1 files changed, 297 insertions, 14 deletions

diff --git a/release/src/linux/linux/net/ipv4/tcp_input.c b/release/src/linux/linux/net/ipv4/tcp_input.c
index 8c99dd52..243e2991 100644
--- a/release/src/linux/linux/net/ipv4/tcp_input.c
+++ b/release/src/linux/linux/net/ipv4/tcp_input.c
@@ -87,6 +87,16 @@ int sysctl_tcp_stdurg = 0;
 int sysctl_tcp_rfc1337 = 0;
 int sysctl_tcp_max_orphans = NR_FILE;
 
+int sysctl_tcp_vegas_cong_avoid = 0;
+
+/* Default values of the Vegas variables, in fixed-point representation
+ * with V_PARAM_SHIFT bits to the right of the binary point.
+ */
+#define V_PARAM_SHIFT 1
+int sysctl_tcp_vegas_alpha = 1<<V_PARAM_SHIFT;
+int sysctl_tcp_vegas_beta  = 3<<V_PARAM_SHIFT;
+int sysctl_tcp_vegas_gamma = 1<<V_PARAM_SHIFT;
+
 #define FLAG_DATA		0x01 /* Incoming frame contained data.		*/
 #define FLAG_WIN_UPDATE		0x02 /* Incoming ACK was a window update.	*/
 #define FLAG_DATA_ACKED		0x04 /* This ACK acknowledged new data.		*/
@@ -399,6 +409,42 @@ static void tcp_event_data_recv(struct sock *sk, struct tcp_opt *tp, struct sk_b
 		tcp_grow_window(sk, tp, skb);
 }
 
+/* Set up a new TCP connection, depending on whether it should be
+ * using Vegas or not.
+ */    
+void tcp_vegas_init(struct tcp_opt *tp)
+{
+	if (sysctl_tcp_vegas_cong_avoid) {
+		tp->vegas.do_vegas = 1;
+		tp->vegas.baseRTT = 0x7fffffff;
+		tcp_vegas_enable(tp);
+	} else 
+		tcp_vegas_disable(tp);
+}
+
+/* Do RTT sampling needed for Vegas.
+ * Basically we:
+ *   o min-filter RTT samples from within an RTT to get the current
+ *     propagation delay + queuing delay (we are min-filtering to try to
+ *     avoid the effects of delayed ACKs)
+ *   o min-filter RTT samples from a much longer window (forever for now)
+ *     to find the propagation delay (baseRTT)
+ */
+static inline void vegas_rtt_calc(struct tcp_opt *tp, __u32 rtt)
+{
+	__u32 vrtt = rtt + 1; /* Never allow zero rtt or baseRTT */
+
+	/* Filter to find propagation delay: */
+	if (vrtt < tp->vegas.baseRTT) 
+		tp->vegas.baseRTT = vrtt;
+
+	/* Find the min RTT during the last RTT to find
+	 * the current prop. delay + queuing delay:
+	 */
+	tp->vegas.minRTT = min(tp->vegas.minRTT, vrtt);
+	tp->vegas.cntRTT++;
+}
+
 /* Called to compute a smoothed rtt estimate. The data fed to this
  * routine either comes from timestamps, or from segments that were
  * known _not_ to have been retransmitted [see Karn/Partridge
@@ -412,6 +458,9 @@ static __inline__ void tcp_rtt_estimator(struct tcp_opt *tp, __u32 mrtt)
 {
 	long m = mrtt; /* RTT */
 
+	if (tcp_vegas_enabled(tp))
+		vegas_rtt_calc(tp, mrtt);
+
 	/*	The following amusing code comes from Jacobson's
 	 *	article in SIGCOMM '88.  Note that rtt and mdev
 	 *	are scaled versions of rtt and mean deviation.
@@ -1013,7 +1062,7 @@ void tcp_enter_loss(struct sock *sk, int how)
 	tcp_sync_left_out(tp);
 
 	tp->reordering = min_t(unsigned int, tp->reordering, sysctl_tcp_reordering);
-	tp->ca_state = TCP_CA_Loss;
+	tcp_set_ca_state(tp, TCP_CA_Loss);
 	tp->high_seq = tp->snd_nxt;
 	TCP_ECN_queue_cwr(tp);
 }
@@ -1375,7 +1424,7 @@ static int tcp_try_undo_recovery(struct sock *sk, struct tcp_opt *tp)
 		tcp_moderate_cwnd(tp);
 		return 1;
 	}
-	tp->ca_state = TCP_CA_Open;
+	tcp_set_ca_state(tp, TCP_CA_Open);
 	return 0;
 }
 
@@ -1435,7 +1484,7 @@ static int tcp_try_undo_loss(struct sock *sk, struct tcp_opt *tp)
 		tp->retransmits = 0;
 		tp->undo_marker = 0;
 		if (!IsReno(tp))
-			tp->ca_state = TCP_CA_Open;
+			tcp_set_ca_state(tp, TCP_CA_Open);
 		return 1;
 	}
 	return 0;
@@ -1466,7 +1515,7 @@ static void tcp_try_to_open(struct sock *sk, struct tcp_opt *tp, int flag)
 			state = TCP_CA_Disorder;
 
 		if (tp->ca_state != state) {
-			tp->ca_state = state;
+			tcp_set_ca_state(tp, state);
 			tp->high_seq = tp->snd_nxt;
 		}
 		tcp_moderate_cwnd(tp);
@@ -1540,7 +1589,7 @@ tcp_fastretrans_alert(struct sock *sk, u32 prior_snd_una,
 			 * is ACKed for CWR bit to reach receiver. */
 			if (tp->snd_una != tp->high_seq) {
 				tcp_complete_cwr(tp);
-				tp->ca_state = TCP_CA_Open;
+				tcp_set_ca_state(tp, TCP_CA_Open);
 			}
 			break;
 
@@ -1551,7 +1600,7 @@ tcp_fastretrans_alert(struct sock *sk, u32 prior_snd_una,
 			     * catching for all duplicate ACKs. */
 			    IsReno(tp) || tp->snd_una != tp->high_seq) {
 				tp->undo_marker = 0;
-				tp->ca_state = TCP_CA_Open;
+				tcp_set_ca_state(tp, TCP_CA_Open);
 			}
 			break;
 
@@ -1625,7 +1674,7 @@ tcp_fastretrans_alert(struct sock *sk, u32 prior_snd_una,
 		}
 
 		tp->snd_cwnd_cnt = 0;
-		tp->ca_state = TCP_CA_Recovery;
+		tcp_set_ca_state(tp, TCP_CA_Recovery);
 	}
 
 	if (is_dupack || tcp_head_timedout(sk, tp))
@@ -1696,7 +1745,7 @@ tcp_ack_update_rtt(struct tcp_opt *tp, int flag, s32 seq_rtt)
 /* This is Jacobson's slow start and congestion avoidance. 
  * SIGCOMM '88, p. 328.
  */
-static __inline__ void tcp_cong_avoid(struct tcp_opt *tp)
+static __inline__ void reno_cong_avoid(struct tcp_opt *tp)
 {
         if (tp->snd_cwnd <= tp->snd_ssthresh) {
                 /* In "safe" area, increase. */
@@ -1716,6 +1765,236 @@ static __inline__ void tcp_cong_avoid(struct tcp_opt *tp)
 	tp->snd_cwnd_stamp = tcp_time_stamp;
 }
 
+/* This is based on the congestion detection/avoidance scheme described in
+ *    Lawrence S. Brakmo and Larry L. Peterson.
+ *    "TCP Vegas: End to end congestion avoidance on a global internet."
+ *    IEEE Journal on Selected Areas in Communication, 13(8):1465--1480,
+ *    October 1995. Available from:
+ *	ftp://ftp.cs.arizona.edu/xkernel/Papers/jsac.ps
+ *
+ * See http://www.cs.arizona.edu/xkernel/ for their implementation.
+ * The main aspects that distinguish this implementation from the
+ * Arizona Vegas implementation are:
+ *   o We do not change the loss detection or recovery mechanisms of
+ *     Linux in any way. Linux already recovers from losses quite well,
+ *     using fine-grained timers, NewReno, and FACK.
+ *   o To avoid the performance penalty imposed by increasing cwnd
+ *     only every-other RTT during slow start, we increase during
+ *     every RTT during slow start, just like Reno.
+ *   o Largely to allow continuous cwnd growth during slow start,
+ *     we use the rate at which ACKs come back as the "actual"
+ *     rate, rather than the rate at which data is sent.
+ *   o To speed convergence to the right rate, we set the cwnd
+ *     to achieve the right ("actual") rate when we exit slow start.
+ *   o To filter out the noise caused by delayed ACKs, we use the
+ *     minimum RTT sample observed during the last RTT to calculate
+ *     the actual rate.
+ *   o When the sender re-starts from idle, it waits until it has
+ *     received ACKs for an entire flight of new data before making
+ *     a cwnd adjustment decision. The original Vegas implementation
+ *     assumed senders never went idle.
+ */
+static void vegas_cong_avoid(struct tcp_opt *tp, u32 ack, u32 seq_rtt)
+{
+	/* The key players are v_beg_snd_una and v_beg_snd_nxt.
+	 *
+	 * These are so named because they represent the approximate values
+	 * of snd_una and snd_nxt at the beginning of the current RTT. More
+	 * precisely, they represent the amount of data sent during the RTT.
+	 * At the end of the RTT, when we receive an ACK for v_beg_snd_nxt,
+	 * we will calculate that (v_beg_snd_nxt - v_beg_snd_una) outstanding
+	 * bytes of data have been ACKed during the course of the RTT, giving
+	 * an "actual" rate of:
+	 *
+	 *     (v_beg_snd_nxt - v_beg_snd_una) / (rtt duration)
+	 *
+	 * Unfortunately, v_beg_snd_una is not exactly equal to snd_una,
+	 * because delayed ACKs can cover more than one segment, so they
+	 * don't line up nicely with the boundaries of RTTs.
+	 *
+	 * Another unfortunate fact of life is that delayed ACKs delay the
+	 * advance of the left edge of our send window, so that the number
+	 * of bytes we send in an RTT is often less than our cwnd will allow.
+	 * So we keep track of our cwnd separately, in v_beg_snd_cwnd.
+	 */
+
+	if (after(ack, tp->vegas.beg_snd_nxt)) {
+		/* Do the Vegas once-per-RTT cwnd adjustment. */
+		u32 old_wnd, old_snd_cwnd;
+
+		
+		/* Here old_wnd is essentially the window of data that was
+		 * sent during the previous RTT, and has all
+		 * been acknowledged in the course of the RTT that ended
+		 * with the ACK we just received. Likewise, old_snd_cwnd
+		 * is the cwnd during the previous RTT.
+		 */
+		old_wnd = (tp->vegas.beg_snd_nxt - tp->vegas.beg_snd_una) /
+			tp->mss_cache;
+		old_snd_cwnd = tp->vegas.beg_snd_cwnd;
+
+		/* Save the extent of the current window so we can use this
+		 * at the end of the next RTT.
+		 */
+		tp->vegas.beg_snd_una  = tp->vegas.beg_snd_nxt;
+		tp->vegas.beg_snd_nxt  = tp->snd_nxt;
+		tp->vegas.beg_snd_cwnd = tp->snd_cwnd;
+
+		/* Take into account the current RTT sample too, to
+		 * decrease the impact of delayed acks. This double counts
+		 * this sample since we count it for the next window as well,
+		 * but that's not too awful, since we're taking the min,
+		 * rather than averaging.
+		 */
+		vegas_rtt_calc(tp, seq_rtt);
+
+		/* We do the Vegas calculations only if we got enough RTT
+		 * samples that we can be reasonably sure that we got
+		 * at least one RTT sample that wasn't from a delayed ACK.
+		 * If we only had 2 samples total,
+		 * then that means we're getting only 1 ACK per RTT, which
+		 * means they're almost certainly delayed ACKs.
+		 * If  we have 3 samples, we should be OK.
+		 */
+
+		if (tp->vegas.cntRTT <= 2) {
+			/* We don't have enough RTT samples to do the Vegas
+			 * calculation, so we'll behave like Reno.
+			 */
+			if (tp->snd_cwnd > tp->snd_ssthresh)
+				tp->snd_cwnd++;
+		} else {
+			u32 rtt, target_cwnd, diff;
+
+			/* We have enough RTT samples, so, using the Vegas
+			 * algorithm, we determine if we should increase or
+			 * decrease cwnd, and by how much.
+			 */
+
+			/* Pluck out the RTT we are using for the Vegas
+			 * calculations. This is the min RTT seen during the
+			 * last RTT. Taking the min filters out the effects
+			 * of delayed ACKs, at the cost of noticing congestion
+			 * a bit later.
+			 */
+			rtt = tp->vegas.minRTT;
+
+			/* Calculate the cwnd we should have, if we weren't
+			 * going too fast.
+			 *
+			 * This is:
+			 *     (actual rate in segments) * baseRTT
+			 * We keep it as a fixed point number with
+			 * V_PARAM_SHIFT bits to the right of the binary point.
+			 */
+			target_cwnd = ((old_wnd * tp->vegas.baseRTT)
+				       << V_PARAM_SHIFT) / rtt;
+
+			/* Calculate the difference between the window we had,
+			 * and the window we would like to have. This quantity
+			 * is the "Diff" from the Arizona Vegas papers.
+			 *
+			 * Again, this is a fixed point number with
+			 * V_PARAM_SHIFT bits to the right of the binary
+			 * point.
+			 */
+			diff = (old_wnd << V_PARAM_SHIFT) - target_cwnd;
+
+			if (tp->snd_cwnd < tp->snd_ssthresh) {
+				/* Slow start.  */
+				if (diff > sysctl_tcp_vegas_gamma) {
+					/* Going too fast. Time to slow down
+					 * and switch to congestion avoidance.
+					 */
+					tp->snd_ssthresh = 2;
+
+					/* Set cwnd to match the actual rate
+					 * exactly:
+					 *   cwnd = (actual rate) * baseRTT
+					 * Then we add 1 because the integer
+					 * truncation robs us of full link
+					 * utilization.
+					 */
+					tp->snd_cwnd = min(tp->snd_cwnd,
+							   (target_cwnd >>
+							    V_PARAM_SHIFT)+1);
+
+				}
+			} else {
+				/* Congestion avoidance. */
+				u32 next_snd_cwnd;
+
+				/* Figure out where we would like cwnd
+				 * to be.
+				 */
+				if (diff > sysctl_tcp_vegas_beta) {
+					/* The old window was too fast, so
+					 * we slow down.
+					 */
+					next_snd_cwnd = old_snd_cwnd - 1;
+				} else if (diff < sysctl_tcp_vegas_alpha) {
+					/* We don't have enough extra packets
+					 * in the network, so speed up.
+					 */
+					next_snd_cwnd = old_snd_cwnd + 1;
+				} else {
+					/* Sending just as fast as we
+					 * should be.
+					 */
+					next_snd_cwnd = old_snd_cwnd;
+				}
+
+				/* Adjust cwnd upward or downward, toward the
+				 * desired value.
+				 */
+				if (next_snd_cwnd > tp->snd_cwnd)
+					tp->snd_cwnd++;
+				else if (next_snd_cwnd < tp->snd_cwnd)
+					tp->snd_cwnd--;
+			}
+		}
+
+		/* Wipe the slate clean for the next RTT. */
+		tp->vegas.cntRTT = 0;
+		tp->vegas.minRTT = 0x7fffffff;
+	}
+
+	/* The following code is executed for every ack we receive,
+	 * except for conditions checked in should_advance_cwnd()
+	 * before the call to tcp_cong_avoid(). Mainly this means that
+	 * we only execute this code if the ack actually acked some
+	 * data.
+	 */
+
+	/* If we are in slow start, increase our cwnd in response to this ACK.
+	 * (If we are not in slow start then we are in congestion avoidance,
+	 * and adjust our congestion window only once per RTT. See the code
+	 * above.)
+	 */
+	if (tp->snd_cwnd <= tp->snd_ssthresh) 
+		tp->snd_cwnd++;
+
+	/* to keep cwnd from growing without bound */
+	tp->snd_cwnd = min_t(u32, tp->snd_cwnd, tp->snd_cwnd_clamp);
+
+	/* Make sure that we are never so timid as to reduce our cwnd below
+	 * 2 MSS.
+	 *
+	 * Going below 2 MSS would risk huge delayed ACKs from our receiver.
+	 */
+	tp->snd_cwnd = max(tp->snd_cwnd, 2U);
+
+	tp->snd_cwnd_stamp = tcp_time_stamp;
+}
+
+static inline void tcp_cong_avoid(struct tcp_opt *tp, u32 ack, u32 seq_rtt)
+{
+	if (tcp_vegas_enabled(tp))
+		vegas_cong_avoid(tp, ack, seq_rtt);
+	else
+		reno_cong_avoid(tp);
+}
+
 /* Restart timer after forward progress on connection.
  * RFC2988 recommends to restart timer to now+rto.
  */
@@ -1730,7 +2009,7 @@ static __inline__ void tcp_ack_packets_out(struct sock *sk, struct tcp_opt *tp)
 }
 
 /* Remove acknowledged frames from the retransmission queue. */
-static int tcp_clean_rtx_queue(struct sock *sk)
+static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p)
 {
 	struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
 	struct sk_buff *skb;
@@ -1813,6 +2092,7 @@ static int tcp_clean_rtx_queue(struct sock *sk)
 		}
 	}
 #endif
+	*seq_rtt_p = seq_rtt;
 	return acked;
 }
 
@@ -1900,6 +2180,7 @@ static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
 	u32 ack_seq = TCP_SKB_CB(skb)->seq;
 	u32 ack = TCP_SKB_CB(skb)->ack_seq;
 	u32 prior_in_flight;
+	s32 seq_rtt;
 	int prior_packets;
 
 	/* If the ack is newer than sent or older than previous acks
@@ -1947,17 +2228,19 @@ static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
 	prior_in_flight = tcp_packets_in_flight(tp);
 
 	/* See if we can take anything off of the retransmit queue. */
-	flag |= tcp_clean_rtx_queue(sk);
+	flag |= tcp_clean_rtx_queue(sk, &seq_rtt);
 
 	if (tcp_ack_is_dubious(tp, flag)) {
 		/* Advanve CWND, if state allows this. */
-		if ((flag&FLAG_DATA_ACKED) && prior_in_flight >= tp->snd_cwnd &&
+		if ((flag&FLAG_DATA_ACKED) &&
+		    (tcp_vegas_enabled(tp) || prior_in_flight >= tp->snd_cwnd) &&
 		    tcp_may_raise_cwnd(tp, flag))
-			tcp_cong_avoid(tp);
+			tcp_cong_avoid(tp, ack, seq_rtt);
 		tcp_fastretrans_alert(sk, prior_snd_una, prior_packets, flag);
 	} else {
-		if ((flag&FLAG_DATA_ACKED) && prior_in_flight >= tp->snd_cwnd)
-			tcp_cong_avoid(tp);
+		if ((flag & FLAG_DATA_ACKED) &&
+		    (tcp_vegas_enabled(tp) || prior_in_flight >= tp->snd_cwnd))
+			tcp_cong_avoid(tp, ack, seq_rtt);
 	}
 
 	if ((flag & FLAG_FORWARD_PROGRESS) || !(flag&FLAG_NOT_DUP))