path: root/include/linux/skbuff.h

/*
 *	Definitions for the 'struct sk_buff' memory handlers.
 *
 *	Authors:
 *		Alan Cox, <gw4pts@gw4pts.ampr.org>
 *		Florian La Roche, <rzsfl@rz.uni-sb.de>
 *
 *	This program is free software; you can redistribute it and/or
 *	modify it under the terms of the GNU General Public License
 *	as published by the Free Software Foundation; either version
 *	2 of the License, or (at your option) any later version.
 */

#ifndef _LINUX_SKBUFF_H
#define _LINUX_SKBUFF_H

#include <linux/kernel.h>
#include <linux/kmemcheck.h>
#include <linux/compiler.h>
#include <linux/time.h>
#include <linux/bug.h>
#include <linux/cache.h>
#include <linux/rbtree.h>
#include <linux/socket.h>

#include <linux/atomic.h>
#include <asm/types.h>
#include <linux/spinlock.h>
#include <linux/net.h>
#include <linux/textsearch.h>
#include <net/checksum.h>
#include <linux/rcupdate.h>
#include <linux/hrtimer.h>
#include <linux/dma-mapping.h>
#include <linux/netdev_features.h>
#include <linux/sched.h>
#include <net/flow_dissector.h>
#include <linux/splice.h>

/* A. Checksumming of received packets by device.
 *
 * CHECKSUM_NONE:
 *
 *   Device failed to checksum this packet e.g. due to lack of capabilities.
 *   The packet contains full (though not verified) checksum in packet but
 *   not in skb->csum. Thus, skb->csum is undefined in this case.
 *
 * CHECKSUM_UNNECESSARY:
 *
 *   The hardware you're dealing with doesn't calculate the full checksum
 *   (as in CHECKSUM_COMPLETE), but it does parse headers and verify checksums
 *   for specific protocols. For such packets it will set CHECKSUM_UNNECESSARY
 *   if their checksums are okay. skb->csum is still undefined in this case
 *   though. It is a bad option, but, unfortunately, nowadays most vendors do
 *   this. Apparently with the secret goal to sell you new devices, when you
 *   will add new protocol to your host, f.e. IPv6 8)
 *
 *   CHECKSUM_UNNECESSARY is applicable to following protocols:
 *     TCP: IPv6 and IPv4.
 *     UDP: IPv4 and IPv6. A device may apply CHECKSUM_UNNECESSARY to a
 *       zero UDP checksum for either IPv4 or IPv6, the networking stack
 *       may perform further validation in this case.
 *     GRE: only if the checksum is present in the header.
 *     SCTP: indicates the CRC in SCTP header has been validated.
 *
 *   skb->csum_level indicates the number of consecutive checksums found in
 *   the packet minus one that have been verified as CHECKSUM_UNNECESSARY.
 *   For instance if a device receives an IPv6->UDP->GRE->IPv4->TCP packet
 *   and a device is able to verify the checksums for UDP (possibly zero),
 *   GRE (checksum flag is set), and TCP-- skb->csum_level would be set to
 *   two. If the device were only able to verify the UDP checksum and not
 *   GRE, either because it doesn't support GRE checksum of because GRE
 *   checksum is bad, skb->csum_level would be set to zero (TCP checksum is
 *   not considered in this case).
 *
 * CHECKSUM_COMPLETE:
 *
 *   This is the most generic way. The device supplied checksum of the _whole_
 *   packet as seen by netif_rx() and fills out in skb->csum. Meaning, the
 *   hardware doesn't need to parse L3/L4 headers to implement this.
 *
 *   Note: Even if device supports only some protocols, but is able to produce
 *   skb->csum, it MUST use CHECKSUM_COMPLETE, not CHECKSUM_UNNECESSARY.
 *
 * CHECKSUM_PARTIAL:
 *
 *   A checksum is set up to be offloaded to a device as described in the
 *   output description for CHECKSUM_PARTIAL. This may occur on a packet
 *   received directly from another Linux OS, e.g., a virtualized Linux kernel
 *   on the same host, or it may be set in the input path in GRO or remote
 *   checksum offload. For the purposes of checksum verification, the checksum
 *   referred to by skb->csum_start + skb->csum_offset and any preceding
 *   checksums in the packet are considered verified. Any checksums in the
 *   packet that are after the checksum being offloaded are not considered to
 *   be verified.
 *
 * B. Checksumming on output.
 *
 * CHECKSUM_NONE:
 *
 *   The skb was already checksummed by the protocol, or a checksum is not
 *   required.
 *
 * CHECKSUM_PARTIAL:
 *
 *   The device is required to checksum the packet as seen by hard_start_xmit()
 *   from skb->csum_start up to the end, and to record/write the checksum at
 *   offset skb->csum_start + skb->csum_offset.
 *
 *   The device must show its capabilities in dev->features, set up at device
 *   setup time, e.g. netdev_features.h:
 *
 *	NETIF_F_HW_CSUM	- It's a clever device, it's able to checksum everything.
 *	NETIF_F_IP_CSUM - Device is dumb, it's able to checksum only TCP/UDP over
 *			  IPv4. Sigh. Vendors like this way for an unknown reason.
 *			  Though, see comment above about CHECKSUM_UNNECESSARY. 8)
 *	NETIF_F_IPV6_CSUM - About as dumb as the last one but does IPv6 instead.
 *	NETIF_F_...     - Well, you get the picture.
 *
 * CHECKSUM_UNNECESSARY:
 *
 *   Normally, the device will do per protocol specific checksumming. Protocol
 *   implementations that do not want the NIC to perform the checksum
 *   calculation should use this flag in their outgoing skbs.
 *
 *	NETIF_F_FCOE_CRC - This indicates that the device can do FCoE FC CRC
 *			   offload. Correspondingly, the FCoE protocol driver
 *			   stack should use CHECKSUM_UNNECESSARY.
 *
 * Any questions? No questions, good.		--ANK
 */

/* Don't change this without changing skb_csum_unnecessary! */
#define CHECKSUM_NONE		0
#define CHECKSUM_UNNECESSARY	1
#define CHECKSUM_COMPLETE	2
#define CHECKSUM_PARTIAL	3

/* Maximum value in skb->csum_level */
#define SKB_MAX_CSUM_LEVEL	3

#define SKB_DATA_ALIGN(X)	ALIGN(X, SMP_CACHE_BYTES)
#define SKB_WITH_OVERHEAD(X)	\
	((X) - SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))
#define SKB_MAX_ORDER(X, ORDER) \
	SKB_WITH_OVERHEAD((PAGE_SIZE << (ORDER)) - (X))
#define SKB_MAX_HEAD(X)		(SKB_MAX_ORDER((X), 0))
#define SKB_MAX_ALLOC		(SKB_MAX_ORDER(0, 2))

/* return minimum truesize of one skb containing X bytes of data */
#define SKB_TRUESIZE(X) ((X) +						\
			 SKB_DATA_ALIGN(sizeof(struct sk_buff)) +	\
			 SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))

struct net_device;
struct scatterlist;
struct pipe_inode_info;
struct iov_iter;
struct napi_struct;

#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
struct nf_conntrack {
	atomic_t use;
};
#endif

#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
struct nf_bridge_info {
	atomic_t		use;
	enum {
		BRNF_PROTO_UNCHANGED,
		BRNF_PROTO_8021Q,
		BRNF_PROTO_PPPOE
	} orig_proto:8;
	bool			pkt_otherhost;
	unsigned int		mask;
	struct net_device	*physindev;
	union {
		struct net_device *physoutdev;
		char neigh_header[8];
	};
	__be32			ipv4_daddr;
};
#endif

struct sk_buff_head {
	/* These two members must be first. */
	struct sk_buff	*next;
	struct sk_buff	*prev;

	__u32		qlen;
	spinlock_t	lock;
};

struct sk_buff;

/* To allow 64K frame to be packed as single skb without frag_list we
 * require 64K/PAGE_SIZE pages plus 1 additional page to allow for
 * buffers which do not start on a page boundary.
 *
 * Since GRO uses frags we allocate at least 16 regardless of page
 * size.
 */
#if (65536/PAGE_SIZE + 1) < 16
#define MAX_SKB_FRAGS 16UL
#else
#define MAX_SKB_FRAGS (65536/PAGE_SIZE + 1)
#endif

typedef struct skb_frag_struct skb_frag_t;

struct skb_frag_struct {
	struct {
		struct page *p;
	} page;
#if (BITS_PER_LONG > 32) || (PAGE_SIZE >= 65536)
	__u32 page_offset;
	__u32 size;
#else
	__u16 page_offset;
	__u16 size;
#endif
};

static inline unsigned int skb_frag_size(const skb_frag_t *frag)
{
	return frag->size;
}

static inline void skb_frag_size_set(skb_frag_t *frag, unsigned int size)
{
	frag->size = size;
}

static inline void skb_frag_size_add(skb_frag_t *frag, int delta)
{
	frag->size += delta;
}

static inline void skb_frag_size_sub(skb_frag_t *frag, int delta)
{
	frag->size -= delta;
}

#define HAVE_HW_TIME_STAMP

/**
 * struct skb_shared_hwtstamps - hardware time stamps
 * @hwtstamp:	hardware time stamp transformed into duration
 *		since arbitrary point in time
 *
 * Software time stamps generated by ktime_get_real() are stored in
 * skb->tstamp.
 *
 * hwtstamps can only be compared against other hwtstamps from
 * the same device.
 *
 * This structure is attached to packets as part of the
 * &skb_shared_info. Use skb_hwtstamps() to get a pointer.
 */
struct skb_shared_hwtstamps {
	ktime_t	hwtstamp;
};

/* Definitions for tx_flags in struct skb_shared_info */
enum {
	/* generate hardware time stamp */
	SKBTX_HW_TSTAMP = 1 << 0,

	/* generate software time stamp when queueing packet to NIC */
	SKBTX_SW_TSTAMP = 1 << 1,

	/* device driver is going to provide hardware time stamp */
	SKBTX_IN_PROGRESS = 1 << 2,

	/* device driver supports TX zero-copy buffers */
	SKBTX_DEV_ZEROCOPY = 1 << 3,

	/* generate wifi status information (where possible) */
	SKBTX_WIFI_STATUS = 1 << 4,

	/* This indicates at least one fragment might be overwritten
	 * (as in vmsplice(), sendfile() ...)
	 * If we need to compute a TX checksum, we'll need to copy
	 * all frags to avoid possible bad checksum
	 */
	SKBTX_SHARED_FRAG = 1 << 5,

	/* generate software time stamp when entering packet scheduling */
	SKBTX_SCHED_TSTAMP = 1 << 6,

	/* generate software timestamp on peer data acknowledgment */
	SKBTX_ACK_TSTAMP = 1 << 7,
};

#define SKBTX_ANY_SW_TSTAMP	(SKBTX_SW_TSTAMP    | \
				 SKBTX_SCHED_TSTAMP | \
				 SKBTX_ACK_TSTAMP)
#define SKBTX_ANY_TSTAMP	(SKBTX_HW_TSTAMP | SKBTX_ANY_SW_TSTAMP)

/*
 * The callback notifies userspace to release buffers when skb DMA is done in
 * lower device, the skb last reference should be 0 when calling this.
 * The zerocopy_success argument is true if zero copy transmit occurred,
 * false on data copy or out of memory error caused by data copy attempt.
 * The ctx field is used to track device context.
 * The desc field is used to track userspace buffer index.
 */
struct ubuf_info {
	void (*callback)(struct ubuf_info *, bool zerocopy_success);
	void *ctx;
	unsigned long desc;
};

/* This data is invariant across clones and lives at
 * the end of the header data, ie. at skb->end.
 */
struct skb_shared_info {
	unsigned char	nr_frags;
	__u8		tx_flags;
	unsigned short	gso_size;
	/* Warning: this field is not always filled in (UFO)! */
	unsigned short	gso_segs;
	unsigned short  gso_type;
	struct sk_buff	*frag_list;
	struct skb_shared_hwtstamps hwtstamps;
	u32		tskey;
	__be32          ip6_frag_id;

	/*
	 * Warning : all fields before dataref are cleared in __alloc_skb()
	 */
	atomic_t	dataref;

	/* Intermediate layers must ensure that destructor_arg
	 * remains valid until skb destructor */
	void *		destructor_arg;

	/* must be last field, see pskb_expand_head() */
	skb_frag_t	frags[MAX_SKB_FRAGS];
};

/* We divide dataref into two halves.  The higher 16 bits hold references
 * to the payload part of skb->data.  The lower 16 bits hold references to
 * the entire skb->data.  A clone of a headerless skb holds the length of
 * the header in skb->hdr_len.
 *
 * All users must obey the rule that the skb->data reference count must be
 * greater than or equal to the payload reference count.
 *
 * Holding a reference to the payload part means that the user does not
 * care about modifications to the header part of skb->data.
 */
#define SKB_DATAREF_SHIFT 16
#define SKB_DATAREF_MASK ((1 << SKB_DATAREF_SHIFT) - 1)


enum {
	SKB_FCLONE_UNAVAILABLE,	/* skb has no fclone (from head_cache) */
	SKB_FCLONE_ORIG,	/* orig skb (from fclone_cache) */
	SKB_FCLONE_CLONE,	/* companion fclone skb (from fclone_cache) */
};

enum {
	SKB_GSO_TCPV4 = 1 << 0,
	SKB_GSO_UDP = 1 << 1,

	/* This indicates the skb is from an untrusted source. */
	SKB_GSO_DODGY = 1 << 2,

	/* This indicates the tcp segment has CWR set. */
	SKB_GSO_TCP_ECN = 1 << 3,

	SKB_GSO_TCPV6 = 1 << 4,

	SKB_GSO_FCOE = 1 << 5,

	SKB_GSO_GRE = 1 << 6,

	SKB_GSO_GRE_CSUM = 1 << 7,

	SKB_GSO_IPIP = 1 << 8,

	SKB_GSO_SIT = 1 << 9,

	SKB_GSO_UDP_TUNNEL = 1 << 10,

	SKB_GSO_UDP_TUNNEL_CSUM = 1 << 11,

	SKB_GSO_TUNNEL_REMCSUM = 1 << 12,
};

#if BITS_PER_LONG > 32
#define NET_SKBUFF_DATA_USES_OFFSET 1
#endif

#ifdef NET_SKBUFF_DATA_USES_OFFSET
typedef unsigned int sk_buff_data_t;
#else
typedef unsigned char *sk_buff_data_t;
#endif

/**
 * struct skb_mstamp - multi resolution time stamps
 * @stamp_us: timestamp in us resolution
 * @stamp_jiffies: timestamp in jiffies
 */
struct skb_mstamp {
	union {
		u64		v64;
		struct {
			u32	stamp_us;
			u32	stamp_jiffies;
		};
	};
};

/**
 * skb_mstamp_get - get current timestamp
 * @cl: place to store timestamps
 */
static inline void skb_mstamp_get(struct skb_mstamp *cl)
{
	u64 val = local_clock();

	do_div(val, NSEC_PER_USEC);
	cl->stamp_us = (u32)val;
	cl->stamp_jiffies = (u32)jiffies;
}

/**
 * skb_mstamp_delta - compute the difference in usec between two skb_mstamp
 * @t1: pointer to newest sample
 * @t0: pointer to oldest sample
 */
static inline u32 skb_mstamp_us_delta(const struct skb_mstamp *t1,
				      const struct skb_mstamp *t0)
{
	s32 delta_us = t1->stamp_us - t0->stamp_us;
	u32 delta_jiffies = t1->stamp_jiffies - t0->stamp_jiffies;

	/* If delta_us is negative, this might be because interval is too big,
	 * or local_clock() drift is too big : fallback using jiffies.
	 */
	if (delta_us <= 0 ||
	    delta_jiffies >= (INT_MAX / (USEC_PER_SEC / HZ)))

		delta_us = jiffies_to_usecs(delta_jiffies);

	return delta_us;
}


/** 
 *	struct sk_buff - socket buffer
 *	@next: Next buffer in list
 *	@prev: Previous buffer in list
 *	@tstamp: Time we arrived/left
 *	@rbnode: RB tree node, alternative to next/prev for netem/tcp
 *	@sk: Socket we are owned by
 *	@dev: Device we arrived on/are leaving by
 *	@cb: Control buffer. Free for use by every layer. Put private vars here
 *	@_skb_refdst: destination entry (with norefcount bit)
 *	@sp: the security path, used for xfrm
 *	@len: Length of actual data
 *	@data_len: Data length
 *	@mac_len: Length of link layer header
 *	@hdr_len: writable header length of cloned skb
 *	@csum: Checksum (must include start/offset pair)
 *	@csum_start: Offset from skb->head where checksumming should start
 *	@csum_offset: Offset from csum_start where checksum should be stored
 *	@priority: Packet queueing priority
 *	@ignore_df: allow local fragmentation
 *	@cloned: Head may be cloned (check refcnt to be sure)
 *	@ip_summed: Driver fed us an IP checksum
 *	@nohdr: Payload reference only, must not modify header
 *	@nfctinfo: Relationship of this skb to the connection
 *	@pkt_type: Packet class
 *	@fclone: skbuff clone status
 *	@ipvs_property: skbuff is owned by ipvs
 *	@peeked: this packet has been seen already, so stats have been
 *		done for it, don't do them again
 *	@nf_trace: netfilter packet trace flag
 *	@protocol: Packet protocol from driver
 *	@destructor: Destruct function
 *	@nfct: Associated connection, if any
 *	@nf_bridge: Saved data about a bridged frame - see br_netfilter.c
 *	@skb_iif: ifindex of device we arrived on
 *	@tc_index: Traffic control index
 *	@tc_verd: traffic control verdict
 *	@hash: the packet hash
 *	@queue_mapping: Queue mapping for multiqueue devices
 *	@xmit_more: More SKBs are pending for this queue
 *	@ndisc_nodetype: router type (from link layer)
 *	@ooo_okay: allow the mapping of a socket to a queue to be changed
 *	@l4_hash: indicate hash is a canonical 4-tuple hash over transport
 *		ports.
 *	@sw_hash: indicates hash was computed in software stack
 *	@wifi_acked_valid: wifi_acked was set
 *	@wifi_acked: whether frame was acked on wifi or not
 *	@no_fcs:  Request NIC to treat last 4 bytes as Ethernet FCS
  *	@napi_id: id of the NAPI struct this skb came from
 *	@secmark: security marking
 *	@mark: Generic packet mark
 *	@vlan_proto: vlan encapsulation protocol
 *	@vlan_tci: vlan tag control information
 *	@inner_protocol: Protocol (encapsulation)
 *	@inner_transport_header: Inner transport layer header (encapsulation)
 *	@inner_network_header: Network layer header (encapsulation)
 *	@inner_mac_header: Link layer header (encapsulation)
 *	@transport_header: Transport layer header
 *	@network_header: Network layer header
 *	@mac_header: Link layer header
 *	@tail: Tail pointer
 *	@end: End pointer
 *	@head: Head of buffer
 *	@data: Data head pointer
 *	@truesize: Buffer size
 *	@users: User count - see {datagram,tcp}.c
 */

struct sk_buff {
	union {
		struct {
			/* These two members must be first. */
			struct sk_buff		*next;
			struct sk_buff		*prev;

			union {
				ktime_t		tstamp;
				struct skb_mstamp skb_mstamp;
			};
		};
		struct rb_node	rbnode; /* used in netem & tcp stack */
	};
	struct sock		*sk;
	struct net_device	*dev;

	/*
	 * This is the control buffer. It is free to use for every
	 * layer. Please put your private variables there. If you
	 * want to keep them across layers you have to do a skb_clone()
	 * first. This is owned by whoever has the skb queued ATM.
	 */
	char			cb[48] __aligned(8);

	unsigned long		_skb_refdst;
	void			(*destructor)(struct sk_buff *skb);
#ifdef CONFIG_XFRM
	struct	sec_path	*sp;
#endif
#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
	struct nf_conntrack	*nfct;
#endif
#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
	struct nf_bridge_info	*nf_bridge;
#endif
	unsigned int		len,
				data_len;
	__u16			mac_len,
				hdr_len;

	/* Following fields are _not_ copied in __copy_skb_header()
	 * Note that queue_mapping is here mostly to fill a hole.
	 */
	kmemcheck_bitfield_begin(flags1);
	__u16			queue_mapping;
	__u8			cloned:1,
				nohdr:1,
				fclone:2,
				peeked:1,
				head_frag:1,
				xmit_more:1;
	/* one bit hole */
	kmemcheck_bitfield_end(flags1);

	/* fields enclosed in headers_start/headers_end are copied
	 * using a single memcpy() in __copy_skb_header()
	 */
	/* private: */
	__u32			headers_start[0];
	/* public: */

/* if you move pkt_type around you also must adapt those constants */
#ifdef __BIG_ENDIAN_BITFIELD
#define PKT_TYPE_MAX	(7 << 5)
#else
#define PKT_TYPE_MAX	7
#endif
#define PKT_TYPE_OFFSET()	offsetof(struct sk_buff, __pkt_type_offset)

	__u8			__pkt_type_offset[0];
	__u8			pkt_type:3;
	__u8			pfmemalloc:1;
	__u8			ignore_df:1;
	__u8			nfctinfo:3;

	__u8			nf_trace:1;
	__u8			ip_summed:2;
	__u8			ooo_okay:1;
	__u8			l4_hash:1;
	__u8			sw_hash:1;
	__u8			wifi_acked_valid:1;
	__u8			wifi_acked:1;

	__u8			no_fcs:1;
	/* Indicates the inner headers are valid in the skbuff. */
	__u8			encapsulation:1;
	__u8			encap_hdr_csum:1;
	__u8			csum_valid:1;
	__u8			csum_complete_sw:1;
	__u8			csum_level:2;
	__u8			csum_bad:1;

#ifdef CONFIG_IPV6_NDISC_NODETYPE
	__u8			ndisc_nodetype:2;
#endif
	__u8			ipvs_property:1;
	__u8			inner_protocol_type:1;
	__u8			remcsum_offload:1;
	/* 3 or 5 bit hole */

#ifdef CONFIG_NET_SCHED
	__u16			tc_index;	/* traffic control index */
#ifdef CONFIG_NET_CLS_ACT
	__u16			tc_verd;	/* traffic control verdict */
#endif
#endif

	union {
		__wsum		csum;
		struct {
			__u16	csum_start;
			__u16	csum_offset;
		};
	};
	__u32			priority;
	int			skb_iif;
	__u32			hash;
	__be16			vlan_proto;
	__u16			vlan_tci;
#if defined(CONFIG_NET_RX_BUSY_POLL) || defined(CONFIG_XPS)
	union {
		unsigned int	napi_id;
		unsigned int	sender_cpu;
	};
#endif
#ifdef CONFIG_NETWORK_SECMARK
	__u32			secmark;
#endif
	union {
		__u32		mark;
		__u32		reserved_tailroom;
	};

	union {
		__be16		inner_protocol;
		__u8		inner_ipproto;
	};

	__u16			inner_transport_header;
	__u16			inner_network_header;
	__u16			inner_mac_header;

	__be16			protocol;
	__u16			transport_header;
	__u16			network_header;
	__u16			mac_header;

	/* private: */
	__u32			headers_end[0];
	/* public: */

	/* These elements must be at the end, see alloc_skb() for details.  */
	sk_buff_data_t		tail;
	sk_buff_data_t		end;
	unsigned char		*head,
				*data;
	unsigned int		truesize;
	atomic_t		users;
};

#ifdef __KERNEL__
/*
 *	Handling routines are only of interest to the kernel
 */
#include <linux/slab.h>


#define SKB_ALLOC_FCLONE	0x01
#define SKB_ALLOC_RX		0x02
#define SKB_ALLOC_NAPI		0x04

/* Returns true if the skb was allocated from PFMEMALLOC reserves */
static inline bool skb_pfmemalloc(const struct sk_buff *skb)
{
	return unlikely(skb->pfmemalloc);
}

/*
 * skb might have a dst pointer attached, refcounted or not.
 * _skb_refdst low order bit is set if refcount was _not_ taken
 */
#define SKB_DST_NOREF	1UL
#define SKB_DST_PTRMASK	~(SKB_DST_NOREF)

/**
 * skb_dst - returns skb dst_entry
 * @skb: buffer
 *
 * Returns skb dst_entry, regardless of reference taken or not.
 */
static inline struct dst_entry *skb_dst(const struct sk_buff *skb)
{
	/* If refdst was not refcounted, check we still are in a 
	 * rcu_read_lock section
	 */
	WARN_ON((skb->_skb_refdst & SKB_DST_NOREF) &&
		!rcu_read_lock_held() &&
		!rcu_read_lock_bh_held());
	return (struct dst_entry *)(skb->_skb_refdst & SKB_DST_PTRMASK);
}

/**
 * skb_dst_set - sets skb dst
 * @skb: buffer
 * @dst: dst entry
 *
 * Sets skb dst, assuming a reference was taken on dst and should
 * be released by skb_dst_drop()
 */
static inline void skb_dst_set(struct sk_buff *skb, struct dst_entry *dst)
{
	skb->_skb_refdst = (unsigned long)dst;
}

/**
 * skb_dst_set_noref - sets skb dst, hopefully, without taking reference
 * @skb: buffer
 * @dst: dst entry
 *
 * Sets skb dst, assuming a reference was not taken on dst.
 * If dst entry is cached, we do not take reference and dst_release
 * will be avoided by refdst_drop. If dst entry is not cached, we take
 * reference, so that last dst_release can destroy the dst immediately.
 */
static inline void skb_dst_set_noref(struct sk_buff *skb, struct dst_entry *dst)
{
	WARN_ON(!rcu_read_lock_held() && !rcu_read_lock_bh_held());
	skb->_skb_refdst = (unsigned long)dst | SKB_DST_NOREF;
}

/**
 * skb_dst_is_noref - Test if skb dst isn't refcounted
 * @skb: buffer
 */
static inline bool skb_dst_is_noref(const struct sk_buff *skb)
{
	return (skb->_skb_refdst & SKB_DST_NOREF) && skb_dst(skb);
}

static inline struct rtable *skb_rtable(const struct sk_buff *skb)
{
	return (struct rtable *)skb_dst(skb);
}

void kfree_skb(struct sk_buff *skb);
void kfree_skb_list(struct sk_buff *segs);
void skb_tx_error(struct sk_buff *skb);
void consume_skb(struct sk_buff *skb);
void  __kfree_skb(struct sk_buff *skb);
extern struct kmem_cache *skbuff_head_cache;

void kfree_skb_partial(struct sk_buff *skb, bool head_stolen);
bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from,
		      bool *fragstolen, int *delta_truesize);

struct sk_buff *__alloc_skb(unsigned int size, gfp_t priority, int flags,
			    int node);
struct sk_buff *__build_skb(void *data, unsigned int frag_size);
struct sk_buff *build_skb(void *data, unsigned int frag_size);
static inline struct sk_buff *alloc_skb(unsigned int size,
					gfp_t priority)
{
	return __alloc_skb(size, priority, 0, NUMA_NO_NODE);
}

struct sk_buff *alloc_skb_with_frags(unsigned long header_len,
				     unsigned long data_len,
				     int max_page_order,
				     int *errcode,
				     gfp_t gfp_mask);

/* Layout of fast clones : [skb1][skb2][fclone_ref] */
struct sk_buff_fclones {
	struct sk_buff	skb1;

	struct sk_buff	skb2;

	atomic_t	fclone_ref;
};

/**
 *	skb_fclone_busy - check if fclone is busy
 *	@skb: buffer
 *
 * Returns true is skb is a fast clone, and its clone is not freed.
 * Some drivers call skb_orphan() in their ndo_start_xmit(),
 * so we also check that this didnt happen.
 */
static inline bool skb_fclone_busy(const struct sock *sk,
				   const struct sk_buff *skb)
{
	const struct sk_buff_fclones *fclones;

	fclones = container_of(skb, struct sk_buff_fclones, skb1);

	return skb->fclone == SKB_FCLONE_ORIG &&
	       atomic_read(&fclones->fclone_ref) > 1 &&
	       fclones->skb2.sk == sk;
}

static inline struct sk_buff *alloc_skb_fclone(unsigned int size,
					       gfp_t priority)
{
	return __alloc_skb(size, priority, SKB_ALLOC_FCLONE, NUMA_NO_NODE);
}

struct sk_buff *__alloc_skb_head(gfp_t priority, int node);
static inline struct sk_buff *alloc_skb_head(gfp_t priority)
{
	return __alloc_skb_head(priority, -1);
}

struct sk_buff *skb_morph(struct sk_buff *dst, struct sk_buff *src);
int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask);
struct sk_buff *skb_clone(struct sk_buff *skb, gfp_t priority);
struct sk_buff *skb_copy(const struct sk_buff *skb, gfp_t priority);
struct sk_buff *__pskb_copy_fclone(struct sk_buff *skb, int headroom,
				   gfp_t gfp_mask, bool fclone);
static inline struct sk_buff *__pskb_copy(struct sk_buff *skb, int headroom,
					  gfp_t gfp_mask)
{
	return __pskb_copy_fclone(skb, headroom, gfp_mask, false);
}

int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail, gfp_t gfp_mask);
struct sk_buff *skb_realloc_headroom(struct sk_buff *skb,
				     unsigned int headroom);
struct sk_buff *skb_copy_expand(const struct sk_buff *skb, int newheadroom,
				int newtailroom, gfp_t priority);
int skb_to_sgvec_nomark(struct sk_buff *skb, struct scatterlist *sg,
			int offset, int len);
int skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset,
		 int len);
int skb_cow_data(struct sk_buff *skb, int tailbits, struct sk_buff **trailer);
int skb_pad(struct sk_buff *skb, int pad);
#define dev_kfree_skb(a)	consume_skb(a)

int skb_append_datato_frags(struct sock *sk, struct sk_buff *skb,
			    int getfrag(void *from, char *to, int offset,
					int len, int odd, struct sk_buff *skb),
			    void *from, int length);

int skb_append_pagefrags(struct sk_buff *skb, struct page *page,
			 int offset, size_t size);

struct skb_seq_state {
	__u32		lower_offset;
	__u32		upper_offset;
	__u32		frag_idx;
	__u32		stepped_offset;
	struct sk_buff	*root_skb;
	struct sk_buff	*cur_skb;
	__u8		*frag_data;
};

void skb_prepare_seq_read(struct sk_buff *skb, unsigned int from,
			  unsigned int to, struct skb_seq_state *st);
unsigned int skb_seq_read(unsigned int consumed, const u8 **data,
			  struct skb_seq_state *st);
void skb_abort_seq_read(struct skb_seq_state *st);

unsigned int skb_find_text(struct sk_buff *skb, unsigned int from,
			   unsigned int to, struct ts_config *config);

/*
 * Packet hash types specify the type of hash in skb_set_hash.
 *
 * Hash types refer to the protocol layer addresses which are used to
 * construct a packet's hash. The hashes are used to differentiate or identify
 * flows of the protocol layer for the hash type. Hash types are either
 * layer-2 (L2), layer-3 (L3), or layer-4 (L4).
 *
 * Properties of hashes:
 *
 * 1) Two packets in different flows have different hash values
 * 2) Two packets in the same flow should have the same hash value
 *
 * A hash at a higher layer is considered to be more specific. A driver should
 * set the most specific hash possible.
 *
 * A driver cannot indicate a more specific hash than the layer at which a hash
 * was computed. For instance an L3 hash cannot be set as an L4 hash.
 *
 * A driver may indicate a hash level which is less specific than the
 * actual layer the hash was computed on. For instance, a hash computed
 * at L4 may be considered an L3 hash. This should only be done if the
 * driver can't unambiguously determine that the HW computed the hash at
 * the higher layer. Note that the "should" in the second property above
 * permits this.
 */
enum pkt_hash_types {
	PKT_HASH_TYPE_NONE,	/* Undefined type */
	PKT_HASH_TYPE_L2,	/* Input: src_MAC, dest_MAC */
	PKT_HASH_TYPE_L3,	/* Input: src_IP, dst_IP */
	PKT_HASH_TYPE_L4,	/* Input: src_IP, dst_IP, src_port, dst_port */
};

static inline void
skb_set_hash(struct sk_buff *skb, __u32 hash, enum pkt_hash_types type)
{
	skb->l4_hash = (type == PKT_HASH_TYPE_L4);
	skb->sw_hash = 0;
	skb->hash = hash;
}

static inline __u32 skb_get_hash(struct sk_buff *skb)
{
	if (!skb->l4_hash && !skb->sw_hash)
		__skb_get_hash(skb);

	return skb->hash;
}

__u32 skb_get_hash_perturb(const struct sk_buff *skb, u32 perturb);

static inline __u32 skb_get_hash_raw(const struct sk_buff *skb)
{
	return skb->hash;
}

static inline void skb_clear_hash(struct sk_buff *skb)
{
	skb->hash = 0;
	skb->sw_hash = 0;
	skb->l4_hash = 0;
}

static inline void skb_clear_hash_if_not_l4(struct sk_buff *skb)
{
	if (!skb->l4_hash)
		skb_clear_hash(skb);
}

static inline void skb_copy_hash(struct sk_buff *to, const struct sk_buff *from)
{
	to->hash = from->hash;
	to->sw_hash = from->sw_hash;
	to->l4_hash = from->l4_hash;
};

static inline void skb_sender_cpu_clear(struct sk_buff *skb)
{
#ifdef CONFIG_XPS
	skb->sender_cpu = 0;
#endif
}

#ifdef NET_SKBUFF_DATA_USES_OFFSET
static inline unsigned char *skb_end_pointer(const struct sk_buff *skb)
{
	return skb->head + skb->end;
}

static inline unsigned int skb_end_offset(const struct sk_buff *skb)
{
	return skb->end;
}
#else
static inline unsigned char *skb_end_pointer(const struct sk_buff *skb)
{
	return skb->end;
}

static inline unsigned int skb_end_offset(const struct sk_buff *skb)
{
	return skb->end - skb->head;
}
#endif

/* Internal */
#define skb_shinfo(SKB)	((struct skb_shared_info *)(skb_end_pointer(SKB)))

static inline struct skb_shared_hwtstamps *skb_hwtstamps(struct sk_buff *skb)
{
	return &skb_shinfo(skb)->hwtstamps;
}

/**
 *	skb_queue_empty - check if a queue is empty
 *	@list: queue head
 *
 *	Returns true if the queue is empty, false otherwise.
 */
static inline int skb_queue_empty(const struct sk_buff_head *list)
{
	return list->next == (const struct sk_buff *) list;
}

/**
 *	skb_queue_is_last - check if skb is the last entry in the queue
 *	@list: queue head
 *	@skb: buffer
 *
 *	Returns true if @skb is the last buffer on the list.
 */
static inline bool skb_queue_is_last(const struct sk_buff_head *list,
				     const struct sk_buff *skb)
{
	return skb->next == (const struct sk_buff *) list;
}

/**
 *	skb_queue_is_first - check if skb is the first entry in the queue
 *	@list: queue head
 *	@skb: buffer
 *
 *	Returns true if @skb is the first buffer on the list.
 */
static inline bool skb_queue_is_first(const struct sk_buff_head *list,
				      const struct sk_buff *skb)
{
	return skb->prev == (const struct sk_buff *) list;
}

/**
 *	skb_queue_next - return the next packet in the queue
 *	@list: queue head
 *	@skb: current buffer
 *
 *	Return the next packet in @list after @skb.  It is only valid to
 *	call this if skb_queue_is_last() evaluates to false.
 */
static inline struct sk_buff *skb_queue_next(const struct sk_buff_head *list,
					     const struct sk_buff *skb)
{
	/* This BUG_ON may seem severe, but if we just return then we
	 * are going to dereference garbage.
	 */
	BUG_ON(skb_queue_is_last(list, skb));
	return skb->next;
}

/**
 *	skb_queue_prev - return the prev packet in the queue
 *	@list: queue head
 *	@skb: current buffer
 *
 *	Return the prev packet in @list before @skb.  It is only valid to
 *	call this if skb_queue_is_first() evaluates to false.
 */
static inline struct sk_buff *skb_queue_prev(const struct sk_buff_head *list,
					     const struct sk_buff *skb)
{
	/* This BUG_ON may seem severe, but if we just return then we
	 * are going to dereference garbage.
	 */
	BUG_ON(skb_queue_is_first(list, skb));
	return skb->prev;
}

/**
 *	skb_get - reference buffer
 *	@skb: buffer to reference
 *
 *	Makes another reference to a socket buffer and returns a pointer
 *	to the buffer.
 */
static inline struct sk_buff *skb_get(struct sk_buff *skb)
{
	atomic_inc(&skb->users);
	return skb;
}

/*
 * If users == 1, we are the only owner and are can avoid redundant
 * atomic change.
 */

/**
 *	skb_cloned - is the buffer a clone
 *	@skb: buffer to check
 *
 *	Returns true if the buffer was generated with skb_clone() and is
 *	one of multiple shared copies of the buffer. Cloned buffers are
 *	shared data so must not be written to under normal circumstances.
 */
static inline int skb_cloned(const struct sk_buff *skb)
{
	return skb->cloned &&
	       (atomic_read(&skb_shinfo(skb)->dataref) & SKB_DATAREF_MASK) != 1;
}

static inline int skb_unclone(struct sk_buff *skb, gfp_t pri)
{
	might_sleep_if(pri & __GFP_WAIT);

	if (skb_cloned(skb))
		return pskb_expand_head(skb, 0, 0, pri);

	return 0;
}

/**
 *	skb_header_cloned - is the header a clone
 *	@skb: buffer to check
 *
 *	Returns true if modifying the header part of the buffer requires
 *	the data to be copied.
 */
static inline int skb_header_cloned(const struct sk_buff *skb)
{
	int dataref;

	if (!skb->cloned)
		return 0;

	dataref = atomic_read(&skb_shinfo(skb)->dataref);
	dataref = (dataref & SKB_DATAREF_MASK) - (dataref >> SKB_DATAREF_SHIFT);
	return dataref != 1;
}

/**
 *	skb_header_release - release reference to header
 *	@skb: buffer to operate on
 *
 *	Drop a reference to the header part of the buffer.  This is done
 *	by acquiring a payload reference.  You must not read from the header
 *	part of skb->data after this.
 *	Note : Check if you can use __skb_header_release() instead.
 */
static inline void skb_header_release(struct sk_buff *skb)
{
	BUG_ON(skb->nohdr);
	skb->nohdr = 1;
	atomic_add(1 << SKB_DATAREF_SHIFT, &skb_shinfo(skb)->dataref);
}

/**
 *	__skb_header_release - release reference to header
 *	@skb: buffer to operate on
 *
 *	Variant of skb_header_release() assuming skb is private to caller.
 *	We can avoid one atomic operation.
 */
static inline void __skb_header_release(struct sk_buff *skb)
{
	skb->nohdr = 1;
	atomic_set(&skb_shinfo(skb)->dataref, 1 + (1 << SKB_DATAREF_SHIFT));
}


/**
 *	skb_shared - is the buffer shared
 *	@skb: buffer to check
 *
 *	Returns true if more than one person has a reference to this
 *	buffer.
 */
static inline int skb_shared(const struct sk_buff *skb)
{
	return atomic_read(&skb->users) != 1;
}

/**
 *	skb_share_check - check if buffer is shared and if so clone it
 *	@skb: buffer to check
 *	@pri: priority for memory allocation
 *
 *	If the buffer is shared the buffer is cloned and the old copy
 *	drops a reference. A new clone with a single reference is returned.
 *	If the buffer is not shared the original buffer is returned. When
 *	being called from interrupt status or with spinlocks held pri must
 *	be GFP_ATOMIC.
 *
 *	NULL is returned on a memory allocation failure.
 */
static inline struct sk_buff *skb_share_check(struct sk_buff *skb, gfp_t pri)
{
	might_sleep_if(pri & __GFP_WAIT);
	if (skb_shared(skb)) {
		struct sk_buff *nskb = skb_clone(skb, pri);

		if (likely(nskb))
			consume_skb(skb);
		else
			kfree_skb(skb);
		skb = nskb;
	}
	return skb;
}

/*
 *	Copy shared buffers into a new sk_buff. We effectively do COW on
 *	packets to handle cases where we have a local reader and forward
 *	and a couple of other messy ones. The normal one is tcpdumping
 *	a packet thats being forwarded.
 */

/**
 *	skb_unshare - make a copy of a shared buffer
 *	@skb: buffer to check
 *	@pri: priority for memory allocation
 *
 *	If the socket buffer is a clone then this function creates a new
 *	copy of the data, drops a reference count on the old copy and returns
 *	the new copy with the reference count at 1. If the buffer is not a clone
 *	the original buffer is returned. When called with a spinlock held or
 *	from interrupt state @pri must be %GFP_ATOMIC
 *
 *	%NULL is returned on a memory allocation failure.
 */
static inline struct sk_buff *skb_unshare(struct sk_buff *skb,
					  gfp_t pri)
{
	might_sleep_if(pri & __GFP_WAIT);
	if (skb_cloned(skb)) {
		struct sk_buff *nskb = skb_copy(skb, pri);

		/* Free our shared copy */
		if (likely(nskb))
			consume_skb(skb);
		else
			kfree_skb(skb);
		skb = nskb;
	}
	return skb;
}

/**
 *	skb_peek - peek at the head of an &sk_buff_head
 *	@list_: list to peek at
 *
 *	Peek an &sk_buff. Unlike most other operations you _MUST_
 *	be careful with this one. A peek leaves the buffer on the
 *	list and someone else may run off with it. You must hold
 *	the appropriate locks or have a private queue to do this.
 *
 *	Returns %NULL for an empty list or a pointer to the head element.
 *	The reference count is not incremented and the reference is therefore
 *	volatile. Use with caution.
 */
static inline struct sk_buff *skb_peek(const struct sk_buff_head *list_)
{
	struct sk_buff *skb = list_->next;

	if (skb == (struct sk_buff *)list_)
		skb = NULL;
	return skb;
}

/**
 *	skb_peek_next - peek skb following the given one from a queue
 *	@skb: skb to start from
 *	@list_: list to peek at
 *
 *	Returns %NULL when the end of the list is met or a pointer to the
 *	next element. The reference count is not incremented and the
 *	reference is therefore volatile. Use with caution.
 */
static inline struct sk_buff *skb_peek_next(struct sk_buff *skb,
		const struct sk_buff_head *list_)
{
	struct sk_buff *next = skb->next;

	if (next == (struct sk_buff *)list_)
		next = NULL;
	return next;
}

/**
 *	skb_peek_tail - peek at the tail of an &sk_buff_head
 *	@list_: list to peek at
 *
 *	Peek an &sk_buff. Unlike most other operations you _MUST_
 *	be careful with this one. A peek leaves the buffer on the
 *	list and someone else may run off with it. You must hold
 *	the appropriate locks or have a private queue to do this.
 *
 *	Returns %NULL for an empty list or a pointer to the tail element.
 *	The reference count is not incremented and the reference is therefore
 *	volatile. Use with caution.
 */
static inline struct sk_buff *skb_peek_tail(const struct sk_buff_head *list_)
{
	struct sk_buff *skb = list_->prev;

	if (skb == (struct sk_buff *)list_)
		skb = NULL;
	return skb;

}

/**
 *	skb_queue_len	- get queue length
 *	@list_: list to measure
 *
 *	Return the length of an &sk_buff queue.
 */
static inline __u32 skb_queue_len(const struct sk_buff_head *list_)
{
	return list_->qlen;
}

/**
 *	__skb_queue_head_init - initialize non-spinlock portions of sk_buff_head
 *	@list: queue to initialize
 *
 *	This initializes only the list and queue length aspects of
 *	an sk_buff_head object.  This allows to initialize the list
 *	aspects of an sk_buff_head without reinitializing things like
 *	the spinlock.  It can also be used for on-stack sk_buff_head
 *	objects where the spinlock is known to not be used.
 */
static inline void __skb_queue_head_init(struct sk_buff_head *list)
{
	list->prev = list->next = (struct sk_buff *)list;
	list->qlen = 0;
}

/*
 * This function creates a split out lock class for each invocation;
 * this is needed for now since a whole lot of users of the skb-queue
 * infrastructure in drivers have different locking usage (in hardirq)
 * than the networking core (in softirq only). In the long run either the
 * network layer or drivers should need annotation to consolidate the
 * main types of usage into 3 classes.
 */
static inline void skb_queue_head_init(struct sk_buff_head *list)
{
	spin_lock_init(&list->lock);
	__skb_queue_head_init(list);
}

static inline void skb_queue_head_init_class(struct sk_buff_head *list,
		struct lock_class_key *class)
{
	skb_queue_head_init(list);
	lockdep_set_class(&list->lock, class);
}

/*
 *	Insert an sk_buff on a list.
 *
 *	The "__skb_xxxx()" functions are the non-atomic ones that
 *	can only be called with interrupts disabled.
 */
void skb_insert(struct sk_buff *old, struct sk_buff *newsk,
		struct sk_buff_head *list);
static inline void __skb_insert(struct sk_buff *newsk,
				struct sk_buff *prev, struct sk_buff *next,
				struct sk_buff_head *list)
{
	newsk->next = next;
	newsk->prev = prev;
	next->prev  = prev->next = newsk;
	list->qlen++;
}

static inline void __skb_queue_splice(const struct sk_buff_head *list,
				      struct sk_buff *prev,
				      struct sk_buff *next)
{
	struct sk_buff *first = list->next;
	struct sk_buff *last = list->prev;

	first->prev = prev;
	prev->next = first;

	last->next = next;
	next->prev = last;
}

/**
 *	skb_queue_splice - join two skb lists, this is designed for stacks
 *	@list: the new list to add
 *	@head: the place to add it in the first list
 */
static inline void skb_queue_splice(const struct sk_buff_head *list,
				    struct sk_buff_head *head)
{
	if (!skb_queue_empty(list)) {
		__skb_queue_splice(list, (struct sk_buff *) head, head->next);
		head->qlen += list->qlen;
	}
}

/**
 *	skb_queue_splice_init - join two skb lists and reinitialise the emptied list
 *	@list: the new list to add
 *	@head: the place to add it in the first list
 *
 *	The list at @list is reinitialised
 */
static inline void skb_queue_splice_init(struct sk_buff_head *list,
					 struct sk_buff_head *head)
{
	if (!skb_queue_empty(list)) {
		__skb_queue_splice(list, (struct sk_buff *) head, head->next);
		head->qlen += list->qlen;
		__skb_queue_head_init(list);
	}
}

/**
 *	skb_queue_splice_tail - join two skb lists, each list being a queue
 *	@list: the new list to add
 *	@head: the place to add it in the first list
 */
static inline void skb_queue_splice_tail(const struct sk_buff_head *list,
					 struct sk_buff_head *head)
{
	if (!skb_queue_empty(list)) {
		__skb_queue_splice(list, head->prev, (struct sk_buff *) head);
		head->qlen += list->qlen;
	}
}

/**
 *	skb_queue_splice_tail_init - join two skb lists and reinitialise the emptied list
 *	@list: the new list to add
 *	@head: the place to add it in the first list
 *
 *	Each of the lists is a queue.
 *	The list at @list is reinitialised
 */
static inline void skb_queue_splice_tail_init(struct sk_buff_head *list,
					      struct sk_buff_head *head)
{
	if (!skb_queue_empty(list)) {
		__skb_queue_splice(list, head->prev, (struct sk_buff *) head);
		head->qlen += list->qlen;
		__skb_queue_head_init(list);
	}
}

/**
 *	__skb_queue_after - queue a buffer at the list head
 *	@list: list to use
 *	@prev: place after this buffer
 *	@newsk: buffer to queue
 *
 *	Queue a buffer int the middle of a list. This function takes no locks
 *	and you must therefore hold required locks before calling it.
 *
 *	A buffer cannot be placed on two lists at the same time.
 */
static inline void __skb_queue_after(struct sk_buff_head *list,
				     struct sk_buff *prev,
				     struct sk_buff *newsk)
{
	__skb_insert(newsk, prev, prev->next, list);
}

void skb_append(struct sk_buff *old, struct sk_buff *newsk,
		struct sk_buff_head *list);

static inline void __skb_queue_before(struct sk_buff_head *list,
				      struct sk_buff *next,
				      struct sk_buff *newsk)
{
	__skb_insert(newsk, next->prev, next, list);
}

/**
 *	__skb_queue_head - queue a buffer at the list head
 *	@list: list to use
 *	@newsk: buffer to queue
 *
 *	Queue a buffer at the start of a list. This function takes no locks
 *	and you must therefore hold required locks before calling it.
 *
 *	A buffer cannot be placed on two lists at the same time.
 */
void skb_queue_head(struct sk_buff_head *list, struct sk_buff *newsk);
static inline void __skb_queue_head(struct sk_buff_head *list,
				    struct sk_buff *newsk)
{
	__skb_queue_after(list, (struct sk_buff *)list, newsk);
}

/**
 *	__skb_queue_tail - queue a buffer at the list tail
 *	@list: list to use
 *	@newsk: buffer to queue
 *
 *	Queue a buffer at the end of a list. This function takes no locks
 *	and you must therefore hold required locks before calling it.
 *
 *	A buffer cannot be placed on two lists at the same time.
 */
void skb_queue_tail(struct sk_buff_head *list, struct sk_buff *newsk);
static inline void __skb_queue_tail(struct sk_buff_head *list,
				   struct sk_buff *newsk)
{
	__skb_queue_before(list, (struct sk_buff *)list, newsk);
}

/*
 * remove sk_buff from list. _Must_ be called atomically, and with
 * the list known..
 */
void skb_unlink(struct sk_buff *skb, struct sk_buff_head *list);
static inline void __skb_unlink(struct sk_buff *skb, struct sk_buff_head *list)
{
	struct sk_buff *next, *prev;

	list->qlen--;
	next	   = skb->next;
	prev	   = skb->prev;
	skb->next  = skb->prev = NULL;
	next->prev = prev;
	prev->next = next;
}

/**
 *	__skb_dequeue - remove from the head of the queue
 *	@list: list to dequeue from
 *
 *	Remove the head of the list. This function does not take any locks
 *	so must be used with appropriate locks held only. The head item is
 *	returned or %NULL if the list is empty.
 */
struct sk_buff *skb_dequeue(struct sk_buff_head *list);
static inline struct sk_buff *__skb_dequeue(struct sk_buff_head *list)
{
	struct sk_buff *skb = skb_peek(list);
	if (skb)
		__skb_unlink(skb, list);
	return skb;
}

/**
 *	__skb_dequeue_tail - remove from the tail of the queue
 *	@list: list to dequeue from
 *
 *	Remove the tail of the list. This function does not take any locks
 *	so must be used with appropriate locks held only. The tail item is
 *	returned or %NULL if the list is empty.
 */
struct sk_buff *skb_dequeue_tail(struct sk_buff_head *list);
static inline struct sk_buff *__skb_dequeue_tail(struct sk_buff_head *list)
{
	struct sk_buff *skb = skb_peek_tail(list);
	if (skb)
		__skb_unlink(skb, list);
	return skb;
}


static inline bool skb_is_nonlinear(const struct sk_buff *skb)
{
	return skb->data_len;
}

static inline unsigned int skb_headlen(const struct sk_buff *skb)
{
	return skb->len - skb->data_len;
}

static inline int skb_pagelen(const struct sk_buff *skb)
{
	int i, len = 0;

	for (i = (int)skb_shinfo(skb)->nr_frags - 1; i >= 0; i--)
		len += skb_frag_size(&skb_shinfo(skb)->frags[i]);
	return len + skb_headlen(skb);
}

/**
 * __skb_fill_page_desc - initialise a paged fragment in an skb
 * @skb: buffer containing fragment to be initialised
 * @i: paged fragment index to initialise
 * @page: the page to use for this fragment
 * @off: the offset to the data with @page
 * @size: the length of the data
 *
 * Initialises the @i'th fragment of @skb to point to &size bytes at
 * offset @off within @page.
 *
 * Does not take any additional reference on the fragment.
 */
static inline void __skb_fill_page_desc(struct sk_buff *skb, int i,
					struct page *page, int off, int size)
{
	skb_frag_t *frag = &skb_shinfo(skb)->frags[i];

	/*
	 * Propagate page->pfmemalloc to the skb if we can. The problem is
	 * that not all callers have unique ownership of the page. If
	 * pfmemalloc is set, we check the mapping as a mapping implies
	 * page->index is set (index and pfmemalloc share space).
	 * If it's a valid mapping, we cannot use page->pfmemalloc but we
	 * do not lose pfmemalloc information as the pages would not be
	 * allocated using __GFP_MEMALLOC.
	 */
	frag->page.p		  = page;
	frag->page_offset	  = off;
	skb_frag_size_set(frag, size);

	page = compound_head(page);
	if (page->pfmemalloc && !page->mapping)
		skb->pfmemalloc	= true;
}

/**
 * skb_fill_page_desc - initialise a paged fragment in an skb
 * @skb: buffer containing fragment to be initialised
 * @i: paged fragment index to initialise
 * @page: the page to use for this fragment
 * @off: the offset to the data with @page
 * @size: the length of the data
 *
 * As per __skb_fill_page_desc() -- initialises the @i'th fragment of
 * @skb to point to @size bytes at offset @off within @page. In
 * addition updates @skb such that @i is the last fragment.
 *
 * Does not take any additional reference on the fragment.
 */
static inline void skb_fill_page_desc(struct sk_buff *skb, int i,
				      struct page *page, int off, int size)
{
	__skb_fill_page_desc(skb, i, page, off, size);
	skb_shinfo(skb)->nr_frags = i + 1;
}

void skb_add_rx_frag(struct sk_buff *skb, int i, struct page *page, int off,
		     int size, unsigned int truesize);

void skb_coalesce_rx_frag(struct sk_buff *skb, int i, int size,
			  unsigned int truesize);

#define SKB_PAGE_ASSERT(skb) 	BUG_ON(skb_shinfo(skb)->nr_frags)
#define SKB_FRAG_ASSERT(skb) 	BUG_ON(skb_has_frag_list(skb))
#define SKB_LINEAR_ASSERT(skb)  BUG_ON(skb_is_nonlinear(skb))

#ifdef NET_SKBUFF_DATA_USES_OFFSET
static inline unsigned char *skb_tail_pointer(const struct sk_buff *skb)
{
	return skb->head + skb->tail;
}

static inline void skb_reset_tail_pointer(struct sk_buff *skb)
{
	skb->tail = skb->data - skb->head;
}

static inline void skb_set_tail_pointer(struct sk_buff *skb, const int offset)
{
	skb_reset_tail_pointer(skb);
	skb->tail += offset;
}

#else /* NET_SKBUFF_DATA_USES_OFFSET */
static inline unsigned char *skb_tail_pointer(const struct sk_buff *skb)
{
	return skb->tail;
}

static inline void skb_reset_tail_pointer(struct sk_buff *skb)
{
	skb->tail = skb->data;
}

static inline void skb_set_tail_pointer(struct sk_buff *skb, const int offset)
{
	skb->tail = skb->data + offset;
}

#endif /* NET_SKBUFF_DATA_USES_OFFSET */

/*
 *	Add data to an sk_buff
 */
unsigned char *pskb_put(struct sk_buff *skb, struct sk_buff *tail, int len);
unsigned char *skb_put(struct sk_buff *skb, unsigned int len);
static inline unsigned char *__skb_put(struct sk_buff *skb, unsigned int len)
{
	unsigned char *tmp = skb_tail_pointer(skb);
	SKB_LINEAR_ASSERT(skb);
	skb->tail += len;
	skb->len  += len;
	return tmp;
}

unsigned char *skb_push(struct sk_buff *skb, unsigned int len);
static inline unsigned char *__skb_push(struct sk_buff *skb, unsigned int len)
{
	skb->data -= len;
	skb->len  += len;
	return skb->data;
}

unsigned char *skb_pull(struct sk_buff *skb, unsigned int len);
static inline unsigned char *__skb_pull(struct sk_buff *skb, unsigned int len)
{
	skb->len -= len;
	BUG_ON(skb->len < skb->data_len);
	return skb->data += len;
}

static inline unsigned char *skb_pull_inline(struct sk_buff *skb, unsigned int len)
{
	return unlikely(len > skb->len) ? NULL : __skb_pull(skb, len);
}

unsigned char *__pskb_pull_tail(struct sk_buff *skb, int delta);

static inline unsigned char *__pskb_pull(struct sk_buff *skb, unsigned int len)
{
	if (len > skb_headlen(skb) &&
	    !__pskb_pull_tail(skb, len - skb_headlen(skb)))
		return NULL;
	skb->len -= len;
	return skb->data += len;
}

static inline unsigned char *pskb_pull(struct sk_buff *skb, unsigned int len)
{
	return unlikely(len > skb->len) ? NULL : __pskb_pull(skb, len);
}

static inline int pskb_may_pull(struct sk_buff *skb, unsigned int len)
{
	if (likely(len <= skb_headlen(skb)))
		return 1;
	if (unlikely(len > skb->len))
		return 0;
	return __pskb_pull_tail(skb, len - skb_headlen(skb)) != NULL;
}

/**
 *	skb_headroom - bytes at buffer head
 *	@skb: buffer to check
 *
 *	Return the number of bytes of free space at the head of an &sk_buff.
 */
static inline unsigned int skb_headroom(const struct sk_buff *skb)
{
	return skb->data - skb->head;
}

/**
 *	skb_tailroom - bytes at buffer end
 *	@skb: buffer to check
 *
 *	Return the number of bytes of free space at the tail of an sk_buff
 */
static inline int skb_tailroom(const struct sk_buff *skb)
{
	return skb_is_nonlinear(skb) ? 0 : skb->end - skb->tail;
}

/**
 *	skb_availroom - bytes at buffer end
 *	@skb: buffer to check
 *
 *	Return the number of bytes of free space at the tail of an sk_buff
 *	allocated by sk_stream_alloc()
 */
static inline int skb_availroom(const struct sk_buff *skb)
{
	if (skb_is_nonlinear(skb))
		return 0;

	return skb->end - skb->tail - skb->reserved_tailroom;
}

/**
 *	skb_reserve - adjust headroom
 *	@skb: buffer to alter
 *	@len: bytes to move
 *
 *	Increase the headroom of an empty &sk_buff by reducing the tail
 *	room. This is only allowed for an empty buffer.
 */
static inline void skb_reserve(struct sk_buff *skb, int len)
{
	skb->data += len;
	skb->tail += len;
}

#define ENCAP_TYPE_ETHER	0
#define ENCAP_TYPE_IPPROTO	1

static inline void skb_set_inner_protocol(struct sk_buff *skb,
					  __be16 protocol)
{
	skb->inner_protocol = protocol;
	skb->inner_protocol_type = ENCAP_TYPE_ETHER;
}

static inline void skb_set_inner_ipproto(struct sk_buff *skb,
					 __u8 ipproto)
{
	skb->inner_ipproto = ipproto;
	skb->inner_protocol_type = ENCAP_TYPE_IPPROTO;
}

static inline void skb_reset_inner_headers(struct sk_buff *skb)
{
	skb->inner_mac_header = skb->mac_header;
	skb->inner_network_header = skb->network_header;
	skb->inner_transport_header = skb->transport_header;
}

static inline void skb_reset_mac_len(struct sk_buff *skb)
{
	skb->mac_len = skb->network_header - skb->mac_header;
}

static inline unsigned char *skb_inner_transport_header(const struct sk_buff
							*skb)
{
	return skb->head + skb->inner_transport_header;
}

static inline void skb_reset_inner_transport_header(struct sk_buff *skb)
{
	skb->inner_transport_header = skb->data - skb->head;
}

static inline void skb_set_inner_transport_header(struct sk_buff *skb,
						   const int offset)
{
	skb_reset_inner_transport_header(skb);
	skb->inner_transport_header += offset;
}

static inline unsigned char *skb_inner_network_header(const struct sk_buff *skb)
{
	return skb->head + skb->inner_network_header;
}

static inline void skb_reset_inner_network_header(struct sk_buff *skb)
{
	skb->inner_network_header = skb->data - skb->head;
}

static inline void skb_set_inner_network_header(struct sk_buff *skb,
						const int offset)
{
	skb_reset_inner_network_header(skb);
	skb->inner_network_header += offset;
}

static inline unsigned char *skb_inner_mac_header(const struct sk_buff *skb)
{
	return skb->head + skb->inner_mac_header;
}

static inline void skb_reset_inner_mac_header(struct sk_buff *skb)
{
	skb->inner_mac_header = skb->data - skb->head;
}

static inline void skb_set_inner_mac_header(struct sk_buff *skb,
					    const int offset)
{
	skb_reset_inner_mac_header(skb);
	skb->inner_mac_header += offset;
}
static inline bool skb_transport_header_was_set(const struct sk_buff *skb)
{
	return skb->transport_header != (typeof(skb->transport_header))~0U;
}

static inline unsigned char *skb_transport_header(const struct sk_buff *skb)
{
	return skb->head + skb->transport_header;
}

static inline void skb_reset_transport_header(struct sk_buff *skb)
{
	skb->transport_header = skb->data - skb->head;
}

static inline void skb_set_transport_header(struct sk_buff *skb,
					    const int offset)
{
	skb_reset_transport_header(skb);
	skb->transport_header += offset;
}

static inline unsigned char *skb_network_header(const struct sk_buff *skb)
{
	return skb->head + skb->network_header;
}

static inline void skb_reset_network_header(struct sk_buff *skb)
{
	skb->network_header = skb->data - skb->head;
}

static inline void skb_set_network_header(struct sk_buff *skb, const int offset)
{
	skb_reset_network_header(skb);
	skb->network_header += offset;
}

static inline unsigned char *skb_mac_header(const struct sk_buff *skb)
{
	return skb->head + skb->mac_header;
}

static inline int skb_mac_header_was_set(const struct sk_buff *skb)
{
	return skb->mac_header != (typeof(skb->mac_header))~0U;
}

static inline void skb_reset_mac_header(struct sk_buff *skb)
{
	skb->mac_header = skb->data - skb->head;
}

static inline void skb_set_mac_header(struct sk_buff *skb, const int offset)
{
	skb_reset_mac_header(skb);
	skb->mac_header += offset;
}

static inline void skb_pop_mac_header(struct sk_buff *skb)
{
	skb->mac_header = skb->network_header;
}

static inline void skb_probe_transport_header(struct sk_buff *skb,
					      const int offset_hint)
{
	struct flow_keys keys;

	if (skb_transport_header_was_set(skb))
		return;
	else if (skb_flow_dissect_flow_keys(skb, &keys))
		skb_set_transport_header(skb, keys.basic.thoff);
	else
		skb_set_transport_header(skb, offset_hint);
}

static inline void skb_mac_header_rebuild(struct sk_buff *skb)
{
	if (skb_mac_header_was_set(skb)) {
		const unsigned char *old_mac = skb_mac_header(skb);

		skb_set_mac_header(skb, -skb->mac_len);
		memmove(skb_mac_header(skb), old_mac, skb->mac_len);
	}
}

static inline int skb_checksum_start_offset(const struct sk_buff *skb)
{
	return skb->csum_start - skb_headroom(skb);
}

static inline int skb_transport_offset(const struct sk_buff *skb)
{
	return skb_transport_header(skb) - skb->data;
}

static inline u32 skb_network_header_len(const struct sk_buff *skb)
{
	return skb->transport_header - skb->network_header;
}

static inline u32 skb_inner_network_header_len(const struct sk_buff *skb)
{
	return skb->inner_transport_header - skb->inner_network_header;
}

static inline int skb_network_offset(const struct sk_buff *skb)
{
	return skb_network_header(skb) - skb->data;
}

static inline int skb_inner_network_offset(const struct sk_buff *skb)
{
	return skb_inner_network_header(skb) - skb->data;
}

static inline int pskb_network_may_pull(struct sk_buff *skb, unsigned int len)
{
	return pskb_may_pull(skb, skb_network_offset(skb) + len);
}

/*
 * CPUs often take a performance hit when accessing unaligned memory
 * locations. The actual performance hit varies, it can be small if the
 * hardware handles it or large if we have to take an exception and fix it
 * in software.
 *
 * Since an ethernet header is 14 bytes network drivers often end up with
 * the IP header at an unaligned offset. The IP header can be aligned by
 * shifting the start of the packet by 2 bytes. Drivers should do this
 * with:
 *
 * skb_reserve(skb, NET_IP_ALIGN);
 *
 * The downside to this alignment of the IP header is that the DMA is now
 * unaligned. On some architectures the cost of an unaligned DMA is high
 * and this cost outweighs the gains made by aligning the IP header.
 *
 * Since this trade off varies between architectures, we allow NET_IP_ALIGN
 * to be overridden.
 */
#ifndef NET_IP_ALIGN
#define NET_IP_ALIGN	2
#endif

/*
 * The networking layer reserves some headroom in skb data (via
 * dev_alloc_skb). This is used to avoid having to reallocate skb data when
 * the header has to grow. In the default case, if the header has to grow
 * 32 bytes or less we avoid the reallocation.
 *
 * Unfortunately this headroom changes the DMA alignment of the resulting
 * network packet. As for NET_IP_ALIGN, this unaligned DMA is expensive
 * on some architectures. An architecture can override this value,
 * perhaps setting it to a cacheline in size (since that will maintain
 * cacheline alignment of the DMA). It must be a power of 2.
 *
 * Various parts of the networking layer expect at least 32 bytes of
 * headroom, you should not reduce this.
 *
 * Using max(32, L1_CACHE_BYTES) makes sense (especially with RPS)
 * to reduce average number of cache lines per packet.
 * get_rps_cpus() for example only access one 64 bytes aligned block :
 * NET_IP_ALIGN(2) + ethernet_header(14) + IP_header(20/40) + ports(8)
 */
#ifndef NET_SKB_PAD
#define NET_SKB_PAD	max(32, L1_CACHE_BYTES)
#endif

int ___pskb_trim(struct sk_buff *skb, unsigned int len);

static inline void __skb_trim(struct sk_buff *skb, unsigned int len)
{
	if (unlikely(skb_is_nonlinear(skb))) {
		WARN_ON(1);
		return;
	}
	skb->len = len;
	skb_set_tail_pointer(skb, len);
}

void skb_trim(struct sk_buff *skb, unsigned int len);

static inline int __pskb_trim(struct sk_buff *skb, unsigned int len)
{
	if (skb->data_len)
		return ___pskb_trim(skb, len);
	__skb_trim(skb, len);
	return 0;
}

static inline int pskb_trim(struct sk_buff *skb, unsigned int len)
{
	return (len < skb->len) ? __pskb_trim(skb, len) : 0;
}

/**
 *	pskb_trim_unique - remove end from a paged unique (not cloned) buffer
 *	@skb: buffer to alter
 *	@len: new length
 *
 *	This is identical to pskb_trim except that the caller knows that
 *	the skb is not cloned so we should never get an error due to out-
 *	of-memory.
 */
static inline void pskb_trim_unique(struct sk_buff *skb, unsigned int len)
{
	int err = pskb_trim(skb, len);
	BUG_ON(err);
}

/**
 *	skb_orphan - orphan a buffer
 *	@skb: buffer to orphan
 *
 *	If a buffer currently has an owner then we call the owner's
 *	destructor function and make the @skb unowned. The buffer continues
 *	to exist but is no longer charged to its former owner.
 */
static inline void skb_orphan(struct sk_buff *skb)
{
	if (skb->destructor) {
		skb->destructor(skb);
		skb->destructor = NULL;
		skb->sk		= NULL;
	} else {
		BUG_ON(skb->sk);
	}
}

/**
 *	skb_orphan_frags - orphan the frags contained in a buffer
 *	@skb: buffer to orphan frags from
 *	@gfp_mask: allocation mask for replacement pages
 *
 *	For each frag in the SKB which needs a destructor (i.e. has an
 *	owner) create a copy of that frag and release the original
 *	page by calling the destructor.
 */
static inline int skb_orphan_frags(struct sk_buff *skb, gfp_t gfp_mask)
{
	if (likely(!(skb_shinfo(skb)->tx_flags & SKBTX_DEV_ZEROCOPY)))
		return 0;
	return skb_copy_ubufs(skb, gfp_mask);
}

/**
 *	__skb_queue_purge - empty a list
 *	@list: list to empty
 *
 *	Delete all buffers on an &sk_buff list. Each buffer is removed from
 *	the list and one reference dropped. This function does not take the
 *	list lock and the caller must hold the relevant locks to use it.
 */
void skb_queue_purge(struct sk_buff_head *list);
static inline void __skb_queue_purge(struct sk_buff_head *list)
{
	struct sk_buff *skb;
	while ((skb = __skb_dequeue(list)) != NULL)
		kfree_skb(skb);
}

void *netdev_alloc_frag(unsigned int fragsz);

struct sk_buff *__netdev_alloc_skb(struct net_device *dev, unsigned int length,
				   gfp_t gfp_mask);

/**
 *	netdev_alloc_skb - allocate an skbuff for rx on a specific device
 *	@dev: network device to receive on
 *	@length: length to allocate
 *
 *	Allocate a new &sk_buff and assign it a usage count of one. The
 *	buffer has unspecified headroom built in. Users should allocate
 *	the headroom they think they need without accounting for the
 *	built in space. The built in space is used for optimisations.
 *
 *	%NULL is returned if there is no free memory. Although this function
 *	allocates memory it can be called from an interrupt.
 */
static inline struct sk_buff *netdev_alloc_skb(struct net_device *dev,
					       unsigned int length)
{
	return __netdev_alloc_skb(dev, length, GFP_ATOMIC);
}

/* legacy helper around __netdev_alloc_skb() */
static inline struct sk_buff *__dev_alloc_skb(unsigned int length,
					      gfp_t gfp_mask)
{
	return __netdev_alloc_skb(NULL, length, gfp_mask);
}

/* legacy helper around netdev_alloc_skb() */
static inline struct sk_buff *dev_alloc_skb(unsigned int length)
{
	return netdev_alloc_skb(NULL, length);
}


static inline struct sk_buff *__netdev_alloc_skb_ip_align(struct net_device *dev,
		unsigned int length, gfp_t gfp)
{
	struct sk_buff *skb = __netdev_alloc_skb(dev, length + NET_IP_ALIGN, gfp);

	if (NET_IP_ALIGN && skb)
		skb_reserve(skb, NET_IP_ALIGN);
	return skb;
}

static inline struct sk_buff *netdev_alloc_skb_ip_align(struct net_device *dev,
		unsigned int length)
{
	return __netdev_alloc_skb_ip_align(dev, length, GFP_ATOMIC);
}

static inline void skb_free_frag(void *addr)
{
	__free_page_frag(addr);
}

void *napi_alloc_frag(unsigned int fragsz);
struct sk_buff *__napi_alloc_skb(struct napi_struct *napi,
				 unsigned int length, gfp_t gfp_mask);
static inline struct sk_buff *napi_alloc_skb(struct napi_struct *napi,
					     unsigned int length)
{
	return __napi_alloc_skb(napi, length, GFP_ATOMIC);
}

/**
 * __dev_alloc_pages - allocate page for network Rx
 * @gfp_mask: allocation priority. Set __GFP_NOMEMALLOC if not for network Rx
 * @order: size of the allocation
 *
 * Allocate a new page.
 *
 * %NULL is returned if there is no free memory.
*/
static inline struct page *__dev_alloc_pages(gfp_t gfp_mask,
					     unsigned int order)
{
	/* This piece of code contains several assumptions.
	 * 1.  This is for device Rx, therefor a cold page is preferred.
	 * 2.  The expectation is the user wants a compound page.
	 * 3.  If requesting a order 0 page it will not be compound
	 *     due to the check to see if order has a value in prep_new_page
	 * 4.  __GFP_MEMALLOC is ignored if __GFP_NOMEMALLOC is set due to
	 *     code in gfp_to_alloc_flags that should be enforcing this.
	 */
	gfp_mask |= __GFP_COLD | __GFP_COMP | __GFP_MEMALLOC;

	return alloc_pages_node(NUMA_NO_NODE, gfp_mask, order);
}

static inline struct page *dev_alloc_pages(unsigned int order)
{
	return __dev_alloc_pages(GFP_ATOMIC, order);
}

/**
 * __dev_alloc_page - allocate a page for network Rx
 * @gfp_mask: allocation priority. Set __GFP_NOMEMALLOC if not for network Rx
 *
 * Allocate a new page.
 *
 * %NULL is returned if there is no free memory.
 */
static inline struct page *__dev_alloc_page(gfp_t gfp_mask)
{
	return __dev_alloc_pages(gfp_mask, 0);
}

static inline struct page *dev_alloc_page(void)
{
	return __dev_alloc_page(GFP_ATOMIC);
}

/**
 *	skb_propagate_pfmemalloc - Propagate pfmemalloc if skb is allocated after RX page
 *	@page: The page that was allocated from skb_alloc_page
 *	@skb: The skb that may need pfmemalloc set
 */
static inline void skb_propagate_pfmemalloc(struct page *page,
					     struct sk_buff *skb)
{
	if (page && page->pfmemalloc)
		skb->pfmemalloc = true;
}

/**
 * skb_frag_page - retrieve the page referred to by a paged fragment
 * @frag: the paged fragment
 *
 * Returns the &struct page associated with @frag.
 */
static inline struct page *skb_frag_page(const skb_frag_t *frag)
{
	return frag->page.p;
}

/**
 * __skb_frag_ref - take an addition reference on a paged fragment.
 * @frag: the paged fragment
 *
 * Takes an additional reference on the paged fragment @frag.
 */
static inline void __skb_frag_ref(skb_frag_t *frag)
{
	get_page(skb_frag_page(frag));
}

/**
 * skb_frag_ref - take an addition reference on a paged fragment of an skb.
 * @skb: the buffer
 * @f: the fragment offset.
 *
 * Takes an additional reference on the @f'th paged fragment of @skb.
 */
static inline void skb_frag_ref(struct sk_buff *skb, int f)
{
	__skb_frag_ref(&skb_shinfo(skb)->frags[f]);
}

/**
 * __skb_frag_unref - release a reference on a paged fragment.
 * @frag: the paged fragment
 *
 * Releases a reference on the paged fragment @frag.
 */
static inline void __skb_frag_unref(skb_frag_t *frag)
{
	put_page(skb_frag_page(frag));
}

/**
 * skb_frag_unref - release a reference on a paged fragment of an skb.
 * @skb: the buffer
 * @f: the fragment offset
 *
 * Releases a reference on the @f'th paged fragment of @skb.
 */
static inline void skb_frag_unref(struct sk_buff *skb, int f)
{
	__skb_frag_unref(&skb_shinfo(skb)->frags[f]);
}

/**
 * skb_frag_address - gets the address of the data contained in a paged fragment
 * @frag: the paged fragment buffer
 *
 * Returns the address of the data within @frag. The page must already
 * be mapped.
 */
static inline void *skb_frag_address(const skb_frag_t *frag)
{
	return page_address(skb_frag_page(frag)) + frag->page_offset;
}

/**
 * skb_frag_address_safe - gets the address of the data contained in a paged fragment
 * @frag: the paged fragment buffer
 *
 * Returns the address of the data within @frag. Checks that the page
 * is mapped and returns %NULL otherwise.
 */
static inline void *skb_frag_address_safe(const skb_frag_t *frag)
{
	void *ptr = page_address(skb_frag_page(frag));
	if (unlikely(!ptr))
		return NULL;

	return ptr + frag->page_offset;
}

/**
 * __skb_frag_set_page - sets the page contained in a paged fragment
 * @frag: the paged fragment
 * @page: the page to set
 *
 * Sets the fragment @frag to contain @page.
 */
static inline void __skb_frag_set_page(skb_frag_t *frag, struct page *page)
{
	frag->page.p = page;
}

/**
 * skb_frag_set_page - sets the page contained in a paged fragment of an skb
 * @skb: the buffer
 * @f: the fragment offset
 * @page: the page to set
 *
 * Sets the @f'th fragment of @skb to contain @page.
 */
static inline void skb_frag_set_page(struct sk_buff *skb, int f,
				     struct page *page)
{
	__skb_frag_set_page(&skb_shinfo(skb)->frags[f], page);
}

bool skb_page_frag_refill(unsigned int sz, struct page_frag *pfrag, gfp_t prio);

/**
 * skb_frag_dma_map - maps a paged fragment via the DMA API
 * @dev: the device to map the fragment to
 * @frag: the paged fragment to map
 * @offset: the offset within the fragment (starting at the
 *          fragment's own offset)
 * @size: the number of bytes to map
 * @dir: the direction of the mapping (%PCI_DMA_*)
 *
 * Maps the page associated with @frag to @device.
 */
static inline dma_addr_t skb_frag_dma_map(struct device *dev,
					  const skb_frag_t *frag,
					  size_t offset, size_t size,
					  enum dma_data_direction dir)
{
	return dma_map_page(dev, skb_frag_page(frag),
			    frag->page_offset + offset, size, dir);
}

static inline struct sk_buff *pskb_copy(struct sk_buff *skb,
					gfp_t gfp_mask)
{
	return __pskb_copy(skb, skb_headroom(skb), gfp_mask);
}


static inline struct sk_buff *pskb_copy_for_clone(struct sk_buff *skb,
						  gfp_t gfp_mask)
{
	return __pskb_copy_fclone(skb, skb_headroom(skb), gfp_mask, true);
}


/**
 *	skb_clone_writable - is the header of a clone writable
 *	@skb: buffer to check
 *	@len: length up to which to write
 *
 *	Returns true if modifying the header part of the cloned buffer
 *	does not requires the data to be copied.
 */
static inline int skb_clone_writable(const struct sk_buff *skb, unsigned int len)
{
	return !skb_header_cloned(skb) &&
	       skb_headroom(skb) + len <= skb->hdr_len;
}

static inline int __skb_cow(struct sk_buff *skb, unsigned int headroom,
			    int cloned)
{
	int delta = 0;

	if (headroom > skb_headroom(skb))
		delta = headroom - skb_headroom(skb);

	if (delta || cloned)
		return pskb_expand_head(skb, ALIGN(delta, NET_SKB_PAD), 0,
					GFP_ATOMIC);
	return 0;
}

/**
 *	skb_cow - copy header of skb when it is required
 *	@skb: buffer to cow
 *	@headroom: needed headroom
 *
 *	If the skb passed lacks sufficient headroom or its data part
 *	is shared, data is reallocated. If reallocation fails, an error
 *	is returned and original skb is not changed.
 *
 *	The result is skb with writable area skb->head...skb->tail
 *	and at least @headroom of space at head.
 */
static inline int skb_cow(struct sk_buff *skb, unsigned int headroom)
{
	return __skb_cow(skb, headroom, skb_cloned(skb));
}

/**
 *	skb_cow_head - skb_cow but only making the head writable
 *	@skb: buffer to cow
 *	@headroom: needed headroom
 *
 *	This function is identical to skb_cow except that we replace the
 *	skb_cloned check by skb_header_cloned.  It should be used when
 *	you only need to push on some header and do not need to modify
 *	the data.
 */
static inline int skb_cow_head(struct sk_buff *skb, unsigned int headroom)
{
	return __skb_cow(skb, headroom, skb_header_cloned(skb));
}

/**
 *	skb_padto	- pad an skbuff up to a minimal size
 *	@skb: buffer to pad
 *	@len: minimal length
 *
 *	Pads up a buffer to ensure the trailing bytes exist and are
 *	blanked. If the buffer already contains sufficient data it
 *	is untouched. Otherwise it is extended. Returns zero on
 *	success. The skb is freed on error.
 */
static inline int skb_padto(struct sk_buff *skb, unsigned int len)
{
	unsigned int size = skb->len;
	if (likely(size >= len))
		return 0;
	return skb_pad(skb, len - size);
}

/**
 *	skb_put_padto - increase size and pad an skbuff up to a minimal size
 *	@skb: buffer to pad
 *	@len: minimal length
 *
 *	Pads up a buffer to ensure the trailing bytes exist and are
 *	blanked. If the buffer already contains sufficient data it
 *	is untouched. Otherwise it is extended. Returns zero on
 *	success. The skb is freed on error.
 */
static inline int skb_put_padto(struct sk_buff *skb, unsigned int len)
{
	unsigned int size = skb->len;

	if (unlikely(size < len)) {
		len -= size;
		if (skb_pad(skb, len))
			return -ENOMEM;
		__skb_put(skb, len);
	}
	return 0;
}

static inline int skb_add_data(struct sk_buff *skb,
			       struct iov_iter *from, int copy)
{
	const int off = skb->len;

	if (skb->ip_summed == CHECKSUM_NONE) {
		__wsum csum = 0;
		if (csum_and_copy_from_iter(skb_put(skb, copy), copy,
					    &csum, from) == copy) {
			skb->csum = csum_block_add(skb->csum, csum, off);
			return 0;
		}
	} else if (copy_from_iter(skb_put(skb, copy), copy, from) == copy)
		return 0;

	__skb_trim(skb, off);
	return -EFAULT;
}

static inline bool skb_can_coalesce(struct sk_buff *skb, int i,
				    const struct page *page, int off)
{
	if (i) {
		const struct skb_frag_struct *frag = &skb_shinfo(skb)->frags[i - 1];

		return page == skb_frag_page(frag) &&
		       off == frag->page_offset + skb_frag_size(frag);
	}
	return false;
}

static inline int __skb_linearize(struct sk_buff *skb)
{
	return __pskb_pull_tail(skb, skb->data_len) ? 0 : -ENOMEM;
}

/**
 *	skb_linearize - convert paged skb to linear one
 *	@skb: buffer to linarize
 *
 *	If there is no free memory -ENOMEM is returned, otherwise zero
 *	is returned and the old skb data released.
 */
static inline int skb_linearize(struct sk_buff *skb)
{
	return skb_is_nonlinear(skb) ? __skb_linearize(skb) : 0;
}

/**
 * skb_has_shared_frag - can any frag be overwritten
 * @skb: buffer to test
 *
 * Return true if the skb has at least one frag that might be modified
 * by an external entity (as in vmsplice()/sendfile())
 */
static inline bool skb_has_shared_frag(const struct sk_buff *skb)
{
	return skb_is_nonlinear(skb) &&
	       skb_shinfo(skb)->tx_flags & SKBTX_SHARED_FRAG;
}

/**
 *	skb_linearize_cow - make sure skb is linear and writable
 *	@skb: buffer to process
 *
 *	If there is no free memory -ENOMEM is returned, otherwise zero
 *	is returned and the old skb data released.
 */
static inline int skb_linearize_cow(struct sk_buff *skb)
{
	return skb_is_nonlinear(skb) || skb_cloned(skb) ?
	       __skb_linearize(skb) : 0;
}

/**
 *	skb_postpull_rcsum - update checksum for received skb after pull
 *	@skb: buffer to update
 *	@start: start of data before pull
 *	@len: length of data pulled
 *
 *	After doing a pull on a received packet, you need to call this to
 *	update the CHECKSUM_COMPLETE checksum, or set ip_summed to
 *	CHECKSUM_NONE so that it can be recomputed from scratch.
 */

static inline void skb_postpull_rcsum(struct sk_buff *skb,
				      const void *start, unsigned int len)
{
	if (skb->ip_summed == CHECKSUM_COMPLETE)
		skb->csum = csum_sub(skb->csum, csum_partial(start, len, 0));
}

unsigned char *skb_pull_rcsum(struct sk_buff *skb, unsigned int len);

/**
 *	pskb_trim_rcsum - trim received skb and update checksum
 *	@skb: buffer to trim
 *	@len: new length
 *
 *	This is exactly the same as pskb_trim except that it ensures the
 *	checksum of received packets are still valid after the operation.
 */

static inline int pskb_trim_rcsum(struct sk_buff *skb, unsigned int len)
{
	if (likely(len >= skb->len))
		return 0;
	if (skb->ip_summed == CHECKSUM_COMPLETE)
		skb->ip_summed = CHECKSUM_NONE;
	return __pskb_trim(skb, len);
}

#define skb_queue_walk(queue, skb) \
		for (skb = (queue)->next;					\
		     skb != (struct sk_buff *)(queue);				\
		     skb = skb->next)

#define skb_queue_walk_safe(queue, skb, tmp)					\
		for (skb = (queue)->next, tmp = skb->next;			\
		     skb != (struct sk_buff *)(queue);				\
		     skb = tmp, tmp = skb->next)

#define skb_queue_walk_from(queue, skb)						\
		for (; skb != (struct sk_buff *)(queue);			\
		     skb = skb->next)

#define skb_queue_walk_from_safe(queue, skb, tmp)				\
		for (tmp = skb->next;						\
		     skb != (struct sk_buff *)(queue);				\
		     skb = tmp, tmp = skb->next)

#define skb_queue_reverse_walk(queue, skb) \
		for (skb = (queue)->prev;					\
		     skb != (struct sk_buff *)(queue);				\
		     skb = skb->prev)

#define skb_queue_reverse_walk_safe(queue, skb, tmp)				\
		for (skb = (queue)->prev, tmp = skb->prev;			\
		     skb != (struct sk_buff *)(queue);				\
		     skb = tmp, tmp = skb->prev)

#define skb_queue_reverse_walk_from_safe(queue, skb, tmp)			\
		for (tmp = skb->prev;						\
		     skb != (struct sk_buff *)(queue);				\
		     skb = tmp, tmp = skb->prev)

static inline bool skb_has_frag_list(const struct sk_buff *skb)
{
	return skb_shinfo(skb)->frag_list != NULL;
}

static inline void skb_frag_list_init(struct sk_buff *skb)
{
	skb_shinfo(skb)->frag_list = NULL;
}

static inline void skb_frag_add_head(struct sk_buff *skb, struct sk_buff *frag)
{
	frag->next = skb_shinfo(skb)->frag_list;
	skb_shinfo(skb)->frag_list = frag;
}

#define skb_walk_frags(skb, iter)	\
	for (iter = skb_shinfo(skb)->frag_list; iter; iter = iter->next)

struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned flags,
				    int *peeked, int *off, int *err);
struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned flags, int noblock,
				  int *err);
unsigned int datagram_poll(struct file *file, struct socket *sock,
			   struct poll_table_struct *wait);
int skb_copy_datagram_iter(const struct sk_buff *from, int offset,
			   struct iov_iter *to, int size);
static inline int skb_copy_datagram_msg(const struct sk_buff *from, int offset,
					struct msghdr *msg, int size)
{
	return skb_copy_datagram_iter(from, offset, &msg->msg_iter, size);
}
int skb_copy_and_csum_datagram_msg(struct sk_buff *skb, int hlen,
				   struct msghdr *msg);
int skb_copy_datagram_from_iter(struct sk_buff *skb, int offset,
				 struct iov_iter *from, int len);
int zerocopy_sg_from_iter(struct sk_buff *skb, struct iov_iter *frm);
void skb_free_datagram(struct sock *sk, struct sk_buff *skb);
void skb_free_datagram_locked(struct sock *sk, struct sk_buff *skb);
int skb_kill_datagram(struct sock *sk, struct sk_buff *skb, unsigned int flags);
int skb_copy_bits(const struct sk_buff *skb, int offset, void *to, int len);
int skb_store_bits(struct sk_buff *skb, int offset, const void *from, int len);
__wsum skb_copy_and_csum_bits(const struct sk_buff *skb, int offset, u8 *to,
			      int len, __wsum csum);
ssize_t skb_socket_splice(struct sock *sk,
			  struct pipe_inode_info *pipe,
			  struct splice_pipe_desc *spd);
int skb_splice_bits(struct sk_buff *skb, struct sock *sk, unsigned int offset,
		    struct pipe_inode_info *pipe, unsigned int len,
		    unsigned int flags,
		    ssize_t (*splice_cb)(struct sock *,
					 struct pipe_inode_info *,
					 struct splice_pipe_desc *));
void skb_copy_and_csum_dev(const struct sk_buff *skb, u8 *to);
unsigned int skb_zerocopy_headlen(const struct sk_buff *from);
int skb_zerocopy(struct sk_buff *to, struct sk_buff *from,
		 int len, int hlen);
void skb_split(struct sk_buff *skb, struct sk_buff *skb1, const u32 len);
int skb_shift(struct sk_buff *tgt, struct sk_buff *skb, int shiftlen);
void skb_scrub_packet(struct sk_buff *skb, bool xnet);
unsigned int skb_gso_transport_seglen(const struct sk_buff *skb);
struct sk_buff *skb_segment(struct sk_buff *skb, netdev_features_t features);
struct sk_buff *skb_vlan_untag(struct sk_buff *skb);
int skb_ensure_writable(struct sk_buff *skb, int write_len);
int skb_vlan_pop(struct sk_buff *skb);
int skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci);

static inline int memcpy_from_msg(void *data, struct msghdr *msg, int len)
{
	return copy_from_iter(data, len, &msg->msg_iter) == len ? 0 : -EFAULT;
}

static inline int memcpy_to_msg(struct msghdr *msg, void *data, int len)
{
	return copy_to_iter(data, len, &msg->msg_iter) == len ? 0 : -EFAULT;
}

struct skb_checksum_ops {
	__wsum (*update)(const void *mem, int len, __wsum wsum);
	__wsum (*combine)(__wsum csum, __wsum csum2, int offset, int len);
};

__wsum __skb_checksum(const struct sk_buff *skb, int offset, int len,
		      __wsum csum, const struct skb_checksum_ops *ops);
__wsum skb_checksum(const struct sk_buff *skb, int offset, int len,
		    __wsum csum);

static inline void *__skb_header_pointer(const struct sk_buff *skb, int offset,
					 int len, void *data, int hlen, void *buffer)
{
	if (hlen - offset >= len)
		return data + offset;

	if (!skb ||
	    skb_copy_bits(skb, offset, buffer, len) < 0)
		return NULL;

	return buffer;
}

static inline void *skb_header_pointer(const struct sk_buff *skb, int offset,
				       int len, void *buffer)
{
	return __skb_header_pointer(skb, offset, len, skb->data,
				    skb_headlen(skb), buffer);
}

/**
 *	skb_needs_linearize - check if we need to linearize a given skb
 *			      depending on the given device features.
 *	@skb: socket buffer to check
 *	@features: net device features
 *
 *	Returns true if either:
 *	1. skb has frag_list and the device doesn't support FRAGLIST, or
 *	2. skb is fragmented and the device does not support SG.
 */
static inline bool skb_needs_linearize(struct sk_buff *skb,
				       netdev_features_t features)
{
	return skb_is_nonlinear(skb) &&
	       ((skb_has_frag_list(skb) && !(features & NETIF_F_FRAGLIST)) ||
		(skb_shinfo(skb)->nr_frags && !(features & NETIF_F_SG)));
}

static inline void skb_copy_from_linear_data(const struct sk_buff *skb,
					     void *to,
					     const unsigned int len)
{
	memcpy(to, skb->data, len);
}

static inline void skb_copy_from_linear_data_offset(const struct sk_buff *skb,
						    const int offset, void *to,
						    const unsigned int len)
{
	memcpy(to, skb->data + offset, len);
}

static inline void skb_copy_to_linear_data(struct sk_buff *skb,
					   const void *from,
					   const unsigned int len)
{
	memcpy(skb->data, from, len);
}

static inline void skb_copy_to_linear_data_offset(struct sk_buff *skb,
						  const int offset,
						  const void *from,
						  const unsigned int len)
{
	memcpy(skb->data + offset, from, len);
}

void skb_init(void);

static inline ktime_t skb_get_ktime(const struct sk_buff *skb)
{
	return skb->tstamp;
}

/**
 *	skb_get_timestamp - get timestamp from a skb
 *	@skb: skb to get stamp from
 *	@stamp: pointer to struct timeval to store stamp in
 *
 *	Timestamps are stored in the skb as offsets to a base timestamp.
 *	This function converts the offset back to a struct timeval and stores
 *	it in stamp.
 */
static inline void skb_get_timestamp(const struct sk_buff *skb,
				     struct timeval *stamp)
{
	*stamp = ktime_to_timeval(skb->tstamp);
}

static inline void skb_get_timestampns(const struct sk_buff *skb,
				       struct timespec *stamp)
{
	*stamp = ktime_to_timespec(skb->tstamp);
}

static inline void __net_timestamp(struct sk_buff *skb)
{
	skb->tstamp = ktime_get_real();
}

static inline ktime_t net_timedelta(ktime_t t)
{
	return ktime_sub(ktime_get_real(), t);
}

static inline ktime_t net_invalid_timestamp(void)
{
	return ktime_set(0, 0);
}

struct sk_buff *skb_clone_sk(struct sk_buff *skb);

#ifdef CONFIG_NETWORK_PHY_TIMESTAMPING

void skb_clone_tx_timestamp(struct sk_buff *skb);
bool skb_defer_rx_timestamp(struct sk_buff *skb);

#else /* CONFIG_NETWORK_PHY_TIMESTAMPING */

static inline void skb_clone_tx_timestamp(struct sk_buff *skb)
{
}

static inline bool skb_defer_rx_timestamp(struct sk_buff *skb)
{
	return false;
}

#endif /* !CONFIG_NETWORK_PHY_TIMESTAMPING */

/**
 * skb_complete_tx_timestamp() - deliver cloned skb with tx timestamps
 *
 * PHY drivers may accept clones of transmitted packets for
 * timestamping via their phy_driver.txtstamp method. These drivers
 * must call this function to return the skb back to the stack, with
 * or without a timestamp.
 *
 * @skb: clone of the the original outgoing packet
 * @hwtstamps: hardware time stamps, may be NULL if not available
 *
 */
void skb_complete_tx_timestamp(struct sk_buff *skb,
			       struct skb_shared_hwtstamps *hwtstamps);

void __skb_tstamp_tx(struct sk_buff *orig_skb,
		     struct skb_shared_hwtstamps *hwtstamps,
		     struct sock *sk, int tstype);

/**
 * skb_tstamp_tx - queue clone of skb with send time stamps
 * @orig_skb:	the original outgoing packet
 * @hwtstamps:	hardware time stamps, may be NULL if not available
 *
 * If the skb has a socket associated, then this function clones the
 * skb (thus sharing the actual data and optional structures), stores
 * the optional hardware time stamping information (if non NULL) or
 * generates a software time stamp (otherwise), then queues the clone
 * to the error queue of the socket.  Errors are silently ignored.
 */
void skb_tstamp_tx(struct sk_buff *orig_skb,
		   struct skb_shared_hwtstamps *hwtstamps);

static inline void sw_tx_timestamp(struct sk_buff *skb)
{
	if (skb_shinfo(skb)->tx_flags & SKBTX_SW_TSTAMP &&
	    !(skb_shinfo(skb)->tx_flags & SKBTX_IN_PROGRESS))
		skb_tstamp_tx(skb, NULL);
}

/**
 * skb_tx_timestamp() - Driver hook for transmit timestamping
 *
 * Ethernet MAC Drivers should call this function in their hard_xmit()
 * function immediately before giving the sk_buff to the MAC hardware.
 *
 * Specifically, one should make absolutely sure that this function is
 * called before TX completion of this packet can trigger.  Otherwise
 * the packet could potentially already be freed.
 *
 * @skb: A socket buffer.
 */
static inline void skb_tx_timestamp(struct sk_buff *skb)
{
	skb_clone_tx_timestamp(skb);
	sw_tx_timestamp(skb);
}

/**
 * skb_complete_wifi_ack - deliver skb with wifi status
 *
 * @skb: the original outgoing packet
 * @acked: ack status
 *
 */
void skb_complete_wifi_ack(struct sk_buff *skb, bool acked);

__sum16 __skb_checksum_complete_head(struct sk_buff *skb, int len);
__sum16 __skb_checksum_complete(struct sk_buff *skb);

static inline int skb_csum_unnecessary(const struct sk_buff *skb)
{
	return ((skb->ip_summed == CHECKSUM_UNNECESSARY) ||
		skb->csum_valid ||
		(skb->ip_summed == CHECKSUM_PARTIAL &&
		 skb_checksum_start_offset(skb) >= 0));
}

/**
 *	skb_checksum_complete - Calculate checksum of an entire packet
 *	@skb: packet to process
 *
 *	This function calculates the checksum over the entire packet plus
 *	the value of skb->csum.  The latter can be used to supply the
 *	checksum of a pseudo header as used by TCP/UDP.  It returns the
 *	checksum.
 *
 *	For protocols that contain complete checksums such as ICMP/TCP/UDP,
 *	this function can be used to verify that checksum on received
 *	packets.  In that case the function should return zero if the
 *	checksum is correct.  In particular, this function will return zero
 *	if skb->ip_summed is CHECKSUM_UNNECESSARY which indicates that the
 *	hardware has already verified the correctness of the checksum.
 */
static inline __sum16 skb_checksum_complete(struct sk_buff *skb)
{
	return skb_csum_unnecessary(skb) ?
	       0 : __skb_checksum_complete(skb);
}

static inline void __skb_decr_checksum_unnecessary(struct sk_buff *skb)
{
	if (skb->ip_summed == CHECKSUM_UNNECESSARY) {
		if (skb->csum_level == 0)
			skb->ip_summed = CHECKSUM_NONE;
		else
			skb->csum_level--;
	}
}

static inline void __skb_incr_checksum_unnecessary(struct sk_buff *skb)
{
	if (skb->ip_summed == CHECKSUM_UNNECESSARY) {
		if (skb->csum_level < SKB_MAX_CSUM_LEVEL)
			skb->csum_level++;
	} else if (skb->ip_summed == CHECKSUM_NONE) {
		skb->ip_summed = CHECKSUM_UNNECESSARY;
		skb->csum_level = 0;
	}
}

static inline void __skb_mark_checksum_bad(struct sk_buff *skb)
{
	/* Mark current checksum as bad (typically called from GRO
	 * path). In the case that ip_summed is CHECKSUM_NONE
	 * this must be the first checksum encountered in the packet.
	 * When ip_summed is CHECKSUM_UNNECESSARY, this is the first
	 * checksum after the last one validated. For UDP, a zero
	 * checksum can not be marked as bad.
	 */

	if (skb->ip_summed == CHECKSUM_NONE ||
	    skb->ip_summed == CHECKSUM_UNNECESSARY)
		skb->csum_bad = 1;
}

/* Check if we need to perform checksum complete validation.
 *
 * Returns true if checksum complete is needed, false otherwise
 * (either checksum is unnecessary or zero checksum is allowed).
 */
static inline bool __skb_checksum_validate_needed(struct sk_buff *skb,
						  bool zero_okay,
						  __sum16 check)
{
	if (skb_csum_unnecessary(skb) || (zero_okay && !check)) {
		skb->csum_valid = 1;
		__skb_decr_checksum_unnecessary(skb);
		return false;
	}

	return true;
}

/* For small packets <= CHECKSUM_BREAK peform checksum complete directly
 * in checksum_init.
 */
#define CHECKSUM_BREAK 76

/* Unset checksum-complete
 *
 * Unset checksum complete can be done when packet is being modified
 * (uncompressed for instance) and checksum-complete value is
 * invalidated.
 */
static inline void skb_checksum_complete_unset(struct sk_buff *skb)
{
	if (skb->ip_summed == CHECKSUM_COMPLETE)
		skb->ip_summed = CHECKSUM_NONE;
}

/* Validate (init) checksum based on checksum complete.
 *
 * Return values:
 *   0: checksum is validated or try to in skb_checksum_complete. In the latter
 *	case the ip_summed will not be CHECKSUM_UNNECESSARY and the pseudo
 *	checksum is stored in skb->csum for use in __skb_checksum_complete
 *   non-zero: value of invalid checksum
 *
 */
static inline __sum16 __skb_checksum_validate_complete(struct sk_buff *skb,
						       bool complete,
						       __wsum psum)
{
	if (skb->ip_summed == CHECKSUM_COMPLETE) {
		if (!csum_fold(csum_add(psum, skb->csum))) {
			skb->csum_valid = 1;
			return 0;
		}
	} else if (skb->csum_bad) {
		/* ip_summed == CHECKSUM_NONE in this case */
		return (__force __sum16)1;
	}

	skb->csum = psum;

	if (complete || skb->len <= CHECKSUM_BREAK) {
		__sum16 csum;

		csum = __skb_checksum_complete(skb);
		skb->csum_valid = !csum;
		return csum;
	}

	return 0;
}

static inline __wsum null_compute_pseudo(struct sk_buff *skb, int proto)
{
	return 0;
}

/* Perform checksum validate (init). Note that this is a macro since we only
 * want to calculate the pseudo header which is an input function if necessary.
 * First we try to validate without any computation (checksum unnecessary) and
 * then calculate based on checksum complete calling the function to compute
 * pseudo header.
 *
 * Return values:
 *   0: checksum is validated or try to in skb_checksum_complete
 *   non-zero: value of invalid checksum
 */
#define __skb_checksum_validate(skb, proto, complete,			\
				zero_okay, check, compute_pseudo)	\
({									\
	__sum16 __ret = 0;						\
	skb->csum_valid = 0;						\
	if (__skb_checksum_validate_needed(skb, zero_okay, check))	\
		__ret = __skb_checksum_validate_complete(skb,		\
				complete, compute_pseudo(skb, proto));	\
	__ret;								\
})

#define skb_checksum_init(skb, proto, compute_pseudo)			\
	__skb_checksum_validate(skb, proto, false, false, 0, compute_pseudo)

#define skb_checksum_init_zero_check(skb, proto, check, compute_pseudo)	\
	__skb_checksum_validate(skb, proto, false, true, check, compute_pseudo)

#define skb_checksum_validate(skb, proto, compute_pseudo)		\
	__skb_checksum_validate(skb, proto, true, false, 0, compute_pseudo)

#define skb_checksum_validate_zero_check(skb, proto, check,		\
					 compute_pseudo)		\
	__skb_checksum_validate(skb, proto, true, true, check, compute_pseudo)

#define skb_checksum_simple_validate(skb)				\
	__skb_checksum_validate(skb, 0, true, false, 0, null_compute_pseudo)

static inline bool __skb_checksum_convert_check(struct sk_buff *skb)
{
	return (skb->ip_summed == CHECKSUM_NONE &&
		skb->csum_valid && !skb->csum_bad);
}

static inline void __skb_checksum_convert(struct sk_buff *skb,
					  __sum16 check, __wsum pseudo)
{
	skb->csum = ~pseudo;
	skb->ip_summed = CHECKSUM_COMPLETE;
}

#define skb_checksum_try_convert(skb, proto, check, compute_pseudo)	\
do {									\
	if (__skb_checksum_convert_check(skb))				\
		__skb_checksum_convert(skb, check,			\
				       compute_pseudo(skb, proto));	\
} while (0)

static inline void skb_remcsum_adjust_partial(struct sk_buff *skb, void *ptr,
					      u16 start, u16 offset)
{
	skb->ip_summed = CHECKSUM_PARTIAL;
	skb->csum_start = ((unsigned char *)ptr + start) - skb->head;
	skb->csum_offset = offset - start;
}

/* Update skbuf and packet to reflect the remote checksum offload operation.
 * When called, ptr indicates the starting point for skb->csum when
 * ip_summed is CHECKSUM_COMPLETE. If we need create checksum complete
 * here, skb_postpull_rcsum is done so skb->csum start is ptr.
 */
static inline void skb_remcsum_process(struct sk_buff *skb, void *ptr,
				       int start, int offset, bool nopartial)
{
	__wsum delta;

	if (!nopartial) {
		skb_remcsum_adjust_partial(skb, ptr, start, offset);
		return;
	}

	 if (unlikely(skb->ip_summed != CHECKSUM_COMPLETE)) {
		__skb_checksum_complete(skb);
		skb_postpull_rcsum(skb, skb->data, ptr - (void *)skb->data);
	}

	delta = remcsum_adjust(ptr, skb->csum, start, offset);

	/* Adjust skb->csum since we changed the packet */
	skb->csum = csum_add(skb->csum, delta);
}

#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
void nf_conntrack_destroy(struct nf_conntrack *nfct);
static inline void nf_conntrack_put(struct nf_conntrack *nfct)
{
	if (nfct && atomic_dec_and_test(&nfct->use))
		nf_conntrack_destroy(nfct);
}
static inline void nf_conntrack_get(struct nf_conntrack *nfct)
{
	if (nfct)
		atomic_inc(&nfct->use);
}
#endif
#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
static inline void nf_bridge_put(struct nf_bridge_info *nf_bridge)
{
	if (nf_bridge && atomic_dec_and_test(&nf_bridge->use))
		kfree(nf_bridge);
}
static inline void nf_bridge_get(struct nf_bridge_info *nf_bridge)
{
	if (nf_bridge)
		atomic_inc(&nf_bridge->use);
}
#endif /* CONFIG_BRIDGE_NETFILTER */
static inline void nf_reset(struct sk_buff *skb)
{
#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
	nf_conntrack_put(skb->nfct);
	skb->nfct = NULL;
#endif
#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
	nf_bridge_put(skb->nf_bridge);
	skb->nf_bridge = NULL;
#endif
}

static inline void nf_reset_trace(struct sk_buff *skb)
{
#if IS_ENABLED(CONFIG_NETFILTER_XT_TARGET_TRACE) || defined(CONFIG_NF_TABLES)
	skb->nf_trace = 0;
#endif
}

/* Note: This doesn't put any conntrack and bridge info in dst. */
static inline void __nf_copy(struct sk_buff *dst, const struct sk_buff *src,
			     bool copy)
{
#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
	dst->nfct = src->nfct;
	nf_conntrack_get(src->nfct);
	if (copy)
		dst->nfctinfo = src->nfctinfo;
#endif
#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
	dst->nf_bridge  = src->nf_bridge;
	nf_bridge_get(src->nf_bridge);
#endif
#if IS_ENABLED(CONFIG_NETFILTER_XT_TARGET_TRACE) || defined(CONFIG_NF_TABLES)
	if (copy)
		dst->nf_trace = src->nf_trace;
#endif
}

static inline void nf_copy(struct sk_buff *dst, const struct sk_buff *src)
{
#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
	nf_conntrack_put(dst->nfct);
#endif
#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
	nf_bridge_put(dst->nf_bridge);
#endif
	__nf_copy(dst, src, true);
}

#ifdef CONFIG_NETWORK_SECMARK
static inline void skb_copy_secmark(struct sk_buff *to, const struct sk_buff *from)
{
	to->secmark = from->secmark;
}

static inline void skb_init_secmark(struct sk_buff *skb)
{
	skb->secmark = 0;
}
#else
static inline void skb_copy_secmark(struct sk_buff *to, const struct sk_buff *from)
{ }

static inline void skb_init_secmark(struct sk_buff *skb)
{ }
#endif

static inline bool skb_irq_freeable(const struct sk_buff *skb)
{
	return !skb->destructor &&
#if IS_ENABLED(CONFIG_XFRM)
		!skb->sp &&
#endif
#if IS_ENABLED(CONFIG_NF_CONNTRACK)
		!skb->nfct &&
#endif
		!skb->_skb_refdst &&
		!skb_has_frag_list(skb);
}

static inline void skb_set_queue_mapping(struct sk_buff *skb, u16 queue_mapping)
{
	skb->queue_mapping = queue_mapping;
}

static inline u16 skb_get_queue_mapping(const struct sk_buff *skb)
{
	return skb->queue_mapping;
}

static inline void skb_copy_queue_mapping(struct sk_buff *to, const struct sk_buff *from)
{
	to->queue_mapping = from->queue_mapping;
}

static inline void skb_record_rx_queue(struct sk_buff *skb, u16 rx_queue)
{
	skb->queue_mapping = rx_queue + 1;
}

static inline u16 skb_get_rx_queue(const struct sk_buff *skb)
{
	return skb->queue_mapping - 1;
}

static inline bool skb_rx_queue_recorded(const struct sk_buff *skb)
{
	return skb->queue_mapping != 0;
}

static inline struct sec_path *skb_sec_path(struct sk_buff *skb)
{
#ifdef CONFIG_XFRM
	return skb->sp;
#else
	return NULL;
#endif
}

/* Keeps track of mac header offset relative to skb->head.
 * It is useful for TSO of Tunneling protocol. e.g. GRE.
 * For non-tunnel skb it points to skb_mac_header() and for
 * tunnel skb it points to outer mac header.
 * Keeps track of level of encapsulation of network headers.
 */
struct skb_gso_cb {
	int	mac_offset;
	int	encap_level;
	__u16	csum_start;
};
#define SKB_GSO_CB(skb) ((struct skb_gso_cb *)(skb)->cb)

static inline int skb_tnl_header_len(const struct sk_buff *inner_skb)
{
	return (skb_mac_header(inner_skb) - inner_skb->head) -
		SKB_GSO_CB(inner_skb)->mac_offset;
}

static inline int gso_pskb_expand_head(struct sk_buff *skb, int extra)
{
	int new_headroom, headroom;
	int ret;

	headroom = skb_headroom(skb);
	ret = pskb_expand_head(skb, extra, 0, GFP_ATOMIC);
	if (ret)
		return ret;

	new_headroom = skb_headroom(skb);
	SKB_GSO_CB(skb)->mac_offset += (new_headroom - headroom);
	return 0;
}

/* Compute the checksum for a gso segment. First compute the checksum value
 * from the start of transport header to SKB_GSO_CB(skb)->csum_start, and
 * then add in skb->csum (checksum from csum_start to end of packet).
 * skb->csum and csum_start are then updated to reflect the checksum of the
 * resultant packet starting from the transport header-- the resultant checksum
 * is in the res argument (i.e. normally zero or ~ of checksum of a pseudo
 * header.
 */
static inline __sum16 gso_make_checksum(struct sk_buff *skb, __wsum res)
{
	int plen = SKB_GSO_CB(skb)->csum_start - skb_headroom(skb) -
		   skb_transport_offset(skb);
	__wsum partial;

	partial = csum_partial(skb_transport_header(skb), plen, skb->csum);
	skb->csum = res;
	SKB_GSO_CB(skb)->csum_start -= plen;

	return csum_fold(partial);
}

static inline bool skb_is_gso(const struct sk_buff *skb)
{
	return skb_shinfo(skb)->gso_size;
}

/* Note: Should be called only if skb_is_gso(skb) is true */
static inline bool skb_is_gso_v6(const struct sk_buff *skb)
{
	return skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6;
}

void __skb_warn_lro_forwarding(const struct sk_buff *skb);

static inline bool skb_warn_if_lro(const struct sk_buff *skb)
{
	/* LRO sets gso_size but not gso_type, whereas if GSO is really
	 * wanted then gso_type will be set. */
	const struct skb_shared_info *shinfo = skb_shinfo(skb);

	if (skb_is_nonlinear(skb) && shinfo->gso_size != 0 &&
	    unlikely(shinfo->gso_type == 0)) {
		__skb_warn_lro_forwarding(skb);
		return true;
	}
	return false;
}

static inline void skb_forward_csum(struct sk_buff *skb)
{
	/* Unfortunately we don't support this one.  Any brave souls? */
	if (skb->ip_summed == CHECKSUM_COMPLETE)
		skb->ip_summed = CHECKSUM_NONE;
}

/**
 * skb_checksum_none_assert - make sure skb ip_summed is CHECKSUM_NONE
 * @skb: skb to check
 *
 * fresh skbs have their ip_summed set to CHECKSUM_NONE.
 * Instead of forcing ip_summed to CHECKSUM_NONE, we can
 * use this helper, to document places where we make this assertion.
 */
static inline void skb_checksum_none_assert(const struct sk_buff *skb)
{
#ifdef DEBUG
	BUG_ON(skb->ip_summed != CHECKSUM_NONE);
#endif
}

bool skb_partial_csum_set(struct sk_buff *skb, u16 start, u16 off);

int skb_checksum_setup(struct sk_buff *skb, bool recalculate);
struct sk_buff *skb_checksum_trimmed(struct sk_buff *skb,
				     unsigned int transport_len,
				     __sum16(*skb_chkf)(struct sk_buff *skb));

/**
 * skb_head_is_locked - Determine if the skb->head is locked down
 * @skb: skb to check
 *
 * The head on skbs build around a head frag can be removed if they are
 * not cloned.  This function returns true if the skb head is locked down
 * due to either being allocated via kmalloc, or by being a clone with
 * multiple references to the head.
 */
static inline bool skb_head_is_locked(const struct sk_buff *skb)
{
	return !skb->head_frag || skb_cloned(skb);
}

/**
 * skb_gso_network_seglen - Return length of individual segments of a gso packet
 *
 * @skb: GSO skb
 *
 * skb_gso_network_seglen is used to determine the real size of the
 * individual segments, including Layer3 (IP, IPv6) and L4 headers (TCP/UDP).
 *
 * The MAC/L2 header is not accounted for.
 */
static inline unsigned int skb_gso_network_seglen(const struct sk_buff *skb)
{
	unsigned int hdr_len = skb_transport_header(skb) -
			       skb_network_header(skb);
	return hdr_len + skb_gso_transport_seglen(skb);
}
#endif	/* __KERNEL__ */
#endif	/* _LINUX_SKBUFF_H */