sctp: implement the sender side for SACK-IMMEDIATELY extension

This patch implement the sender side for SACK-IMMEDIATELY
extension.

  Section 4.1.  Sender Side Considerations

  Whenever the sender of a DATA chunk can benefit from the
  corresponding SACK chunk being sent back without delay, the sender
  MAY set the I-bit in the DATA chunk header.

  Reasons for setting the I-bit include

  o  The sender is in the SHUTDOWN-PENDING state.

  o  The application requests to set the I-bit of the last DATA chunk
     of a user message when providing the user message to the SCTP
     implementation.

Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>

2 files changed, 21 insertions, 1 deletions

diff --git a/net/sctp/chunk.c b/net/sctp/chunk.c
index acf7c4d128f7..8e4320040f05 100644
--- a/net/sctp/chunk.c
+++ b/net/sctp/chunk.c
@@ -263,9 +263,18 @@ struct sctp_datamsg *sctp_datamsg_from_user(struct sctp_association *asoc,
                 if (0 == i)
                         frag |= SCTP_DATA_FIRST_FRAG;
 
-                if ((i == (whole - 1)) && !over)
+                if ((i == (whole - 1)) && !over) {
                         frag |= SCTP_DATA_LAST_FRAG;
 
+                        /* The application requests to set the I-bit of the
+                         * last DATA chunk of a user message when providing
+                         * the user message to the SCTP implementation.
+                         */
+                        if ((sinfo->sinfo_flags & SCTP_EOF) ||
+                            (sinfo->sinfo_flags & SCTP_SACK_IMMEDIATELY))
+                                frag |= SCTP_DATA_SACK_IMM;
+                }
+
                 chunk = sctp_make_datafrag_empty(asoc, sinfo, len, frag, 0);
 
                 if (!chunk)
@@ -297,6 +306,10 @@ struct sctp_datamsg *sctp_datamsg_from_user(struct sctp_association *asoc,
                 else
                         frag = SCTP_DATA_LAST_FRAG;
 
+                if ((sinfo->sinfo_flags & SCTP_EOF) ||
+                    (sinfo->sinfo_flags & SCTP_SACK_IMMEDIATELY))
+                        frag |= SCTP_DATA_SACK_IMM;
+
                 chunk = sctp_make_datafrag_empty(asoc, sinfo, over, frag, 0);
 
                 if (!chunk)
diff --git a/net/sctp/outqueue.c b/net/sctp/outqueue.c
index c9f20e28521b..5732661c87d3 100644
--- a/net/sctp/outqueue.c
+++ b/net/sctp/outqueue.c
@@ -1011,6 +1011,13 @@ static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout)
                                 break;
 
                         case SCTP_XMIT_OK:
+                                /* The sender is in the SHUTDOWN-PENDING state,
+                                 * The sender MAY set the I-bit in the DATA
+                                 * chunk header.
+                                 */
+                                if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
+                                        chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
+
                                 break;
 
                         default: