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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID:
 <PAXPR07MB7984D6FA40FF000E51F694F3A357A@PAXPR07MB7984.eurprd07.prod.outlook.com>
Date: Tue, 15 Jul 2025 15:14:11 +0000
From: "Chia-Yu Chang (Nokia)" <chia-yu.chang@...ia-bell-labs.com>
To: Paolo Abeni <pabeni@...hat.com>, "edumazet@...gle.com"
	<edumazet@...gle.com>, "linux-doc@...r.kernel.org"
	<linux-doc@...r.kernel.org>, "corbet@....net" <corbet@....net>,
	"horms@...nel.org" <horms@...nel.org>, "dsahern@...nel.org"
	<dsahern@...nel.org>, "kuniyu@...zon.com" <kuniyu@...zon.com>,
	"bpf@...r.kernel.org" <bpf@...r.kernel.org>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>, "dave.taht@...il.com" <dave.taht@...il.com>,
	"jhs@...atatu.com" <jhs@...atatu.com>, "kuba@...nel.org" <kuba@...nel.org>,
	"stephen@...workplumber.org" <stephen@...workplumber.org>,
	"xiyou.wangcong@...il.com" <xiyou.wangcong@...il.com>, "jiri@...nulli.us"
	<jiri@...nulli.us>, "davem@...emloft.net" <davem@...emloft.net>,
	"andrew+netdev@...n.ch" <andrew+netdev@...n.ch>, "donald.hunter@...il.com"
	<donald.hunter@...il.com>, "ast@...erby.net" <ast@...erby.net>,
	"liuhangbin@...il.com" <liuhangbin@...il.com>, "shuah@...nel.org"
	<shuah@...nel.org>, "linux-kselftest@...r.kernel.org"
	<linux-kselftest@...r.kernel.org>, "ij@...nel.org" <ij@...nel.org>,
	"ncardwell@...gle.com" <ncardwell@...gle.com>, "Koen De Schepper (Nokia)"
	<koen.de_schepper@...ia-bell-labs.com>, "g.white@...lelabs.com"
	<g.white@...lelabs.com>, "ingemar.s.johansson@...csson.com"
	<ingemar.s.johansson@...csson.com>, "mirja.kuehlewind@...csson.com"
	<mirja.kuehlewind@...csson.com>, "cheshire@...le.com" <cheshire@...le.com>,
	"rs.ietf@....at" <rs.ietf@....at>, "Jason_Livingood@...cast.com"
	<Jason_Livingood@...cast.com>, "vidhi_goel@...le.com" <vidhi_goel@...le.com>
Subject: RE: [PATCH v12 net-next 12/15] tcp: accecn: AccECN option send
 control

> CAUTION: This is an external email. Please be very careful when clicking links or opening attachments. See the URL nok.it/ext for additional information.
> 
> 
> 
> On 7/4/25 10:53 AM, chia-yu.chang@...ia-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?