On 10/30/25 3:34 PM, chia-yu.chang@nokia-bell-labs.com wrote:
From: Chia-Yu Chang chia-yu.chang@nokia-bell-labs.com
Detect spurious retransmission of a previously sent ACK carrying the AccECN option after the second retransmission. Since this might be caused by the middlebox dropping ACK with options it does not recognize, disable the sending of the AccECN option in all subsequent ACKs. This patch follows Section 3.2.3.2.2 of AccECN spec (RFC9768).
Also, a new AccECN option sending mode is added to tcp_ecn_option sysctl: (TCP_ECN_OPTION_PERSIST), which ignores the AccECN fallback policy and persistently sends AccECN option once it fits into TCP option space.
Signed-off-by: Chia-Yu Chang chia-yu.chang@nokia-bell-labs.com
Acked-by: Paolo Abeni pabeni@redhat.com