nginx: stop HTTP/3 steam read when skipping request data

There's a few cases where nginx wants to skip over request payload data
but not immediately finalize the request. For HTTP/3, there is potential
for nginx to get into a tight loop when processing the client
connection. This is because quiche's `poll()` API always presents DATA
events for open streams wth buffered data. When the skip flag is set to
true, nginx does not drain quiche's buffer, resulting in repeated DATA
events for the same thing as long as the stream is active.

In most cases when the skip flag is set, the request is finalized
immediately. This change covers the remaining cases where the stream is
not finalized immediately. We now use `quiche_conn_stream_shutdown()` to
stop the read part of the stream, which effectively discards quiche's
buffering for the stream and prevents endless DATA events. Shutting only
the read side allows any pending response data to be sent but prevents
skippable request data from tying up the connection.

1 files changed, 47 insertions, 13 deletions

diff --git a/extras/nginx/nginx-1.16.patch b/extras/nginx/nginx-1.16.patch
index a9b5b248..105d8d01 100644
--- a/extras/nginx/nginx-1.16.patch
+++ b/extras/nginx/nginx-1.16.patch
@@ -1,4 +1,4 @@
-From 8b6bc45dd698ec1686fb281481cf16b638c2d6d1 Mon Sep 17 00:00:00 2001
+From 1372db755f3ecda39a4baee7978fa150d7053376 Mon Sep 17 00:00:00 2001
 From: Alessandro Ghedini <alessandro@cloudflare.com>
 Date: Thu, 22 Oct 2020 12:28:02 +0100
 Subject: [PATCH] Initial QUIC and HTTP/3 implementation using quiche
@@ -24,14 +24,14 @@ Subject: [PATCH] Initial QUIC and HTTP/3 implementation using quiche
  src/http/ngx_http_core_module.h         |    3 +
  src/http/ngx_http_request.c             |  140 +-
  src/http/ngx_http_request.h             |    3 +
- src/http/ngx_http_request_body.c        |   29 +
+ src/http/ngx_http_request_body.c        |   33 +
  src/http/ngx_http_upstream.c            |   13 +
- src/http/v3/ngx_http_v3.c               | 2310 +++++++++++++++++++++++
- src/http/v3/ngx_http_v3.h               |   77 +
+ src/http/v3/ngx_http_v3.c               | 2339 +++++++++++++++++++++++
+ src/http/v3/ngx_http_v3.h               |   78 +
  src/http/v3/ngx_http_v3_filter_module.c |   68 +
  src/http/v3/ngx_http_v3_module.c        |  286 +++
  src/http/v3/ngx_http_v3_module.h        |   34 +
- 27 files changed, 3788 insertions(+), 11 deletions(-)
+ 27 files changed, 3822 insertions(+), 11 deletions(-)
  create mode 100644 auto/lib/quiche/conf
  create mode 100644 auto/lib/quiche/make
  create mode 100644 src/event/ngx_event_quic.c
@@ -1475,7 +1475,7 @@ index fce70efe6..8ac19658c 100644
      ngx_http_log_handler_pt           log_handler;
  
 diff --git a/src/http/ngx_http_request_body.c b/src/http/ngx_http_request_body.c
-index c4f092e59..2f8514418 100644
+index c4f092e59..d6d85a30f 100644
 --- a/src/http/ngx_http_request_body.c
 +++ b/src/http/ngx_http_request_body.c
 @@ -85,6 +85,13 @@ ngx_http_read_client_request_body(ngx_http_request_t *r,
@@ -1511,13 +1511,17 @@ index c4f092e59..2f8514418 100644
      if (r->connection->read->timedout) {
          r->connection->timedout = 1;
          return NGX_HTTP_REQUEST_TIME_OUT;
-@@ -525,6 +544,13 @@ ngx_http_discard_request_body(ngx_http_request_t *r)
+@@ -525,6 +544,17 @@ ngx_http_discard_request_body(ngx_http_request_t *r)
      }
  #endif
  
 +#if (NGX_HTTP_V3)
 +    if (r->qstream) {
 +        r->qstream->skip_data = 1;
++
++        /* disable stream read to avoid pointless data events */
++        ngx_http_v3_stop_stream_read(r->qstream, 0);
++
 +        return NGX_OK;
 +    }
 +#endif
@@ -1525,7 +1529,7 @@ index c4f092e59..2f8514418 100644
      if (ngx_http_test_expect(r) != NGX_OK) {
          return NGX_HTTP_INTERNAL_SERVER_ERROR;
      }
-@@ -808,6 +834,9 @@ ngx_http_test_expect(ngx_http_request_t *r)
+@@ -808,6 +838,9 @@ ngx_http_test_expect(ngx_http_request_t *r)
          || r->http_version < NGX_HTTP_VERSION_11
  #if (NGX_HTTP_V2)
          || r->stream != NULL
@@ -1568,10 +1572,10 @@ index a7391d09a..398af2797 100644
      if (ngx_event_flags & NGX_USE_KQUEUE_EVENT) {
 diff --git a/src/http/v3/ngx_http_v3.c b/src/http/v3/ngx_http_v3.c
 new file mode 100644
-index 000000000..61e35c96a
+index 000000000..896e26af6
 --- /dev/null
 +++ b/src/http/v3/ngx_http_v3.c
-@@ -0,0 +1,2310 @@
+@@ -0,0 +1,2339 @@
 +
 +/*
 + * Copyright (C) Cloudflare, Inc.
@@ -2881,6 +2885,9 @@ index 000000000..61e35c96a
 +
 +    if (rb->buf == NULL) {
 +        stream->skip_data = 1;
++
++        /* disable stream read to avoid pointless data events */
++        ngx_http_v3_stop_stream_read(stream, 0);
 +        return NGX_HTTP_INTERNAL_SERVER_ERROR;
 +    }
 +
@@ -3149,6 +3156,9 @@ index 000000000..61e35c96a
 +        stream->skip_data = 1;
 +        fc->timedout = 1;
 +
++        /* disable stream read to avoid pointless data events */
++        ngx_http_v3_stop_stream_read(stream, 0);
++
 +        return NGX_HTTP_REQUEST_TIME_OUT;
 +    }
 +
@@ -3161,6 +3171,10 @@ index 000000000..61e35c96a
 +
 +    if (rc != NGX_OK) {
 +        stream->skip_data = 1;
++
++        /* disable stream read to avoid pointless data events */
++        ngx_http_v3_stop_stream_read(stream, 0);
++
 +        return rc;
 +    }
 +
@@ -3798,6 +3812,25 @@ index 000000000..61e35c96a
 +    ngx_http_v3_close_stream(r->qstream, 0);
 +}
 +
++void
++ngx_http_v3_stop_stream_read(ngx_http_v3_stream_t *stream, ngx_int_t rc)
++{
++    ngx_http_v3_connection_t  *h3c;
++
++    if (!stream) {
++        return;
++    }
++
++    h3c = stream->connection;
++
++    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, h3c->connection->log, 0,
++                   "http3 stream shutdown read %ui", stream->id);
++
++    quiche_conn_stream_shutdown(h3c->connection->quic->conn,
++                                stream->id,
++                                QUICHE_SHUTDOWN_READ, rc);
++}
++
 +
 +static void
 +ngx_http_v3_finalize_connection(ngx_http_v3_connection_t *h3c,
@@ -3884,10 +3917,10 @@ index 000000000..61e35c96a
 +}
 diff --git a/src/http/v3/ngx_http_v3.h b/src/http/v3/ngx_http_v3.h
 new file mode 100644
-index 000000000..45a55b898
+index 000000000..52920b781
 --- /dev/null
 +++ b/src/http/v3/ngx_http_v3.h
-@@ -0,0 +1,77 @@
+@@ -0,0 +1,78 @@
 +
 +/*
 + * Copyright (C) Cloudflare, Inc.
@@ -3962,6 +3995,7 @@ index 000000000..45a55b898
 +ngx_int_t ngx_http_v3_send_response(ngx_http_request_t *r);
 +
 +void ngx_http_v3_close_stream(ngx_http_v3_stream_t *stream, ngx_int_t rc);
++void ngx_http_v3_stop_stream_read(ngx_http_v3_stream_t *stream, ngx_int_t rc);
 +
 +
 +#endif /* _NGX_HTTP_V3_H_INCLUDED_ */
@@ -4372,5 +4406,5 @@ index 000000000..72e189def
 +
 +#endif /* _NGX_HTTP_V3_MODULE_H_INCLUDED_ */
 -- 
-2.29.2
+2.30.0