On 17.10.19 15:01, Kevin Wolf wrote:
> Add a --nbd-server option to qemu-storage-daemon to start the built-in
> NBD server right away. It maps the arguments for nbd-server-start to the
> command line.

Well, it doesn’t quite, because nbd-server-start takes a
SocketAddressLegacy, and this takes a SocketAddress.

On one hand I can understand why you would do it differently (especially
for command-line options), but on the other I find it a bit problematic
to have --nbd-server be slightly different from nbd-server-start when
both are intended to be the same.

My biggest problem though lies in the duplication in the QAPI schema.
If NbdServerOptions.addr were a SocketAddressLegacy, we could let
nbd-server-start’s options just be of type NbdServerOptions and thus get
rid of the duplication.

I suspect in practice it’s all not that big of a problem.  I can’t call
it bad if --nbd-server is just nicer to use.  And the biggest problem
with duplication in the QAPI schema is that nbd-server-start and
--nbd-server might get out of sync.  But realistically, I don’t see that
happen, because if nbd-server-start changes, nbd_server_start() will
change, too, so we’ll get compile errors in nbd_server_start_options().

*shrug*

But I do think the commit message should explain why we can’t just use
NbdServerOptions for nbd-server-start.

Max

> Example (only with required options):
> 
>     --nbd-server addr.type=inet,addr.host=localhost,addr.port=10809
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  qapi/block.json       | 18 ++++++++++++++++++
>  include/block/nbd.h   |  1 +
>  blockdev-nbd.c        |  5 +++++
>  qemu-storage-daemon.c | 26 +++++++++++++++++++++++++-
>  Makefile.objs         |  2 +-
>  5 files changed, 50 insertions(+), 2 deletions(-)
> 
> diff --git a/qapi/block.json b/qapi/block.json
> index 145c268bb6..7fe0cf6538 100644
> --- a/qapi/block.json
> +++ b/qapi/block.json
> @@ -215,6 +215,24 @@
>              '*id': 'str',
>              '*force': 'bool' } }
>  
> +##
> +# @NbdServerOptions:
> +#
> +# @addr: Address on which to listen.
> +# @tls-creds: ID of the TLS credentials object (since 2.6).
> +# @tls-authz: ID of the QAuthZ authorization object used to validate
> +#             the client's x509 distinguished name. This object is
> +#             is only resolved at time of use, so can be deleted and
> +#             recreated on the fly while the NBD server is active.
> +#             If missing, it will default to denying access (since 4.0).
> +#
> +# Since: 4.2
> +##
> +{ 'struct': 'NbdServerOptions',
> +  'data': { 'addr': 'SocketAddress',
> +            '*tls-creds': 'str',
> +            '*tls-authz': 'str'} }
> +
>  ##
>  # @nbd-server-start:
>  #
> diff --git a/include/block/nbd.h b/include/block/nbd.h
> index 316fd705a9..2a7441491a 100644
> --- a/include/block/nbd.h
> +++ b/include/block/nbd.h
> @@ -353,6 +353,7 @@ void nbd_client_put(NBDClient *client);
>  
>  void nbd_server_start(SocketAddress *addr, const char *tls_creds,
>                        const char *tls_authz, Error **errp);
> +void nbd_server_start_options(NbdServerOptions *arg, Error **errp);
>  
>  /* nbd_read
>   * Reads @size bytes from @ioc. Returns 0 on success.
> diff --git a/blockdev-nbd.c b/blockdev-nbd.c
> index 6a8b206e1d..d4c1fd4166 100644
> --- a/blockdev-nbd.c
> +++ b/blockdev-nbd.c
> @@ -132,6 +132,11 @@ void nbd_server_start(SocketAddress *addr, const char *tls_creds,
>      nbd_server = NULL;
>  }
>  
> +void nbd_server_start_options(NbdServerOptions *arg, Error **errp)
> +{
> +    nbd_server_start(arg->addr, arg->tls_creds, arg->tls_authz, errp);
> +}
> +
>  void qmp_nbd_server_start(SocketAddressLegacy *addr,
>                            bool has_tls_creds, const char *tls_creds,
>                            bool has_tls_authz, const char *tls_authz,
> diff --git a/qemu-storage-daemon.c b/qemu-storage-daemon.c
> index 904e3c3a46..51882452f3 100644
> --- a/qemu-storage-daemon.c
> +++ b/qemu-storage-daemon.c
> @@ -25,11 +25,14 @@
>  #include "qemu/osdep.h"
>  
>  #include "block/block.h"
> +#include "block/nbd.h"
>  #include "crypto/init.h"
>  
>  #include "qapi/error.h"
> -#include "qapi/qapi-visit-block-core.h"
> +#include "qapi/qapi-commands-block.h"
>  #include "qapi/qapi-commands-block-core.h"
> +#include "qapi/qapi-visit-block.h"
> +#include "qapi/qapi-visit-block-core.h"
>  #include "qapi/qobject-input-visitor.h"
>  
>  #include "qemu-common.h"
> @@ -64,6 +67,12 @@ static void help(void)
>  "             [,driver specific parameters...]\n"
>  "                         configure a block backend\n"
>  "\n"
> +"  --nbd-server addr.type=inet,addr.host=<host>,addr.port=<port>\n"
> +"               [,tls-creds=<id>][,tls-authz=<id>]\n"
> +"  --nbd-server addr.type=unix,addr.path=<path>\n"
> +"               [,tls-creds=<id>][,tls-authz=<id>]\n"
> +"                         start an NBD server for exporting block nodes\n"
> +"\n"
>  "  --object <properties>  define a QOM object such as 'secret' for\n"
>  "                         passwords and/or encryption keys\n"
>  "\n"
> @@ -74,6 +83,7 @@ QEMU_HELP_BOTTOM "\n",
>  enum {
>      OPTION_OBJECT = 256,
>      OPTION_BLOCKDEV,
> +    OPTION_NBD_SERVER,
>  };
>  
>  static QemuOptsList qemu_object_opts = {
> @@ -95,6 +105,7 @@ static int process_options(int argc, char *argv[], Error **errp)
>          {"help", no_argument, 0, 'h'},
>          {"object", required_argument, 0, OPTION_OBJECT},
>          {"blockdev", required_argument, 0, OPTION_BLOCKDEV},
> +        {"nbd-server", required_argument, 0, OPTION_NBD_SERVER},
>          {"version", no_argument, 0, 'V'},
>          {"trace", required_argument, NULL, 'T'},
>          {0, 0, 0, 0}
> @@ -152,6 +163,19 @@ static int process_options(int argc, char *argv[], Error **errp)
>                  qapi_free_BlockdevOptions(options);
>                  break;
>              }
> +        case OPTION_NBD_SERVER:
> +            {
> +                Visitor *v;
> +                NbdServerOptions *options;
> +
> +                v = qobject_input_visitor_new_str(optarg, NULL, &error_fatal);
> +                visit_type_NbdServerOptions(v, NULL, &options, &error_fatal);
> +                visit_free(v);
> +
> +                nbd_server_start_options(options, &error_fatal);
> +                qapi_free_NbdServerOptions(options);
> +                break;
> +            }
>          }
>      }
>      if (optind != argc) {
> diff --git a/Makefile.objs b/Makefile.objs
> index 00fdf54500..cc262e445f 100644
> --- a/Makefile.objs
> +++ b/Makefile.objs
> @@ -42,7 +42,7 @@ io-obj-y = io/
>  # used for system emulation, too, but specified separately there)
>  
>  storage-daemon-obj-y = block/
> -storage-daemon-obj-y += blockdev.o iothread.o
> +storage-daemon-obj-y += blockdev.o blockdev-nbd.o iothread.o
>  
>  ######################################################################
>  # Target independent part of system emulation. The long term path is to
>