[PATCH bpf-next] xdp: introduce convert_to_xdp_buff utility routine

[Lorenzo Bianconi <lorenzo@xxxxxxxxxx>]

Introduce convert_to_xdp_buff utility routine to initialize xdp_buff
fields from xdp_frames ones. Rely on convert_to_xdp_buff in veth xdp
code

Suggested-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
Signed-off-by: Lorenzo Bianconi <lorenzo@xxxxxxxxxx>
---
 drivers/net/veth.c | 12 ++----------
 include/net/xdp.h  | 10 ++++++++++
 2 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index b586d2fa5551..dfbe553f967e 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -559,27 +559,19 @@ static struct sk_buff *veth_xdp_rcv_one(struct veth_rq *rq,
 					struct veth_xdp_tx_bq *bq,
 					struct veth_stats *stats)
 {
-	void *hard_start = frame->data - frame->headroom;
 	int len = frame->len, delta = 0;
 	struct xdp_frame orig_frame;
 	struct bpf_prog *xdp_prog;
 	unsigned int headroom;
 	struct sk_buff *skb;
 
-	/* bpf_xdp_adjust_head() assures BPF cannot access xdp_frame area */
-	hard_start -= sizeof(struct xdp_frame);
-
 	rcu_read_lock();
 	xdp_prog = rcu_dereference(rq->xdp_prog);
 	if (likely(xdp_prog)) {
 		struct xdp_buff xdp;
 		u32 act;
 
-		xdp.data_hard_start = hard_start;
-		xdp.data = frame->data;
-		xdp.data_end = frame->data + frame->len;
-		xdp.data_meta = frame->data - frame->metasize;
-		xdp.frame_sz = frame->frame_sz;
+		convert_to_xdp_buff(frame, &xdp);
 		xdp.rxq = &rq->xdp_rxq;
 
 		act = bpf_prog_run_xdp(xdp_prog, &xdp);
@@ -626,7 +618,7 @@ static struct sk_buff *veth_xdp_rcv_one(struct veth_rq *rq,
 	rcu_read_unlock();
 
 	headroom = sizeof(struct xdp_frame) + frame->headroom - delta;
-	skb = veth_build_skb(hard_start, headroom, len, frame->frame_sz);
+	skb = veth_build_skb(frame, headroom, len, frame->frame_sz);
 	if (!skb) {
 		xdp_return_frame(frame);
 		stats->rx_drops++;
diff --git a/include/net/xdp.h b/include/net/xdp.h
index 90f11760bd12..5dbdd65866a9 100644
--- a/include/net/xdp.h
+++ b/include/net/xdp.h
@@ -106,6 +106,16 @@ void xdp_warn(const char *msg, const char *func, const int line);
 
 struct xdp_frame *xdp_convert_zc_to_xdp_frame(struct xdp_buff *xdp);
 
+static inline
+void convert_to_xdp_buff(struct xdp_frame *frame, struct xdp_buff *xdp)
+{
+	xdp->data_hard_start = (void *)frame;
+	xdp->data = frame->data;
+	xdp->data_end = frame->data + frame->len;
+	xdp->data_meta = frame->data - frame->metasize;
+	xdp->frame_sz = frame->frame_sz;
+}
+
 /* Convert xdp_buff to xdp_frame */
 static inline
 struct xdp_frame *convert_to_xdp_frame(struct xdp_buff *xdp)
-- 
2.26.2