From: Jesper Dangaard Brouer <brouer@redhat.com>
Date: Wed, 3 Jan 2018 11:26:14 +0100
Subject: bpf: finally expose xdp_rxq_info to XDP bpf-programs
Patch-mainline: v4.16-rc1
Git-commit: 02dd3291b2f095bbc88e1d2628fd5bf2e92de69b
References: bsc#1109837

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 <brouer@redhat.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 include/uapi/linux/bpf.h |    3 +++
 net/core/filter.c        |   19 +++++++++++++++++++
 2 files changed, 22 insertions(+)

--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -891,6 +891,9 @@ 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 {
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4305,6 +4305,25 @@ static u32 xdp_convert_ctx_access(enum b
 				      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;