sctp: implement make_datafrag for sctp_stream_interleave

To avoid hundreds of checks for the different process on I-DATA chunk,
struct sctp_stream_interleave is defined as a group of functions used
to replace the codes in some place where it needs to do different job
according to if the asoc intl_enabled is set.

With these ops, it only needs to initialize asoc->stream.si with
sctp_stream_interleave_0 for normal data if asoc intl_enable is 0,
or sctp_stream_interleave_1 for idata if asoc intl_enable is set in
sctp_stream_init.

After that, the members in asoc->stream.si can be used directly in
some special places without checking asoc intl_enable.

make_datafrag is the first member for sctp_stream_interleave, it's
used to make data or idata frags, called in sctp_datamsg_from_user.
The old function sctp_make_datafrag_empty needs to be adjust some
to fit in this ops.

Note that as idata and data chunks have different length, it also
defines data_chunk_len for sctp_stream_interleave to describe the
chunk size.

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

3 files changed, 58 insertions, 3 deletions

diff --git a/include/net/sctp/sm.h b/include/net/sctp/sm.h
index 5389ae034cfa..f950186aae34 100644
--- a/include/net/sctp/sm.h
+++ b/include/net/sctp/sm.h
@@ -199,10 +199,9 @@ struct sctp_chunk *sctp_make_cwr(const struct sctp_association *asoc,
 				 const struct sctp_chunk *chunk);
 struct sctp_chunk *sctp_make_idata(const struct sctp_association *asoc,
 				   __u8 flags, int paylen, gfp_t gfp);
-struct sctp_chunk *sctp_make_datafrag_empty(struct sctp_association *asoc,
+struct sctp_chunk *sctp_make_datafrag_empty(const struct sctp_association *asoc,
 					    const struct sctp_sndrcvinfo *sinfo,
-					    int len, const __u8 flags,
-					    __u16 ssn, gfp_t gfp);
+					    int len, __u8 flags, gfp_t gfp);
 struct sctp_chunk *sctp_make_ecne(const struct sctp_association *asoc,
 				  const __u32 lowest_tsn);
 struct sctp_chunk *sctp_make_sack(const struct sctp_association *asoc);
diff --git a/include/net/sctp/stream_interleave.h b/include/net/sctp/stream_interleave.h
new file mode 100644
index 000000000000..7b9fa8dbe620
--- /dev/null
+++ b/include/net/sctp/stream_interleave.h
@@ -0,0 +1,44 @@
+/* SCTP kernel implementation
+ * (C) Copyright Red Hat Inc. 2017
+ *
+ * These are definitions used by the stream schedulers, defined in RFC
+ * draft ndata (https://tools.ietf.org/html/draft-ietf-tsvwg-sctp-ndata-11)
+ *
+ * This SCTP implementation is free software;
+ * you can redistribute it and/or modify it under the terms of
+ * the GNU General Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * This SCTP implementation  is distributed in the hope that it
+ * will be useful, but WITHOUT ANY WARRANTY; without even the implied
+ *                 ************************
+ * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GNU CC; see the file COPYING.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ * Please send any bug reports or fixes you make to the
+ * email addresses:
+ *    lksctp developers <linux-sctp@vger.kernel.org>
+ *
+ * Written or modified by:
+ *   Xin Long <lucien.xin@gmail.com>
+ */
+
+#ifndef __sctp_stream_interleave_h__
+#define __sctp_stream_interleave_h__
+
+struct sctp_stream_interleave {
+	__u16	data_chunk_len;
+	/* (I-)DATA process */
+	struct sctp_chunk *(*make_datafrag)(const struct sctp_association *asoc,
+					    const struct sctp_sndrcvinfo *sinfo,
+					    int len, __u8 flags, gfp_t gfp);
+};
+
+void sctp_stream_interleave_init(struct sctp_stream *stream);
+
+#endif /* __sctp_stream_interleave_h__ */
diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index 7026a8039367..96cc898787f1 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -89,6 +89,7 @@ struct sctp_stream;
 #include <net/sctp/tsnmap.h>
 #include <net/sctp/ulpevent.h>
 #include <net/sctp/ulpqueue.h>
+#include <net/sctp/stream_interleave.h>
 
 /* Structures useful for managing bind/connect. */
 
@@ -1389,11 +1390,22 @@ struct sctp_stream {
 			struct sctp_stream_out_ext *rr_next;
 		};
 	};
+	struct sctp_stream_interleave *si;
 };
 
 #define SCTP_STREAM_CLOSED		0x00
 #define SCTP_STREAM_OPEN		0x01
 
+static inline __u16 sctp_datachk_len(const struct sctp_stream *stream)
+{
+	return stream->si->data_chunk_len;
+}
+
+static inline __u16 sctp_datahdr_len(const struct sctp_stream *stream)
+{
+	return stream->si->data_chunk_len - sizeof(struct sctp_chunkhdr);
+}
+
 /* SCTP_GET_ASSOC_STATS counters */
 struct sctp_priv_assoc_stats {
 	/* Maximum observed rto in the association during subsequent