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Date: Mon, 05 Nov 2007 19:00:19 +0100 From: Patrick McHardy <kaber@...sh.net> To: Dave Johnson <djohnson+linux-kernel@...starentnetworks.com> CC: David Miller <davem@...emloft.net>, jes@...ined-monkey.org, mchan@...adcom.com, ram.vepa@...erion.com, linux-kernel@...r.kernel.org, netdev@...r.kernel.org, bguo@...starentnetworks.com Subject: Re: [PATCH 1/2] NET: Re-add VLAN tag for devices incapable of keeping it Dave Johnson wrote: > +/* VLAN rx hw acceleration helper. This acts like netif_{rx,receive_skb}(). */ > +static inline int __vlan_hwaccel_rx(struct sk_buff *skb, > + struct vlan_group *grp, > + unsigned short vlan_tag, int polling) > +{ > ... > + /* Driver removed vlan tag from the packet, but we have no > + * vlan device for this VID. > + * > + * This can occur for 2 reasons: > + * 1) Have a vlan group, we want some VIDs, just not this VID. > + * 2) Have no vlan group, but hardware limitation requires it > + * to remove vlan tags anyway. > + * > + * Normally if no vlan group is configured, the underlying > + * driver will configure the hardware to NOT strip out the > + * vlan tag. It can then call netif_receive_skb/netif_rx > + * with the vlan tag still intact. However some devices > + * cannot be configured to keep the vlan tag and must not > + * call netif_receive_skb/netif_rx with the vlan tag > + * missing. This would allow the normal protocol handlers > + * to process this tagged packet as if it arived without a > + * vlan tag. > + * > + * We need to re-add the TAG and hand the packet off to the > + * base device with the TAG present so any protocol handlers > + * (PF_PACKET, etc...) will get a chance to see it. > + */ This looks like a rather expensive operation for the unlikely case that packets will be received by a packet socket. IMO it should only be reconstructed if actually needed, by af_packet itself. As we discussed some time back storing the VLAN tag in the CB on TX clashes with other users of the CB like qdiscs, so we need a new field in the skb for this anyway. - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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