+ snprintf(new_option, sizeof(new_option) - 1,
+ "nfsvers=%lu", nfs_server.pmap.pm_vers);
+ if (po_append(options, new_option) == PO_FAILED)
+ goto err;
+
+ if (nfs_server.pmap.pm_prot == IPPROTO_TCP)
+ snprintf(new_option, sizeof(new_option) - 1,
+ "proto=tcp");
+ else
+ snprintf(new_option, sizeof(new_option) - 1,
+ "proto=udp");
+ if (po_append(options, new_option) == PO_FAILED)
+ goto err;
+
+ if (nfs_server.pmap.pm_port != NFS_PORT) {
+ snprintf(new_option, sizeof(new_option) - 1,
+ "port=%lu", nfs_server.pmap.pm_port);
+ if (po_append(options, new_option) == PO_FAILED)
+ goto err;
+
+ }
+
+ errno = 0;
+ return options;
+
+err:
+ po_destroy(options);
+ return NULL;
+}
+
+/*
+ * Do the mount(2) system call.
+ *
+ * Returns 1 if successful, otherwise zero.
+ * "errno" is set to reflect the individual error.
+ */
+static int nfs_sys_mount(const struct nfsmount_info *mi, const char *type,
+ const char *options)
+{
+ int result;
+
+ result = mount(mi->spec, mi->node, type,
+ mi->flags & ~(MS_USER|MS_USERS), options);
+ if (verbose && result) {
+ int save = errno;
+ nfs_error(_("%s: mount(2): %s"), progname, strerror(save));
+ errno = save;
+ }
+ return !result;
+}
+
+/*
+ * Retry an NFS mount that failed because the requested service isn't
+ * available on the server.
+ *
+ * Returns 1 if successful. Otherwise, returns zero.
+ * "errno" is set to reflect the individual error.
+ *
+ * Side effect: If the retry is successful, both 'options' and
+ * 'extra_opts' are updated to reflect the mount options that worked.
+ * If the retry fails, 'options' and 'extra_opts' are left unchanged.
+ */
+static int nfs_retry_nfs23mount(struct nfsmount_info *mi)
+{
+ struct mount_options *retry_options;
+ char *retry_str = NULL;
+ char **extra_opts = mi->extra_opts;
+
+ retry_options = rewrite_mount_options(*extra_opts);
+ if (!retry_options)
+ return 0;
+
+ if (po_join(retry_options, &retry_str) == PO_FAILED) {
+ po_destroy(retry_options);
+ errno = EIO;
+ return 0;
+ }
+
+ if (verbose)
+ printf(_("%s: text-based options (retry): '%s'\n"),
+ progname, retry_str);
+
+ if (!nfs_sys_mount(mi, "nfs", retry_str)) {
+ po_destroy(retry_options);
+ free(retry_str);
+ return 0;
+ }
+
+ free(*extra_opts);
+ *extra_opts = retry_str;
+ po_replace(mi->options, retry_options);
+ return 1;
+}
+
+/*
+ * Attempt an NFSv2/3 mount via a mount(2) system call. If the kernel
+ * claims the requested service isn't supported on the server, probe
+ * the server to see what's supported, rewrite the mount options,
+ * and retry the request.
+ *
+ * Returns 1 if successful. Otherwise, returns zero.
+ * "errno" is set to reflect the individual error.
+ *
+ * Side effect: If the retry is successful, both 'options' and
+ * 'extra_opts' are updated to reflect the mount options that worked.
+ * If the retry fails, 'options' and 'extra_opts' are left unchanged.
+ */
+static int nfs_try_nfs23mount(struct nfsmount_info *mi)
+{
+ char **extra_opts = mi->extra_opts;
+
+ if (po_join(mi->options, extra_opts) == PO_FAILED) {
+ errno = EIO;
+ return 0;
+ }
+
+ if (verbose)
+ printf(_("%s: text-based options: '%s'\n"),
+ progname, *extra_opts);
+
+ if (mi->fake)
+ return 1;
+
+ if (nfs_sys_mount(mi, "nfs", *extra_opts))
+ return 1;
+
+ /*
+ * The kernel returns EOPNOTSUPP if the RPC bind failed,
+ * and EPROTONOSUPPORT if the version isn't supported.
+ */
+ if (errno != EOPNOTSUPP && errno != EPROTONOSUPPORT)
+ return 0;
+
+ return nfs_retry_nfs23mount(mi);
+}
+
+/*
+ * Attempt an NFS v4 mount via a mount(2) system call.
+ *
+ * Returns 1 if successful. Otherwise, returns zero.
+ * "errno" is set to reflect the individual error.
+ */
+static int nfs_try_nfs4mount(struct nfsmount_info *mi)
+{
+ char **extra_opts = mi->extra_opts;
+
+ if (po_join(mi->options, extra_opts) == PO_FAILED) {
+ errno = EIO;
+ return 0;