sctp: add basic structures and make chunk function for ifwdtsn

sctp_ifwdtsn_skip, sctp_ifwdtsn_hdr and sctp_ifwdtsn_chunk are used to
define and parse I-FWD TSN chunk format, and sctp_make_ifwdtsn is a
function to build the chunk.

The I-FORWARD-TSN Chunk Format is defined in section 2.3.1 of RFC8260.

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

1 files changed, 24 insertions, 0 deletions

diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index 23a7313d7972..b9b269cf615e 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -3536,6 +3536,30 @@ struct sctp_chunk *sctp_make_fwdtsn(const struct sctp_association *asoc,
 	return retval;
 }
 
+struct sctp_chunk *sctp_make_ifwdtsn(const struct sctp_association *asoc,
+				     __u32 new_cum_tsn, size_t nstreams,
+				     struct sctp_ifwdtsn_skip *skiplist)
+{
+	struct sctp_chunk *retval = NULL;
+	struct sctp_ifwdtsn_hdr ftsn_hdr;
+	size_t hint;
+
+	hint = (nstreams + 1) * sizeof(__u32);
+
+	retval = sctp_make_control(asoc, SCTP_CID_I_FWD_TSN, 0, hint,
+				   GFP_ATOMIC);
+	if (!retval)
+		return NULL;
+
+	ftsn_hdr.new_cum_tsn = htonl(new_cum_tsn);
+	retval->subh.ifwdtsn_hdr =
+		sctp_addto_chunk(retval, sizeof(ftsn_hdr), &ftsn_hdr);
+
+	sctp_addto_chunk(retval, nstreams * sizeof(skiplist[0]), skiplist);
+
+	return retval;
+}
+
 /* RE-CONFIG 3.1 (RE-CONFIG chunk)
  *   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