Re: [PATCH v5 net-next 03/14] net: update commnets for SKB_GSO_TCP_ECN and SKB_GSO_TCP_ACCECN

[Paolo Abeni <pabeni@redhat.com>]

On 11/6/25 12:06 PM, Paolo Abeni wrote:
> 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>
>>
>> No functional changes.
>>
>> Co-developed-by: Ilpo Järvinen <ij@kernel.org>
>> Signed-off-by: Ilpo Järvinen <ij@kernel.org>
>> Signed-off-by: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
>> ---
>>  include/linux/skbuff.h | 13 ++++++++++++-
>>  1 file changed, 12 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
>> index a7cc3d1f4fd1..74d6a209e203 100644
>> --- a/include/linux/skbuff.h
>> +++ b/include/linux/skbuff.h
>> @@ -671,7 +671,12 @@ 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. This cannot be
>> +	 * used on Rx, because the connection to which the segment belongs is
>> +	 * not tracked to use RFC3168 or Accurate ECN, and using RFC3168 ECN
>> +	 * offload may corrupt AccECN signal of AccECN segments.
>> +	 */
> 
> The intended difference between RX and TX sounds bad to me; I think it
> conflicts with the basic GRO design goal of making aggregated and
> re-segmented traffic indistinguishable from the original stream. Also
> what about forwarded packet?

Uhm... I missed completely the point that SKB_GSO_TCP_ECN is TX path
only, i.e. GRO never produces aggregated SKB_GSO_TCP_ECN packets. Except
virtio_net uses it in the RX path ( virtio_net_hdr_to_skb ). Please
clarify the statement accordingly.

/P