Re: [PATCH v2 2/2] vnc: add qmp to support reload vnc tls certificates

[Markus Armbruster]

Zihao Chang <changzihao1@huawei.com> writes:

> QEMU loads vnc tls certificates only when vm is started. This patch
> provides a new qmp to reload vnc tls certificates without restart
> vnc-server/VM.
> {"execute": "reload-vnc-cert"}
>
> Signed-off-by: Zihao Chang <changzihao1@huawei.com>
> ---
>  include/ui/console.h |  1 +
>  monitor/qmp-cmds.c   |  5 +++++
>  qapi/ui.json         | 18 ++++++++++++++++++
>  ui/vnc.c             | 24 ++++++++++++++++++++++++
>  4 files changed, 48 insertions(+)
>
> diff --git a/include/ui/console.h b/include/ui/console.h
> index 5dd21976a3..60a24a8bb5 100644
> --- a/include/ui/console.h
> +++ b/include/ui/console.h
> @@ -441,6 +441,7 @@ int vnc_display_password(const char *id, const char 
> *password);
>  int vnc_display_pw_expire(const char *id, time_t expires);
>  QemuOpts *vnc_parse(const char *str, Error **errp);
>  int vnc_init_func(void *opaque, QemuOpts *opts, Error **errp);
> +void vnc_display_reload_cert(const char *id,  Error **errp);

Make this return bool, please.

error.h's big comment:

 * = Rules =
 *
 * - Functions that use Error to report errors have an Error **errp
 *   parameter.  It should be the last parameter, except for functions
 *   taking variable arguments.
 *
 * - You may pass NULL to not receive the error, &error_abort to abort
 *   on error, &error_fatal to exit(1) on error, or a pointer to a
 *   variable containing NULL to receive the error.
 *
 * - Separation of concerns: the function is responsible for detecting
 *   errors and failing cleanly; handling the error is its caller's
 *   job.  Since the value of @errp is about handling the error, the
 *   function should not examine it.
 *
 * - The function may pass @errp to functions it calls to pass on
 *   their errors to its caller.  If it dereferences @errp to check
 *   for errors, it must use ERRP_GUARD().
 *
 * - On success, the function should not touch *errp.  On failure, it
 *   should set a new error, e.g. with error_setg(errp, ...), or
 *   propagate an existing one, e.g. with error_propagate(errp, ...).
 *
 * - Whenever practical, also return a value that indicates success /
 *   failure.  This can make the error checking more concise, and can
 *   avoid useless error object creation and destruction.  Note that
 *   we still have many functions returning void.  We recommend
 *   • bool-valued functions return true on success / false on failure,
 *   • pointer-valued functions return non-null / null pointer, and
 *   • integer-valued functions return non-negative / negative.

>  
>  /* input.c */
>  int index_from_key(const char *key, size_t key_length);
> diff --git a/monitor/qmp-cmds.c b/monitor/qmp-cmds.c
> index 34f7e75b7b..84f2b74ea8 100644
> --- a/monitor/qmp-cmds.c
> +++ b/monitor/qmp-cmds.c
> @@ -287,6 +287,11 @@ static void qmp_change_vnc(const char *target, bool 
> has_arg, const char *arg,
>          qmp_change_vnc_listen(target, errp);
>      }
>  }
> +
> +void qmp_reload_vnc_cert(Error **errp)
> +{
> +    vnc_display_reload_cert(NULL, errp);
> +}
>  #endif /* !CONFIG_VNC */
>  
>  void qmp_change(const char *device, const char *target,
> diff --git a/qapi/ui.json b/qapi/ui.json
> index d08d72b439..855b1ac007 100644
> --- a/qapi/ui.json
> +++ b/qapi/ui.json
> @@ -1179,3 +1179,21 @@
>  ##
>  { 'command': 'query-display-options',
>    'returns': 'DisplayOptions' }
> +
> +##
> +# @reload-vnc-cert:
> +#
> +# Reload certificates for vnc.
> +#
> +# Returns: nothing
> +#
> +# Since: 5.2

6.0 now.

> +#
> +# Example:
> +#
> +# -> { "execute": "reload-vnc-cert" }
> +# <- { "return": {} }
> +#
> +##
> +{ 'command': 'reload-vnc-cert',
> +  'if': 'defined(CONFIG_VNC)' }

Daniel's objection to another patch that adds a rather specialized QMP
command may apply: "I'm not a fan of adding adhoc new commands for
specific properties."

    From: Daniel P. Berrangé <berrange@redhat.com>
    Subject: Re: [PATCH] vnc: add qmp to support change authz
    Message-ID: <20210107161830.GE1029501@redhat.com>

[...]