linux/include/linux/skbuff.h
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   1/*
   2 *      Definitions for the 'struct sk_buff' memory handlers.
   3 *
   4 *      Authors:
   5 *              Alan Cox, <gw4pts@gw4pts.ampr.org>
   6 *              Florian La Roche, <rzsfl@rz.uni-sb.de>
   7 *
   8 *      This program is free software; you can redistribute it and/or
   9 *      modify it under the terms of the GNU General Public License
  10 *      as published by the Free Software Foundation; either version
  11 *      2 of the License, or (at your option) any later version.
  12 */
  13
  14#ifndef _LINUX_SKBUFF_H
  15#define _LINUX_SKBUFF_H
  16
  17#include <linux/kernel.h>
  18#include <linux/compiler.h>
  19#include <linux/time.h>
  20#include <linux/cache.h>
  21
  22#include <asm/atomic.h>
  23#include <asm/types.h>
  24#include <linux/spinlock.h>
  25#include <linux/net.h>
  26#include <linux/textsearch.h>
  27#include <net/checksum.h>
  28#include <linux/rcupdate.h>
  29#include <linux/dmaengine.h>
  30#include <linux/hrtimer.h>
  31
  32#define HAVE_ALLOC_SKB          /* For the drivers to know */
  33#define HAVE_ALIGNABLE_SKB      /* Ditto 8)                */
  34
  35/* Don't change this without changing skb_csum_unnecessary! */
  36#define CHECKSUM_NONE 0
  37#define CHECKSUM_UNNECESSARY 1
  38#define CHECKSUM_COMPLETE 2
  39#define CHECKSUM_PARTIAL 3
  40
  41#define SKB_DATA_ALIGN(X)       (((X) + (SMP_CACHE_BYTES - 1)) & \
  42                                 ~(SMP_CACHE_BYTES - 1))
  43#define SKB_WITH_OVERHEAD(X)    \
  44        ((X) - SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))
  45#define SKB_MAX_ORDER(X, ORDER) \
  46        SKB_WITH_OVERHEAD((PAGE_SIZE << (ORDER)) - (X))
  47#define SKB_MAX_HEAD(X)         (SKB_MAX_ORDER((X), 0))
  48#define SKB_MAX_ALLOC           (SKB_MAX_ORDER(0, 2))
  49
  50/* A. Checksumming of received packets by device.
  51 *
  52 *      NONE: device failed to checksum this packet.
  53 *              skb->csum is undefined.
  54 *
  55 *      UNNECESSARY: device parsed packet and wouldbe verified checksum.
  56 *              skb->csum is undefined.
  57 *            It is bad option, but, unfortunately, many of vendors do this.
  58 *            Apparently with secret goal to sell you new device, when you
  59 *            will add new protocol to your host. F.e. IPv6. 8)
  60 *
  61 *      COMPLETE: the most generic way. Device supplied checksum of _all_
  62 *          the packet as seen by netif_rx in skb->csum.
  63 *          NOTE: Even if device supports only some protocols, but
  64 *          is able to produce some skb->csum, it MUST use COMPLETE,
  65 *          not UNNECESSARY.
  66 *
  67 *      PARTIAL: identical to the case for output below.  This may occur
  68 *          on a packet received directly from another Linux OS, e.g.,
  69 *          a virtualised Linux kernel on the same host.  The packet can
  70 *          be treated in the same way as UNNECESSARY except that on
  71 *          output (i.e., forwarding) the checksum must be filled in
  72 *          by the OS or the hardware.
  73 *
  74 * B. Checksumming on output.
  75 *
  76 *      NONE: skb is checksummed by protocol or csum is not required.
  77 *
  78 *      PARTIAL: device is required to csum packet as seen by hard_start_xmit
  79 *      from skb->csum_start to the end and to record the checksum
  80 *      at skb->csum_start + skb->csum_offset.
  81 *
  82 *      Device must show its capabilities in dev->features, set
  83 *      at device setup time.
  84 *      NETIF_F_HW_CSUM - it is clever device, it is able to checksum
  85 *                        everything.
  86 *      NETIF_F_NO_CSUM - loopback or reliable single hop media.
  87 *      NETIF_F_IP_CSUM - device is dumb. It is able to csum only
  88 *                        TCP/UDP over IPv4. Sigh. Vendors like this
  89 *                        way by an unknown reason. Though, see comment above
  90 *                        about CHECKSUM_UNNECESSARY. 8)
  91 *      NETIF_F_IPV6_CSUM about as dumb as the last one but does IPv6 instead.
  92 *
  93 *      Any questions? No questions, good.              --ANK
  94 */
  95
  96struct net_device;
  97struct scatterlist;
  98struct pipe_inode_info;
  99
 100#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
 101struct nf_conntrack {
 102        atomic_t use;
 103};
 104#endif
 105
 106#ifdef CONFIG_BRIDGE_NETFILTER
 107struct nf_bridge_info {
 108        atomic_t use;
 109        struct net_device *physindev;
 110        struct net_device *physoutdev;
 111        unsigned int mask;
 112        unsigned long data[32 / sizeof(unsigned long)];
 113};
 114#endif
 115
 116struct sk_buff_head {
 117        /* These two members must be first. */
 118        struct sk_buff  *next;
 119        struct sk_buff  *prev;
 120
 121        __u32           qlen;
 122        spinlock_t      lock;
 123};
 124
 125struct sk_buff;
 126
 127/* To allow 64K frame to be packed as single skb without frag_list */
 128#define MAX_SKB_FRAGS (65536/PAGE_SIZE + 2)
 129
 130typedef struct skb_frag_struct skb_frag_t;
 131
 132struct skb_frag_struct {
 133        struct page *page;
 134        __u32 page_offset;
 135        __u32 size;
 136};
 137
 138/* This data is invariant across clones and lives at
 139 * the end of the header data, ie. at skb->end.
 140 */
 141struct skb_shared_info {
 142        atomic_t        dataref;
 143        unsigned short  nr_frags;
 144        unsigned short  gso_size;
 145        /* Warning: this field is not always filled in (UFO)! */
 146        unsigned short  gso_segs;
 147        unsigned short  gso_type;
 148        __be32          ip6_frag_id;
 149#ifdef CONFIG_HAS_DMA
 150        unsigned int    num_dma_maps;
 151#endif
 152        struct sk_buff  *frag_list;
 153        skb_frag_t      frags[MAX_SKB_FRAGS];
 154#ifdef CONFIG_HAS_DMA
 155        dma_addr_t      dma_maps[MAX_SKB_FRAGS + 1];
 156#endif
 157};
 158
 159/* We divide dataref into two halves.  The higher 16 bits hold references
 160 * to the payload part of skb->data.  The lower 16 bits hold references to
 161 * the entire skb->data.  A clone of a headerless skb holds the length of
 162 * the header in skb->hdr_len.
 163 *
 164 * All users must obey the rule that the skb->data reference count must be
 165 * greater than or equal to the payload reference count.
 166 *
 167 * Holding a reference to the payload part means that the user does not
 168 * care about modifications to the header part of skb->data.
 169 */
 170#define SKB_DATAREF_SHIFT 16
 171#define SKB_DATAREF_MASK ((1 << SKB_DATAREF_SHIFT) - 1)
 172
 173
 174enum {
 175        SKB_FCLONE_UNAVAILABLE,
 176        SKB_FCLONE_ORIG,
 177        SKB_FCLONE_CLONE,
 178};
 179
 180enum {
 181        SKB_GSO_TCPV4 = 1 << 0,
 182        SKB_GSO_UDP = 1 << 1,
 183
 184        /* This indicates the skb is from an untrusted source. */
 185        SKB_GSO_DODGY = 1 << 2,
 186
 187        /* This indicates the tcp segment has CWR set. */
 188        SKB_GSO_TCP_ECN = 1 << 3,
 189
 190        SKB_GSO_TCPV6 = 1 << 4,
 191};
 192
 193#if BITS_PER_LONG > 32
 194#define NET_SKBUFF_DATA_USES_OFFSET 1
 195#endif
 196
 197#ifdef NET_SKBUFF_DATA_USES_OFFSET
 198typedef unsigned int sk_buff_data_t;
 199#else
 200typedef unsigned char *sk_buff_data_t;
 201#endif
 202
 203/** 
 204 *      struct sk_buff - socket buffer
 205 *      @next: Next buffer in list
 206 *      @prev: Previous buffer in list
 207 *      @sk: Socket we are owned by
 208 *      @tstamp: Time we arrived
 209 *      @dev: Device we arrived on/are leaving by
 210 *      @transport_header: Transport layer header
 211 *      @network_header: Network layer header
 212 *      @mac_header: Link layer header
 213 *      @dst: destination entry
 214 *      @sp: the security path, used for xfrm
 215 *      @cb: Control buffer. Free for use by every layer. Put private vars here
 216 *      @len: Length of actual data
 217 *      @data_len: Data length
 218 *      @mac_len: Length of link layer header
 219 *      @hdr_len: writable header length of cloned skb
 220 *      @csum: Checksum (must include start/offset pair)
 221 *      @csum_start: Offset from skb->head where checksumming should start
 222 *      @csum_offset: Offset from csum_start where checksum should be stored
 223 *      @local_df: allow local fragmentation
 224 *      @cloned: Head may be cloned (check refcnt to be sure)
 225 *      @nohdr: Payload reference only, must not modify header
 226 *      @pkt_type: Packet class
 227 *      @fclone: skbuff clone status
 228 *      @ip_summed: Driver fed us an IP checksum
 229 *      @priority: Packet queueing priority
 230 *      @users: User count - see {datagram,tcp}.c
 231 *      @protocol: Packet protocol from driver
 232 *      @truesize: Buffer size 
 233 *      @head: Head of buffer
 234 *      @data: Data head pointer
 235 *      @tail: Tail pointer
 236 *      @end: End pointer
 237 *      @destructor: Destruct function
 238 *      @mark: Generic packet mark
 239 *      @nfct: Associated connection, if any
 240 *      @ipvs_property: skbuff is owned by ipvs
 241 *      @peeked: this packet has been seen already, so stats have been
 242 *              done for it, don't do them again
 243 *      @nf_trace: netfilter packet trace flag
 244 *      @nfctinfo: Relationship of this skb to the connection
 245 *      @nfct_reasm: netfilter conntrack re-assembly pointer
 246 *      @nf_bridge: Saved data about a bridged frame - see br_netfilter.c
 247 *      @iif: ifindex of device we arrived on
 248 *      @queue_mapping: Queue mapping for multiqueue devices
 249 *      @tc_index: Traffic control index
 250 *      @tc_verd: traffic control verdict
 251 *      @ndisc_nodetype: router type (from link layer)
 252 *      @do_not_encrypt: set to prevent encryption of this frame
 253 *      @dma_cookie: a cookie to one of several possible DMA operations
 254 *              done by skb DMA functions
 255 *      @secmark: security marking
 256 *      @vlan_tci: vlan tag control information
 257 */
 258
 259struct sk_buff {
 260        /* These two members must be first. */
 261        struct sk_buff          *next;
 262        struct sk_buff          *prev;
 263
 264        struct sock             *sk;
 265        ktime_t                 tstamp;
 266        struct net_device       *dev;
 267
 268        union {
 269                struct  dst_entry       *dst;
 270                struct  rtable          *rtable;
 271        };
 272        struct  sec_path        *sp;
 273
 274        /*
 275         * This is the control buffer. It is free to use for every
 276         * layer. Please put your private variables there. If you
 277         * want to keep them across layers you have to do a skb_clone()
 278         * first. This is owned by whoever has the skb queued ATM.
 279         */
 280        char                    cb[48];
 281
 282        unsigned int            len,
 283                                data_len;
 284        __u16                   mac_len,
 285                                hdr_len;
 286        union {
 287                __wsum          csum;
 288                struct {
 289                        __u16   csum_start;
 290                        __u16   csum_offset;
 291                };
 292        };
 293        __u32                   priority;
 294        __u8                    local_df:1,
 295                                cloned:1,
 296                                ip_summed:2,
 297                                nohdr:1,
 298                                nfctinfo:3;
 299        __u8                    pkt_type:3,
 300                                fclone:2,
 301                                ipvs_property:1,
 302                                peeked:1,
 303                                nf_trace:1;
 304        __be16                  protocol;
 305
 306        void                    (*destructor)(struct sk_buff *skb);
 307#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
 308        struct nf_conntrack     *nfct;
 309        struct sk_buff          *nfct_reasm;
 310#endif
 311#ifdef CONFIG_BRIDGE_NETFILTER
 312        struct nf_bridge_info   *nf_bridge;
 313#endif
 314
 315        int                     iif;
 316        __u16                   queue_mapping;
 317#ifdef CONFIG_NET_SCHED
 318        __u16                   tc_index;       /* traffic control index */
 319#ifdef CONFIG_NET_CLS_ACT
 320        __u16                   tc_verd;        /* traffic control verdict */
 321#endif
 322#endif
 323#ifdef CONFIG_IPV6_NDISC_NODETYPE
 324        __u8                    ndisc_nodetype:2;
 325#endif
 326#if defined(CONFIG_MAC80211) || defined(CONFIG_MAC80211_MODULE)
 327        __u8                    do_not_encrypt:1;
 328#endif
 329        /* 0/13/14 bit hole */
 330
 331#ifdef CONFIG_NET_DMA
 332        dma_cookie_t            dma_cookie;
 333#endif
 334#ifdef CONFIG_NETWORK_SECMARK
 335        __u32                   secmark;
 336#endif
 337
 338        __u32                   mark;
 339
 340        __u16                   vlan_tci;
 341
 342        sk_buff_data_t          transport_header;
 343        sk_buff_data_t          network_header;
 344        sk_buff_data_t          mac_header;
 345        /* These elements must be at the end, see alloc_skb() for details.  */
 346        sk_buff_data_t          tail;
 347        sk_buff_data_t          end;
 348        unsigned char           *head,
 349                                *data;
 350        unsigned int            truesize;
 351        atomic_t                users;
 352};
 353
 354#ifdef __KERNEL__
 355/*
 356 *      Handling routines are only of interest to the kernel
 357 */
 358#include <linux/slab.h>
 359
 360#include <asm/system.h>
 361
 362#ifdef CONFIG_HAS_DMA
 363#include <linux/dma-mapping.h>
 364extern int skb_dma_map(struct device *dev, struct sk_buff *skb,
 365                       enum dma_data_direction dir);
 366extern void skb_dma_unmap(struct device *dev, struct sk_buff *skb,
 367                          enum dma_data_direction dir);
 368#endif
 369
 370extern void kfree_skb(struct sk_buff *skb);
 371extern void            __kfree_skb(struct sk_buff *skb);
 372extern struct sk_buff *__alloc_skb(unsigned int size,
 373                                   gfp_t priority, int fclone, int node);
 374static inline struct sk_buff *alloc_skb(unsigned int size,
 375                                        gfp_t priority)
 376{
 377        return __alloc_skb(size, priority, 0, -1);
 378}
 379
 380static inline struct sk_buff *alloc_skb_fclone(unsigned int size,
 381                                               gfp_t priority)
 382{
 383        return __alloc_skb(size, priority, 1, -1);
 384}
 385
 386extern int skb_recycle_check(struct sk_buff *skb, int skb_size);
 387
 388extern struct sk_buff *skb_morph(struct sk_buff *dst, struct sk_buff *src);
 389extern struct sk_buff *skb_clone(struct sk_buff *skb,
 390                                 gfp_t priority);
 391extern struct sk_buff *skb_copy(const struct sk_buff *skb,
 392                                gfp_t priority);
 393extern struct sk_buff *pskb_copy(struct sk_buff *skb,
 394                                 gfp_t gfp_mask);
 395extern int             pskb_expand_head(struct sk_buff *skb,
 396                                        int nhead, int ntail,
 397                                        gfp_t gfp_mask);
 398extern struct sk_buff *skb_realloc_headroom(struct sk_buff *skb,
 399                                            unsigned int headroom);
 400extern struct sk_buff *skb_copy_expand(const struct sk_buff *skb,
 401                                       int newheadroom, int newtailroom,
 402                                       gfp_t priority);
 403extern int             skb_to_sgvec(struct sk_buff *skb,
 404                                    struct scatterlist *sg, int offset,
 405                                    int len);
 406extern int             skb_cow_data(struct sk_buff *skb, int tailbits,
 407                                    struct sk_buff **trailer);
 408extern int             skb_pad(struct sk_buff *skb, int pad);
 409#define dev_kfree_skb(a)        kfree_skb(a)
 410extern void           skb_over_panic(struct sk_buff *skb, int len,
 411                                     void *here);
 412extern void           skb_under_panic(struct sk_buff *skb, int len,
 413                                      void *here);
 414extern void           skb_truesize_bug(struct sk_buff *skb);
 415
 416static inline void skb_truesize_check(struct sk_buff *skb)
 417{
 418        int len = sizeof(struct sk_buff) + skb->len;
 419
 420        if (unlikely((int)skb->truesize < len))
 421                skb_truesize_bug(skb);
 422}
 423
 424extern int skb_append_datato_frags(struct sock *sk, struct sk_buff *skb,
 425                        int getfrag(void *from, char *to, int offset,
 426                        int len,int odd, struct sk_buff *skb),
 427                        void *from, int length);
 428
 429struct skb_seq_state
 430{
 431        __u32           lower_offset;
 432        __u32           upper_offset;
 433        __u32           frag_idx;
 434        __u32           stepped_offset;
 435        struct sk_buff  *root_skb;
 436        struct sk_buff  *cur_skb;
 437        __u8            *frag_data;
 438};
 439
 440extern void           skb_prepare_seq_read(struct sk_buff *skb,
 441                                           unsigned int from, unsigned int to,
 442                                           struct skb_seq_state *st);
 443extern unsigned int   skb_seq_read(unsigned int consumed, const u8 **data,
 444                                   struct skb_seq_state *st);
 445extern void           skb_abort_seq_read(struct skb_seq_state *st);
 446
 447extern unsigned int   skb_find_text(struct sk_buff *skb, unsigned int from,
 448                                    unsigned int to, struct ts_config *config,
 449                                    struct ts_state *state);
 450
 451#ifdef NET_SKBUFF_DATA_USES_OFFSET
 452static inline unsigned char *skb_end_pointer(const struct sk_buff *skb)
 453{
 454        return skb->head + skb->end;
 455}
 456#else
 457static inline unsigned char *skb_end_pointer(const struct sk_buff *skb)
 458{
 459        return skb->end;
 460}
 461#endif
 462
 463/* Internal */
 464#define skb_shinfo(SKB) ((struct skb_shared_info *)(skb_end_pointer(SKB)))
 465
 466/**
 467 *      skb_queue_empty - check if a queue is empty
 468 *      @list: queue head
 469 *
 470 *      Returns true if the queue is empty, false otherwise.
 471 */
 472static inline int skb_queue_empty(const struct sk_buff_head *list)
 473{
 474        return list->next == (struct sk_buff *)list;
 475}
 476
 477/**
 478 *      skb_queue_is_last - check if skb is the last entry in the queue
 479 *      @list: queue head
 480 *      @skb: buffer
 481 *
 482 *      Returns true if @skb is the last buffer on the list.
 483 */
 484static inline bool skb_queue_is_last(const struct sk_buff_head *list,
 485                                     const struct sk_buff *skb)
 486{
 487        return (skb->next == (struct sk_buff *) list);
 488}
 489
 490/**
 491 *      skb_queue_next - return the next packet in the queue
 492 *      @list: queue head
 493 *      @skb: current buffer
 494 *
 495 *      Return the next packet in @list after @skb.  It is only valid to
 496 *      call this if skb_queue_is_last() evaluates to false.
 497 */
 498static inline struct sk_buff *skb_queue_next(const struct sk_buff_head *list,
 499                                             const struct sk_buff *skb)
 500{
 501        /* This BUG_ON may seem severe, but if we just return then we
 502         * are going to dereference garbage.
 503         */
 504        BUG_ON(skb_queue_is_last(list, skb));
 505        return skb->next;
 506}
 507
 508/**
 509 *      skb_get - reference buffer
 510 *      @skb: buffer to reference
 511 *
 512 *      Makes another reference to a socket buffer and returns a pointer
 513 *      to the buffer.
 514 */
 515static inline struct sk_buff *skb_get(struct sk_buff *skb)
 516{
 517        atomic_inc(&skb->users);
 518        return skb;
 519}
 520
 521/*
 522 * If users == 1, we are the only owner and are can avoid redundant
 523 * atomic change.
 524 */
 525
 526/**
 527 *      skb_cloned - is the buffer a clone
 528 *      @skb: buffer to check
 529 *
 530 *      Returns true if the buffer was generated with skb_clone() and is
 531 *      one of multiple shared copies of the buffer. Cloned buffers are
 532 *      shared data so must not be written to under normal circumstances.
 533 */
 534static inline int skb_cloned(const struct sk_buff *skb)
 535{
 536        return skb->cloned &&
 537               (atomic_read(&skb_shinfo(skb)->dataref) & SKB_DATAREF_MASK) != 1;
 538}
 539
 540/**
 541 *      skb_header_cloned - is the header a clone
 542 *      @skb: buffer to check
 543 *
 544 *      Returns true if modifying the header part of the buffer requires
 545 *      the data to be copied.
 546 */
 547static inline int skb_header_cloned(const struct sk_buff *skb)
 548{
 549        int dataref;
 550
 551        if (!skb->cloned)
 552                return 0;
 553
 554        dataref = atomic_read(&skb_shinfo(skb)->dataref);
 555        dataref = (dataref & SKB_DATAREF_MASK) - (dataref >> SKB_DATAREF_SHIFT);
 556        return dataref != 1;
 557}
 558
 559/**
 560 *      skb_header_release - release reference to header
 561 *      @skb: buffer to operate on
 562 *
 563 *      Drop a reference to the header part of the buffer.  This is done
 564 *      by acquiring a payload reference.  You must not read from the header
 565 *      part of skb->data after this.
 566 */
 567static inline void skb_header_release(struct sk_buff *skb)
 568{
 569        BUG_ON(skb->nohdr);
 570        skb->nohdr = 1;
 571        atomic_add(1 << SKB_DATAREF_SHIFT, &skb_shinfo(skb)->dataref);
 572}
 573
 574/**
 575 *      skb_shared - is the buffer shared
 576 *      @skb: buffer to check
 577 *
 578 *      Returns true if more than one person has a reference to this
 579 *      buffer.
 580 */
 581static inline int skb_shared(const struct sk_buff *skb)
 582{
 583        return atomic_read(&skb->users) != 1;
 584}
 585
 586/**
 587 *      skb_share_check - check if buffer is shared and if so clone it
 588 *      @skb: buffer to check
 589 *      @pri: priority for memory allocation
 590 *
 591 *      If the buffer is shared the buffer is cloned and the old copy
 592 *      drops a reference. A new clone with a single reference is returned.
 593 *      If the buffer is not shared the original buffer is returned. When
 594 *      being called from interrupt status or with spinlocks held pri must
 595 *      be GFP_ATOMIC.
 596 *
 597 *      NULL is returned on a memory allocation failure.
 598 */
 599static inline struct sk_buff *skb_share_check(struct sk_buff *skb,
 600                                              gfp_t pri)
 601{
 602        might_sleep_if(pri & __GFP_WAIT);
 603        if (skb_shared(skb)) {
 604                struct sk_buff *nskb = skb_clone(skb, pri);
 605                kfree_skb(skb);
 606                skb = nskb;
 607        }
 608        return skb;
 609}
 610
 611/*
 612 *      Copy shared buffers into a new sk_buff. We effectively do COW on
 613 *      packets to handle cases where we have a local reader and forward
 614 *      and a couple of other messy ones. The normal one is tcpdumping
 615 *      a packet thats being forwarded.
 616 */
 617
 618/**
 619 *      skb_unshare - make a copy of a shared buffer
 620 *      @skb: buffer to check
 621 *      @pri: priority for memory allocation
 622 *
 623 *      If the socket buffer is a clone then this function creates a new
 624 *      copy of the data, drops a reference count on the old copy and returns
 625 *      the new copy with the reference count at 1. If the buffer is not a clone
 626 *      the original buffer is returned. When called with a spinlock held or
 627 *      from interrupt state @pri must be %GFP_ATOMIC
 628 *
 629 *      %NULL is returned on a memory allocation failure.
 630 */
 631static inline struct sk_buff *skb_unshare(struct sk_buff *skb,
 632                                          gfp_t pri)
 633{
 634        might_sleep_if(pri & __GFP_WAIT);
 635        if (skb_cloned(skb)) {
 636                struct sk_buff *nskb = skb_copy(skb, pri);
 637                kfree_skb(skb); /* Free our shared copy */
 638                skb = nskb;
 639        }
 640        return skb;
 641}
 642
 643/**
 644 *      skb_peek
 645 *      @list_: list to peek at
 646 *
 647 *      Peek an &sk_buff. Unlike most other operations you _MUST_
 648 *      be careful with this one. A peek leaves the buffer on the
 649 *      list and someone else may run off with it. You must hold
 650 *      the appropriate locks or have a private queue to do this.
 651 *
 652 *      Returns %NULL for an empty list or a pointer to the head element.
 653 *      The reference count is not incremented and the reference is therefore
 654 *      volatile. Use with caution.
 655 */
 656static inline struct sk_buff *skb_peek(struct sk_buff_head *list_)
 657{
 658        struct sk_buff *list = ((struct sk_buff *)list_)->next;
 659        if (list == (struct sk_buff *)list_)
 660                list = NULL;
 661        return list;
 662}
 663
 664/**
 665 *      skb_peek_tail
 666 *      @list_: list to peek at
 667 *
 668 *      Peek an &sk_buff. Unlike most other operations you _MUST_
 669 *      be careful with this one. A peek leaves the buffer on the
 670 *      list and someone else may run off with it. You must hold
 671 *      the appropriate locks or have a private queue to do this.
 672 *
 673 *      Returns %NULL for an empty list or a pointer to the tail element.
 674 *      The reference count is not incremented and the reference is therefore
 675 *      volatile. Use with caution.
 676 */
 677static inline struct sk_buff *skb_peek_tail(struct sk_buff_head *list_)
 678{
 679        struct sk_buff *list = ((struct sk_buff *)list_)->prev;
 680        if (list == (struct sk_buff *)list_)
 681                list = NULL;
 682        return list;
 683}
 684
 685/**
 686 *      skb_queue_len   - get queue length
 687 *      @list_: list to measure
 688 *
 689 *      Return the length of an &sk_buff queue.
 690 */
 691static inline __u32 skb_queue_len(const struct sk_buff_head *list_)
 692{
 693        return list_->qlen;
 694}
 695
 696/**
 697 *      __skb_queue_head_init - initialize non-spinlock portions of sk_buff_head
 698 *      @list: queue to initialize
 699 *
 700 *      This initializes only the list and queue length aspects of
 701 *      an sk_buff_head object.  This allows to initialize the list
 702 *      aspects of an sk_buff_head without reinitializing things like
 703 *      the spinlock.  It can also be used for on-stack sk_buff_head
 704 *      objects where the spinlock is known to not be used.
 705 */
 706static inline void __skb_queue_head_init(struct sk_buff_head *list)
 707{
 708        list->prev = list->next = (struct sk_buff *)list;
 709        list->qlen = 0;
 710}
 711
 712/*
 713 * This function creates a split out lock class for each invocation;
 714 * this is needed for now since a whole lot of users of the skb-queue
 715 * infrastructure in drivers have different locking usage (in hardirq)
 716 * than the networking core (in softirq only). In the long run either the
 717 * network layer or drivers should need annotation to consolidate the
 718 * main types of usage into 3 classes.
 719 */
 720static inline void skb_queue_head_init(struct sk_buff_head *list)
 721{
 722        spin_lock_init(&list->lock);
 723        __skb_queue_head_init(list);
 724}
 725
 726static inline void skb_queue_head_init_class(struct sk_buff_head *list,
 727                struct lock_class_key *class)
 728{
 729        skb_queue_head_init(list);
 730        lockdep_set_class(&list->lock, class);
 731}
 732
 733/*
 734 *      Insert an sk_buff on a list.
 735 *
 736 *      The "__skb_xxxx()" functions are the non-atomic ones that
 737 *      can only be called with interrupts disabled.
 738 */
 739extern void        skb_insert(struct sk_buff *old, struct sk_buff *newsk, struct sk_buff_head *list);
 740static inline void __skb_insert(struct sk_buff *newsk,
 741                                struct sk_buff *prev, struct sk_buff *next,
 742                                struct sk_buff_head *list)
 743{
 744        newsk->next = next;
 745        newsk->prev = prev;
 746        next->prev  = prev->next = newsk;
 747        list->qlen++;
 748}
 749
 750static inline void __skb_queue_splice(const struct sk_buff_head *list,
 751                                      struct sk_buff *prev,
 752                                      struct sk_buff *next)
 753{
 754        struct sk_buff *first = list->next;
 755        struct sk_buff *last = list->prev;
 756
 757        first->prev = prev;
 758        prev->next = first;
 759
 760        last->next = next;
 761        next->prev = last;
 762}
 763
 764/**
 765 *      skb_queue_splice - join two skb lists, this is designed for stacks
 766 *      @list: the new list to add
 767 *      @head: the place to add it in the first list
 768 */
 769static inline void skb_queue_splice(const struct sk_buff_head *list,
 770                                    struct sk_buff_head *head)
 771{
 772        if (!skb_queue_empty(list)) {
 773                __skb_queue_splice(list, (struct sk_buff *) head, head->next);
 774                head->qlen += list->qlen;
 775        }
 776}
 777
 778/**
 779 *      skb_queue_splice - join two skb lists and reinitialise the emptied list
 780 *      @list: the new list to add
 781 *      @head: the place to add it in the first list
 782 *
 783 *      The list at @list is reinitialised
 784 */
 785static inline void skb_queue_splice_init(struct sk_buff_head *list,
 786                                         struct sk_buff_head *head)
 787{
 788        if (!skb_queue_empty(list)) {
 789                __skb_queue_splice(list, (struct sk_buff *) head, head->next);
 790                head->qlen += list->qlen;
 791                __skb_queue_head_init(list);
 792        }
 793}
 794
 795/**
 796 *      skb_queue_splice_tail - join two skb lists, each list being a queue
 797 *      @list: the new list to add
 798 *      @head: the place to add it in the first list
 799 */
 800static inline void skb_queue_splice_tail(const struct sk_buff_head *list,
 801                                         struct sk_buff_head *head)
 802{
 803        if (!skb_queue_empty(list)) {
 804                __skb_queue_splice(list, head->prev, (struct sk_buff *) head);
 805                head->qlen += list->qlen;
 806        }
 807}
 808
 809/**
 810 *      skb_queue_splice_tail - join two skb lists and reinitialise the emptied list
 811 *      @list: the new list to add
 812 *      @head: the place to add it in the first list
 813 *
 814 *      Each of the lists is a queue.
 815 *      The list at @list is reinitialised
 816 */
 817static inline void skb_queue_splice_tail_init(struct sk_buff_head *list,
 818                                              struct sk_buff_head *head)
 819{
 820        if (!skb_queue_empty(list)) {
 821                __skb_queue_splice(list, head->prev, (struct sk_buff *) head);
 822                head->qlen += list->qlen;
 823                __skb_queue_head_init(list);
 824        }
 825}
 826
 827/**
 828 *      __skb_queue_after - queue a buffer at the list head
 829 *      @list: list to use
 830 *      @prev: place after this buffer
 831 *      @newsk: buffer to queue
 832 *
 833 *      Queue a buffer int the middle of a list. This function takes no locks
 834 *      and you must therefore hold required locks before calling it.
 835 *
 836 *      A buffer cannot be placed on two lists at the same time.
 837 */
 838static inline void __skb_queue_after(struct sk_buff_head *list,
 839                                     struct sk_buff *prev,
 840                                     struct sk_buff *newsk)
 841{
 842        __skb_insert(newsk, prev, prev->next, list);
 843}
 844
 845extern void skb_append(struct sk_buff *old, struct sk_buff *newsk,
 846                       struct sk_buff_head *list);
 847
 848static inline void __skb_queue_before(struct sk_buff_head *list,
 849                                      struct sk_buff *next,
 850                                      struct sk_buff *newsk)
 851{
 852        __skb_insert(newsk, next->prev, next, list);
 853}
 854
 855/**
 856 *      __skb_queue_head - queue a buffer at the list head
 857 *      @list: list to use
 858 *      @newsk: buffer to queue
 859 *
 860 *      Queue a buffer at the start of a list. This function takes no locks
 861 *      and you must therefore hold required locks before calling it.
 862 *
 863 *      A buffer cannot be placed on two lists at the same time.
 864 */
 865extern void skb_queue_head(struct sk_buff_head *list, struct sk_buff *newsk);
 866static inline void __skb_queue_head(struct sk_buff_head *list,
 867                                    struct sk_buff *newsk)
 868{
 869        __skb_queue_after(list, (struct sk_buff *)list, newsk);
 870}
 871
 872/**
 873 *      __skb_queue_tail - queue a buffer at the list tail
 874 *      @list: list to use
 875 *      @newsk: buffer to queue
 876 *
 877 *      Queue a buffer at the end of a list. This function takes no locks
 878 *      and you must therefore hold required locks before calling it.
 879 *
 880 *      A buffer cannot be placed on two lists at the same time.
 881 */
 882extern void skb_queue_tail(struct sk_buff_head *list, struct sk_buff *newsk);
 883static inline void __skb_queue_tail(struct sk_buff_head *list,
 884                                   struct sk_buff *newsk)
 885{
 886        __skb_queue_before(list, (struct sk_buff *)list, newsk);
 887}
 888
 889/*
 890 * remove sk_buff from list. _Must_ be called atomically, and with
 891 * the list known..
 892 */
 893extern void        skb_unlink(struct sk_buff *skb, struct sk_buff_head *list);
 894static inline void __skb_unlink(struct sk_buff *skb, struct sk_buff_head *list)
 895{
 896        struct sk_buff *next, *prev;
 897
 898        list->qlen--;
 899        next       = skb->next;
 900        prev       = skb->prev;
 901        skb->next  = skb->prev = NULL;
 902        next->prev = prev;
 903        prev->next = next;
 904}
 905
 906/**
 907 *      __skb_dequeue - remove from the head of the queue
 908 *      @list: list to dequeue from
 909 *
 910 *      Remove the head of the list. This function does not take any locks
 911 *      so must be used with appropriate locks held only. The head item is
 912 *      returned or %NULL if the list is empty.
 913 */
 914extern struct sk_buff *skb_dequeue(struct sk_buff_head *list);
 915static inline struct sk_buff *__skb_dequeue(struct sk_buff_head *list)
 916{
 917        struct sk_buff *skb = skb_peek(list);
 918        if (skb)
 919                __skb_unlink(skb, list);
 920        return skb;
 921}
 922
 923/**
 924 *      __skb_dequeue_tail - remove from the tail of the queue
 925 *      @list: list to dequeue from
 926 *
 927 *      Remove the tail of the list. This function does not take any locks
 928 *      so must be used with appropriate locks held only. The tail item is
 929 *      returned or %NULL if the list is empty.
 930 */
 931extern struct sk_buff *skb_dequeue_tail(struct sk_buff_head *list);
 932static inline struct sk_buff *__skb_dequeue_tail(struct sk_buff_head *list)
 933{
 934        struct sk_buff *skb = skb_peek_tail(list);
 935        if (skb)
 936                __skb_unlink(skb, list);
 937        return skb;
 938}
 939
 940
 941static inline int skb_is_nonlinear(const struct sk_buff *skb)
 942{
 943        return skb->data_len;
 944}
 945
 946static inline unsigned int skb_headlen(const struct sk_buff *skb)
 947{
 948        return skb->len - skb->data_len;
 949}
 950
 951static inline int skb_pagelen(const struct sk_buff *skb)
 952{
 953        int i, len = 0;
 954
 955        for (i = (int)skb_shinfo(skb)->nr_frags - 1; i >= 0; i--)
 956                len += skb_shinfo(skb)->frags[i].size;
 957        return len + skb_headlen(skb);
 958}
 959
 960static inline void skb_fill_page_desc(struct sk_buff *skb, int i,
 961                                      struct page *page, int off, int size)
 962{
 963        skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
 964
 965        frag->page                = page;
 966        frag->page_offset         = off;
 967        frag->size                = size;
 968        skb_shinfo(skb)->nr_frags = i + 1;
 969}
 970
 971extern void skb_add_rx_frag(struct sk_buff *skb, int i, struct page *page,
 972                            int off, int size);
 973
 974#define SKB_PAGE_ASSERT(skb)    BUG_ON(skb_shinfo(skb)->nr_frags)
 975#define SKB_FRAG_ASSERT(skb)    BUG_ON(skb_shinfo(skb)->frag_list)
 976#define SKB_LINEAR_ASSERT(skb)  BUG_ON(skb_is_nonlinear(skb))
 977
 978#ifdef NET_SKBUFF_DATA_USES_OFFSET
 979static inline unsigned char *skb_tail_pointer(const struct sk_buff *skb)
 980{
 981        return skb->head + skb->tail;
 982}
 983
 984static inline void skb_reset_tail_pointer(struct sk_buff *skb)
 985{
 986        skb->tail = skb->data - skb->head;
 987}
 988
 989static inline void skb_set_tail_pointer(struct sk_buff *skb, const int offset)
 990{
 991        skb_reset_tail_pointer(skb);
 992        skb->tail += offset;
 993}
 994#else /* NET_SKBUFF_DATA_USES_OFFSET */
 995static inline unsigned char *skb_tail_pointer(const struct sk_buff *skb)
 996{
 997        return skb->tail;
 998}
 999
1000static inline void skb_reset_tail_pointer(struct sk_buff *skb)
1001{
1002        skb->tail = skb->data;
1003}
1004
1005static inline void skb_set_tail_pointer(struct sk_buff *skb, const int offset)
1006{
1007        skb->tail = skb->data + offset;
1008}
1009
1010#endif /* NET_SKBUFF_DATA_USES_OFFSET */
1011
1012/*
1013 *      Add data to an sk_buff
1014 */
1015extern unsigned char *skb_put(struct sk_buff *skb, unsigned int len);
1016static inline unsigned char *__skb_put(struct sk_buff *skb, unsigned int len)
1017{
1018        unsigned char *tmp = skb_tail_pointer(skb);
1019        SKB_LINEAR_ASSERT(skb);
1020        skb->tail += len;
1021        skb->len  += len;
1022        return tmp;
1023}
1024
1025extern unsigned char *skb_push(struct sk_buff *skb, unsigned int len);
1026static inline unsigned char *__skb_push(struct sk_buff *skb, unsigned int len)
1027{
1028        skb->data -= len;
1029        skb->len  += len;
1030        return skb->data;
1031}
1032
1033extern unsigned char *skb_pull(struct sk_buff *skb, unsigned int len);
1034static inline unsigned char *__skb_pull(struct sk_buff *skb, unsigned int len)
1035{
1036        skb->len -= len;
1037        BUG_ON(skb->len < skb->data_len);
1038        return skb->data += len;
1039}
1040
1041extern unsigned char *__pskb_pull_tail(struct sk_buff *skb, int delta);
1042
1043static inline unsigned char *__pskb_pull(struct sk_buff *skb, unsigned int len)
1044{
1045        if (len > skb_headlen(skb) &&
1046            !__pskb_pull_tail(skb, len - skb_headlen(skb)))
1047                return NULL;
1048        skb->len -= len;
1049        return skb->data += len;
1050}
1051
1052static inline unsigned char *pskb_pull(struct sk_buff *skb, unsigned int len)
1053{
1054        return unlikely(len > skb->len) ? NULL : __pskb_pull(skb, len);
1055}
1056
1057static inline int pskb_may_pull(struct sk_buff *skb, unsigned int len)
1058{
1059        if (likely(len <= skb_headlen(skb)))
1060                return 1;
1061        if (unlikely(len > skb->len))
1062                return 0;
1063        return __pskb_pull_tail(skb, len - skb_headlen(skb)) != NULL;
1064}
1065
1066/**
1067 *      skb_headroom - bytes at buffer head
1068 *      @skb: buffer to check
1069 *
1070 *      Return the number of bytes of free space at the head of an &sk_buff.
1071 */
1072static inline unsigned int skb_headroom(const struct sk_buff *skb)
1073{
1074        return skb->data - skb->head;
1075}
1076
1077/**
1078 *      skb_tailroom - bytes at buffer end
1079 *      @skb: buffer to check
1080 *
1081 *      Return the number of bytes of free space at the tail of an sk_buff
1082 */
1083static inline int skb_tailroom(const struct sk_buff *skb)
1084{
1085        return skb_is_nonlinear(skb) ? 0 : skb->end - skb->tail;
1086}
1087
1088/**
1089 *      skb_reserve - adjust headroom
1090 *      @skb: buffer to alter
1091 *      @len: bytes to move
1092 *
1093 *      Increase the headroom of an empty &sk_buff by reducing the tail
1094 *      room. This is only allowed for an empty buffer.
1095 */
1096static inline void skb_reserve(struct sk_buff *skb, int len)
1097{
1098        skb->data += len;
1099        skb->tail += len;
1100}
1101
1102#ifdef NET_SKBUFF_DATA_USES_OFFSET
1103static inline unsigned char *skb_transport_header(const struct sk_buff *skb)
1104{
1105        return skb->head + skb->transport_header;
1106}
1107
1108static inline void skb_reset_transport_header(struct sk_buff *skb)
1109{
1110        skb->transport_header = skb->data - skb->head;
1111}
1112
1113static inline void skb_set_transport_header(struct sk_buff *skb,
1114                                            const int offset)
1115{
1116        skb_reset_transport_header(skb);
1117        skb->transport_header += offset;
1118}
1119
1120static inline unsigned char *skb_network_header(const struct sk_buff *skb)
1121{
1122        return skb->head + skb->network_header;
1123}
1124
1125static inline void skb_reset_network_header(struct sk_buff *skb)
1126{
1127        skb->network_header = skb->data - skb->head;
1128}
1129
1130static inline void skb_set_network_header(struct sk_buff *skb, const int offset)
1131{
1132        skb_reset_network_header(skb);
1133        skb->network_header += offset;
1134}
1135
1136static inline unsigned char *skb_mac_header(const struct sk_buff *skb)
1137{
1138        return skb->head + skb->mac_header;
1139}
1140
1141static inline int skb_mac_header_was_set(const struct sk_buff *skb)
1142{
1143        return skb->mac_header != ~0U;
1144}
1145
1146static inline void skb_reset_mac_header(struct sk_buff *skb)
1147{
1148        skb->mac_header = skb->data - skb->head;
1149}
1150
1151static inline void skb_set_mac_header(struct sk_buff *skb, const int offset)
1152{
1153        skb_reset_mac_header(skb);
1154        skb->mac_header += offset;
1155}
1156
1157#else /* NET_SKBUFF_DATA_USES_OFFSET */
1158
1159static inline unsigned char *skb_transport_header(const struct sk_buff *skb)
1160{
1161        return skb->transport_header;
1162}
1163
1164static inline void skb_reset_transport_header(struct sk_buff *skb)
1165{
1166        skb->transport_header = skb->data;
1167}
1168
1169static inline void skb_set_transport_header(struct sk_buff *skb,
1170                                            const int offset)
1171{
1172        skb->transport_header = skb->data + offset;
1173}
1174
1175static inline unsigned char *skb_network_header(const struct sk_buff *skb)
1176{
1177        return skb->network_header;
1178}
1179
1180static inline void skb_reset_network_header(struct sk_buff *skb)
1181{
1182        skb->network_header = skb->data;
1183}
1184
1185static inline void skb_set_network_header(struct sk_buff *skb, const int offset)
1186{
1187        skb->network_header = skb->data + offset;
1188}
1189
1190static inline unsigned char *skb_mac_header(const struct sk_buff *skb)
1191{
1192        return skb->mac_header;
1193}
1194
1195static inline int skb_mac_header_was_set(const struct sk_buff *skb)
1196{
1197        return skb->mac_header != NULL;
1198}
1199
1200static inline void skb_reset_mac_header(struct sk_buff *skb)
1201{
1202        skb->mac_header = skb->data;
1203}
1204
1205static inline void skb_set_mac_header(struct sk_buff *skb, const int offset)
1206{
1207        skb->mac_header = skb->data + offset;
1208}
1209#endif /* NET_SKBUFF_DATA_USES_OFFSET */
1210
1211static inline int skb_transport_offset(const struct sk_buff *skb)
1212{
1213        return skb_transport_header(skb) - skb->data;
1214}
1215
1216static inline u32 skb_network_header_len(const struct sk_buff *skb)
1217{
1218        return skb->transport_header - skb->network_header;
1219}
1220
1221static inline int skb_network_offset(const struct sk_buff *skb)
1222{
1223        return skb_network_header(skb) - skb->data;
1224}
1225
1226/*
1227 * CPUs often take a performance hit when accessing unaligned memory
1228 * locations. The actual performance hit varies, it can be small if the
1229 * hardware handles it or large if we have to take an exception and fix it
1230 * in software.
1231 *
1232 * Since an ethernet header is 14 bytes network drivers often end up with
1233 * the IP header at an unaligned offset. The IP header can be aligned by
1234 * shifting the start of the packet by 2 bytes. Drivers should do this
1235 * with:
1236 *
1237 * skb_reserve(NET_IP_ALIGN);
1238 *
1239 * The downside to this alignment of the IP header is that the DMA is now
1240 * unaligned. On some architectures the cost of an unaligned DMA is high
1241 * and this cost outweighs the gains made by aligning the IP header.
1242 * 
1243 * Since this trade off varies between architectures, we allow NET_IP_ALIGN
1244 * to be overridden.
1245 */
1246#ifndef NET_IP_ALIGN
1247#define NET_IP_ALIGN    2
1248#endif
1249
1250/*
1251 * The networking layer reserves some headroom in skb data (via
1252 * dev_alloc_skb). This is used to avoid having to reallocate skb data when
1253 * the header has to grow. In the default case, if the header has to grow
1254 * 16 bytes or less we avoid the reallocation.
1255 *
1256 * Unfortunately this headroom changes the DMA alignment of the resulting
1257 * network packet. As for NET_IP_ALIGN, this unaligned DMA is expensive
1258 * on some architectures. An architecture can override this value,
1259 * perhaps setting it to a cacheline in size (since that will maintain
1260 * cacheline alignment of the DMA). It must be a power of 2.
1261 *
1262 * Various parts of the networking layer expect at least 16 bytes of
1263 * headroom, you should not reduce this.
1264 */
1265#ifndef NET_SKB_PAD
1266#define NET_SKB_PAD     16
1267#endif
1268
1269extern int ___pskb_trim(struct sk_buff *skb, unsigned int len);
1270
1271static inline void __skb_trim(struct sk_buff *skb, unsigned int len)
1272{
1273        if (unlikely(skb->data_len)) {
1274                WARN_ON(1);
1275                return;
1276        }
1277        skb->len = len;
1278        skb_set_tail_pointer(skb, len);
1279}
1280
1281extern void skb_trim(struct sk_buff *skb, unsigned int len);
1282
1283static inline int __pskb_trim(struct sk_buff *skb, unsigned int len)
1284{
1285        if (skb->data_len)
1286                return ___pskb_trim(skb, len);
1287        __skb_trim(skb, len);
1288        return 0;
1289}
1290
1291static inline int pskb_trim(struct sk_buff *skb, unsigned int len)
1292{
1293        return (len < skb->len) ? __pskb_trim(skb, len) : 0;
1294}
1295
1296/**
1297 *      pskb_trim_unique - remove end from a paged unique (not cloned) buffer
1298 *      @skb: buffer to alter
1299 *      @len: new length
1300 *
1301 *      This is identical to pskb_trim except that the caller knows that
1302 *      the skb is not cloned so we should never get an error due to out-
1303 *      of-memory.
1304 */
1305static inline void pskb_trim_unique(struct sk_buff *skb, unsigned int len)
1306{
1307        int err = pskb_trim(skb, len);
1308        BUG_ON(err);
1309}
1310
1311/**
1312 *      skb_orphan - orphan a buffer
1313 *      @skb: buffer to orphan
1314 *
1315 *      If a buffer currently has an owner then we call the owner's
1316 *      destructor function and make the @skb unowned. The buffer continues
1317 *      to exist but is no longer charged to its former owner.
1318 */
1319static inline void skb_orphan(struct sk_buff *skb)
1320{
1321        if (skb->destructor)
1322                skb->destructor(skb);
1323        skb->destructor = NULL;
1324        skb->sk         = NULL;
1325}
1326
1327/**
1328 *      __skb_queue_purge - empty a list
1329 *      @list: list to empty
1330 *
1331 *      Delete all buffers on an &sk_buff list. Each buffer is removed from
1332 *      the list and one reference dropped. This function does not take the
1333 *      list lock and the caller must hold the relevant locks to use it.
1334 */
1335extern void skb_queue_purge(struct sk_buff_head *list);
1336static inline void __skb_queue_purge(struct sk_buff_head *list)
1337{
1338        struct sk_buff *skb;
1339        while ((skb = __skb_dequeue(list)) != NULL)
1340                kfree_skb(skb);
1341}
1342
1343/**
1344 *      __dev_alloc_skb - allocate an skbuff for receiving
1345 *      @length: length to allocate
1346 *      @gfp_mask: get_free_pages mask, passed to alloc_skb
1347 *
1348 *      Allocate a new &sk_buff and assign it a usage count of one. The
1349 *      buffer has unspecified headroom built in. Users should allocate
1350 *      the headroom they think they need without accounting for the
1351 *      built in space. The built in space is used for optimisations.
1352 *
1353 *      %NULL is returned if there is no free memory.
1354 */
1355static inline struct sk_buff *__dev_alloc_skb(unsigned int length,
1356                                              gfp_t gfp_mask)
1357{
1358        struct sk_buff *skb = alloc_skb(length + NET_SKB_PAD, gfp_mask);
1359        if (likely(skb))
1360                skb_reserve(skb, NET_SKB_PAD);
1361        return skb;
1362}
1363
1364extern struct sk_buff *dev_alloc_skb(unsigned int length);
1365
1366extern struct sk_buff *__netdev_alloc_skb(struct net_device *dev,
1367                unsigned int length, gfp_t gfp_mask);
1368
1369/**
1370 *      netdev_alloc_skb - allocate an skbuff for rx on a specific device
1371 *      @dev: network device to receive on
1372 *      @length: length to allocate
1373 *
1374 *      Allocate a new &sk_buff and assign it a usage count of one. The
1375 *      buffer has unspecified headroom built in. Users should allocate
1376 *      the headroom they think they need without accounting for the
1377 *      built in space. The built in space is used for optimisations.
1378 *
1379 *      %NULL is returned if there is no free memory. Although this function
1380 *      allocates memory it can be called from an interrupt.
1381 */
1382static inline struct sk_buff *netdev_alloc_skb(struct net_device *dev,
1383                unsigned int length)
1384{
1385        return __netdev_alloc_skb(dev, length, GFP_ATOMIC);
1386}
1387
1388extern struct page *__netdev_alloc_page(struct net_device *dev, gfp_t gfp_mask);
1389
1390/**
1391 *      netdev_alloc_page - allocate a page for ps-rx on a specific device
1392 *      @dev: network device to receive on
1393 *
1394 *      Allocate a new page node local to the specified device.
1395 *
1396 *      %NULL is returned if there is no free memory.
1397 */
1398static inline struct page *netdev_alloc_page(struct net_device *dev)
1399{
1400        return __netdev_alloc_page(dev, GFP_ATOMIC);
1401}
1402
1403static inline void netdev_free_page(struct net_device *dev, struct page *page)
1404{
1405        __free_page(page);
1406}
1407
1408/**
1409 *      skb_clone_writable - is the header of a clone writable
1410 *      @skb: buffer to check
1411 *      @len: length up to which to write
1412 *
1413 *      Returns true if modifying the header part of the cloned buffer
1414 *      does not requires the data to be copied.
1415 */
1416static inline int skb_clone_writable(struct sk_buff *skb, unsigned int len)
1417{
1418        return !skb_header_cloned(skb) &&
1419               skb_headroom(skb) + len <= skb->hdr_len;
1420}
1421
1422static inline int __skb_cow(struct sk_buff *skb, unsigned int headroom,
1423                            int cloned)
1424{
1425        int delta = 0;
1426
1427        if (headroom < NET_SKB_PAD)
1428                headroom = NET_SKB_PAD;
1429        if (headroom > skb_headroom(skb))
1430                delta = headroom - skb_headroom(skb);
1431
1432        if (delta || cloned)
1433                return pskb_expand_head(skb, ALIGN(delta, NET_SKB_PAD), 0,
1434                                        GFP_ATOMIC);
1435        return 0;
1436}
1437
1438/**
1439 *      skb_cow - copy header of skb when it is required
1440 *      @skb: buffer to cow
1441 *      @headroom: needed headroom
1442 *
1443 *      If the skb passed lacks sufficient headroom or its data part
1444 *      is shared, data is reallocated. If reallocation fails, an error
1445 *      is returned and original skb is not changed.
1446 *
1447 *      The result is skb with writable area skb->head...skb->tail
1448 *      and at least @headroom of space at head.
1449 */
1450static inline int skb_cow(struct sk_buff *skb, unsigned int headroom)
1451{
1452        return __skb_cow(skb, headroom, skb_cloned(skb));
1453}
1454
1455/**
1456 *      skb_cow_head - skb_cow but only making the head writable
1457 *      @skb: buffer to cow
1458 *      @headroom: needed headroom
1459 *
1460 *      This function is identical to skb_cow except that we replace the
1461 *      skb_cloned check by skb_header_cloned.  It should be used when
1462 *      you only need to push on some header and do not need to modify
1463 *      the data.
1464 */
1465static inline int skb_cow_head(struct sk_buff *skb, unsigned int headroom)
1466{
1467        return __skb_cow(skb, headroom, skb_header_cloned(skb));
1468}
1469
1470/**
1471 *      skb_padto       - pad an skbuff up to a minimal size
1472 *      @skb: buffer to pad
1473 *      @len: minimal length
1474 *
1475 *      Pads up a buffer to ensure the trailing bytes exist and are
1476 *      blanked. If the buffer already contains sufficient data it
1477 *      is untouched. Otherwise it is extended. Returns zero on
1478 *      success. The skb is freed on error.
1479 */
1480 
1481static inline int skb_padto(struct sk_buff *skb, unsigned int len)
1482{
1483        unsigned int size = skb->len;
1484        if (likely(size >= len))
1485                return 0;
1486        return skb_pad(skb, len - size);
1487}
1488
1489static inline int skb_add_data(struct sk_buff *skb,
1490                               char __user *from, int copy)
1491{
1492        const int off = skb->len;
1493
1494        if (skb->ip_summed == CHECKSUM_NONE) {
1495                int err = 0;
1496                __wsum csum = csum_and_copy_from_user(from, skb_put(skb, copy),
1497                                                            copy, 0, &err);
1498                if (!err) {
1499                        skb->csum = csum_block_add(skb->csum, csum, off);
1500                        return 0;
1501                }
1502        } else if (!copy_from_user(skb_put(skb, copy), from, copy))
1503                return 0;
1504
1505        __skb_trim(skb, off);
1506        return -EFAULT;
1507}
1508
1509static inline int skb_can_coalesce(struct sk_buff *skb, int i,
1510                                   struct page *page, int off)
1511{
1512        if (i) {
1513                struct skb_frag_struct *frag = &skb_shinfo(skb)->frags[i - 1];
1514
1515                return page == frag->page &&
1516                       off == frag->page_offset + frag->size;
1517        }
1518        return 0;
1519}
1520
1521static inline int __skb_linearize(struct sk_buff *skb)
1522{
1523        return __pskb_pull_tail(skb, skb->data_len) ? 0 : -ENOMEM;
1524}
1525
1526/**
1527 *      skb_linearize - convert paged skb to linear one
1528 *      @skb: buffer to linarize
1529 *
1530 *      If there is no free memory -ENOMEM is returned, otherwise zero
1531 *      is returned and the old skb data released.
1532 */
1533static inline int skb_linearize(struct sk_buff *skb)
1534{
1535        return skb_is_nonlinear(skb) ? __skb_linearize(skb) : 0;
1536}
1537
1538/**
1539 *      skb_linearize_cow - make sure skb is linear and writable
1540 *      @skb: buffer to process
1541 *
1542 *      If there is no free memory -ENOMEM is returned, otherwise zero
1543 *      is returned and the old skb data released.
1544 */
1545static inline int skb_linearize_cow(struct sk_buff *skb)
1546{
1547        return skb_is_nonlinear(skb) || skb_cloned(skb) ?
1548               __skb_linearize(skb) : 0;
1549}
1550
1551/**
1552 *      skb_postpull_rcsum - update checksum for received skb after pull
1553 *      @skb: buffer to update
1554 *      @start: start of data before pull
1555 *      @len: length of data pulled
1556 *
1557 *      After doing a pull on a received packet, you need to call this to
1558 *      update the CHECKSUM_COMPLETE checksum, or set ip_summed to
1559 *      CHECKSUM_NONE so that it can be recomputed from scratch.
1560 */
1561
1562static inline void skb_postpull_rcsum(struct sk_buff *skb,
1563                                      const void *start, unsigned int len)
1564{
1565        if (skb->ip_summed == CHECKSUM_COMPLETE)
1566                skb->csum = csum_sub(skb->csum, csum_partial(start, len, 0));
1567}
1568
1569unsigned char *skb_pull_rcsum(struct sk_buff *skb, unsigned int len);
1570
1571/**
1572 *      pskb_trim_rcsum - trim received skb and update checksum
1573 *      @skb: buffer to trim
1574 *      @len: new length
1575 *
1576 *      This is exactly the same as pskb_trim except that it ensures the
1577 *      checksum of received packets are still valid after the operation.
1578 */
1579
1580static inline int pskb_trim_rcsum(struct sk_buff *skb, unsigned int len)
1581{
1582        if (likely(len >= skb->len))
1583                return 0;
1584        if (skb->ip_summed == CHECKSUM_COMPLETE)
1585                skb->ip_summed = CHECKSUM_NONE;
1586        return __pskb_trim(skb, len);
1587}
1588
1589#define skb_queue_walk(queue, skb) \
1590                for (skb = (queue)->next;                                       \
1591                     prefetch(skb->next), (skb != (struct sk_buff *)(queue));   \
1592                     skb = skb->next)
1593
1594#define skb_queue_walk_safe(queue, skb, tmp)                                    \
1595                for (skb = (queue)->next, tmp = skb->next;                      \
1596                     skb != (struct sk_buff *)(queue);                          \
1597                     skb = tmp, tmp = skb->next)
1598
1599#define skb_queue_walk_from(queue, skb)                                         \
1600                for (; prefetch(skb->next), (skb != (struct sk_buff *)(queue)); \
1601                     skb = skb->next)
1602
1603#define skb_queue_walk_from_safe(queue, skb, tmp)                               \
1604                for (tmp = skb->next;                                           \
1605                     skb != (struct sk_buff *)(queue);                          \
1606                     skb = tmp, tmp = skb->next)
1607
1608#define skb_queue_reverse_walk(queue, skb) \
1609                for (skb = (queue)->prev;                                       \
1610                     prefetch(skb->prev), (skb != (struct sk_buff *)(queue));   \
1611                     skb = skb->prev)
1612
1613
1614extern struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned flags,
1615                                           int *peeked, int *err);
1616extern struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned flags,
1617                                         int noblock, int *err);
1618extern unsigned int    datagram_poll(struct file *file, struct socket *sock,
1619                                     struct poll_table_struct *wait);
1620extern int             skb_copy_datagram_iovec(const struct sk_buff *from,
1621                                               int offset, struct iovec *to,
1622                                               int size);
1623extern int             skb_copy_and_csum_datagram_iovec(struct sk_buff *skb,
1624                                                        int hlen,
1625                                                        struct iovec *iov);
1626extern int             skb_copy_datagram_from_iovec(struct sk_buff *skb,
1627                                                    int offset,
1628                                                    struct iovec *from,
1629                                                    int len);
1630extern void            skb_free_datagram(struct sock *sk, struct sk_buff *skb);
1631extern int             skb_kill_datagram(struct sock *sk, struct sk_buff *skb,
1632                                         unsigned int flags);
1633extern __wsum          skb_checksum(const struct sk_buff *skb, int offset,
1634                                    int len, __wsum csum);
1635extern int             skb_copy_bits(const struct sk_buff *skb, int offset,
1636                                     void *to, int len);
1637extern int             skb_store_bits(struct sk_buff *skb, int offset,
1638                                      const void *from, int len);
1639extern __wsum          skb_copy_and_csum_bits(const struct sk_buff *skb,
1640                                              int offset, u8 *to, int len,
1641                                              __wsum csum);
1642extern int             skb_splice_bits(struct sk_buff *skb,
1643                                                unsigned int offset,
1644                                                struct pipe_inode_info *pipe,
1645                                                unsigned int len,
1646                                                unsigned int flags);
1647extern void            skb_copy_and_csum_dev(const struct sk_buff *skb, u8 *to);
1648extern void            skb_split(struct sk_buff *skb,
1649                                 struct sk_buff *skb1, const u32 len);
1650
1651extern struct sk_buff *skb_segment(struct sk_buff *skb, int features);
1652
1653static inline void *skb_header_pointer(const struct sk_buff *skb, int offset,
1654                                       int len, void *buffer)
1655{
1656        int hlen = skb_headlen(skb);
1657
1658        if (hlen - offset >= len)
1659                return skb->data + offset;
1660
1661        if (skb_copy_bits(skb, offset, buffer, len) < 0)
1662                return NULL;
1663
1664        return buffer;
1665}
1666
1667static inline void skb_copy_from_linear_data(const struct sk_buff *skb,
1668                                             void *to,
1669                                             const unsigned int len)
1670{
1671        memcpy(to, skb->data, len);
1672}
1673
1674static inline void skb_copy_from_linear_data_offset(const struct sk_buff *skb,
1675                                                    const int offset, void *to,
1676                                                    const unsigned int len)
1677{
1678        memcpy(to, skb->data + offset, len);
1679}
1680
1681static inline void skb_copy_to_linear_data(struct sk_buff *skb,
1682                                           const void *from,
1683                                           const unsigned int len)
1684{
1685        memcpy(skb->data, from, len);
1686}
1687
1688static inline void skb_copy_to_linear_data_offset(struct sk_buff *skb,
1689                                                  const int offset,
1690                                                  const void *from,
1691                                                  const unsigned int len)
1692{
1693        memcpy(skb->data + offset, from, len);
1694}
1695
1696extern void skb_init(void);
1697
1698/**
1699 *      skb_get_timestamp - get timestamp from a skb
1700 *      @skb: skb to get stamp from
1701 *      @stamp: pointer to struct timeval to store stamp in
1702 *
1703 *      Timestamps are stored in the skb as offsets to a base timestamp.
1704 *      This function converts the offset back to a struct timeval and stores
1705 *      it in stamp.
1706 */
1707static inline void skb_get_timestamp(const struct sk_buff *skb, struct timeval *stamp)
1708{
1709        *stamp = ktime_to_timeval(skb->tstamp);
1710}
1711
1712static inline void __net_timestamp(struct sk_buff *skb)
1713{
1714        skb->tstamp = ktime_get_real();
1715}
1716
1717static inline ktime_t net_timedelta(ktime_t t)
1718{
1719        return ktime_sub(ktime_get_real(), t);
1720}
1721
1722static inline ktime_t net_invalid_timestamp(void)
1723{
1724        return ktime_set(0, 0);
1725}
1726
1727extern __sum16 __skb_checksum_complete_head(struct sk_buff *skb, int len);
1728extern __sum16 __skb_checksum_complete(struct sk_buff *skb);
1729
1730static inline int skb_csum_unnecessary(const struct sk_buff *skb)
1731{
1732        return skb->ip_summed & CHECKSUM_UNNECESSARY;
1733}
1734
1735/**
1736 *      skb_checksum_complete - Calculate checksum of an entire packet
1737 *      @skb: packet to process
1738 *
1739 *      This function calculates the checksum over the entire packet plus
1740 *      the value of skb->csum.  The latter can be used to supply the
1741 *      checksum of a pseudo header as used by TCP/UDP.  It returns the
1742 *      checksum.
1743 *
1744 *      For protocols that contain complete checksums such as ICMP/TCP/UDP,
1745 *      this function can be used to verify that checksum on received
1746 *      packets.  In that case the function should return zero if the
1747 *      checksum is correct.  In particular, this function will return zero
1748 *      if skb->ip_summed is CHECKSUM_UNNECESSARY which indicates that the
1749 *      hardware has already verified the correctness of the checksum.
1750 */
1751static inline __sum16 skb_checksum_complete(struct sk_buff *skb)
1752{
1753        return skb_csum_unnecessary(skb) ?
1754               0 : __skb_checksum_complete(skb);
1755}
1756
1757#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
1758extern void nf_conntrack_destroy(struct nf_conntrack *nfct);
1759static inline void nf_conntrack_put(struct nf_conntrack *nfct)
1760{
1761        if (nfct && atomic_dec_and_test(&nfct->use))
1762                nf_conntrack_destroy(nfct);
1763}
1764static inline void nf_conntrack_get(struct nf_conntrack *nfct)
1765{
1766        if (nfct)
1767                atomic_inc(&nfct->use);
1768}
1769static inline void nf_conntrack_get_reasm(struct sk_buff *skb)
1770{
1771        if (skb)
1772                atomic_inc(&skb->users);
1773}
1774static inline void nf_conntrack_put_reasm(struct sk_buff *skb)
1775{
1776        if (skb)
1777                kfree_skb(skb);
1778}
1779#endif
1780#ifdef CONFIG_BRIDGE_NETFILTER
1781static inline void nf_bridge_put(struct nf_bridge_info *nf_bridge)
1782{
1783        if (nf_bridge && atomic_dec_and_test(&nf_bridge->use))
1784                kfree(nf_bridge);
1785}
1786static inline void nf_bridge_get(struct nf_bridge_info *nf_bridge)
1787{
1788        if (nf_bridge)
1789                atomic_inc(&nf_bridge->use);
1790}
1791#endif /* CONFIG_BRIDGE_NETFILTER */
1792static inline void nf_reset(struct sk_buff *skb)
1793{
1794#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
1795        nf_conntrack_put(skb->nfct);
1796        skb->nfct = NULL;
1797        nf_conntrack_put_reasm(skb->nfct_reasm);
1798        skb->nfct_reasm = NULL;
1799#endif
1800#ifdef CONFIG_BRIDGE_NETFILTER
1801        nf_bridge_put(skb->nf_bridge);
1802        skb->nf_bridge = NULL;
1803#endif
1804}
1805
1806/* Note: This doesn't put any conntrack and bridge info in dst. */
1807static inline void __nf_copy(struct sk_buff *dst, const struct sk_buff *src)
1808{
1809#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
1810        dst->nfct = src->nfct;
1811        nf_conntrack_get(src->nfct);
1812        dst->nfctinfo = src->nfctinfo;
1813        dst->nfct_reasm = src->nfct_reasm;
1814        nf_conntrack_get_reasm(src->nfct_reasm);
1815#endif
1816#ifdef CONFIG_BRIDGE_NETFILTER
1817        dst->nf_bridge  = src->nf_bridge;
1818        nf_bridge_get(src->nf_bridge);
1819#endif
1820}
1821
1822static inline void nf_copy(struct sk_buff *dst, const struct sk_buff *src)
1823{
1824#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
1825        nf_conntrack_put(dst->nfct);
1826        nf_conntrack_put_reasm(dst->nfct_reasm);
1827#endif
1828#ifdef CONFIG_BRIDGE_NETFILTER
1829        nf_bridge_put(dst->nf_bridge);
1830#endif
1831        __nf_copy(dst, src);
1832}
1833
1834#ifdef CONFIG_NETWORK_SECMARK
1835static inline void skb_copy_secmark(struct sk_buff *to, const struct sk_buff *from)
1836{
1837        to->secmark = from->secmark;
1838}
1839
1840static inline void skb_init_secmark(struct sk_buff *skb)
1841{
1842        skb->secmark = 0;
1843}
1844#else
1845static inline void skb_copy_secmark(struct sk_buff *to, const struct sk_buff *from)
1846{ }
1847
1848static inline void skb_init_secmark(struct sk_buff *skb)
1849{ }
1850#endif
1851
1852static inline void skb_set_queue_mapping(struct sk_buff *skb, u16 queue_mapping)
1853{
1854        skb->queue_mapping = queue_mapping;
1855}
1856
1857static inline u16 skb_get_queue_mapping(struct sk_buff *skb)
1858{
1859        return skb->queue_mapping;
1860}
1861
1862static inline void skb_copy_queue_mapping(struct sk_buff *to, const struct sk_buff *from)
1863{
1864        to->queue_mapping = from->queue_mapping;
1865}
1866
1867static inline int skb_is_gso(const struct sk_buff *skb)
1868{
1869        return skb_shinfo(skb)->gso_size;
1870}
1871
1872static inline int skb_is_gso_v6(const struct sk_buff *skb)
1873{
1874        return skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6;
1875}
1876
1877extern void __skb_warn_lro_forwarding(const struct sk_buff *skb);
1878
1879static inline bool skb_warn_if_lro(const struct sk_buff *skb)
1880{
1881        /* LRO sets gso_size but not gso_type, whereas if GSO is really
1882         * wanted then gso_type will be set. */
1883        struct skb_shared_info *shinfo = skb_shinfo(skb);
1884        if (shinfo->gso_size != 0 && unlikely(shinfo->gso_type == 0)) {
1885                __skb_warn_lro_forwarding(skb);
1886                return true;
1887        }
1888        return false;
1889}
1890
1891static inline void skb_forward_csum(struct sk_buff *skb)
1892{
1893        /* Unfortunately we don't support this one.  Any brave souls? */
1894        if (skb->ip_summed == CHECKSUM_COMPLETE)
1895                skb->ip_summed = CHECKSUM_NONE;
1896}
1897
1898bool skb_partial_csum_set(struct sk_buff *skb, u16 start, u16 off);
1899#endif  /* __KERNEL__ */
1900#endif  /* _LINUX_SKBUFF_H */
1901
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