Re: [PATCH v12 net-next 12/15] tcp: accecn: AccECN option send control

On 7/4/25 10:53 AM, chia-yu.chang@nokia-bell-labs.com wrote:

@@ -285,9 +297,33 @@ 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];
  

• tp->received_ecn_bytes[ecnfield - 1] += len;
  tp->accecn_minlen = max_t(u8, tp->accecn_minlen,
  			  minlen);
  

• 	/* Demand AccECN option at least every 2^22 bytes to
  

• 	 * avoid overflowing the ECN byte counters.
  

• 	 */
  

• 	if ((tp->received_ecn_bytes[ecnfield - 1] ^ oldbytes) &
  

• 	    ~((1 << 22) - 1)) {
  

I don't understand the above statement, I don't think it yield the result expected according to the above comment.

@@ -365,6 +401,7 @@ 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;

} @@ -447,6 +484,7 @@ 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)) {

@@ -467,6 +505,7 @@ 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);
  

  } }

@@ -565,4 +604,16 @@ 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) +{

• const struct tcp_sock *tp = tcp_sk(sk);
• if (!READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_option_beacon))

• return false;
  

• return tcp_stamp_us_delta(tp->tcp_mstamp, tp->accecn_opt_tstamp) *

•       READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_option_beacon) >=
  

•       (tp->srtt_us >> 3);
  

To be consistent:

u32 ecn_beacon = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_option_beacon);

if (!ecn_beacon) return false;

return tcp_stamp_us_delta(tp->tcp_mstamp, tp->accecn_opt_tstamp) * ecn_beacon // ...

/P