netdev - Re: [PATCH v8 net-next 11/15] tcp: accecn: AccECN option failure handling

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Message-ID: <558d81d1-3cd0-41f8-87b1-aa7be05f2924@redhat.com>
Date: Tue, 17 Jun 2025 11:44:21 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: chia-yu.chang@...ia-bell-labs.com, edumazet@...gle.com,
 linux-doc@...r.kernel.org, corbet@....net, horms@...nel.org,
 dsahern@...nel.org, kuniyu@...zon.com, bpf@...r.kernel.org,
 netdev@...r.kernel.org, dave.taht@...il.com, jhs@...atatu.com,
 kuba@...nel.org, stephen@...workplumber.org, xiyou.wangcong@...il.com,
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 donald.hunter@...il.com, ast@...erby.net, liuhangbin@...il.com,
 shuah@...nel.org, linux-kselftest@...r.kernel.org, ij@...nel.org,
 ncardwell@...gle.com, koen.de_schepper@...ia-bell-labs.com,
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 mirja.kuehlewind@...csson.com, cheshire@...le.com, rs.ietf@....at,
 Jason_Livingood@...cast.com, vidhi_goel@...le.com
Subject: Re: [PATCH v8 net-next 11/15] tcp: accecn: AccECN option failure
 handling

On 6/10/25 2:53 PM, chia-yu.chang@...ia-bell-labs.com wrote:
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index 3de6641c776e..d7cdc6589a9c 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -1087,6 +1087,7 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
>  	/* Simultaneous open SYN/ACK needs AccECN option but not SYN */
>  	if (unlikely((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK) &&
>  		     tcp_ecn_mode_accecn(tp) &&
> +		     inet_csk(sk)->icsk_retransmits < 2 &&
>  		     sock_net(sk)->ipv4.sysctl_tcp_ecn_option &&
>  		     remaining >= TCPOLEN_ACCECN_BASE)) {
>  		u32 saving = tcp_synack_options_combine_saving(opts);

AFAICS here the AccECN option is allowed even on the first retransmit as
opposed of what enforced for synack packets and what stated in the
commit message. Why?

Either code change or code/commit message comment needed.

Thanks,

Paolo