sctp: add support for generating stream reconf add incoming/outgoing streams request chunk

This patch is to define Add Incoming/Outgoing Streams Request
Parameter described in rfc6525 section 4.5 and 4.6. They can
be in one same chunk trunk as rfc6525 section 3.1-7 describes,
so make them in one function.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/sctp.h

@@ -742,4 +742,11 @@ struct sctp_strreset_tsnreq {
 	__u32 request_seq;
 };
 
+struct sctp_strreset_addstrm {
+	sctp_paramhdr_t param_hdr;
+	__u32 request_seq;
+	__u16 number_of_streams;
+	__u16 reserved;
+};
+
 #endif /* __LINUX_SCTP_H__ */

include/net/sctp/sm.h

@@ -267,6 +267,9 @@ struct sctp_chunk *sctp_make_strreset_req(
 				bool out, bool in);
 struct sctp_chunk *sctp_make_strreset_tsnreq(
 				const struct sctp_association *asoc);
+struct sctp_chunk *sctp_make_strreset_addstrm(
+				const struct sctp_association *asoc,
+				__u16 out, __u16 in);
 void sctp_chunk_assign_tsn(struct sctp_chunk *);
 void sctp_chunk_assign_ssn(struct sctp_chunk *);
 

net/sctp/sm_make_chunk.c

@@ -3687,3 +3687,49 @@ struct sctp_chunk *sctp_make_strreset_tsnreq(
 
 	return retval;
 }
+
+/* RE-CONFIG 4.5/4.6 (ADD STREAM)
+ *   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 = 17       |      Parameter Length = 12    |
+ *  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *  |          Re-configuration Request Sequence Number             |
+ *  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *  |      Number of new streams    |         Reserved              |
+ *  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ */
+struct sctp_chunk *sctp_make_strreset_addstrm(
+				const struct sctp_association *asoc,
+				__u16 out, __u16 in)
+{
+	struct sctp_strreset_addstrm addstrm;
+	__u16 size = sizeof(addstrm);
+	struct sctp_chunk *retval;
+
+	retval = sctp_make_reconf(asoc, (!!out + !!in) * size);
+	if (!retval)
+		return NULL;
+
+	if (out) {
+		addstrm.param_hdr.type = SCTP_PARAM_RESET_ADD_OUT_STREAMS;
+		addstrm.param_hdr.length = htons(size);
+		addstrm.number_of_streams = htons(out);
+		addstrm.request_seq = htonl(asoc->strreset_outseq);
+		addstrm.reserved = 0;
+
+		sctp_addto_chunk(retval, size, &addstrm);
+	}
+
+	if (in) {
+		addstrm.param_hdr.type = SCTP_PARAM_RESET_ADD_IN_STREAMS;
+		addstrm.param_hdr.length = htons(size);
+		addstrm.number_of_streams = htons(in);
+		addstrm.request_seq = htonl(asoc->strreset_outseq + !!out);
+		addstrm.reserved = 0;
+
+		sctp_addto_chunk(retval, size, &addstrm);
+	}
+
+	return retval;
+}