Re: [PATCH net-next] tun/macvtap: use consume_skb() instead of kfree_skb() in tun/macvtap_do_read()

From: Eric Dumazet
Date: Wed Nov 26 2014 - 01:26:09 EST


On Wed, 2014-11-26 at 14:08 +0800, Jason Wang wrote:
> To be more friendly with drop monitor, we should use comsume_skb() instead
> of kfree_skb() in tun/macvtap_do_read(). Otherwise, the packets will be
> marked as dropped.
>
> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
> ---
> drivers/net/macvtap.c | 2 +-
> drivers/net/tun.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
> index 42a80d3..74d1b23 100644
> --- a/drivers/net/macvtap.c
> +++ b/drivers/net/macvtap.c
> @@ -862,7 +862,7 @@ static ssize_t macvtap_do_read(struct macvtap_queue *q,
> }
> iov_iter_init(&iter, READ, iv, segs, len);
> ret = macvtap_put_user(q, skb, &iter);
> - kfree_skb(skb);
> + consume_skb(skb);
> break;
> }
>
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index ac53a73..d7edeaf 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -1363,7 +1363,7 @@ static ssize_t tun_do_read(struct tun_struct *tun, struct tun_file *tfile,
>
> iov_iter_init(&iter, READ, iv, segs, len);
> ret = tun_put_user(tun, tfile, skb, &iter);
> - kfree_skb(skb);
> + consume_skb(skb);
>
> return ret;
> }


These patches keep going on, but they are wrong.

If you care about drop monitor, then you want to not hide drops but
precisely report them.

Surely tun_put_user() can return an error, and then packet _is_ dropped.



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/