Now all XDP driver have been updated to setup xdp_rxq_info and assign
this to xdp_buff->rxq.  Thus, it is now safe to enable access to some
of the xdp_rxq_info struct members.

This patch extend xdp_md and expose UAPI to userspace for
ingress_ifindex and rx_queue_index.  Access happens via bpf
instruction rewrite, that load data directly from struct xdp_rxq_info.

* ingress_ifindex map to xdp_rxq_info->dev->ifindex
* rx_queue_index  map to xdp_rxq_info->queue_index

Signed-off-by: Jesper Dangaard Brouer <redacted>
---
 include/uapi/linux/bpf.h |    3 +++
 net/core/filter.c        |   19 +++++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 69eabfcb9bdb..a6000a95d40e 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h

@@ -899,6 +899,9 @@ struct xdp_md {
 	__u32 data;
 	__u32 data_end;
 	__u32 data_meta;
+	/* Below access go though struct xdp_rxq_info */
+	__u32 ingress_ifindex; /* rxq->dev->ifindex */
+	__u32 rx_queue_index;  /* rxq->queue_index  */
 };
 
 enum sk_action {