Re: [PATCH bpf-next 09/10] [bpf]: make tun compatible w/ bpf_xdp_adjust_tail

Jason Wang
2018-04-18T02:16:31Z

On 2018年04月17日 14:51, Nikita V. Shirokov wrote:
> w/ bpf_xdp_adjust_tail helper xdp's data_end pointer could be changed as
> well (only "decrease" of pointer's location is going to be supported).
> changing of this pointer will change packet's size.
> for tun driver we need to adjust XDP_PASS handling by recalculating
> length of the packet if it was passed to the TCP/IP stack
> (in case if after xdp's prog run data_end pointer was adjusted)
>
> Signed-off-by: Nikita V. Shirokov <tehnerd@tehnerd.com>
> ---
> drivers/net/tun.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index 28583aa0c17d..0b488a958076 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -1688,6 +1688,7 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
> return NULL;
> case XDP_PASS:
> delta = orig_data - xdp.data;
> + len = xdp.data_end - xdp.data;
> break;
> default:
> bpf_warn_invalid_xdp_action(act);
> @@ -1708,7 +1709,7 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
> }
>
> skb_reserve(skb, pad - delta);
> - skb_put(skb, len + delta);
> + skb_put(skb, len);
> get_page(alloc_frag->page);
> alloc_frag->offset += buflen;
>

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