Meaning of data_len and meta_len RX WB descriptor fields is
slightly confusing. Add a comment with a diagram clarifying
the layout. Also remove the buffer length validation:
(a) it's imprecise for static rx-offsets; (b) if firmware
is buggy enough to DMA past the end of the buffer
WARN_ON_ONCE() doesn't seem like a strong enough response.
skb_put() will do the checking for us anyway.
Signed-off-by: Jakub Kicinski <jakub.kicin...@netronome.com>
---
.../net/ethernet/netronome/nfp/nfp_net_common.c | 26 ++++++++++++----------
1 file changed, 14 insertions(+), 12 deletions(-)
diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
index 0bdff390c958..5235e86eb684 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
+++ b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
@@ -1298,23 +1298,25 @@ static int nfp_net_rx(struct nfp_net_rx_ring *rx_ring,
int budget)
nfp_net_rx_give_one(rx_ring, new_skb, new_dma_addr);
+ /* < meta_len >
+ * <-- [rx_offset] -->
+ * ---------------------------------------------------------
+ * | [XX] | metadata | packet | XXXX |
+ * ---------------------------------------------------------
+ * <---------------- data_len --------------->
+ *
+ * The rx_offset is fixed for all packets, the meta_len can vary
+ * on a packet by packet basis. If rx_offset is set to zero
+ * (_RX_OFFSET_DYNAMIC) metadata starts at the beginning of the
+ * buffer and is immediately followed by the packet (no [XX]).
+ */
meta_len = rxd->rxd.meta_len_dd & PCIE_DESC_RX_META_LEN_MASK;
data_len = le16_to_cpu(rxd->rxd.data_len);
- if (WARN_ON_ONCE(data_len > nn->fl_bufsz)) {
- dev_kfree_skb_any(skb);
- continue;
- }
-
- if (nn->rx_offset == NFP_NET_CFG_RX_OFFSET_DYNAMIC) {
- /* The packet data starts after the metadata */
+ if (nn->rx_offset == NFP_NET_CFG_RX_OFFSET_DYNAMIC)
skb_reserve(skb, meta_len);
- } else {
- /* The packet data starts at a fixed offset */
+ else
skb_reserve(skb, nn->rx_offset);
- }
-
- /* Adjust the SKB for the dynamic meta data pre-pended */
skb_put(skb, data_len - meta_len);
nfp_net_set_hash(nn->netdev, skb, rxd);
--
1.9.1
