include/net/udp_tunnel.h - linux - Git at Google

 /* SPDX-License-Identifier: GPL-2.0 */
 #ifndef __NET_UDP_TUNNEL_H
 #define __NET_UDP_TUNNEL_H

 #include <net/ip_tunnels.h>
 #include <net/udp.h>

 #if IS_ENABLED(CONFIG_IPV6)
 #include <net/ipv6.h>
 #include <net/ipv6_stubs.h>
 #endif

 struct udp_port_cfg {
 	u8			family;

 	/* Used only for kernel-created sockets */
 	union {
 		struct in_addr		local_ip;
 #if IS_ENABLED(CONFIG_IPV6)
 		struct in6_addr		local_ip6;
 #endif
 	};

 	union {
 		struct in_addr		peer_ip;
 #if IS_ENABLED(CONFIG_IPV6)
 		struct in6_addr		peer_ip6;
 #endif
 	};

 	__be16			local_udp_port;
 	__be16			peer_udp_port;
 	int			bind_ifindex;
 	unsigned int		use_udp_checksums:1,
 				use_udp6_tx_checksums:1,
 				use_udp6_rx_checksums:1,
 				ipv6_v6only:1;
 };

 int udp_sock_create4(struct net *net, struct udp_port_cfg *cfg,
 		     struct socket **sockp);

 #if IS_ENABLED(CONFIG_IPV6)
 int udp_sock_create6(struct net *net, struct udp_port_cfg *cfg,
 		     struct socket **sockp);
 #else
 static inline int udp_sock_create6(struct net *net, struct udp_port_cfg *cfg,
 				   struct socket **sockp)
 {
 	return 0;
 }
 #endif

 static inline int udp_sock_create(struct net *net,
 				  struct udp_port_cfg *cfg,
 				  struct socket **sockp)
 {
 	if (cfg->family == AF_INET)
 		return udp_sock_create4(net, cfg, sockp);

 	if (cfg->family == AF_INET6)
 		return udp_sock_create6(net, cfg, sockp);

 	return -EPFNOSUPPORT;
 }

 typedef int (*udp_tunnel_encap_rcv_t)(struct sock *sk, struct sk_buff *skb);
 typedef int (*udp_tunnel_encap_err_lookup_t)(struct sock *sk,
 					     struct sk_buff *skb);
 typedef void (*udp_tunnel_encap_destroy_t)(struct sock *sk);
 typedef struct sk_buff *(*udp_tunnel_gro_receive_t)(struct sock *sk,
 						    struct list_head *head,
 						    struct sk_buff *skb);
 typedef int (*udp_tunnel_gro_complete_t)(struct sock *sk, struct sk_buff *skb,
 					 int nhoff);

 struct udp_tunnel_sock_cfg {
 	void *sk_user_data;     /* user data used by encap_rcv call back */
 	/* Used for setting up udp_sock fields, see udp.h for details */
 	__u8  encap_type;
 	udp_tunnel_encap_rcv_t encap_rcv;
 	udp_tunnel_encap_err_lookup_t encap_err_lookup;
 	udp_tunnel_encap_destroy_t encap_destroy;
 	udp_tunnel_gro_receive_t gro_receive;
 	udp_tunnel_gro_complete_t gro_complete;
 };

 /* Setup the given (UDP) sock to receive UDP encapsulated packets */
 void setup_udp_tunnel_sock(struct net *net, struct socket *sock,
 			   struct udp_tunnel_sock_cfg *sock_cfg);

 /* -- List of parsable UDP tunnel types --
  *
  * Adding to this list will result in serious debate.  The main issue is
  * that this list is essentially a list of workarounds for either poorly
  * designed tunnels, or poorly designed device offloads.
  *
  * The parsing supported via these types should really be used for Rx
  * traffic only as the network stack will have already inserted offsets for
  * the location of the headers in the skb.  In addition any ports that are
  * pushed should be kept within the namespace without leaking to other
  * devices such as VFs or other ports on the same device.
  *
  * It is strongly encouraged to use CHECKSUM_COMPLETE for Rx to avoid the
  * need to use this for Rx checksum offload.  It should not be necessary to
  * call this function to perform Tx offloads on outgoing traffic.
  */
 enum udp_parsable_tunnel_type {
 	UDP_TUNNEL_TYPE_VXLAN	  = BIT(0), /* RFC 7348 */
 	UDP_TUNNEL_TYPE_GENEVE	  = BIT(1), /* draft-ietf-nvo3-geneve */
 	UDP_TUNNEL_TYPE_VXLAN_GPE = BIT(2), /* draft-ietf-nvo3-vxlan-gpe */
 };

 struct udp_tunnel_info {
 	unsigned short type;
 	sa_family_t sa_family;
 	__be16 port;
 	u8 hw_priv;
 };

 /* Notify network devices of offloadable types */
 void udp_tunnel_push_rx_port(struct net_device *dev, struct socket *sock,
 			     unsigned short type);
 void udp_tunnel_drop_rx_port(struct net_device *dev, struct socket *sock,
 			     unsigned short type);
 void udp_tunnel_notify_add_rx_port(struct socket *sock, unsigned short type);
 void udp_tunnel_notify_del_rx_port(struct socket *sock, unsigned short type);

 static inline void udp_tunnel_get_rx_info(struct net_device *dev)
 {
 	ASSERT_RTNL();
 	call_netdevice_notifiers(NETDEV_UDP_TUNNEL_PUSH_INFO, dev);
 }

 static inline void udp_tunnel_drop_rx_info(struct net_device *dev)
 {
 	ASSERT_RTNL();
 	call_netdevice_notifiers(NETDEV_UDP_TUNNEL_DROP_INFO, dev);
 }

 /* Transmit the skb using UDP encapsulation. */
 void udp_tunnel_xmit_skb(struct rtable *rt, struct sock *sk, struct sk_buff *skb,
 			 __be32 src, __be32 dst, __u8 tos, __u8 ttl,
 			 __be16 df, __be16 src_port, __be16 dst_port,
 			 bool xnet, bool nocheck);

 int udp_tunnel6_xmit_skb(struct dst_entry *dst, struct sock *sk,
 			 struct sk_buff *skb,
 			 struct net_device *dev, struct in6_addr *saddr,
 			 struct in6_addr *daddr,
 			 __u8 prio, __u8 ttl, __be32 label,
 			 __be16 src_port, __be16 dst_port, bool nocheck);

 void udp_tunnel_sock_release(struct socket *sock);

 struct metadata_dst *udp_tun_rx_dst(struct sk_buff *skb, unsigned short family,
 				    __be16 flags, __be64 tunnel_id,
 				    int md_size);

 #ifdef CONFIG_INET
 static inline int udp_tunnel_handle_offloads(struct sk_buff *skb, bool udp_csum)
 {
 	int type = udp_csum ? SKB_GSO_UDP_TUNNEL_CSUM : SKB_GSO_UDP_TUNNEL;

 	return iptunnel_handle_offloads(skb, type);
 }
 #endif

 static inline void udp_tunnel_encap_enable(struct socket *sock)
 {
 	struct udp_sock *up = udp_sk(sock->sk);

 	if (up->encap_enabled)
 		return;

 	up->encap_enabled = 1;
 #if IS_ENABLED(CONFIG_IPV6)
 	if (sock->sk->sk_family == PF_INET6)
 		ipv6_stub->udpv6_encap_enable();
 	else
 #endif
 		udp_encap_enable();
 }

 #define UDP_TUNNEL_NIC_MAX_TABLES	4

 enum udp_tunnel_nic_info_flags {
 	/* Device callbacks may sleep */
 	UDP_TUNNEL_NIC_INFO_MAY_SLEEP	= BIT(0),
 	/* Device only supports offloads when it's open, all ports
 	 * will be removed before close and re-added after open.
 	 */
 	UDP_TUNNEL_NIC_INFO_OPEN_ONLY	= BIT(1),
 	/* Device supports only IPv4 tunnels */
 	UDP_TUNNEL_NIC_INFO_IPV4_ONLY	= BIT(2),
 	/* Device has hard-coded the IANA VXLAN port (4789) as VXLAN.
 	 * This port must not be counted towards n_entries of any table.
 	 * Driver will not receive any callback associated with port 4789.
 	 */
 	UDP_TUNNEL_NIC_INFO_STATIC_IANA_VXLAN	= BIT(3),
 };

 struct udp_tunnel_nic;

 #define UDP_TUNNEL_NIC_MAX_SHARING_DEVICES	(U16_MAX / 2)

 struct udp_tunnel_nic_shared {
 	struct udp_tunnel_nic *udp_tunnel_nic_info;

 	struct list_head devices;
 };

 struct udp_tunnel_nic_shared_node {
 	struct net_device *dev;
 	struct list_head list;
 };

 /**
  * struct udp_tunnel_nic_info - driver UDP tunnel offload information
  * @set_port:	callback for adding a new port
  * @unset_port:	callback for removing a port
  * @sync_table:	callback for syncing the entire port table at once
  * @shared:	reference to device global state (optional)
  * @flags:	device flags from enum udp_tunnel_nic_info_flags
  * @tables:	UDP port tables this device has
  * @tables.n_entries:		number of entries in this table
  * @tables.tunnel_types:	types of tunnels this table accepts
  *
  * Drivers are expected to provide either @set_port and @unset_port callbacks
  * or the @sync_table callback. Callbacks are invoked with rtnl lock held.
  *
  * Devices which (misguidedly) share the UDP tunnel port table across multiple
  * netdevs should allocate an instance of struct udp_tunnel_nic_shared and
  * point @shared at it.
  * There must never be more than %UDP_TUNNEL_NIC_MAX_SHARING_DEVICES devices
  * sharing a table.
  *
  * Known limitations:
  *  - UDP tunnel port notifications are fundamentally best-effort -
  *    it is likely the driver will both see skbs which use a UDP tunnel port,
  *    while not being a tunneled skb, and tunnel skbs from other ports -
  *    drivers should only use these ports for non-critical RX-side offloads,
  *    e.g. the checksum offload;
  *  - none of the devices care about the socket family at present, so we don't
  *    track it. Please extend this code if you care.
  */
 struct udp_tunnel_nic_info {
 	/* one-by-one */
 	int (*set_port)(struct net_device *dev,
 			unsigned int table, unsigned int entry,
 			struct udp_tunnel_info *ti);
 	int (*unset_port)(struct net_device *dev,
 			  unsigned int table, unsigned int entry,
 			  struct udp_tunnel_info *ti);

 	/* all at once */
 	int (*sync_table)(struct net_device *dev, unsigned int table);

 	struct udp_tunnel_nic_shared *shared;

 	unsigned int flags;

 	struct udp_tunnel_nic_table_info {
 		unsigned int n_entries;
 		unsigned int tunnel_types;
 	} tables[UDP_TUNNEL_NIC_MAX_TABLES];
 };

 /* UDP tunnel module dependencies
  *
  * Tunnel drivers are expected to have a hard dependency on the udp_tunnel
  * module. NIC drivers are not, they just attach their
  * struct udp_tunnel_nic_info to the netdev and wait for callbacks to come.
  * Loading a tunnel driver will cause the udp_tunnel module to be loaded
  * and only then will all the required state structures be allocated.
  * Since we want a weak dependency from the drivers and the core to udp_tunnel
  * we call things through the following stubs.
  */
 struct udp_tunnel_nic_ops {
 	void (*get_port)(struct net_device *dev, unsigned int table,
 			 unsigned int idx, struct udp_tunnel_info *ti);
 	void (*set_port_priv)(struct net_device *dev, unsigned int table,
 			      unsigned int idx, u8 priv);
 	void (*add_port)(struct net_device *dev, struct udp_tunnel_info *ti);
 	void (*del_port)(struct net_device *dev, struct udp_tunnel_info *ti);
 	void (*reset_ntf)(struct net_device *dev);

 	size_t (*dump_size)(struct net_device *dev, unsigned int table);
 	int (*dump_write)(struct net_device *dev, unsigned int table,
 			  struct sk_buff *skb);
 };

 #ifdef CONFIG_INET
 extern const struct udp_tunnel_nic_ops *udp_tunnel_nic_ops;
 #else
 #define udp_tunnel_nic_ops	((struct udp_tunnel_nic_ops *)NULL)
 #endif

 static inline void
 udp_tunnel_nic_get_port(struct net_device *dev, unsigned int table,
 			unsigned int idx, struct udp_tunnel_info *ti)
 {
 	/* This helper is used from .sync_table, we indicate empty entries
 	 * by zero'ed @ti. Drivers which need to know the details of a port
 	 * when it gets deleted should use the .set_port / .unset_port
 	 * callbacks.
 	 * Zero out here, otherwise !CONFIG_INET causes uninitilized warnings.
 	 */
 	memset(ti, 0, sizeof(*ti));

 	if (udp_tunnel_nic_ops)
 		udp_tunnel_nic_ops->get_port(dev, table, idx, ti);
 }

 static inline void
 udp_tunnel_nic_set_port_priv(struct net_device *dev, unsigned int table,
 			     unsigned int idx, u8 priv)
 {
 	if (udp_tunnel_nic_ops)
 		udp_tunnel_nic_ops->set_port_priv(dev, table, idx, priv);
 }

 static inline void
 udp_tunnel_nic_add_port(struct net_device *dev, struct udp_tunnel_info *ti)
 {
 	if (udp_tunnel_nic_ops)
 		udp_tunnel_nic_ops->add_port(dev, ti);
 }

 static inline void
 udp_tunnel_nic_del_port(struct net_device *dev, struct udp_tunnel_info *ti)
 {
 	if (udp_tunnel_nic_ops)
 		udp_tunnel_nic_ops->del_port(dev, ti);
 }

 /**
  * udp_tunnel_nic_reset_ntf() - device-originating reset notification
  * @dev: network interface device structure
  *
  * Called by the driver to inform the core that the entire UDP tunnel port
  * state has been lost, usually due to device reset. Core will assume device
  * forgot all the ports and issue .set_port and .sync_table callbacks as
  * necessary.
  *
  * This function must be called with rtnl lock held, and will issue all
  * the callbacks before returning.
  */
 static inline void udp_tunnel_nic_reset_ntf(struct net_device *dev)
 {
 	if (udp_tunnel_nic_ops)
 		udp_tunnel_nic_ops->reset_ntf(dev);
 }

 static inline size_t
 udp_tunnel_nic_dump_size(struct net_device *dev, unsigned int table)
 {
 	if (!udp_tunnel_nic_ops)
 		return 0;
 	return udp_tunnel_nic_ops->dump_size(dev, table);
 }

 static inline int
 udp_tunnel_nic_dump_write(struct net_device *dev, unsigned int table,
 			  struct sk_buff *skb)
 {
 	if (!udp_tunnel_nic_ops)
 		return 0;
 	return udp_tunnel_nic_ops->dump_write(dev, table, skb);
 }
 #endif
	/* SPDX-License-Identifier: GPL-2.0 */
	#ifndef __NET_UDP_TUNNEL_H
	#define __NET_UDP_TUNNEL_H

	#include <net/ip_tunnels.h>
	#include <net/udp.h>

	#if IS_ENABLED(CONFIG_IPV6)
	#include <net/ipv6.h>
	#include <net/ipv6_stubs.h>
	#endif

	struct udp_port_cfg {
	u8 family;

	/* Used only for kernel-created sockets */
	union {
	struct in_addr local_ip;
	#if IS_ENABLED(CONFIG_IPV6)
	struct in6_addr local_ip6;
	#endif
	};

	union {
	struct in_addr peer_ip;
	#if IS_ENABLED(CONFIG_IPV6)
	struct in6_addr peer_ip6;
	#endif
	};

	__be16 local_udp_port;
	__be16 peer_udp_port;
	int bind_ifindex;
	unsigned int use_udp_checksums:1,
	use_udp6_tx_checksums:1,
	use_udp6_rx_checksums:1,
	ipv6_v6only:1;
	};

	int udp_sock_create4(struct net net, struct udp_port_cfg cfg,
	struct socket **sockp);

	#if IS_ENABLED(CONFIG_IPV6)
	int udp_sock_create6(struct net net, struct udp_port_cfg cfg,
	struct socket **sockp);
	#else
	static inline int udp_sock_create6(struct net net, struct udp_port_cfg cfg,
	struct socket **sockp)
	{
	return 0;
	}
	#endif

	static inline int udp_sock_create(struct net *net,
	struct udp_port_cfg *cfg,
	struct socket **sockp)
	{
	if (cfg->family == AF_INET)
	return udp_sock_create4(net, cfg, sockp);

	if (cfg->family == AF_INET6)
	return udp_sock_create6(net, cfg, sockp);

	return -EPFNOSUPPORT;
	}

	typedef int (udp_tunnel_encap_rcv_t)(struct sock sk, struct sk_buff *skb);
	typedef int (udp_tunnel_encap_err_lookup_t)(struct sock sk,
	struct sk_buff *skb);
	typedef void (udp_tunnel_encap_destroy_t)(struct sock sk);
	typedef struct sk_buff (udp_tunnel_gro_receive_t)(struct sock *sk,
	struct list_head *head,
	struct sk_buff *skb);
	typedef int (udp_tunnel_gro_complete_t)(struct sock sk, struct sk_buff *skb,
	int nhoff);

	struct udp_tunnel_sock_cfg {
	void sk_user_data; / user data used by encap_rcv call back */
	/* Used for setting up udp_sock fields, see udp.h for details */
	__u8 encap_type;
	udp_tunnel_encap_rcv_t encap_rcv;
	udp_tunnel_encap_err_lookup_t encap_err_lookup;
	udp_tunnel_encap_destroy_t encap_destroy;
	udp_tunnel_gro_receive_t gro_receive;
	udp_tunnel_gro_complete_t gro_complete;
	};

	/* Setup the given (UDP) sock to receive UDP encapsulated packets */
	void setup_udp_tunnel_sock(struct net net, struct socket sock,
	struct udp_tunnel_sock_cfg *sock_cfg);

	/* -- List of parsable UDP tunnel types --
	*
	* Adding to this list will result in serious debate. The main issue is
	* that this list is essentially a list of workarounds for either poorly
	* designed tunnels, or poorly designed device offloads.
	*
	* The parsing supported via these types should really be used for Rx
	* traffic only as the network stack will have already inserted offsets for
	* the location of the headers in the skb. In addition any ports that are
	* pushed should be kept within the namespace without leaking to other
	* devices such as VFs or other ports on the same device.
	*
	* It is strongly encouraged to use CHECKSUM_COMPLETE for Rx to avoid the
	* need to use this for Rx checksum offload. It should not be necessary to
	* call this function to perform Tx offloads on outgoing traffic.
	*/
	enum udp_parsable_tunnel_type {
	UDP_TUNNEL_TYPE_VXLAN = BIT(0), /* RFC 7348 */
	UDP_TUNNEL_TYPE_GENEVE = BIT(1), /* draft-ietf-nvo3-geneve */
	UDP_TUNNEL_TYPE_VXLAN_GPE = BIT(2), /* draft-ietf-nvo3-vxlan-gpe */
	};

	struct udp_tunnel_info {
	unsigned short type;
	sa_family_t sa_family;
	__be16 port;
	u8 hw_priv;
	};

	/* Notify network devices of offloadable types */
	void udp_tunnel_push_rx_port(struct net_device dev, struct socket sock,
	unsigned short type);
	void udp_tunnel_drop_rx_port(struct net_device dev, struct socket sock,
	unsigned short type);
	void udp_tunnel_notify_add_rx_port(struct socket *sock, unsigned short type);
	void udp_tunnel_notify_del_rx_port(struct socket *sock, unsigned short type);

	static inline void udp_tunnel_get_rx_info(struct net_device *dev)
	{
	ASSERT_RTNL();
	call_netdevice_notifiers(NETDEV_UDP_TUNNEL_PUSH_INFO, dev);
	}

	static inline void udp_tunnel_drop_rx_info(struct net_device *dev)
	{
	ASSERT_RTNL();
	call_netdevice_notifiers(NETDEV_UDP_TUNNEL_DROP_INFO, dev);
	}

	/* Transmit the skb using UDP encapsulation. */
	void udp_tunnel_xmit_skb(struct rtable rt, struct sock sk, struct sk_buff *skb,
	__be32 src, __be32 dst, __u8 tos, __u8 ttl,
	__be16 df, __be16 src_port, __be16 dst_port,
	bool xnet, bool nocheck);

	int udp_tunnel6_xmit_skb(struct dst_entry dst, struct sock sk,
	struct sk_buff *skb,
	struct net_device dev, struct in6_addr saddr,
	struct in6_addr *daddr,
	__u8 prio, __u8 ttl, __be32 label,
	__be16 src_port, __be16 dst_port, bool nocheck);

	void udp_tunnel_sock_release(struct socket *sock);

	struct metadata_dst udp_tun_rx_dst(struct sk_buff skb, unsigned short family,
	__be16 flags, __be64 tunnel_id,
	int md_size);

	#ifdef CONFIG_INET
	static inline int udp_tunnel_handle_offloads(struct sk_buff *skb, bool udp_csum)
	{
	int type = udp_csum ? SKB_GSO_UDP_TUNNEL_CSUM : SKB_GSO_UDP_TUNNEL;

	return iptunnel_handle_offloads(skb, type);
	}
	#endif

	static inline void udp_tunnel_encap_enable(struct socket *sock)
	{
	struct udp_sock *up = udp_sk(sock->sk);

	if (up->encap_enabled)
	return;

	up->encap_enabled = 1;
	#if IS_ENABLED(CONFIG_IPV6)
	if (sock->sk->sk_family == PF_INET6)
	ipv6_stub->udpv6_encap_enable();
	else
	#endif
	udp_encap_enable();
	}

	#define UDP_TUNNEL_NIC_MAX_TABLES 4

	enum udp_tunnel_nic_info_flags {
	/* Device callbacks may sleep */
	UDP_TUNNEL_NIC_INFO_MAY_SLEEP = BIT(0),
	/* Device only supports offloads when it's open, all ports
	* will be removed before close and re-added after open.
	*/
	UDP_TUNNEL_NIC_INFO_OPEN_ONLY = BIT(1),
	/* Device supports only IPv4 tunnels */
	UDP_TUNNEL_NIC_INFO_IPV4_ONLY = BIT(2),
	/* Device has hard-coded the IANA VXLAN port (4789) as VXLAN.
	* This port must not be counted towards n_entries of any table.
	* Driver will not receive any callback associated with port 4789.
	*/
	UDP_TUNNEL_NIC_INFO_STATIC_IANA_VXLAN = BIT(3),
	};

	struct udp_tunnel_nic;

	#define UDP_TUNNEL_NIC_MAX_SHARING_DEVICES (U16_MAX / 2)

	struct udp_tunnel_nic_shared {
	struct udp_tunnel_nic *udp_tunnel_nic_info;

	struct list_head devices;
	};

	struct udp_tunnel_nic_shared_node {
	struct net_device *dev;
	struct list_head list;
	};

	/**
	* struct udp_tunnel_nic_info - driver UDP tunnel offload information
	* @set_port: callback for adding a new port
	* @unset_port: callback for removing a port
	* @sync_table: callback for syncing the entire port table at once
	* @shared: reference to device global state (optional)
	* @flags: device flags from enum udp_tunnel_nic_info_flags
	* @tables: UDP port tables this device has
	* @tables.n_entries: number of entries in this table
	* @tables.tunnel_types: types of tunnels this table accepts
	*
	* Drivers are expected to provide either @set_port and @unset_port callbacks
	* or the @sync_table callback. Callbacks are invoked with rtnl lock held.
	*
	* Devices which (misguidedly) share the UDP tunnel port table across multiple
	* netdevs should allocate an instance of struct udp_tunnel_nic_shared and
	* point @shared at it.
	* There must never be more than %UDP_TUNNEL_NIC_MAX_SHARING_DEVICES devices
	* sharing a table.
	*
	* Known limitations:
	* - UDP tunnel port notifications are fundamentally best-effort -
	* it is likely the driver will both see skbs which use a UDP tunnel port,
	* while not being a tunneled skb, and tunnel skbs from other ports -
	* drivers should only use these ports for non-critical RX-side offloads,
	* e.g. the checksum offload;
	* - none of the devices care about the socket family at present, so we don't
	* track it. Please extend this code if you care.
	*/
	struct udp_tunnel_nic_info {
	/* one-by-one */
	int (set_port)(struct net_device dev,
	unsigned int table, unsigned int entry,
	struct udp_tunnel_info *ti);
	int (unset_port)(struct net_device dev,
	unsigned int table, unsigned int entry,
	struct udp_tunnel_info *ti);

	/* all at once */
	int (sync_table)(struct net_device dev, unsigned int table);

	struct udp_tunnel_nic_shared *shared;

	unsigned int flags;

	struct udp_tunnel_nic_table_info {
	unsigned int n_entries;
	unsigned int tunnel_types;
	} tables[UDP_TUNNEL_NIC_MAX_TABLES];
	};

	/* UDP tunnel module dependencies
	*
	* Tunnel drivers are expected to have a hard dependency on the udp_tunnel
	* module. NIC drivers are not, they just attach their
	* struct udp_tunnel_nic_info to the netdev and wait for callbacks to come.
	* Loading a tunnel driver will cause the udp_tunnel module to be loaded
	* and only then will all the required state structures be allocated.
	* Since we want a weak dependency from the drivers and the core to udp_tunnel
	* we call things through the following stubs.
	*/
	struct udp_tunnel_nic_ops {
	void (get_port)(struct net_device dev, unsigned int table,
	unsigned int idx, struct udp_tunnel_info *ti);
	void (set_port_priv)(struct net_device dev, unsigned int table,
	unsigned int idx, u8 priv);
	void (add_port)(struct net_device dev, struct udp_tunnel_info *ti);
	void (del_port)(struct net_device dev, struct udp_tunnel_info *ti);
	void (reset_ntf)(struct net_device dev);

	size_t (dump_size)(struct net_device dev, unsigned int table);
	int (dump_write)(struct net_device dev, unsigned int table,
	struct sk_buff *skb);
	};

	#ifdef CONFIG_INET
	extern const struct udp_tunnel_nic_ops *udp_tunnel_nic_ops;
	#else
	#define udp_tunnel_nic_ops ((struct udp_tunnel_nic_ops *)NULL)
	#endif

	static inline void
	udp_tunnel_nic_get_port(struct net_device *dev, unsigned int table,
	unsigned int idx, struct udp_tunnel_info *ti)
	{
	/* This helper is used from .sync_table, we indicate empty entries
	* by zero'ed @ti. Drivers which need to know the details of a port
	* when it gets deleted should use the .set_port / .unset_port
	* callbacks.
	* Zero out here, otherwise !CONFIG_INET causes uninitilized warnings.
	*/
	memset(ti, 0, sizeof(*ti));

	if (udp_tunnel_nic_ops)
	udp_tunnel_nic_ops->get_port(dev, table, idx, ti);
	}

	static inline void
	udp_tunnel_nic_set_port_priv(struct net_device *dev, unsigned int table,
	unsigned int idx, u8 priv)
	{
	if (udp_tunnel_nic_ops)
	udp_tunnel_nic_ops->set_port_priv(dev, table, idx, priv);
	}

	static inline void
	udp_tunnel_nic_add_port(struct net_device dev, struct udp_tunnel_info ti)
	{
	if (udp_tunnel_nic_ops)
	udp_tunnel_nic_ops->add_port(dev, ti);
	}

	static inline void
	udp_tunnel_nic_del_port(struct net_device dev, struct udp_tunnel_info ti)
	{
	if (udp_tunnel_nic_ops)
	udp_tunnel_nic_ops->del_port(dev, ti);
	}

	/**
	* udp_tunnel_nic_reset_ntf() - device-originating reset notification
	* @dev: network interface device structure
	*
	* Called by the driver to inform the core that the entire UDP tunnel port
	* state has been lost, usually due to device reset. Core will assume device
	* forgot all the ports and issue .set_port and .sync_table callbacks as
	* necessary.
	*
	* This function must be called with rtnl lock held, and will issue all
	* the callbacks before returning.
	*/
	static inline void udp_tunnel_nic_reset_ntf(struct net_device *dev)
	{
	if (udp_tunnel_nic_ops)
	udp_tunnel_nic_ops->reset_ntf(dev);
	}

	static inline size_t
	udp_tunnel_nic_dump_size(struct net_device *dev, unsigned int table)
	{
	if (!udp_tunnel_nic_ops)
	return 0;
	return udp_tunnel_nic_ops->dump_size(dev, table);
	}

	static inline int
	udp_tunnel_nic_dump_write(struct net_device *dev, unsigned int table,
	struct sk_buff *skb)
	{
	if (!udp_tunnel_nic_ops)
	return 0;
	return udp_tunnel_nic_ops->dump_write(dev, table, skb);
	}
	#endif