On Sun, 09 Apr 2017 13:35:28 -0700 (PDT)
David Miller <davem@xxxxxxxxxxxxx> wrote:
> This provides a generic non-optimized XDP implementation when the
> device driver does not provide an optimized one.
>
> It is arguable that perhaps I should have required something like
> this as part of the initial XDP feature merge.
>
> I believe this is critical for two reasons:
>
> 1) Accessibility. More people can play with XDP with less
> dependencies. Yes I know we have XDP support in virtio_net, but
> that just creates another depedency for learning how to use this
> facility.
>
> I wrote this to make life easier for the XDP newbies.
>
> 2) As a model for what the expected semantics are. If there is a pure
> generic core implementation, it serves as a semantic example for
> driver folks adding XDP support.
>
> This is just a rough draft and is untested.
>
> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Agreed, XDP really needs this
> v2:
> - Add some "fall through" comments in switch statements based
> upon feedback from Andrew Lunn
> - Use RCU for generic xdp_prog, thanks to Johannes Berg.
>
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index cc07c3b..f8ff49c 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -1892,6 +1892,7 @@ struct net_device {
> struct lock_class_key *qdisc_tx_busylock;
> struct lock_class_key *qdisc_running_key;
> bool proto_down;
> + struct bpf_prog __rcu *xdp_prog;
> };
> #define to_net_dev(d) container_of(d, struct net_device, dev)
>
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 7efb417..ad6de2d 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
...
> + if (static_key_false(&generic_xdp_needed)) {
> + struct bpf_prog *xdp_prog = rcu_dereference(skb->dev->xdp_prog);
> +
> + if (xdp_prog) {
> + u32 act = netif_receive_generic_xdp(skb, xdp_prog);
> +
> + if (act != XDP_PASS) {
> + rcu_read_unlock();
> + if (act == XDP_TX)
> + dev_queue_xmit(skb);
> + return NET_RX_DROP;
> + }
Wouldn't it be cleaner if XDP returned an enumerated type and a
switch was used? Safer than allowing arbitrary int.
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