util: Introduce xattr getter/setter/remover

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>

src/libvirt_private.syms

@@ -1831,6 +1831,7 @@ virFileGetACLs;
 virFileGetHugepageSize;
 virFileGetMountReverseSubtree;
 virFileGetMountSubtree;
+virFileGetXAttr;
 virFileHasSuffix;
 virFileInData;
 virFileIsAbsPath;
@@ -1870,6 +1871,7 @@ virFileReadValueUint;
 virFileRelLinkPointsTo;
 virFileRemove;
 virFileRemoveLastComponent;
+virFileRemoveXAttr;
 virFileResolveAllLinks;
 virFileResolveLink;
 virFileRewrite;
@@ -1877,6 +1879,7 @@ virFileRewriteStr;
 virFileSanitizePath;
 virFileSetACLs;
 virFileSetupDev;
+virFileSetXAttr;
 virFileSkipRoot;
 virFileStripSuffix;
 virFileTouch;

src/util/virfile.c

@@ -64,6 +64,10 @@
 # include <linux/cdrom.h>
 #endif
 
+#if HAVE_LIBATTR
+# include <sys/xattr.h>
+#endif
+
 #include "configmake.h"
 #include "intprops.h"
 #include "vircommand.h"
@@ -4354,3 +4358,120 @@ virFileWaitForExists(const char *path,
 
     return 0;
 }
+
+
+#if HAVE_LIBATTR
+/**
+ * virFileGetXAttr;
+ * @path: a filename
+ * @name: name of xattr
+ * @value: read value
+ *
+ * Reads xattr with @name for given @path and stores it into
+ * @value. Caller is responsible for freeing @value.
+ *
+ * Returns: 0 on success,
+ *         -1 otherwise (with errno set).
+ */
+int
+virFileGetXAttr(const char *path,
+                const char *name,
+                char **value)
+{
+    char *buf = NULL;
+    int ret = -1;
+
+    /* We might be racing with somebody who sets the same attribute. */
+    while (1) {
+        ssize_t need;
+        ssize_t got;
+
+        /* The first call determines how many bytes we need to allocate. */
+        if ((need = getxattr(path, name, NULL, 0)) < 0)
+            goto cleanup;
+
+        if (VIR_REALLOC_N_QUIET(buf, need + 1) < 0)
+            goto cleanup;
+
+        if ((got = getxattr(path, name, buf, need)) < 0) {
+            if (errno == ERANGE)
+                continue;
+            goto cleanup;
+        }
+
+        buf[got] = '\0';
+        break;
+    }
+
+    VIR_STEAL_PTR(*value, buf);
+    ret = 0;
+ cleanup:
+    VIR_FREE(buf);
+    return ret;
+}
+
+/**
+ * virFileSetXAttr:
+ * @path: a filename
+ * @name: name of xattr
+ * @value: value to set
+ *
+ * Sets xattr of @name and @value on @path.
+ *
+ * Returns: 0 on success,
+ *         -1 otherwise (with errno set).
+ */
+int
+virFileSetXAttr(const char *path,
+                const char *name,
+                const char *value)
+{
+    return setxattr(path, name, value, strlen(value), 0);
+}
+
+/**
+ * virFileRemoveXAttr:
+ * @path: a filename
+ * @name: name of xattr
+ *
+ * Remove xattr of @name on @path.
+ *
+ * Returns: 0 on success,
+ *         -1 otherwise (with errno set).
+ */
+int
+virFileRemoveXAttr(const char *path,
+                   const char *name)
+{
+    return removexattr(path, name);
+}
+
+#else /* !HAVE_LIBATTR */
+
+int
+virFileGetXAttr(const char *path ATTRIBUTE_UNUSED,
+                const char *name ATTRIBUTE_UNUSED,
+                char **value ATTRIBUTE_UNUSED)
+{
+    errno = ENOSYS;
+    return -1;
+}
+
+int
+virFileSetXAttr(const char *path ATTRIBUTE_UNUSED,
+                const char *name ATTRIBUTE_UNUSED,
+                const char *value ATTRIBUTE_UNUSED)
+{
+    errno = ENOSYS;
+    return -1;
+}
+
+int
+virFileRemoveXAttr(const char *path ATTRIBUTE_UNUSED,
+                   const char *name ATTRIBUTE_UNUSED)
+{
+    errno = ENOSYS;
+    return -1;
+}
+
+#endif /* HAVE_LIBATTR */

src/util/virfile.h

@@ -382,4 +382,15 @@ int virFileInData(int fd,
 
 VIR_DEFINE_AUTOPTR_FUNC(virFileWrapperFd, virFileWrapperFdFree)
 
+int virFileGetXAttr(const char *path,
+                    const char *name,
+                    char **value);
+
+int virFileSetXAttr(const char *path,
+                    const char *name,
+                    const char *value);
+
+int virFileRemoveXAttr(const char *path,
+                       const char *name);
+
 #endif /* LIBVIRT_VIRFILE_H */