On 04/09/2017 10:35 PM, David Miller wrote:
[...]
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;
Should this be moved rather near other rx members for locality?
My config has last member of rx group in a new cacheline, which
is really waste ...
[...]
/* --- cacheline 14 boundary (896 bytes) --- */
struct hlist_node index_hlist; /* 896 16 */
/* XXX 48 bytes hole, try to pack */
[...]
... but given this layout can change significantly for a given
config, perhaps could be a union with something exotic that is
currently always built in like ax25_ptr; would then require to
depend on ax25 not being built, though. :/ Otoh, we potentially
have to linearize the skb in data path, which is slow anyway,
so probably okay as is, too.
[...]
@@ -4247,6 +4248,83 @@ static int __netif_receive_skb(struct sk_buff *skb)
return ret;
}
+static struct static_key generic_xdp_needed __read_mostly;
+
+static int generic_xdp_install(struct net_device *dev, struct netdev_xdp *xdp)
+{
+ struct bpf_prog *new = xdp->prog;
+ int ret = 0;
+
+ switch (xdp->command) {
+ case XDP_SETUP_PROG: {
+ struct bpf_prog *old = rtnl_dereference(dev->xdp_prog);
+
+ rcu_assign_pointer(dev->xdp_prog, new);
+ if (old)
+ bpf_prog_put(old);
+
+ if (old && !new)
+ static_key_slow_dec(&generic_xdp_needed);
+ else if (new && !old)
+ static_key_slow_inc(&generic_xdp_needed);
+ break;
+ }
+
+ case XDP_QUERY_PROG:
+ xdp->prog_attached = !!rcu_access_pointer(dev->xdp_prog);
+ break;
Would be nice to extend this here, so that in the current 'ip link'
output we could indicate next to the 'xdp' flag that this does /not/
run natively in the driver.
Also, when the user loads a prog f.e. via 'ip link set dev em1 xdp obj prog.o',
we should add a flag where it could be specified that running non-natively
/is/ okay. Thus that the rtnl bits bail out if there's no ndo_xdp callback.
I could imagine that this could be overseen quickly and people wonder why
performance is significantly less than usually expected.
+
+ default:
+ ret = -EINVAL;
+ break;
+ }
+
+ return ret;
+}
+
+static u32 netif_receive_generic_xdp(struct sk_buff *skb,
+ struct bpf_prog *xdp_prog)
+{
+ struct xdp_buff xdp;
+ u32 act = XDP_DROP;
+ void *orig_data;
+ int hlen, off;
+
+ if (skb_linearize(skb))
+ goto do_drop;
+
+ hlen = skb_headlen(skb);
+ xdp.data = skb->data;
+ xdp.data_end = xdp.data + hlen;
+ xdp.data_hard_start = xdp.data - skb_headroom(skb);
+ orig_data = xdp.data;
Wondering regarding XDP_PACKET_HEADROOM requirement,
presumably we would need to guarantee enough headroom
here as well, so that there's no difference to a native
driver implementation.
+ act = bpf_prog_run_xdp(xdp_prog, &xdp);
+
+ off = xdp.data - orig_data;
+ if (off)
+ __skb_push(skb, off);
+
+ switch (act) {
+ case XDP_PASS:
+ case XDP_TX:
+ break;
+
+ default:
+ bpf_warn_invalid_xdp_action(act);
+ /* fall through */
+ case XDP_ABORTED:
+ trace_xdp_exception(skb->dev, xdp_prog, act);
+ /* fall through */
+ case XDP_DROP:
+ do_drop:
+ kfree_skb(skb);
+ break;
+ }
+
+ return act;
+}
