netdev - [RFC PATCH 17/28] tcp: AccECN needs to know delivered bytes

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Date:   Wed, 18 Mar 2020 11:43:21 +0200
From:   Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>
To:     netdev@...r.kernel.org
Cc:     Yuchung Cheng <ycheng@...gle.com>,
        Neal Cardwell <ncardwell@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Olivier Tilmans <olivier.tilmans@...ia-bell-labs.com>
Subject: [RFC PATCH 17/28] tcp: AccECN needs to know delivered bytes

From: Ilpo Järvinen <ilpo.jarvinen@...helsinki.fi>

AccECN byte counter estimation requires delivered bytes
which can be calculated while processing SACK blocks and
cumulative ACK.

Non-SACK calculation is quite annoying, inaccurate, and
likely bogus.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...helsinki.fi>
---
 net/ipv4/tcp_input.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 3109e3199906..0a63f8a49057 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1235,6 +1235,7 @@ static bool tcp_check_dsack(struct sock *sk, const struct sk_buff *ack_skb,
 
 struct tcp_sacktag_state {
 	u32	reord;
+	u32	delivered_bytes;
 	/* Timestamps for earliest and latest never-retransmitted segment
 	 * that was SACKed. RTO needs the earliest RTT to stay conservative,
 	 * but congestion control should still get an accurate delay signal.
@@ -1306,7 +1307,7 @@ static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb,
 static u8 tcp_sacktag_one(struct sock *sk,
 			  struct tcp_sacktag_state *state, u8 sacked,
 			  u32 start_seq, u32 end_seq,
-			  int dup_sack, int pcount,
+			  int dup_sack, int pcount, u32 plen,
 			  u64 xmit_time)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
@@ -1365,6 +1366,7 @@ static u8 tcp_sacktag_one(struct sock *sk,
 		state->flag |= FLAG_DATA_SACKED;
 		tp->sacked_out += pcount;
 		tp->delivered += pcount;  /* Out-of-order packets delivered */
+		state->delivered_bytes += plen;
 
 		/* Lost marker hint past SACKed? Tweak RFC3517 cnt */
 		if (tp->lost_skb_hint &&
@@ -1406,7 +1408,7 @@ static bool tcp_shifted_skb(struct sock *sk, struct sk_buff *prev,
 	 * tcp_highest_sack_seq() when skb is highest_sack.
 	 */
 	tcp_sacktag_one(sk, state, TCP_SKB_CB(skb)->sacked,
-			start_seq, end_seq, dup_sack, pcount,
+			start_seq, end_seq, dup_sack, pcount, skb->len,
 			tcp_skb_timestamp_us(skb));
 	tcp_rate_skb_delivered(sk, skb, state->rate);
 
@@ -1696,6 +1698,7 @@ static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk,
 						TCP_SKB_CB(skb)->end_seq,
 						dup_sack,
 						tcp_skb_pcount(skb),
+						skb->len,
 						tcp_skb_timestamp_us(skb));
 			tcp_rate_skb_delivered(sk, skb, state->rate);
 			if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
@@ -3239,6 +3242,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, u32 prior_fack,
 			tp->sacked_out -= acked_pcount;
 		} else if (tcp_is_sack(tp)) {
 			tp->delivered += acked_pcount;
+			sack->delivered_bytes += skb->len;
 			if (!tcp_skb_spurious_retrans(tp, skb))
 				tcp_rack_advance(tp, sacked, scb->end_seq,
 						 tcp_skb_timestamp_us(skb));
@@ -3325,6 +3329,10 @@ static int tcp_clean_rtx_queue(struct sock *sk, u32 prior_fack,
 			 */
 			if (flag & FLAG_RETRANS_DATA_ACKED)
 				flag &= ~FLAG_ORIG_SACK_ACKED;
+
+			sack->delivered_bytes = (skb ?
+						 TCP_SKB_CB(skb)->seq :
+						 tp->snd_una) - prior_snd_una;
 		} else {
 			int delta;
 
@@ -3742,6 +3750,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 	u32 ecn_count = 0; /* Did we receive ECE/an AccECN ACE update? */
 	u32 prior_fack;
 
+	sack_state.delivered_bytes = 0;
 	sack_state.first_sackt = 0;
 	sack_state.rate = &rs;
 
-- 
2.20.1