tcp: replace cnt & rtt with struct in pkts_acked()

Replace 2 arguments (cnt and rtt) in the congestion control modules'
pkts_acked() function with a struct. This will allow adding more
information without having to modify existing congestion control
modules (tcp_nv in particular needs bytes in flight when packet
was sent).

As proposed by Neal Cardwell in his comments to the tcp_nv patch.
Signed-off-by: Lawrence Brakmo <brakmo@fb.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/tcp.h

@@ -854,6 +854,11 @@ enum tcp_ca_ack_event_flags {
 
 union tcp_cc_info;
 
+struct ack_sample {
+	u32 pkts_acked;
+	s32 rtt_us;
+};
+
 struct tcp_congestion_ops {
 	struct list_head	list;
 	u32 key;
@@ -877,7 +882,7 @@ struct tcp_congestion_ops {
 	/* new value of cwnd after loss (optional) */
 	u32  (*undo_cwnd)(struct sock *sk);
 	/* hook for packet ack accounting (optional) */
-	void (*pkts_acked)(struct sock *sk, u32 num_acked, s32 rtt_us);
+	void (*pkts_acked)(struct sock *sk, const struct ack_sample *sample);
 	/* get info for inet_diag (optional) */
 	size_t (*get_info)(struct sock *sk, u32 ext, int *attr,
 			   union tcp_cc_info *info);

net/ipv4/tcp_bic.c

@@ -197,15 +197,15 @@ static void bictcp_state(struct sock *sk, u8 new_state)
 /* Track delayed acknowledgment ratio using sliding window
  * ratio = (15*ratio + sample) / 16
  */
-static void bictcp_acked(struct sock *sk, u32 cnt, s32 rtt)
+static void bictcp_acked(struct sock *sk, const struct ack_sample *sample)
 {
 	const struct inet_connection_sock *icsk = inet_csk(sk);
 
 	if (icsk->icsk_ca_state == TCP_CA_Open) {
 		struct bictcp *ca = inet_csk_ca(sk);
 
-		cnt -= ca->delayed_ack >> ACK_RATIO_SHIFT;
-		ca->delayed_ack += cnt;
+		ca->delayed_ack += sample->pkts_acked -
+			(ca->delayed_ack >> ACK_RATIO_SHIFT);
 	}
 }
 

net/ipv4/tcp_cdg.c

@@ -294,12 +294,12 @@ static void tcp_cdg_cong_avoid(struct sock *sk, u32 ack, u32 acked)
 	ca->shadow_wnd = max(ca->shadow_wnd, ca->shadow_wnd + incr);
 }
 
-static void tcp_cdg_acked(struct sock *sk, u32 num_acked, s32 rtt_us)
+static void tcp_cdg_acked(struct sock *sk, const struct ack_sample *sample)
 {
 	struct cdg *ca = inet_csk_ca(sk);
 	struct tcp_sock *tp = tcp_sk(sk);
 
-	if (rtt_us <= 0)
+	if (sample->rtt_us <= 0)
 		return;
 
 	/* A heuristic for filtering delayed ACKs, adapted from:
@@ -307,20 +307,20 @@ static void tcp_cdg_acked(struct sock *sk, u32 num_acked, s32 rtt_us)
 	 * delay and rate based TCP mechanisms." TR 100219A. CAIA, 2010.
 	 */
 	if (tp->sacked_out == 0) {
-		if (num_acked == 1 && ca->delack) {
+		if (sample->pkts_acked == 1 && ca->delack) {
 			/* A delayed ACK is only used for the minimum if it is
 			 * provenly lower than an existing non-zero minimum.
 			 */
-			ca->rtt.min = min(ca->rtt.min, rtt_us);
+			ca->rtt.min = min(ca->rtt.min, sample->rtt_us);
 			ca->delack--;
 			return;
-		} else if (num_acked > 1 && ca->delack < 5) {
+		} else if (sample->pkts_acked > 1 && ca->delack < 5) {
 			ca->delack++;
 		}
 	}
 
-	ca->rtt.min = min_not_zero(ca->rtt.min, rtt_us);
-	ca->rtt.max = max(ca->rtt.max, rtt_us);
+	ca->rtt.min = min_not_zero(ca->rtt.min, sample->rtt_us);
+	ca->rtt.max = max(ca->rtt.max, sample->rtt_us);
 }
 
 static u32 tcp_cdg_ssthresh(struct sock *sk)

net/ipv4/tcp_cubic.c

@@ -437,21 +437,21 @@ static void hystart_update(struct sock *sk, u32 delay)
 /* Track delayed acknowledgment ratio using sliding window
  * ratio = (15*ratio + sample) / 16
  */
-static void bictcp_acked(struct sock *sk, u32 cnt, s32 rtt_us)
+static void bictcp_acked(struct sock *sk, const struct ack_sample *sample)
 {
 	const struct tcp_sock *tp = tcp_sk(sk);
 	struct bictcp *ca = inet_csk_ca(sk);
 	u32 delay;
 
 	/* Some calls are for duplicates without timetamps */
-	if (rtt_us < 0)
+	if (sample->rtt_us < 0)
 		return;
 
 	/* Discard delay samples right after fast recovery */
 	if (ca->epoch_start && (s32)(tcp_time_stamp - ca->epoch_start) < HZ)
 		return;
 
-	delay = (rtt_us << 3) / USEC_PER_MSEC;
+	delay = (sample->rtt_us << 3) / USEC_PER_MSEC;
 	if (delay == 0)
 		delay = 1;
 

net/ipv4/tcp_htcp.c

@@ -99,7 +99,7 @@ static inline void measure_rtt(struct sock *sk, u32 srtt)
 }
 
 static void measure_achieved_throughput(struct sock *sk,
-					u32 pkts_acked, s32 rtt)
+					const struct ack_sample *sample)
 {
 	const struct inet_connection_sock *icsk = inet_csk(sk);
 	const struct tcp_sock *tp = tcp_sk(sk);
@@ -107,10 +107,10 @@ static void measure_achieved_throughput(struct sock *sk,
 	u32 now = tcp_time_stamp;
 
 	if (icsk->icsk_ca_state == TCP_CA_Open)
-		ca->pkts_acked = pkts_acked;
+		ca->pkts_acked = sample->pkts_acked;
 
-	if (rtt > 0)
-		measure_rtt(sk, usecs_to_jiffies(rtt));
+	if (sample->rtt_us > 0)
+		measure_rtt(sk, usecs_to_jiffies(sample->rtt_us));
 
 	if (!use_bandwidth_switch)
 		return;
@@ -122,7 +122,7 @@ static void measure_achieved_throughput(struct sock *sk,
 		return;
 	}
 
-	ca->packetcount += pkts_acked;
+	ca->packetcount += sample->pkts_acked;
 
 	if (ca->packetcount >= tp->snd_cwnd - (ca->alpha >> 7 ? : 1) &&
 	    now - ca->lasttime >= ca->minRTT &&

net/ipv4/tcp_illinois.c

@@ -82,30 +82,31 @@ static void tcp_illinois_init(struct sock *sk)
 }
 
 /* Measure RTT for each ack. */
-static void tcp_illinois_acked(struct sock *sk, u32 pkts_acked, s32 rtt)
+static void tcp_illinois_acked(struct sock *sk, const struct ack_sample *sample)
 {
 	struct illinois *ca = inet_csk_ca(sk);
+	s32 rtt_us = sample->rtt_us;
 
-	ca->acked = pkts_acked;
+	ca->acked = sample->pkts_acked;
 
 	/* dup ack, no rtt sample */
-	if (rtt < 0)
+	if (rtt_us < 0)
 		return;
 
 	/* ignore bogus values, this prevents wraparound in alpha math */
-	if (rtt > RTT_MAX)
-		rtt = RTT_MAX;
+	if (rtt_us > RTT_MAX)
+		rtt_us = RTT_MAX;
 
 	/* keep track of minimum RTT seen so far */
-	if (ca->base_rtt > rtt)
-		ca->base_rtt = rtt;
+	if (ca->base_rtt > rtt_us)
+		ca->base_rtt = rtt_us;
 
 	/* and max */
-	if (ca->max_rtt < rtt)
-		ca->max_rtt = rtt;
+	if (ca->max_rtt < rtt_us)
+		ca->max_rtt = rtt_us;
 
 	++ca->cnt_rtt;
-	ca->sum_rtt += rtt;
+	ca->sum_rtt += rtt_us;
 }
 
 /* Maximum queuing delay */

net/ipv4/tcp_input.c

@@ -3248,8 +3248,12 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
 		tcp_rearm_rto(sk);
 	}
 
-	if (icsk->icsk_ca_ops->pkts_acked)
-		icsk->icsk_ca_ops->pkts_acked(sk, pkts_acked, ca_rtt_us);
+	if (icsk->icsk_ca_ops->pkts_acked) {
+		struct ack_sample sample = { .pkts_acked = pkts_acked,
+					     .rtt_us = ca_rtt_us };
+
+		icsk->icsk_ca_ops->pkts_acked(sk, &sample);
+	}
 
 #if FASTRETRANS_DEBUG > 0
 	WARN_ON((int)tp->sacked_out < 0);

net/ipv4/tcp_lp.c

@@ -260,13 +260,13 @@ static void tcp_lp_rtt_sample(struct sock *sk, u32 rtt)
  * newReno in increase case.
  * We work it out by following the idea from TCP-LP's paper directly
  */
-static void tcp_lp_pkts_acked(struct sock *sk, u32 num_acked, s32 rtt_us)
+static void tcp_lp_pkts_acked(struct sock *sk, const struct ack_sample *sample)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct lp *lp = inet_csk_ca(sk);
 
-	if (rtt_us > 0)
-		tcp_lp_rtt_sample(sk, rtt_us);
+	if (sample->rtt_us > 0)
+		tcp_lp_rtt_sample(sk, sample->rtt_us);
 
 	/* calc inference */
 	if (tcp_time_stamp > tp->rx_opt.rcv_tsecr)

net/ipv4/tcp_vegas.c

@@ -107,16 +107,16 @@ EXPORT_SYMBOL_GPL(tcp_vegas_init);
  *   o min-filter RTT samples from a much longer window (forever for now)
  *     to find the propagation delay (baseRTT)
  */
-void tcp_vegas_pkts_acked(struct sock *sk, u32 cnt, s32 rtt_us)
+void tcp_vegas_pkts_acked(struct sock *sk, const struct ack_sample *sample)
 {
 	struct vegas *vegas = inet_csk_ca(sk);
 	u32 vrtt;
 
-	if (rtt_us < 0)
+	if (sample->rtt_us < 0)
 		return;
 
 	/* Never allow zero rtt or baseRTT */
-	vrtt = rtt_us + 1;
+	vrtt = sample->rtt_us + 1;
 
 	/* Filter to find propagation delay: */
 	if (vrtt < vegas->baseRTT)

net/ipv4/tcp_vegas.h

@@ -17,7 +17,7 @@ struct vegas {
 
 void tcp_vegas_init(struct sock *sk);
 void tcp_vegas_state(struct sock *sk, u8 ca_state);
-void tcp_vegas_pkts_acked(struct sock *sk, u32 cnt, s32 rtt_us);
+void tcp_vegas_pkts_acked(struct sock *sk, const struct ack_sample *sample);
 void tcp_vegas_cwnd_event(struct sock *sk, enum tcp_ca_event event);
 size_t tcp_vegas_get_info(struct sock *sk, u32 ext, int *attr,
 			  union tcp_cc_info *info);

net/ipv4/tcp_veno.c

@@ -69,16 +69,17 @@ static void tcp_veno_init(struct sock *sk)
 }
 
 /* Do rtt sampling needed for Veno. */
-static void tcp_veno_pkts_acked(struct sock *sk, u32 cnt, s32 rtt_us)
+static void tcp_veno_pkts_acked(struct sock *sk,
+				const struct ack_sample *sample)
 {
 	struct veno *veno = inet_csk_ca(sk);
 	u32 vrtt;
 
-	if (rtt_us < 0)
+	if (sample->rtt_us < 0)
 		return;
 
 	/* Never allow zero rtt or baseRTT */
-	vrtt = rtt_us + 1;
+	vrtt = sample->rtt_us + 1;
 
 	/* Filter to find propagation delay: */
 	if (vrtt < veno->basertt)

net/ipv4/tcp_westwood.c

@@ -99,12 +99,13 @@ static 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 sock *sk, u32 cnt, s32 rtt)
+static void tcp_westwood_pkts_acked(struct sock *sk,
+				    const struct ack_sample *sample)
 {
 	struct westwood *w = inet_csk_ca(sk);
 
-	if (rtt > 0)
-		w->rtt = usecs_to_jiffies(rtt);
+	if (sample->rtt_us > 0)
+		w->rtt = usecs_to_jiffies(sample->rtt_us);
 }
 
 /*

net/ipv4/tcp_yeah.c

@@ -56,15 +56,16 @@ static void tcp_yeah_init(struct sock *sk)
 	tp->snd_cwnd_clamp = min_t(u32, tp->snd_cwnd_clamp, 0xffffffff/128);
 }
 
-static void tcp_yeah_pkts_acked(struct sock *sk, u32 pkts_acked, s32 rtt_us)
+static void tcp_yeah_pkts_acked(struct sock *sk,
+				const struct ack_sample *sample)
 {
 	const struct inet_connection_sock *icsk = inet_csk(sk);
 	struct yeah *yeah = inet_csk_ca(sk);
 
 	if (icsk->icsk_ca_state == TCP_CA_Open)
-		yeah->pkts_acked = pkts_acked;
+		yeah->pkts_acked = sample->pkts_acked;
 
-	tcp_vegas_pkts_acked(sk, pkts_acked, rtt_us);
+	tcp_vegas_pkts_acked(sk, sample);
 }
 
 static void tcp_yeah_cong_avoid(struct sock *sk, u32 ack, u32 acked)