bpf: devmap: check XDP features in __xdp_enqueue routine

Check if the destination device implements ndo_xdp_xmit callback relying
on NETDEV_XDP_ACT_NDO_XMIT flags. Moreover, check if the destination device
supports XDP non-linear frame in __xdp_enqueue and is_valid_dst routines.
This patch allows to perform XDP_REDIRECT on non-linear XDP buffers.

Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Co-developed-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://lore.kernel.org/r/26a94c33520c0bfba021b3fbb2cb8c1e69bf53b8.1675245258.git.lorenzo@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

kernel/bpf/devmap.c

@@ -474,7 +474,11 @@ static inline int __xdp_enqueue(struct net_device *dev, struct xdp_frame *xdpf,
 {
 	int err;
 
-	if (!dev->netdev_ops->ndo_xdp_xmit)
+	if (!(dev->xdp_features & NETDEV_XDP_ACT_NDO_XMIT))
+		return -EOPNOTSUPP;
+
+	if (unlikely(!(dev->xdp_features & NETDEV_XDP_ACT_NDO_XMIT_SG) &&
+		     xdp_frame_has_frags(xdpf)))
 		return -EOPNOTSUPP;
 
 	err = xdp_ok_fwd_dev(dev, xdp_get_frame_len(xdpf));
@@ -532,8 +536,14 @@ int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_frame *xdpf,
 
 static bool is_valid_dst(struct bpf_dtab_netdev *obj, struct xdp_frame *xdpf)
 {
-	if (!obj ||
-	    !obj->dev->netdev_ops->ndo_xdp_xmit)
+	if (!obj)
+		return false;
+
+	if (!(obj->dev->xdp_features & NETDEV_XDP_ACT_NDO_XMIT))
+		return false;
+
+	if (unlikely(!(obj->dev->xdp_features & NETDEV_XDP_ACT_NDO_XMIT_SG) &&
+		     xdp_frame_has_frags(xdpf)))
 		return false;
 
 	if (xdp_ok_fwd_dev(obj->dev, xdp_get_frame_len(xdpf)))

net/core/filter.c

@@ -4318,16 +4318,13 @@ int xdp_do_redirect(struct net_device *dev, struct xdp_buff *xdp,
 	struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
 	enum bpf_map_type map_type = ri->map_type;
 
-	/* XDP_REDIRECT is not fully supported yet for xdp frags since
-	 * not all XDP capable drivers can map non-linear xdp_frame in
-	 * ndo_xdp_xmit.
-	 */
-	if (unlikely(xdp_buff_has_frags(xdp) &&
-		     map_type != BPF_MAP_TYPE_CPUMAP))
-		return -EOPNOTSUPP;
+	if (map_type == BPF_MAP_TYPE_XSKMAP) {
+		/* XDP_REDIRECT is not supported AF_XDP yet. */
+		if (unlikely(xdp_buff_has_frags(xdp)))
+			return -EOPNOTSUPP;
 
-	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);