Re: [Qemu-devel] [RFC PATCH 09/13] qmp: add NBD server commands

[Luiz Capitulino <lcapitulino@redhat.com>]

On Mon, 27 Aug 2012 17:00:22 +0200
Paolo Bonzini <pbonzini@redhat.com> wrote:

> Adding an NBD server inside QEMU is trivial, since all the logic is
> in nbd.c and can be shared easily between qemu-nbd and QEMU itself.
> The main difference is that qemu-nbd serves a single unnamed export,
> while QEMU serves named exports.

Quickly reviewed the qmp part and it looks good to me (apart from TODOs
of course, specially on error handling).

I've only a few minor comments to the schema.

> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  Makefile.objs    |  2 +-
>  blockdev-nbd.c   | 93 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  qapi-schema.json | 69 +++++++++++++++++++++++++++++++++++++++++
>  qmp-commands.hx  | 16 ++++++++++
>  4 file modificati, 179 inserzioni(+). 1 rimozione(-)
>  create mode 100644 blockdev-nbd.c
> 
> diff --git a/Makefile.objs b/Makefile.objs
> index 4412757..c42affc 100644
> --- a/Makefile.objs
> +++ b/Makefile.objs
> @@ -59,7 +59,7 @@ endif
>  # suppress *all* target specific code in case of system emulation, i.e. a
>  # single QEMU executable should support all CPUs and machines.
>  
> -common-obj-y = $(block-obj-y) blockdev.o
> +common-obj-y = $(block-obj-y) blockdev.o blockdev-nbd.o
>  common-obj-y += net.o net/
>  common-obj-y += qom/
>  common-obj-y += readline.o console.o cursor.o
> diff --git a/blockdev-nbd.c b/blockdev-nbd.c
> new file mode 100644
> index 0000000..5a415be
> --- /dev/null
> +++ b/blockdev-nbd.c
> @@ -0,0 +1,93 @@
> +/*
> + * QEMU host block devices
> + *
> + * Copyright (c) 2003-2008 Fabrice Bellard
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or
> + * later.  See the COPYING file in the top-level directory.
> + */
> +
> +#include "blockdev.h"
> +#include "hw/block-common.h"
> +#include "monitor.h"
> +#include "qerror.h"
> +#include "sysemu.h"
> +#include "qmp-commands.h"
> +#include "trace.h"
> +#include "nbd.h"
> +#include "qemu_socket.h"
> +
> +static int server_fd = -1;
> +
> +static void nbd_accept(void *opaque)
> +{
> +    struct sockaddr_in addr;
> +    socklen_t addr_len = sizeof(addr);
> +
> +    int fd = accept(server_fd, (struct sockaddr *)&addr, &addr_len);
> +    if (fd >= 0) {
> +        nbd_client_new(NULL, fd, NULL);
> +    }
> +}
> +
> +static void nbd_server_start(QemuOpts *opts, Error **errp)
> +{
> +    if (server_fd != -1) {
> +        /* TODO: error */
> +        return;
> +    }
> +
> +    server_fd = inet_listen_opts(opts, 0, errp);
> +    if (server_fd != -1) {
> +        qemu_set_fd_handler2(server_fd, NULL, nbd_accept, NULL, NULL);
> +    }
> +}
> +
> +void qmp_nbd_server_start(IPSocketAddress *addr, Error **errp)
> +{
> +    QemuOpts *opts;
> +
> +    opts = qemu_opts_create(&socket_opts, NULL, 0, NULL);
> +    qemu_opt_set(opts, "host", addr->host);
> +    qemu_opt_set(opts, "port", addr->port);
> +
> +    addr->ipv4 |= !addr->has_ipv4;
> +    addr->ipv6 |= !addr->has_ipv6;
> +    if (!addr->ipv4 || !addr->ipv6) {
> +        qemu_opt_set_bool(opts, "ipv4", addr->ipv4);
> +        qemu_opt_set_bool(opts, "ipv6", addr->ipv6);
> +    }
> +
> +    nbd_server_start(opts, errp);
> +    qemu_opts_del(opts);
> +}
> +
> +
> +void qmp_nbd_server_add(const char *device, bool has_writable, bool writable,
> +                        Error **errp)
> +{
> +    BlockDriverState *bs;
> +    NBDExport *exp;
> +
> +    bs = bdrv_find(device);
> +    if (!bs) {
> +        error_set(errp, QERR_DEVICE_NOT_FOUND, device);
> +        return;
> +    }
> +
> +    if (nbd_export_find(bdrv_get_device_name(bs))) {
> +        /* TODO: error */
> +        return;
> +    }
> +
> +    exp = nbd_export_new(bs, 0, -1, writable ? 0 : NBD_FLAG_READ_ONLY);
> +    nbd_export_set_name(exp, device);
> +}
> +
> +void qmp_nbd_server_stop(Error **errp)
> +{
> +    nbd_export_close_all();
> +    qemu_set_fd_handler2(server_fd, NULL, NULL, NULL, NULL);
> +    close(server_fd);
> +    server_fd = -1;
> +}
> diff --git a/qapi-schema.json b/qapi-schema.json
> index 3d2b2d1..d792d2c 100644
> --- a/qapi-schema.json
> +++ b/qapi-schema.json
> @@ -2275,6 +2275,30 @@
>      'opts': 'NetClientOptions' } }
>  
>  ##
> +# @IPSocketAddress
> +#
> +# Captures the destination address of an IP socket
> +#
> +# @host: host part of the address
> +#
> +# @port: port part of the address, or lowest port if @to is present
> +#
> +# @to: highest port to try

Doesn't exist in data. If you add, please use a more descriptive name.

> +#
> +# @ipv4: whether to accept IPv4 addresses, default try both IPv4 and IPv6
> +#
> +# @ipv6: whether to accept IPv6 addresses, default try both IPv4 and IPv6

Both are missing #optional.

> +#
> +# Since 1.3
> +##
> +{ 'type': 'IPSocketAddress',
> +  'data': {
> +    'host': 'str',
> +    'port': 'str',
> +    '*ipv4': 'bool',
> +    '*ipv6': 'bool' } }
> +
> +##
>  # @getfd:
>  #
>  # Receive a file descriptor via SCM rights and assign it a name
> @@ -2454,3 +2478,46 @@
>  #
>  ##
>  { 'command': 'query-fdsets', 'returns': ['FdsetInfo'] }
> +
> +##
> +# @nbd-server-start:
> +#
> +# Start an NBD server listening on the given host and port.
> +#
> +# @addr: Interface on which to listen, nothing for all interfaces.
> +#
> +# Since: 1.3.0
> +#
> +##
> +{ 'command': 'nbd-server-start',
> +  'data': { 'addr': 'IPSocketAddress' } }
> +
> +##
> +# @nbd-server-add:
> +#
> +# Export a device to QEMU's embedded NBD server.
> +#
> +# @device: Block device to be exported
> +#
> +# @writable: Whether clients should be able to write to the device via the
> +#     NBD connection (default false).

Missing #optional.

> +#
> +# Returns: error if the device is already marked for export.
> +#
> +# Since: 1.3.0
> +#
> +##
> +{ 'command': 'nbd-server-add', 'data': {'device': 'str', '*writable': 'bool'} }
> +
> +##
> +# @nbd-server-stop:
> +#
> +# Stop QEMU's embedded NBD server, and unregister all devices previously
> +# added via nbd-server-add
> +#
> +# Returns: error if the server is already running.

That error pertains to nbd-start-start.

> +#
> +# Since: 1.3.0
> +#
> +##
> +{ 'command': 'nbd-server-stop' }
> diff --git a/qmp-commands.hx b/qmp-commands.hx
> index 2ce4ce6..1f7d6fe 100644
> --- a/qmp-commands.hx
> +++ b/qmp-commands.hx
> @@ -2481,6 +2481,22 @@ EQMP
>      },
>  
>      {
> +        .name       = "nbd-server-start",
> +        .args_type  = "addr:q",
> +        .mhandler.cmd_new = qmp_marshal_input_nbd_server_start,
> +    },
> +    {
> +        .name       = "nbd-server-add",
> +        .args_type  = "device:B,writable:b?",
> +        .mhandler.cmd_new = qmp_marshal_input_nbd_server_add,
> +    },
> +    {
> +        .name       = "nbd-server-stop",
> +        .args_type  = "",
> +        .mhandler.cmd_new = qmp_marshal_input_nbd_server_stop,
> +    },
> +
> +    {
>          .name       = "change-vnc-password",
>          .args_type  = "password:s",
>          .mhandler.cmd_new = qmp_marshal_input_change_vnc_password,