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.
This commit is contained in:
Maxim Dounin 2023-10-10 15:13:39 +03:00
parent c37fdcdd1e
commit 6ceef192e7
2 changed files with 17 additions and 0 deletions

View File

@ -347,6 +347,7 @@ ngx_http_v2_read_handler(ngx_event_t *rev)
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_connection_t *h2c, u_char *pos,
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_connection_t *h2c, u_char *pos,
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);
}

View File

@ -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;