GUACAMOLE-288: Add parameter to limit the usage of multiple monitors.

src/protocols/rdp/channels/disp.c

@@ -195,6 +195,14 @@ void guac_rdp_disp_update_size(guac_rdp_disp* disp,
     int height = disp->requested_height;
     int monitors_count = disp->requested_monitors;
 
+    /* Prevent opening too many monitors than allowed */
+    if (settings->max_secondary_monitors + 1 < monitors_count)
+        monitors_count = settings->max_secondary_monitors + 1;
+
+    /* At least one monitor is required */
+    if (monitors_count < 1)
+        monitors_count = 1;
+
     /* Do not update size if no requests have been received */
     if (width == 0 || height == 0)
         return;

src/protocols/rdp/client.c

@@ -42,6 +42,7 @@
 #include <guacamole/mem.h>
 #include <guacamole/recording.h>
 #include <guacamole/rwlock.h>
+#include <guacamole/string.h>
 
 #include <dirent.h>
 #include <errno.h>
@@ -130,6 +131,16 @@ static int guac_rdp_join_pending_handler(guac_client* client) {
     /* Bring user up to date with any registered static channels */
     guac_rdp_pipe_svc_send_pipes(client, broadcast_socket);
 
+    /* Get max secondary monitors */
+    char* max_monitors = guac_mem_alloc(12);
+    guac_itoa(max_monitors,
+            (unsigned int) rdp_client->settings->max_secondary_monitors);
+
+    /* Send current max allowed secondary monitors */
+    guac_client_stream_argv(client, broadcast_socket, "text/plain",
+            "secondary-monitors", max_monitors);
+    guac_mem_free(max_monitors);
+
     /* Synchronize with current display */
     if (rdp_client->display != NULL) {
         guac_display_dup(rdp_client->display, broadcast_socket);

src/protocols/rdp/settings.c

@@ -128,6 +128,7 @@ const char* GUAC_RDP_CLIENT_ARGS[] = {
     "create-recording-path",
     "recording-write-existing",
     "resize-method",
+    "secondary-monitors",
     "enable-audio-input",
     "enable-touch",
     "read-only",
@@ -598,6 +599,12 @@ enum RDP_ARGS_IDX {
      */
     IDX_RESIZE_METHOD,
 
+    /**
+     * The maximum allowed count of secondary monitors.
+     * 0 to disable.
+     */
+    IDX_SECONDARY_MONITORS,
+
     /**
      * "true" if audio input (microphone) should be enabled for the RDP
      * connection, "false" or blank otherwise.
@@ -1234,6 +1241,11 @@ guac_rdp_settings* guac_rdp_parse_args(guac_user* user,
         settings->resize_method = GUAC_RESIZE_NONE;
     }
 
+    /* Maximum secondary monitors (default 0 = disabled) */
+    settings->max_secondary_monitors =
+        guac_user_parse_args_int(user, GUAC_RDP_CLIENT_ARGS, argv,
+                IDX_SECONDARY_MONITORS, 0);
+
     /* RDP Graphics Pipeline enable/disable */
     settings->enable_gfx =
         !guac_user_parse_args_boolean(user, GUAC_RDP_CLIENT_ARGS, argv,

src/protocols/rdp/settings.h

@@ -596,6 +596,11 @@ typedef struct guac_rdp_settings {
      */
     guac_rdp_resize_method resize_method;
 
+    /**
+     * The maximum allowed count of secondary monitors.
+     */
+    int max_secondary_monitors;
+
     /**
      * Whether audio input (microphone) is enabled.
      */