Re: [PATCH net-next v2 3/4] net: core: resegment oversized TCP GSO skbs

[Paolo Abeni <pabeni@redhat.com>]

On 9/19/26 17:37, Willem de Bruijn wrote:
>> @@ -4088,10 +4168,29 @@ static struct sk_buff *validate_xmit_skb(struct sk_buff *skb, struct net_device
>>   	if (unlikely(!skb))
>>   		goto out_null;
>>   
>> -	if (netif_needs_gso(skb, features)) {
>> +	/*
>> +	 * An oversized skb loses its GSO feature bits and is segmented
>> +	 * down to MSS sized skbs below.  A TCP skb can instead be split
>> +	 * into GSO skbs which do fit the device, so keep the bits and
>> +	 * bound the resegmentation.  The features computed without the
>> +	 * limit checks say whether the device offloads the GSO type at
>> +	 * all.
>> +	 */
>> +	if (skb_is_gso(skb) && skb_is_gso_tcp(skb) && !skb->encapsulation &&
>> +	    !gso_within_device_limits(skb, dev)) {
>> +		netdev_features_t offload = __netif_skb_features(skb, false);
>> +
>> +		resegment_max_segs =
>> +			skb_gso_resegment_max_segs(skb, dev, offload);
>> +		if (resegment_max_segs)
>> +			features = offload;
>> +	}
>> +
> 
> This is a lot to put in the hot path for a rare use case. 

+1

> Consider how to make this less expensive.
I think that performing all the resegs check only in the

	netif_needs_gso(skb, features)

case would address this concern.

/P