MINOR: mux-quic: define config for max-data

Define a new global configuration tune.quic.frontend.max-data. This
allows users to explicitely set the value for the corresponding QUIC TP
initial-max-data, with direct impact on haproxy memory consumption.

doc/configuration.txt

@@ -1691,6 +1691,7 @@ The following keywords are supported in the "global" section :
    - tune.quic.disable-tx-pacing
    - tune.quic.disable-udp-gso
    - tune.quic.frontend.glitches-threshold
+   - tune.quic.frontend.max-data-size
    - tune.quic.frontend.max-idle-timeout
    - tune.quic.frontend.max-streams-bidi
    - tune.quic.frontend.default-max-window-size
@@ -4336,6 +4337,18 @@ tune.quic.frontend.glitches-threshold <number>
 
   See also: fc_glitches
 
+tune.quic.frontend.max-data-size <size>
+  This setting is the hard limit for the number of data bytes in flight over a
+  QUIC frontend connection. It is reused as the value for the initial_max_data
+  transport parameter. It directly impacts the upload bandwidth for the peer
+  depending on the latency and the per-connection memory consumption in
+  haproxy.
+
+  By default, the value is set to 0, which indicates that it must be
+  automatically generated as the product between max-streams-bidi and bufsize.
+  This can be increased for example if a backend application relies on massive
+  uploads over high latency networks.
+
 tune.quic.frontend.max-idle-timeout <timeout>
   Sets the QUIC max_idle_timeout transport parameters in milliseconds for
   frontends which determines the period of time after which a connection silently

include/haproxy/global-t.h

@@ -213,6 +213,7 @@ struct global {
 		unsigned int quic_backend_max_idle_timeout;
 		unsigned int quic_frontend_max_idle_timeout;
 		unsigned int quic_frontend_glitches_threshold;
+		unsigned int quic_frontend_max_data;
 		unsigned int quic_frontend_max_streams_bidi;
 		size_t quic_frontend_max_window_size;
 		unsigned int quic_retry_threshold;

src/cfgparse-quic.c

@@ -282,7 +282,7 @@ static int cfg_parse_quic_tune_setting(char **args, int section_type,
 {
 	unsigned int arg = 0;
 	int prefix_len = strlen("tune.quic.");
-	const char *suffix;
+	const char *suffix, *errptr;
 
 	if (too_many_args(1, args, err, NULL))
 		return -1;
@@ -305,6 +305,15 @@ static int cfg_parse_quic_tune_setting(char **args, int section_type,
 	}
 	else if (strcmp(suffix, "frontend.glitches-threshold") == 0)
 		global.tune.quic_frontend_glitches_threshold = arg;
+	else if (strcmp(suffix, "frontend.max-data-size") == 0) {
+		if ((errptr = parse_size_err(args[1], &arg))) {
+			memprintf(err, "'%s': unexpected charater '%c' in size argument '%s'.",
+			          args[0], *errptr, args[1]);
+			return -1;
+		}
+
+		global.tune.quic_frontend_max_data = arg;
+	}
 	else if (strcmp(suffix, "frontend.max-streams-bidi") == 0)
 		global.tune.quic_frontend_max_streams_bidi = arg;
 	else if (strcmp(suffix, "frontend.default-max-window-size") == 0) {
@@ -411,6 +420,7 @@ static struct cfg_kw_list cfg_kws = {ILH, {
 	{ CFG_GLOBAL, "tune.quic.cc.cubic.min-losses", cfg_parse_quic_tune_setting },
 	{ CFG_GLOBAL, "tune.quic.frontend.conn-tx-buffers.limit", cfg_parse_quic_tune_setting },
 	{ CFG_GLOBAL, "tune.quic.frontend.glitches-threshold", cfg_parse_quic_tune_setting },
+	{ CFG_GLOBAL, "tune.quic.frontend.max-data-size", cfg_parse_quic_tune_setting },
 	{ CFG_GLOBAL, "tune.quic.frontend.max-streams-bidi", cfg_parse_quic_tune_setting },
 	{ CFG_GLOBAL, "tune.quic.frontend.max-idle-timeout", cfg_parse_quic_time },
 	{ CFG_GLOBAL, "tune.quic.frontend.default-max-window-size", cfg_parse_quic_tune_setting },

src/haproxy.c

@@ -196,6 +196,7 @@ struct global global = {
 #ifdef USE_QUIC
 		.quic_backend_max_idle_timeout = QUIC_TP_DFLT_BACK_MAX_IDLE_TIMEOUT,
 		.quic_frontend_max_idle_timeout = QUIC_TP_DFLT_FRONT_MAX_IDLE_TIMEOUT,
+		.quic_frontend_max_data = 0,
 		.quic_frontend_max_streams_bidi = QUIC_TP_DFLT_FRONT_MAX_STREAMS_BIDI,
 		.quic_frontend_max_window_size = QUIC_DFLT_MAX_WINDOW_SIZE,
 		.quic_reorder_ratio = QUIC_DFLT_REORDER_RATIO,

src/quic_tp.c

@@ -67,9 +67,13 @@ void quic_transport_params_init(struct quic_transport_params *p, int server)
 	p->initial_max_streams_bidi = max_streams_bidi;
 	p->initial_max_streams_uni  = max_streams_uni;
 
-	/* Set connection flow-control data limit, automatically calculated
-	 * from max number of concurrently opened streams.
+	/* Set connection flow-control data limit, either from configuration,
+	 * or automatically calculated from max number of concurrently opened
+	 * streams.
 	 */
+	if (global.tune.quic_frontend_max_data)
+		p->initial_max_data = global.tune.quic_frontend_max_data;
+	else
 		p->initial_max_data = max_streams_bidi * stream_rx_bufsz;
 
 	/* Set remote streams flow-control data limit. */