$ touch /var/lib/libvirt/images/'a<b>c'
$ virsh pool-refresh default
$ virsh vol-dumpxml 'a<b>c' default | head -n2
<volume>
  <name>a<b>c</name>

Oops.  That's not valid XML.  And when we fix the XML
generation, it fails RelaxNG validation.

I'm also tired of seeing <key>(null)</key> in the example
output for volume xml; while we used NULLSTR() to avoid
a NULL deref rather than relying on glibc's printf
extension behavior, it's even better if we avoid the issue
in the first place.  But this requires being careful that
we don't invalidate any storage backends that were relying
on key being unassigned during virStoragVolCreateXML[From].

I would have split this into two patches (one for escaping,
one for avoiding <key>(null)</key>), but since they both
end up touching a lot of the same test files, I ended up
merging it into one.

Note that this patch allows pretty much any volume name
that can appear in a directory (excluding . and .. because
those are special), but does nothing to change the current
(unenforced) RelaxNG claim that pool names will consist
only of letters, numbers, _, -, and +.  Tightening the C
code to match RelaxNG patterns and/or relaxing the grammar
to match the C code for pool names is a task for another
day (but remember, we DID recently tighten C code for
domain names to exclude a leading '.').

* src/conf/storage_conf.c (virStoragePoolSourceFormat)
(virStoragePoolDefFormat, virStorageVolTargetDefFormat)
(virStorageVolDefFormat): Escape user-controlled strings.
(virStorageVolDefParseXML): Parse key, for use in unit tests.
* src/storage/storage_driver.c (storageVolCreateXML)
(storageVolCreateXMLFrom): Ensure parsed key doesn't confuse
volume creation.
* docs/schemas/basictypes.rng (volName): Relax definition.
* tests/storagepoolxml2xmltest.c (mymain): Test it.
* tests/storagevolxml2xmltest.c (mymain): Likewise.
* tests/storagepoolxml2xmlin/pool-dir-naming.xml: New file.
* tests/storagepoolxml2xmlout/pool-dir-naming.xml: Likewise.
* tests/storagevolxml2xmlin/vol-file-naming.xml: Likewise.
* tests/storagevolxml2xmlout/vol-file-naming.xml: Likewise.
* tests/storagevolxml2xmlout/vol-*.xml: Fix fallout.
Signed-off-by: NEric Blake <eblake@redhat.com>
(cherry picked from commit 6cc4d6a3)

Reuse the XML files in storagevolxml2xmlin.

(This requires changing a few backing files to /dev/null,
since virStorageBackendCreateQemuImgCmd checks for its
presence)

Add <features> and <compat> elements to volume target XML.

<compat> is a string which for qcow2 represents the QEMU version
it should be compatible with. Valid values are 0.10 and 1.1.
1.1 is implicit if the <features> element is present, otherwise
qemu-img default is used. 0.10 can be specified to explicitly
create older images after the qemu-img default changes.

<features> contains optional features, so far
<lazy_refcounts/> is available, which enables caching of reference
counters, improving performance for snapshots.

Make it obvious to 'dumpxml' readers what unit we are using,
since our default of KiB for memory (1024) differs from qemu's
default of MiB; and differs from our use of bytes for storage.

Tests were updated via:

$ find tests/*data tests/*out -name '*.xml' | \
  xargs sed -i 's/<\(memory\|currentMemory\|hard_limit\|soft_limit\|min_guarantee\|swap_hard_limit\)>/<\1 unit='"'KiB'>/"
$ find tests/*data tests/*out -name '*.xml' | \
  xargs sed -i 's/<\(capacity\|allocation\|available\)>/<\1 unit='"'bytes'>/"

followed by a few fixes for the stragglers.

Note that with this patch, the RNG for <memory> still forbids
validation of anything except unit='KiB', since the code silently
ignores the attribute; a later patch will expand <memory> to allow
scaled input in the code and update the RNG to match.

* docs/schemas/basictypes.rng (unit): Add 'bytes'.
(scaledInteger): New define.
* docs/schemas/storagevol.rng (sizing): Use it.
* docs/schemas/storagepool.rng (sizing): Likewise.
* docs/schemas/domaincommon.rng (memoryKBElement): New define; use
for memory elements.
* src/conf/storage_conf.c (virStoragePoolDefFormat)
(virStorageVolDefFormat): Likewise.
* src/conf/domain_conf.h (_virDomainDef): Document unit used
internally.
* src/conf/storage_conf.h (_virStoragePoolDef, _virStorageVolDef):
Likewise.
* tests/*data/*.xml: Update all tests.
* tests/*out/*.xml: Likewise.
* tests/define-dev-segfault: Likewise.
* tests/openvzutilstest.c (testReadNetworkConf): Likewise.
* tests/qemuargv2xmltest.c (blankProblemElements): Likewise.

The XML allows <encryption format='unencrypted'/>, this implementation
canonicalizes the internal representation so that "vol->encryption" is
non-NULL iff the volume is encrypted.

Note that partial encryption information (e.g. specifying an encryption
format, but not the key/passphrase) is valid, libvirt will automatically
choose value for the missing information during volume creation.  The
user can read the volume XML, and use the unmodified <encryption> tag in
future operations (without having to be able to understand) its contents.

* docs/formatstorage.html, docs/formatstorage.html.in: Document
  storage volume encryption options
* src/storage_conf.c, src/storage_conf.h: Hook up storage
  encryption XML handling
* tests/storagevolschemadata/vol-qcow2.xml: Test case for encryption
  schema changes

* docs/schemas/storagevol.rng docs/formatstorage.html[.in]
  tests/storagevolschemadata/vol-qcow2.xml: fix storage volume
  inconsistencies in schema and document, patch by Ryota Ozaki
daniel