Add new set_client_capabilities() interface to QXLInstance

A new interface

  set_client_capabilities (QXLInstance *qin,
  			   uint8_t client_present,
  			   uint8_t caps[58]);

is added to QXLInstance, and spice server is changed to call it
whenever a client connects or disconnects. The QXL device in response
is expected to update the client capability bits in the ROM of the
device and raise the QXL_INTERRUPT_CLIENT interrupt.

There is a potential race condition in the case where a client
disconnects and a new client with fewer capabilities connects. There
may be commands in the ring that the new client can't handle. This
case is handled by first changing the capability bits, then processing
all commands in the ring, and then start forwarding commands to the
new client. As long as the guest obeys the capability bits, the new
client will never see anything it doesn't understand.

2 files changed, 27 insertions, 0 deletions

diff --git a/server/red_worker.c b/server/red_worker.c
index eee9915d..1e301c45 100644
--- a/server/red_worker.c
+++ b/server/red_worker.c
@@ -10344,6 +10344,23 @@ static void handle_new_display_channel(RedWorker *worker, RedClient *client, Red
     spice_info("jpeg %s", display_channel->enable_jpeg ? "enabled" : "disabled");
     spice_info("zlib-over-glz %s", display_channel->enable_zlib_glz_wrap ? "enabled" : "disabled");
 
+    if (worker->qxl->st->qif->set_client_capabilities) {
+        RedChannelClient *rcc = (RedChannelClient *)dcc;
+        uint8_t caps[58] = { 0 };
+
+#define SET_CAP(a,c)                                                    \
+        ((a)[(c) / 8] |= (1 << ((c) % 8)))
+
+        if (red_channel_client_test_remote_cap(rcc, SPICE_DISPLAY_CAP_SIZED_STREAM))
+            SET_CAP(caps, SPICE_DISPLAY_CAP_SIZED_STREAM);
+        if (red_channel_client_test_remote_cap(rcc, SPICE_DISPLAY_CAP_MONITORS_CONFIG))
+            SET_CAP(caps, SPICE_DISPLAY_CAP_MONITORS_CONFIG);
+        if (red_channel_client_test_remote_cap(rcc, SPICE_DISPLAY_CAP_COMPOSITE))
+            SET_CAP(caps, SPICE_DISPLAY_CAP_COMPOSITE);
+
+        worker->qxl->st->qif->set_client_capabilities(worker->qxl, TRUE, caps);
+    }
+    
     // todo: tune level according to bandwidth
     display_channel->zlib_level = ZLIB_DEFAULT_COMPRESSION_LEVEL;
     red_display_client_init_streams(dcc);
@@ -11198,9 +11215,16 @@ void handle_dev_display_disconnect(void *opaque, void *payload)
 {
     RedWorkerMessageDisplayDisconnect *msg = payload;
     RedChannelClient *rcc = msg->rcc;
+    RedWorker *worker = opaque;
 
     spice_info("disconnect display client");
     spice_assert(rcc);
+
+    if (worker->qxl->st->qif->set_client_capabilities) {
+        uint8_t caps[58] = { 0 };
+        worker->qxl->st->qif->set_client_capabilities(worker->qxl, FALSE, caps);
+    }
+
     red_channel_client_disconnect(rcc);
 }
 
diff --git a/server/spice.h b/server/spice.h
index fdcfbb76..61144076 100644
--- a/server/spice.h
+++ b/server/spice.h
@@ -239,6 +239,9 @@ struct QXLInterface {
     void (*update_area_complete)(QXLInstance *qin, uint32_t surface_id,
                                  struct QXLRect *updated_rects,
                                  uint32_t num_updated_rects);
+    void (*set_client_capabilities)(QXLInstance *qin,
+				    uint8_t client_present,
+				    uint8_t caps[58]);
 };
 
 struct QXLInstance {