On Mon, 5 May 2025, Chia-Yu Chang (Nokia) wrote:
-----Original Message----- From: Paolo Abeni pabeni@redhat.com Sent: Tuesday, April 29, 2025 2:10 PM To: Chia-Yu Chang (Nokia) chia-yu.chang@nokia-bell-labs.com; horms@kernel.org; dsahern@kernel.org; kuniyu@amazon.com; bpf@vger.kernel.org; netdev@vger.kernel.org; dave.taht@gmail.com; jhs@mojatatu.com; kuba@kernel.org; stephen@networkplumber.org; xiyou.wangcong@gmail.com; jiri@resnulli.us; davem@davemloft.net; edumazet@google.com; andrew+netdev@lunn.ch; donald.hunter@gmail.com; ast@fiberby.net; liuhangbin@gmail.com; shuah@kernel.org; linux-kselftest@vger.kernel.org; ij@kernel.org; ncardwell@google.com; Koen De Schepper (Nokia) koen.de_schepper@nokia-bell-labs.com; g.white g.white@cablelabs.com; ingemar.s.johansson@ericsson.com; mirja.kuehlewind@ericsson.com; cheshire@apple.com; rs.ietf@gmx.at; Jason_Livingood@comcast.com; vidhi_goel vidhi_goel@apple.com Subject: Re: [PATCH v5 net-next 10/15] tcp: accecn: AccECN option send control
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On 4/22/25 5:35 PM, chia-yu.chang@nokia-bell-labs.com wrote:
From: Ilpo Järvinen ij@kernel.org
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 ij@kernel.org Co-developed-by: Chia-Yu Chang chia-yu.chang@nokia-bell-labs.com Signed-off-by: Chia-Yu Chang chia-yu.chang@nokia-bell-labs.com
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).