On Sat, Jan 31, 2026 at 11:55:08PM +0100, [email protected]
wrote:
> From: Chia-Yu Chang <[email protected]>
>
> No functional changes.
>
> Co-developed-by: Ilpo Järvinen <[email protected]>
> Signed-off-by: Ilpo Järvinen <[email protected]>
> Signed-off-by: Chia-Yu Chang <[email protected]>
Subject: comments?
> ---
> include/linux/skbuff.h | 16 +++++++++++++++-
> 1 file changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index e6bfe5d0c525..30a8dc4233ba 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -671,7 +671,13 @@ enum {
> /* This indicates the skb is from an untrusted source. */
> SKB_GSO_DODGY = 1 << 1,
>
> - /* This indicates the tcp segment has CWR set. */
> + /* For Tx, this indicates the first TCP segment has CWR set, and any
> + * subsequent segment in the same skb has CWR cleared. However, because
> + * the connection to which the segment belongs is not tracked to use
> + * RFC3168 or AccECN (RFC9768), and using RFC3168 ECN offload may clear
> + * ACE signal (CWR is one of it). Therefore, this cannot be used on Rx.
> + * Instead, SKB_GSO_TCP_ACCECN shall be used to avoid CWR corruption.
> + */
> SKB_GSO_TCP_ECN = 1 << 2,
>
> __SKB_GSO_TCP_FIXEDID = 1 << 3,
> @@ -706,6 +712,14 @@ enum {
>
> SKB_GSO_FRAGLIST = 1 << 18,
>
> + /* For TX, this indicates the TCP segment uses the CWR flag as part of
> + * ACE signal, and the CWR flag is not modified in the skb. For RX, any
> + * CWR flagged segment must use SKB_GSO_TCP_ACCECN to ensure CWR flag
> + * is not cleared by any RFC3168 ECN offload, and thus keeping ACE
> + * signal of AccECN segments. This is particularly used for Rx of
> + * virtio_net driver in order to tell latter GSO Tx in a forwarding
> + * scenario that it is NOT ok to clean CWR flag from the 2nd segment.
> + */
> SKB_GSO_TCP_ACCECN = 1 << 19,
>
> /* These indirectly map onto the same netdev feature.
> --
> 2.34.1
