-----Original Message-----
From: Paolo Abeni <pabeni@redhat.com> 
Sent: Thursday, November 6, 2025 1:18 PM
To: Chia-Yu Chang (Nokia) <redacted>; edumazet@google.com; parav@nvidia.com; linux-doc@vger.kernel.org; corbet@lwn.net; horms@kernel.org; dsahern@kernel.org; kuniyu@google.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; 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) <redacted>; g.white@cablelabs.com; ingemar.s.johansson@ericsson.com; mirja.kuehlewind@ericsson.com; cheshire <redacted>; rs.ietf@gmx.at; Jason_Livingood@comcast.com; Vidhi Goel <redacted>
Subject: Re: [PATCH v5 net-next 11/14] tcp: accecn: unset ECT if receive or send ACE=0 in AccECN negotiaion


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On 10/30/25 3:34 PM, chia-yu.chang@nokia-bell-labs.com wrote:

quoted

@@ -4006,7 +4008,7 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
      memset(th, 0, sizeof(struct tcphdr));
      th->syn = 1;
      th->ack = 1;
-     tcp_ecn_make_synack(req, th);
+     tcp_ecn_make_synack((struct sock *)sk, req, th);
      th->source = htons(ireq->ir_num);
      th->dest = ireq->ir_rmt_port;
      skb->mark = ireq->ir_mark;

Whoops, I missed the const cast in the previous revisions. This could make the code generated by the compiler for the caller incorrect - assuming the changed field is actually constant.

I don't have a good idea on how to address this. Changing the argument type for the whole call chain looks like a no go.

/P

One thought I have now is to add one extra flag in request_sock.

By using this new flag in rquest_sock after calling tcp_rtx_synack, the ACCECN_FAIL_MODE can be set in sk.

Would it make sense to you?

Chia-Yu