xdp: add reporting of offload mode

Extend the XDP_ATTACHED_* values to include offloaded mode.
Let drivers report whether program is installed in the driver
or the HW by changing the prog_attached field from bool to
u8 (type of the netlink attribute).

Exploit the fact that the value of XDP_ATTACHED_DRV is 1,
therefore since all drivers currently assign the mode with
double negation:
       mode = !!xdp_prog;
no drivers have to be modified.
Signed-off-by: NJakub Kicinski <jakub.kicinski@netronome.com>
Acked-by: NDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -809,7 +809,8 @@ enum xdp_netdev_command {
 	XDP_SETUP_PROG,
 	XDP_SETUP_PROG_HW,
 	/* Check if a bpf program is set on the device.  The callee should
-	 * return true if a program is currently attached and running.
+	 * set @prog_attached to one of XDP_ATTACHED_* values, note that "true"
+	 * is equivalent to XDP_ATTACHED_DRV.
 	 */
 	XDP_QUERY_PROG,
 };
@@ -827,7 +828,7 @@ struct netdev_xdp {
 		};
 		/* XDP_QUERY_PROG */
 		struct {
-			bool prog_attached;
+			u8 prog_attached;
 			u32 prog_id;
 		};
 	};
@@ -3307,7 +3308,7 @@ struct sk_buff *dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
 typedef int (*xdp_op_t)(struct net_device *dev, struct netdev_xdp *xdp);
 int dev_change_xdp_fd(struct net_device *dev, struct netlink_ext_ack *extack,
 		      int fd, u32 flags);
-bool __dev_xdp_attached(struct net_device *dev, xdp_op_t xdp_op, u32 *prog_id);
+u8 __dev_xdp_attached(struct net_device *dev, xdp_op_t xdp_op, u32 *prog_id);
 
 int __dev_forward_skb(struct net_device *dev, struct sk_buff *skb);
 int dev_forward_skb(struct net_device *dev, struct sk_buff *skb);

include/uapi/linux/if_link.h

@@ -903,6 +903,7 @@ enum {
 	XDP_ATTACHED_NONE = 0,
 	XDP_ATTACHED_DRV,
 	XDP_ATTACHED_SKB,
+	XDP_ATTACHED_HW,
 };
 
 enum {

net/core/dev.c

@@ -6934,8 +6934,7 @@ int dev_change_proto_down(struct net_device *dev, bool proto_down)
 }
 EXPORT_SYMBOL(dev_change_proto_down);
 
-bool __dev_xdp_attached(struct net_device *dev, xdp_op_t xdp_op,
-			u32 *prog_id)
+u8 __dev_xdp_attached(struct net_device *dev, xdp_op_t xdp_op, u32 *prog_id)
 {
 	struct netdev_xdp xdp;
 

net/core/rtnetlink.c

@@ -1265,10 +1265,10 @@ static u8 rtnl_xdp_attached_mode(struct net_device *dev, u32 *prog_id)
 		*prog_id = generic_xdp_prog->aux->id;
 		return XDP_ATTACHED_SKB;
 	}
-	if (ops->ndo_xdp && __dev_xdp_attached(dev, ops->ndo_xdp, prog_id))
-		return XDP_ATTACHED_DRV;
+	if (!ops->ndo_xdp)
+		return XDP_ATTACHED_NONE;
 
-	return XDP_ATTACHED_NONE;
+	return __dev_xdp_attached(dev, ops->ndo_xdp, prog_id);
 }
 
 static int rtnl_xdp_fill(struct sk_buff *skb, struct net_device *dev)