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* [PATCH iproute2 v3] add print_hexstring helper
@ 2026-07-26 15:50 Stephen Hemminger
  0 siblings, 0 replies; only message in thread
From: Stephen Hemminger @ 2026-07-26 15:50 UTC (permalink / raw)
  To: netdev; +Cc: Stephen Hemminger

hexstring_n2a() writes into a caller-supplied buffer and silently
truncates when it is too small: the loop stops once fewer than three
bytes remain and returns the partial string. Callers using a fixed
SPRINT_BUF therefore drop trailing bytes for keys wider than 31 bytes.

Add a new function print_hexstring() that formats and prints a binary
attribute in one call.

Convert the callers that dump a binary attribute straight to output
over to print_hexstring().

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 include/json_print.h |  3 +++
 ip/ipaddress.c       | 19 ++++++-------------
 ip/ipmacsec.c        |  7 ++-----
 lib/bpf_legacy.c     |  6 ++----
 lib/json_print.c     | 13 +++++++++++++
 tc/f_bpf.c           |  8 +++-----
 tc/m_action.c        |  9 +++------
 tc/m_bpf.c           |  9 +++------
 8 files changed, 35 insertions(+), 39 deletions(-)

diff --git a/include/json_print.h b/include/json_print.h
index c0d6315f..6a458189 100644
--- a/include/json_print.h
+++ b/include/json_print.h
@@ -84,6 +84,9 @@ _PRINT_FUNC(float, double)
 _PRINT_FUNC(tv, const struct timeval *)
 #undef _PRINT_FUNC
 
+void print_hexstring(const char *key, const char *fmt,
+		     const __u8 *data, unsigned int len);
+
 #define _PRINT_NAME_VALUE_FUNC(type_name, type, format_char)		  \
 	void print_##type_name##_name_value(const char *name, type value) \
 
diff --git a/ip/ipaddress.c b/ip/ipaddress.c
index 6017bc83..7e4cb77c 100644
--- a/ip/ipaddress.c
+++ b/ip/ipaddress.c
@@ -1263,22 +1263,15 @@ int print_linkinfo(struct nlmsghdr *n, void *arg)
 				     rta_getattr_str(tb[IFLA_PHYS_PORT_NAME]));
 
 		if (tb[IFLA_PHYS_PORT_ID]) {
-			print_string(PRINT_ANY,
-				     "phys_port_id",
-				     "portid %s ",
-				     hexstring_n2a(
-					     RTA_DATA(tb[IFLA_PHYS_PORT_ID]),
-					     RTA_PAYLOAD(tb[IFLA_PHYS_PORT_ID]),
-					     b1, sizeof(b1)));
+			print_hexstring("phys_port_id", "portid %s ",
+					RTA_DATA(tb[IFLA_PHYS_PORT_ID]),
+					RTA_PAYLOAD(tb[IFLA_PHYS_PORT_ID]));
 		}
 
 		if (tb[IFLA_PHYS_SWITCH_ID]) {
-			print_string(PRINT_ANY,
-				     "phys_switch_id",
-				     "switchid %s ",
-				     hexstring_n2a(RTA_DATA(tb[IFLA_PHYS_SWITCH_ID]),
-						   RTA_PAYLOAD(tb[IFLA_PHYS_SWITCH_ID]),
-						   b1, sizeof(b1)));
+			print_hexstring("phys_switch_id", "switchid %s ",
+					RTA_DATA(tb[IFLA_PHYS_SWITCH_ID]),
+					RTA_PAYLOAD(tb[IFLA_PHYS_SWITCH_ID]));
 		}
 
 		if (tb[IFLA_PARENT_DEV_BUS_NAME]) {
diff --git a/ip/ipmacsec.c b/ip/ipmacsec.c
index fc4c8631..1864ffd3 100644
--- a/ip/ipmacsec.c
+++ b/ip/ipmacsec.c
@@ -661,11 +661,8 @@ static void print_flag(struct rtattr *attrs[], const char *desc,
 
 static void print_key(struct rtattr *key)
 {
-	SPRINT_BUF(keyid);
-
-	print_string(PRINT_ANY, "key", " key %s\n",
-		     hexstring_n2a(RTA_DATA(key), RTA_PAYLOAD(key),
-				   keyid, sizeof(keyid)));
+	print_hexstring("key", " key %s\n",
+			RTA_DATA(key), RTA_PAYLOAD(key));
 }
 
 #define CIPHER_NAME_GCM_AES_128 "GCM-AES-128"
diff --git a/lib/bpf_legacy.c b/lib/bpf_legacy.c
index 50ca82c1..9d5fcf5f 100644
--- a/lib/bpf_legacy.c
+++ b/lib/bpf_legacy.c
@@ -176,7 +176,6 @@ int bpf_dump_prog_info(FILE *f, uint32_t id)
 	struct bpf_prog_info info = {};
 	uint32_t len = sizeof(info);
 	int fd, ret, dump_ok = 0;
-	SPRINT_BUF(tmp);
 
 	open_json_object("prog");
 	print_uint(PRINT_ANY, "id", "id %u ", id);
@@ -190,9 +189,8 @@ int bpf_dump_prog_info(FILE *f, uint32_t id)
 		int jited = !!info.jited_prog_len;
 
 		print_string(PRINT_ANY, "name", "name %s ", info.name);
-		print_string(PRINT_ANY, "tag", "tag %s ",
-			     hexstring_n2a(info.tag, sizeof(info.tag),
-					   tmp, sizeof(tmp)));
+		print_hexstring("tag", "tag %s ",
+				info.tag, sizeof(info.tag));
 		print_uint(PRINT_JSON, "jited", NULL, jited);
 		if (jited && !is_json_context())
 			fprintf(f, "jited ");
diff --git a/lib/json_print.c b/lib/json_print.c
index 810d496e..f604f265 100644
--- a/lib/json_print.c
+++ b/lib/json_print.c
@@ -179,6 +179,19 @@ int print_color_string(enum output_type type,
 	return ret;
 }
 
+/* Print binary data as a hex string. The buffer is sized to the input,
+ * so keys of any length are printed in full rather than truncated.
+ */
+void print_hexstring(const char *key, const char *fmt,
+		     const __u8 *data, unsigned int len)
+{
+	int blen = 2 * len + 1;
+	char buf[blen];
+
+	print_string(PRINT_ANY, key, fmt,
+		     hexstring_n2a(data, len, buf, blen));
+}
+
 /*
  * value's type is bool. When using this function in FP context you can't pass
  * a value to it, you will need to use "is_json_context()" to have different
diff --git a/tc/f_bpf.c b/tc/f_bpf.c
index 6dd75445..50fe01ca 100644
--- a/tc/f_bpf.c
+++ b/tc/f_bpf.c
@@ -241,11 +241,9 @@ static int bpf_print_opt(const struct filter_util *qu, FILE *f,
 	if (tb[TCA_BPF_ID])
 		dump_ok = bpf_dump_prog_info(f, rta_getattr_u32(tb[TCA_BPF_ID]));
 	if (!dump_ok && tb[TCA_BPF_TAG]) {
-		SPRINT_BUF(b);
-
-		print_string(PRINT_ANY, "tag", "tag %s ",
-			     hexstring_n2a(RTA_DATA(tb[TCA_BPF_TAG]),
-			     RTA_PAYLOAD(tb[TCA_BPF_TAG]), b, sizeof(b)));
+		print_hexstring("tag", "tag %s ",
+				RTA_DATA(tb[TCA_BPF_TAG]),
+				RTA_PAYLOAD(tb[TCA_BPF_TAG]));
 	}
 
 	if (tb[TCA_BPF_POLICE]) {
diff --git a/tc/m_action.c b/tc/m_action.c
index 6f79fdae..bbc8e6a6 100644
--- a/tc/m_action.c
+++ b/tc/m_action.c
@@ -401,12 +401,9 @@ static int tc_print_one_action(FILE *f, struct rtattr *arg, bool bind)
 		print_nl();
 	}
 	if (tb[TCA_ACT_COOKIE]) {
-		int strsz = RTA_PAYLOAD(tb[TCA_ACT_COOKIE]);
-		char b1[strsz * 2 + 1];
-
-		print_string(PRINT_ANY, "cookie", "\tcookie %s",
-			     hexstring_n2a(RTA_DATA(tb[TCA_ACT_COOKIE]),
-					   strsz, b1, sizeof(b1)));
+		print_hexstring("cookie", "\tcookie %s",
+				RTA_DATA(tb[TCA_ACT_COOKIE]),
+				RTA_PAYLOAD(tb[TCA_ACT_COOKIE]));
 		print_nl();
 	}
 	if (tb[TCA_ACT_FLAGS] || tb[TCA_ACT_IN_HW_COUNT]) {
diff --git a/tc/m_bpf.c b/tc/m_bpf.c
index a5de7da1..83b21b57 100644
--- a/tc/m_bpf.c
+++ b/tc/m_bpf.c
@@ -183,12 +183,9 @@ static int bpf_print_opt(const struct action_util *au, FILE *f, struct rtattr *a
 		d_ok = bpf_dump_prog_info(f,
 					  rta_getattr_u32(tb[TCA_ACT_BPF_ID]));
 	if (!d_ok && tb[TCA_ACT_BPF_TAG]) {
-		SPRINT_BUF(b);
-
-		print_string(PRINT_ANY, "tag", "tag %s ",
-			     hexstring_n2a(RTA_DATA(tb[TCA_ACT_BPF_TAG]),
-			     RTA_PAYLOAD(tb[TCA_ACT_BPF_TAG]),
-			     b, sizeof(b)));
+		print_hexstring("tag", "tag %s ",
+				RTA_DATA(tb[TCA_ACT_BPF_TAG]),
+				RTA_PAYLOAD(tb[TCA_ACT_BPF_TAG]));
 	}
 
 	print_action_control("default-action ", parm->action, _SL_);
-- 
2.53.0


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