sctp: introduce round robin stream scheduler

This patch introduces RFC Draft ndata section 3.2 Priority Based
Scheduler (SCTP_SS_RR).

Works by maintaining a list of enqueued streams and tracking the last
one used to send data. When the datamsg is done, it switches to the next
stream.

See-also: https://tools.ietf.org/html/draft-ietf-tsvwg-sctp-ndata-13
Tested-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 0 deletions

diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index 40eb8d6..16f949e 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -1348,6 +1348,10 @@ struct sctp_stream_out_ext {
 			struct list_head prio_list;
 			struct sctp_stream_priorities *prio_head;
 		};
+		/* Fields used by RR scheduler */
+		struct {
+			struct list_head rr_list;
+		};
 	};
 };
 
@@ -1374,6 +1378,13 @@ struct sctp_stream {
 			/* List of priorities scheduled */
 			struct list_head prio_list;
 		};
+		/* Fields used by RR scheduler */
+		struct {
+			/* List of streams scheduled */
+			struct list_head rr_list;
+			/* The next stream stream in line */
+			struct sctp_stream_out_ext *rr_next;
+		};
 	};
 };