[PATCH 1 of 2] QUIC: update stream flow control credit on STREAM_DATA_BLOCKED

[Roman Arutyunyan]

On Wed, Nov 17, 2021 at 10:31:01AM +0300, Roman Arutyunyan wrote:
> # HG changeset patch
> # User Roman Arutyunyan <arut at nginx.com>
> # Date 1637133234 -10800
> #      Wed Nov 17 10:13:54 2021 +0300
> # Branch quic
> # Node ID 4e3a7fc0533192f51a01042a1e9dd2b595881420
> # Parent  4ad8fc79cb33257c928a9098a87324b350576551
> 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 +1599,44 @@ 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_quic_frame_t       *frame;
> +    ngx_quic_stream_t      *qs;
> +    ngx_quic_connection_t  *qc;
> +
> +    qs = c->quic;
> +    qc = ngx_quic_get_connection(qs->parent);
> +
> +    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(c);

The argument should be "pc":

    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)
>  {
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-- 
Roman Arutyunyan