diff mbox series

[v2,net-next,11/15] tcp: accecn: AccECN option ceb/cep heuristic

Message ID 20250318002710.29483-12-chia-yu.chang@nokia-bell-labs.com (mailing list archive)
State New
Headers show
Series AccECN protocol patch series | expand

Commit Message

Chia-Yu Chang (Nokia) March 18, 2025, 12:27 a.m. UTC 
From: Ilpo Järvinen <ij@kernel.org>

The heuristic algorithm from draft-11 Appendix A.2.2 to
mitigate against false ACE field overflows.

Signed-off-by: Ilpo Järvinen <ij@kernel.org>
Signed-off-by: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
---
 include/net/tcp.h    |  1 +
 net/ipv4/tcp_input.c | 18 ++++++++++++++++--
 2 files changed, 17 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/include/net/tcp.h b/include/net/tcp.h
index d531da9f9af8..09220668d2e3 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -244,6 +244,7 @@  static_assert((1 << ATO_BITS) > TCP_DELACK_MAX);
 #define TCP_ACCECN_MAXSIZE		(TCPOLEN_ACCECN_BASE + \
 					 TCPOLEN_ACCECN_PERFIELD * \
 					 TCP_ACCECN_NUMFIELDS)
+#define TCP_ACCECN_SAFETY_SHIFT		1 /* SAFETY_FACTOR in accecn draft */
 
 /* tp->accecn_fail_mode */
 #define TCP_ACCECN_ACE_FAIL_SEND	BIT(0)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index d7498b1c9fb9..f62bbf6f4eb3 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -695,16 +695,19 @@  static u32 __tcp_accecn_process(struct sock *sk, const struct sk_buff *skb,
 				u32 delivered_pkts, u32 delivered_bytes,
 				int flag)
 {
+	u32 old_ceb = tcp_sk(sk)->delivered_ecn_bytes[INET_ECN_CE - 1];
 	const struct tcphdr *th = tcp_hdr(skb);
 	struct tcp_sock *tp = tcp_sk(sk);
-	u32 delta, safe_delta;
+	u32 delta, safe_delta, d_ceb;
+	bool opt_deltas_valid;
 	u32 corrected_ace;
 
 	/* Reordered ACK or uncertain due to lack of data to send and ts */
 	if (!(flag & (FLAG_FORWARD_PROGRESS | FLAG_TS_PROGRESS)))
 		return 0;
 
-	tcp_accecn_process_option(tp, skb, delivered_bytes, flag);
+	opt_deltas_valid = tcp_accecn_process_option(tp, skb,
+						     delivered_bytes, flag);
 
 	if (!(flag & FLAG_SLOWPATH)) {
 		/* AccECN counter might overflow on large ACKs */
@@ -727,6 +730,17 @@  static u32 __tcp_accecn_process(struct sock *sk, const struct sk_buff *skb,
 	safe_delta = delivered_pkts -
 		     ((delivered_pkts - delta) & TCP_ACCECN_CEP_ACE_MASK);
 
+	if (opt_deltas_valid) {
+		d_ceb = tp->delivered_ecn_bytes[INET_ECN_CE - 1] - old_ceb;
+		if (!d_ceb)
+			return delta;
+		if (d_ceb > delta * tp->mss_cache)
+			return safe_delta;
+		if (d_ceb <
+		    safe_delta * tp->mss_cache >> TCP_ACCECN_SAFETY_SHIFT)
+			return delta;
+	}
+
 	return safe_delta;
 }