xdp: Add xdp_do_redirect_frame() for pre-computed xdp_frames

Add an xdp_do_redirect_frame() variant which supports pre-computed
xdp_frame structures. This will be used in bpf_prog_run() to avoid having
to write to the xdp_frame structure when the XDP program doesn't modify the
frame boundaries.

Signed-off-by: Toke Høiland-Jørgensen <[e-mail]>
Signed-off-by: Alexei Starovoitov <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]

include/linux/filter.h

···
 int xdp_do_redirect(struct net_device *dev,
 		    struct xdp_buff *xdp,
 		    struct bpf_prog *prog);
+int xdp_do_redirect_frame(struct net_device *dev,
+			  struct xdp_buff *xdp,
+			  struct xdp_frame *xdpf,
+			  struct bpf_prog *prog);
 void xdp_do_flush(void);
 
 /* The xdp_do_flush_map() helper has been renamed to drop the _map suffix, as

net/core/filter.c

···
 }
 EXPORT_SYMBOL_GPL(xdp_master_redirect);
 
-int xdp_do_redirect(struct net_device *dev, struct xdp_buff *xdp,
-		    struct bpf_prog *xdp_prog)
+static inline int __xdp_do_redirect_xsk(struct bpf_redirect_info *ri,
+					struct net_device *dev,
+					struct xdp_buff *xdp,
+					struct bpf_prog *xdp_prog)
 {
-	struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
 	enum bpf_map_type map_type = ri->map_type;
 	void *fwd = ri->tgt_value;
 	u32 map_id = ri->map_id;
-	struct xdp_frame *xdpf;
+	int err;
+
+	ri->map_id = 0; /* Valid map id idr range: [1,INT_MAX[ */
+	ri->map_type = BPF_MAP_TYPE_UNSPEC;
+
+	err = __xsk_map_redirect(fwd, xdp);
+	if (unlikely(err))
+		goto err;
+
+	_trace_xdp_redirect_map(dev, xdp_prog, fwd, map_type, map_id, ri->tgt_index);
+	return 0;
+err:
+	_trace_xdp_redirect_map_err(dev, xdp_prog, fwd, map_type, map_id, ri->tgt_index, err);
+	return err;
+}
+
+static __always_inline int __xdp_do_redirect_frame(struct bpf_redirect_info *ri,
+						   struct net_device *dev,
+						   struct xdp_frame *xdpf,
+						   struct bpf_prog *xdp_prog)
+{
+	enum bpf_map_type map_type = ri->map_type;
+	void *fwd = ri->tgt_value;
+	u32 map_id = ri->map_id;
 	struct bpf_map *map;
 	int err;
 
 	ri->map_id = 0; /* Valid map id idr range: [1,INT_MAX[ */
 	ri->map_type = BPF_MAP_TYPE_UNSPEC;
 
-	if (map_type == BPF_MAP_TYPE_XSKMAP) {
-		err = __xsk_map_redirect(fwd, xdp);
-		goto out;
-	}
-
-	xdpf = xdp_convert_buff_to_frame(xdp);
 	if (unlikely(!xdpf)) {
 		err = -EOVERFLOW;
 		goto err;
···
 		err = -EBADRQC;
 	}
 
-out:
 	if (unlikely(err))
 		goto err;
 
···
 	_trace_xdp_redirect_map_err(dev, xdp_prog, fwd, map_type, map_id, ri->tgt_index, err);
 	return err;
 }
+
+int xdp_do_redirect(struct net_device *dev, struct xdp_buff *xdp,
+		    struct bpf_prog *xdp_prog)
+{
+	struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
+	enum bpf_map_type map_type = ri->map_type;
+
+	if (map_type == BPF_MAP_TYPE_XSKMAP)
+		return __xdp_do_redirect_xsk(ri, dev, xdp, xdp_prog);
+
+	return __xdp_do_redirect_frame(ri, dev, xdp_convert_buff_to_frame(xdp),
+				       xdp_prog);
+}
 EXPORT_SYMBOL_GPL(xdp_do_redirect);
+
+int xdp_do_redirect_frame(struct net_device *dev, struct xdp_buff *xdp,
+			  struct xdp_frame *xdpf, struct bpf_prog *xdp_prog)
+{
+	struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
+	enum bpf_map_type map_type = ri->map_type;
+
+	if (map_type == BPF_MAP_TYPE_XSKMAP)
+		return __xdp_do_redirect_xsk(ri, dev, xdp, xdp_prog);
+
+	return __xdp_do_redirect_frame(ri, dev, xdpf, xdp_prog);
+}
+EXPORT_SYMBOL_GPL(xdp_do_redirect_frame);
 
 static int xdp_do_generic_redirect_map(struct net_device *dev,
 				       struct sk_buff *skb,