[PATCH bpf-next RFCv3 5/6] veth: add AF_XDP RX support.

[William Tu]

If the receiving veth side has umem rx enabled, the patch
directly copy the packet from the peer side's send buffer
to the umem receive buffer.  This requires running AF_XDP
as both side of the veth peer.  For example:
Receiver:
  # ip netns exec at_ns0 xdpsock -r -N -z -i p0
Sender:
  # xdpsock -i p1 -t -N -z
The performance increases from 1.4Mpps to 2.3Mpps.

Signed-off-by: William Tu <u9012...@gmail.com>
---
 drivers/net/veth.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index 551444195398..8aac67554880 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -766,11 +766,28 @@ static int veth_xsk_poll(struct napi_struct *napi, int 
budget)
                struct sk_buff *skb;
                struct page *page;
                void *vaddr;
+               u64 handle;
                u32 len;
 
                if (!xsk_umem_consume_tx_virtual(peer_rq->xsk_umem, &vaddr, 
&len))
                        break;
 
+               if (rq->xsk_umem && xsk_umem_peek_addr(rq->xsk_umem, &handle)) {
+                       char *daddr;
+                       u64 hr = 0;
+
+                       /* the peer side also has umem enabled,
+                        * copy directly to it.
+                        */
+                       handle &= rq->xsk_umem->chunk_mask;
+                       hr = rq->xsk_umem->headroom + XDP_PACKET_HEADROOM;
+                       daddr = xdp_umem_get_data(rq->xsk_umem, handle);
+                       daddr += hr;
+                       memcpy((void *)daddr, vaddr, len);
+                       xsk_umem_discard_addr(rq->xsk_umem);
+                       vaddr = daddr;
+               }
+
                xdpf.data = vaddr + metasize;
                xdpf.len = len;
                xdpf.headroom = 0;
-- 
2.7.4