[RTNETLINK]: Add rtnetlink notification interface

Adds rtnl_notify() to send rtnetlink notification messages and
rtnl_set_sk_err() to report notification errors as socket
errors in order to indicate the need of a resync due to loss
of events.

nlmsg_report() is added to properly document the meaning of
NLM_F_ECHO.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 20 insertions, 0 deletions

diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h
index 0e4f478e2cb..ecbe0349060 100644
--- a/include/linux/rtnetlink.h
+++ b/include/linux/rtnetlink.h
@@ -585,6 +585,9 @@ struct rtnetlink_link
 extern struct rtnetlink_link * rtnetlink_links[NPROTO];
 extern int rtnetlink_send(struct sk_buff *skb, u32 pid, u32 group, int echo);
 extern int rtnl_unicast(struct sk_buff *skb, u32 pid);
+extern int rtnl_notify(struct sk_buff *skb, u32 pid, u32 group,
+                       struct nlmsghdr *nlh, gfp_t flags);
+extern void rtnl_set_sk_err(u32 group, int error);
 extern int rtnetlink_put_metrics(struct sk_buff *skb, u32 *metrics);
 
 extern void __rta_fill(struct sk_buff *skb, int attrtype, int attrlen, const void *data);
diff --git a/include/net/netlink.h b/include/net/netlink.h
index b154b81d9a7..bf593eb59e1 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -65,6 +65,9 @@
  *   nlmsg_validate()                   validate netlink message incl. attrs
  *   nlmsg_for_each_attr()              loop over all attributes
  *
+ * Misc:
+ *   nlmsg_report()                     report back to application?
+ *
  * ------------------------------------------------------------------------
  *                          Attributes Interface
  * ------------------------------------------------------------------------
@@ -194,6 +197,9 @@ extern void		netlink_run_queue(struct sock *sk, unsigned int *qlen,
                                                     struct nlmsghdr *, int *));
 extern void             netlink_queue_skip(struct nlmsghdr *nlh,
                                            struct sk_buff *skb);
+extern int              nlmsg_notify(struct sock *sk, struct sk_buff *skb,
+                                     u32 pid, unsigned int group, int report,
+                                     gfp_t flags);
 
 extern int              nla_validate(struct nlattr *head, int len, int maxtype,
                                      struct nla_policy *policy);
@@ -376,6 +382,17 @@ static inline int nlmsg_validate(struct nlmsghdr *nlh, int hdrlen, int maxtype,
 }
 
 /**
+ * nlmsg_report - need to report back to application?
+ * @nlh: netlink message header
+ *
+ * Returns 1 if a report back to the application is requested.
+ */
+static inline int nlmsg_report(struct nlmsghdr *nlh)
+{
+        return !!(nlh->nlmsg_flags & NLM_F_ECHO);
+}
+
+/**
  * nlmsg_for_each_attr - iterate over a stream of attributes
  * @pos: loop counter, set to current attribute
  * @nlh: netlink message header