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

[Jason Wang]

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:

Signed-off-by: Jason Wang 

Acked-by: Michael S. Tsirkin 

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


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

[Michael S. Tsirkin]

On Thu, Sep 06, 2018 at 12:05:17PM +0800, Jason Wang wrote:
> Signed-off-by: Jason Wang 

Acked-by: Michael S. Tsirkin 

any idea why didn't we do this straight away?

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

[Jason Wang]

Signed-off-by: Jason Wang 
---
 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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