On Fri, 2016-04-01 at 18:21 -0700, Brenden Blanco wrote: > Add support for the BPF_PROG_TYPE_PHYS_DEV hook in mlx4 driver. Since > bpf programs require a skb context to navigate the packet, build a > percpu fake skb with the minimal fields. This avoids the costly > allocation for packets that end up being dropped. >
> + /* A bpf program gets first chance to drop the packet. It may > + * read bytes but not past the end of the frag. A non-zero > + * return indicates packet should be dropped. > + */ > + if (prog) { > + struct ethhdr *ethh; > + > + ethh = (struct ethhdr *)(page_address(frags[0].page) + > + frags[0].page_offset); > + if (mlx4_call_bpf(prog, ethh, length)) { > + priv->stats.rx_dropped++; > + goto next; > + } > + } > + 1) mlx4 can use multiple fragments (priv->num_frags) to hold an Ethernet frame. Still you pass a single fragment but total 'length' here : BPF program can read past the end of this first fragment and panic the box. Please take a look at mlx4_en_complete_rx_desc() and you'll see what I mean. 2) priv->stats.rx_dropped is shared by all the RX queues -> false sharing. This is probably the right time to add a rx_dropped field in struct mlx4_en_rx_ring since you guys want to drop 14 Mpps, and 50 Mpps on higher speed links.