closed_nodes in h2c should define as ngx_uint_t

[zhengjinhuanHW@…]

When h2c->processing exceeds 256 and all streams are released, the h2c->close_nodes in ngx_http_v2_close_stream will roll over and become a small value, eventually causing the node in the h2c->closed queue to be unreusable in the ngx_http_v2_get_node_by_id function, eventually h2c->streams_index contains a lot of invalid nodes, resulting in low performance of ngx_http_v2_get_node_by_id, so the closed_nodes in h2c is recommended to be define as ngx_uint_t instead of unsigned closed_nodes:8;

[Maxim Dounin]

Thanks for the report, this indeed seems possible if ​http2_max_concurrent_streams is set to a large value.

[Maxim Dounin <mdounin@…>]

In 8007:011f5ebdb928/nginx:

HTTP/2: fixed closed_nodes overflow (ticket #1708).

With large http2_max_concurrent_streams or http2_max_concurrent_pushes, more
than 255 ngx_http_v2_node_t structures might be allocated, eventually leading
to h2c->closed_nodes overflow when closing corresponding streams. This will
in turn result in additional allocations in ngx_http_v2_get_node_by_id().

While mostly harmless, it can result in excessive memory usage by a HTTP/2
connection, notably in configurations with many keepalive_requests allowed.
Fix is to use ngx_uint_t for h2c->closed_nodes instead of unsigned:8.

[Maxim Dounin]

Fix committed. Thanks for reporting this.