On 2018年09月07日 00:57, Michael S. Tsirkin wrote:

On Thu, Sep 06, 2018 at 12:05:17PM +0800, Jason Wang wrote:

quoted

Signed-off-by: Jason Wang <jasowang@redhat.com>

Acked-by: Michael S. Tsirkin <mst@redhat.com>

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

quoted

---
  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

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