nbd: allow setting of an export name for qemu-nbd server

The qemu-nbd server currently always uses the old style protocol
since it never sets any export name. This is a problem because
future TLS support will require use of the new style protocol
negotiation.

This adds "--exportname NAME" / "-x NAME" arguments to qemu-nbd
which allow the user to set an explicit export name. When an
export name is set the server will always use the new style
NBD protocol.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>
Message-Id: <1455129674-17255-11-git-send-email-berrange@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

qemu-nbd.c

@@ -44,6 +44,7 @@
 #define QEMU_NBD_OPT_OBJECT        5
 
 static NBDExport *exp;
+static bool newproto;
 static int verbose;
 static char *srcpath;
 static SocketAddress *saddr;
@@ -339,7 +340,7 @@ static gboolean nbd_accept(QIOChannel *ioc, GIOCondition cond, gpointer opaque)
 
     nb_fds++;
     nbd_update_server_watch();
-    nbd_client_new(exp, cioc, nbd_client_closed);
+    nbd_client_new(newproto ? NULL : exp, cioc, nbd_client_closed);
     object_unref(OBJECT(cioc));
 
     return TRUE;
@@ -413,7 +414,7 @@ int main(int argc, char **argv)
     off_t fd_size;
     QemuOpts *sn_opts = NULL;
     const char *sn_id_or_name = NULL;
-    const char *sopt = "hVb:o:p:rsnP:c:dvk:e:f:tl:";
+    const char *sopt = "hVb:o:p:rsnP:c:dvk:e:f:tl:x:";
     struct option lopt[] = {
         { "help", 0, NULL, 'h' },
         { "version", 0, NULL, 'V' },
@@ -437,6 +438,7 @@ int main(int argc, char **argv)
         { "persistent", 0, NULL, 't' },
         { "verbose", 0, NULL, 'v' },
         { "object", 1, NULL, QEMU_NBD_OPT_OBJECT },
+        { "export-name", 1, NULL, 'x' },
         { NULL, 0, NULL, 0 }
     };
     int ch;
@@ -453,6 +455,7 @@ int main(int argc, char **argv)
     Error *local_err = NULL;
     BlockdevDetectZeroesOptions detect_zeroes = BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF;
     QDict *options = NULL;
+    const char *export_name = NULL;
 
     /* The client thread uses SIGTERM to interrupt the server.  A signal
      * handler ensures that "qemu-nbd -v -c" exits with a nice status code.
@@ -604,6 +607,9 @@ int main(int argc, char **argv)
         case 't':
             persistent = 1;
             break;
+        case 'x':
+            export_name = optarg;
+            break;
         case 'v':
             verbose = 1;
             break;
@@ -783,6 +789,10 @@ int main(int argc, char **argv)
         error_report_err(local_err);
         exit(EXIT_FAILURE);
     }
+    if (export_name) {
+        nbd_export_set_name(exp, export_name);
+        newproto = true;
+    }
 
     server_ioc = qio_channel_socket_new();
     if (qio_channel_socket_listen_sync(server_ioc, saddr, &local_err) < 0) {

qemu-nbd.texi

@@ -73,6 +73,9 @@ Disconnect the device @var{dev}
 Allow up to @var{num} clients to share the device (default @samp{1})
 @item -t, --persistent
 Don't exit on the last connection
+@item -x NAME, --export-name=NAME
+Set the NBD volume export name. This switches the server to use
+the new style NBD protocol negotiation
 @item -v, --verbose
 Display extra debugging information
 @item -h, --help