+static int
+estimate_ioctl(zfs_handle_t *zhp, uint64_t fromsnap_obj,
+ boolean_t fromorigin, uint64_t *sizep)
+{
+ zfs_cmd_t zc = { "\0", "\0", "\0", "\0", 0 };
+ libzfs_handle_t *hdl = zhp->zfs_hdl;
+
+ assert(zhp->zfs_type == ZFS_TYPE_SNAPSHOT);
+ assert(fromsnap_obj == 0 || !fromorigin);
+
+ (void) strlcpy(zc.zc_name, zhp->zfs_name, sizeof (zc.zc_name));
+ zc.zc_obj = fromorigin;
+ zc.zc_sendobj = zfs_prop_get_int(zhp, ZFS_PROP_OBJSETID);
+ zc.zc_fromobj = fromsnap_obj;
+ zc.zc_guid = 1; /* estimate flag */
+
+ if (zfs_ioctl(zhp->zfs_hdl, ZFS_IOC_SEND, &zc) != 0) {
+ char errbuf[1024];
+ (void) snprintf(errbuf, sizeof (errbuf), dgettext(TEXT_DOMAIN,
+ "warning: cannot estimate space for '%s'"), zhp->zfs_name);
+
+ switch (errno) {
+ case EXDEV:
+ zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
+ "not an earlier snapshot from the same fs"));
+ return (zfs_error(hdl, EZFS_CROSSTARGET, errbuf));
+
+ case ENOENT:
+ if (zfs_dataset_exists(hdl, zc.zc_name,
+ ZFS_TYPE_SNAPSHOT)) {
+ zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
+ "incremental source (@%s) does not exist"),
+ zc.zc_value);
+ }
+ return (zfs_error(hdl, EZFS_NOENT, errbuf));
+
+ case EDQUOT:
+ case EFBIG:
+ case EIO:
+ case ENOLINK:
+ case ENOSPC:
+ case ENOSTR:
+ case ENXIO:
+ case EPIPE:
+ case ERANGE:
+ case EFAULT:
+ case EROFS:
+ zfs_error_aux(hdl, strerror(errno));
+ return (zfs_error(hdl, EZFS_BADBACKUP, errbuf));
+
+ default:
+ return (zfs_standard_error(hdl, errno, errbuf));
+ }
+ }
+
+ *sizep = zc.zc_objset_type;
+
+ return (0);
+}
+