from_disk.ml \
 	vCenter.ml \
-	domainxml.ml \
 	DOM.ml \
 	changeuid.ml \
 	OVF.ml \
@@ -175,9 +175,9 @@ virt_v2v_copy_to_local_CFLAGS = \
 
 COPY_TO_LOCAL_BOBJECTS = \
 	uefi.cmo \
+	domainxml.cmo \
 	utils.cmo \
 	vCenter.cmo \
-	domainxml.cmo \
 	copy_to_local.cmo
 COPY_TO_LOCAL_XOBJECTS = $(COPY_TO_LOCAL_BOBJECTS:.cmo=.cmx)
 
@@ -402,6 +402,7 @@ endif
 v2v_unit_tests_BOBJECTS = \
 	types.cmo \
 	uefi.cmo \
+	domainxml.cmo \
 	utils.cmo \
 	DOM.cmo \
 	OVF.cmo \

v2v/input_ova.ml

@@ -91,7 +91,8 @@ object
         match detect_file_type ova with
         | `Tar ->
           (* Normal ovas are tar file (not compressed). *)
-          if qemu_img_supports_offset_and_size () then (
+          if qemu_img_supports_offset_and_size () &&
+              libvirt_supports_json_raw_driver () then (
             (* In newer QEMU we don't have to extract everything.
              * We can access disks inside the tar archive directly.
              *)

v2v/utils.ml

@@ -119,6 +119,20 @@ let qemu_img_supports_offset_and_size () =
   debug "qemu-img supports \"offset\" and \"size\" in json URLs: %b" r;
   r
 
+(* Libvirt < 3.1.0 lacks enough support for json: pseudo-URLs we use as backing
+ * files, when importing OVAs directly without extracting them first.
+ *)
+let libvirt_supports_json_raw_driver () =
+  let libguestfs_backend = (open_guestfs ())#get_backend () in
+  let libguestfs_backend, _ = String.split ":" libguestfs_backend in
+  if libguestfs_backend = "libvirt" then (
+    let sup = Domainxml.libvirt_get_version () >= (3, 1, 0) in
+    debug "libvirt supports  \"raw\" driver in json URL: %B" sup;
+    sup
+  )
+  else
+    true
+
 let find_file_in_tar tar filename =
   let lines = external_command (sprintf "tar tRvf %s" (Filename.quote tar)) in
   let rec loop lines =

v2v/utils.mli

@@ -55,6 +55,11 @@ val qemu_img_supports_offset_and_size : unit -> bool
 (** Return true iff [qemu-img] supports the ["offset"] and ["size"]
     parameters to open a subset of a file. *)
 
+val libvirt_supports_json_raw_driver : unit -> bool
+(** Return true if [libvirt] supports ["json:"] pseudo-URLs and accepts the
+    ["raw"] driver. Function also returns true if [libvirt] backend is not
+    used. *)
+
 val find_file_in_tar : string -> string -> int64 * int64
 (** [find_file_in_tar tar filename] looks up file in [tar] archive and returns
     a tuple containing at which byte it starts and how long the file is.