[RFC PATCH v2 bpf-next 04/15] xdp: Export dev_check_xdp and dev_change_xdp

[Toshiaki Makita <toshiaki.makita1@xxxxxxxxx>]

Factor out the check and change logic from dev_change_xdp_fd(),
and export them for the following commit.

Signed-off-by: Toshiaki Makita <toshiaki.makita1@xxxxxxxxx>
---
 include/linux/netdevice.h |   4 ++
 net/core/dev.c            | 111 +++++++++++++++++++++++++++++++++++++---------
 2 files changed, 95 insertions(+), 20 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 3207e0b..c338a73 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3707,6 +3707,10 @@ struct sk_buff *dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
 				    struct netdev_queue *txq, int *ret);
 
 typedef int (*bpf_op_t)(struct net_device *dev, struct netdev_bpf *bpf);
+int dev_check_xdp(struct net_device *dev, struct netlink_ext_ack *extack,
+		  bool do_install, u32 *prog_id_p, u32 flags);
+int dev_change_xdp(struct net_device *dev, struct netlink_ext_ack *extack,
+		   struct bpf_prog *prod, u32 flags);
 int dev_change_xdp_fd(struct net_device *dev, struct netlink_ext_ack *extack,
 		      int fd, u32 flags);
 u32 __dev_xdp_query(struct net_device *dev, bpf_op_t xdp_op,
diff --git a/net/core/dev.c b/net/core/dev.c
index 8bc3dce..9965675 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -8317,23 +8317,24 @@ static void dev_xdp_uninstall(struct net_device *dev)
 }
 
 /**
- *	dev_change_xdp_fd - set or clear a bpf program for a device rx path
+ *	dev_check_xdp - check if xdp prog can be [un]installed
  *	@dev: device
  *	@extack: netlink extended ack
- *	@fd: new program fd or negative value to clear
+ *	@install: flag to install or uninstall
+ *	@prog_id_p: pointer to a storage for program id
  *	@flags: xdp-related flags
  *
- *	Set or clear a bpf program for a device
+ *	Check if xdp prog can be [un]installed
+ *	If a program is already loaded, store the prog id to prog_id_p
  */
-int dev_change_xdp_fd(struct net_device *dev, struct netlink_ext_ack *extack,
-		      int fd, u32 flags)
+int dev_check_xdp(struct net_device *dev, struct netlink_ext_ack *extack,
+		  bool install, u32 *prog_id_p, u32 flags)
 {
 	const struct net_device_ops *ops = dev->netdev_ops;
 	enum bpf_netdev_command query;
-	struct bpf_prog *prog = NULL;
 	bpf_op_t bpf_op, bpf_chk;
 	bool offload;
-	int err;
+	u32 prog_id;
 
 	ASSERT_RTNL();
 
@@ -8350,28 +8351,64 @@ int dev_change_xdp_fd(struct net_device *dev, struct netlink_ext_ack *extack,
 	if (bpf_op == bpf_chk)
 		bpf_chk = generic_xdp_install;
 
-	if (fd >= 0) {
-		u32 prog_id;
-
+	if (install) {
 		if (!offload && __dev_xdp_query(dev, bpf_chk, XDP_QUERY_PROG)) {
 			NL_SET_ERR_MSG(extack, "native and generic XDP can't be active at the same time");
 			return -EEXIST;
 		}
 
 		prog_id = __dev_xdp_query(dev, bpf_op, query);
+		if (prog_id_p)
+			*prog_id_p = prog_id;
 		if ((flags & XDP_FLAGS_UPDATE_IF_NOEXIST) && prog_id) {
 			NL_SET_ERR_MSG(extack, "XDP program already attached");
 			return -EBUSY;
 		}
+	} else {
+		prog_id = __dev_xdp_query(dev, bpf_op, query);
+		if (prog_id_p)
+			*prog_id_p = prog_id;
+		if (!prog_id)
+			return -ENOENT;
+	}
 
-		prog = bpf_prog_get_type_dev(fd, BPF_PROG_TYPE_XDP,
-					     bpf_op == ops->ndo_bpf);
-		if (IS_ERR(prog))
-			return PTR_ERR(prog);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(dev_check_xdp);
+
+/**
+ *	dev_change_xdp - set or clear a bpf program for a device rx path
+ *	@dev: device
+ *	@extack: netlink extended ack
+ *	@prog: bpf progam
+ *	@flags: xdp-related flags
+ *
+ *	Set or clear a bpf program for a device.
+ *	Caller must call dev_check_xdp before calling this function to
+ *	check if xdp prog can be [un]installed.
+ */
+int dev_change_xdp(struct net_device *dev, struct netlink_ext_ack *extack,
+		   struct bpf_prog *prog, u32 flags)
+{
+	const struct net_device_ops *ops = dev->netdev_ops;
+	enum bpf_netdev_command query;
+	bpf_op_t bpf_op;
+	bool offload;
+
+	ASSERT_RTNL();
+
+	offload = flags & XDP_FLAGS_HW_MODE;
+	query = offload ? XDP_QUERY_PROG_HW : XDP_QUERY_PROG;
+
+	bpf_op = ops->ndo_bpf;
+	if (!bpf_op || (flags & XDP_FLAGS_SKB_MODE))
+		bpf_op = generic_xdp_install;
+
+	if (prog) {
+		u32 prog_id = __dev_xdp_query(dev, bpf_op, query);
 
 		if (!offload && bpf_prog_is_dev_bound(prog->aux)) {
 			NL_SET_ERR_MSG(extack, "using device-bound program without HW_MODE flag is not supported");
-			bpf_prog_put(prog);
 			return -EINVAL;
 		}
 
@@ -8379,13 +8416,47 @@ int dev_change_xdp_fd(struct net_device *dev, struct netlink_ext_ack *extack,
 			bpf_prog_put(prog);
 			return 0;
 		}
-	} else {
-		if (!__dev_xdp_query(dev, bpf_op, query))
-			return 0;
 	}
 
-	err = dev_xdp_install(dev, bpf_op, extack, flags, prog);
-	if (err < 0 && prog)
+	return dev_xdp_install(dev, bpf_op, extack, flags, prog);
+}
+EXPORT_SYMBOL_GPL(dev_change_xdp);
+
+/**
+ *	dev_change_xdp_fd - set or clear a bpf program for a device rx path
+ *	@dev: device
+ *	@extack: netlink extended ack
+ *	@fd: new program fd or negative value to clear
+ *	@flags: xdp-related flags
+ *
+ *	Set or clear a bpf program for a device
+ */
+int dev_change_xdp_fd(struct net_device *dev, struct netlink_ext_ack *extack,
+		      int fd, u32 flags)
+{
+	struct bpf_prog *prog = NULL;
+	bool install = fd >= 0;
+	int err;
+
+	err = dev_check_xdp(dev, extack, install, NULL, flags);
+	if (err) {
+		if (!install && err == -ENOENT)
+			err = 0;
+		return err;
+	}
+
+	if (install) {
+		bool attach_drv;
+
+		attach_drv = dev->netdev_ops->ndo_bpf &&
+			     !(flags & XDP_FLAGS_SKB_MODE);
+		prog = bpf_prog_get_type_dev(fd, BPF_PROG_TYPE_XDP, attach_drv);
+		if (IS_ERR(prog))
+			return PTR_ERR(prog);
+	}
+
+	err = dev_change_xdp(dev, extack, prog, flags);
+	if (err && prog)
 		bpf_prog_put(prog);
 
 	return err;
-- 
1.8.3.1