[PATCH 1 of 4] HTTP/2: emit new frames only after applying all SETTINGS params

[Valentin V. Bartenev]

On Monday 24 April 2017 15:48:23 Piotr Sikora via nginx-devel wrote:
> # HG changeset patch
> # User Piotr Sikora <piotrsikora at google.com>
> # Date 1493073310 25200
> #      Mon Apr 24 15:35:10 2017 -0700
> # Node ID 07adf0a7009c3244de4b795c0c06927f4316a87f
> # Parent  2c4dbcd6f2e4c9c2a1eb8dc1f0d39c99975ae208
> HTTP/2: emit new frames only after applying all SETTINGS params.
> 
> Previously, new frames could be emitted in the middle of applying
> new (and already acknowledged) SETTINGS params, which is illegal.
> 
> Signed-off-by: Piotr Sikora <piotrsikora at google.com>
> 
> diff -r 2c4dbcd6f2e4 -r 07adf0a7009c src/http/v2/ngx_http_v2.c
> --- a/src/http/v2/ngx_http_v2.c
> +++ b/src/http/v2/ngx_http_v2.c
> @@ -1982,7 +1982,9 @@ static u_char *
>  ngx_http_v2_state_settings_params(ngx_http_v2_connection_t *h2c, u_char *pos,
>      u_char *end)
>  {
> -    ngx_uint_t  id, value;
> +    ngx_uint_t  id, value, adjustment;

The new initial window size can be lower than the previous one,
so the difference can be negative (that's why the delta parameter
of ngx_http_v2_adjust_windows() is ssize_t).

Please consider the patch below:

diff -r 00015416ae79 src/http/v2/ngx_http_v2.c
--- a/src/http/v2/ngx_http_v2.c Mon Apr 24 15:35:10 2017 -0700
+++ b/src/http/v2/ngx_http_v2.c Thu Jun 01 17:45:37 2017 +0300
@@ -1969,7 +1969,8 @@ static u_char *
 ngx_http_v2_state_settings_params(ngx_http_v2_connection_t *h2c, u_char *pos,
     u_char *end)
 {
-    ngx_uint_t  id, value, adjustment;
+    ssize_t     window_delta;
+    ngx_uint_t  id, value;
 
     adjustment = 0;
 
@@ -1997,7 +1998,8 @@ ngx_http_v2_state_settings_params(ngx_ht
                                                   NGX_HTTP_V2_FLOW_CTRL_ERROR);
             }
 
-            adjustment = value - h2c->init_window;
+            window_delta = value - h2c->init_window;
+
             h2c->init_window = value;
             break;
 
@@ -2024,8 +2026,8 @@ ngx_http_v2_state_settings_params(ngx_ht
         pos += NGX_HTTP_V2_SETTINGS_PARAM_SIZE;
     }
 
-    if (adjustment) {
-        if (ngx_http_v2_adjust_windows(h2c, adjustment) != NGX_OK) {
+    if (window_delta) {
+        if (ngx_http_v2_adjust_windows(h2c, window_delta) != NGX_OK) {
             return ngx_http_v2_connection_error(h2c,
                                                 NGX_HTTP_V2_INTERNAL_ERROR);
         }


  wbr, Valentin V. Bartenev