genl: Add genlmsg_user_hdr(), genlmsg_user_data(), and genlmsg_user_datalen()

These functions deprecate the function genlmsg_data() which did not
allow to specify the length of the user header. Use of the new API
will make code much clearer. The old function is still kept around
for backwards compatibility but marked deprecated in the API reference.

3 files changed, 77 insertions, 18 deletions

diff --git a/include/netlink/genl/genl.h b/include/netlink/genl/genl.h
index a2da943..e455581 100644
--- a/include/netlink/genl/genl.h
+++ b/include/netlink/genl/genl.h
@@ -35,6 +35,10 @@ extern int		genlmsg_parse(struct nlmsghdr *, int, struct nlattr **,
 extern struct genlmsghdr *
 			genlmsg_hdr(struct nlmsghdr *);
 extern void *		genlmsg_data(const struct genlmsghdr *);
+extern void *		genlmsg_user_hdr(const struct genlmsghdr *);
+extern void *		genlmsg_user_data(const struct genlmsghdr *, const int);
+extern int		genlmsg_user_datalen(const struct genlmsghdr *,
+					     const int);
 extern int		genlmsg_len(const struct genlmsghdr *);
 extern struct nlattr *	genlmsg_attrdata(const struct genlmsghdr *, int);
 extern int		genlmsg_attrlen(const struct genlmsghdr *, int);
diff --git a/lib/genl/genl.c b/lib/genl/genl.c
index 8f2e496..569ef9e 100644
--- a/lib/genl/genl.c
+++ b/lib/genl/genl.c
@@ -213,36 +213,66 @@ struct genlmsghdr *genlmsg_hdr(struct nlmsghdr *nlh)
 }
 
 /**
- * Return pointer to message payload
+ * Return length of message payload including user header
  * @arg gnlh		Generic Netlink message header
  *
- * Calculates the pointer to the message payload based on the pointer
- * to the generic netlink message header.
+ * @see genlmsg_data()
  *
- * @note Depending on whether your own message format uses a header, the
- *       returned pointer may in fact point to the user header.
+ * @return Length of user payload including an eventual user header in
+ *         number of bytes.
+ */
+int genlmsg_len(const struct genlmsghdr *gnlh)
+{
+	struct nlmsghdr *nlh;
+
+	nlh = (struct nlmsghdr *)((unsigned char *) gnlh - NLMSG_HDRLEN);
+	return (nlh->nlmsg_len - GENL_HDRLEN - NLMSG_HDRLEN);
+}
+
+
+/**
+ * Return pointer to user header
+ * @arg gnlh		Generic Netlink message header
+ *
+ * Calculates the pointer to the user header based on the pointer to
+ * the Generic Netlink message header.
  *
- * @return Pointer to generic netlink message
+ * @return Pointer to the user header
  */
-void *genlmsg_data(const struct genlmsghdr *gnlh)
+void *genlmsg_user_hdr(const struct genlmsghdr *gnlh)
 {
-	return ((unsigned char *) gnlh + GENL_HDRLEN);
+	return genlmsg_data(gnlh);
 }
 
+/**
+ * Return pointer to user data
+ * @arg gnlh		Generic netlink message header
+ * @arg hdrlen		Length of user header
+ *
+ * Calculates the pointer to the user data based on the pointer to
+ * the Generic Netlink message header.
+ *
+ * @see genlmsg_user_datalen()
+ *
+ * @return Pointer to the user data
+ */
+void *genlmsg_user_data(const struct genlmsghdr *gnlh, const int hdrlen)
+{
+	return genlmsg_user_hdr(gnlh) + NLMSG_ALIGN(hdrlen);
+}
 
 /**
- * Return length of message payload
+ * Return length of user data
  * @arg gnlh		Generic Netlink message header
+ * @arg hdrlen		Length of user header
  *
- * @return Length of user payload including an eventual user header in
- *         number of bytes.
+ * @see genlmsg_user_data()
+ *
+ * @return Length of user data in bytes
  */
-int genlmsg_len(const struct genlmsghdr *gnlh)
+int genlmsg_user_datalen(const struct genlmsghdr *gnlh, const int hdrlen)
 {
-	struct nlmsghdr *nlh;
-	
-	nlh = (struct nlmsghdr *)((unsigned char *) gnlh - NLMSG_HDRLEN);
-	return (nlh->nlmsg_len - GENL_HDRLEN - NLMSG_HDRLEN);
+	return genlmsg_len(gnlh) - NLMSG_ALIGN(hdrlen);
 }
 
 /**
@@ -250,11 +280,13 @@ int genlmsg_len(const struct genlmsghdr *gnlh)
  * @arg gnlh		Generic Netlink message header
  * @arg hdrlen		Length of user header
  *
+ * @see genlmsg_attrlen()
+ *
  * @return Pointer to the start of the message's attributes section.
  */
 struct nlattr *genlmsg_attrdata(const struct genlmsghdr *gnlh, int hdrlen)
 {
-	return genlmsg_data(gnlh) + NLMSG_ALIGN(hdrlen);
+	return genlmsg_user_data(gnlh, hdrlen);
 }
 
 /**
@@ -262,6 +294,8 @@ struct nlattr *genlmsg_attrdata(const struct genlmsghdr *gnlh, int hdrlen)
  * @arg gnlh		Generic Netlink message header
  * @arg hdrlen		Length of user header
  *
+ * @see genlmsg_attrdata()
+ *
  * @return Length of the message section containing attributes in number
  *         of bytes.
  */
@@ -333,4 +367,25 @@ void *genlmsg_put(struct nl_msg *msg, uint32_t port, uint32_t seq, int family,
 
 /** @} */
 
+/**
+ * @name Deprecated
+ * @{
+ */
+
+/**
+ * Return pointer to message payload
+ * @arg gnlh		Generic Netlink message header
+ *
+ * @deprecated This function has been deprecated due to inability to specify
+ *             the length of the user header. Use genlmsg_user_hdr()
+ *             respectively genlmsg_user_data().
+ *
+ * @return Pointer to payload section
+ */
+void *genlmsg_data(const struct genlmsghdr *gnlh)
+{
+	return ((unsigned char *) gnlh + GENL_HDRLEN);
+}
+
+/** @} */
 /** @} */
diff --git a/lib/genl/mngt.c b/lib/genl/mngt.c
index fd1aa03..f53aa8a 100644
--- a/lib/genl/mngt.c
+++ b/lib/genl/mngt.c
@@ -60,7 +60,7 @@ found:
 			.who = who,
 			.nlh = nlh,
 			.genlhdr = ghdr,
-			.userhdr = genlmsg_data(ghdr),
+			.userhdr = genlmsg_user_hdr(ghdr),
 			.attrs = tb,
 		};