Subject: Re: [PATCH] NET: Proper handling of IPv6 header in tun driver when TUN_NO_PI is set

From: Max Krasnyanskiy <[email-masked]>
Date: Fri, 06 Jun 2008 13:21:06 -0700

Acked-by: Max Krasnyansky <[email-masked]>

Dave, can you please add this patch to your tree.

--
Steve, this is what I meant by "we do not need extra copy_from_user". We 
already do copy into the SKB and can parse the header right there.

Max

Ang Way Chuang wrote:
> By default, tun.c running in TUN_TUN_DEV mode will set the protocol of 
> packet to IPv4 if TUN_NO_PI is set. My program failed to work when I 
> assumed that the driver will check the first nibble of packet, determine 
> IP version and set the appropriate protocol.
> 
> The test for this change was conducted on 2.6.24.7 kernel. But the diff 
> is produced using git commit
> c3b25b32e8bef526cca748e1ba023c6bdd705a99. I couldn't test it on kernel 
> version greater than 2.6.25 due to out of tree driver failing to 
> compile. But tun_get_user doesn't change that much between 2.6.24 and 
> 2.6.26, so it should work, I hope :-D. This patch is trivial because 
> this problem can also be fixed by not using TUN_NO_PI.
> 
> Signed-off-by: Ang Way Chuang <[email-masked]>
> ---
> 
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index 0ce07a3..77964bc 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -313,6 +313,21 @@ static __inline__ ssize_t tun_get_user(struct 
> tun_struct *tun, struct iovec *iv,
> 
>         switch (tun->flags & TUN_TYPE_MASK) {
>         case TUN_TUN_DEV:
> +               if (tun->flags & TUN_NO_PI) {
> +                       switch (skb->data[0] & 0xf0) {
> +                       case 0x40:
> +                               pi.proto = __constant_htons(ETH_P_IP);
> +                               break;
> +                       case 0x60:
> +                               pi.proto = __constant_htons(ETH_P_IPV6);
> +                               break;
> +                       default:
> +                               tun->dev->stats.rx_dropped++;
> +                               kfree_skb(skb);
> +                               return -EINVAL;
> +                       }
> +               }
> +
>                 skb_reset_mac_header(skb);
>                 skb->protocol = pi.proto;
>                 skb->dev = tun->dev;
> 
> -- 
>