[bpf-next V3 PATCH 13/14] bpf: finally expose xdp_rxq_info to XDP bpf-programs

[Jesper Dangaard Brouer]

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 <bro...@redhat.com>
---
 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 {
diff --git a/net/core/filter.c b/net/core/filter.c
index 130b842c3a15..acdb94c0e97f 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4304,6 +4304,25 @@ static u32 xdp_convert_ctx_access(enum bpf_access_type 
type,
                                      si->dst_reg, si->src_reg,
                                      offsetof(struct xdp_buff, data_end));
                break;
+       case offsetof(struct xdp_md, ingress_ifindex):
+               *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct xdp_buff, rxq),
+                                     si->dst_reg, si->src_reg,
+                                     offsetof(struct xdp_buff, rxq));
+               *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct xdp_rxq_info, 
dev),
+                                     si->dst_reg, si->dst_reg,
+                                     offsetof(struct xdp_rxq_info, dev));
+               *insn++ = BPF_LDX_MEM(BPF_W, si->dst_reg, si->dst_reg,
+                                     bpf_target_off(struct net_device,
+                                                    ifindex, 4, target_size));
+               break;
+       case offsetof(struct xdp_md, rx_queue_index):
+               *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct xdp_buff, rxq),
+                                     si->dst_reg, si->src_reg,
+                                     offsetof(struct xdp_buff, rxq));
+               *insn++ = BPF_LDX_MEM(BPF_W, si->dst_reg, si->dst_reg,
+                                     bpf_target_off(struct xdp_rxq_info,
+                                               queue_index, 4, target_size));
+               break;
        }
 
        return insn - insn_buf;