+/*
+ * Pick up certain mount options used during the original mount
+ * from /etc/mtab. The basics include the server's IP address and
+ * the server pathname of the share to unregister.
+ *
+ * These options might also describe the mount port, mount protocol
+ * version, and transport protocol used to punch through a firewall.
+ * We will need this information to get through the firewall again
+ * to do the umount.
+ *
+ * Note that option parsing failures won't necessarily cause the
+ * umount request to fail. Those values will be left zero in the
+ * pmap tuple. If the GETPORT call later fails to disambiguate them,
+ * then we fail.
+ */
+static int nfs_umount23(const char *devname, char *string)
+{
+ char *hostname, *dirname;
+ struct mount_options *options;
+ int result = EX_FAIL;
+
+ if (!nfs_parse_devname(devname, &hostname, &dirname))
+ return EX_USAGE;
+
+ options = po_split(string);
+ if (options) {
+ result = nfs_umount_do_umnt(options, &hostname, &dirname);
+ po_destroy(options);
+ } else
+ nfs_error(_("%s: option parsing error"), progname);
+
+ free(hostname);
+ free(dirname);
+ return result;
+}
+
+/*
+ * Detect NFSv4 mounts.
+ *
+ * Consult /proc/mounts to determine if the mount point
+ * is an NFSv4 mount. The kernel is authoritative about
+ * what type of mount this is.
+ *
+ * Returns 1 if "mc" is an NFSv4 mount, zero if not, and
+ * -1 if some error occurred.
+ */
+static int nfs_umount_is_vers4(const struct mntentchn *mc)
+{
+ char buffer[LINELEN], *next;
+ int retval;
+ FILE *f;
+
+ if ((f = fopen(MOUNTSFILE, "r")) == NULL) {
+ fprintf(stderr, "%s: %s\n",
+ MOUNTSFILE, strerror(errno));
+ return -1;