bpf, ixgbe: add meta data support

Implement support for transferring XDP meta data into skb for
ixgbe driver; before calling into the program, xdp.data_meta points
to xdp.data, where on program return with pass verdict, we call
into skb_metadata_set().

We implement this for the default ixgbe_build_skb() variant. For the
ixgbe_construct_skb() that is used when legacy-rx buffer mananagement
mode is turned on via ethtool, I found that XDP gets 0 headroom, so
neither xdp_adjust_head() nor xdp_adjust_meta() can be used with this.
Just add a comment with explanation for this operating mode.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index 04bb03b..3942c62 100644 (file)
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -2133,6 +2133,21 @@ static struct sk_buff *ixgbe_construct_skb(struct ixgbe_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 ixgbe_build_skb(). The latter
+        * provides us currently with 192 bytes of headroom.
+        *
+        * For ixgbe_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, IXGBE_RX_HDR_SIZE);
@@ -2165,6 +2180,7 @@ static struct sk_buff *ixgbe_build_skb(struct ixgbe_ring *rx_ring,
                                       struct xdp_buff *xdp,
                                       union ixgbe_adv_rx_desc *rx_desc)
 {
+       unsigned int metasize = xdp->data - xdp->data_meta;
 #if (PAGE_SIZE < 8192)
        unsigned int truesize = ixgbe_rx_pg_size(rx_ring) / 2;
 #else
@@ -2174,10 +2190,14 @@ static struct sk_buff *ixgbe_build_skb(struct ixgbe_ring *rx_ring,
 #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 to around the page buffer */
@@ -2188,6 +2208,8 @@ static struct sk_buff *ixgbe_build_skb(struct ixgbe_ring *rx_ring,
        /* update pointers within the skb to store the data */
        skb_reserve(skb, xdp->data - xdp->data_hard_start);
        __skb_put(skb, xdp->data_end - xdp->data);
+       if (metasize)
+               skb_metadata_set(skb, metasize);
 
        /* record DMA address if this is the start of a chain of buffers */
        if (!ixgbe_test_staterr(rx_desc, IXGBE_RXD_STAT_EOP))
@@ -2326,7 +2348,7 @@ static int ixgbe_clean_rx_irq(struct ixgbe_q_vector *q_vector,
                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 -
                                              ixgbe_rx_offset(rx_ring);
                        xdp.data_end = xdp.data + size;