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Re: [PATCH 2 of 3] HTTP/3: allowed QUIC stream connection reuse

Sergey Kandaurov
November 10, 2021 08:02AM
> On 18 Oct 2021, at 15:48, Roman Arutyunyan <arut@nginx.com> wrote:
>
> # HG changeset patch
> # User Roman Arutyunyan <arut@nginx.com>
> # Date 1634561226 -10800
> # Mon Oct 18 15:47:06 2021 +0300
> # Branch quic
> # Node ID 8ae53c592c719af4f3ba47dbd85f78be27aaf7db
> # Parent 8739f475583031399879ef0af2eb5af76008449e
> HTTP/3: allowed QUIC stream connection reuse.
>
> A QUIC stream connection is treated as reusable until first bytes of request
> arrive, which is also when the request object is now allocated. A connection
> closed as a result of draining, is reset with the error code
> H3_REQUEST_REJECTED. Such behavior is allowed by quic-http-34:
>
> Once a request stream has been opened, the request MAY be cancelled
> by either endpoint. Clients cancel requests if the response is no
> longer of interest; servers cancel requests if they are unable to or
> choose not to respond.
>
> When the server cancels a request without performing any application
> processing, the request is considered "rejected." The server SHOULD
> abort its response stream with the error code H3_REQUEST_REJECTED.
>
> The client can treat requests rejected by the server as though they had
> never been sent at all, thereby allowing them to be retried later.
>

Looks good. See below for minor comments.
BTW, if we still hit the worker_connections limit, this leads to
an entire QUIC connection close, but I doubt we can easily improve this.

> diff --git a/src/http/ngx_http_request.c b/src/http/ngx_http_request.c
> --- a/src/http/ngx_http_request.c
> +++ b/src/http/ngx_http_request.c
> @@ -3743,15 +3743,14 @@ ngx_http_free_request(ngx_http_request_t
>
> log->action = "closing request";
>
> - if (r->connection->timedout) {
> + if (r->connection->timedout
> +#if (NGX_HTTP_QUIC)
> + && r->connection->quic == NULL
> +#endif
> + )
> + {
> clcf = ngx_http_get_module_loc_conf(r, ngx_http_core_module);
>
> -#if (NGX_HTTP_V3)
> - if (r->connection->quic) {
> - (void) ngx_quic_reset_stream(r->connection,
> - NGX_HTTP_V3_ERR_GENERAL_PROTOCOL_ERROR);
> - } else
> -#endif
> if (clcf->reset_timedout_connection) {
> linger.l_onoff = 1;
> linger.l_linger = 0;
> @@ -3763,14 +3762,6 @@ ngx_http_free_request(ngx_http_request_t
> "setsockopt(SO_LINGER) failed");
> }
> }
> -
> - } else if (!r->response_sent) {
> -#if (NGX_HTTP_V3)
> - if (r->connection->quic) {
> - (void) ngx_quic_reset_stream(r->connection,
> - NGX_HTTP_V3_ERR_INTERNAL_ERROR);
> - }
> -#endif
> }
>
> /* the various request strings were allocated from r->pool */
> @@ -3830,6 +3821,12 @@ ngx_http_close_connection(ngx_connection
>
> #endif
>
> +#if (NGX_HTTP_V3)
> + if (ngx_http_v3_connection(c)) {
> + ngx_http_v3_reset_connection(c);
> + }
> +#endif
> +
> #if (NGX_STAT_STUB)
> (void) ngx_atomic_fetch_add(ngx_stat_active, -1);
> #endif
> diff --git a/src/http/v3/ngx_http_v3.h b/src/http/v3/ngx_http_v3.h
> --- a/src/http/v3/ngx_http_v3.h
> +++ b/src/http/v3/ngx_http_v3.h
> @@ -90,6 +90,9 @@
> #define ngx_http_v3_shutdown_connection(c, code, reason) \
> ngx_quic_shutdown_connection(c->quic->parent, code, reason)
>
> +#define ngx_http_v3_connection(c) \
> + ((c)->quic ? ngx_http_quic_get_connection(c)->addr_conf->http3 : 0)
> +
>
> typedef struct {
> size_t max_table_capacity;
> @@ -138,6 +141,7 @@ struct ngx_http_v3_session_s {
>
>
> void ngx_http_v3_init(ngx_connection_t *c);
> +void ngx_http_v3_reset_connection(ngx_connection_t *c);
> ngx_int_t ngx_http_v3_init_session(ngx_connection_t *c);
> ngx_int_t ngx_http_v3_check_flood(ngx_connection_t *c);
>
> diff --git a/src/http/v3/ngx_http_v3_request.c b/src/http/v3/ngx_http_v3_request.c
> --- a/src/http/v3/ngx_http_v3_request.c
> +++ b/src/http/v3/ngx_http_v3_request.c
> @@ -10,6 +10,7 @@
> #include <ngx_http.h>
>
>
> +static void ngx_http_v3_wait_request_handler(ngx_event_t *rev);
> static void ngx_http_v3_cleanup_request(void *data);
> static void ngx_http_v3_process_request(ngx_event_t *rev);
> static ngx_int_t ngx_http_v3_process_header(ngx_http_request_t *r,
> @@ -53,12 +54,8 @@ static const struct {
> void
> ngx_http_v3_init(ngx_connection_t *c)
> {
> - size_t size;
> uint64_t n;
> - ngx_buf_t *b;
> ngx_event_t *rev;
> - ngx_pool_cleanup_t *cln;
> - ngx_http_request_t *r;
> ngx_http_connection_t *hc;
> ngx_http_v3_session_t *h3c;
> ngx_http_core_loc_conf_t *clcf;
> @@ -96,7 +93,7 @@ ngx_http_v3_init(ngx_connection_t *c)
> h3c = ngx_http_v3_get_session(c);
>
> if (h3c->goaway) {
> - ngx_quic_reset_stream(c, NGX_HTTP_V3_ERR_REQUEST_REJECTED);
> + c->close = 1;
> ngx_http_close_connection(c);
> return;
> }
> @@ -116,21 +113,57 @@ ngx_http_v3_init(ngx_connection_t *c)
> "reached maximum number of requests");
> }
>
> - cln = ngx_pool_cleanup_add(c->pool, 0);
> - if (cln == NULL) {
> + rev = c->read;
> + rev->handler = ngx_http_v3_wait_request_handler;
> + c->write->handler = ngx_http_empty_handler;
> +
> + if (rev->ready) {
> + rev->handler(rev);
> + return;
> + }
> +
> + cscf = ngx_http_get_module_srv_conf(hc->conf_ctx, ngx_http_core_module);
> +
> + ngx_add_timer(rev, cscf->client_header_timeout);
> + ngx_reusable_connection(c, 1);
> +
> + if (ngx_handle_read_event(rev, 0) != NGX_OK) {
> + ngx_http_close_connection(c);
> + return;
> + }
> +}
> +
> +
> +static void
> +ngx_http_v3_wait_request_handler(ngx_event_t *rev)
> +{
> + size_t size;
> + ssize_t n;
> + ngx_buf_t *b;
> + ngx_connection_t *c;
> + ngx_pool_cleanup_t *cln;
> + ngx_http_request_t *r;
> + ngx_http_connection_t *hc;
> + ngx_http_v3_session_t *h3c;
> + ngx_http_core_srv_conf_t *cscf;
> +
> + c = rev->data;
> +
> + ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 wait request handler");
> +
> + if (rev->timedout) {
> + ngx_log_error(NGX_LOG_INFO, c->log, NGX_ETIMEDOUT, "client timed out");
> + c->timedout = 1;
> ngx_http_close_connection(c);
> return;
> }
>
> - cln->handler = ngx_http_v3_cleanup_request;
> - cln->data = c;
> -
> - h3c->nrequests++;
> -
> - if (h3c->keepalive.timer_set) {
> - ngx_del_timer(&h3c->keepalive);
> + if (c->close) {
> + ngx_http_close_connection(c);
> + return;
> }
>
> + hc = c->data;
> cscf = ngx_http_get_module_srv_conf(hc->conf_ctx, ngx_http_core_module);
>
> size = cscf->client_header_buffer_size;
> @@ -159,8 +192,49 @@ ngx_http_v3_init(ngx_connection_t *c)
> b->end = b->last + size;
> }
>
> + n = c->recv(c, b->last, size);
> +
> + if (n == NGX_AGAIN) {
> +
> + if (!rev->timer_set) {
> + ngx_add_timer(rev, cscf->client_header_timeout);
> + ngx_reusable_connection(c, 1);
> + }
> +
> + if (ngx_handle_read_event(rev, 0) != NGX_OK) {
> + ngx_http_close_connection(c);
> + return;
> + }
> +
> + /*
> + * We are trying to not hold c->buffer's memory for an idle connection.
> + */
> +
> + if (ngx_pfree(c->pool, b->start) == NGX_OK) {
> + b->start = NULL;
> + }
> +
> + return;
> + }
> +
> + if (n == NGX_ERROR) {
> + ngx_http_close_connection(c);
> + return;
> + }
> +
> + if (n == 0) {
> + ngx_log_error(NGX_LOG_INFO, c->log, 0,
> + "client closed connection");
> + ngx_http_close_connection(c);
> + return;
> + }
> +
> + b->last += n;
> +
> c->log->action = "reading client request";
>
> + ngx_reusable_connection(c, 0);
> +
> r = ngx_http_create_request(c);
> if (r == NULL) {
> ngx_http_close_connection(c);
> @@ -171,7 +245,7 @@ ngx_http_v3_init(ngx_connection_t *c)
>
> r->v3_parse = ngx_pcalloc(r->pool, sizeof(ngx_http_v3_parse_t));
> if (r->v3_parse == NULL) {
> - ngx_http_close_connection(c);
> + ngx_http_close_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR);
> return;
> }
>

Since we now defer request initialization until first bytes, that's fine.

> @@ -179,23 +253,59 @@ ngx_http_v3_init(ngx_connection_t *c)
> * cscf->large_client_header_buffers.num;
>
> c->data = r;
> - c->requests = n + 1;
> + c->requests = (c->quic->id >> 2) + 1;
> +
> + cln = ngx_pool_cleanup_add(r->pool, 0);
> + if (cln == NULL) {
> + ngx_http_close_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR);
> + return;
> + }
> +
> + cln->handler = ngx_http_v3_cleanup_request;
> + cln->data = r;
> +
> + h3c = ngx_http_v3_get_session(c);
> + h3c->nrequests++;
> +
> + if (h3c->keepalive.timer_set) {
> + ngx_del_timer(&h3c->keepalive);
> + }
>
> - rev = c->read;
> rev->handler = ngx_http_v3_process_request;
> + ngx_http_v3_process_request(rev);
> +}
>
> - ngx_http_v3_process_request(rev);
> +
> +void
> +ngx_http_v3_reset_connection(ngx_connection_t *c)
> +{
> + if (c->timedout) {
> + ngx_quic_reset_stream(c, NGX_HTTP_V3_ERR_GENERAL_PROTOCOL_ERROR);
> +
> + } else if (c->close) {
> + ngx_quic_reset_stream(c, NGX_HTTP_V3_ERR_REQUEST_REJECTED);
> +
> + } else if (c->requests == 0 || c->error) {
> + ngx_quic_reset_stream(c, NGX_HTTP_V3_ERR_INTERNAL_ERROR);
> + }
> }

The c->requests check looks suspicious,
is it something to catch a not yet initialized request?

>
>
> static void
> ngx_http_v3_cleanup_request(void *data)
> {
> - ngx_connection_t *c = data;
> + ngx_http_request_t *r = data;
>
> + ngx_connection_t *c;
> ngx_http_v3_session_t *h3c;
> ngx_http_core_loc_conf_t *clcf;
>
> + c = r->connection;
> +
> + if (!r->response_sent) {
> + c->error = 1;
> + }
> +
> h3c = ngx_http_v3_get_session(c);
>
> if (--h3c->nrequests == 0) {
> diff --git a/src/http/v3/ngx_http_v3_streams.c b/src/http/v3/ngx_http_v3_streams.c
> --- a/src/http/v3/ngx_http_v3_streams.c
> +++ b/src/http/v3/ngx_http_v3_streams.c
> @@ -49,7 +49,8 @@ ngx_http_v3_init_uni_stream(ngx_connecti
> ngx_http_v3_finalize_connection(c,
> NGX_HTTP_V3_ERR_STREAM_CREATION_ERROR,
> "reached maximum number of uni streams");
> - ngx_http_close_connection(c);
> + c->data = NULL;
> + ngx_http_v3_close_uni_stream(c);
> return;
> }
>
> @@ -57,7 +58,11 @@ ngx_http_v3_init_uni_stream(ngx_connecti
>
> us = ngx_pcalloc(c->pool, sizeof(ngx_http_v3_uni_stream_t));
> if (us == NULL) {
> - ngx_http_close_connection(c);
> + ngx_http_v3_finalize_connection(c,
> + NGX_HTTP_V3_ERR_INTERNAL_ERROR,
> + "memory allocation error");
> + c->data = NULL;
> + ngx_http_v3_close_uni_stream(c);
> return;
> }
>
> @@ -79,12 +84,12 @@ ngx_http_v3_close_uni_stream(ngx_connect
> ngx_http_v3_session_t *h3c;
> ngx_http_v3_uni_stream_t *us;
>
> - us = c->data;
> - h3c = ngx_http_v3_get_session(c);
> -
> ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 close stream");
>
> - if (us->index >= 0) {
> + us = c->data;
> +
> + if (us && us->index >= 0) {
> + h3c = ngx_http_v3_get_session(c);
> h3c->known_streams[us->index] = NULL;
> }
>

Is there any difference after switching to ngx_http_v3_close_uni_stream(),
besides ngx_stat_active now no longer decremented? This itself looks like
a right change, since ngx_stat_active isn't incremented for uni streams.

BTW, we need additional checks to prevent processing new streams
after ngx_http_v3_finalize_connection().

# HG changeset patch
# User Sergey Kandaurov <pluknet@nginx.com>
# Date 1636549164 -10800
# Wed Nov 10 15:59:24 2021 +0300
# Branch quic
# Node ID 924ee879f8befa1ec574d41a3979e5c5c5db8639
# Parent c6386afdd1552105c18ce5c47b4b5cd6f6de8b88
QUIC: stop processing new client streams on quic connection error.

diff --git a/src/event/quic/ngx_event_quic_streams.c b/src/event/quic/ngx_event_quic_streams.c
--- a/src/event/quic/ngx_event_quic_streams.c
+++ b/src/event/quic/ngx_event_quic_streams.c
@@ -314,7 +314,7 @@ ngx_quic_create_client_stream(ngx_connec

qc = ngx_quic_get_connection(c);

- if (qc->shutdown) {
+ if (qc->shutdown || qc->error) {
return NGX_QUIC_STREAM_GONE;
}

@@ -385,7 +385,7 @@ ngx_quic_create_client_stream(ngx_connec
return NULL;
}

- if (qc->shutdown) {
+ if (qc->shutdown || qc->error) {
return NGX_QUIC_STREAM_GONE;
}
}


--
Sergey Kandaurov

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Subject Author Views Posted

[PATCH 0 of 3] HTTP/3 Stream Cancellation and friends

Roman Arutyunyan 233 October 18, 2021 08:50AM

[PATCH 1 of 3] HTTP/3: adjusted QUIC connection finalization

Roman Arutyunyan 45 October 18, 2021 08:50AM

Re: [PATCH 1 of 3] HTTP/3: adjusted QUIC connection finalization

Sergey Kandaurov 36 November 08, 2021 11:26AM

Re: [PATCH 1 of 3] HTTP/3: adjusted QUIC connection finalization

Roman Arutyunyan 68 November 09, 2021 02:34AM

Re: [PATCH 1 of 3] HTTP/3: adjusted QUIC connection finalization

Sergey Kandaurov 34 November 09, 2021 11:02AM

Re: [PATCH 1 of 3] HTTP/3: adjusted QUIC connection finalization

Roman Arutyunyan 24 November 10, 2021 07:22AM

[PATCH 2 of 3] HTTP/3: allowed QUIC stream connection reuse

Roman Arutyunyan 54 October 18, 2021 08:50AM

Re: [PATCH 2 of 3] HTTP/3: allowed QUIC stream connection reuse

Sergey Kandaurov 76 November 10, 2021 08:02AM

Re: [PATCH 2 of 3] HTTP/3: allowed QUIC stream connection reuse

Roman Arutyunyan 63 November 10, 2021 04:44PM

Re: [PATCH 2 of 3] HTTP/3: allowed QUIC stream connection reuse

Sergey Kandaurov 37 November 11, 2021 06:50AM

Re: [PATCH 2 of 3] HTTP/3: allowed QUIC stream connection reuse

Roman Arutyunyan 25 November 15, 2021 07:36AM

Re: [PATCH 2 of 3] HTTP/3: allowed QUIC stream connection reuse

Vladimir Homutov 25 November 16, 2021 04:20AM

Re: [PATCH 2 of 3] HTTP/3: allowed QUIC stream connection reuse

Roman Arutyunyan 102 November 17, 2021 02:14AM

Re: [PATCH 2 of 3] HTTP/3: allowed QUIC stream connection reuse

Vladimir Homutov 50 November 17, 2021 03:24AM

[PATCH 3 of 3] HTTP/3: send Stream Cancellation instruction

Roman Arutyunyan 45 October 18, 2021 08:50AM

Re: [PATCH 3 of 3] HTTP/3: send Stream Cancellation instruction

Sergey Kandaurov 71 November 10, 2021 11:00AM



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