sctp: Fix to handle SHUTDOWN in SHUTDOWN_RECEIVED state

Once an endpoint has reached the SHUTDOWN-RECEIVED state,
it MUST NOT send a SHUTDOWN in response to a ULP request.
The Cumulative TSN Ack of the received SHUTDOWN chunk
MUST be processed.

This patch fix to process Cumulative TSN Ack of the received
SHUTDOWN chunk in SHUTDOWN_RECEIVED state.

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_backbeat_8_3;
 sctp_state_fn_t sctp_sf_do_9_2_final;
 sctp_state_fn_t sctp_sf_do_9_2_shutdown;
+sctp_state_fn_t sctp_sf_do_9_2_shut_ctsn;
 sctp_state_fn_t sctp_sf_do_ecn_cwr;
 sctp_state_fn_t sctp_sf_do_ecne;
 sctp_state_fn_t sctp_sf_ootb;

net/sctp/sm_statefuns.c

···
 	return disposition;
 }
 
+/*
+ * sctp_sf_do_9_2_shut_ctsn
+ *
+ * Once an endpoint has reached the SHUTDOWN-RECEIVED state,
+ * it MUST NOT send a SHUTDOWN in response to a ULP request.
+ * The Cumulative TSN Ack of the received SHUTDOWN chunk
+ * MUST be processed.
+ */
+sctp_disposition_t sctp_sf_do_9_2_shut_ctsn(const struct sctp_endpoint *ep,
+					   const struct sctp_association *asoc,
+					   const sctp_subtype_t type,
+					   void *arg,
+					   sctp_cmd_seq_t *commands)
+{
+	struct sctp_chunk *chunk = arg;
+	sctp_shutdownhdr_t *sdh;
+
+	if (!sctp_vtag_verify(chunk, asoc))
+		return sctp_sf_pdiscard(ep, asoc, type, arg, commands);
+
+	/* Make sure that the SHUTDOWN chunk has a valid length. */
+	if (!sctp_chunk_length_valid(chunk,
+				      sizeof(struct sctp_shutdown_chunk_t)))
+		return sctp_sf_violation_chunklen(ep, asoc, type, arg,
+						  commands);
+
+	sdh = (sctp_shutdownhdr_t *)chunk->skb->data;
+
+	/* If Cumulative TSN Ack beyond the max tsn currently
+	 * send, terminating the association and respond to the
+	 * sender with an ABORT.
+	 */
+	if (!TSN_lt(ntohl(sdh->cum_tsn_ack), asoc->next_tsn))
+		return sctp_sf_violation_ctsn(ep, asoc, type, arg, commands);
+
+	/* verify, by checking the Cumulative TSN Ack field of the
+	 * chunk, that all its outstanding DATA chunks have been
+	 * received by the SHUTDOWN sender.
+	 */
+	sctp_add_cmd_sf(commands, SCTP_CMD_PROCESS_CTSN,
+			SCTP_BE32(sdh->cum_tsn_ack));
+
+	return SCTP_DISPOSITION_CONSUME;
+}
+
 /* RFC 2960 9.2
  * If an endpoint is in SHUTDOWN-ACK-SENT state and receives an INIT chunk
  * (e.g., if the SHUTDOWN COMPLETE was lost) with source and destination

net/sctp/sm_statetable.c

···
 	/* SCTP_STATE_SHUTDOWN_SENT */ \
 	TYPE_SCTP_FUNC(sctp_sf_do_9_2_shutdown_ack), \
 	/* SCTP_STATE_SHUTDOWN_RECEIVED */ \
-	TYPE_SCTP_FUNC(sctp_sf_discard_chunk), \
+	TYPE_SCTP_FUNC(sctp_sf_do_9_2_shut_ctsn), \
 	/* SCTP_STATE_SHUTDOWN_ACK_SENT */ \
 	TYPE_SCTP_FUNC(sctp_sf_discard_chunk), \
 } /* TYPE_SCTP_SHUTDOWN */