[PATCH] launch: libvirt: Autodetect backing format for drive overlays (RHBZ#1354335).
by Richard W.M. Jones
If the user doesn't specify a format (ie. they want autodetection)
then we must do the file format detection ourselves since libvirt
disabled this and now doesn't work at all on qcow2 overlays that have
no backing_fmt field set.
---
src/launch-libvirt.c | 90 ++++++++++++++++++++++++++++++++--------------------
1 file changed, 56 insertions(+), 34 deletions(-)
diff --git a/src/launch-libvirt.c b/src/launch-libvirt.c
index e8b6e27..3b53a3a 100644
--- a/src/launch-libvirt.c
+++ b/src/launch-libvirt.c
@@ -162,6 +162,50 @@ static int check_bridge_exists (guestfs_h *g, const char *brname);
static void selinux_warning (guestfs_h *g, const char *func, const char *selinux_op, const char *data);
#endif
+/* Return drv->src.format, but if it is NULL, autodetect the format.
+ *
+ * libvirt has disabled the feature of detecting the disk format,
+ * unless the administrator sets allow_disk_format_probing=1 in
+ * qemu.conf. There is no way to detect if this option is set, so we
+ * have to do format detection here using qemu-img and pass that to
+ * libvirt.
+ *
+ * This can still be a security issue, so in most cases it is
+ * recommended the users pass the format to libguestfs which will
+ * faithfully pass that to libvirt and this function won't be used.
+ *
+ * Caller must free the returned string.
+ */
+static char *
+get_source_format_or_autodetect (guestfs_h *g, struct drive *drv)
+{
+ if (drv->src.format)
+ return safe_strdup (g, drv->src.format);
+
+ if (drv->src.protocol == drive_protocol_file) {
+ char *format;
+
+ format = guestfs_disk_format (g, drv->src.u.path);
+ if (!format)
+ return NULL;
+
+ if (STREQ (format, "unknown")) {
+ error (g, _("could not auto-detect the format.\n"
+ "If the format is known, pass the format to libguestfs, eg. using the\n"
+ "'--format' option, or via the optional 'format' argument to 'add-drive'."));
+ return NULL;
+ }
+
+ return format;
+ }
+
+ /* Non-file protocol. */
+ error (g, _("could not auto-detect the format when using a non-file protocol.\n"
+ "If the format is known, pass the format to libguestfs, eg. using the\n"
+ "'--format' option, or via the optional 'format' argument to 'add-drive'."));
+ return NULL;
+}
+
static char *
make_qcow2_overlay (guestfs_h *g, const char *backing_drive,
const char *format)
@@ -169,6 +213,8 @@ make_qcow2_overlay (guestfs_h *g, const char *backing_drive,
char *overlay;
struct guestfs_disk_create_argv optargs;
+ assert (format != NULL);
+
if (guestfs_int_lazy_make_tmpdir (g) == -1)
return NULL;
@@ -176,10 +222,8 @@ make_qcow2_overlay (guestfs_h *g, const char *backing_drive,
optargs.bitmask = GUESTFS_DISK_CREATE_BACKINGFILE_BITMASK;
optargs.backingfile = backing_drive;
- if (format) {
- optargs.bitmask |= GUESTFS_DISK_CREATE_BACKINGFORMAT_BITMASK;
- optargs.backingformat = format;
- }
+ optargs.bitmask |= GUESTFS_DISK_CREATE_BACKINGFORMAT_BITMASK;
+ optargs.backingformat = format;
if (guestfs_disk_create_argv (g, overlay, "qcow2", -1, &optargs) == -1) {
free (overlay);
@@ -196,13 +240,18 @@ create_cow_overlay_libvirt (guestfs_h *g, void *datav, struct drive *drv)
struct backend_libvirt_data *data = datav;
#endif
CLEANUP_FREE char *backing_drive = NULL;
+ CLEANUP_FREE char *format = NULL;
char *overlay;
backing_drive = guestfs_int_drive_source_qemu_param (g, &drv->src);
if (!backing_drive)
return NULL;
- overlay = make_qcow2_overlay (g, backing_drive, drv->src.format);
+ format = get_source_format_or_autodetect (g, drv);
+ if (!format)
+ return NULL;
+
+ overlay = make_qcow2_overlay (g, backing_drive, format);
if (!overlay)
return NULL;
@@ -1480,36 +1529,9 @@ construct_libvirt_xml_disk (guestfs_h *g,
if (construct_libvirt_xml_disk_target (g, xo, drv_index) == -1)
return -1;
- if (drv->src.format)
- format = safe_strdup (g, drv->src.format);
- else if (drv->src.protocol == drive_protocol_file) {
- /* libvirt has disabled the feature of detecting the disk format,
- * unless the administrator sets allow_disk_format_probing=1 in
- * qemu.conf. There is no way to detect if this option is set, so we
- * have to do format detection here using qemu-img and pass that to
- * libvirt.
- *
- * This is still a security issue, so in most cases it is recommended
- * the users pass the format to libguestfs which will faithfully pass
- * that to libvirt and this function won't be used.
- */
- format = guestfs_disk_format (g, drv->src.u.path);
- if (!format)
- return -1;
-
- if (STREQ (format, "unknown")) {
- error (g, _("could not auto-detect the format.\n"
- "If the format is known, pass the format to libguestfs, eg. using the\n"
- "'--format' option, or via the optional 'format' argument to 'add-drive'."));
- return -1;
- }
- }
- else {
- error (g, _("could not auto-detect the format when using a non-file protocol.\n"
- "If the format is known, pass the format to libguestfs, eg. using the\n"
- "'--format' option, or via the optional 'format' argument to 'add-drive'."));
+ format = get_source_format_or_autodetect (g, drv);
+ if (!format)
return -1;
- }
if (construct_libvirt_xml_disk_driver_qemu (g, data, drv, xo, format,
drv->cachemode ? : "writeback",
--
2.7.4
7 years, 9 months
- 1
- 0
Add support for musl libc
by Jakub Jirutka
Hi,
I’m trying to compile libguestfs on Alpine Linux, that uses musl libc (lightweight, fast and simple standards-conformance libc). It fails in the check phase due to missing glibc-style extended printf formatters.
--
checking for register_printf_specifier... no
checking for register_printf_function... no
configure: error: in `/tmp/libguestfs/src/libguestfs-1.32.6’:
configure: error: No support for glibc-style extended printf formatters.
This means you either have a very old glibc (pre-2.0) or you
are using some other libc where this is not supported.
See `config.log’ for more details
--
Could you please add support for musl libc, i.e. avoid using glibc-specific extensions? How often are such non-standard functions used in the libguestfs code-base; can we just patch few occurrences or is it too widespread?
Thanks,
Jakub Jirutka
7 years, 9 months
- 2
- 1