Deciding if a user string represents a local file instead of a
network path is an operation worth exposing directly, particularly
since the next patch will be removing a redundant variable that
was caching the information.

* src/util/virstoragefile.h (virStorageIsFile): New declaration.
* src/util/virstoragefile.c (virBackingStoreIsFile): Rename...
(virStorageIsFile): ...export, and allow NULL input.
(virStorageFileGetMetadataInternal)
(virStorageFileGetMetadataRecurse, virStorageFileGetMetadata):
Update callers.
* src/conf/domain_conf.c (virDomainDiskDefForeachPath): Use it.
* src/storage/storage_backend_fs.c (virStorageBackendProbeTarget):
Likewise.
* src/libvirt_private.syms (virstoragefile.h): Export function.
Signed-off-by: NEric Blake <eblake@redhat.com>

So far, my work has been merely preserving the status quo of
backing file analysis.  But this patch starts to tread in the
territory of making the backing chain code more powerful - we
will eventually support network storage containing non-raw
formats.  Here, we expose metadata information about a network
backing store, even if that information is still hardcoded to
a raw format for now.

* src/util/virstoragefile.c (virStorageFileGetMetadataRecurse):
Also populate struct for non-file backing.
(virStorageFileGetMetadata, virStorageFileGetMetadatainternal):
Recognize non-file top image.
(virFindBackingFile): Add comment.
(virStorageFileChainGetBroken): Adjust comment, ensure output
is set.
* tests/virstoragetest.c (mymain): Update test to reflect it.
Signed-off-by: NEric Blake <eblake@redhat.com>

The current use of virStorageFileMetadata is awkward; to learn
some of the information about a child node, you have to read
fields in the parent node.  This does not lend itself well to
modifying backing chains (whether inserting a new node in the
chain, or consolidating existing nodes); better would be to
learn about a child node directly in that node.  This patch
sets up some new fields which contain redundant information,
although not necessarily in the final desired state for the
new fields (see the next patch for actual tests of what is there
now).  Then later patches will do any refactoring necessary to
get the fields to their desired states, and update clients to
get the information from the new fields, so we can finally
delete the fields that are tracking information about the wrong
node.

More concretely, compare these three example backing chains:

good <- one
missing <- two
gluster://server/vol/img <- three

Pre-patch, querying the chains gives:
{ .backingStore = "/path/to/good",
  .backingStoreRaw = "good",
  .backingStoreIsFile = true,
  .backingStoreFormat = VIR_STORAGE_FILE_RAW,
  .backingMeta = {
    .backingStore = NULL,
    .backingStoreRaw = NULL,
    .backingStoreIsFile = false,
    .backingMeta = NULL,
  }
}
{ .backingStore = NULL,
  .backingStoreRaw = "missing",
  .backingStoreIsFile = false,
  .backingStoreFormat = VIR_STORAGE_FILE_NONE,
  .backingMeta = NULL,
}
{ .backingStore = "gluster://server/vol/img",
  .backingStoreRaw = NULL,
  .backingStoreIsFile = false,
  .backingStoreFormat = VIR_STORAGE_FILE_RAW,
  .backingMeta = NULL,
}

Deciding whether to ignore a missing backing file (as in virsh
vol-dumpxml) or report an error (as in security manager sVirt
labeling) requires reading multiple fields.  Plus, the format
is hard-coded to treat all network protocols as end-of-the-chain,
as if they were raw.  By the end of this patch series, the goal
is to instead represent these three situations as:

{ .path = "one",
  .canonPath = "/path/to/one",
  .type = VIR_STORAGE_TYPE_FILE,
  .format = VIR_STORAGE_FILE_QCOW2,
  .backingStoreRaw = "good",
  .backingMeta = {
    .path = "good",
    .canonPath = "/path/to/good",
    .type = VIR_STORAGE_TYPE_FILE,
    .format = VIR_STORAGE_FILE_RAW,
    .backingStoreRaw = NULL,
    .backingMeta = NULL,
  }
}
{ .path = "two",
  .canonPath = "/path/to/two",
  .type = VIR_STORAGE_TYPE_FILE,
  .format = VIR_STORAGE_FILE_QCOW2,
  .backingStoreRaw = "missing",
  .backingMeta = NULL,
}
{ .path = "three",
  .canonPath = "/path/to/three",
  .type = VIR_STORAGE_TYPE_FILE,
  .format = VIR_STORAGE_FILE_QCOW2,
  .backingStoreRaw = "gluster://server/vol/img",
  .backingMeta = {
    .path = "gluster://server/vol/img",
    .canonPath = "gluster://server/vol/img",
    .type = VIR_STORAGE_TYPE_NETWORK,
    .format = VIR_STORAGE_FILE_RAW,
    .backingStoreRaw = NULL,
    .backingMeta = NULL,
  }
}

or, for the second file, maybe also allowing:
{ .path = "two",
  .canonPath = "/path/to/two",
  .type = VIR_STORAGE_TYPE_FILE,
  .format = VIR_STORAGE_FILE_QCOW2,
  .backingStoreRaw = "missing",
  .backingMeta = {
    .path = "missing",
    .canonPath = NULL,
    .type = VIR_STORAGE_TYPE_NONE,
    .format = VIR_STORAGE_FILE_NONE,
    .backingStoreRaw = NULL,
    .backingMeta = NULL,
  }
}

* src/util/virstoragefile.h (_virStorageFileMetadata): Add
path, canonPath, relDir, type, and format fields.  Reorder
existing fields, and add lots of comments.
* src/util/virstoragefile.c (virStorageFileFreeMetadata): Clean
new fields.
(virStorageFileGetMetadataInternal)
(virStorageFileGetMetadataFromFDInternal): Start populating new
fields.
Signed-off-by: NEric Blake <eblake@redhat.com>

Right now, we are allocating virStorageFileMetadata near the bottom
of the callchain, only after we have identified that we are visiting
a file (and not a network resource).  I'm hoping to eventually
support parsing the backing chain from XML, where the backing chain
crawl then validates what was parsed rather than allocating a fresh
structure.  Likewise, I'm working towards a setup where we have a
backing element even for networks.  Both of these use cases are
easier to code if the allocation is hoisted earlier.

* src/util/virstoragefile.c (virStorageFileGetMetadataInternal)
(virStorageFileGetMetadataFromFDInternal): Change signature.
(virStorageFileGetMetadataFromBuf)
(virStorageFileGetMetadataRecurse, virStorageFileGetMetadata):
Update callers.
Signed-off-by: NEric Blake <eblake@redhat.com>

The previous patch started a separation of error messages
reported against the user-specified name, vs. tracking the
canonical path that was actually opened.  This patch extends
that notion, by hoisting directory detection up front, passing
the canonical path through the entire call chain, and
simplifying lower-level functions that can now assume that
a canonical path and directory have been supplied.

* src/util/virstoragefile.c
(virStorageFileGetMetadataFromFDInternal)
(virStorageFileGetMetadataInternal): Add parameter, require
directory.
(virFindBackingFile): Require directory.
(virStorageFileGetMetadataFromFD): Pass canonical path.
(virStorageFileGetMetadataFromBuf): Likewise.
(virStorageFileGetMetadata): Determine initial directory.
Signed-off-by: NEric Blake <eblake@redhat.com>

Now that the storage source definition is uniform convert the helpers to
retrieve the actual storage type to a single one.

While trying to refactor the backing file chain, I noticed that
if you have a self-referential qcow2 file via a relative name:

qemu-img create -f qcow2 loop 10M
qemu-img rebase -u -f qcow2 -F qcow2 -b loop loop

then libvirt was creating a chain 2 deep before realizing it
had hit a loop; furthermore, virStorageFileChainCheckBroken
was not identifying the chain as broken.  With this patch,
the loop is detected when the chain is only 1 deep; still
enough for storage volume XML to display the file, but now
with a proper error report about where the loop was found.

This patch adds a parameter to virStorageFileGetMetadataRecurse,
so that errors at the top of the chain remain unchanged; messages
issued for backing files now use the name provided by the user
instead of the canonical name (for VDSM, which uses relative
symlinks to device mapper block devices, this is actually more
useful).

* src/util/virstoragefile.c (virStorageFileGetMetadataRecurse):
Add parameter, require canonical path up front.  Mark chain
broken on OOM or loop detection.
(virStorageFileGetMetadata): Pass in canonical name.
Signed-off-by: NEric Blake <eblake@redhat.com>

I noticed that the apparmor code could request metadata even
for a cdrom with no media, which would cause a memory leak of
the hash table used to look for loops in the backing chain.
But even before that, we blindly dereferenced the path for
printing a debug statement, so it is just better to enforce
that this is only used on non-NULL names.

* src/util/virstoragefile.c (virStorageFileGetMetadata): Assume
non-NULL path.
* src/util/virstoragefile.h: Annotate this.
* src/security/virt-aa-helper.c (get_files): Fix caller.
Signed-off-by: NEric Blake <eblake@redhat.com>

Right now, virStorageFileMetadata tracks bool backingStoreIsFile
for whether the backing string specified in metadata can be
resolved as a file (covering both block and regular file
resources) or is treated as a network protocol.  But when
merging this struct with virStorageSource, it will be easier
to just actually track which type of resource it is, as well
as have a reserved value for the case where the resource type
is unknown (or had an error during probing).

* src/util/virstoragefile.h (virStorageType): Add a placeholder
value, swap order to match similar public enum.
* src/util/virstoragefile.c (virStorage): Update string mapping.
* src/conf/domain_conf.c (virDomainDiskSourceParse)
(virDomainDiskDefParseXML, virDomainDiskDefFormat)
(virDomainDiskSourceFormat): Adjust clients.
* src/conf/snapshot_conf.c (virDomainSnapshotDiskDefParseXML):
Likewise.
* src/qemu/qemu_driver.c
(qemuDomainSnapshotPrepareDiskExternalBackingInactive)
(qemuDomainSnapshotPrepareDiskExternalOverlayActive)
(qemuDomainSnapshotPrepareDiskExternalOverlayInactive)
(qemuDomainSnapshotPrepareDiskInternal)
(qemuDomainSnapshotCreateSingleDiskActive): Likewise.
* src/qemu/qemu_command.c (qemuGetDriveSourceString): Likewise.
Signed-off-by: NEric Blake <eblake@redhat.com>

A future patch will merge virStorageFileMetadata and virStorageSource,
but I found it easier to do if both structs use the same information
for tracking whether a source file needs encryption keys.

* src/util/virstoragefile.h (_virStorageFileMetadata): Prepare
full encryption struct instead of just a bool.
* src/storage/storage_backend_fs.c (virStorageBackendProbeTarget):
Use transfer semantics.
* src/storage/storage_backend_gluster.c
(virStorageBackendGlusterRefreshVol): Likewise.
* src/util/virstoragefile.c (virStorageFileGetMetadataInternal):
Populate struct.
(virStorageFileFreeMetadata): Adjust clients.
* tests/virstoragetest.c (testStorageChain): Likewise.
Signed-off-by: NEric Blake <eblake@redhat.com>

Another step towards unification of structures.  While we might
not expose everything in XML via domain disk as we do for
storage volume pointer, both places want to deal with (at least
part of) the backing chain; therefore, moving towards a single
struct usable from both contexts will make the backing chain
code more reusable.

* src/conf/storage_conf.h (_virStoragePerms)
(virStorageTimestamps): Move...
* src/util/virstoragefile.h: ...here.
(_virStorageSource): Add more fields.
* src/util/virstoragefile.c (virStorageSourceClear): Clean
additional fields.
Signed-off-by: NEric Blake <eblake@redhat.com>

Move some functions out of domain_conf for use in the next
patch where snapshot starts to directly use structs in
virstoragefile.

* src/conf/domain_conf.c (virDomainDiskDefFree)
(virDomainDiskSourcePoolDefParse): Adjust callers.
(virDomainDiskSourceDefClear, virDomainDiskSourcePoolDefFree)
(virDomainDiskAuthClear): Move...
* src/util/virstoragefile.c (virStorageSourceClear)
(virStorageSourcePoolDefFree, virStorageSourceAuthClear): ...and
rename.
* src/conf/domain_conf.h (virDomainDiskAuthClear): Drop
declaration.
* src/qemu/qemu_conf.c (qemuTranslateDiskSourcePool): Adjust
caller.
* src/util/virstoragefile.h: Declare them.
* src/libvirt_private.syms (virstoragefile.h): Export them.
Signed-off-by: NEric Blake <eblake@redhat.com>

The code in virstoragefile.c is getting more complex as I
consolidate backing chain handling code.  But for the setuid
virt-login-shell, we don't need to crawl backing chains.  It's
easier to audit things for setuid security if there are fewer
files involved, so this patch moves the one function that
virFileOpen() was actually relying on to also live in virfile.c.

* src/util/virstoragefile.c (virStorageFileIsSharedFS)
(virStorageFileIsSharedFSType): Move...
* src/util/virfile.c (virFileIsSharedFS, virFileIsSharedFSType):
...to here, and rename.
(virFileOpenAs): Update caller.
* src/security/security_selinux.c
(virSecuritySELinuxSetFileconHelper)
(virSecuritySELinuxSetSecurityAllLabel)
(virSecuritySELinuxRestoreSecurityImageLabelInt): Likewise.
* src/security/security_dac.c
(virSecurityDACRestoreSecurityImageLabelInt): Likewise.
* src/qemu/qemu_driver.c (qemuOpenFileAs): Likewise.
* src/qemu/qemu_migration.c (qemuMigrationIsSafe): Likewise.
* src/util/virstoragefile.h: Adjust declarations.
* src/util/virfile.h: Likewise.
* src/libvirt_private.syms (virfile.h, virstoragefile.h): Move
symbols as appropriate.
Signed-off-by: NEric Blake <eblake@redhat.com>

Another struct being moved to util.  This one doesn't have as
much use yet, thankfully.

* src/conf/domain_conf.h (virDomainDiskSourcePoolMode)
(virDomainDiskSourcePoolDef): Move...
* src/util/virstoragefile.h (virStorageSourcePoolMode)
(virStorageSourcePoolDef): ...and rename.
* src/conf/domain_conf.c (virDomainDiskSourcePoolDefFree)
(virDomainDiskSourceDefClear, virDomainDiskSourcePoolDefParse)
(virDomainDiskDefParseXML, virDomainDiskSourceDefParse)
(virDomainDiskSourceDefFormatInternal)
(virDomainDiskDefForeachPath, virDomainDiskSourceIsBlockType):
Adjust clients.
* src/qemu/qemu_conf.c (qemuTranslateDiskSourcePool): Likewise.
* src/libvirt_private.syms (domain_conf.h): Move symbols...
(virstoragefile.h): ...as appropriate.
Signed-off-by: NEric Blake <eblake@redhat.com>

Another enum moved to util/, this time the fallout from renaming
is not quite as large.

* src/conf/domain_conf.h (virDomainDiskProtocol): Move...
* src/util/virstoragefile.h (virStorageNetProtocol): ...and
rename.
* src/conf/domain_conf.c: Update clients.
* src/qemu/qemu_command.c: Likewise.
* src/qemu/qemu_conf.c: Likewise.
* src/qemu/qemu_driver.c: Likewise.
* src/qemu/qemu_migration.c: Likewise.
* src/storage/storage_backend.c: Likewise.
* src/storage/storage_backend_gluster.c: Likewise.
* src/libvirt_private.syms (domain_conf.h): Move symbols...
(virstoragefile.h): ...as appropriate.
Signed-off-by: NEric Blake <eblake@redhat.com>

A continuation of the migration of disk details to virstoragefile.
This patch moves a single enum, but converting the name has quite
a bit of fallout.

* src/conf/domain_conf.h (virDomainDiskType): Move...
* src/util/virstoragefile.h (virStorageType): ...and rename.
* src/bhyve/bhyve_command.c (bhyveBuildDiskArgStr)
(virBhyveProcessBuildLoadCmd): Update clients.
* src/conf/domain_conf.c (virDomainDiskSourceDefParse)
(virDomainDiskDefParseXML, virDomainDiskSourceDefFormatInternal)
(virDomainDiskDefFormat, virDomainDiskGetActualType)
(virDomainDiskDefForeachPath, virDomainDiskSourceIsBlockType):
Likewise.
* src/conf/snapshot_conf.h (_virDomainSnapshotDiskDef): Likewise.
* src/conf/snapshot_conf.c (virDomainSnapshotDiskDefParseXML)
(virDomainSnapshotAlignDisks, virDomainSnapshotDiskDefFormat):
Likewise.
* src/esx/esx_driver.c (esxAutodetectSCSIControllerModel)
(esxDomainDefineXML): Likewise.
* src/locking/domain_lock.c (virDomainLockManagerAddDisk):
Likewise.
* src/lxc/lxc_controller.c
(virLXCControllerSetupLoopDeviceDisk)
(virLXCControllerSetupNBDDeviceDisk)
(virLXCControllerSetupLoopDevices, virLXCControllerSetupDisk):
Likewise.
* src/parallels/parallels_driver.c (parallelsGetHddInfo):
Likewise.
* src/phyp/phyp_driver.c (phypDiskType): Likewise.
* src/qemu/qemu_command.c (qemuGetDriveSourceString)
(qemuDomainDiskGetSourceString, qemuBuildDriveStr)
(qemuBuildCommandLine, qemuParseCommandLineDisk)
(qemuParseCommandLine): Likewise.
* src/qemu/qemu_conf.c (qemuCheckSharedDevice)
(qemuTranslateDiskSourcePool)
(qemuTranslateSnapshotDiskSourcePool): Likewise.
* src/qemu/qemu_domain.c (qemuDomainDeviceDefPostParse)
(qemuDomainDetermineDiskChain): Likewise.
* src/qemu/qemu_driver.c (qemuDomainGetBlockInfo)
(qemuDomainSnapshotPrepareDiskExternalBackingInactive)
(qemuDomainSnapshotPrepareDiskExternalBackingActive)
(qemuDomainSnapshotPrepareDiskExternalOverlayActive)
(qemuDomainSnapshotPrepareDiskExternalOverlayInactive)
(qemuDomainSnapshotPrepareDiskInternal)
(qemuDomainSnapshotPrepare)
(qemuDomainSnapshotCreateSingleDiskActive): Likewise.
* src/qemu/qemu_hotplug.c (qemuDomainChangeEjectableMedia):
Likewise.
* src/qemu/qemu_migration.c (qemuMigrationIsSafe): Likewise.
* src/security/security_apparmor.c
(AppArmorRestoreSecurityImageLabel)
(AppArmorSetSecurityImageLabel): Likewise.
* src/security/security_dac.c (virSecurityDACSetSecurityImageLabel)
(virSecurityDACRestoreSecurityImageLabelInt)
(virSecurityDACSetSecurityAllLabel): Likewise.
* src/security/security_selinux.c
(virSecuritySELinuxRestoreSecurityImageLabelInt)
(virSecuritySELinuxSetSecurityImageLabel)
(virSecuritySELinuxSetSecurityAllLabel): Likewise.
* src/storage/storage_backend.c (virStorageFileBackendForType):
Likewise.
* src/storage/storage_backend_fs.c (virStorageFileBackendFile)
(virStorageFileBackendBlock): Likewise.
* src/storage/storage_backend_gluster.c
(virStorageFileBackendGluster): Likewise.
* src/vbox/vbox_tmpl.c (vboxDomainGetXMLDesc, vboxAttachDrives)
(vboxDomainAttachDeviceImpl, vboxDomainDetachDevice): Likewise.
* src/vmware/vmware_conf.c (vmwareVmxPath): Likewise.
* src/vmx/vmx.c (virVMXParseDisk, virVMXFormatDisk)
(virVMXFormatFloppy): Likewise.
* src/xenxs/xen_sxpr.c (xenParseSxprDisks, xenParseSxpr)
(xenFormatSxprDisk): Likewise.
* src/xenxs/xen_xm.c (xenParseXM, xenFormatXMDisk): Likewise.
* tests/securityselinuxlabeltest.c (testSELinuxLoadDef):
Likewise.
* src/libvirt_private.syms (domain_conf.h): Move symbols...
(virstoragefile.h): ...as appropriate.
Signed-off-by: NEric Blake <eblake@redhat.com>

Continuing the refactoring of host-side storage descriptions out
of conf/domain_conf and into util/virstoragefile, this patch
focuses on details about a host name/port/transport as used by
a network storage volume.

* src/conf/domain_conf.h (virDomainDiskProtocolTransport)
(virDomainDiskHostDef, virDomainDiskHostDefClear)
(virDomainDiskHostDefFree, virDomainDiskHostDefCopy): Move...
* src/util/virstoragefile.h (virStorageNetHostTransport)
(virStorageNetHostDef, virStorageNetHostDefClear)
(virStorageNetHostDefFree, virStorageNetHostDefCopy): ...here,
with better names.
* src/util/virstoragefile.c (virStorageNetHostDefClear)
(virStorageNetHostDefFree, virStorageNetHostDefCopy): Moved from...
* src/conf/domain_conf.c (virDomainDiskHostDefClear)
(virDomainDiskHostDefFree, virDomainDiskHostDefCopy): ...here.
(virDomainDiskSourceDefClear, virDomainDiskSourceDefParse)
(virDomainDiskSourceDefFormatInternal): Adjust callers.
* src/conf/snapshot_conf.h (_virDomainSnapshotDiskDef): Likewise.
* src/conf/snapshot_conf.c (virDomainSnapshotDiskDefClear):
Likewise.
* src/qemu/qemu_command.c (qemuAddRBDHost)
(qemuParseDriveURIString, qemuParseNBDString)
(qemuBuildNetworkDriveURI, qemuParseCommandLineDisk)
(qemuParseCommandLine, qemuGetDriveSourceString): Likewise.
* src/qemu/qemu_command.h: Likewise.
* src/qemu/qemu_conf.c (qemuAddISCSIPoolSourceHost)
(qemuTranslateDiskSourcePool): Likewise.
* src/qemu/qemu_driver.c
(qemuDomainSnapshotCreateSingleDiskActive)
(qemuDomainSnapshotUndoSingleDiskActive): Likewise.
* src/storage/storage_backend_gluster.c
(virStorageFileBackendGlusterInit): Likewise.
* src/storage/storage_driver.c (virStorageFileFree)
(virStorageFileInitInternal): Likewise.
* src/storage/storage_driver.h (_virStorageFile): Likewise.
* src/libvirt_private.syms (domain_conf.h): Move symbols...
(virstoragefile.h): ...as appropriate.
Signed-off-by: NEric Blake <eblake@redhat.com>

When virStorageFileGetMetadata is called with NULL path argument, the
invalid pointer boils down through the recursive worker and is caught by
virHashAddEntry which is thankfully resistant to NULL arguments. As it
doesn't make sense to pursue backing chains of NULL volumes, exit
earlier.

This was noticed in the virt-aahelper-test with a slightly modified
codebase.

Any source file which calls the logging APIs now needs
to have a VIR_LOG_INIT("source.name") declaration at
the start of the file. This provides a static variable
of the virLogSource type.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

This gets rid of another stat() per volume, as well as cutting
bytes read in half, when populating the volumes of a directory
pool during a pool refresh.  Not to mention that it provides an
interface that can let gluster pools also probe file types.

* src/util/virstoragefile.h (virStorageFileProbeFormatFromFD):
Delete.
(virStorageFileProbeFormatFromBuf): New prototype.
(VIR_STORAGE_MAX_HEADER): New constant, based on...
* src/util/virstoragefile.c (STORAGE_MAX_HEAD): ...old name.
(vmdk4GetBackingStore, virStorageFileGetMetadataInternal)
(virStorageFileProbeFormat): Adjust clients.
(virStorageFileProbeFormatFromFD): Delete.
(virStorageFileProbeFormatFromBuf): Export.
* src/storage/storage_backend_fs.c (virStorageBackendProbeTarget):
Adjust client.
* src/libvirt_private.syms (virstoragefile.h): Adjust exports.
Signed-off-by: NEric Blake <eblake@redhat.com>

Future patches will want to learn metadata about a file using
a buffer that was already parsed in order to probe the file's
format.  Rather than reopening and re-reading the file, it makes
sense to separate getting file contents from actually parsing
those contents.

* src/util/virstoragefile.c (virStorageFileGetMetadataFromBuf)
(virStorageFileGetMetadataFromFDInternal): New functions.
(virStorageFileGetMetadataInternal): Hoist fstat() and read() into
callers.
(virStorageFileGetMetadataFromFD)
(virStorageFileGetMetadataRecurse): Rework clients.
* src/util/virstoragefile.h (virStorageFileGetMetadataFromBuf):
New prototype.
* src/libvirt_private.syms (virstoragefile.h): Export it.
Signed-off-by: NEric Blake <eblake@redhat.com>

Our backing file chain code was not very robust to an ill-timed
EINTR, which could lead to a short read causing us to randomly
treat metadata differently than usual.  But the existing
virFileReadLimFD forces an error if we don't read the entire
file, even though we only care about the header of the file.
So add a new virFile function that does what we want.

* src/util/virfile.h (virFileReadHeaderFD): New prototype.
* src/util/virfile.c (virFileReadHeaderFD): New function.
* src/libvirt_private.syms (virfile.h): Export it.
* src/util/virstoragefile.c (virStorageFileGetMetadataInternal)
(virStorageFileProbeFormatFromFD): Use it.
Signed-off-by: NEric Blake <eblake@redhat.com>

'unsigned char *' makes sense if you are doing math on bytes and
don't want to worry about wraparound from a signed 'char'; but
since all we are doing is memcmp() or virReadBufInt*[LB]E(), which
are both safe on either type of char, and since read() prefers to
operate on 'char *', it's simpler to avoid casts by just typing
things as 'char *' from the get-go.  [Technically, read can
operate on an 'unsigned char *' thanks to the C rule that any
pointer can be implicitly converted to 'char *' for legacy K&R
compatibility; but where this patch saves us is if we try to use
virfile.h functions that take 'char **' in order to allocate the
buffer, where the compiler would barf on type mismatch.]

* src/util/virstoragefile.c (FileTypeInfo): Avoid unsigned char.
(cowGetBackingStore, qcow2GetBackingStoreFormat)
(qcowXGetBackingStore, qcow1GetBackingStore)
(qcow2GetBackingStore, vmdk4GetBackingStore, qedGetBackingStore)
(virStorageFileMatchesMagic, virStorageFileMatchesVersion)
(virStorageFileProbeFormatFromBuf, qcow2GetFeatures)
(virStorageFileGetMetadataInternal)
(virStorageFileProbeFormatFromFD): Simplify clients.
Signed-off-by: NEric Blake <eblake@redhat.com>

A qcow2 file with a backing file of 'gluster://host/vol/file' should
not try to look for a directory named './gluster:/' in the file system.

* src/util/virstoragefile.c (virBackingStoreIsFile): Broaden check
to include all protocols.
Signed-off-by: NEric Blake <eblake@redhat.com>

Most of the usage of getuid()/getgid() is in cases where we are
considering what privileges we have. As such the code should be
using the effective IDs, not real IDs.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

This should resolve:

  https://bugzilla.redhat.com/show_bug.cgi?id=1012085

libvirt previously recognized NFS, GFS2, OCFS2, and AFS filesystems as
"shared", and thus eligible for exceptions to certain rules/actions
about chowning image files before handing them off to a guest. This
patch widens the definition of "shared filesystem" to include SMB and
CIFS filesystems (aka "Windows file sharing"); both of these use the
same protocol, but different drivers so there are different magic
numbers for each.

*src/util/virstoragefile.c: Add a helper function to get
the first name of missing backing files, if the name is NULL,
it means the diskchain is not broken.
*src/qemu/qemu_domain.c: qemuDiskChainCheckBroken(disk) to
check if its chain is broken

Convert the type of loop iterators named 'i', 'j', k',
'ii', 'jj', 'kk', to be 'size_t' instead of 'int' or
'unsigned int', also santizing 'ii', 'jj', 'kk' to use
the normal 'i', 'j', 'k' naming
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

Initially proposed as [1], but then changed to comment fix only.  VMDK
can have internal version set to 2 when there are few features added
which do not affect us.  Thanks to Jan's commit a1ee8e18 this can be
easily fixed by adding it to list of supported versions.

[1] http://www.redhat.com/archives/libvir-list/2013-June/msg00419.html

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=836676

Detect qcow2 images with version 3 in the image header as
VIR_STORAGE_FILE_QCOW2.

These images have a feature bitfield, with just one feature supported
so far: lazy_refcounts.

The header length changed too, moving the location of the backing
format name.

Such as on FreeBSD.  Broken in commit aa2a4cff.

* src/util/virstoragefile.c (virStorageFileResize): Add missing ';',
mark conditionally unused variables.
Signed-off-by: NEric Blake <eblake@redhat.com>

The document for "vol-resize" says the new capacity will be sparse
unless "--allocate" is specified, however, the "--allocate" flag
is never implemented. This implements the "--allocate" flag for
fs backend's raw type volume, based on posix_fallocate and the
syscall SYS_fallocate.

This resolves:

     https://bugzilla.redhat.com/show_bug.cgi?id=851411
     https://bugzilla.redhat.com/show_bug.cgi?id=955500

The first problem was that virFileOpenAs was returning fd (-1) in one
of the error cases rather than ret (-errno), so the caller thought
that the error was EPERM rather than ENOENT.

The second problem was that some log messages in the general purpose
qemuOpenFile() function would always say "Failed to create" even if
the caller hadn't included O_CREAT (i.e. they were trying to open an
existing file).

This fixes virFileOpenAs to jump down to the error return (which
returns ret instead of fd) in the previously mentioned incorrect
failure case of virFileOpenAs(), removes all error logging from
virFileOpenAs() (since the callers report it), and modifies
qemuOpenFile to appropriately use "open" or "create" in its log
messages.

NB: I seriously considered removing logging from all callers of
virFileOpenAs(), but there is at least one case where the caller
doesn't want virFileOpenAs() to log any errors, because it's just
going to try again (qemuOpenFile()). We can't simply make a silent
variation of virFileOpenAs() though, because qemuOpenFile() can't make
the decision about whether or not it wants to retry until after
virFileOpenAs() has already returned an error code.

Likewise, I also considered changing virFileOpenAs() to return -1 with
errno set on return, and may still do that, but only as a separate
patch, as it obscures the intent of this patch too much.

The source code base needs to be adapted as well. Some files
include virutil.h just for the string related functions (here,
the include is substituted to match the new file), some include
virutil.h without any need (here, the include is removed), and
some require both.

Commit 027bf2ea used the wrong offset: the text field at the start
of the header has 64 bytes, not 68. [1]

Bug: https://bugzilla.redhat.com/show_bug.cgi?id=921452

[1] https://forums.virtualbox.org/viewtopic.php?p=29267#p29267