> On 10 Oct 2023, at 16:29, Maxim Dounin <mdou...@mdounin.ru> wrote:
>
> # HG changeset patch
> # User Maxim Dounin <mdou...@mdounin.ru>
> # Date 1696940019 -10800
> # Tue Oct 10 15:13:39 2023 +0300
> # Node ID cdda286c0f1b4b10f30d4eb6a63fefb9b8708ecc
> # Parent 3db945fda515014d220151046d02f3960bcfca0a
> 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.
>
> 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
> @@ -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 --git a/src/http/v2/ngx_http_v2.h b/src/http/v2/ngx_http_v2.h
> --- a/src/http/v2/ngx_http_v2.h
> +++ b/src/http/v2/ngx_http_v2.h
> @@ -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;
Looks good.
--
Sergey Kandaurov
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