On Wed, Sep 18, 2019 at 08:04:18PM -0600, Subash Abhinov Kasiviswanathan wrote:

On 2019-09-18 10:10, Willem de Bruijn wrote:

quoted

On Wed, Sep 18, 2019 at 3:25 AM Steffen Klassert
[off-list ref] wrote:

quoted

This adds a new NETIF_F_GRO_LIST feature flag. I will be used
to configure listfyed GRO what will be implemented with some
followup paches.

This should probably simultaneously introduce SKB_GSO_FRAGLIST as well
as a BUILD_BUG_ON in net_gso_ok.

Please also in the commit describe the constraints of skbs that have
this type. If I'm not mistaken, an skb with either gso_size linear
data or one gso_sized frag, followed by a frag_list of the same. With
the exception of the last frag_list member, whose mss may be less than
gso_size. This will help when reasoning about all the types of skbs we
may see at segmentation, as we recently had to do [1]

Would it be preferrable to allow any size skbs for the listification.

We currently require a single gso_size because we adjust uh->len
on the head skb to the full size to do correct memory accounting
on the local input path. That is going to be restored with the
gso_size on segmentation.

Since the original skbs are being restored, single gso_size shoudln't
be a constraint here.

It might be possible to allow any sized skbs with some extra work, though.