[NETLINK]: Add notification message sending interface
Adds nlmsg_notify() implementing proper notification logic. The
message is multicasted to all listeners in the group. The
applications the requests orignates from can request a unicast
back report in which case said socket will be excluded from the
multicast to avoid duplicated notifications.
nlmsg_multicast() is extended to take allocation flags to
allow notification in atomic contexts.
Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 0f36ddc..a80e445 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1549,6 +1549,38 @@
skb_pull(skb, msglen);
}
+/**
+ * nlmsg_notify - send a notification netlink message
+ * @sk: netlink socket to use
+ * @skb: notification message
+ * @pid: destination netlink pid for reports or 0
+ * @group: destination multicast group or 0
+ * @report: 1 to report back, 0 to disable
+ * @flags: allocation flags
+ */
+int nlmsg_notify(struct sock *sk, struct sk_buff *skb, u32 pid,
+ unsigned int group, int report, gfp_t flags)
+{
+ int err = 0;
+
+ if (group) {
+ int exclude_pid = 0;
+
+ if (report) {
+ atomic_inc(&skb->users);
+ exclude_pid = pid;
+ }
+
+ /* errors reported via destination sk->sk_err */
+ nlmsg_multicast(sk, skb, exclude_pid, group, flags);
+ }
+
+ if (report)
+ err = nlmsg_unicast(sk, skb, pid);
+
+ return err;
+}
+
#ifdef CONFIG_PROC_FS
struct nl_seq_iter {
int link;
@@ -1802,4 +1834,4 @@
EXPORT_SYMBOL(netlink_set_nonroot);
EXPORT_SYMBOL(netlink_unicast);
EXPORT_SYMBOL(netlink_unregister_notifier);
-
+EXPORT_SYMBOL(nlmsg_notify);