diff mbox series

[v9,net-next,13/15] tcp: accecn: AccECN ACE field multi-wrap heuristic

Message ID 20250621193737.16593-14-chia-yu.chang@nokia-bell-labs.com
State New
Headers show
Series AccECN protocol patch series | expand

Commit Message

Chia-Yu Chang (Nokia) June 21, 2025, 7:37 p.m. UTC 
From: Ilpo Järvinen <ij@kernel.org>

Armed with ceb delta from option, delivered bytes, and
delivered packets it is possible to estimate how many times
ACE field wrapped.

This calculation is necessary only if more than one wrap
is possible. Without SACK, delivered bytes and packets are
not always trustworthy in which case TCP falls back to the
simpler no-or-all wraps ceb algorithm.

Signed-off-by: Ilpo Järvinen <ij@kernel.org>
Signed-off-by: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
---
 net/ipv4/tcp_input.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)
diff mbox series

Patch

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 3f8cac22efda..97b5fe52d8fd 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -758,6 +758,24 @@  static u32 __tcp_accecn_process(struct sock *sk, const struct sk_buff *skb,
 		d_ceb = tp->delivered_ecn_bytes[INET_ECN_CE - 1] - old_ceb;
 		if (!d_ceb)
 			return delta;
+
+		if ((delivered_pkts >= (TCP_ACCECN_CEP_ACE_MASK + 1) * 2) &&
+		    (tcp_is_sack(tp) ||
+		     ((1 << inet_csk(sk)->icsk_ca_state) &
+		      (TCPF_CA_Open | TCPF_CA_CWR)))) {
+			u32 est_d_cep;
+
+			if (delivered_bytes <= d_ceb)
+				return safe_delta;
+
+			est_d_cep = DIV_ROUND_UP_ULL((u64)d_ceb *
+						     delivered_pkts,
+						     delivered_bytes);
+			return min(safe_delta,
+				   delta +
+				   (est_d_cep & ~TCP_ACCECN_CEP_ACE_MASK));
+		}
+
 		if (d_ceb > delta * tp->mss_cache)
 			return safe_delta;
 		if (d_ceb <