sctp: add support for generating add stream change event notification

This patch is to add Stream Change Event described in rfc6525
section 6.1.3.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sctp/ulpevent.c b/net/sctp/ulpevent.c
index 420d7f3..ec2b3e0 100644
--- a/net/sctp/ulpevent.c
+++ b/net/sctp/ulpevent.c
@@ -911,6 +911,34 @@
 	return event;
 }
 
+struct sctp_ulpevent *sctp_ulpevent_make_stream_change_event(
+	const struct sctp_association *asoc, __u16 flags,
+	__u32 strchange_instrms, __u32 strchange_outstrms, gfp_t gfp)
+{
+	struct sctp_stream_change_event *schange;
+	struct sctp_ulpevent *event;
+	struct sk_buff *skb;
+
+	event = sctp_ulpevent_new(sizeof(struct sctp_stream_change_event),
+				  MSG_NOTIFICATION, gfp);
+	if (!event)
+		return NULL;
+
+	skb = sctp_event2skb(event);
+	schange = (struct sctp_stream_change_event *)
+		skb_put(skb, sizeof(struct sctp_stream_change_event));
+
+	schange->strchange_type = SCTP_STREAM_CHANGE_EVENT;
+	schange->strchange_flags = flags;
+	schange->strchange_length = sizeof(struct sctp_stream_change_event);
+	sctp_ulpevent_set_owner(event, asoc);
+	schange->strchange_assoc_id = sctp_assoc2id(asoc);
+	schange->strchange_instrms = strchange_instrms;
+	schange->strchange_outstrms = strchange_outstrms;
+
+	return event;
+}
+
 /* Return the notification type, assuming this is a notification
  * event.
  */