msg: Introduce a method to copy a message.

The transparent clock will want to have two copies of certain messages,
one for forwarding and one for internal use (in the BMCA and for
syntonization).  This patch add a function that duplicates a given
message, including all of the attached TLVs.

Signed-off-by: Richard Cochran <richardcochran@gmail.com>

msg.c

@@ -295,6 +295,40 @@ void msg_cleanup(void)
 	}
 }
 
+struct ptp_message *msg_duplicate(struct ptp_message *msg, int cnt)
+{
+	struct ptp_message *dup;
+	int err;
+
+	dup = msg_allocate();
+	if (!dup) {
+		return NULL;
+	}
+	memcpy(dup, msg, sizeof(*dup));
+	dup->refcnt = 1;
+	TAILQ_INIT(&dup->tlv_list);
+	dup->tlv_count = 0;
+
+	err = msg_post_recv(dup, cnt);
+	if (err) {
+		switch (err) {
+		case -EBADMSG:
+			pr_err("msg_duplicate: bad message");
+			break;
+		case -ETIME:
+			pr_err("msg_duplicate: received %s without timestamp",
+				msg_type_string(msg_type(msg)));
+			break;
+		case -EPROTO:
+			pr_debug("msg_duplicate: ignoring message");
+			break;
+		}
+		msg_put(dup);
+		return NULL;
+	}
+	return dup;
+}
+
 void msg_get(struct ptp_message *m)
 {
 	m->refcnt++;

msg.h

@@ -316,6 +316,26 @@ struct ptp_message *msg_allocate(void);
  */
 void msg_cleanup(void);
 
+/**
+ * Duplicate a message instance.
+ *
+ * This function accepts a message in network byte order and returns a
+ * duplicate in host byte.
+ *
+ * Messages are reference counted, and newly allocated messages have a
+ * reference count of one. Allocated messages are freed using the
+ * function @ref msg_put().
+ *
+ * @param msg  A message obtained using @ref msg_allocate().
+ *             The passed message must be in network byte order, not
+ *             having been passed to @ref msg_post_recv().
+ *
+ * @return     Pointer to a message on success, NULL otherwise.
+ *             The returned message will be in host byte order, having
+ *             been passed to @ref msg_post_recv().
+ */
+struct ptp_message *msg_duplicate(struct ptp_message *msg, int cnt);
+
 /**
  * Obtain a reference to a message, increasing its reference count by one.
  * @param m A message obtained using @ref msg_allocate().