Re: [PATCH net-next 2/8] udp: skip fwd/list GRO for tunnel packets

On Mon, 2021-03-22 at 09:24 -0400, Willem de Bruijn wrote:

On Sun, Mar 21, 2021 at 1:01 PM Paolo Abeni [off-list ref] wrote:

quoted

If UDP GRO forwarding (or list) is enabled,

Please explicitly mention the gso type SKB_GSO_FRAGLIST. I, at least,
didn't immediately grasp that gro forwarding is an alias for that.

I see the commit message was not clear at all, I'm sorry.

The above means:

gso_type & (NETIF_F_GSO_UDP_L4 | NETIF_F_GSO_FRAGLIST) 

:)

quoted

and there are
udp tunnel available in the system, we could end-up doing L4
aggregation for packets targeting the UDP tunnel.

Is this specific to UDP tunnels, or can this also occur with others,
such as GRE? (not implying that this patchset needs to address those
at the same time)

I did not look at that before your suggestion. Thanks for pointing out.

I think the problem is specific to UDP: when processing the outer UDP
header that is potentially eligible for both NETIF_F_GSO_UDP_L4 and
gro_receive aggregation and that is the root cause of the problem
addressed here.

quoted

Just skip the fwd GRO if this packet could land in an UDP
tunnel.

Could you make more clear that this does not skip UDP GRO, only
switches from fraglist-based to pure SKB_GSO_UDP_L4.

Sure, I'll try to rewrite the commit message.

Thanks!

Paolo