From: Jakub Kicinski <kuba@xxxxxxxxxx> Date: Wed, 4 Oct 2023 11:08:50 -0700 > On Tue, 3 Oct 2023 15:09:39 +0200 Alexander Lobakin wrote: >>> Sorry for a random chime-in but was there any discussion about >>> the validity of VLAN stripping as an offload? >>> >>> I always thought this is a legacy "Windows" thing which allowed >>> Windows drivers to operate on VLAN-tagged networks even before >>> the OS itself understood VLANs... Do people actually care about >>> having it enabled? >> >> On MIPS routers, I actually have some perf gains from having it enabled. >> So they do, I'd say. Mediatek even has DSA tag stripping. Both save you >> some skb->data push-pulls, csum corrections when CHECKSUM_COMPLETE, skb >> unsharing in some cases, reduce L3/L4 headers cacheline spanning etc. > > No unsharing - you can still strip it in the driver. Nobody manually strips VLAN tags in the drivers. You either have HW stripping or pass VLAN-tagged skb to the stack, so that skb_vlan_untag() takes care of it. > Do you really think that for XDP kfunc call will be cheaper? Wait, you initially asked: * discussion about the validity of VLAN stripping as an offload? * Do people actually care about having it enabled? I did read this as "do we still need HW VLAN stripping in general?", not only for XDP. So I replied for "in general" -- yes. Forcefully disabling stripping when XDP is active is obscure IMO, let the user decide. Thanks, Olek
