netdev - [PATCH net-next 20/44] tcp: accecn: AccECN needs to know delivered bytes

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Message-Id: <20241015102940.26157-21-chia-yu.chang@nokia-bell-labs.com>
Date: Tue, 15 Oct 2024 12:29:16 +0200
From: chia-yu.chang@...ia-bell-labs.com
To: netdev@...r.kernel.org, ij@...nel.org, ncardwell@...gle.com,
        koen.de_schepper@...ia-bell-labs.com, g.white@...leLabs.com,
        ingemar.s.johansson@...csson.com, mirja.kuehlewind@...csson.com,
        cheshire@...le.com, rs.ietf@....at, Jason_Livingood@...cast.com,
        vidhi_goel@...le.com
Cc: Chia-Yu Chang <chia-yu.chang@...ia-bell-labs.com>
Subject: [PATCH net-next 20/44] tcp: accecn: AccECN needs to know delivered bytes

From: Ilpo Järvinen <ij@...nel.org>

AccECN byte counter estimation requires delivered bytes
which can be calculated while processing SACK blocks and
cumulative ACK. The delivered bytes will be used to estimate
the byte counters between AccECN option (on ACKs w/o the
option).

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

Signed-off-by: Ilpo Järvinen <ij@...nel.org>
Signed-off-by: Chia-Yu Chang <chia-yu.chang@...ia-bell-labs.com>
---
 net/ipv4/tcp_input.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index c6b1324caab4..f70b65034e45 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1159,6 +1159,7 @@ struct tcp_sacktag_state {
 	u64	last_sackt;
 	u32	reord;
 	u32	sack_delivered;
+	u32     delivered_bytes;
 	int	flag;
 	unsigned int mss_now;
 	struct rate_sample *rate;
@@ -1520,7 +1521,7 @@ 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);
@@ -1580,6 +1581,7 @@ static u8 tcp_sacktag_one(struct sock *sk,
 		tp->sacked_out += pcount;
 		/* Out-of-order packets delivered */
 		state->sack_delivered += pcount;
+		state->delivered_bytes += plen;
 
 		/* Lost marker hint past SACKed? Tweak RFC3517 cnt */
 		if (tp->lost_skb_hint &&
@@ -1621,7 +1623,7 @@ 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);
 
@@ -1913,6 +1915,7 @@ 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)
@@ -3529,6 +3532,8 @@ static int tcp_clean_rtx_queue(struct sock *sk, const struct sk_buff *ack_skb,
 
 		if (sacked & TCPCB_SACKED_ACKED) {
 			tp->sacked_out -= acked_pcount;
+			/* snd_una delta covers these skbs */
+			sack->delivered_bytes -= skb->len;
 		} else if (tcp_is_sack(tp)) {
 			tcp_count_delivered(tp, acked_pcount, ece_ack);
 			if (!tcp_skb_spurious_retrans(tp, skb))
@@ -3632,6 +3637,10 @@ static int tcp_clean_rtx_queue(struct sock *sk, const struct sk_buff *ack_skb,
 			delta = prior_sacked - tp->sacked_out;
 			tp->lost_cnt_hint -= min(tp->lost_cnt_hint, delta);
 		}
+
+		sack->delivered_bytes = (skb ?
+					 TCP_SKB_CB(skb)->seq : tp->snd_una) -
+					 prior_snd_una;
 	} else if (skb && rtt_update && sack_rtt_us >= 0 &&
 		   sack_rtt_us > tcp_stamp_us_delta(tp->tcp_mstamp,
 						    tcp_skb_timestamp_us(skb))) {
@@ -4085,6 +4094,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 	sack_state.first_sackt = 0;
 	sack_state.rate = &rs;
 	sack_state.sack_delivered = 0;
+	sack_state.delivered_bytes = 0;
 
 	/* We very likely will need to access rtx queue. */
 	prefetch(sk->tcp_rtx_queue.rb_node);
-- 
2.34.1