diff --git a/util.c b/util.c
index 06c3296..1fa8336 100644
--- a/util.c
+++ b/util.c
@@ -88,6 +88,19 @@ char *pid2str(struct PortIdentity *id)
 	return buf;
 }
 
+int str2mac(const char *s, unsigned char mac[MAC_LEN])
+{
+	unsigned char buf[MAC_LEN];
+	int c;
+	c = sscanf(s, "%hhx:%hhx:%hhx:%hhx:%hhx:%hhx",
+		   &buf[0], &buf[1], &buf[2], &buf[3], &buf[4], &buf[5]);
+	if (c != MAC_LEN) {
+		return -1;
+	}
+	memcpy(mac, buf, MAC_LEN);
+	return 0;
+}
+
 int str2pid(const char *s, struct PortIdentity *result)
 {
 	struct PortIdentity pid;
diff --git a/util.h b/util.h
index 98b395b..734ea05 100644
--- a/util.h
+++ b/util.h
@@ -21,6 +21,7 @@
 #define HAVE_UTIL_H
 
 #include "ddt.h"
+#include "ether.h"
 
 /**
  * Table of human readable strings, one for each port state.
@@ -54,6 +55,15 @@ char *cid2str(struct ClockIdentity *id);
  */
 char *pid2str(struct PortIdentity *id);
 
+/**
+ * Scan a string containing a MAC address and convert it into binary form.
+ *
+ * @param s       String in human readable form.
+ * @param mac     Pointer to a buffer to hold the result.
+ * @return Zero on success, or -1 if the string is incorrectly formatted.
+ */
+int str2mac(const char *s, unsigned char mac[MAC_LEN]);
+
 /**
  * Scan a string containing a port identity and convert it into binary form.
  *