bpf: cpumap xdp_buff to skb conversion and allocation

This patch makes cpumap functional, by adding SKB allocation and
invoking the network stack on the dequeuing CPU.

For constructing the SKB on the remote CPU, the xdp_buff in converted
into a struct xdp_pkt, and it mapped into the top headroom of the
packet, to avoid allocating separate mem.  For now, struct xdp_pkt is
just a cpumap internal data structure, with info carried between
enqueue to dequeue.

If a driver doesn't have enough headroom it is simply dropped, with
return code -EOVERFLOW.  This will be picked up the xdp tracepoint
infrastructure, to allow users to catch this.

V2: take into account xdp->data_meta

V4:
 - Drop busypoll tricks, keeping it more simple.
 - Skip RPS and Generic-XDP-recursive-reinjection, suggested by Alexei

V5: correct RCU read protection around __netif_receive_skb_core.

V6: Setting TASK_RUNNING vs TASK_INTERRUPTIBLE based on talk with Rik van Riel

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 27 insertions, 0 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index d2b20e73080e..cf5894f0e6eb 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4492,6 +4492,33 @@ out:
 	return ret;
 }
 
+/**
+ *	netif_receive_skb_core - special purpose version of netif_receive_skb
+ *	@skb: buffer to process
+ *
+ *	More direct receive version of netif_receive_skb().  It should
+ *	only be used by callers that have a need to skip RPS and Generic XDP.
+ *	Caller must also take care of handling if (page_is_)pfmemalloc.
+ *
+ *	This function may only be called from softirq context and interrupts
+ *	should be enabled.
+ *
+ *	Return values (usually ignored):
+ *	NET_RX_SUCCESS: no congestion
+ *	NET_RX_DROP: packet was dropped
+ */
+int netif_receive_skb_core(struct sk_buff *skb)
+{
+	int ret;
+
+	rcu_read_lock();
+	ret = __netif_receive_skb_core(skb, false);
+	rcu_read_unlock();
+
+	return ret;
+}
+EXPORT_SYMBOL(netif_receive_skb_core);
+
 static int __netif_receive_skb(struct sk_buff *skb)
 {
 	int ret;