sctp: implement event notification SCTP_SENDER_DRY_EVENT

This patch implement event notification SCTP_SENDER_DRY_EVENT.
SCTP Socket API Extensions:

6.1.9. SCTP_SENDER_DRY_EVENT

When the SCTP stack has no more user data to send or retransmit, this
notification is given to the user. Also, at the time when a user app
subscribes to this event, if there is no data to be sent or
retransmit, the stack will immediately send up this notification.

Signed-off-by: Wei Yongjun <[e-mail]>
Signed-off-by: Vlad Yasevich <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/net/sctp/sm.h

···
 sctp_state_fn_t sctp_sf_do_prm_asconf;
 
 /* Prototypes for other event state functions.  */
+sctp_state_fn_t sctp_sf_do_no_pending_tsn;
 sctp_state_fn_t sctp_sf_do_9_2_start_shutdown;
 sctp_state_fn_t sctp_sf_do_9_2_shutdown_ack;
 sctp_state_fn_t sctp_sf_ignore_other;

include/net/sctp/ulpevent.h

···
 	const struct sctp_association *asoc, __u16 key_id,
 	__u32 indication, gfp_t gfp);
 
+struct sctp_ulpevent *sctp_ulpevent_make_sender_dry_event(
+	const struct sctp_association *asoc, gfp_t gfp);
+
 void sctp_ulpevent_read_sndrcvinfo(const struct sctp_ulpevent *event,
 	struct msghdr *);
 __u16 sctp_ulpevent_get_notification_type(const struct sctp_ulpevent *event);

include/net/sctp/user.h

···
 
 enum { SCTP_AUTH_NEWKEY = 0, };
 
+/*
+ * 6.1.9. SCTP_SENDER_DRY_EVENT
+ *
+ * When the SCTP stack has no more user data to send or retransmit, this
+ * notification is given to the user. Also, at the time when a user app
+ * subscribes to this event, if there is no data to be sent or
+ * retransmit, the stack will immediately send up this notification.
+ */
+struct sctp_sender_dry_event {
+	__u16 sender_dry_type;
+	__u16 sender_dry_flags;
+	__u32 sender_dry_length;
+	sctp_assoc_t sender_dry_assoc_id;
+};
 
 /*
  * Described in Section 7.3
···
 	__u8 sctp_partial_delivery_event;
 	__u8 sctp_adaptation_layer_event;
 	__u8 sctp_authentication_event;
+	__u8 sctp_sender_dry_event;
 };
 
 /*
···
 	struct sctp_adaptation_event sn_adaptation_event;
 	struct sctp_pdapi_event sn_pdapi_event;
 	struct sctp_authkey_event sn_authkey_event;
+	struct sctp_sender_dry_event sn_sender_dry_event;
 };
 
 /* Section 5.3.1
···
 	SCTP_ADAPTATION_INDICATION,
 	SCTP_AUTHENTICATION_EVENT,
 #define SCTP_AUTHENTICATION_INDICATION	SCTP_AUTHENTICATION_EVENT
+	SCTP_SENDER_DRY_EVENT,
 };
 
 /* Notification error codes used to fill up the error fields in some

net/sctp/sm_statefuns.c

···
  ***************************************************************************/
 
 /*
+ * When the SCTP stack has no more user data to send or retransmit, this
+ * notification is given to the user. Also, at the time when a user app
+ * subscribes to this event, if there is no data to be sent or
+ * retransmit, the stack will immediately send up this notification.
+ */
+sctp_disposition_t sctp_sf_do_no_pending_tsn(
+	const struct sctp_endpoint *ep,
+	const struct sctp_association *asoc,
+	const sctp_subtype_t type,
+	void *arg,
+	sctp_cmd_seq_t *commands)
+{
+	struct sctp_ulpevent *event;
+
+	event = sctp_ulpevent_make_sender_dry_event(asoc, GFP_ATOMIC);
+	if (!event)
+		return SCTP_DISPOSITION_NOMEM;
+
+	sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP, SCTP_ULPEVENT(event));
+
+	return SCTP_DISPOSITION_CONSUME;
+}
+
+/*
  * Start the shutdown negotiation.
  *
  * From Section 9.2:

net/sctp/sm_statetable.c

···
 	/* SCTP_STATE_COOKIE_ECHOED */ \
 	TYPE_SCTP_FUNC(sctp_sf_ignore_other), \
 	/* SCTP_STATE_ESTABLISHED */ \
-	TYPE_SCTP_FUNC(sctp_sf_ignore_other), \
+	TYPE_SCTP_FUNC(sctp_sf_do_no_pending_tsn), \
 	/* SCTP_STATE_SHUTDOWN_PENDING */ \
 	TYPE_SCTP_FUNC(sctp_sf_do_9_2_start_shutdown), \
 	/* SCTP_STATE_SHUTDOWN_SENT */ \

net/sctp/ulpevent.c

···
 	return NULL;
 }
 
+/*
+ * Socket Extensions for SCTP
+ * 6.3.10. SCTP_SENDER_DRY_EVENT
+ */
+struct sctp_ulpevent *sctp_ulpevent_make_sender_dry_event(
+	const struct sctp_association *asoc, gfp_t gfp)
+{
+	struct sctp_ulpevent *event;
+	struct sctp_sender_dry_event *sdry;
+	struct sk_buff *skb;
+
+	event = sctp_ulpevent_new(sizeof(struct sctp_sender_dry_event),
+				  MSG_NOTIFICATION, gfp);
+	if (!event)
+		return NULL;
+
+	skb = sctp_event2skb(event);
+	sdry = (struct sctp_sender_dry_event *)
+		skb_put(skb, sizeof(struct sctp_sender_dry_event));
+
+	sdry->sender_dry_type = SCTP_SENDER_DRY_EVENT;
+	sdry->sender_dry_flags = 0;
+	sdry->sender_dry_length = sizeof(struct sctp_sender_dry_event);
+	sctp_ulpevent_set_owner(event, asoc);
+	sdry->sender_dry_assoc_id = sctp_assoc2id(asoc);
+
+	return event;
+}
 
 /* Return the notification type, assuming this is a notification
  * event.