sctp: Bring SCTP_DELAYED_ACK socket option into API compliance

Brings delayed_ack socket option set/get into line with the latest ietf
socket extensions API draft, while maintaining backwards compatibility.

Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 4 deletions

diff --git a/net/sctp/sm_sideeffect.c b/net/sctp/sm_sideeffect.c
index 23a9f1a95b7d..b083312c725a 100644
--- a/net/sctp/sm_sideeffect.c
+++ b/net/sctp/sm_sideeffect.c
@@ -190,20 +190,28 @@ static int sctp_gen_sack(struct sctp_association *asoc, int force,
          * unacknowledged DATA chunk. ...
          */
         if (!asoc->peer.sack_needed) {
-                /* We will need a SACK for the next packet.  */
-                asoc->peer.sack_needed = 1;
+                asoc->peer.sack_cnt++;
 
                 /* Set the SACK delay timeout based on the
                  * SACK delay for the last transport
                  * data was received from, or the default
                  * for the association.
                  */
-                if (trans)
+                if (trans) {
+                        /* We will need a SACK for the next packet.  */
+                        if (asoc->peer.sack_cnt >= trans->sackfreq - 1)
+                                asoc->peer.sack_needed = 1;
+
                         asoc->timeouts[SCTP_EVENT_TIMEOUT_SACK] =
                                 trans->sackdelay;
-                else
+                } else {
+                        /* We will need a SACK for the next packet.  */
+                        if (asoc->peer.sack_cnt >= asoc->sackfreq - 1)
+                                asoc->peer.sack_needed = 1;
+
                         asoc->timeouts[SCTP_EVENT_TIMEOUT_SACK] =
                                 asoc->sackdelay;
+                }
 
                 /* Restart the SACK timer. */
                 sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_RESTART,
@@ -216,6 +224,7 @@ static int sctp_gen_sack(struct sctp_association *asoc, int force,
                         goto nomem;
 
                 asoc->peer.sack_needed = 0;
+                asoc->peer.sack_cnt = 0;
 
                 sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(sack));