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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/compiler.h>
#include <linux/time.h>
#include <linux/cache.h>

#include <asm/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/dmaengine.h>
#include <linux/hrtimer.h>

#define HAVE_ALLOC_SKB        /* For the drivers to know */
#define HAVE_ALIGNABLE_SKB    /* Ditto 8)          */

/* 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

#define SKB_DATA_ALIGN(X)     (((X) + (SMP_CACHE_BYTES - 1)) & \
                         ~(SMP_CACHE_BYTES - 1))
#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))

/* A. Checksumming of received packets by device.
 *
 *    NONE: device failed to checksum this packet.
 *          skb->csum is undefined.
 *
 *    UNNECESSARY: device parsed packet and wouldbe verified checksum.
 *          skb->csum is undefined.
 *          It is bad option, but, unfortunately, many of vendors do this.
 *          Apparently with secret goal to sell you new device, when you
 *          will add new protocol to your host. F.e. IPv6. 8)
 *
 *    COMPLETE: the most generic way. Device supplied checksum of _all_
 *        the packet as seen by netif_rx in skb->csum.
 *        NOTE: Even if device supports only some protocols, but
 *        is able to produce some skb->csum, it MUST use COMPLETE,
 *        not UNNECESSARY.
 *
 *    PARTIAL: identical to the case for output below.  This may occur
 *        on a packet received directly from another Linux OS, e.g.,
 *        a virtualised Linux kernel on the same host.  The packet can
 *        be treated in the same way as UNNECESSARY except that on
 *        output (i.e., forwarding) the checksum must be filled in
 *        by the OS or the hardware.
 *
 * B. Checksumming on output.
 *
 *    NONE: skb is checksummed by protocol or csum is not required.
 *
 *    PARTIAL: device is required to csum packet as seen by hard_start_xmit
 *    from skb->csum_start to the end and to record the checksum
 *    at skb->csum_start + skb->csum_offset.
 *
 *    Device must show its capabilities in dev->features, set
 *    at device setup time.
 *    NETIF_F_HW_CSUM   - it is clever device, it is able to checksum
 *                  everything.
 *    NETIF_F_NO_CSUM - loopback or reliable single hop media.
 *    NETIF_F_IP_CSUM - device is dumb. It is able to csum only
 *                  TCP/UDP over IPv4. Sigh. Vendors like this
 *                  way by 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.
 *
 *    Any questions? No questions, good.        --ANK
 */

struct net_device;
struct scatterlist;

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

#ifdef CONFIG_BRIDGE_NETFILTER
struct nf_bridge_info {
      atomic_t use;
      struct net_device *physindev;
      struct net_device *physoutdev;
#if defined(CONFIG_VLAN_8021Q) || defined(CONFIG_VLAN_8021Q_MODULE)
      struct net_device *netoutdev;
#endif
      unsigned int mask;
      unsigned long data[32 / sizeof(unsigned long)];
};
#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 */
#define MAX_SKB_FRAGS (65536/PAGE_SIZE + 2)

typedef struct skb_frag_struct skb_frag_t;

struct skb_frag_struct {
      struct page *page;
      __u32 page_offset;
      __u32 size;
};

/* This data is invariant across clones and lives at
 * the end of the header data, ie. at skb->end.
 */
struct skb_shared_info {
      atomic_t    dataref;
      unsigned short    nr_frags;
      unsigned short    gso_size;
      /* Warning: this field is not always filled in (UFO)! */
      unsigned short    gso_segs;
      unsigned short  gso_type;
      __be32          ip6_frag_id;
      struct sk_buff    *frag_list;
      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_FCLONE_ORIG,
      SKB_FCLONE_CLONE,
};

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,
};

#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 sk_buff - socket buffer
 *    @next: Next buffer in list
 *    @prev: Previous buffer in list
 *    @sk: Socket we are owned by
 *    @tstamp: Time we arrived
 *    @dev: Device we arrived on/are leaving by
 *    @transport_header: Transport layer header
 *    @network_header: Network layer header
 *    @mac_header: Link layer header
 *    @dst: destination entry
 *    @sp: the security path, used for xfrm
 *    @cb: Control buffer. Free for use by every layer. Put private vars here
 *    @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
 *    @local_df: allow local fragmentation
 *    @cloned: Head may be cloned (check refcnt to be sure)
 *    @nohdr: Payload reference only, must not modify header
 *    @pkt_type: Packet class
 *    @fclone: skbuff clone status
 *    @ip_summed: Driver fed us an IP checksum
 *    @priority: Packet queueing priority
 *    @users: User count - see {datagram,tcp}.c
 *    @protocol: Packet protocol from driver
 *    @truesize: Buffer size 
 *    @head: Head of buffer
 *    @data: Data head pointer
 *    @tail: Tail pointer
 *    @end: End pointer
 *    @destructor: Destruct function
 *    @mark: Generic packet mark
 *    @nfct: Associated connection, if any
 *    @ipvs_property: skbuff is owned by ipvs
 *    @nf_trace: netfilter packet trace flag
 *    @nfctinfo: Relationship of this skb to the connection
 *    @nfct_reasm: netfilter conntrack re-assembly pointer
 *    @nf_bridge: Saved data about a bridged frame - see br_netfilter.c
 *    @iif: ifindex of device we arrived on
 *    @queue_mapping: Queue mapping for multiqueue devices
 *    @tc_index: Traffic control index
 *    @tc_verd: traffic control verdict
 *    @dma_cookie: a cookie to one of several possible DMA operations
 *          done by skb DMA functions
 *    @secmark: security marking
 */

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

      struct sock       *sk;
      ktime_t                 tstamp;
      struct net_device *dev;

      struct  dst_entry *dst;
      struct      sec_path    *sp;

      /*
       * 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];

      unsigned int            len,
                        data_len;
      __u16             mac_len,
                        hdr_len;
      union {
            __wsum            csum;
            struct {
                  __u16 csum_start;
                  __u16 csum_offset;
            };
      };
      __u32             priority;
      __u8              local_df:1,
                        cloned:1,
                        ip_summed:2,
                        nohdr:1,
                        nfctinfo:3;
      __u8              pkt_type:3,
                        fclone:2,
                        ipvs_property:1,
                        nf_trace:1;
      __be16                  protocol;

      void              (*destructor)(struct sk_buff *skb);
#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
      struct nf_conntrack     *nfct;
      struct sk_buff          *nfct_reasm;
#endif
#ifdef CONFIG_BRIDGE_NETFILTER
      struct nf_bridge_info   *nf_bridge;
#endif

      int               iif;
#ifdef CONFIG_NETDEVICES_MULTIQUEUE
      __u16             queue_mapping;
#endif
#ifdef CONFIG_NET_SCHED
      __u16             tc_index;   /* traffic control index */
#ifdef CONFIG_NET_CLS_ACT
      __u16             tc_verd;    /* traffic control verdict */
#endif
#endif
      /* 2 byte hole */

#ifdef CONFIG_NET_DMA
      dma_cookie_t            dma_cookie;
#endif
#ifdef CONFIG_NETWORK_SECMARK
      __u32             secmark;
#endif

      __u32             mark;

      sk_buff_data_t          transport_header;
      sk_buff_data_t          network_header;
      sk_buff_data_t          mac_header;
      /* 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>

#include <asm/system.h>

extern void kfree_skb(struct sk_buff *skb);
extern void        __kfree_skb(struct sk_buff *skb);
extern struct sk_buff *__alloc_skb(unsigned int size,
                           gfp_t priority, int fclone, int node);
static inline struct sk_buff *alloc_skb(unsigned int size,
                              gfp_t priority)
{
      return __alloc_skb(size, priority, 0, -1);
}

static inline struct sk_buff *alloc_skb_fclone(unsigned int size,
                                     gfp_t priority)
{
      return __alloc_skb(size, priority, 1, -1);
}

extern struct sk_buff *skb_morph(struct sk_buff *dst, struct sk_buff *src);
extern struct sk_buff *skb_clone(struct sk_buff *skb,
                         gfp_t priority);
extern struct sk_buff *skb_copy(const struct sk_buff *skb,
                        gfp_t priority);
extern struct sk_buff *pskb_copy(struct sk_buff *skb,
                         gfp_t gfp_mask);
extern int         pskb_expand_head(struct sk_buff *skb,
                              int nhead, int ntail,
                              gfp_t gfp_mask);
extern struct sk_buff *skb_realloc_headroom(struct sk_buff *skb,
                                  unsigned int headroom);
extern struct sk_buff *skb_copy_expand(const struct sk_buff *skb,
                               int newheadroom, int newtailroom,
                               gfp_t priority);
extern int         skb_to_sgvec(struct sk_buff *skb,
                            struct scatterlist *sg, int offset,
                            int len);
extern int         skb_cow_data(struct sk_buff *skb, int tailbits,
                            struct sk_buff **trailer);
extern int         skb_pad(struct sk_buff *skb, int pad);
#define dev_kfree_skb(a)      kfree_skb(a)
extern void       skb_over_panic(struct sk_buff *skb, int len,
                             void *here);
extern void       skb_under_panic(struct sk_buff *skb, int len,
                              void *here);
extern void       skb_truesize_bug(struct sk_buff *skb);

static inline void skb_truesize_check(struct sk_buff *skb)
{
      int len = sizeof(struct sk_buff) + skb->len;

      if (unlikely((int)skb->truesize < len))
            skb_truesize_bug(skb);
}

extern 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);

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;
};

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

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

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

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

/**
 *    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 == (struct sk_buff *)list;
}

/**
 *    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;
}

/**
 *    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.
 */
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_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);
            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);
            kfree_skb(skb);   /* Free our shared copy */
            skb = nskb;
      }
      return skb;
}

/**
 *    skb_peek
 *    @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(struct sk_buff_head *list_)
{
      struct sk_buff *list = ((struct sk_buff *)list_)->next;
      if (list == (struct sk_buff *)list_)
            list = NULL;
      return list;
}

/**
 *    skb_peek_tail
 *    @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(struct sk_buff_head *list_)
{
      struct sk_buff *list = ((struct sk_buff *)list_)->prev;
      if (list == (struct sk_buff *)list_)
            list = NULL;
      return list;
}

/**
 *    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;
}

/*
 * 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);
      list->prev = list->next = (struct sk_buff *)list;
      list->qlen = 0;
}

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 at the start of a list.
 *
 *    The "__skb_xxxx()" functions are the non-atomic ones that
 *    can only be called with interrupts disabled.
 */

/**
 *    __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)
{
      struct sk_buff *next;
      list->qlen++;

      next = prev->next;
      newsk->next = next;
      newsk->prev = prev;
      next->prev  = prev->next = newsk;
}

/**
 *    __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.
 */
extern 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.
 */
extern 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)
{
      struct sk_buff *prev, *next;

      list->qlen++;
      next = (struct sk_buff *)list;
      prev = next->prev;
      newsk->next = next;
      newsk->prev = prev;
      next->prev  = prev->next = newsk;
}


/**
 *    __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.
 */
extern 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 *next, *prev, *result;

      prev = (struct sk_buff *) list;
      next = prev->next;
      result = NULL;
      if (next != prev) {
            result           = next;
            next       = next->next;
            list->qlen--;
            next->prev   = prev;
            prev->next   = next;
            result->next = result->prev = NULL;
      }
      return result;
}


/*
 *    Insert a packet on a list.
 */
extern 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++;
}

/*
 *    Place a packet after a given packet in a list.
 */
extern void    skb_append(struct sk_buff *old, struct sk_buff *newsk, struct sk_buff_head *list);
static inline void __skb_append(struct sk_buff *old, struct sk_buff *newsk, struct sk_buff_head *list)
{
      __skb_insert(newsk, old, old->next, list);
}

/*
 * remove sk_buff from list. _Must_ be called atomically, and with
 * the list known..
 */
extern 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;
}


/* XXX: more streamlined implementation */

/**
 *    __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.
 */
extern 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 int 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_shinfo(skb)->frags[i].size;
      return len + skb_headlen(skb);
}

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];

      frag->page          = page;
      frag->page_offset   = off;
      frag->size          = size;
      skb_shinfo(skb)->nr_frags = i + 1;
}

#define SKB_PAGE_ASSERT(skb)  BUG_ON(skb_shinfo(skb)->nr_frags)
#define SKB_FRAG_ASSERT(skb)  BUG_ON(skb_shinfo(skb)->frag_list)
#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
 */
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;
}

/**
 *    skb_put - add data to a buffer
 *    @skb: buffer to use
 *    @len: amount of data to add
 *
 *    This function extends the used data area of the buffer. If this would
 *    exceed the total buffer size the kernel will panic. A pointer to the
 *    first byte of the extra data is returned.
 */
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;
      if (unlikely(skb->tail > skb->end))
            skb_over_panic(skb, len, current_text_addr());
      return tmp;
}

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

/**
 *    skb_push - add data to the start of a buffer
 *    @skb: buffer to use
 *    @len: amount of data to add
 *
 *    This function extends the used data area of the buffer at the buffer
 *    start. If this would exceed the total buffer headroom the kernel will
 *    panic. A pointer to the first byte of the extra data is returned.
 */
static inline unsigned char *skb_push(struct sk_buff *skb, unsigned int len)
{
      skb->data -= len;
      skb->len  += len;
      if (unlikely(skb->data<skb->head))
            skb_under_panic(skb, len, current_text_addr());
      return skb->data;
}

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;
}

/**
 *    skb_pull - remove data from the start of a buffer
 *    @skb: buffer to use
 *    @len: amount of data to remove
 *
 *    This function removes data from the start of a buffer, returning
 *    the memory to the headroom. A pointer to the next data in the buffer
 *    is returned. Once the data has been pulled future pushes will overwrite
 *    the old data.
 */
static inline unsigned char *skb_pull(struct sk_buff *skb, unsigned int len)
{
      return unlikely(len > skb->len) ? NULL : __skb_pull(skb, len);
}

extern 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_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;
}

#ifdef NET_SKBUFF_DATA_USES_OFFSET
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 != ~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;
}

#else /* NET_SKBUFF_DATA_USES_OFFSET */

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

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

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

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

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

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

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

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

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

static inline void skb_set_mac_header(struct sk_buff *skb, const int offset)
{
      skb->mac_header = skb->data + offset;
}
#endif /* NET_SKBUFF_DATA_USES_OFFSET */

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

/*
 * 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(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
 * 16 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 16 bytes of
 * headroom, you should not reduce this.
 */
#ifndef NET_SKB_PAD
#define NET_SKB_PAD     16
#endif

extern 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->data_len)) {
            WARN_ON(1);
            return;
      }
      skb->len = len;
      skb_set_tail_pointer(skb, len);
}

/**
 *    skb_trim - remove end from a buffer
 *    @skb: buffer to alter
 *    @len: new length
 *
 *    Cut the length of a buffer down by removing data from the tail. If
 *    the buffer is already under the length specified it is not modified.
 *    The skb must be linear.
 */
static inline void skb_trim(struct sk_buff *skb, unsigned int len)
{
      if (skb->len > len)
            __skb_trim(skb, 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;
}

/**
 *    __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.
 */
extern 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);
}

/**
 *    __dev_alloc_skb - allocate an skbuff for receiving
 *    @length: length to allocate
 *    @gfp_mask: get_free_pages mask, passed to alloc_skb
 *
 *    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.
 */
static inline struct sk_buff *__dev_alloc_skb(unsigned int length,
                                    gfp_t gfp_mask)
{
      struct sk_buff *skb = alloc_skb(length + NET_SKB_PAD, gfp_mask);
      if (likely(skb))
            skb_reserve(skb, NET_SKB_PAD);
      return skb;
}

/**
 *    dev_alloc_skb - allocate an skbuff for receiving
 *    @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 *dev_alloc_skb(unsigned int length)
{
      return __dev_alloc_skb(length, GFP_ATOMIC);
}

extern 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);
}

/**
 *    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(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 < NET_SKB_PAD)
            headroom = NET_SKB_PAD;
      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);
}

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

      if (skb->ip_summed == CHECKSUM_NONE) {
            int err = 0;
            __wsum csum = csum_and_copy_from_user(from, skb_put(skb, copy),
                                              copy, 0, &err);
            if (!err) {
                  skb->csum = csum_block_add(skb->csum, csum, off);
                  return 0;
            }
      } else if (!copy_from_user(skb_put(skb, copy), from, copy))
            return 0;

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

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

            return page == frag->page &&
                   off == frag->page_offset + frag->size;
      }
      return 0;
}

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_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;                             \
                 prefetch(skb->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_reverse_walk(queue, skb) \
            for (skb = (queue)->prev;                             \
                 prefetch(skb->prev), (skb != (struct sk_buff *)(queue));     \
                 skb = skb->prev)


extern struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned flags,
                               int noblock, int *err);
extern unsigned int    datagram_poll(struct file *file, struct socket *sock,
                             struct poll_table_struct *wait);
extern int         skb_copy_datagram_iovec(const struct sk_buff *from,
                                     int offset, struct iovec *to,
                                     int size);
extern int         skb_copy_and_csum_datagram_iovec(struct sk_buff *skb,
                                          int hlen,
                                          struct iovec *iov);
extern void        skb_free_datagram(struct sock *sk, struct sk_buff *skb);
extern void        skb_kill_datagram(struct sock *sk, struct sk_buff *skb,
                               unsigned int flags);
extern __wsum            skb_checksum(const struct sk_buff *skb, int offset,
                            int len, __wsum csum);
extern int         skb_copy_bits(const struct sk_buff *skb, int offset,
                             void *to, int len);
extern int         skb_store_bits(struct sk_buff *skb, int offset,
                              const void *from, int len);
extern __wsum            skb_copy_and_csum_bits(const struct sk_buff *skb,
                                    int offset, u8 *to, int len,
                                    __wsum csum);
extern void        skb_copy_and_csum_dev(const struct sk_buff *skb, u8 *to);
extern void        skb_split(struct sk_buff *skb,
                         struct sk_buff *skb1, const u32 len);

extern struct sk_buff *skb_segment(struct sk_buff *skb, int features);

static inline void *skb_header_pointer(const struct sk_buff *skb, int offset,
                               int len, void *buffer)
{
      int hlen = skb_headlen(skb);

      if (hlen - offset >= len)
            return skb->data + offset;

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

      return buffer;
}

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);
}

extern void skb_init(void);

/**
 *    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 __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);
}

extern __sum16 __skb_checksum_complete_head(struct sk_buff *skb, int len);
extern __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_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);
}

#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
extern 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);
}
static inline void nf_conntrack_get_reasm(struct sk_buff *skb)
{
      if (skb)
            atomic_inc(&skb->users);
}
static inline void nf_conntrack_put_reasm(struct sk_buff *skb)
{
      if (skb)
            kfree_skb(skb);
}
#endif
#ifdef 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;
      nf_conntrack_put_reasm(skb->nfct_reasm);
      skb->nfct_reasm = NULL;
#endif
#ifdef CONFIG_BRIDGE_NETFILTER
      nf_bridge_put(skb->nf_bridge);
      skb->nf_bridge = NULL;
#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)
{
#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
      dst->nfct = src->nfct;
      nf_conntrack_get(src->nfct);
      dst->nfctinfo = src->nfctinfo;
      dst->nfct_reasm = src->nfct_reasm;
      nf_conntrack_get_reasm(src->nfct_reasm);
#endif
#ifdef CONFIG_BRIDGE_NETFILTER
      dst->nf_bridge  = src->nf_bridge;
      nf_bridge_get(src->nf_bridge);
#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);
      nf_conntrack_put_reasm(dst->nfct_reasm);
#endif
#ifdef CONFIG_BRIDGE_NETFILTER
      nf_bridge_put(dst->nf_bridge);
#endif
      __nf_copy(dst, src);
}

#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 void skb_set_queue_mapping(struct sk_buff *skb, u16 queue_mapping)
{
#ifdef CONFIG_NETDEVICES_MULTIQUEUE
      skb->queue_mapping = queue_mapping;
#endif
}

static inline u16 skb_get_queue_mapping(struct sk_buff *skb)
{
#ifdef CONFIG_NETDEVICES_MULTIQUEUE
      return skb->queue_mapping;
#else
      return 0;
#endif
}

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

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

static inline int skb_is_gso_v6(const struct sk_buff *skb)
{
      return skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6;
}

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;
}

#endif      /* __KERNEL__ */
#endif      /* _LINUX_SKBUFF_H */

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