-----Original Message----- From: Eric Dumazet edumazet@google.com Sent: Thursday, August 21, 2025 2:56 PM 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 Subject: Re: [PATCH v15 net-next 12/14] tcp: accecn: AccECN option failure handling
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On Fri, Aug 15, 2025 at 1:40 AM chia-yu.chang@nokia-bell-labs.com wrote:
From: Chia-Yu Chang chia-yu.chang@nokia-bell-labs.com
AccECN option may fail in various way, handle these:
- Attempt to negotiate the use of AccECN on the 1st retransmitted SYN - From the 2nd retransmitted SYN, stop AccECN negotiation
- Remove option from SYN/ACK rexmits to handle blackholes
- If no option arrives in SYN/ACK, assume Option is not usable - If an option arrives later, re-enabled
- If option is zeroed, disable AccECN option processing
This patch use existing padding bits in tcp_request_sock and holes in tcp_sock without increasing the size.
Signed-off-by: Ilpo Järvinen ij@kernel.org Signed-off-by: Chia-Yu Chang chia-yu.chang@nokia-bell-labs.com
Truly invasive changes, what can I say....
Not sure why you CC so many folks which will very unlikely give any feedback.
What is the purpose of WARN_ON_ONCE() in tcp_accecn_option_init() ?
Just to feed syzbot ?
Hi Eric,
WARN_ON_ONCE() exists in both tcp_accecn_option_init() and tcp_accecn_process_option().
And the one in tcp_accecn_option_init() is for AccECN option handling during the handshake.
Or is it not preferred to put WARN_ON_ONCE() during TCP handshake?
Chia-Yu