sctp: add support for generating stream reconf ssn/tsn reset request chunk

This patch is to define SSN/TSN Reset Request Parameter described
in rfc6525 section 4.3.
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/sctp.h

@@ -737,4 +737,9 @@ struct sctp_strreset_inreq {
 	__u16 list_of_streams[0];
 };
 
+struct sctp_strreset_tsnreq {
+	sctp_paramhdr_t param_hdr;
+	__u32 request_seq;
+};
+
 #endif /* __LINUX_SCTP_H__ */

include/net/sctp/sm.h

@@ -265,6 +265,8 @@ struct sctp_chunk *sctp_make_strreset_req(
 				const struct sctp_association *asoc,
 				__u16 stream_num, __u16 *stream_list,
 				bool out, bool in);
+struct sctp_chunk *sctp_make_strreset_tsnreq(
+				const struct sctp_association *asoc);
 void sctp_chunk_assign_tsn(struct sctp_chunk *);
 void sctp_chunk_assign_ssn(struct sctp_chunk *);
 

net/sctp/sm_make_chunk.c

@@ -3658,3 +3658,32 @@ struct sctp_chunk *sctp_make_strreset_req(
 
 	return retval;
 }
+
+/* RE-CONFIG 4.3 (SSN/TSN RESET ALL)
+ *   0                   1                   2                   3
+ *   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ *  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *  |     Parameter Type = 15       |      Parameter Length = 8     |
+ *  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *  |         Re-configuration Request Sequence Number              |
+ *  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ */
+struct sctp_chunk *sctp_make_strreset_tsnreq(
+				const struct sctp_association *asoc)
+{
+	struct sctp_strreset_tsnreq tsnreq;
+	__u16 length = sizeof(tsnreq);
+	struct sctp_chunk *retval;
+
+	retval = sctp_make_reconf(asoc, length);
+	if (!retval)
+		return NULL;
+
+	tsnreq.param_hdr.type = SCTP_PARAM_RESET_TSN_REQUEST;
+	tsnreq.param_hdr.length = htons(length);
+	tsnreq.request_seq = htonl(asoc->strreset_outseq);
+
+	sctp_addto_chunk(retval, sizeof(tsnreq), &tsnreq);
+
+	return retval;
+}