[nginx] HTTP/2: workaround for clients which fail on table size updates.

[Maxim Dounin]

details:   http://hg.nginx.org/nginx/rev/fbb683496705
branches:  
changeset: 7335:fbb683496705
user:      Maxim Dounin <mdounin at mdounin.ru>
date:      Thu Aug 09 20:12:17 2018 +0300
description:
HTTP/2: workaround for clients which fail on table size updates.

There are clients which cannot handle HPACK's dynamic table size updates
as added in 12cadc4669a7 (1.13.6).  Notably, old versions of OkHttp library
are known to fail on it (ticket #1397).

This change makes it possible to work with such clients by only sending
dynamic table size updates in response to SETTINGS_HEADER_TABLE_SIZE.  As
a downside, clients which do not use SETTINGS_HEADER_TABLE_SIZE will
continue to maintain default 4k table.

diffstat:

 src/http/v2/ngx_http_v2.c |  7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diffs (24 lines):

diff --git a/src/http/v2/ngx_http_v2.c b/src/http/v2/ngx_http_v2.c
--- a/src/http/v2/ngx_http_v2.c
+++ b/src/http/v2/ngx_http_v2.c
@@ -270,8 +270,6 @@ ngx_http_v2_init(ngx_event_t *rev)
 
     h2c->frame_size = NGX_HTTP_V2_DEFAULT_FRAME_SIZE;
 
-    h2c->table_update = 1;
-
     h2scf = ngx_http_get_module_srv_conf(hc->conf_ctx, ngx_http_v2_module);
 
     h2c->concurrent_pushes = h2scf->concurrent_pushes;
@@ -2075,6 +2073,11 @@ ngx_http_v2_state_settings_params(ngx_ht
             h2c->concurrent_pushes = ngx_min(value, h2scf->concurrent_pushes);
             break;
 
+        case NGX_HTTP_V2_HEADER_TABLE_SIZE_SETTING:
+
+            h2c->table_update = 1;
+            break;
+
         default:
             break;
         }