MINOR: quic_stats: Add a new stats module for QUIC

This is a very minimalist frontend only stats module with only one gauge for the
QUIC establishing connections count.
diff --git a/Makefile b/Makefile
index 56fd89a..918ddc1 100644
--- a/Makefile
+++ b/Makefile
@@ -637,7 +637,7 @@
                 src/quic_frame.o src/quic_cc.o src/quic_cc_newreno.o src/mux_quic.o \
                 src/cbuf.o src/qpack-dec.o src/qpack-tbl.o src/h3.o src/qpack-enc.o \
                 src/hq_interop.o src/cfgparse-quic.o src/quic_loss.o \
-                src/quic_stream.o
+                src/quic_stream.o src/quic_stats.o
 endif
 
 ifneq ($(USE_LUA),)
diff --git a/include/haproxy/quic_stats-t.h b/include/haproxy/quic_stats-t.h
new file mode 100644
index 0000000..7baed42
--- /dev/null
+++ b/include/haproxy/quic_stats-t.h
@@ -0,0 +1,26 @@
+#ifndef _HAPROXY_QUIC_STATS_T_H
+#define _HAPROXY_QUIC_STATS_T_H
+
+#ifdef USE_QUIC
+#ifndef USE_OPENSSL
+#error "Must define USE_OPENSSL"
+#endif
+
+extern struct stats_module quic_stats_module;
+
+struct quic_counters {
+	long long dropped_pkt;       /* total number of dropped packets */
+	long long retry_sent;        /* total number of Retry sent */
+	long long retry_validated;   /* total number of validated Retry tokens */
+	long long retry_error;       /* total number of Retry token errors */
+	long long conn_opening;      /* total number of connection openings */
+	long long hdshk_fail;        /* total number of handshake failures */
+	/* Streams related counters */
+	long long data_blocked;              /* total number of times DATA_BLOCKED frame was received */
+	long long stream_data_blocked;       /* total number of times STEAM_DATA_BLOCKED frame was received */
+	long long streams_data_blocked_bidi; /* total number of times STREAMS_DATA_BLOCKED_BIDI frame was received */
+	long long streams_data_blocked_uni;  /* total number of times STREAMS_DATA_BLOCKED_UNI frame was received */
+};
+
+#endif /* USE_QUIC */
+#endif /* _HAPROXY_QUIC_STATS_T_H */
diff --git a/src/quic_stats.c b/src/quic_stats.c
new file mode 100644
index 0000000..adc1667
--- /dev/null
+++ b/src/quic_stats.c
@@ -0,0 +1,73 @@
+#include <haproxy/quic_stats-t.h>
+#include <haproxy/stats.h>
+
+enum {
+	QUIC_ST_DROPPED_PACKETS,
+	QUIC_ST_RETRY_SENT,
+	QUIC_ST_RETRY_VALIDATED,
+	QUIC_ST_RETRY_ERRORS,
+	QUIC_ST_CONN_OPENINGS,
+	QUIC_ST_HDSHK_FAILS,
+	/* Stream related counters */
+	QUIC_ST_DATA_BLOCKED,
+	QUIC_ST_STREAM_DATA_BLOCKED,
+	QUIC_ST_STREAMS_DATA_BLOCKED_BIDI,
+	QUIC_ST_STREAMS_DATA_BLOCKED_UNI,
+	QUIC_STATS_COUNT /* must be the last */
+};
+
+static struct name_desc quic_stats[] = {
+	[QUIC_ST_DROPPED_PACKETS]     = { .name = "quic_dropped_pkt",
+	                                  .desc = "Total number of dropped packets" },
+	[QUIC_ST_RETRY_SENT]          = { .name = "quic_retry_sent",
+	                                  .desc = "Total number of Retry sent" },
+	[QUIC_ST_RETRY_VALIDATED]     = { .name = "quic_retry_validated",
+	                                  .desc = "Total number of validated Retry tokens" },
+	[QUIC_ST_RETRY_ERRORS]        = { .name = "quic_retry_error",
+	                                  .desc = "Total number of Retry tokens errors" },
+	[QUIC_ST_CONN_OPENINGS]       = { .name = "quic_conn_opening",
+	                                  .desc = "Total number of connection openings" },
+	[QUIC_ST_HDSHK_FAILS]         = { .name = "quic_hdshk_fail",
+	                                  .desc = "Total number of handshake failures" },
+	/* Streams related counters */
+	[QUIC_ST_DATA_BLOCKED]              = { .name = "quic_data_blocked",
+	                                        .desc = "Total number of times DATA_BLOCKED frame was received" },
+	[QUIC_ST_STREAM_DATA_BLOCKED]       = { .name = "quic_stream_data_blocked",
+	                                        .desc = "Total number of times STREAMS_BLOCKED frame was received" },
+	[QUIC_ST_STREAMS_DATA_BLOCKED_BIDI] = { .name = "quic_streams_data_blocked_bidi",
+	                                        .desc = "Total number of times STREAM_DATA_BLOCKED_BIDI frame was received" },
+	[QUIC_ST_STREAMS_DATA_BLOCKED_UNI]  = { .name = "quic_streams_data_blocked_bidi",
+	                                        .desc = "Total number of times STREAM_DATA_BLOCKED_UNI frame was received" },
+};
+
+struct quic_counters quic_counters;
+
+static void quic_fill_stats(void *data, struct field *stats)
+{
+	struct quic_counters *counters = data;
+
+	stats[QUIC_ST_DROPPED_PACKETS]   = mkf_u64(FN_COUNTER, counters->dropped_pkt);
+	stats[QUIC_ST_RETRY_SENT]        = mkf_u64(FN_COUNTER, counters->retry_sent);
+	stats[QUIC_ST_RETRY_VALIDATED]   = mkf_u64(FN_COUNTER, counters->retry_validated);
+	stats[QUIC_ST_RETRY_ERRORS]      = mkf_u64(FN_COUNTER, counters->retry_error);
+	stats[QUIC_ST_CONN_OPENINGS]     = mkf_u64(FN_GAUGE, counters->conn_opening);
+	stats[QUIC_ST_HDSHK_FAILS]       = mkf_u64(FN_COUNTER, counters->hdshk_fail);
+	/* Streams related counters */
+	stats[QUIC_ST_DATA_BLOCKED]              = mkf_u64(FN_COUNTER, counters->data_blocked);
+	stats[QUIC_ST_STREAM_DATA_BLOCKED]       = mkf_u64(FN_COUNTER, counters->stream_data_blocked);
+	stats[QUIC_ST_STREAMS_DATA_BLOCKED_BIDI] = mkf_u64(FN_COUNTER, counters->streams_data_blocked_bidi);
+	stats[QUIC_ST_STREAMS_DATA_BLOCKED_UNI]  = mkf_u64(FN_COUNTER, counters->streams_data_blocked_uni);
+}
+
+struct stats_module quic_stats_module = {
+	.name          = "quic",
+	.fill_stats    = quic_fill_stats,
+	.stats         = quic_stats,
+	.stats_count   = QUIC_STATS_COUNT,
+	.counters      = &quic_counters,
+	.counters_size = sizeof(quic_counters),
+	.domain_flags  = MK_STATS_PROXY_DOMAIN(STATS_PX_CAP_FE),
+	.clearable     = 1,
+};
+
+INITCALL1(STG_REGISTER, stats_register_module, &quic_stats_module);