net: xdp: make the stack take care of the tear down

Since day one of XDP drivers had to remember to free the program
on the remove path.  This leads to code duplication and is error
prone.  Make the stack query the installed programs on unregister
and if something is installed, remove the program.  Freeing of
program attached to XDP generic is moved from free_netdev() as well.

Because the remove will now be called before notifiers are
invoked, BPF offload state of the program will not get destroyed
before uninstall.

Signed-off-by: Jakub Kicinski <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Reviewed-by: Quentin Monnet <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>

Author: Jakub Kicinski

drivers/net/ethernet/broadcom/bnxt/bnxt.c

@@ -7800,8 +7800,6 @@ static void bnxt_remove_one(struct pci_dev *pdev)
 	bnxt_dcb_free(bp);
 	kfree(bp->edev);
 	bp->edev = NULL;
-	if (bp->xdp_prog)
-		bpf_prog_put(bp->xdp_prog);
 	bnxt_cleanup_pci(bp);
 	free_netdev(dev);
 }

drivers/net/ethernet/mellanox/mlx5/core/en_main.c

@@ -4308,9 +4308,6 @@ static void mlx5e_nic_cleanup(struct mlx5e_priv *priv)
 {
 	mlx5e_ipsec_cleanup(priv);
 	mlx5e_vxlan_cleanup(priv);
-
-	if (priv->channels.params.xdp_prog)
-		bpf_prog_put(priv->channels.params.xdp_prog);
 }
 
 static int mlx5e_init_nic_rx(struct mlx5e_priv *priv)

drivers/net/ethernet/netronome/nfp/bpf/main.c

@@ -82,12 +82,6 @@ static const char *nfp_bpf_extra_cap(struct nfp_app *app, struct nfp_net *nn)
 	return nfp_net_ebpf_capable(nn) ? "BPF" : "";
 }
 
-static void nfp_bpf_vnic_free(struct nfp_app *app, struct nfp_net *nn)
-{
-	if (nn->dp.bpf_offload_xdp)
-		nfp_bpf_xdp_offload(app, nn, NULL);
-}
-
 static int nfp_bpf_setup_tc_block_cb(enum tc_setup_type type,
 				     void *type_data, void *cb_priv)
 {
@@ -168,7 +162,6 @@ const struct nfp_app_type app_bpf = {
 	.extra_cap	= nfp_bpf_extra_cap,
 
 	.vnic_alloc	= nfp_app_nic_vnic_alloc,
-	.vnic_free	= nfp_bpf_vnic_free,
 
 	.setup_tc	= nfp_bpf_setup_tc,
 	.tc_busy	= nfp_bpf_tc_busy,

drivers/net/ethernet/netronome/nfp/nfp_net_common.c

@@ -3562,9 +3562,6 @@ struct nfp_net *nfp_net_alloc(struct pci_dev *pdev, bool needs_netdev,
  */
 void nfp_net_free(struct nfp_net *nn)
 {
-	if (nn->xdp_prog)
-		bpf_prog_put(nn->xdp_prog);
-
 	if (nn->dp.netdev)
 		free_netdev(nn->dp.netdev);
 	else

drivers/net/ethernet/qlogic/qede/qede_main.c

@@ -1068,10 +1068,6 @@ static void __qede_remove(struct pci_dev *pdev, enum qede_remove_mode mode)
 
 	pci_set_drvdata(pdev, NULL);
 
-	/* Release edev's reference to XDP's bpf if such exist */
-	if (edev->xdp_prog)
-		bpf_prog_put(edev->xdp_prog);
-
 	/* Use global ops since we've freed edev */
 	qed_ops->common->slowpath_stop(cdev);
 	if (system_state == SYSTEM_POWER_OFF)

drivers/net/tun.c

@@ -673,7 +673,6 @@ static void tun_detach(struct tun_file *tfile, bool clean)
 static void tun_detach_all(struct net_device *dev)
 {
 	struct tun_struct *tun = netdev_priv(dev);
-	struct bpf_prog *xdp_prog = rtnl_dereference(tun->xdp_prog);
 	struct tun_file *tfile, *tmp;
 	int i, n = tun->numqueues;
 
@@ -708,9 +707,6 @@ static void tun_detach_all(struct net_device *dev)
 	}
 	BUG_ON(tun->numdisabled != 0);
 
-	if (xdp_prog)
-		bpf_prog_put(xdp_prog);
-
 	if (tun->flags & IFF_PERSIST)
 		module_put(THIS_MODULE);
 }

net/core/dev.c

@@ -7110,6 +7110,27 @@ static int dev_xdp_install(struct net_device *dev, bpf_op_t bpf_op,
 	return bpf_op(dev, &xdp);
 }
 
+static void dev_xdp_uninstall(struct net_device *dev)
+{
+	struct netdev_bpf xdp;
+	bpf_op_t ndo_bpf;
+
+	/* Remove generic XDP */
+	WARN_ON(dev_xdp_install(dev, generic_xdp_install, NULL, 0, NULL));
+
+	/* Remove from the driver */
+	ndo_bpf = dev->netdev_ops->ndo_bpf;
+	if (!ndo_bpf)
+		return;
+
+	__dev_xdp_query(dev, ndo_bpf, &xdp);
+	if (xdp.prog_attached == XDP_ATTACHED_NONE)
+		return;
+
+	/* Program removal should always succeed */
+	WARN_ON(dev_xdp_install(dev, ndo_bpf, NULL, xdp.prog_flags, NULL));
+}
+
 /**
  *	dev_change_xdp_fd - set or clear a bpf program for a device rx path
  *	@dev: device
@@ -7240,6 +7261,7 @@ static void rollback_registered_many(struct list_head *head)
 		/* Shutdown queueing discipline. */
 		dev_shutdown(dev);
 
+		dev_xdp_uninstall(dev);
 
 		/* Notify protocols, that we are about to destroy
 		 * this device. They should clean all the things.
@@ -8199,7 +8221,6 @@ EXPORT_SYMBOL(alloc_netdev_mqs);
 void free_netdev(struct net_device *dev)
 {
 	struct napi_struct *p, *n;
-	struct bpf_prog *prog;
 
 	might_sleep();
 	netif_free_tx_queues(dev);
@@ -8218,12 +8239,6 @@ void free_netdev(struct net_device *dev)
 	free_percpu(dev->pcpu_refcnt);
 	dev->pcpu_refcnt = NULL;
 
-	prog = rcu_dereference_protected(dev->xdp_prog, 1);
-	if (prog) {
-		bpf_prog_put(prog);
-		static_key_slow_dec(&generic_xdp_needed);
-	}
-
 	/*  Compatibility with error handling in drivers */
 	if (dev->reg_state == NETREG_UNINITIALIZED) {
 		netdev_freemem(dev);