Tunes and fixes the new DC-CC to seem to hit the

right mix.  Still may need some tweaks but it
appears to almost not give away too much to an
RFC2581 flow, but can really minimize the amount of
buffers used in the net.

MFC after:	3 months

1 files changed, 415 insertions, 135 deletions

diff --git a/sys/netinet/sctp_cc_functions.c b/sys/netinet/sctp_cc_functions.c
index dd5aab0..3d52820 100644
--- a/sys/netinet/sctp_cc_functions.c
+++ b/sys/netinet/sctp_cc_functions.c
@@ -185,6 +185,328 @@ sctp_cwnd_update_after_fr(struct sctp_tcb *stcb,
 	}
 }
 
+/* Defines for instantaneous bw decisions */
+#define SCTP_INST_LOOSING 1	/* Loosing to other flows */
+#define SCTP_INST_NEUTRAL 2	/* Neutral, no indication */
+#define SCTP_INST_GAINING 3	/* Gaining, step down possible */
+
+
+static int
+cc_bw_same(struct sctp_tcb *stcb, struct sctp_nets *net, uint64_t nbw,
+    uint64_t rtt_offset, uint64_t vtag, uint8_t inst_ind)
+{
+	uint64_t oth, probepoint;
+
+	probepoint = (((uint64_t) net->cwnd) << 32);
+	if (net->rtt > net->cc_mod.rtcc.lbw_rtt + rtt_offset) {
+		/*
+		 * rtt increased we don't update bw.. so we don't update the
+		 * rtt either.
+		 */
+		/* Probe point 5 */
+		probepoint |= ((5 << 16) | 1);
+		SDT_PROBE(sctp, cwnd, net, rttvar,
+		    vtag,
+		    ((net->cc_mod.rtcc.lbw << 32) | nbw),
+		    ((net->cc_mod.rtcc.lbw_rtt << 32) | net->rtt),
+		    net->flight_size,
+		    probepoint);
+		if ((net->cc_mod.rtcc.steady_step) && (inst_ind != SCTP_INST_LOOSING)) {
+			if (net->cc_mod.rtcc.last_step_state == 5)
+				net->cc_mod.rtcc.step_cnt++;
+			else
+				net->cc_mod.rtcc.step_cnt = 1;
+			net->cc_mod.rtcc.last_step_state = 5;
+			if ((net->cc_mod.rtcc.step_cnt == net->cc_mod.rtcc.steady_step) ||
+			    ((net->cc_mod.rtcc.step_cnt > net->cc_mod.rtcc.steady_step) &&
+			    ((net->cc_mod.rtcc.step_cnt % net->cc_mod.rtcc.steady_step) == 0))) {
+				/* Try a step down */
+				oth = net->cc_mod.rtcc.vol_reduce;
+				oth <<= 16;
+				oth |= net->cc_mod.rtcc.step_cnt;
+				oth <<= 16;
+				oth |= net->cc_mod.rtcc.last_step_state;
+				SDT_PROBE(sctp, cwnd, net, rttstep,
+				    vtag,
+				    ((net->cc_mod.rtcc.lbw << 32) | nbw),
+				    ((net->cc_mod.rtcc.lbw_rtt << 32) | net->rtt),
+				    oth,
+				    probepoint);
+				if (net->cwnd > (4 * net->mtu)) {
+					net->cwnd -= net->mtu;
+					net->cc_mod.rtcc.vol_reduce++;
+				} else {
+					net->cc_mod.rtcc.step_cnt = 0;
+				}
+			}
+		}
+		return (1);
+	}
+	if (net->rtt < net->cc_mod.rtcc.lbw_rtt - rtt_offset) {
+		/*
+		 * rtt decreased, there could be more room. we update both
+		 * the bw and the rtt here to lock this in as a good step
+		 * down.
+		 */
+		/* Probe point 6 */
+		probepoint |= ((6 << 16) | 0);
+		SDT_PROBE(sctp, cwnd, net, rttvar,
+		    vtag,
+		    ((net->cc_mod.rtcc.lbw << 32) | nbw),
+		    ((net->cc_mod.rtcc.lbw_rtt << 32) | net->rtt),
+		    net->flight_size,
+		    probepoint);
+		if (net->cc_mod.rtcc.steady_step) {
+			oth = net->cc_mod.rtcc.vol_reduce;
+			oth <<= 16;
+			oth |= net->cc_mod.rtcc.step_cnt;
+			oth <<= 16;
+			oth |= net->cc_mod.rtcc.last_step_state;
+			SDT_PROBE(sctp, cwnd, net, rttstep,
+			    vtag,
+			    ((net->cc_mod.rtcc.lbw << 32) | nbw),
+			    ((net->cc_mod.rtcc.lbw_rtt << 32) | net->rtt),
+			    oth,
+			    probepoint);
+			if ((net->cc_mod.rtcc.last_step_state == 5) &&
+			    (net->cc_mod.rtcc.step_cnt > net->cc_mod.rtcc.steady_step)) {
+				/* Step down worked */
+				net->cc_mod.rtcc.step_cnt = 0;
+				return (1);
+			} else {
+				net->cc_mod.rtcc.last_step_state = 6;
+				net->cc_mod.rtcc.step_cnt = 0;
+			}
+		}
+		net->cc_mod.rtcc.lbw = nbw;
+		net->cc_mod.rtcc.lbw_rtt = net->rtt;
+		net->cc_mod.rtcc.cwnd_at_bw_set = net->cwnd;
+		if (inst_ind == SCTP_INST_GAINING)
+			return (1);
+		else if (inst_ind == SCTP_INST_NEUTRAL)
+			return (1);
+		else
+			return (0);
+	}
+	/*
+	 * Ok bw and rtt remained the same .. no update to any
+	 */
+	/* Probe point 7 */
+	probepoint |= ((7 << 16) | net->cc_mod.rtcc.ret_from_eq);
+	SDT_PROBE(sctp, cwnd, net, rttvar,
+	    vtag,
+	    ((net->cc_mod.rtcc.lbw << 32) | nbw),
+	    ((net->cc_mod.rtcc.lbw_rtt << 32) | net->rtt),
+	    net->flight_size,
+	    probepoint);
+
+	if ((net->cc_mod.rtcc.steady_step) && (inst_ind != SCTP_INST_LOOSING)) {
+		if (net->cc_mod.rtcc.last_step_state == 5)
+			net->cc_mod.rtcc.step_cnt++;
+		else
+			net->cc_mod.rtcc.step_cnt = 1;
+		net->cc_mod.rtcc.last_step_state = 5;
+		if ((net->cc_mod.rtcc.step_cnt == net->cc_mod.rtcc.steady_step) ||
+		    ((net->cc_mod.rtcc.step_cnt > net->cc_mod.rtcc.steady_step) &&
+		    ((net->cc_mod.rtcc.step_cnt % net->cc_mod.rtcc.steady_step) == 0))) {
+			/* Try a step down */
+			if (net->cwnd > (4 * net->mtu)) {
+				net->cwnd -= net->mtu;
+				net->cc_mod.rtcc.vol_reduce++;
+				return (1);
+			} else {
+				net->cc_mod.rtcc.step_cnt = 0;
+			}
+		}
+	}
+	if (inst_ind == SCTP_INST_GAINING)
+		return (1);
+	else if (inst_ind == SCTP_INST_NEUTRAL)
+		return (1);
+	else
+		return ((int)net->cc_mod.rtcc.ret_from_eq);
+}
+
+static int
+cc_bw_decrease(struct sctp_tcb *stcb, struct sctp_nets *net, uint64_t nbw, uint64_t rtt_offset,
+    uint64_t vtag, uint8_t inst_ind)
+{
+	uint64_t oth, probepoint;
+
+	/* Bandwidth decreased. */
+	probepoint = (((uint64_t) net->cwnd) << 32);
+	if (net->rtt > net->cc_mod.rtcc.lbw_rtt + rtt_offset) {
+		/* rtt increased */
+		/* Did we add more */
+		if ((net->cwnd > net->cc_mod.rtcc.cwnd_at_bw_set) &&
+		    (inst_ind != SCTP_INST_LOOSING)) {
+			/* We caused it maybe.. back off? */
+			/* PROBE POINT 1 */
+			probepoint |= ((1 << 16) | 1);
+			SDT_PROBE(sctp, cwnd, net, rttvar,
+			    vtag,
+			    ((net->cc_mod.rtcc.lbw << 32) | nbw),
+			    ((net->cc_mod.rtcc.lbw_rtt << 32) | net->rtt),
+			    net->flight_size,
+			    probepoint);
+
+			if (net->cc_mod.rtcc.ret_from_eq) {
+				/*
+				 * Switch over to CA if we are less
+				 * aggressive
+				 */
+				net->ssthresh = net->cwnd - 1;
+				net->partial_bytes_acked = 0;
+			}
+			return (1);
+		}
+		/* Probe point 2 */
+		probepoint |= ((2 << 16) | 0);
+		SDT_PROBE(sctp, cwnd, net, rttvar,
+		    vtag,
+		    ((net->cc_mod.rtcc.lbw << 32) | nbw),
+		    ((net->cc_mod.rtcc.lbw_rtt << 32) | net->rtt),
+		    net->flight_size,
+		    probepoint);
+
+		/* Someone else - fight for more? */
+		if (net->cc_mod.rtcc.steady_step) {
+			oth = net->cc_mod.rtcc.vol_reduce;
+			oth <<= 16;
+			oth |= net->cc_mod.rtcc.step_cnt;
+			oth <<= 16;
+			oth |= net->cc_mod.rtcc.last_step_state;
+			SDT_PROBE(sctp, cwnd, net, rttstep,
+			    vtag,
+			    ((net->cc_mod.rtcc.lbw << 32) | nbw),
+			    ((net->cc_mod.rtcc.lbw_rtt << 32) | net->rtt),
+			    oth,
+			    probepoint);
+			/*
+			 * Did we voluntarily give up some? if so take one
+			 * back please
+			 */
+			if ((net->cc_mod.rtcc.vol_reduce) &&
+			    (inst_ind != SCTP_INST_GAINING)) {
+				net->cwnd += net->mtu;
+				net->cc_mod.rtcc.vol_reduce--;
+			}
+			net->cc_mod.rtcc.last_step_state = 2;
+			net->cc_mod.rtcc.step_cnt = 0;
+		}
+		goto out_decision;
+	} else if (net->rtt < net->cc_mod.rtcc.lbw_rtt - rtt_offset) {
+		/* bw & rtt decreased */
+		/* Probe point 3 */
+		probepoint |= ((3 << 16) | 0);
+		SDT_PROBE(sctp, cwnd, net, rttvar,
+		    vtag,
+		    ((net->cc_mod.rtcc.lbw << 32) | nbw),
+		    ((net->cc_mod.rtcc.lbw_rtt << 32) | net->rtt),
+		    net->flight_size,
+		    probepoint);
+		if (net->cc_mod.rtcc.steady_step) {
+			oth = net->cc_mod.rtcc.vol_reduce;
+			oth <<= 16;
+			oth |= net->cc_mod.rtcc.step_cnt;
+			oth <<= 16;
+			oth |= net->cc_mod.rtcc.last_step_state;
+			SDT_PROBE(sctp, cwnd, net, rttstep,
+			    vtag,
+			    ((net->cc_mod.rtcc.lbw << 32) | nbw),
+			    ((net->cc_mod.rtcc.lbw_rtt << 32) | net->rtt),
+			    oth,
+			    probepoint);
+			if ((net->cc_mod.rtcc.vol_reduce) &&
+			    (inst_ind != SCTP_INST_GAINING)) {
+				net->cwnd += net->mtu;
+				net->cc_mod.rtcc.vol_reduce--;
+			}
+			net->cc_mod.rtcc.last_step_state = 3;
+			net->cc_mod.rtcc.step_cnt = 0;
+		}
+		goto out_decision;
+	}
+	/* The bw decreased but rtt stayed the same */
+	/* Probe point 4 */
+	probepoint |= ((4 << 16) | 0);
+	SDT_PROBE(sctp, cwnd, net, rttvar,
+	    vtag,
+	    ((net->cc_mod.rtcc.lbw << 32) | nbw),
+	    ((net->cc_mod.rtcc.lbw_rtt << 32) | net->rtt),
+	    net->flight_size,
+	    probepoint);
+	if (net->cc_mod.rtcc.steady_step) {
+		oth = net->cc_mod.rtcc.vol_reduce;
+		oth <<= 16;
+		oth |= net->cc_mod.rtcc.step_cnt;
+		oth <<= 16;
+		oth |= net->cc_mod.rtcc.last_step_state;
+		SDT_PROBE(sctp, cwnd, net, rttstep,
+		    vtag,
+		    ((net->cc_mod.rtcc.lbw << 32) | nbw),
+		    ((net->cc_mod.rtcc.lbw_rtt << 32) | net->rtt),
+		    oth,
+		    probepoint);
+		if ((net->cc_mod.rtcc.vol_reduce) &&
+		    (inst_ind != SCTP_INST_GAINING)) {
+			net->cwnd += net->mtu;
+			net->cc_mod.rtcc.vol_reduce--;
+		}
+		net->cc_mod.rtcc.last_step_state = 4;
+		net->cc_mod.rtcc.step_cnt = 0;
+	}
+out_decision:
+	net->cc_mod.rtcc.lbw = nbw;
+	net->cc_mod.rtcc.lbw_rtt = net->rtt;
+	net->cc_mod.rtcc.cwnd_at_bw_set = net->cwnd;
+	if (inst_ind == SCTP_INST_GAINING) {
+		return (1);
+	} else {
+		return (0);
+	}
+}
+
+static int
+cc_bw_increase(struct sctp_tcb *stcb, struct sctp_nets *net, uint64_t nbw,
+    uint64_t vtag, uint8_t inst_ind)
+{
+	uint64_t oth, probepoint;
+
+	/*
+	 * BW increased, so update and return 0, since all actions in our
+	 * table say to do the normal CC update. Note that we pay no
+	 * attention to the inst_ind since our overall sum is increasing.
+	 */
+	/* PROBE POINT 0 */
+	probepoint = (((uint64_t) net->cwnd) << 32);
+	SDT_PROBE(sctp, cwnd, net, rttvar,
+	    vtag,
+	    ((net->cc_mod.rtcc.lbw << 32) | nbw),
+	    ((net->cc_mod.rtcc.lbw_rtt << 32) | net->rtt),
+	    net->flight_size,
+	    probepoint);
+	if (net->cc_mod.rtcc.steady_step) {
+		oth = net->cc_mod.rtcc.vol_reduce;
+		oth <<= 16;
+		oth |= net->cc_mod.rtcc.step_cnt;
+		oth <<= 16;
+		oth |= net->cc_mod.rtcc.last_step_state;
+		SDT_PROBE(sctp, cwnd, net, rttstep,
+		    vtag,
+		    ((net->cc_mod.rtcc.lbw << 32) | nbw),
+		    ((net->cc_mod.rtcc.lbw_rtt << 32) | net->rtt),
+		    oth,
+		    probepoint);
+		net->cc_mod.rtcc.last_step_state = 0;
+		net->cc_mod.rtcc.step_cnt = 0;
+		net->cc_mod.rtcc.vol_reduce = 0;
+	}
+	net->cc_mod.rtcc.lbw = nbw;
+	net->cc_mod.rtcc.lbw_rtt = net->rtt;
+	net->cc_mod.rtcc.cwnd_at_bw_set = net->cwnd;
+	return (0);
+}
 
 /* RTCC Algoritm to limit growth of cwnd, return
  * true if you want to NOT allow cwnd growth
@@ -193,6 +515,11 @@ static int
 cc_bw_limit(struct sctp_tcb *stcb, struct sctp_nets *net, uint64_t nbw)
 {
 	uint64_t bw_offset, rtt_offset, rtt, vtag, probepoint;
+	uint64_t bytes_for_this_rtt, inst_bw;
+	uint64_t div, inst_off;
+	int bw_shift;
+	uint8_t inst_ind;
+	int ret;
 
 	/*-
 	 * Here we need to see if we want
@@ -231,151 +558,67 @@ cc_bw_limit(struct sctp_tcb *stcb, struct sctp_nets *net, uint64_t nbw)
 	 * RTT it stayed the same if it did not
 	 * change within 1/32nd
 	 */
+	bw_shift = SCTP_BASE_SYSCTL(sctp_rttvar_bw);
 	rtt = stcb->asoc.my_vtag;
 	vtag = (rtt << 32) | (((uint32_t) (stcb->sctp_ep->sctp_lport)) << 16) | (stcb->rport);
 	probepoint = (((uint64_t) net->cwnd) << 32);
 	rtt = net->rtt;
-	bw_offset = net->cc_mod.rtcc.lbw >> SCTP_BASE_SYSCTL(sctp_rttvar_bw);
-	if (nbw > net->cc_mod.rtcc.lbw + bw_offset) {
-		/*
-		 * BW increased, so update and return 0, since all actions
-		 * in our table say to do the normal CC update
-		 */
-		/* PROBE POINT 0 */
+	if (net->cc_mod.rtcc.rtt_set_this_sack) {
+		net->cc_mod.rtcc.rtt_set_this_sack = 0;
+		bytes_for_this_rtt = net->cc_mod.rtcc.bw_bytes - net->cc_mod.rtcc.bw_bytes_at_last_rttc;
+		net->cc_mod.rtcc.bw_bytes_at_last_rttc = net->cc_mod.rtcc.bw_bytes;
+		if (net->rtt) {
+			div = net->rtt / 1000;
+			if (div) {
+				inst_bw = bytes_for_this_rtt / div;
+				inst_off = inst_bw >> bw_shift;
+				if (inst_bw > nbw)
+					inst_ind = SCTP_INST_GAINING;
+				else if ((inst_bw + inst_off) < nbw)
+					inst_ind = SCTP_INST_LOOSING;
+				else
+					inst_ind = SCTP_INST_NEUTRAL;
+				probepoint |= ((0xb << 16) | inst_ind);
+			} else {
+				inst_bw = bytes_for_this_rtt / (uint64_t) (net->rtt);
+				/* Can't determine do not change */
+				inst_ind = net->cc_mod.rtcc.last_inst_ind;
+				probepoint |= ((0xc << 16) | inst_ind);
+			}
+		} else {
+			inst_bw = bytes_for_this_rtt;
+			/* Can't determine do not change */
+			inst_ind = net->cc_mod.rtcc.last_inst_ind;
+			probepoint |= ((0xd << 16) | inst_ind);
+		}
 		SDT_PROBE(sctp, cwnd, net, rttvar,
 		    vtag,
-		    ((net->cc_mod.rtcc.lbw << 32) | nbw),
-		    net->cc_mod.rtcc.lbw_rtt,
-		    rtt,
+		    ((nbw << 32) | inst_bw),
+		    ((net->cc_mod.rtcc.lbw_rtt << 32) | rtt),
+		    net->flight_size,
 		    probepoint);
-		net->cc_mod.rtcc.lbw = nbw;
-		net->cc_mod.rtcc.lbw_rtt = rtt;
-		net->cc_mod.rtcc.cwnd_at_bw_set = net->cwnd;
-		return (0);
+	} else {
+		/* No rtt measurement, use last one */
+		inst_ind = net->cc_mod.rtcc.last_inst_ind;
+	}
+	bw_offset = net->cc_mod.rtcc.lbw >> bw_shift;
+	if (nbw > net->cc_mod.rtcc.lbw + bw_offset) {
+		ret = cc_bw_increase(stcb, net, nbw, vtag, inst_ind);
+		goto out;
 	}
 	rtt_offset = net->cc_mod.rtcc.lbw_rtt >> SCTP_BASE_SYSCTL(sctp_rttvar_rtt);
 	if (nbw < net->cc_mod.rtcc.lbw - bw_offset) {
-		/* Bandwidth decreased. */
-		if (rtt > net->cc_mod.rtcc.lbw_rtt + rtt_offset) {
-			/* rtt increased */
-			/* Did we add more */
-			if (net->cwnd > net->cc_mod.rtcc.cwnd_at_bw_set) {
-				/* We caused it maybe.. back off */
-				/* PROBE POINT 1 */
-				probepoint |= ((1 << 16) | 1);
-				SDT_PROBE(sctp, cwnd, net, rttvar,
-				    vtag,
-				    ((net->cc_mod.rtcc.lbw << 32) | nbw),
-				    net->cc_mod.rtcc.lbw_rtt,
-				    rtt,
-				    probepoint);
-
-				net->cc_mod.rtcc.lbw = nbw;
-				net->cc_mod.rtcc.lbw_rtt = rtt;
-				net->cwnd = net->cc_mod.rtcc.cwnd_at_bw_set;
-				if (net->cc_mod.rtcc.ret_from_eq) {
-					/*
-					 * Switch over to CA if we are less
-					 * aggressive
-					 */
-					net->ssthresh = net->cwnd - 1;
-					net->partial_bytes_acked = 0;
-				}
-				return (1);
-			}
-			/* Probe point 2 */
-			probepoint |= ((2 << 16) | 0);
-			SDT_PROBE(sctp, cwnd, net, rttvar,
-			    vtag,
-			    ((net->cc_mod.rtcc.lbw << 32) | nbw),
-			    net->cc_mod.rtcc.lbw_rtt,
-			    rtt,
-			    probepoint);
-
-			/* Someone else - fight for more? */
-			net->cc_mod.rtcc.lbw = nbw;
-			net->cc_mod.rtcc.lbw_rtt = rtt;
-			net->cc_mod.rtcc.cwnd_at_bw_set = net->cwnd;
-			return (0);
-		} else if (rtt < net->cc_mod.rtcc.lbw_rtt - rtt_offset) {
-			/* rtt decreased */
-			/* Probe point 3 */
-			probepoint |= ((3 << 16) | 0);
-			SDT_PROBE(sctp, cwnd, net, rttvar,
-			    vtag,
-			    ((net->cc_mod.rtcc.lbw << 32) | nbw),
-			    net->cc_mod.rtcc.lbw_rtt,
-			    rtt,
-			    probepoint);
-			net->cc_mod.rtcc.lbw = nbw;
-			net->cc_mod.rtcc.lbw_rtt = rtt;
-			net->cc_mod.rtcc.cwnd_at_bw_set = net->cwnd;
-			return (0);
-		}
-		/* The bw decreased but rtt stayed the same */
-		net->cc_mod.rtcc.lbw = nbw;
-		net->cc_mod.rtcc.lbw_rtt = rtt;
-		net->cc_mod.rtcc.cwnd_at_bw_set = net->cwnd;
-		/* Probe point 4 */
-		probepoint |= ((4 << 16) | 0);
-		SDT_PROBE(sctp, cwnd, net, rttvar,
-		    vtag,
-		    ((net->cc_mod.rtcc.lbw << 32) | nbw),
-		    net->cc_mod.rtcc.lbw_rtt,
-		    rtt,
-		    probepoint);
-		return (0);
+		ret = cc_bw_decrease(stcb, net, nbw, rtt_offset, vtag, inst_ind);
+		goto out;
 	}
 	/*
 	 * If we reach here then we are in a situation where the bw stayed
 	 * the same.
 	 */
-	if (rtt > net->cc_mod.rtcc.lbw_rtt + rtt_offset) {
-		/*
-		 * rtt increased we don't update bw.. so we don't update the
-		 * rtt either.
-		 */
-		/* Probe point 5 */
-		probepoint |= ((5 << 16) | 1);
-		SDT_PROBE(sctp, cwnd, net, rttvar,
-		    vtag,
-		    ((net->cc_mod.rtcc.lbw << 32) | nbw),
-		    net->cc_mod.rtcc.lbw_rtt,
-		    rtt,
-		    probepoint);
-		return (1);
-	}
-	if (rtt < net->cc_mod.rtcc.lbw_rtt - rtt_offset) {
-		/*
-		 * rtt decreased, there could be more room. we update both
-		 * the bw and the rtt here.
-		 */
-		/* Probe point 6 */
-		probepoint |= ((6 << 16) | 0);
-		SDT_PROBE(sctp, cwnd, net, rttvar,
-		    vtag,
-		    ((net->cc_mod.rtcc.lbw << 32) | nbw),
-		    net->cc_mod.rtcc.lbw_rtt,
-		    rtt,
-		    probepoint);
-		net->cc_mod.rtcc.lbw = nbw;
-		net->cc_mod.rtcc.lbw_rtt = rtt;
-		net->cc_mod.rtcc.cwnd_at_bw_set = net->cwnd;
-		return (0);
-	}
-	/*
-	 * Ok bw and rtt remained the same .. no update to any but save the
-	 * latest cwnd.
-	 */
-	/* Probe point 7 */
-	probepoint |= ((7 << 16) | net->cc_mod.rtcc.ret_from_eq);
-	SDT_PROBE(sctp, cwnd, net, rttvar,
-	    vtag,
-	    ((net->cc_mod.rtcc.lbw << 32) | nbw),
-	    net->cc_mod.rtcc.lbw_rtt,
-	    rtt,
-	    probepoint);
-	return ((int)net->cc_mod.rtcc.ret_from_eq);
+	ret = cc_bw_same(stcb, net, nbw, rtt_offset, vtag, inst_ind);
+out:
+	net->cc_mod.rtcc.last_inst_ind = inst_ind;
+	return (ret);
 }
 
 static void
@@ -554,11 +797,15 @@ sctp_cwnd_update_after_sack_common(struct sctp_tcb *stcb,
 				SDT_PROBE(sctp, cwnd, net, rttvar,
 				    vtag,
 				    nbw,
-				    0,
-				    net->rtt,
+				    ((net->cc_mod.rtcc.lbw_rtt << 32) | net->rtt),
+				    net->flight_size,
 				    probepoint);
 				net->cc_mod.rtcc.lbw = nbw;
 				net->cc_mod.rtcc.lbw_rtt = net->rtt;
+				if (net->cc_mod.rtcc.rtt_set_this_sack) {
+					net->cc_mod.rtcc.rtt_set_this_sack = 0;
+					net->cc_mod.rtcc.bw_bytes_at_last_rttc = net->cc_mod.rtcc.bw_bytes;
+				}
 			}
 		}
 		/*
@@ -1014,15 +1261,22 @@ sctp_cwnd_new_rtcc_transmission_begins(struct sctp_tcb *stcb,
 		SDT_PROBE(sctp, cwnd, net, rttvar,
 		    vtag,
 		    ((net->cc_mod.rtcc.lbw << 32) | 0),
-		    net->cc_mod.rtcc.lbw_rtt,
-		    0,
+		    ((net->cc_mod.rtcc.lbw_rtt << 32) | net->rtt),
+		    net->flight_size,
 		    probepoint);
 		net->cc_mod.rtcc.lbw_rtt = 0;
 		net->cc_mod.rtcc.cwnd_at_bw_set = 0;
 		net->cc_mod.rtcc.lbw = 0;
+		net->cc_mod.rtcc.bw_bytes_at_last_rttc = 0;
+		net->cc_mod.rtcc.vol_reduce = 0;
 		net->cc_mod.rtcc.bw_tot_time = 0;
 		net->cc_mod.rtcc.bw_bytes = 0;
 		net->cc_mod.rtcc.tls_needs_set = 0;
+		if (net->cc_mod.rtcc.steady_step) {
+			net->cc_mod.rtcc.vol_reduce = 0;
+			net->cc_mod.rtcc.step_cnt = 0;
+			net->cc_mod.rtcc.last_step_state = 0;
+		}
 		if (net->cc_mod.rtcc.ret_from_eq) {
 			/* less aggressive one - reset cwnd too */
 			uint32_t cwnd_in_mtu, cwnd;
@@ -1075,11 +1329,20 @@ sctp_set_rtcc_initial_cc_param(struct sctp_tcb *stcb,
 	    probepoint);
 	net->cc_mod.rtcc.lbw_rtt = 0;
 	net->cc_mod.rtcc.cwnd_at_bw_set = 0;
+	net->cc_mod.rtcc.vol_reduce = 0;
 	net->cc_mod.rtcc.lbw = 0;
+	net->cc_mod.rtcc.vol_reduce = 0;
+	net->cc_mod.rtcc.bw_bytes_at_last_rttc = 0;
 	net->cc_mod.rtcc.bw_tot_time = 0;
 	net->cc_mod.rtcc.bw_bytes = 0;
 	net->cc_mod.rtcc.tls_needs_set = 0;
 	net->cc_mod.rtcc.ret_from_eq = SCTP_BASE_SYSCTL(sctp_rttvar_eqret);
+	net->cc_mod.rtcc.steady_step = SCTP_BASE_SYSCTL(sctp_steady_step);
+	net->cc_mod.rtcc.use_dccc_ecn = SCTP_BASE_SYSCTL(sctp_use_dccc_ecn);
+	net->cc_mod.rtcc.step_cnt = 0;
+	net->cc_mod.rtcc.last_step_state = 0;
+
+
 }
 
 static int
@@ -1106,6 +1369,10 @@ sctp_cwnd_rtcc_socket_option(struct sctp_tcb *stcb, int setorget,
 			TAILQ_FOREACH(net, &stcb->asoc.nets, sctp_next) {
 				net->cc_mod.rtcc.use_dccc_ecn = cc_opt->aid_value.assoc_value;
 			}
+		} else if (cc_opt->option == SCTP_CC_OPT_STEADY_STEP) {
+			TAILQ_FOREACH(net, &stcb->asoc.nets, sctp_next) {
+				net->cc_mod.rtcc.steady_step = cc_opt->aid_value.assoc_value;
+			}
 		} else {
 			return (EINVAL);
 		}
@@ -1123,6 +1390,12 @@ sctp_cwnd_rtcc_socket_option(struct sctp_tcb *stcb, int setorget,
 				return (EFAULT);
 			}
 			cc_opt->aid_value.assoc_value = net->cc_mod.rtcc.use_dccc_ecn;
+		} else if (cc_opt->option == SCTP_CC_OPT_STEADY_STEP) {
+			net = TAILQ_FIRST(&stcb->asoc.nets);
+			if (net == NULL) {
+				return (EFAULT);
+			}
+			cc_opt->aid_value.assoc_value = net->cc_mod.rtcc.steady_step;
 		} else {
 			return (EINVAL);
 		}
@@ -1149,6 +1422,12 @@ sctp_cwnd_update_rtcc_after_sack(struct sctp_tcb *stcb,
 	sctp_cwnd_update_after_sack_common(stcb, asoc, accum_moved, reneged_all, will_exit, 1);
 }
 
+static void
+sctp_rtt_rtcc_calculated(struct sctp_tcb *stcb,
+    struct sctp_nets *net, struct timeval *now)
+{
+	net->cc_mod.rtcc.rtt_set_this_sack = 1;
+}
 
 /* Here starts Sally Floyds HS-TCP */
 
@@ -2203,6 +2482,7 @@ struct sctp_cc_functions sctp_cc_functions[] = {
 		.sctp_cwnd_update_tsn_acknowledged = sctp_cwnd_update_rtcc_tsn_acknowledged,
 		.sctp_cwnd_new_transmission_begins = sctp_cwnd_new_rtcc_transmission_begins,
 		.sctp_cwnd_prepare_net_for_sack = sctp_cwnd_prepare_rtcc_net_for_sack,
-		.sctp_cwnd_socket_option = sctp_cwnd_rtcc_socket_option
+		.sctp_cwnd_socket_option = sctp_cwnd_rtcc_socket_option,
+		.sctp_rtt_calculated = sctp_rtt_rtcc_calculated
 	}
 };