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[libvirt] [PATCH] esx: Use MD5 sum of mount path as storage pool UUID



With the previous storage pool UUID source not all storage pools
had a proper UUID, especially GSX storage pools. The mount path
is unique per host and cannot change during the lifetime of the
datastore. Therefore, its MD5 sum can be used as UUID.

Use gnulib's crypto/md5 module to generate the MD5 sum.
---
 bootstrap.conf               |    1 +
 src/esx/esx_storage_driver.c |  107 +++++++++++-------------------------------
 2 files changed, 28 insertions(+), 80 deletions(-)

diff --git a/bootstrap.conf b/bootstrap.conf
index 5af77a7..ca31a6e 100644
--- a/bootstrap.conf
+++ b/bootstrap.conf
@@ -26,6 +26,7 @@ canonicalize-lgpl
 close
 connect
 count-one-bits
+crypto/md5
 dirname-lgpl
 fcntl-h
 getaddrinfo
diff --git a/src/esx/esx_storage_driver.c b/src/esx/esx_storage_driver.c
index 644e66c..adbe8c6 100644
--- a/src/esx/esx_storage_driver.c
+++ b/src/esx/esx_storage_driver.c
@@ -24,6 +24,7 @@
 
 #include <config.h>
 
+#include "md5.h"
 #include "internal.h"
 #include "util.h"
 #include "memory.h"
@@ -197,10 +198,7 @@ esxStoragePoolLookupByName(virConnectPtr conn, const char *name)
     esxPrivate *priv = conn->storagePrivateData;
     esxVI_ObjectContent *datastore = NULL;
     esxVI_DatastoreHostMount *hostMount = NULL;
-    char *suffix = NULL;
-    int suffixLength;
-    char uuid_string[VIR_UUID_STRING_BUFLEN] = "00000000-00000000-0000-000000000000";
-    unsigned char uuid[VIR_UUID_BUFLEN];
+    unsigned char md5[MD5_DIGEST_SIZE]; /* MD5_DIGEST_SIZE = VIR_UUID_BUFLEN = 16 */
     virStoragePoolPtr pool = NULL;
 
     if (esxVI_EnsureSession(priv->primary) < 0) {
@@ -213,53 +211,22 @@ esxStoragePoolLookupByName(virConnectPtr conn, const char *name)
     }
 
     /*
-     * Datastores don't have a UUID. We can use the 'host.mountInfo.path'
-     * property as source for a "UUID" on ESX, because the property value has
-     * this format:
+     * Datastores don't have a UUID, but we can use the 'host.mountInfo.path'
+     * property as source for a UUID. The mount path is unique per host and
+     * cannot change during the lifetime of the datastore.
      *
-     *   host.mountInfo.path = /vmfs/volumes/4b0beca7-7fd401f3-1d7f-000ae484a6a3
-     *   host.mountInfo.path = /vmfs/volumes/b24b7a78-9d82b4f5    (short format)
-     *
-     * The 'host.mountInfo.path' property comes in two forms, with a complete
-     * "UUID" and a short "UUID".
-     *
-     * But this trailing "UUID" is not guaranteed to be there. On the other
-     * hand we already rely on another implementation detail of the ESX server:
-     * The object name of virtual machine contains an integer, we use that as
-     * domain ID.
+     * The MD5 sum of the mount path can be used as UUID, assuming MD5 is
+     * considered to be collision-free enough for this use case.
      */
     if (esxVI_LookupDatastoreHostMount(priv->primary, datastore->obj,
                                        &hostMount) < 0) {
         goto cleanup;
     }
 
-    if ((suffix = STRSKIP(hostMount->mountInfo->path, "/vmfs/volumes/")) != NULL) {
-        suffixLength = strlen(suffix);
+    md5_buffer(hostMount->mountInfo->path,
+               strlen(hostMount->mountInfo->path), md5);
 
-        if ((suffixLength == 35 && /* = strlen("4b0beca7-7fd401f3-1d7f-000ae484a6a3") */
-             suffix[8] == '-' && suffix[17] == '-' && suffix[22] == '-') ||
-            (suffixLength == 17 && /* = strlen("b24b7a78-9d82b4f5") */
-             suffix[8] == '-')) {
-            /*
-             * Intentionally use memcpy here, because we want to be able to
-             * replace a prefix of the initial Zero-UUID. virStrncpy would
-             * null-terminate the string in an unwanted place.
-             */
-            memcpy(uuid_string, suffix, suffixLength);
-        } else {
-            VIR_WARN("Datastore host mount path suffix '%s' has unexpected "
-                     "format, cannot deduce a UUID from it", suffix);
-        }
-    }
-
-    if (virUUIDParse(uuid_string, uuid) < 0) {
-        ESX_ERROR(VIR_ERR_INTERNAL_ERROR,
-                  _("Could not parse UUID from string '%s'"),
-                  uuid_string);
-        goto cleanup;
-    }
-
-    pool = virGetStoragePool(conn, name, uuid);
+    pool = virGetStoragePool(conn, name, md5);
 
   cleanup:
     esxVI_ObjectContent_Free(&datastore);
@@ -275,9 +242,11 @@ esxStoragePoolLookupByUUID(virConnectPtr conn, const unsigned char *uuid)
 {
     esxPrivate *priv = conn->storagePrivateData;
     esxVI_String *propertyNameList = NULL;
+    esxVI_ObjectContent *datastoreList = NULL;
     esxVI_ObjectContent *datastore = NULL;
+    esxVI_DatastoreHostMount *hostMount = NULL;
+    unsigned char md5[MD5_DIGEST_SIZE]; /* MD5_DIGEST_SIZE = VIR_UUID_BUFLEN = 16 */
     char uuid_string[VIR_UUID_STRING_BUFLEN] = "";
-    char *absolutePath = NULL;
     char *name = NULL;
     virStoragePoolPtr pool = NULL;
 
@@ -285,48 +254,26 @@ esxStoragePoolLookupByUUID(virConnectPtr conn, const unsigned char *uuid)
         return NULL;
     }
 
-    /*
-     * Convert UUID to 'host.mountInfo.path' form by stripping the second '-':
-     *
-     * <---- 14 ----><-------- 22 -------->    <---- 13 ---><-------- 22 -------->
-     * 4b0beca7-7fd4-01f3-1d7f-000ae484a6a3 -> 4b0beca7-7fd401f3-1d7f-000ae484a6a3
-     */
-    virUUIDFormat(uuid, uuid_string);
-    memmove(uuid_string + 13, uuid_string + 14, 22 + 1);
-
-    if (virAsprintf(&absolutePath, "/vmfs/volumes/%s", uuid_string) < 0) {
-        virReportOOMError();
-        goto cleanup;
-    }
-
     if (esxVI_String_AppendValueToList(&propertyNameList, "summary.name") < 0 ||
-        esxVI_LookupDatastoreByAbsolutePath(priv->primary, absolutePath,
-                                            propertyNameList, &datastore,
-                                            esxVI_Occurrence_OptionalItem) < 0) {
+        esxVI_LookupDatastoreList(priv->primary, propertyNameList,
+                                  &datastoreList) < 0) {
         goto cleanup;
     }
 
-    /*
-     * If the first try didn't succeed and the trailing 16 digits are zero then
-     * the "UUID" could be a short one. Strip the 16 zeros and try again:
-     *
-     * <------ 17 ----->                      <------ 17 ----->
-     * b24b7a78-9d82b4f5-0000-000000000000 -> b24b7a78-9d82b4f5
-     */
-    if (datastore == NULL && STREQ(uuid_string + 17, "-0000-000000000000")) {
-        uuid_string[17] = '\0';
+    for (datastore = datastoreList; datastore != NULL;
+         datastore = datastore->_next) {
+        esxVI_DatastoreHostMount_Free(&hostMount);
 
-        VIR_FREE(absolutePath);
-
-        if (virAsprintf(&absolutePath, "/vmfs/volumes/%s", uuid_string) < 0) {
-            virReportOOMError();
+        if (esxVI_LookupDatastoreHostMount(priv->primary, datastore->obj,
+                                           &hostMount) < 0) {
             goto cleanup;
         }
 
-        if (esxVI_LookupDatastoreByAbsolutePath(priv->primary, absolutePath,
-                                                propertyNameList, &datastore,
-                                                esxVI_Occurrence_RequiredItem) < 0) {
-            goto cleanup;
+        md5_buffer(hostMount->mountInfo->path,
+                   strlen(hostMount->mountInfo->path), md5);
+
+        if (memcmp(uuid, md5, VIR_UUID_BUFLEN) == 0) {
+            break;
         }
     }
 
@@ -348,9 +295,9 @@ esxStoragePoolLookupByUUID(virConnectPtr conn, const unsigned char *uuid)
     pool = virGetStoragePool(conn, name, uuid);
 
   cleanup:
-    VIR_FREE(absolutePath);
     esxVI_String_Free(&propertyNameList);
-    esxVI_ObjectContent_Free(&datastore);
+    esxVI_ObjectContent_Free(&datastoreList);
+    esxVI_DatastoreHostMount_Free(&hostMount);
 
     return pool;
 }
-- 
1.7.0.4


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