1 files changed, 52 insertions, 0 deletions

diff --git a/include/net/tcp_ecn.h b/include/net/tcp_ecn.h
index 08c7f4757e4e..133fb6b79500 100644
--- a/include/net/tcp_ecn.h
+++ b/include/net/tcp_ecn.h
@@ -176,6 +176,17 @@ static inline void tcp_accecn_third_ack(struct sock *sk,
 	}
 }
 
+/* Demand the minimum # to send AccECN optnio */
+static inline void tcp_accecn_opt_demand_min(struct sock *sk,
+					     u8 opt_demand_min)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	u8 opt_demand;
+
+	opt_demand = max_t(u8, opt_demand_min, tp->accecn_opt_demand);
+	tp->accecn_opt_demand = opt_demand;
+}
+
 /* Maps IP ECN field ECT/CE code point to AccECN option field number, given
  * we are sending fields with Accurate ECN Order 1: ECT(1), CE, ECT(0).
  */
@@ -256,6 +267,7 @@ static inline void tcp_ecn_received_counters(struct sock *sk,
 	u8 ecnfield = TCP_SKB_CB(skb)->ip_dsfield & INET_ECN_MASK;
 	u8 is_ce = INET_ECN_is_ce(ecnfield);
 	struct tcp_sock *tp = tcp_sk(sk);
+	bool ecn_edge;
 
 	if (!INET_ECN_is_not_ect(ecnfield)) {
 		u32 pcount = is_ce * max_t(u16, 1, skb_shinfo(skb)->gso_segs);
@@ -274,9 +286,34 @@ static inline void tcp_ecn_received_counters(struct sock *sk,
 
 		if (len > 0) {
 			u8 minlen = tcp_ecnfield_to_accecn_optfield(ecnfield);
+			u32 oldbytes = tp->received_ecn_bytes[ecnfield - 1];
+			u32 bytes_mask = GENMASK_U32(31, 22);
+
 			tp->received_ecn_bytes[ecnfield - 1] += len;
 			tp->accecn_minlen = max_t(u8, tp->accecn_minlen,
 						  minlen);
+
+			/* Send AccECN option at least once per 2^22-byte
+			 * increase in any ECN byte counter.
+			 */
+			if ((tp->received_ecn_bytes[ecnfield - 1] ^ oldbytes) &
+			    bytes_mask) {
+				tcp_accecn_opt_demand_min(sk, 1);
+			}
+		}
+	}
+
+	ecn_edge = tp->prev_ecnfield != ecnfield;
+	if (ecn_edge || is_ce) {
+		tp->prev_ecnfield = ecnfield;
+		/* Demand Accurate ECN change-triggered ACKs. Two ACK are
+		 * demanded to indicate unambiguously the ecnfield value
+		 * in the latter ACK.
+		 */
+		if (tcp_ecn_mode_accecn(tp)) {
+			if (ecn_edge)
+				inet_csk(sk)->icsk_ack.pending |= ICSK_ACK_NOW;
+			tp->accecn_opt_demand = 2;
 		}
 	}
 }
@@ -349,6 +386,7 @@ static inline void tcp_accecn_init_counters(struct tcp_sock *tp)
 	__tcp_accecn_init_bytes_counters(tp->received_ecn_bytes);
 	__tcp_accecn_init_bytes_counters(tp->delivered_ecn_bytes);
 	tp->accecn_minlen = 0;
+	tp->accecn_opt_demand = 0;
 	tp->est_ecnfield = 0;
 }
 
@@ -431,6 +469,7 @@ static inline void tcp_ecn_rcv_synack(struct sock *sk, const struct tcphdr *th,
 	default:
 		tcp_ecn_mode_set(tp, TCP_ECN_MODE_ACCECN);
 		tp->syn_ect_rcv = ip_dsfield & INET_ECN_MASK;
+		tp->accecn_opt_demand = 2;
 		if (INET_ECN_is_ce(ip_dsfield) &&
 		    tcp_accecn_validate_syn_feedback(sk, ace,
 						     tp->syn_ect_snt)) {
@@ -451,6 +490,7 @@ static inline void tcp_ecn_rcv_syn(struct tcp_sock *tp, const struct tcphdr *th,
 		} else {
 			tp->syn_ect_rcv = TCP_SKB_CB(skb)->ip_dsfield &
 					  INET_ECN_MASK;
+			tp->prev_ecnfield = tp->syn_ect_rcv;
 			tcp_ecn_mode_set(tp, TCP_ECN_MODE_ACCECN);
 		}
 	}
@@ -542,4 +582,16 @@ tcp_ecn_make_synack(const struct request_sock *req, struct tcphdr *th)
 		th->ece = 1;
 }
 
+static inline bool tcp_accecn_option_beacon_check(const struct sock *sk)
+{
+	u32 ecn_beacon = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_option_beacon);
+	const struct tcp_sock *tp = tcp_sk(sk);
+
+	if (!ecn_beacon)
+		return false;
+
+	return tcp_stamp_us_delta(tp->tcp_mstamp, tp->accecn_opt_tstamp) * ecn_beacon >=
+	       (tp->srtt_us >> 3);
+}
+
 #endif /* _LINUX_TCP_ECN_H */