-----Original Message----- From: Eric Dumazet edumazet@google.com Sent: Wednesday, June 25, 2025 9:58 AM To: Chia-Yu Chang (Nokia) chia-yu.chang@nokia-bell-labs.com Cc: pabeni@redhat.com; linux-doc@vger.kernel.org; corbet@lwn.net; horms@kernel.org; dsahern@kernel.org; kuniyu@amazon.com; bpf@vger.kernel.org; netdev@vger.kernel.org; jhs@mojatatu.com; kuba@kernel.org; stephen@networkplumber.org; xiyou.wangcong@gmail.com; jiri@resnulli.us; davem@davemloft.net; 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@cablelabs.com; ingemar.s.johansson@ericsson.com; mirja.kuehlewind@ericsson.com; cheshire@apple.com; rs.ietf@gmx.at; Jason_Livingood@comcast.com; vidhi_goel@apple.com; Olivier Tilmans (Nokia) olivier.tilmans@nokia.com Subject: Re: [PATCH v9 net-next 05/15] tcp: accecn: AccECN negotiation
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On Sat, Jun 21, 2025 at 12:37 PM chia-yu.chang@nokia-bell-labs.com wrote:
From: Ilpo Järvinen ij@kernel.org
Accurate ECN negotiation parts based on the specification: https://tools.ietf.org/id/draft-ietf-tcpm-accurate-ecn-28.txt
[...]
diff --git a/include/net/tcp.h b/include/net/tcp.h index 6cf5cea992e3..4d6325fa3f67 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h
[...]
@@ -1051,6 +1123,15 @@ struct tcp_skb_cb {
#define TCP_SKB_CB(__skb) ((struct tcp_skb_cb *)&((__skb)->cb[0]))
+static inline u16 tcp_accecn_reflector_flags(u8 ect) +{
u32 flags = ect + 2;if (ect == 3)flags++;A comment might help, I have no idea of what is going on here.
Hi Eric,
Sure, comments will be added in the next version.
return FIELD_PREP(TCPHDR_ACE, flags);+}
extern const struct inet_connection_sock_af_ops ipv4_specific;
#if IS_ENABLED(CONFIG_IPV6)
[...]
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c index 3a43010d726f..75ec1a599b52 100644 --- a/net/ipv4/sysctl_net_ipv4.c +++ b/net/ipv4/sysctl_net_ipv4.c @@ -47,6 +47,7 @@ static unsigned int udp_child_hash_entries_max = UDP_HTABLE_SIZE_MAX; static int tcp_plb_max_rounds = 31; static int tcp_plb_max_cong_thresh = 256; static unsigned int tcp_tw_reuse_delay_max = TCP_PAWS_MSL * MSEC_PER_SEC; +static int tcp_ecn_mode_max = 5;
/* obsolete */ static int sysctl_tcp_low_latency __read_mostly; @@ -728,7 +729,7 @@ static struct ctl_table ipv4_net_table[] = { .mode = 0644, .proc_handler = proc_dou8vec_minmax, .extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_TWO,
.extra2 = &tcp_ecn_mode_max,Please change Documentation/networking/ip-sysctl.rst tcp_ecn accordingly ?
OK, I will break the patch of Documentation/networking/ip-sysctl.rst in this patch.
}, { .procname = "tcp_ecn_fallback",diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 8e0e8d784b1c..e6d7b5420c88 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -3392,6 +3392,8 @@ int tcp_disconnect(struct sock *sk, int flags) tp->window_clamp = 0; tp->delivered = 0; tp->delivered_ce = 0;
tp->wait_third_ack = 0;tp->accecn_fail_mode = 0; tcp_accecn_init_counters(tp); if (icsk->icsk_ca_initialized && icsk->icsk_ca_ops->release) icsk->icsk_ca_ops->release(sk);diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 0fa3803b353d..c986452302cb 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -411,14 +411,114 @@ static void tcp_data_ecn_check(struct sock *sk, const struct sk_buff *skb) } }
I do think this patch is too big and should be split.
I will remove the following two parts from this patch into other patches: (1) ECN negotiation in simultaneous connect, and (2) CA module flag (TCP_CONG_NEEDS_ACCECN) defines that the CA expects to negotiate AccECN functionality.
Best regards, Chia-Yu