1 files changed, 12 insertions, 12 deletions

diff --git a/src/core/transport/chttp2_transport.c b/src/core/transport/chttp2_transport.c
index fbd9d8a146..39297c37a3 100644
--- a/src/core/transport/chttp2_transport.c
+++ b/src/core/transport/chttp2_transport.c
@@ -276,8 +276,8 @@ struct transport {
 struct stream {
   gpr_uint32 id;
 
-  gpr_uint32 outgoing_window;
   gpr_uint32 incoming_window;
+  gpr_int64 outgoing_window;
   /* when the application requests writes be closed, the write_closed is
      'queued'; when the close is flow controlled into the send path, we are
      'sending' it; when the write has been performed it is 'sent' */
@@ -852,7 +852,8 @@ static int prepare_write(transport *t) {
 
   /* for each stream that's become writable, frame it's data (according to
      available window sizes) and add to the output buffer */
-  while (t->outgoing_window && (s = stream_list_remove_head(t, WRITABLE))) {
+  while (t->outgoing_window && (s = stream_list_remove_head(t, WRITABLE)) &&
+         s->outgoing_window > 0) {
     window_delta = grpc_chttp2_preencode(
         s->outgoing_sopb.ops, &s->outgoing_sopb.nops,
         GPR_MIN(t->outgoing_window, s->outgoing_window), &s->writing_sopb);
@@ -867,7 +868,7 @@ static int prepare_write(transport *t) {
 
     /* if there are still writes to do and the stream still has window
        available, then schedule a further write */
-    if (s->outgoing_sopb.nops && s->outgoing_window) {
+    if (s->outgoing_sopb.nops && s->outgoing_window > 0) {
       GPR_ASSERT(!t->outgoing_window);
       stream_list_add_tail(t, s, WRITABLE);
     }
@@ -1430,8 +1431,8 @@ static int init_frame_parser(transport *t) {
   }
 }
 
-static int is_window_update_legal(gpr_uint32 window_update, gpr_uint32 window) {
-  return window_update < MAX_WINDOW - window;
+static int is_window_update_legal(gpr_int64 window_update, gpr_int64 window) {
+  return window + window_update < MAX_WINDOW;
 }
 
 static int parse_frame_slice(transport *t, gpr_slice slice, int is_last) {
@@ -1488,12 +1489,11 @@ static int parse_frame_slice(transport *t, gpr_slice slice, int is_last) {
       if (st.initial_window_update) {
         for (i = 0; i < t->stream_map.count; i++) {
           stream *s = (stream*)(t->stream_map.values[i]);
-          /* TODO there are other scenarios */
-          if (s->outgoing_window == 0) {
-            s->outgoing_window += st.initial_window_update;
-            if (s->outgoing_sopb.nops) {
-                stream_list_join(t, s, WRITABLE);
-            }
+          int was_window_empty = s->outgoing_window <= 0;
+          s->outgoing_window += st.initial_window_update;
+          if (was_window_empty && s->outgoing_window > 0 &&
+              s->outgoing_sopb.nops > 0) {
+            stream_list_join(t, s, WRITABLE);
           }
         }
       }
@@ -1502,7 +1502,7 @@ static int parse_frame_slice(transport *t, gpr_slice slice, int is_last) {
           /* if there was a stream id, this is for some stream */
           stream *s = lookup_stream(t, t->incoming_stream_id);
           if (s) {
-            int was_window_empty = s->outgoing_window == 0;
+            int was_window_empty = s->outgoing_window <= 0;
             if (!is_window_update_legal(st.window_update, s->outgoing_window)) {
               cancel_stream(t, s, grpc_chttp2_http2_error_to_grpc_status(
                                       GRPC_CHTTP2_FLOW_CONTROL_ERROR),