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> On 7/4/25 10:53 AM, chia-yu.ch...@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.
Hi Paolo,
I was thinking to change it into GENMASK_U32() and comments like below.
It is intended to send AccECN option at least once per 2^22-byte increase in
the counter.
But this is done by checking the bit edges (from bit 22) of the byte counters
to avoid extra variables.
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 if any ECN byte counter is
* increased by at least 2^22 bytes.
*/
if ((tp->received_ecn_bytes[ecnfield - 1] ^ oldbytes) &
bytes_mask) {
tcp_accecn_opt_demand_min(sk, 1);
}
Would it make more sense to you?
