From 9acce8a82abec4b88630c1d05a18a44ebb051ecb Mon Sep 17 00:00:00 2001
From: Matthijs Mekking <matthijs@isc.org>
Date: Thu, 19 Aug 2021 13:38:51 +0200
Subject: [PATCH] Add a function isc_stats_resize

Add a new function to resize the number of counters in a statistics
counter structure. This will be needed when we keep track of DNSSEC
sign statistics and new keys are introduced due to a rollover.
---
 lib/isc/include/isc/stats.h | 11 +++++++++++
 lib/isc/stats.c             | 32 ++++++++++++++++++++++++++++++++
 lib/isc/tests/stats_test.c  | 17 +++++++++++++++++
 3 files changed, 60 insertions(+)

diff --git a/lib/isc/include/isc/stats.h b/lib/isc/include/isc/stats.h
index c2ab4e6c03..f57aa1a96f 100644
--- a/lib/isc/include/isc/stats.h
+++ b/lib/isc/include/isc/stats.h
@@ -238,6 +238,17 @@ isc_stats_get_counter(isc_stats_t *stats, isc_statscounter_t counter);
  *	on creation.
  */
 
+void
+isc_stats_resize(isc_stats_t **stats, int ncounters);
+/*%<
+ * Resize a statistics counter structure of general type. The new set of
+ * counters are indexed by an ID between 0 and ncounters -1.
+ *
+ * Requires:
+ *\li	'stats' is a valid isc_stats_t.
+ *\li	'ncounters' is a non-zero positive number.
+ */
+
 ISC_LANG_ENDDECLS
 
 #endif /* ISC_STATS_H */
diff --git a/lib/isc/stats.c b/lib/isc/stats.c
index ab599b18af..6297946cb2 100644
--- a/lib/isc/stats.c
+++ b/lib/isc/stats.c
@@ -162,3 +162,35 @@ isc_stats_get_counter(isc_stats_t *stats, isc_statscounter_t counter) {
 
 	return (atomic_load_acquire(&stats->counters[counter]));
 }
+
+void
+isc_stats_resize(isc_stats_t **statsp, int ncounters) {
+	isc_stats_t *stats;
+	size_t counters_alloc_size;
+	isc__atomic_statcounter_t *newcounters;
+
+	REQUIRE(statsp != NULL && *statsp != NULL);
+	REQUIRE(ISC_STATS_VALID(*statsp));
+	REQUIRE(ncounters > 0);
+
+	stats = *statsp;
+	if (stats->ncounters >= ncounters) {
+		/* We already have enough counters. */
+		return;
+	}
+
+	/* Grow number of counters. */
+	counters_alloc_size = sizeof(isc__atomic_statcounter_t) * ncounters;
+	newcounters = isc_mem_get(stats->mctx, counters_alloc_size);
+	for (int i = 0; i < ncounters; i++) {
+		atomic_init(&newcounters[i], 0);
+	}
+	for (int i = 0; i < stats->ncounters; i++) {
+		uint32_t counter = atomic_load_acquire(&stats->counters[i]);
+		atomic_store_release(&newcounters[i], counter);
+	}
+	isc_mem_put(stats->mctx, stats->counters,
+		    sizeof(isc__atomic_statcounter_t) * stats->ncounters);
+	stats->counters = newcounters;
+	stats->ncounters = ncounters;
+}
diff --git a/lib/isc/tests/stats_test.c b/lib/isc/tests/stats_test.c
index a212613143..7b7476d3ad 100644
--- a/lib/isc/tests/stats_test.c
+++ b/lib/isc/tests/stats_test.c
@@ -96,6 +96,23 @@ isc_stats_basic_test(void **state) {
 		assert_int_equal(isc_stats_get_counter(stats, i), i + 1);
 	}
 
+	/* Test resize. */
+	isc_stats_resize(&stats, 3);
+	assert_int_equal(isc_stats_ncounters(stats), 4);
+	isc_stats_resize(&stats, 4);
+	assert_int_equal(isc_stats_ncounters(stats), 4);
+	isc_stats_resize(&stats, 5);
+	assert_int_equal(isc_stats_ncounters(stats), 5);
+
+	/* Existing counters are retained */
+	for (int i = 0; i < isc_stats_ncounters(stats); i++) {
+		uint32_t expect = i + 1;
+		if (i == 4) {
+			expect = 0;
+		}
+		assert_int_equal(isc_stats_get_counter(stats, i), expect);
+	}
+
 	isc_stats_detach(&stats);
 }