TOMOYO Linux Cross Reference
Linux/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/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>
  #include <linux/dma-mapping.h>
  #include <linux/netdev_features.h>
  #include <net/flow_keys.h>
  
  /* 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))
  
  /* 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)))
  
  /* 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_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.
   *
   *      UNNECESSARY: device will do per protocol specific csum. Protocol drivers
  *      that do not want net to perform the checksum calculation should use
  *      this flag in their outgoing skbs.
  *      NETIF_F_FCOE_CRC  this indicates the device can do FCoE FC CRC
  *                        offload. Correspondingly, the FCoE protocol driver
  *                        stack should use CHECKSUM_UNNECESSARY.
  *
  *      Any questions? No questions, good.              --ANK
  */
 
 struct net_device;
 struct scatterlist;
 struct pipe_inode_info;
 
 #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;
         unsigned int            mask;
         struct net_device       *physindev;
         struct net_device       *physoutdev;
         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 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
  * @syststamp:  hwtstamp transformed to system time base
  *
  * Software time stamps generated by ktime_get_real() are stored in
  * skb->tstamp. The relation between the different kinds of time
  * stamps is as follows:
  *
  * syststamp and tstamp can be compared against each other in
  * arbitrary combinations.  The accuracy of a
  * syststamp/tstamp/"syststamp from other device" comparison is
  * limited by the accuracy of the transformation into system time
  * base. This depends on the device driver and its underlying
  * hardware.
  *
  * 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;
         ktime_t syststamp;
 };
 
 /* Definitions for tx_flags in struct skb_shared_info */
 enum {
         /* generate hardware time stamp */
         SKBTX_HW_TSTAMP = 1 << 0,
 
         /* generate software time stamp */
         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,
 };
 
 /*
  * 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;
         __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_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,
 
         SKB_GSO_FCOE = 1 << 5,
 
         SKB_GSO_GRE = 1 << 6,
 
         SKB_GSO_UDP_TUNNEL = 1 << 7,
 
         SKB_GSO_MPLS = 1 << 8,
 };
 
 #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
 
 #if defined(CONFIG_NF_DEFRAG_IPV4) || defined(CONFIG_NF_DEFRAG_IPV4_MODULE) || \
     defined(CONFIG_NF_DEFRAG_IPV6) || defined(CONFIG_NF_DEFRAG_IPV6_MODULE)
 #define NET_SKBUFF_NF_DEFRAG_NEEDED 1
 #endif
 
 /** 
  *      struct sk_buff - socket buffer
  *      @next: Next buffer in list
  *      @prev: Previous buffer in list
  *      @tstamp: Time we arrived
  *      @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
  *      @local_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
  *      @nfct_reasm: netfilter conntrack re-assembly pointer
  *      @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
  *      @rxhash: the packet hash computed on receive
  *      @queue_mapping: Queue mapping for multiqueue devices
  *      @ndisc_nodetype: router type (from link layer)
  *      @ooo_okay: allow the mapping of a socket to a queue to be changed
  *      @l4_rxhash: indicate rxhash is a canonical 4-tuple hash over transport
  *              ports.
  *      @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
  *      @dma_cookie: a cookie to one of several possible DMA operations
  *              done by skb DMA functions
   *     @napi_id: id of the NAPI struct this skb came from
  *      @secmark: security marking
  *      @mark: Generic packet mark
  *      @dropcount: total number of sk_receive_queue overflows
  *      @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 {
         /* These two members must be first. */
         struct sk_buff          *next;
         struct sk_buff          *prev;
 
         ktime_t                 tstamp;
 
         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;
 #ifdef CONFIG_XFRM
         struct  sec_path        *sp;
 #endif
         unsigned int            len,
                                 data_len;
         __u16                   mac_len,
                                 hdr_len;
         union {
                 __wsum          csum;
                 struct {
                         __u16   csum_start;
                         __u16   csum_offset;
                 };
         };
         __u32                   priority;
         kmemcheck_bitfield_begin(flags1);
         __u8                    local_df:1,
                                 cloned:1,
                                 ip_summed:2,
                                 nohdr:1,
                                 nfctinfo:3;
         __u8                    pkt_type:3,
                                 fclone:2,
                                 ipvs_property:1,
                                 peeked:1,
                                 nf_trace:1;
         kmemcheck_bitfield_end(flags1);
         __be16                  protocol;
 
         void                    (*destructor)(struct sk_buff *skb);
 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
         struct nf_conntrack     *nfct;
 #endif
 #ifdef NET_SKBUFF_NF_DEFRAG_NEEDED
         struct sk_buff          *nfct_reasm;
 #endif
 #ifdef CONFIG_BRIDGE_NETFILTER
         struct nf_bridge_info   *nf_bridge;
 #endif
 
         int                     skb_iif;
 
         __u32                   rxhash;
 
         __be16                  vlan_proto;
         __u16                   vlan_tci;
 
 #ifdef CONFIG_NET_SCHED
         __u16                   tc_index;       /* traffic control index */
 #ifdef CONFIG_NET_CLS_ACT
         __u16                   tc_verd;        /* traffic control verdict */
 #endif
 #endif
 
         __u16                   queue_mapping;
         kmemcheck_bitfield_begin(flags2);
 #ifdef CONFIG_IPV6_NDISC_NODETYPE
         __u8                    ndisc_nodetype:2;
 #endif
         __u8                    pfmemalloc:1;
         __u8                    ooo_okay:1;
         __u8                    l4_rxhash:1;
         __u8                    wifi_acked_valid:1;
         __u8                    wifi_acked:1;
         __u8                    no_fcs:1;
         __u8                    head_frag:1;
         /* Encapsulation protocol and NIC drivers should use
          * this flag to indicate to each other if the skb contains
          * encapsulated packet or not and maybe use the inner packet
          * headers if needed
          */
         __u8                    encapsulation:1;
         /* 7/9 bit hole (depending on ndisc_nodetype presence) */
         kmemcheck_bitfield_end(flags2);
 
 #if defined CONFIG_NET_DMA || defined CONFIG_NET_RX_BUSY_POLL
         union {
                 unsigned int    napi_id;
                 dma_cookie_t    dma_cookie;
         };
 #endif
 #ifdef CONFIG_NETWORK_SECMARK
         __u32                   secmark;
 #endif
         union {
                 __u32           mark;
                 __u32           dropcount;
                 __u32           reserved_tailroom;
         };
 
         __be16                  inner_protocol;
         __u16                   inner_transport_header;
         __u16                   inner_network_header;
         __u16                   inner_mac_header;
         __u16                   transport_header;
         __u16                   network_header;
         __u16                   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>
 
 
 #define SKB_ALLOC_FCLONE        0x01
 #define SKB_ALLOC_RX            0x02
 
 /* 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;
 }
 
 extern void __skb_dst_set_noref(struct sk_buff *skb, struct dst_entry *dst,
                                 bool force);
 
 /**
  * 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)
 {
         __skb_dst_set_noref(skb, dst, false);
 }
 
 /**
  * skb_dst_set_noref_force - sets skb dst, without taking reference
  * @skb: buffer
  * @dst: dst entry
  *
  * Sets skb dst, assuming a reference was not taken on dst.
  * No reference is taken and no dst_release will be called. While for
  * cached dsts deferred reclaim is a basic feature, for entries that are
  * not cached it is caller's job to guarantee that last dst_release for
  * provided dst happens when nobody uses it, eg. after a RCU grace period.
  */
 static inline void skb_dst_set_noref_force(struct sk_buff *skb,
                                            struct dst_entry *dst)
 {
         __skb_dst_set_noref(skb, dst, true);
 }
 
 /**
  * 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);
 }
 
 extern void kfree_skb(struct sk_buff *skb);
 extern void kfree_skb_list(struct sk_buff *segs);
 extern void skb_tx_error(struct sk_buff *skb);
 extern void consume_skb(struct sk_buff *skb);
 extern void            __kfree_skb(struct sk_buff *skb);
 extern struct kmem_cache *skbuff_head_cache;
 
 extern void kfree_skb_partial(struct sk_buff *skb, bool head_stolen);
 extern bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from,
                              bool *fragstolen, int *delta_truesize);
 
 extern struct sk_buff *__alloc_skb(unsigned int size,
                                    gfp_t priority, int flags, int node);
 extern 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);
 }
 
 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);
 }
 
 extern 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);
 }
 
 extern struct sk_buff *skb_morph(struct sk_buff *dst, struct sk_buff *src);
 extern int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask);
 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,
                                  int headroom, 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)        consume_skb(a)
 
 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);
 
 extern void __skb_get_rxhash(struct sk_buff *skb);
 static inline __u32 skb_get_rxhash(struct sk_buff *skb)
 {
         if (!skb->l4_rxhash)
                 __skb_get_rxhash(skb);
 
         return skb->rxhash;
 }
 
 #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 == (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 == (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 == (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.
  */
 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);
 
                 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);
                 kfree_skb(skb); /* Free our shared copy */
                 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.
  */
 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++;
 }
 
 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);
 }
 
 extern 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.
  */
 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)
 {
         __skb_queue_before(list, (struct sk_buff *)list, newsk);
 }
 
 /*
  * 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;
 }
 
 /**
  *      __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 *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.
  */
 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 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);
 }
 
 static inline bool skb_has_frags(const struct sk_buff *skb)
 {
         return skb_shinfo(skb)->nr_frags;
 }
 
 /**
  * __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;
 }
 
 extern void skb_add_rx_frag(struct sk_buff *skb, int i, struct page *page,
                             int off, 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
  */
 extern 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;
 }
 
 extern 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;
 }
 
 extern 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);
 }
 
 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_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;
 }
 
 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_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(skb, &keys))
                 skb_set_transport_header(skb, keys.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
 
 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_is_nonlinear(skb))) {
                 WARN_ON(1);
                 return;
         }
         skb->len = len;
         skb_set_tail_pointer(skb, len);
 }
 
 extern 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;
 }
 
 /**
  *      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.
  */
 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);
 }
 
 #define NETDEV_FRAG_PAGE_MAX_ORDER get_order(32768)
 #define NETDEV_FRAG_PAGE_MAX_SIZE  (PAGE_SIZE << NETDEV_FRAG_PAGE_MAX_ORDER)
 #define NETDEV_PAGECNT_MAX_BIAS    NETDEV_FRAG_PAGE_MAX_SIZE
 
 extern void *netdev_alloc_frag(unsigned int fragsz);
 
 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);
 }
 
 /* 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);
 }
 
 /*
  *      __skb_alloc_page - allocate pages for ps-rx on a skb and preserve pfmemalloc data
  *      @gfp_mask: alloc_pages_node mask. Set __GFP_NOMEMALLOC if not for network packet RX
  *      @skb: skb to set pfmemalloc on if __GFP_MEMALLOC is used
  *      @order: size of the allocation
  *
  *      Allocate a new page.
  *
  *      %NULL is returned if there is no free memory.
 */
 static inline struct page *__skb_alloc_pages(gfp_t gfp_mask,
                                               struct sk_buff *skb,
                                               unsigned int order)
 {
         struct page *page;
 
         gfp_mask |= __GFP_COLD;
 
         if (!(gfp_mask & __GFP_NOMEMALLOC))
                 gfp_mask |= __GFP_MEMALLOC;
 
         page = alloc_pages_node(NUMA_NO_NODE, gfp_mask, order);
         if (skb && page && page->pfmemalloc)
                 skb->pfmemalloc = true;
 
         return page;
 }
 
 /**
  *      __skb_alloc_page - allocate a page for ps-rx for a given skb and preserve pfmemalloc data
  *      @gfp_mask: alloc_pages_node mask. Set __GFP_NOMEMALLOC if not for network packet RX
  *      @skb: skb to set pfmemalloc on if __GFP_MEMALLOC is used
  *
  *      Allocate a new page.
  *
  *      %NULL is returned if there is no free memory.
  */
 static inline struct page *__skb_alloc_page(gfp_t gfp_mask,
                                              struct sk_buff *skb)
 {
         return __skb_alloc_pages(gfp_mask, skb, 0);
 }
 
 /**
  *      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 refered 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);
 }
 
 /**
  * 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);
 }
 
 /**
  *      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);
 }
 
 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 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)
 
 extern struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned flags,
                                            int *peeked, int *off, int *err);
 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 int             skb_copy_datagram_from_iovec(struct sk_buff *skb,
                                                     int offset,
                                                     const struct iovec *from,
                                                     int from_offset,
                                                     int len);
 extern int             skb_copy_datagram_const_iovec(const struct sk_buff *from,
                                                      int offset,
                                                      const struct iovec *to,
                                                      int to_offset,
                                                      int size);
 extern void            skb_free_datagram(struct sock *sk, struct sk_buff *skb);
 extern void            skb_free_datagram_locked(struct sock *sk,
                                                 struct sk_buff *skb);
 extern int             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 int             skb_splice_bits(struct sk_buff *skb,
                                                 unsigned int offset,
                                                 struct pipe_inode_info *pipe,
                                                 unsigned int len,
                                                 unsigned int flags);
 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 int             skb_shift(struct sk_buff *tgt, struct sk_buff *skb,
                                  int shiftlen);
 extern void            skb_scrub_packet(struct sk_buff *skb);
 
 extern struct sk_buff *skb_segment(struct sk_buff *skb,
                                    netdev_features_t 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);
 
 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);
 }
 
 extern void skb_timestamping_init(void);
 
 #ifdef CONFIG_NETWORK_PHY_TIMESTAMPING
 
 extern void skb_clone_tx_timestamp(struct sk_buff *skb);
 extern 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);
 
 /**
  * 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.
  */
 extern 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.
  *
  * @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);
 
 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);
 }
 #endif
 #ifdef NET_SKBUFF_NF_DEFRAG_NEEDED
 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;
 #endif
 #ifdef NET_SKBUFF_NF_DEFRAG_NEEDED
         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
 }
 
 static inline void nf_reset_trace(struct sk_buff *skb)
 {
 #if IS_ENABLED(CONFIG_NETFILTER_XT_TARGET_TRACE)
         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)
 {
 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
         dst->nfct = src->nfct;
         nf_conntrack_get(src->nfct);
         dst->nfctinfo = src->nfctinfo;
 #endif
 #ifdef NET_SKBUFF_NF_DEFRAG_NEEDED
         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);
 #endif
 #ifdef NET_SKBUFF_NF_DEFRAG_NEEDED
         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)
 {
         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;
 }
 
 extern u16 __skb_tx_hash(const struct net_device *dev,
                          const struct sk_buff *skb,
                          unsigned int num_tx_queues);
 
 #ifdef CONFIG_XFRM
 static inline struct sec_path *skb_sec_path(struct sk_buff *skb)
 {
         return skb->sp;
 }
 #else
 static inline struct sec_path *skb_sec_path(struct sk_buff *skb)
 {
         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. */
 struct skb_gso_cb {
         int mac_offset;
 };
 #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;
 }
 
 static inline bool skb_is_gso(const struct sk_buff *skb)
 {
         return skb_shinfo(skb)->gso_size;
 }
 
 static inline bool skb_is_gso_v6(const struct sk_buff *skb)
 {
         return skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6;
 }
 
 extern 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);
 
 u32 __skb_get_poff(const 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);
 }
 #endif  /* __KERNEL__ */
 #endif  /* _LINUX_SKBUFF_H */
 

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