[Intel-wired-lan] [PATCH net-next] bpf, i40e: add meta data support

[Bowers, AndrewX]

This patch is breaking ping, with the patch applied the ICMP packets are arriving corrupted on the receiving end. Reverting the patch fixes the problem. Pcap file attached. 

--Andrew


> -----Original Message-----
> From: Intel-wired-lan [mailto:intel-wired-lan-bounces at osuosl.org] On
> Behalf Of Daniel Borkmann
> Sent: Monday, May 28, 2018 2:07 AM
> To: Kirsher, Jeffrey T <jeffrey.t.kirsher at intel.com>
> Cc: intel-wired-lan at lists.osuosl.org; daniel at iogearbox.net
> Subject: [Intel-wired-lan] [PATCH net-next] bpf, i40e: add meta data support
> 
> Add support for XDP meta data when using build skb variant of the i40e
> driver. Implementation is analogous to the existing ixgbe and ixgbevf support
> for meta data from 366a88fe2f40 ("bpf,
> ixgbe: add meta data support") and be8333322eff ("ixgbevf: Add support for
> meta data"). With the build skb variant we get
> 192 bytes of extra headroom which can be used for encaps or meta data.
> 
> Signed-off-by: Daniel Borkmann <daniel at iogearbox.net>
> Acked-by: John Fastabend <john.fastabend at gmail.com>
> Tested-by: John Fastabend <john.fastabend at gmail.com>
> ---
>  drivers/net/ethernet/intel/i40e/i40e_txrx.c | 39
> +++++++++++++++++++++++------
>  1 file changed, 31 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
> b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
> index 9b698c5..eee6e91 100644
> --- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
> +++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
> @@ -2032,6 +2032,21 @@ static struct sk_buff *i40e_construct_skb(struct
> i40e_ring *rx_ring,  #if L1_CACHE_BYTES < 128
>  	prefetch(xdp->data + L1_CACHE_BYTES);
>  #endif
> +	/* Note, we get here by enabling legacy-rx via:
> +	 *
> +	 *    ethtool --set-priv-flags <dev> legacy-rx on
> +	 *
> +	 * In this mode, we currently get 0 extra XDP headroom as
> +	 * opposed to having legacy-rx off, where we process XDP
> +	 * packets going to stack via i40e_build_skb(). The latter
> +	 * provides us currently with 192 bytes of headroom.
> +	 *
> +	 * For i40e_construct_skb() mode it means that the
> +	 * xdp->data_meta will always point to xdp->data, since
> +	 * the helper cannot expand the head. Should this ever
> +	 * change in future for legacy-rx mode on, then lets also
> +	 * add xdp->data_meta handling here.
> +	 */
> 
>  	/* allocate a skb to store the frags */
>  	skb = __napi_alloc_skb(&rx_ring->q_vector->napi,
> @@ -2083,19 +2098,25 @@ static struct sk_buff *i40e_build_skb(struct
> i40e_ring *rx_ring,
>  				      struct i40e_rx_buffer *rx_buffer,
>  				      struct xdp_buff *xdp)
>  {
> -	unsigned int size = xdp->data_end - xdp->data;
> +	unsigned int metasize = xdp->data - xdp->data_meta;
>  #if (PAGE_SIZE < 8192)
>  	unsigned int truesize = i40e_rx_pg_size(rx_ring) / 2;  #else
>  	unsigned int truesize = SKB_DATA_ALIGN(sizeof(struct
> skb_shared_info)) +
> -				SKB_DATA_ALIGN(I40E_SKB_PAD + size);
> +				SKB_DATA_ALIGN(I40E_SKB_PAD +
> +					       (xdp->data_end -
> +						xdp->data_hard_start));
>  #endif
>  	struct sk_buff *skb;
> 
> -	/* prefetch first cache line of first page */
> -	prefetch(xdp->data);
> +	/* Prefetch first cache line of first page. If xdp->data_meta
> +	 * is unused, this points extactly as xdp->data, otherwise we
> +	 * likely have a consumer accessing first few bytes of meta
> +	 * data, and then actual data.
> +	 */
> +	prefetch(xdp->data_meta);
>  #if L1_CACHE_BYTES < 128
> -	prefetch(xdp->data + L1_CACHE_BYTES);
> +	prefetch(xdp->data_meta + L1_CACHE_BYTES);
>  #endif
>  	/* build an skb around the page buffer */
>  	skb = build_skb(xdp->data_hard_start, truesize); @@ -2103,8
> +2124,10 @@ static struct sk_buff *i40e_build_skb(struct i40e_ring *rx_ring,
>  		return NULL;
> 
>  	/* update pointers within the skb to store the data */
> -	skb_reserve(skb, I40E_SKB_PAD);
> -	__skb_put(skb, size);
> +	skb_reserve(skb, I40E_SKB_PAD + (xdp->data - xdp-
> >data_hard_start));
> +	__skb_put(skb, xdp->data_end - xdp->data);
> +	if (metasize)
> +		skb_metadata_set(skb, metasize);
> 
>  	/* buffer is used by skb, update page_offset */  #if (PAGE_SIZE <
> 8192) @@ -2341,7 +2364,7 @@ static int i40e_clean_rx_irq(struct i40e_ring
> *rx_ring, int budget)
>  		if (!skb) {
>  			xdp.data = page_address(rx_buffer->page) +
>  				   rx_buffer->page_offset;
> -			xdp_set_data_meta_invalid(&xdp);
> +			xdp.data_meta = xdp.data;
>  			xdp.data_hard_start = xdp.data -
>  					      i40e_rx_offset(rx_ring);
>  			xdp.data_end = xdp.data + size;
> --
> 2.9.5
> 
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