[PATCH iproute2 3/3] tc: build ct label strings with hexstring_alloc

[Stephen Hemminger <stephen@networkplumber.org>]

flower_print_ct_label() and ct_print_labels() formatted the key and
optional mask into a fixed on-stack buffer with manual pointer
arithmetic, relying on hexstring_n2a() not to overrun it. Build the
"key/mask" string with hexstring_alloc() and asprintf() instead, which
sizes to the data and drops the open-coded offset handling.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 tc/f_flower.c | 25 ++++++++++++++-----------
 tc/m_ct.c     | 24 ++++++++++++++----------
 2 files changed, 28 insertions(+), 21 deletions(-)

diff --git a/tc/f_flower.c b/tc/f_flower.c
index 6fc2c6a1..d6844282 100644
--- a/tc/f_flower.c
+++ b/tc/f_flower.c
@@ -2619,18 +2619,15 @@ static void flower_print_ct_label(struct rtattr *attr,
 {
 	const unsigned char *str;
 	bool print_mask = false;
+	char *key, *out;
 	int data_len, i;
-	char out[128];
-	char *p;
 
 	if (!attr)
 		return;
 
 	data_len = RTA_PAYLOAD(attr);
-	hexstring_n2a(RTA_DATA(attr), data_len, out, sizeof(out));
-	p = out + data_len*2;
+	key = hexstring_alloc(RTA_DATA(attr), data_len);
 
-	data_len = RTA_PAYLOAD(attr);
 	str = RTA_DATA(mask_attr);
 	if (data_len != 16)
 		print_mask = true;
@@ -2638,16 +2635,22 @@ static void flower_print_ct_label(struct rtattr *attr,
 		if (str[i] != 0xff)
 			print_mask = true;
 	}
+
 	if (print_mask) {
-		*p++ = '/';
-		hexstring_n2a(RTA_DATA(mask_attr), data_len, p,
-			      sizeof(out)-(p-out));
-		p += data_len*2;
+		char *mask = hexstring_alloc(RTA_DATA(mask_attr), data_len);
+
+		if (asprintf(&out, "%s/%s", key, mask) < 0)
+			out = NULL;
+		free(mask);
+		free(key);
+	} else {
+		out = key;
 	}
-	*p = '\0';
 
 	print_nl();
-	print_string(PRINT_ANY, "ct_label", "  ct_label %s", out);
+	print_string(PRINT_ANY, "ct_label", "  ct_label %s", out ? : "");
+
+	free(out);
 }
 
 static void flower_print_ct_zone(struct rtattr *attr,
diff --git a/tc/m_ct.c b/tc/m_ct.c
index e549cb9c..e5eebbda 100644
--- a/tc/m_ct.c
+++ b/tc/m_ct.c
@@ -443,17 +443,15 @@ static void ct_print_labels(struct rtattr *attr,
 {
 	const unsigned char *str;
 	bool print_mask = false;
-	char out[256], *p;
+	char *key, *out;
 	int data_len, i;
 
 	if (!attr)
 		return;
 
 	data_len = RTA_PAYLOAD(attr);
-	hexstring_n2a(RTA_DATA(attr), data_len, out, sizeof(out));
-	p = out + data_len*2;
+	key = hexstring_alloc(RTA_DATA(attr), data_len);
 
-	data_len = RTA_PAYLOAD(attr);
 	str = RTA_DATA(mask_attr);
 	if (data_len != 16)
 		print_mask = true;
@@ -461,15 +459,21 @@ static void ct_print_labels(struct rtattr *attr,
 		if (str[i] != 0xff)
 			print_mask = true;
 	}
+
 	if (print_mask) {
-		*p++ = '/';
-		hexstring_n2a(RTA_DATA(mask_attr), data_len, p,
-			      sizeof(out)-(p-out));
-		p += data_len*2;
+		char *mask = hexstring_alloc(RTA_DATA(mask_attr), data_len);
+
+		if (asprintf(&out, "%s/%s", key, mask) < 0)
+			out = NULL;
+		free(mask);
+		free(key);
+	} else {
+		out = key;
 	}
-	*p = '\0';
 
-	print_string(PRINT_ANY, "label", " label %s", out);
+	print_string(PRINT_ANY, "label", " label %s", out ? : "");
+
+	free(out);
 }
 
 static void ct_print_helper(struct rtattr *family, struct rtattr *proto, struct rtattr *name)
-- 
2.53.0