conf: Add support for requesting of XML metadata via the API

The virDomainGetMetadata function was designed to support also retrieval
of app specific metadata from the <metadata> element. This functionality
was never implemented originally.

src/conf/domain_conf.c

@@ -18542,7 +18542,6 @@ virDomainObjGetMetadata(virDomainObjPtr vm,
                         unsigned int flags)
 {
     virDomainDefPtr def;
-    char *field = NULL;
     char *ret = NULL;
 
     virCheckFlags(VIR_DOMAIN_AFFECT_LIVE |
@@ -18557,16 +18556,20 @@ virDomainObjGetMetadata(virDomainObjPtr vm,
 
     switch ((virDomainMetadataType) type) {
     case VIR_DOMAIN_METADATA_DESCRIPTION:
-        field = def->description;
+        if (VIR_STRDUP(ret, def->description) < 0)
+            goto cleanup;
         break;
 
     case VIR_DOMAIN_METADATA_TITLE:
-        field = def->title;
+        if (VIR_STRDUP(ret, def->title) < 0)
+            goto cleanup;
         break;
 
     case VIR_DOMAIN_METADATA_ELEMENT:
-        virReportError(VIR_ERR_ARGUMENT_UNSUPPORTED, "%s",
+        if (!def->metadata)
-                       _("<metadata> element is not yet supported"));
+            break;
+
+        if (virXMLExtractNamespaceXML(def->metadata, uri, &ret) < 0)
             goto cleanup;
         break;
 
@@ -18577,12 +18580,10 @@ virDomainObjGetMetadata(virDomainObjPtr vm,
         break;
     }
 
-    if (!field)
+    if (!ret)
         virReportError(VIR_ERR_NO_DOMAIN_METADATA, "%s",
                        _("Requested metadata element is not present"));
 
-    ignore_value(VIR_STRDUP(ret, field));
-
 cleanup:
     return ret;
 }

src/libvirt_private.syms

@@ -2092,6 +2092,7 @@ virUUIDParse;
 
 # util/virxml.h
 virXMLChildElementCount;
+virXMLExtractNamespaceXML;
 virXMLNodeToString;
 virXMLParseHelper;
 virXMLPickShellSafeComment;

src/util/virxml.c

@@ -928,3 +928,125 @@ cleanup:
 
      return ret;
 }
+
+typedef int (*virXMLForeachCallback)(xmlNodePtr node,
+                                     void *opaque);
+
+static int
+virXMLForeachNode(xmlNodePtr root,
+                  virXMLForeachCallback cb,
+                  void *opaque);
+
+static int
+virXMLForeachNode(xmlNodePtr root,
+                  virXMLForeachCallback cb,
+                  void *opaque)
+{
+    xmlNodePtr next;
+    int ret;
+
+    for (next = root; next; next = next->next) {
+        if ((ret = cb(next, opaque)) != 0)
+            return ret;
+
+        /* recurse into children */
+        if (next->children) {
+            if ((ret = virXMLForeachNode(next->children, cb, opaque)) != 0)
+                return ret;
+        }
+    }
+
+    return 0;
+}
+
+
+static int
+virXMLRemoveElementNamespace(xmlNodePtr node,
+                             void *opaque)
+{
+    const char *uri = opaque;
+
+    if (node->ns &&
+        STREQ_NULLABLE((const char *)node->ns->href, uri))
+        xmlSetNs(node, NULL);
+    return 0;
+}
+
+
+xmlNodePtr
+virXMLFindChildNodeByNs(xmlNodePtr root,
+                        const char *uri)
+{
+    xmlNodePtr next;
+
+    for (next = root->children; next; next = next->next) {
+        if (next->ns &&
+            STREQ_NULLABLE((const char *) next->ns->href, uri))
+            return next;
+    }
+
+    return NULL;
+}
+
+
+/**
+ * virXMLExtractNamespaceXML: extract a sub-namespace of XML as string
+ */
+int
+virXMLExtractNamespaceXML(xmlNodePtr root,
+                          const char *uri,
+                          char **doc)
+{
+    xmlNodePtr node;
+    xmlNodePtr nodeCopy = NULL;
+    xmlNsPtr actualNs;
+    xmlNsPtr prevNs = NULL;
+    char *xmlstr = NULL;
+    int ret = -1;
+
+    if (!(node = virXMLFindChildNodeByNs(root, uri))) {
+        /* node not found */
+        ret = 1;
+        goto cleanup;
+    }
+
+    /* copy the node so that we can modify the namespace */
+    if (!(nodeCopy = xmlCopyNode(node, 1))) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("Failed to copy XML node"));
+        goto cleanup;
+    }
+
+    virXMLForeachNode(nodeCopy, virXMLRemoveElementNamespace,
+                      (void *)uri);
+
+    /* remove the namespace declaration
+     *  - it's only a single linked list ... doh */
+    for (actualNs = nodeCopy->nsDef; actualNs; actualNs = actualNs->next) {
+        if (STREQ_NULLABLE((const char *)actualNs->href, uri)) {
+
+            /* unlink */
+            if (prevNs)
+                prevNs->next = actualNs->next;
+            else
+                nodeCopy->nsDef = actualNs->next;
+
+            /* discard */
+            xmlFreeNs(actualNs);
+            break;
+        }
+
+        prevNs = actualNs;
+    }
+
+    if (!(xmlstr = virXMLNodeToString(nodeCopy->doc, nodeCopy)))
+        goto cleanup;
+
+    ret = 0;
+
+cleanup:
+    if (doc)
+        *doc = xmlstr;
+    xmlFreeNode(nodeCopy);
+    return ret;
+}

src/util/virxml.h

@@ -165,4 +165,11 @@ int virXMLSaveFile(const char *path,
 
 char *virXMLNodeToString(xmlDocPtr doc, xmlNodePtr node);
 
+xmlNodePtr virXMLFindChildNodeByNs(xmlNodePtr root,
+                                   const char *uri);
+
+int virXMLExtractNamespaceXML(xmlNodePtr root,
+                              const char *uri,
+                              char **doc);
+
 #endif                          /* __VIR_XML_H__ */