details: https://hg.nginx.org/nginx/rev/cdda286c0f1b
branches:
changeset: 9165:cdda286c0f1b
user: Maxim Dounin <mdounin@mdounin.ru>
date: Tue Oct 10 15:13:39 2023 +0300
description:
HTTP/2: per-iteration stream handling limit.

To ensure that attempts to flood servers with many streams are detected
early, a limit of no more than 2 * max_concurrent_streams new streams per one
event loop iteration was introduced. This limit is applied even if
max_concurrent_streams is not yet reached - for example, if corresponding
streams are handled synchronously or reset.

Further, refused streams are now limited to maximum of max_concurrent_streams
and 100, similarly to priority_limit initial value, providing some tolerance
to clients trying to open several streams at the connection start, yet
low tolerance to flooding attempts.

diffstat:

src/http/v2/ngx_http_v2.c | 15 +++++++++++++++
src/http/v2/ngx_http_v2.h | 2 ++
2 files changed, 17 insertions(+), 0 deletions(-)

diffs (51 lines):

diff -r 3db945fda515 -r cdda286c0f1b src/http/v2/ngx_http_v2.c
--- a/src/http/v2/ngx_http_v2.c Fri Sep 22 19:23:57 2023 +0400
+++ b/src/http/v2/ngx_http_v2.c Tue Oct 10 15:13:39 2023 +0300
@@ -347,6 +347,7 @@ ngx_http_v2_read_handler(ngx_event_t *re
ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http2 read handler");

h2c->blocked = 1;
+ h2c->new_streams = 0;

if (c->close) {
c->close = 0;
@@ -1284,6 +1285,14 @@ ngx_http_v2_state_headers(ngx_http_v2_co
goto rst_stream;
}

+ if (h2c->new_streams++ >= 2 * h2scf->concurrent_streams) {
+ ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
+ "client sent too many streams at once");
+
+ status = NGX_HTTP_V2_REFUSED_STREAM;
+ goto rst_stream;
+ }
+
if (!h2c->settings_ack
&& !(h2c->state.flags & NGX_HTTP_V2_END_STREAM_FLAG)
&& h2scf->preread_size < NGX_HTTP_V2_DEFAULT_WINDOW)
@@ -1349,6 +1358,12 @@ ngx_http_v2_state_headers(ngx_http_v2_co

rst_stream:

+ if (h2c->refused_streams++ > ngx_max(h2scf->concurrent_streams, 100)) {
+ ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
+ "client sent too many refused streams");
+ return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_NO_ERROR);
+ }
+
if (ngx_http_v2_send_rst_stream(h2c, h2c->state.sid, status) != NGX_OK) {
return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_INTERNAL_ERROR);
}
diff -r 3db945fda515 -r cdda286c0f1b src/http/v2/ngx_http_v2.h
--- a/src/http/v2/ngx_http_v2.h Fri Sep 22 19:23:57 2023 +0400
+++ b/src/http/v2/ngx_http_v2.h Tue Oct 10 15:13:39 2023 +0300
@@ -131,6 +131,8 @@ struct ngx_http_v2_connection_s {
ngx_uint_t processing;
ngx_uint_t frames;
ngx_uint_t idle;
+ ngx_uint_t new_streams;
+ ngx_uint_t refused_streams;
ngx_uint_t priority_limit;

size_t send_window;
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