Hi

On Thu, Dec 3, 2020 at 3:12 PM Gerd Hoffmann <kra...@redhat.com> wrote:

> The vnc server should send desktop resize notifications unconditionally
> on a new client connect, for feature negotiation reasons.  Add a bool
> flag to vnc_desktop_resize() to force sending the message even in case
> there is no size change.
>
> Signed-off-by: Gerd Hoffmann <kra...@redhat.com>
>

In principle, this looks harmless. But the spec says:

"The server should only send a *DesktopSize* pseudo-rectangle when an
actual change of the framebuffer dimensions has occurred. Some clients
respond to a *DesktopSize* pseudo-rectangle in a way that could send the
system into an infinite loop if the server sent out the pseudo-rectangle
for anything other than an actual change."
(
https://github.com/rfbproto/rfbproto/blob/master/rfbproto.rst#server-semantics
)

I can't say if sending desktop resize during the initial SetEncoding phase
is really compliant with the specification. Also, it's unclear to me if the
client is allowed to SetEncoding multiple times (in which there would be no
dimension change occurring).

What did you fix with this? Is it worth a clarification in the
specification?

thanks

---
>  ui/vnc.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/ui/vnc.c b/ui/vnc.c
> index 247e80d8f5c8..bdaf384f71a4 100644
> --- a/ui/vnc.c
> +++ b/ui/vnc.c
> @@ -664,13 +664,14 @@ void vnc_framebuffer_update(VncState *vs, int x, int
> y, int w, int h,
>  }
>
>
> -static void vnc_desktop_resize(VncState *vs)
> +static void vnc_desktop_resize(VncState *vs, bool force)
>  {
>      if (vs->ioc == NULL || !vnc_has_feature(vs, VNC_FEATURE_RESIZE)) {
>          return;
>      }
>      if (vs->client_width == pixman_image_get_width(vs->vd->server) &&
> -        vs->client_height == pixman_image_get_height(vs->vd->server)) {
> +        vs->client_height == pixman_image_get_height(vs->vd->server) &&
> +        !force) {
>          return;
>      }
>
> @@ -800,7 +801,7 @@ static void vnc_dpy_switch(DisplayChangeListener *dcl,
>
>      QTAILQ_FOREACH(vs, &vd->clients, next) {
>          vnc_colordepth(vs);
> -        vnc_desktop_resize(vs);
> +        vnc_desktop_resize(vs, false);
>          if (vs->vd->cursor) {
>              vnc_cursor_define(vs);
>          }
> @@ -2143,7 +2144,7 @@ static void set_encodings(VncState *vs, int32_t
> *encodings, size_t n_encodings)
>              break;
>          }
>      }
> -    vnc_desktop_resize(vs);
> +    vnc_desktop_resize(vs, true);
>      check_pointer_type_change(&vs->mouse_mode_notifier, NULL);
>      vnc_led_state_change(vs);
>      if (vs->vd->cursor) {
> --
> 2.27.0
>
>
>

-- 
Marc-André Lureau

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