Re: Client server handshake and missing color maps

["Daniel P. Berrange" <dan berrange com>]

On Tue, Apr 22, 2014 at 06:57:27PM +0200, Marco Gidde wrote:
> Hello Daniel, hello list,
>
> I noticed and analyzed a gtk-vnc crash, via vinagre on ubuntu 13.10 and
> gvncviewer.py on an older SUSE release. The client tried to connect to
> an older proprietary VNCserver running on a PLC, RFB version 3.3, maybe
> some RealVNC derivative.
>
> It turned out that the server uses 8bit color depth with a color map and
> does not accept clients which request different color encodings or true
> color. On the other hand the server does not send the color entries
> unless the client explicitly sends the SetPixelFormat message.
>
> There is some code/comment in src/vncdisplay.c:1182:
>
> #if 0
>         /* TigerVNC always sends back the encoding even if
>            unchanged from what the server suggested. This
>            does not appear to matter, so lets save the bytes */
>         memcpy(&fmt, currentFormat, sizeof(fmt));
>         break;
> #else
>         return TRUE;
> #endif
>
> If I activate that code, the client connects successfully, so there
> might be a reason why TigerVNC always sends it :-)

Ok, I'm applying the change

diff --git a/src/vncdisplay.c b/src/vncdisplay.c
index 259c352..d44980b 100644
--- a/src/vncdisplay.c
+++ b/src/vncdisplay.c
@@ -1179,15 +1179,12 @@ static gboolean vnc_display_set_preferred_pixel_format(VncDisplay *display)
         VNC_DEBUG ("Using default colour depth %d (%d bpp) (true color? %d)",
                    currentFormat->depth, currentFormat->bits_per_pixel,
                    currentFormat->true_color_flag);
-#if 0
         /* TigerVNC always sends back the encoding even if
-           unchanged from what the server suggested. This
-           does not appear to matter, so lets save the bytes */
+           unchanged from what the server suggested. This is
+           important with some VNC servers, since they won't
+           otherwise send us the colour map entries */
         memcpy(&fmt, currentFormat, sizeof(fmt));
         break;
-#else
-        return TRUE;
-#endif
 
     case VNC_DISPLAY_DEPTH_COLOR_FULL:
         fmt.depth = 24;

Regards,
Daniel
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