Re: [PATCH net-next 02/11] tuntap: switch to use XDP_PACKET_HEADROOM

[Jason Wang]

On 2018å09æ07æ 00:57, Michael S. Tsirkin wrote:
> On Thu, Sep 06, 2018 at 12:05:17PM +0800, Jason Wang wrote:
> > Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
> Acked-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
>
> any idea why didn't we do this straight away?

Dunno, but git grep told me not all XDP capable driver use this (e.g 
virtio_net has its own value).

Anyway, I think it's ok for driver to have their specific value if they 
can make sure the value is equal or greater than XDP_PACKET_HEADROOM.

Thanks

> > ---
> >   drivers/net/tun.c | 3 +--
> >   1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> > index 2c548bd20393..d3677a544b56 100644
> > --- a/drivers/net/tun.c
> > +++ b/drivers/net/tun.c
> > @@ -113,7 +113,6 @@ do {								\
> >   } while (0)
> >   #endif
> >   
> > -#define TUN_HEADROOM 256
> >   #define TUN_RX_PAD (NET_IP_ALIGN + NET_SKB_PAD)
> >   
> >   /* TUN device flags */
> > @@ -1654,7 +1653,7 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
> >   	rcu_read_lock();
> >   	xdp_prog = rcu_dereference(tun->xdp_prog);
> >   	if (xdp_prog)
> > -		pad += TUN_HEADROOM;
> > +		pad += XDP_PACKET_HEADROOM;
> >   	buflen += SKB_DATA_ALIGN(len + pad);
> >   	rcu_read_unlock();
> >   
> > --
> > 2.17.1