On Mon, 5 May 2025, Chia-Yu Chang (Nokia) wrote:
> > -----Original Message-----
> > From: Paolo Abeni <[email protected]>
> > Sent: Tuesday, April 29, 2025 2:10 PM
> > To: Chia-Yu Chang (Nokia) <[email protected]>;
> > [email protected]; [email protected]; [email protected];
> > [email protected]; [email protected]; [email protected];
> > [email protected]; [email protected]; [email protected];
> > [email protected]; [email protected]; [email protected];
> > [email protected]; [email protected]; [email protected];
> > [email protected]; [email protected]; [email protected];
> > [email protected]; [email protected]; [email protected];
> > Koen De Schepper (Nokia) <[email protected]>; g.white
> > <[email protected]>; [email protected];
> > [email protected]; [email protected]; [email protected];
> > [email protected]; vidhi_goel <[email protected]>
> > Subject: Re: [PATCH v5 net-next 10/15] 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 4/22/25 5:35 PM, [email protected] wrote:
> > > From: Ilpo Järvinen <[email protected]>
> > >
> > > Instead of sending the option in every ACK, limit sending to those
> > > ACKs where the option is necessary:
> > > - Handshake
> > > - "Change-triggered ACK" + the ACK following it. The
> > > 2nd ACK is necessary to unambiguously indicate which
> > > of the ECN byte counters in increasing. The first
> > > ACK has two counters increasing due to the ecnfield
> > > edge.
> > > - ACKs with CE to allow CEP delta validations to take
> > > advantage of the option.
> > > - Force option to be sent every at least once per 2^22
> > > bytes. The check is done using the bit edges of the
> > > byte counters (avoids need for extra variables).
> > > - AccECN option beacon to send a few times per RTT even if
> > > nothing in the ECN state requires that. The default is 3
> > > times per RTT, and its period can be set via
> > > sysctl_tcp_ecn_option_beacon.
> > >
> > > Signed-off-by: Ilpo Järvinen <[email protected]>
> > > Co-developed-by: Chia-Yu Chang <[email protected]>
> > > Signed-off-by: Chia-Yu Chang <[email protected]>
> > > ---
> > > include/linux/tcp.h | 3 +++
> > > include/net/netns/ipv4.h | 1 +
> > > include/net/tcp.h | 1 +
> > > net/ipv4/sysctl_net_ipv4.c | 9 ++++++++
> > > net/ipv4/tcp.c | 5 ++++-
> > > net/ipv4/tcp_input.c | 36 +++++++++++++++++++++++++++++++-
> > > net/ipv4/tcp_ipv4.c | 1 +
> > > net/ipv4/tcp_minisocks.c | 2 ++
> > > net/ipv4/tcp_output.c | 42 ++++++++++++++++++++++++++++++--------
> > > 9 files changed, 90 insertions(+), 10 deletions(-)
> > > diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index
> > > 3f3e285fc973..2e95dad66fe3 100644
> > > --- a/net/ipv4/tcp_ipv4.c
> > > +++ b/net/ipv4/tcp_ipv4.c
> > > @@ -3451,6 +3451,7 @@ static int __net_init tcp_sk_init(struct net
> > > *net) {
> > > net->ipv4.sysctl_tcp_ecn = 2;
> > > net->ipv4.sysctl_tcp_ecn_option = 2;
> > > + net->ipv4.sysctl_tcp_ecn_option_beacon = 3;
> > > net->ipv4.sysctl_tcp_ecn_fallback = 1;
> >
> > Human readable macros instead of magic numbers could help.
>
> OK, commments will be added here.
Hi,
Using named defines to replace literals would be more useful than comments
(names can be grepped for, do not fall out-of-sync with code, etc.).
> > > @@ -1237,13 +1253,18 @@ static unsigned int
> > > tcp_established_options(struct sock *sk, struct sk_buff *skb
> > >
> > > if (tcp_ecn_mode_accecn(tp) &&
> > > sock_net(sk)->ipv4.sysctl_tcp_ecn_option) {
> > > - int saving = opts->num_sack_blocks > 0 ? 2 : 0;
> > > - int remaining = MAX_TCP_OPTION_SPACE - size;
> > > -
> > > - opts->ecn_bytes = tp->received_ecn_bytes;
> > > - size += tcp_options_fit_accecn(opts, tp->accecn_minlen,
> > > - remaining,
> > > - saving);
> > > + if (sock_net(sk)->ipv4.sysctl_tcp_ecn_option >= 2 ||
> > > + tp->accecn_opt_demand ||
> > > + tcp_accecn_option_beacon_check(sk)) {
> >
> > Why a nested if here and just not expanding the existing one?
>
> Sure, will merge them.
While I don't remember everything that well anymore, this might have been
to reduce code churn in some later patch, so it might be worth to check
it first (that patch might even fall outside of this series now that these
are split into multiple chunks).
--
i.
