Re: [RFC PATCH v3 03/11] qapi: net: introduce a way to bypass qemu_opts_parse_noisily()

[Markus Armbruster <armbru@redhat.com>]

Laurent Vivier <lvivier@redhat.com> writes:

> As qemu_opts_parse_noisily() flattens the QAPI structures ("type" field
> of Netdev structure can collides with "type" field of SocketAddress),
> we introduce a way to bypass qemu_opts_parse_noisily() and use directly
> visit_type_Netdev() to parse the backend parameters.
>
> More details from Markus:
>
> qemu_init() passes the argument of -netdev, -nic, and -net to
> net_client_parse().
>
> net_client_parse() parses with qemu_opts_parse_noisily(), passing
> QemuOptsList qemu_netdev_opts for -netdev, qemu_nic_opts for -nic, and
> qemu_net_opts for -net.  Their desc[] are all empty, which means any
> keys are accepted.  The result of the parse (a QemuOpts) is stored in
> the QemuOptsList.
>
> Note that QemuOpts is flat by design.  In some places, we layer non-flat
> on top using dotted keys convention, but not here.
>
> net_init_clients() iterates over the stored QemuOpts, and passes them to
> net_init_netdev(), net_param_nic(), or net_init_client(), respectively.
>
> These functions pass the QemuOpts to net_client_init().  They also do
> other things with the QemuOpts, which we can ignore here.
>
> net_client_init() uses the opts visitor to convert the (flat) QemOpts to
> a (non-flat) QAPI object Netdev.  Netdev is also the argument of QMP
> command netdev_add.
>
> The opts visitor was an early attempt to support QAPI in
> (QemuOpts-based) CLI.  It restricts QAPI types to a certain shape; see
> commit eb7ee2cbeb "qapi: introduce OptsVisitor".
>
> A more modern way to support QAPI is qobject_input_visitor_new_str().
> It uses keyval_parse() instead of QemuOpts for KEY=VALUE,... syntax, and
> it also supports JSON syntax.  The former isn't quite as expressive as
> JSON, but it's a lot closer than QemuOpts + opts visitor.
>
> This commit paves the way to use of the modern way instead.
>
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> ---
>  include/net/net.h |  1 +
>  net/net.c         | 60 +++++++++++++++++++++++++++++++++++++++++++++++
>  softmmu/vl.c      |  3 ++-
>  3 files changed, 63 insertions(+), 1 deletion(-)
>
> diff --git a/include/net/net.h b/include/net/net.h
> index c53c64ac18c4..4ae8ed480f73 100644
> --- a/include/net/net.h
> +++ b/include/net/net.h
> @@ -214,6 +214,7 @@ extern NICInfo nd_table[MAX_NICS];
>  extern const char *host_net_devices[];
>  
>  /* from net.c */
> +int netdev_parse_modern(const char *optarg);
>  int net_client_parse(QemuOptsList *opts_list, const char *str);
>  void show_netdevs(void);
>  void net_init_clients(void);
> diff --git a/net/net.c b/net/net.c
> index 15958f881776..c337d3d753fe 100644
> --- a/net/net.c
> +++ b/net/net.c
> @@ -54,6 +54,7 @@
>  #include "net/colo-compare.h"
>  #include "net/filter.h"
>  #include "qapi/string-output-visitor.h"
> +#include "qapi/qobject-input-visitor.h"
>  
>  /* Net bridge is currently not supported for W32. */
>  #if !defined(_WIN32)
> @@ -63,6 +64,16 @@
>  static VMChangeStateEntry *net_change_state_entry;
>  static QTAILQ_HEAD(, NetClientState) net_clients;
>  
> +typedef struct NetdevQueueEntry {
> +    Netdev *nd;
> +    Location loc;
> +    QSIMPLEQ_ENTRY(NetdevQueueEntry) entry;
> +} NetdevQueueEntry;
> +
> +typedef QSIMPLEQ_HEAD(, NetdevQueueEntry) NetdevQueue;
> +
> +static NetdevQueue nd_queue = QSIMPLEQ_HEAD_INITIALIZER(nd_queue);
> +
>  /***********************************************************/
>  /* network device redirectors */
>  
> @@ -1562,6 +1573,20 @@ out:
>      return ret;
>  }
>  
> +static void netdev_init_modern(void)
> +{
> +    while (!QSIMPLEQ_EMPTY(&nd_queue)) {
> +        NetdevQueueEntry *nd = QSIMPLEQ_FIRST(&nd_queue);
> +
> +        QSIMPLEQ_REMOVE_HEAD(&nd_queue, entry);
> +        loc_push_restore(&nd->loc);
> +        net_client_init1(nd->nd, true, &error_fatal);

Accepts malformed IDs:

    $ qemu-system-x86_64 -netdev type=stream,id=_,addr.type=inet,addr.host=localhost,addr.port=1234
    qemu-system-x86_64: warning: netdev _ has no peer

Compare:

    $ qemu-system-x86_64 -netdev type=user,id=_
    qemu-system-x86_64: -netdev type=user,id=_: Parameter 'id' expects an identifier
    Identifiers consist of letters, digits, '-', '.', '_', starting with a letter.

Calling qmp_netdev_add() instead catches the error.  It won't provide
the hint, though.  Some callers of id_wellformed() do, some don't.
Factoring out bool check_id_wellformed(const char *id, Error **errp)
could make sense.

> +        loc_pop(&nd->loc);
> +        qapi_free_Netdev(nd->nd);
> +        g_free(nd);
> +    }
> +}
> +

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