channel-usbredir: drop isoc packets on low bandwidth

When channel wants to send much more data then the wire can handle, the
queue grows fast. This patch does not limit the queue growth but
introduces an internal API to check if queue size is too big.

This internal API is used in usbredir_buffered_output_size_callback
which is called before any isoc pacaket is queued in usbredir. The
usbredir implements the logic to:
 - only drop isoc packets
 - while dropping packtes does still give us video frames from and above
   10fps streams

An easy way to test locally is sharing and webcam and with tc:
    tc qdisc add dev lo root netem delay 100ms
    tc qdisc change dev lo root netem delay 1000ms
    tc qdisc del dev lo root netem

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1264156

1 files changed, 2 insertions, 0 deletions

diff --git a/src/spice-channel-priv.h b/src/spice-channel-priv.h
index 436a521..4b2d1e6 100644
--- a/src/spice-channel-priv.h
+++ b/src/spice-channel-priv.h
@@ -111,6 +111,7 @@ struct _SpiceChannelPrivate {
     gboolean                    xmit_queue_blocked;
     STATIC_MUTEX                xmit_queue_lock;
     guint                       xmit_queue_wakeup_id;
+    guint64                     xmit_queue_size;
 
     char                        name[16];
     enum spice_channel_state    state;
@@ -171,6 +172,7 @@ void spice_channel_wakeup(SpiceChannel *channel, gboolean cancel);
 
 SpiceSession* spice_channel_get_session(SpiceChannel *channel);
 enum spice_channel_state spice_channel_get_state(SpiceChannel *channel);
+guint64 spice_channel_get_queue_size (SpiceChannel *channel);
 
 /* coroutine context */
 typedef void (*handler_msg_in)(SpiceChannel *channel, SpiceMsgIn *msg, gpointer data);