1 files changed, 109 insertions, 65 deletions

diff --git a/net/ipv4/tcp_westwood.c b/net/ipv4/tcp_westwood.c
index ef827242c94..b94a04ae2ed 100644
--- a/net/ipv4/tcp_westwood.c
+++ b/net/ipv4/tcp_westwood.c
@@ -1,14 +1,30 @@
 /*
- * TCP Westwood+
+ * TCP Westwood+: end-to-end bandwidth estimation for TCP
  *
- *	Angelo Dell'Aera:	TCP Westwood+ support
+ *      Angelo Dell'Aera: author of the first version of TCP Westwood+ in Linux 2.4
+ *
+ * Support at http://c3lab.poliba.it/index.php/Westwood
+ * Main references in literature:
+ *
+ * - Mascolo S, Casetti, M. Gerla et al.
+ *   "TCP Westwood: bandwidth estimation for TCP" Proc. ACM Mobicom 2001
+ *
+ * - A. Grieco, s. Mascolo
+ *   "Performance evaluation of New Reno, Vegas, Westwood+ TCP" ACM Computer
+ *     Comm. Review, 2004
+ *
+ * - A. Dell'Aera, L. Grieco, S. Mascolo.
+ *   "Linux 2.4 Implementation of Westwood+ TCP with Rate-Halving :
+ *    A Performance Evaluation Over the Internet" (ICC 2004), Paris, June 2004
+ *
+ * Westwood+ employs end-to-end bandwidth measurement to set cwnd and
+ * ssthresh after packet loss. The probing phase is as the original Reno.
  */
 
-#include <linux/config.h>
 #include <linux/mm.h>
 #include <linux/module.h>
 #include <linux/skbuff.h>
-#include <linux/tcp_diag.h>
+#include <linux/inet_diag.h>
 #include <net/tcp.h>
 
 /* TCP Westwood structure */
@@ -22,6 +38,8 @@ struct westwood {
 	u32    accounted;
 	u32    rtt;
 	u32    rtt_min;          /* minimum observed RTT */
+	u8     first_ack;        /* flag which infers that this is the first ack */
+	u8     reset_rtt_min;    /* Reset RTT min to next RTT sample*/
 };
 
 
@@ -40,18 +58,20 @@ struct westwood {
  * way as soon as possible. It will reasonably happen within the first
  * RTT period of the connection lifetime.
  */
-static void tcp_westwood_init(struct tcp_sock *tp)
+static void tcp_westwood_init(struct sock *sk)
 {
-	struct westwood *w = tcp_ca(tp);
+	struct westwood *w = inet_csk_ca(sk);
 
 	w->bk = 0;
-        w->bw_ns_est = 0;
-        w->bw_est = 0;
-        w->accounted = 0;
-        w->cumul_ack = 0;
+	w->bw_ns_est = 0;
+	w->bw_est = 0;
+	w->accounted = 0;
+	w->cumul_ack = 0;
+	w->reset_rtt_min = 1;
 	w->rtt_min = w->rtt = TCP_WESTWOOD_INIT_RTT;
 	w->rtt_win_sx = tcp_time_stamp;
-	w->snd_una = tp->snd_una;
+	w->snd_una = tcp_sk(sk)->snd_una;
+	w->first_ack = 1;
 }
 
 /*
@@ -60,13 +80,19 @@ static void tcp_westwood_init(struct tcp_sock *tp)
  */
 static inline u32 westwood_do_filter(u32 a, u32 b)
 {
-	return (((7 * a) + b) >> 3);
+	return ((7 * a) + b) >> 3;
 }
 
-static inline void westwood_filter(struct westwood *w, u32 delta)
+static void westwood_filter(struct westwood *w, u32 delta)
 {
-	w->bw_ns_est = westwood_do_filter(w->bw_ns_est, w->bk / delta);
-	w->bw_est = westwood_do_filter(w->bw_est, w->bw_ns_est);
+	/* If the filter is empty fill it with the first sample of bandwidth  */
+	if (w->bw_ns_est == 0 && w->bw_est == 0) {
+		w->bw_ns_est = w->bk / delta;
+		w->bw_est = w->bw_ns_est;
+	} else {
+		w->bw_ns_est = westwood_do_filter(w->bw_ns_est, w->bk / delta);
+		w->bw_est = westwood_do_filter(w->bw_est, w->bw_ns_est);
+	}
 }
 
 /*
@@ -74,11 +100,12 @@ static inline void westwood_filter(struct westwood *w, u32 delta)
  * Called after processing group of packets.
  * but all westwood needs is the last sample of srtt.
  */
-static void tcp_westwood_pkts_acked(struct tcp_sock *tp, u32 cnt)
+static void tcp_westwood_pkts_acked(struct sock *sk, u32 cnt, s32 rtt)
 {
-	struct westwood *w = tcp_ca(tp);
-	if (cnt > 0)
-		w->rtt = tp->srtt >> 3;
+	struct westwood *w = inet_csk_ca(sk);
+
+	if (rtt > 0)
+		w->rtt = usecs_to_jiffies(rtt);
 }
 
 /*
@@ -86,11 +113,20 @@ static void tcp_westwood_pkts_acked(struct tcp_sock *tp, u32 cnt)
  * It updates RTT evaluation window if it is the right moment to do
  * it. If so it calls filter for evaluating bandwidth.
  */
-static void westwood_update_window(struct tcp_sock *tp)
+static void westwood_update_window(struct sock *sk)
 {
-	struct westwood *w = tcp_ca(tp);
+	struct westwood *w = inet_csk_ca(sk);
 	s32 delta = tcp_time_stamp - w->rtt_win_sx;
 
+	/* Initialize w->snd_una with the first acked sequence number in order
+	 * to fix mismatch between tp->snd_una and w->snd_una for the first
+	 * bandwidth sample
+	 */
+	if (w->first_ack) {
+		w->snd_una = tcp_sk(sk)->snd_una;
+		w->first_ack = 0;
+	}
+
 	/*
 	 * See if a RTT-window has passed.
 	 * Be careful since if RTT is less than
@@ -108,21 +144,32 @@ static void westwood_update_window(struct tcp_sock *tp)
 	}
 }
 
+static inline void update_rtt_min(struct westwood *w)
+{
+	if (w->reset_rtt_min) {
+		w->rtt_min = w->rtt;
+		w->reset_rtt_min = 0;
+	} else
+		w->rtt_min = min(w->rtt, w->rtt_min);
+}
+
+
 /*
  * @westwood_fast_bw
  * It is called when we are in fast path. In particular it is called when
  * header prediction is successful. In such case in fact update is
  * straight forward and doesn't need any particular care.
  */
-static inline void westwood_fast_bw(struct tcp_sock *tp)
+static inline void westwood_fast_bw(struct sock *sk)
 {
-	struct westwood *w = tcp_ca(tp);
+	const struct tcp_sock *tp = tcp_sk(sk);
+	struct westwood *w = inet_csk_ca(sk);
 
-	westwood_update_window(tp);
+	westwood_update_window(sk);
 
 	w->bk += tp->snd_una - w->snd_una;
 	w->snd_una = tp->snd_una;
-	w->rtt_min = min(w->rtt, w->rtt_min);
+	update_rtt_min(w);
 }
 
 /*
@@ -130,21 +177,22 @@ static inline void westwood_fast_bw(struct tcp_sock *tp)
  * This function evaluates cumul_ack for evaluating bk in case of
  * delayed or partial acks.
  */
-static inline u32 westwood_acked_count(struct tcp_sock *tp)
+static inline u32 westwood_acked_count(struct sock *sk)
 {
-	struct westwood *w = tcp_ca(tp);
+	const struct tcp_sock *tp = tcp_sk(sk);
+	struct westwood *w = inet_csk_ca(sk);
 
 	w->cumul_ack = tp->snd_una - w->snd_una;
 
-        /* If cumul_ack is 0 this is a dupack since it's not moving
-         * tp->snd_una.
-         */
-        if (!w->cumul_ack) {
+	/* If cumul_ack is 0 this is a dupack since it's not moving
+	 * tp->snd_una.
+	 */
+	if (!w->cumul_ack) {
 		w->accounted += tp->mss_cache;
 		w->cumul_ack = tp->mss_cache;
 	}
 
-        if (w->cumul_ack > tp->mss_cache) {
+	if (w->cumul_ack > tp->mss_cache) {
 		/* Partial or delayed ack */
 		if (w->accounted >= w->cumul_ack) {
 			w->accounted -= w->cumul_ack;
@@ -160,11 +208,6 @@ static inline u32 westwood_acked_count(struct tcp_sock *tp)
 	return w->cumul_ack;
 }
 
-static inline u32 westwood_bw_rttmin(const struct tcp_sock *tp)
-{
-	struct westwood *w = tcp_ca(tp);
-	return max_t(u32, (w->bw_est * w->rtt_min) / tp->mss_cache, 2);
-}
 
 /*
  * TCP Westwood
@@ -172,32 +215,37 @@ static inline u32 westwood_bw_rttmin(const struct tcp_sock *tp)
  * in packets we use mss_cache). Rttmin is guaranteed to be >= 2
  * so avoids ever returning 0.
  */
-static u32 tcp_westwood_cwnd_min(struct tcp_sock *tp)
+static u32 tcp_westwood_bw_rttmin(const struct sock *sk)
 {
-	return westwood_bw_rttmin(tp);
+	const struct tcp_sock *tp = tcp_sk(sk);
+	const struct westwood *w = inet_csk_ca(sk);
+	return max_t(u32, (w->bw_est * w->rtt_min) / tp->mss_cache, 2);
 }
 
-static void tcp_westwood_event(struct tcp_sock *tp, enum tcp_ca_event event)
+static void tcp_westwood_event(struct sock *sk, enum tcp_ca_event event)
 {
-	struct westwood *w = tcp_ca(tp);
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct westwood *w = inet_csk_ca(sk);
 
-	switch(event) {
+	switch (event) {
 	case CA_EVENT_FAST_ACK:
-		westwood_fast_bw(tp);
+		westwood_fast_bw(sk);
 		break;
 
 	case CA_EVENT_COMPLETE_CWR:
-		tp->snd_cwnd = tp->snd_ssthresh = westwood_bw_rttmin(tp);
+		tp->snd_cwnd = tp->snd_ssthresh = tcp_westwood_bw_rttmin(sk);
 		break;
 
-	case CA_EVENT_FRTO:
-		tp->snd_ssthresh = westwood_bw_rttmin(tp);
+	case CA_EVENT_LOSS:
+		tp->snd_ssthresh = tcp_westwood_bw_rttmin(sk);
+		/* Update RTT_min when next ack arrives */
+		w->reset_rtt_min = 1;
 		break;
 
 	case CA_EVENT_SLOW_ACK:
-		westwood_update_window(tp);
-		w->bk += westwood_acked_count(tp);
-		w->rtt_min = min(w->rtt, w->rtt_min);
+		westwood_update_window(sk);
+		w->bk += westwood_acked_count(sk);
+		update_rtt_min(w);
 		break;
 
 	default:
@@ -208,30 +256,26 @@ static void tcp_westwood_event(struct tcp_sock *tp, enum tcp_ca_event event)
 
 
 /* Extract info for Tcp socket info provided via netlink. */
-static void tcp_westwood_info(struct tcp_sock *tp, u32 ext,
+static void tcp_westwood_info(struct sock *sk, u32 ext,
 			      struct sk_buff *skb)
 {
-	const struct westwood *ca = tcp_ca(tp);
-	if (ext & (1<<(TCPDIAG_VEGASINFO-1))) {
-		struct rtattr *rta;
-		struct tcpvegas_info *info;
-
-		rta = __RTA_PUT(skb, TCPDIAG_VEGASINFO, sizeof(*info));
-		info = RTA_DATA(rta);
-		info->tcpv_enabled = 1;
-		info->tcpv_rttcnt = 0;
-		info->tcpv_rtt = jiffies_to_usecs(ca->rtt);
-		info->tcpv_minrtt = jiffies_to_usecs(ca->rtt_min);
-	rtattr_failure:	;
+	const struct westwood *ca = inet_csk_ca(sk);
+	if (ext & (1 << (INET_DIAG_VEGASINFO - 1))) {
+		struct tcpvegas_info info = {
+			.tcpv_enabled = 1,
+			.tcpv_rtt = jiffies_to_usecs(ca->rtt),
+			.tcpv_minrtt = jiffies_to_usecs(ca->rtt_min),
+		};
+
+		nla_put(skb, INET_DIAG_VEGASINFO, sizeof(info), &info);
 	}
 }
 
 
-static struct tcp_congestion_ops tcp_westwood = {
+static struct tcp_congestion_ops tcp_westwood __read_mostly = {
 	.init		= tcp_westwood_init,
 	.ssthresh	= tcp_reno_ssthresh,
 	.cong_avoid	= tcp_reno_cong_avoid,
-	.min_cwnd	= tcp_westwood_cwnd_min,
 	.cwnd_event	= tcp_westwood_event,
 	.get_info	= tcp_westwood_info,
 	.pkts_acked	= tcp_westwood_pkts_acked,
@@ -242,7 +286,7 @@ static struct tcp_congestion_ops tcp_westwood = {
 
 static int __init tcp_westwood_register(void)
 {
-	BUG_ON(sizeof(struct westwood) > TCP_CA_PRIV_SIZE);
+	BUILD_BUG_ON(sizeof(struct westwood) > ICSK_CA_PRIV_SIZE);
 	return tcp_register_congestion_control(&tcp_westwood);
 }