platform: avoid heap allocating string buffer for printing link flagsth/platform-link-broadcast

3 files changed, 46 insertions, 15 deletions

diff --git a/src/platform/nm-platform.c b/src/platform/nm-platform.c
index a4a0eb8d98..0c3888a4d6 100644
--- a/src/platform/nm-platform.c
+++ b/src/platform/nm-platform.c
@@ -5390,7 +5390,10 @@ nm_platform_link_to_string (const NMPlatformLink *link, char *buf, gsize len)
 {
 	char master[20];
 	char parent[20];
-	GString *str_flags;
+	char str_flags[1 + NM_PLATFORM_LINK_FLAGS2STR_MAX_LEN + 1];
+	char str_highlighted_flags[50];
+	char *s;
+	gsize l;
 	char str_addrmode[30];
 	char str_address[NM_UTILS_HWADDR_LEN_MAX * 3];
 	char str_broadcast[NM_UTILS_HWADDR_LEN_MAX * 3];
@@ -5400,22 +5403,23 @@ nm_platform_link_to_string (const NMPlatformLink *link, char *buf, gsize len)
 	if (!nm_utils_to_string_buffer_init_null (link, &buf, &len))
 		return buf;
 
-	str_flags = g_string_new (NULL);
+	s = str_highlighted_flags;
+	l = sizeof (str_highlighted_flags);
 	if (NM_FLAGS_HAS (link->n_ifi_flags, IFF_NOARP))
-		g_string_append (str_flags, "NOARP,");
+		nm_utils_strbuf_append_str (&s, &l, "NOARP,");
 	if (NM_FLAGS_HAS (link->n_ifi_flags, IFF_UP))
-		g_string_append (str_flags, "UP");
+		nm_utils_strbuf_append_str (&s, &l, "UP");
 	else
-		g_string_append (str_flags, "DOWN");
+		nm_utils_strbuf_append_str (&s, &l, "DOWN");
 	if (link->connected)
-		g_string_append (str_flags, ",LOWER_UP");
+		nm_utils_strbuf_append_str (&s, &l, ",LOWER_UP");
+	nm_assert (s > str_highlighted_flags && l > 0);
 
 	if (link->n_ifi_flags) {
-		char str_flags_buf[64];
-
-		nm_platform_link_flags2str (link->n_ifi_flags, str_flags_buf, sizeof (str_flags_buf));
-		g_string_append_printf (str_flags, ";%s", str_flags_buf);
-	}
+		str_flags[0] = ';';
+		nm_platform_link_flags2str (link->n_ifi_flags, &str_flags[1], sizeof (str_flags) - 1);
+	} else
+		str_flags[0] = '\0';
 
 	if (link->master)
 		g_snprintf (master, sizeof (master), " master %d", link->master);
@@ -5438,7 +5442,7 @@ nm_platform_link_to_string (const NMPlatformLink *link, char *buf, gsize len)
 	            "%d: " /* ifindex */
 	            "%s" /* name */
 	            "%s" /* parent */
-	            " <%s>" /* flags */
+	            " <%s%s>" /* flags */
 	            " mtu %d"
 	            "%s" /* master */
 	            " arp %u" /* arptype */
@@ -5456,7 +5460,8 @@ nm_platform_link_to_string (const NMPlatformLink *link, char *buf, gsize len)
 	            link->ifindex,
 	            link->name,
 	            parent,
-	            str_flags->str,
+	            str_highlighted_flags,
+	            str_flags,
 	            link->mtu, master,
 	            link->arptype,
 	            str_link_type ?: "???",
@@ -5475,7 +5480,6 @@ nm_platform_link_to_string (const NMPlatformLink *link, char *buf, gsize len)
 	            link->driver ?: "",
 	            link->rx_packets, link->rx_bytes,
 	            link->tx_packets, link->tx_bytes);
-	g_string_free (str_flags, TRUE);
 	return buf;
 }
 
diff --git a/src/platform/nm-platform.h b/src/platform/nm-platform.h
index 972b009361..70e956206c 100644
--- a/src/platform/nm-platform.h
+++ b/src/platform/nm-platform.h
@@ -1791,6 +1791,8 @@ void nm_platform_lnk_wireguard_hash_update (const NMPlatformLnkWireGuard *obj, N
 void nm_platform_qdisc_hash_update (const NMPlatformQdisc *obj, NMHashState *h);
 void nm_platform_tfilter_hash_update (const NMPlatformTfilter *obj, NMHashState *h);
 
+#define NM_PLATFORM_LINK_FLAGS2STR_MAX_LEN ((gsize) 162)
+
 const char *nm_platform_link_flags2str (unsigned flags, char *buf, gsize len);
 const char *nm_platform_link_inet6_addrgenmode2str (guint8 mode, char *buf, gsize len);
 const char *nm_platform_addr_flags2str (unsigned flags, char *buf, gsize len);
diff --git a/src/platform/tests/test-platform-general.c b/src/platform/tests/test-platform-general.c
index eebc15d80d..7f98b65f99 100644
--- a/src/platform/tests/test-platform-general.c
+++ b/src/platform/tests/test-platform-general.c
@@ -52,6 +52,31 @@ test_link_get_all (void)
 
 /*****************************************************************************/
 
+static void
+test_nm_platform_link_flags2str (void)
+{
+	int i;
+
+	for (i = 0; i < 100; i++) {
+		char buf[NM_PLATFORM_LINK_FLAGS2STR_MAX_LEN + 100];
+		const char *s;
+		const guint flags = ((i == 0) ? ~0u : nmtst_get_rand_uint ());
+		gsize l;
+
+		s = nm_platform_link_flags2str (flags, buf, sizeof (buf));
+		g_assert (s);
+
+		l = strlen (s);
+		if (l > NM_PLATFORM_LINK_FLAGS2STR_MAX_LEN)
+			g_error ("nm_platform_link_flags2str(%x) produced a longer output than %zu chars: \"%s\"", flags, NM_PLATFORM_LINK_FLAGS2STR_MAX_LEN, s);
+		if (   flags == ~0u
+		    && l != NM_PLATFORM_LINK_FLAGS2STR_MAX_LEN)
+			g_error ("nm_platform_link_flags2str(%x) is expected to produce %zu chars, but produced %zu: \"%s\"", flags, NM_PLATFORM_LINK_FLAGS2STR_MAX_LEN, l, s);
+	}
+}
+
+/*****************************************************************************/
+
 NMTST_DEFINE ();
 
 int
@@ -61,7 +86,7 @@ main (int argc, char **argv)
 
 	g_test_add_func ("/general/init_linux_platform", test_init_linux_platform);
 	g_test_add_func ("/general/link_get_all", test_link_get_all);
+	g_test_add_func ("/general/nm_platform_link_flags2str", test_nm_platform_link_flags2str);
 
 	return g_test_run ();
 }
-