[bpf-next PATCH] bpf: simplify xdp_convert_ctx_access for xdp_rxq_info

[bpf-next PATCH] bpf: simplify xdp_convert_ctx_access for xdp_rxq_info

[Jesper Dangaard Brouer]

As pointed out by Daniel Borkmann, using bpf_target_off() is not
necessary for xdp_rxq_info when extracting queue_index and
ifindex, as these members are u32 like BPF_W.

Also fix trivial spelling mistake introduced in same commit.

Fixes: 02dd3291b2f0 ("bpf: finally expose xdp_rxq_info to XDP bpf-programs")
Reported-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
 include/uapi/linux/bpf.h |    2 +-
 net/core/filter.c        |    7 +++----
 2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 405317f9c064..395d261948de 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -899,7 +899,7 @@ struct xdp_md {
 	__u32 data;
 	__u32 data_end;
 	__u32 data_meta;
-	/* Below access go though struct xdp_rxq_info */
+	/* Below access go through struct xdp_rxq_info */
 	__u32 ingress_ifindex; /* rxq->dev->ifindex */
 	__u32 rx_queue_index;  /* rxq->queue_index  */
 };
diff --git a/net/core/filter.c b/net/core/filter.c
index acdb94c0e97f..4ce50306154d 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4312,16 +4312,15 @@ static u32 xdp_convert_ctx_access(enum bpf_access_type type,
 				      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));
+				      offsetof(struct net_device, ifindex));
 		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));
+				      offsetof(struct xdp_rxq_info,
+					       queue_index));
 		break;
 	}
 

Re: [bpf-next PATCH] bpf: simplify xdp_convert_ctx_access for xdp_rxq_info

[Daniel Borkmann]

On 01/11/2018 05:39 PM, Jesper Dangaard Brouer wrote:
> As pointed out by Daniel Borkmann, using bpf_target_off() is not
> necessary for xdp_rxq_info when extracting queue_index and
> ifindex, as these members are u32 like BPF_W.
> 
> Also fix trivial spelling mistake introduced in same commit.
> 
> Fixes: 02dd3291b2f0 ("bpf: finally expose xdp_rxq_info to XDP bpf-programs")
> Reported-by: Daniel Borkmann <daniel@iogearbox.net>
> Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>

Applied to bpf-next, thanks Jesper!