# HG changeset patch
# User Roman Arutyunyan <arut@nginx.com>
# Date 1637179658 -10800
# Node ID e8cbbfabe5473c47293bdb1d78e98d8a4ea54f13
# Parent  122bfa14465b8ce99c272cc499a6846e87ae8dec
QUIC: update stream flow control credit on STREAM_DATA_BLOCKED.

Previously, after receiving STREAM_DATA_BLOCKED, current flow control limit
was sent to client.  Now, if the limit can be updated to the full window size,
it is updated and the new value is sent to client, otherwise nothing is sent.

The change lets client update flow control credit on demand.  Also, it saves
traffic by not sending MAX_STREAM_DATA with the same value twice.

diff --git a/src/event/quic/ngx_event_quic_streams.c b/src/event/quic/ngx_event_quic_streams.c
--- a/src/event/quic/ngx_event_quic_streams.c
+++ b/src/event/quic/ngx_event_quic_streams.c
@@ -31,6 +31,7 @@ static size_t ngx_quic_max_stream_flow(n
 static void ngx_quic_stream_cleanup_handler(void *data);
 static ngx_int_t ngx_quic_control_flow(ngx_connection_t *c, uint64_t last);
 static ngx_int_t ngx_quic_update_flow(ngx_connection_t *c, uint64_t last);
+static ngx_int_t ngx_quic_update_max_stream_data(ngx_connection_t *c);
 
 
 ngx_connection_t *
@@ -1190,8 +1191,6 @@ ngx_int_t
 ngx_quic_handle_stream_data_blocked_frame(ngx_connection_t *c,
     ngx_quic_header_t *pkt, ngx_quic_stream_data_blocked_frame_t *f)
 {
-    uint64_t                limit;
-    ngx_quic_frame_t       *frame;
     ngx_quic_stream_t      *qs;
     ngx_quic_connection_t  *qc;
 
@@ -1217,29 +1216,10 @@ ngx_quic_handle_stream_data_blocked_fram
             return NGX_OK;
         }
 
-        limit = qs->recv_max_data;
-
-        if (ngx_quic_init_stream(qs) != NGX_OK) {
-            return NGX_ERROR;
-        }
-
-    } else {
-        limit = qs->recv_max_data;
+        return ngx_quic_init_stream(qs);
     }
 
-    frame = ngx_quic_alloc_frame(c);
-    if (frame == NULL) {
-        return NGX_ERROR;
-    }
-
-    frame->level = pkt->level;
-    frame->type = NGX_QUIC_FT_MAX_STREAM_DATA;
-    frame->u.max_stream_data.id = f->id;
-    frame->u.max_stream_data.limit = limit;
-
-    ngx_quic_queue_frame(qc, frame);
-
-    return NGX_OK;
+    return ngx_quic_update_max_stream_data(qs->connection);
 }
 
 
@@ -1587,22 +1567,9 @@ ngx_quic_update_flow(ngx_connection_t *c
     if (!rev->pending_eof && !rev->error
         && qs->recv_max_data <= qs->recv_offset + qs->recv_window / 2)
     {
-        qs->recv_max_data = qs->recv_offset + qs->recv_window;
-
-        ngx_log_debug1(NGX_LOG_DEBUG_EVENT, c->log, 0,
-                       "quic flow update msd:%uL", qs->recv_max_data);
-
-        frame = ngx_quic_alloc_frame(pc);
-        if (frame == NULL) {
+        if (ngx_quic_update_max_stream_data(c) != NGX_OK) {
             return NGX_ERROR;
         }
-
-        frame->level = ssl_encryption_application;
-        frame->type = NGX_QUIC_FT_MAX_STREAM_DATA;
-        frame->u.max_stream_data.id = qs->id;
-        frame->u.max_stream_data.limit = qs->recv_max_data;
-
-        ngx_quic_queue_frame(qc, frame);
     }
 
     qc->streams.recv_offset += len;
@@ -1632,6 +1599,46 @@ ngx_quic_update_flow(ngx_connection_t *c
 }
 
 
+static ngx_int_t
+ngx_quic_update_max_stream_data(ngx_connection_t *c)
+{
+    uint64_t                recv_max_data;
+    ngx_connection_t       *pc;
+    ngx_quic_frame_t       *frame;
+    ngx_quic_stream_t      *qs;
+    ngx_quic_connection_t  *qc;
+
+    qs = c->quic;
+    pc = qs->parent;
+    qc = ngx_quic_get_connection(pc);
+
+    recv_max_data = qs->recv_offset + qs->recv_window;
+
+    if (qs->recv_max_data == recv_max_data) {
+        return NGX_OK;
+    }
+
+    qs->recv_max_data = recv_max_data;
+
+    ngx_log_debug1(NGX_LOG_DEBUG_EVENT, c->log, 0,
+                   "quic flow update msd:%uL", qs->recv_max_data);
+
+    frame = ngx_quic_alloc_frame(pc);
+    if (frame == NULL) {
+        return NGX_ERROR;
+    }
+
+    frame->level = ssl_encryption_application;
+    frame->type = NGX_QUIC_FT_MAX_STREAM_DATA;
+    frame->u.max_stream_data.id = qs->id;
+    frame->u.max_stream_data.limit = qs->recv_max_data;
+
+    ngx_quic_queue_frame(qc, frame);
+
+    return NGX_OK;
+}
+
+
 ngx_int_t
 ngx_quic_handle_read_event(ngx_event_t *rev, ngx_uint_t flags)
 {