skbuff.c

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/*
 *  Routines having to do with the 'struct sk_buff' memory handlers.
 *
 *  Authors:    Alan Cox <[email protected]>
 *          Florian La Roche <[email protected]>
 *
 *  Fixes:
 *      Alan Cox    :   Fixed the worst of the load
 *                  balancer bugs.
 *      Dave Platt  :   Interrupt stacking fix.
 *  Richard Kooijman    :   Timestamp fixes.
 *      Alan Cox    :   Changed buffer format.
 *      Alan Cox    :   destructor hook for AF_UNIX etc.
 *      Linus Torvalds  :   Better skb_clone.
 *      Alan Cox    :   Added skb_copy.
 *      Alan Cox    :   Added all the changed routines Linus
 *                  only put in the headers
 *      Ray VanTassle   :   Fixed --skb->lock in free
 *      Alan Cox    :   skb_copy copy arp field
 *      Andi Kleen  :   slabified it.
 *      Robert Olsson   :   Removed skb_head_pool
 *
 *  NOTE:
 *      The __skb_ routines should be called with interrupts
 *  disabled, or you better be *real* sure that the operation is atomic
 *  with respect to whatever list is being frobbed (e.g. via lock_sock()
 *  or via disabling bottom half handlers, etc).
 *
 *  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.
 */

/*
 *  The functions in this file will not compile correctly with gcc 2.4.x
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/kmemcheck.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/slab.h>
#include <linux/netdevice.h>
#ifdef CONFIG_NET_CLS_ACT
#include <net/pkt_sched.h>
#endif
#include <linux/string.h>
#include <linux/skbuff.h>
#include <linux/splice.h>
#include <linux/cache.h>
#include <linux/rtnetlink.h>
#include <linux/init.h>
#include <linux/scatterlist.h>
#include <linux/errqueue.h>
#include <linux/prefetch.h>

#include <net/protocol.h>
#include <net/dst.h>
#include <net/sock.h>
#include <net/checksum.h>
#include <net/xfrm.h>

#include <asm/uaccess.h>
#include <trace/events/skb.h>
#include <linux/highmem.h>

struct kmem_cache *skbuff_head_cache __read_mostly;
static struct kmem_cache *skbuff_fclone_cache __read_mostly;

static void sock_pipe_buf_release(struct pipe_inode_info *pipe,
                  struct pipe_buffer *buf)
{
    put_page(buf->page);
}

static void sock_pipe_buf_get(struct pipe_inode_info *pipe,
                struct pipe_buffer *buf)
{
    get_page(buf->page);
}

static int sock_pipe_buf_steal(struct pipe_inode_info *pipe,
                   struct pipe_buffer *buf)
{
    return 1;
}


/* Pipe buffer operations for a socket. */
static const struct pipe_buf_operations sock_pipe_buf_ops = {
    .can_merge = 0,
    .map = generic_pipe_buf_map,
    .unmap = generic_pipe_buf_unmap,
    .confirm = generic_pipe_buf_confirm,
    .release = sock_pipe_buf_release,
    .steal = sock_pipe_buf_steal,
    .get = sock_pipe_buf_get,
};

/*
 *  Keep out-of-line to prevent kernel bloat.
 *  __builtin_return_address is not used because it is not always
 *  reliable.
 */

static void skb_over_panic(struct sk_buff *skb, int sz, void *here)
{
    pr_emerg("%s: text:%p len:%d put:%d head:%p data:%p tail:%#lx end:%#lx dev:%s\n",
         __func__, here, skb->len, sz, skb->head, skb->data,
         (unsigned long)skb->tail, (unsigned long)skb->end,
         skb->dev ? skb->dev->name : "<NULL>");
    BUG();
}

static void skb_under_panic(struct sk_buff *skb, int sz, void *here)
{
    pr_emerg("%s: text:%p len:%d put:%d head:%p data:%p tail:%#lx end:%#lx dev:%s\n",
         __func__, here, skb->len, sz, skb->head, skb->data,
         (unsigned long)skb->tail, (unsigned long)skb->end,
         skb->dev ? skb->dev->name : "<NULL>");
    BUG();
}


/*
 * kmalloc_reserve is a wrapper around kmalloc_node_track_caller that tells
 * the caller if emergency pfmemalloc reserves are being used. If it is and
 * the socket is later found to be SOCK_MEMALLOC then PFMEMALLOC reserves
 * may be used. Otherwise, the packet data may be discarded until enough
 * memory is free
 */
#define kmalloc_reserve(size, gfp, node, pfmemalloc) \
     __kmalloc_reserve(size, gfp, node, _RET_IP_, pfmemalloc)
void *__kmalloc_reserve(size_t size, gfp_t flags, int node, unsigned long ip,
             bool *pfmemalloc)
{
    void *obj;
    bool ret_pfmemalloc = false;

    /*
     * Try a regular allocation, when that fails and we're not entitled
     * to the reserves, fail.
     */
    obj = kmalloc_node_track_caller(size,
                    flags | __GFP_NOMEMALLOC | __GFP_NOWARN,
                    node);
    if (obj || !(gfp_pfmemalloc_allowed(flags)))
        goto out;

    /* Try again but now we are using pfmemalloc reserves */
    ret_pfmemalloc = true;
    obj = kmalloc_node_track_caller(size, flags, node);

out:
    if (pfmemalloc)
        *pfmemalloc = ret_pfmemalloc;

    return obj;
}

/*  Allocate a new skbuff. We do this ourselves so we can fill in a few
 *  'private' fields and also do memory statistics to find all the
 *  [BEEP] leaks.
 *
 */

struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
                int flags, int node)
{
    struct kmem_cache *cache;
    struct skb_shared_info *shinfo;
    struct sk_buff *skb;
    u8 *data;
    bool pfmemalloc;

    cache = (flags & SKB_ALLOC_FCLONE)
        ? skbuff_fclone_cache : skbuff_head_cache;

    if (sk_memalloc_socks() && (flags & SKB_ALLOC_RX))
        gfp_mask |= __GFP_MEMALLOC;

    /* Get the HEAD */
    skb = kmem_cache_alloc_node(cache, gfp_mask & ~__GFP_DMA, node);
    if (!skb)
        goto out;
    prefetchw(skb);

    /* We do our best to align skb_shared_info on a separate cache
     * line. It usually works because kmalloc(X > SMP_CACHE_BYTES) gives
     * aligned memory blocks, unless SLUB/SLAB debug is enabled.
     * Both skb->head and skb_shared_info are cache line aligned.
     */
    size = SKB_DATA_ALIGN(size);
    size += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
    data = kmalloc_reserve(size, gfp_mask, node, &pfmemalloc);
    if (!data)
        goto nodata;
    /* kmalloc(size) might give us more room than requested.
     * Put skb_shared_info exactly at the end of allocated zone,
     * to allow max possible filling before reallocation.
     */
    size = SKB_WITH_OVERHEAD(ksize(data));
    prefetchw(data + size);

    /*
     * Only clear those fields we need to clear, not those that we will
     * actually initialise below. Hence, don't put any more fields after
     * the tail pointer in struct sk_buff!
     */
    memset(skb, 0, offsetof(struct sk_buff, tail));
    /* Account for allocated memory : skb + skb->head */
    skb->truesize = SKB_TRUESIZE(size);
    skb->pfmemalloc = pfmemalloc;
    atomic_set(&skb->users, 1);
    skb->head = data;
    skb->data = data;
    skb_reset_tail_pointer(skb);
    skb->end = skb->tail + size;
#ifdef NET_SKBUFF_DATA_USES_OFFSET
    skb->mac_header = ~0U;
#endif

    /* make sure we initialize shinfo sequentially */
    shinfo = skb_shinfo(skb);
    memset(shinfo, 0, offsetof(struct skb_shared_info, dataref));
    atomic_set(&shinfo->dataref, 1);
    kmemcheck_annotate_variable(shinfo->destructor_arg);

    if (flags & SKB_ALLOC_FCLONE) {
        struct sk_buff *child = skb + 1;
        atomic_t *fclone_ref = (atomic_t *) (child + 1);

        kmemcheck_annotate_bitfield(child, flags1);
        kmemcheck_annotate_bitfield(child, flags2);
        skb->fclone = SKB_FCLONE_ORIG;
        atomic_set(fclone_ref, 1);

        child->fclone = SKB_FCLONE_UNAVAILABLE;
        child->pfmemalloc = pfmemalloc;
    }
out:
    return skb;
nodata:
    kmem_cache_free(cache, skb);
    skb = NULL;
    goto out;
}
EXPORT_SYMBOL(__alloc_skb);

struct sk_buff *build_skb(void *data, unsigned int frag_size)
{
    struct skb_shared_info *shinfo;
    struct sk_buff *skb;
    unsigned int size = frag_size ? : ksize(data);

    skb = kmem_cache_alloc(skbuff_head_cache, GFP_ATOMIC);
    if (!skb)
        return NULL;

    size -= SKB_DATA_ALIGN(sizeof(struct skb_shared_info));

    memset(skb, 0, offsetof(struct sk_buff, tail));
    skb->truesize = SKB_TRUESIZE(size);
    skb->head_frag = frag_size != 0;
    atomic_set(&skb->users, 1);
    skb->head = data;
    skb->data = data;
    skb_reset_tail_pointer(skb);
    skb->end = skb->tail + size;
#ifdef NET_SKBUFF_DATA_USES_OFFSET
    skb->mac_header = ~0U;
#endif

    /* make sure we initialize shinfo sequentially */
    shinfo = skb_shinfo(skb);
    memset(shinfo, 0, offsetof(struct skb_shared_info, dataref));
    atomic_set(&shinfo->dataref, 1);
    kmemcheck_annotate_variable(shinfo->destructor_arg);

    return skb;
}
EXPORT_SYMBOL(build_skb);

struct netdev_alloc_cache {
    struct page_frag    frag;
    /* we maintain a pagecount bias, so that we dont dirty cache line
     * containing page->_count every time we allocate a fragment.
     */
    unsigned int        pagecnt_bias;
};
static DEFINE_PER_CPU(struct netdev_alloc_cache, netdev_alloc_cache);

#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

static void *__netdev_alloc_frag(unsigned int fragsz, gfp_t gfp_mask)
{
    struct netdev_alloc_cache *nc;
    void *data = NULL;
    int order;
    unsigned long flags;

    local_irq_save(flags);
    nc = &__get_cpu_var(netdev_alloc_cache);
    if (unlikely(!nc->frag.page)) {
refill:
        for (order = NETDEV_FRAG_PAGE_MAX_ORDER; ;) {
            gfp_t gfp = gfp_mask;

            if (order)
                gfp |= __GFP_COMP | __GFP_NOWARN;
            nc->frag.page = alloc_pages(gfp, order);
            if (likely(nc->frag.page))
                break;
            if (--order < 0)
                goto end;
        }
        nc->frag.size = PAGE_SIZE << order;
recycle:
        atomic_set(&nc->frag.page->_count, NETDEV_PAGECNT_MAX_BIAS);
        nc->pagecnt_bias = NETDEV_PAGECNT_MAX_BIAS;
        nc->frag.offset = 0;
    }

    if (nc->frag.offset + fragsz > nc->frag.size) {
        /* avoid unnecessary locked operations if possible */
        if ((atomic_read(&nc->frag.page->_count) == nc->pagecnt_bias) ||
            atomic_sub_and_test(nc->pagecnt_bias, &nc->frag.page->_count))
            goto recycle;
        goto refill;
    }

    data = page_address(nc->frag.page) + nc->frag.offset;
    nc->frag.offset += fragsz;
    nc->pagecnt_bias--;
end:
    local_irq_restore(flags);
    return data;
}

void *netdev_alloc_frag(unsigned int fragsz)
{
    return __netdev_alloc_frag(fragsz, GFP_ATOMIC | __GFP_COLD);
}
EXPORT_SYMBOL(netdev_alloc_frag);

struct sk_buff *__netdev_alloc_skb(struct net_device *dev,
                   unsigned int length, gfp_t gfp_mask)
{
    struct sk_buff *skb = NULL;
    unsigned int fragsz = SKB_DATA_ALIGN(length + NET_SKB_PAD) +
                  SKB_DATA_ALIGN(sizeof(struct skb_shared_info));

    if (fragsz <= PAGE_SIZE && !(gfp_mask & (__GFP_WAIT | GFP_DMA))) {
        void *data;

        if (sk_memalloc_socks())
            gfp_mask |= __GFP_MEMALLOC;

        data = __netdev_alloc_frag(fragsz, gfp_mask);

        if (likely(data)) {
            skb = build_skb(data, fragsz);
            if (unlikely(!skb))
                put_page(virt_to_head_page(data));
        }
    } else {
        skb = __alloc_skb(length + NET_SKB_PAD, gfp_mask,
                  SKB_ALLOC_RX, NUMA_NO_NODE);
    }
    if (likely(skb)) {
        skb_reserve(skb, NET_SKB_PAD);
        skb->dev = dev;
    }
    return skb;
}
EXPORT_SYMBOL(__netdev_alloc_skb);

void skb_add_rx_frag(struct sk_buff *skb, int i, struct page *page, int off,
             int size, unsigned int truesize)
{
    skb_fill_page_desc(skb, i, page, off, size);
    skb->len += size;
    skb->data_len += size;
    skb->truesize += truesize;
}
EXPORT_SYMBOL(skb_add_rx_frag);

static void skb_drop_list(struct sk_buff **listp)
{
    struct sk_buff *list = *listp;

    *listp = NULL;

    do {
        struct sk_buff *this = list;
        list = list->next;
        kfree_skb(this);
    } while (list);
}

static inline void skb_drop_fraglist(struct sk_buff *skb)
{
    skb_drop_list(&skb_shinfo(skb)->frag_list);
}

static void skb_clone_fraglist(struct sk_buff *skb)
{
    struct sk_buff *list;

    skb_walk_frags(skb, list)
        skb_get(list);
}

static void skb_free_head(struct sk_buff *skb)
{
    if (skb->head_frag)
        put_page(virt_to_head_page(skb->head));
    else
        kfree(skb->head);
}

static void skb_release_data(struct sk_buff *skb)
{
    if (!skb->cloned ||
        !atomic_sub_return(skb->nohdr ? (1 << SKB_DATAREF_SHIFT) + 1 : 1,
                   &skb_shinfo(skb)->dataref)) {
        if (skb_shinfo(skb)->nr_frags) {
            int i;
            for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
                skb_frag_unref(skb, i);
        }

        /*
         * If skb buf is from userspace, we need to notify the caller
         * the lower device DMA has done;
         */
        if (skb_shinfo(skb)->tx_flags & SKBTX_DEV_ZEROCOPY) {
            struct ubuf_info *uarg;

            uarg = skb_shinfo(skb)->destructor_arg;
            if (uarg->callback)
                uarg->callback(uarg);
        }

        if (skb_has_frag_list(skb))
            skb_drop_fraglist(skb);

        skb_free_head(skb);
    }
}

/*
 *  Free an skbuff by memory without cleaning the state.
 */
static void kfree_skbmem(struct sk_buff *skb)
{
    struct sk_buff *other;
    atomic_t *fclone_ref;

    switch (skb->fclone) {
    case SKB_FCLONE_UNAVAILABLE:
        kmem_cache_free(skbuff_head_cache, skb);
        break;

    case SKB_FCLONE_ORIG:
        fclone_ref = (atomic_t *) (skb + 2);
        if (atomic_dec_and_test(fclone_ref))
            kmem_cache_free(skbuff_fclone_cache, skb);
        break;

    case SKB_FCLONE_CLONE:
        fclone_ref = (atomic_t *) (skb + 1);
        other = skb - 1;

        /* The clone portion is available for
         * fast-cloning again.
         */
        skb->fclone = SKB_FCLONE_UNAVAILABLE;

        if (atomic_dec_and_test(fclone_ref))
            kmem_cache_free(skbuff_fclone_cache, other);
        break;
    }
}

static void skb_release_head_state(struct sk_buff *skb)
{
    skb_dst_drop(skb);
#ifdef CONFIG_XFRM
    secpath_put(skb->sp);
#endif
    if (skb->destructor) {
        WARN_ON(in_irq());
        skb->destructor(skb);
    }
#if IS_ENABLED(CONFIG_NF_CONNTRACK)
    nf_conntrack_put(skb->nfct);
#endif
#ifdef NET_SKBUFF_NF_DEFRAG_NEEDED
    nf_conntrack_put_reasm(skb->nfct_reasm);
#endif
#ifdef CONFIG_BRIDGE_NETFILTER
    nf_bridge_put(skb->nf_bridge);
#endif
/* XXX: IS this still necessary? - JHS */
#ifdef CONFIG_NET_SCHED
    skb->tc_index = 0;
#ifdef CONFIG_NET_CLS_ACT
    skb->tc_verd = 0;
#endif
#endif
}

/* Free everything but the sk_buff shell. */
static void skb_release_all(struct sk_buff *skb)
{
    skb_release_head_state(skb);
    skb_release_data(skb);
}

void __kfree_skb(struct sk_buff *skb)
{
    skb_release_all(skb);
    kfree_skbmem(skb);
}
EXPORT_SYMBOL(__kfree_skb);

void kfree_skb(struct sk_buff *skb)
{
    if (unlikely(!skb))
        return;
    if (likely(atomic_read(&skb->users) == 1))
        smp_rmb();
    else if (likely(!atomic_dec_and_test(&skb->users)))
        return;
    trace_kfree_skb(skb, __builtin_return_address(0));
    __kfree_skb(skb);
}
EXPORT_SYMBOL(kfree_skb);

void consume_skb(struct sk_buff *skb)
{
    if (unlikely(!skb))
        return;
    if (likely(atomic_read(&skb->users) == 1))
        smp_rmb();
    else if (likely(!atomic_dec_and_test(&skb->users)))
        return;
    trace_consume_skb(skb);
    __kfree_skb(skb);
}
EXPORT_SYMBOL(consume_skb);

static void __copy_skb_header(struct sk_buff *new, const struct sk_buff *old)
{
    new->tstamp     = old->tstamp;
    new->dev        = old->dev;
    new->transport_header   = old->transport_header;
    new->network_header = old->network_header;
    new->mac_header     = old->mac_header;
    skb_dst_copy(new, old);
    new->rxhash     = old->rxhash;
    new->ooo_okay       = old->ooo_okay;
    new->l4_rxhash      = old->l4_rxhash;
    new->no_fcs     = old->no_fcs;
#ifdef CONFIG_XFRM
    new->sp         = secpath_get(old->sp);
#endif
    memcpy(new->cb, old->cb, sizeof(old->cb));
    new->csum       = old->csum;
    new->local_df       = old->local_df;
    new->pkt_type       = old->pkt_type;
    new->ip_summed      = old->ip_summed;
    skb_copy_queue_mapping(new, old);
    new->priority       = old->priority;
#if IS_ENABLED(CONFIG_IP_VS)
    new->ipvs_property  = old->ipvs_property;
#endif
    new->pfmemalloc     = old->pfmemalloc;
    new->protocol       = old->protocol;
    new->mark       = old->mark;
    new->skb_iif        = old->skb_iif;
    __nf_copy(new, old);
#if IS_ENABLED(CONFIG_NETFILTER_XT_TARGET_TRACE)
    new->nf_trace       = old->nf_trace;
#endif
#ifdef CONFIG_NET_SCHED
    new->tc_index       = old->tc_index;
#ifdef CONFIG_NET_CLS_ACT
    new->tc_verd        = old->tc_verd;
#endif
#endif
    new->vlan_tci       = old->vlan_tci;

    skb_copy_secmark(new, old);
}

/*
 * You should not add any new code to this function.  Add it to
 * __copy_skb_header above instead.
 */
static struct sk_buff *__skb_clone(struct sk_buff *n, struct sk_buff *skb)
{
#define C(x) n->x = skb->x

    n->next = n->prev = NULL;
    n->sk = NULL;
    __copy_skb_header(n, skb);

    C(len);
    C(data_len);
    C(mac_len);
    n->hdr_len = skb->nohdr ? skb_headroom(skb) : skb->hdr_len;
    n->cloned = 1;
    n->nohdr = 0;
    n->destructor = NULL;
    C(tail);
    C(end);
    C(head);
    C(head_frag);
    C(data);
    C(truesize);
    atomic_set(&n->users, 1);

    atomic_inc(&(skb_shinfo(skb)->dataref));
    skb->cloned = 1;

    return n;
#undef C
}

struct sk_buff *skb_morph(struct sk_buff *dst, struct sk_buff *src)
{
    skb_release_all(dst);
    return __skb_clone(dst, src);
}
EXPORT_SYMBOL_GPL(skb_morph);

int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask)
{
    int i;
    int num_frags = skb_shinfo(skb)->nr_frags;
    struct page *page, *head = NULL;
    struct ubuf_info *uarg = skb_shinfo(skb)->destructor_arg;

    for (i = 0; i < num_frags; i++) {
        u8 *vaddr;
        skb_frag_t *f = &skb_shinfo(skb)->frags[i];

        page = alloc_page(gfp_mask);
        if (!page) {
            while (head) {
                struct page *next = (struct page *)head->private;
                put_page(head);
                head = next;
            }
            return -ENOMEM;
        }
        vaddr = kmap_atomic(skb_frag_page(f));
        memcpy(page_address(page),
               vaddr + f->page_offset, skb_frag_size(f));
        kunmap_atomic(vaddr);
        page->private = (unsigned long)head;
        head = page;
    }

    /* skb frags release userspace buffers */
    for (i = 0; i < num_frags; i++)
        skb_frag_unref(skb, i);

    uarg->callback(uarg);

    /* skb frags point to kernel buffers */
    for (i = num_frags - 1; i >= 0; i--) {
        __skb_fill_page_desc(skb, i, head, 0,
                     skb_shinfo(skb)->frags[i].size);
        head = (struct page *)head->private;
    }

    skb_shinfo(skb)->tx_flags &= ~SKBTX_DEV_ZEROCOPY;
    return 0;
}
EXPORT_SYMBOL_GPL(skb_copy_ubufs);

struct sk_buff *skb_clone(struct sk_buff *skb, gfp_t gfp_mask)
{
    struct sk_buff *n;

    if (skb_orphan_frags(skb, gfp_mask))
        return NULL;

    n = skb + 1;
    if (skb->fclone == SKB_FCLONE_ORIG &&
        n->fclone == SKB_FCLONE_UNAVAILABLE) {
        atomic_t *fclone_ref = (atomic_t *) (n + 1);
        n->fclone = SKB_FCLONE_CLONE;
        atomic_inc(fclone_ref);
    } else {
        if (skb_pfmemalloc(skb))
            gfp_mask |= __GFP_MEMALLOC;

        n = kmem_cache_alloc(skbuff_head_cache, gfp_mask);
        if (!n)
            return NULL;

        kmemcheck_annotate_bitfield(n, flags1);
        kmemcheck_annotate_bitfield(n, flags2);
        n->fclone = SKB_FCLONE_UNAVAILABLE;
    }

    return __skb_clone(n, skb);
}
EXPORT_SYMBOL(skb_clone);

static void copy_skb_header(struct sk_buff *new, const struct sk_buff *old)
{
#ifndef NET_SKBUFF_DATA_USES_OFFSET
    /*
     *  Shift between the two data areas in bytes
     */
    unsigned long offset = new->data - old->data;
#endif

    __copy_skb_header(new, old);

#ifndef NET_SKBUFF_DATA_USES_OFFSET
    /* {transport,network,mac}_header are relative to skb->head */
    new->transport_header += offset;
    new->network_header   += offset;
    if (skb_mac_header_was_set(new))
        new->mac_header       += offset;
#endif
    skb_shinfo(new)->gso_size = skb_shinfo(old)->gso_size;
    skb_shinfo(new)->gso_segs = skb_shinfo(old)->gso_segs;
    skb_shinfo(new)->gso_type = skb_shinfo(old)->gso_type;
}

static inline int skb_alloc_rx_flag(const struct sk_buff *skb)
{
    if (skb_pfmemalloc(skb))
        return SKB_ALLOC_RX;
    return 0;
}

struct sk_buff *skb_copy(const struct sk_buff *skb, gfp_t gfp_mask)
{
    int headerlen = skb_headroom(skb);
    unsigned int size = skb_end_offset(skb) + skb->data_len;
    struct sk_buff *n = __alloc_skb(size, gfp_mask,
                    skb_alloc_rx_flag(skb), NUMA_NO_NODE);

    if (!n)
        return NULL;

    /* Set the data pointer */
    skb_reserve(n, headerlen);
    /* Set the tail pointer and length */
    skb_put(n, skb->len);

    if (skb_copy_bits(skb, -headerlen, n->head, headerlen + skb->len))
        BUG();

    copy_skb_header(n, skb);
    return n;
}
EXPORT_SYMBOL(skb_copy);

struct sk_buff *__pskb_copy(struct sk_buff *skb, int headroom, gfp_t gfp_mask)
{
    unsigned int size = skb_headlen(skb) + headroom;
    struct sk_buff *n = __alloc_skb(size, gfp_mask,
                    skb_alloc_rx_flag(skb), NUMA_NO_NODE);

    if (!n)
        goto out;

    /* Set the data pointer */
    skb_reserve(n, headroom);
    /* Set the tail pointer and length */
    skb_put(n, skb_headlen(skb));
    /* Copy the bytes */
    skb_copy_from_linear_data(skb, n->data, n->len);

    n->truesize += skb->data_len;
    n->data_len  = skb->data_len;
    n->len       = skb->len;

    if (skb_shinfo(skb)->nr_frags) {
        int i;

        if (skb_orphan_frags(skb, gfp_mask)) {
            kfree_skb(n);
            n = NULL;
            goto out;
        }
        for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
            skb_shinfo(n)->frags[i] = skb_shinfo(skb)->frags[i];
            skb_frag_ref(skb, i);
        }
        skb_shinfo(n)->nr_frags = i;
    }

    if (skb_has_frag_list(skb)) {
        skb_shinfo(n)->frag_list = skb_shinfo(skb)->frag_list;
        skb_clone_fraglist(n);
    }

    copy_skb_header(n, skb);
out:
    return n;
}
EXPORT_SYMBOL(__pskb_copy);

int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
             gfp_t gfp_mask)
{
    int i;
    u8 *data;
    int size = nhead + skb_end_offset(skb) + ntail;
    long off;

    BUG_ON(nhead < 0);

    if (skb_shared(skb))
        BUG();

    size = SKB_DATA_ALIGN(size);

    if (skb_pfmemalloc(skb))
        gfp_mask |= __GFP_MEMALLOC;
    data = kmalloc_reserve(size + SKB_DATA_ALIGN(sizeof(struct skb_shared_info)),
                   gfp_mask, NUMA_NO_NODE, NULL);
    if (!data)
        goto nodata;
    size = SKB_WITH_OVERHEAD(ksize(data));

    /* Copy only real data... and, alas, header. This should be
     * optimized for the cases when header is void.
     */
    memcpy(data + nhead, skb->head, skb_tail_pointer(skb) - skb->head);

    memcpy((struct skb_shared_info *)(data + size),
           skb_shinfo(skb),
           offsetof(struct skb_shared_info, frags[skb_shinfo(skb)->nr_frags]));

    /*
     * if shinfo is shared we must drop the old head gracefully, but if it
     * is not we can just drop the old head and let the existing refcount
     * be since all we did is relocate the values
     */
    if (skb_cloned(skb)) {
        /* copy this zero copy skb frags */
        if (skb_orphan_frags(skb, gfp_mask))
            goto nofrags;
        for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
            skb_frag_ref(skb, i);

        if (skb_has_frag_list(skb))
            skb_clone_fraglist(skb);

        skb_release_data(skb);
    } else {
        skb_free_head(skb);
    }
    off = (data + nhead) - skb->head;

    skb->head     = data;
    skb->head_frag = 0;
    skb->data    += off;
#ifdef NET_SKBUFF_DATA_USES_OFFSET
    skb->end      = size;
    off           = nhead;
#else
    skb->end      = skb->head + size;
#endif
    /* {transport,network,mac}_header and tail are relative to skb->head */
    skb->tail         += off;
    skb->transport_header += off;
    skb->network_header   += off;
    if (skb_mac_header_was_set(skb))
        skb->mac_header += off;
    /* Only adjust this if it actually is csum_start rather than csum */
    if (skb->ip_summed == CHECKSUM_PARTIAL)
        skb->csum_start += nhead;
    skb->cloned   = 0;
    skb->hdr_len  = 0;
    skb->nohdr    = 0;
    atomic_set(&skb_shinfo(skb)->dataref, 1);
    return 0;

nofrags:
    kfree(data);
nodata:
    return -ENOMEM;
}
EXPORT_SYMBOL(pskb_expand_head);

/* Make private copy of skb with writable head and some headroom */

struct sk_buff *skb_realloc_headroom(struct sk_buff *skb, unsigned int headroom)
{
    struct sk_buff *skb2;
    int delta = headroom - skb_headroom(skb);

    if (delta <= 0)
        skb2 = pskb_copy(skb, GFP_ATOMIC);
    else {
        skb2 = skb_clone(skb, GFP_ATOMIC);
        if (skb2 && pskb_expand_head(skb2, SKB_DATA_ALIGN(delta), 0,
                         GFP_ATOMIC)) {
            kfree_skb(skb2);
            skb2 = NULL;
        }
    }
    return skb2;
}
EXPORT_SYMBOL(skb_realloc_headroom);

struct sk_buff *skb_copy_expand(const struct sk_buff *skb,
                int newheadroom, int newtailroom,
                gfp_t gfp_mask)
{
    /*
     *  Allocate the copy buffer
     */
    struct sk_buff *n = __alloc_skb(newheadroom + skb->len + newtailroom,
                    gfp_mask, skb_alloc_rx_flag(skb),
                    NUMA_NO_NODE);
    int oldheadroom = skb_headroom(skb);
    int head_copy_len, head_copy_off;
    int off;

    if (!n)
        return NULL;

    skb_reserve(n, newheadroom);

    /* Set the tail pointer and length */
    skb_put(n, skb->len);

    head_copy_len = oldheadroom;
    head_copy_off = 0;
    if (newheadroom <= head_copy_len)
        head_copy_len = newheadroom;
    else
        head_copy_off = newheadroom - head_copy_len;

    /* Copy the linear header and data. */
    if (skb_copy_bits(skb, -head_copy_len, n->head + head_copy_off,
              skb->len + head_copy_len))
        BUG();

    copy_skb_header(n, skb);

    off                  = newheadroom - oldheadroom;
    if (n->ip_summed == CHECKSUM_PARTIAL)
        n->csum_start += off;
#ifdef NET_SKBUFF_DATA_USES_OFFSET
    n->transport_header += off;
    n->network_header   += off;
    if (skb_mac_header_was_set(skb))
        n->mac_header += off;
#endif

    return n;
}
EXPORT_SYMBOL(skb_copy_expand);

int skb_pad(struct sk_buff *skb, int pad)
{
    int err;
    int ntail;

    /* If the skbuff is non linear tailroom is always zero.. */
    if (!skb_cloned(skb) && skb_tailroom(skb) >= pad) {
        memset(skb->data+skb->len, 0, pad);
        return 0;
    }

    ntail = skb->data_len + pad - (skb->end - skb->tail);
    if (likely(skb_cloned(skb) || ntail > 0)) {
        err = pskb_expand_head(skb, 0, ntail, GFP_ATOMIC);
        if (unlikely(err))
            goto free_skb;
    }

    /* FIXME: The use of this function with non-linear skb's really needs
     * to be audited.
     */
    err = skb_linearize(skb);
    if (unlikely(err))
        goto free_skb;

    memset(skb->data + skb->len, 0, pad);
    return 0;

free_skb:
    kfree_skb(skb);
    return err;
}
EXPORT_SYMBOL(skb_pad);

unsigned char *skb_put(struct sk_buff *skb, unsigned int len)
{
    unsigned char *tmp = skb_tail_pointer(skb);
    SKB_LINEAR_ASSERT(skb);
    skb->tail += len;
    skb->len  += len;
    if (unlikely(skb->tail > skb->end))
        skb_over_panic(skb, len, __builtin_return_address(0));
    return tmp;
}
EXPORT_SYMBOL(skb_put);

unsigned char *skb_push(struct sk_buff *skb, unsigned int len)
{
    skb->data -= len;
    skb->len  += len;
    if (unlikely(skb->data<skb->head))
        skb_under_panic(skb, len, __builtin_return_address(0));
    return skb->data;
}
EXPORT_SYMBOL(skb_push);

unsigned char *skb_pull(struct sk_buff *skb, unsigned int len)
{
    return skb_pull_inline(skb, len);
}
EXPORT_SYMBOL(skb_pull);

void skb_trim(struct sk_buff *skb, unsigned int len)
{
    if (skb->len > len)
        __skb_trim(skb, len);
}
EXPORT_SYMBOL(skb_trim);

/* Trims skb to length len. It can change skb pointers.
 */

int ___pskb_trim(struct sk_buff *skb, unsigned int len)
{
    struct sk_buff **fragp;
    struct sk_buff *frag;
    int offset = skb_headlen(skb);
    int nfrags = skb_shinfo(skb)->nr_frags;
    int i;
    int err;

    if (skb_cloned(skb) &&
        unlikely((err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC))))
        return err;

    i = 0;
    if (offset >= len)
        goto drop_pages;

    for (; i < nfrags; i++) {
        int end = offset + skb_frag_size(&skb_shinfo(skb)->frags[i]);

        if (end < len) {
            offset = end;
            continue;
        }

        skb_frag_size_set(&skb_shinfo(skb)->frags[i++], len - offset);

drop_pages:
        skb_shinfo(skb)->nr_frags = i;

        for (; i < nfrags; i++)
            skb_frag_unref(skb, i);

        if (skb_has_frag_list(skb))
            skb_drop_fraglist(skb);
        goto done;
    }

    for (fragp = &skb_shinfo(skb)->frag_list; (frag = *fragp);
         fragp = &frag->next) {
        int end = offset + frag->len;

        if (skb_shared(frag)) {
            struct sk_buff *nfrag;

            nfrag = skb_clone(frag, GFP_ATOMIC);
            if (unlikely(!nfrag))
                return -ENOMEM;

            nfrag->next = frag->next;
            consume_skb(frag);
            frag = nfrag;
            *fragp = frag;
        }

        if (end < len) {
            offset = end;
            continue;
        }

        if (end > len &&
            unlikely((err = pskb_trim(frag, len - offset))))
            return err;

        if (frag->next)
            skb_drop_list(&frag->next);
        break;
    }

done:
    if (len > skb_headlen(skb)) {
        skb->data_len -= skb->len - len;
        skb->len       = len;
    } else {
        skb->len       = len;
        skb->data_len  = 0;
        skb_set_tail_pointer(skb, len);
    }

    return 0;
}
EXPORT_SYMBOL(___pskb_trim);

/* Moves tail of skb head forward, copying data from fragmented part,
 * when it is necessary.
 * 1. It may fail due to malloc failure.
 * 2. It may change skb pointers.
 *
 * It is pretty complicated. Luckily, it is called only in exceptional cases.
 */
unsigned char *__pskb_pull_tail(struct sk_buff *skb, int delta)
{
    /* If skb has not enough free space at tail, get new one
     * plus 128 bytes for future expansions. If we have enough
     * room at tail, reallocate without expansion only if skb is cloned.
     */
    int i, k, eat = (skb->tail + delta) - skb->end;

    if (eat > 0 || skb_cloned(skb)) {
        if (pskb_expand_head(skb, 0, eat > 0 ? eat + 128 : 0,
                     GFP_ATOMIC))
            return NULL;
    }

    if (skb_copy_bits(skb, skb_headlen(skb), skb_tail_pointer(skb), delta))
        BUG();

    /* Optimization: no fragments, no reasons to preestimate
     * size of pulled pages. Superb.
     */
    if (!skb_has_frag_list(skb))
        goto pull_pages;

    /* Estimate size of pulled pages. */
    eat = delta;
    for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
        int size = skb_frag_size(&skb_shinfo(skb)->frags[i]);

        if (size >= eat)
            goto pull_pages;
        eat -= size;
    }

    /* If we need update frag list, we are in troubles.
     * Certainly, it possible to add an offset to skb data,
     * but taking into account that pulling is expected to
     * be very rare operation, it is worth to fight against
     * further bloating skb head and crucify ourselves here instead.
     * Pure masohism, indeed. 8)8)
     */
    if (eat) {
        struct sk_buff *list = skb_shinfo(skb)->frag_list;
        struct sk_buff *clone = NULL;
        struct sk_buff *insp = NULL;

        do {
            BUG_ON(!list);

            if (list->len <= eat) {
                /* Eaten as whole. */
                eat -= list->len;
                list = list->next;
                insp = list;
            } else {
                /* Eaten partially. */

                if (skb_shared(list)) {
                    /* Sucks! We need to fork list. :-( */
                    clone = skb_clone(list, GFP_ATOMIC);
                    if (!clone)
                        return NULL;
                    insp = list->next;
                    list = clone;
                } else {
                    /* This may be pulled without
                     * problems. */
                    insp = list;
                }
                if (!pskb_pull(list, eat)) {
                    kfree_skb(clone);
                    return NULL;
                }
                break;
            }
        } while (eat);

        /* Free pulled out fragments. */
        while ((list = skb_shinfo(skb)->frag_list) != insp) {
            skb_shinfo(skb)->frag_list = list->next;
            kfree_skb(list);
        }
        /* And insert new clone at head. */
        if (clone) {
            clone->next = list;
            skb_shinfo(skb)->frag_list = clone;
        }
    }
    /* Success! Now we may commit changes to skb data. */

pull_pages:
    eat = delta;
    k = 0;
    for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
        int size = skb_frag_size(&skb_shinfo(skb)->frags[i]);

        if (size <= eat) {
            skb_frag_unref(skb, i);
            eat -= size;
        } else {
            skb_shinfo(skb)->frags[k] = skb_shinfo(skb)->frags[i];
            if (eat) {
                skb_shinfo(skb)->frags[k].page_offset += eat;
                skb_frag_size_sub(&skb_shinfo(skb)->frags[k], eat);
                eat = 0;
            }
            k++;
        }
    }
    skb_shinfo(skb)->nr_frags = k;

    skb->tail     += delta;
    skb->data_len -= delta;

    return skb_tail_pointer(skb);
}
EXPORT_SYMBOL(__pskb_pull_tail);

int skb_copy_bits(const struct sk_buff *skb, int offset, void *to, int len)
{
    int start = skb_headlen(skb);
    struct sk_buff *frag_iter;
    int i, copy;

    if (offset > (int)skb->len - len)
        goto fault;

    /* Copy header. */
    if ((copy = start - offset) > 0) {
        if (copy > len)
            copy = len;
        skb_copy_from_linear_data_offset(skb, offset, to, copy);
        if ((len -= copy) == 0)
            return 0;
        offset += copy;
        to     += copy;
    }

    for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
        int end;
        skb_frag_t *f = &skb_shinfo(skb)->frags[i];

        WARN_ON(start > offset + len);

        end = start + skb_frag_size(f);
        if ((copy = end - offset) > 0) {
            u8 *vaddr;

            if (copy > len)
                copy = len;

            vaddr = kmap_atomic(skb_frag_page(f));
            memcpy(to,
                   vaddr + f->page_offset + offset - start,
                   copy);
            kunmap_atomic(vaddr);

            if ((len -= copy) == 0)
                return 0;
            offset += copy;
            to     += copy;
        }
        start = end;
    }

    skb_walk_frags(skb, frag_iter) {
        int end;

        WARN_ON(start > offset + len);

        end = start + frag_iter->len;
        if ((copy = end - offset) > 0) {
            if (copy > len)
                copy = len;
            if (skb_copy_bits(frag_iter, offset - start, to, copy))
                goto fault;
            if ((len -= copy) == 0)
                return 0;
            offset += copy;
            to     += copy;
        }
        start = end;
    }

    if (!len)
        return 0;

fault:
    return -EFAULT;
}
EXPORT_SYMBOL(skb_copy_bits);

/*
 * Callback from splice_to_pipe(), if we need to release some pages
 * at the end of the spd in case we error'ed out in filling the pipe.
 */
static void sock_spd_release(struct splice_pipe_desc *spd, unsigned int i)
{
    put_page(spd->pages[i]);
}

static struct page *linear_to_page(struct page *page, unsigned int *len,
                   unsigned int *offset,
                   struct sk_buff *skb, struct sock *sk)
{
    struct page_frag *pfrag = sk_page_frag(sk);

    if (!sk_page_frag_refill(sk, pfrag))
        return NULL;

    *len = min_t(unsigned int, *len, pfrag->size - pfrag->offset);

    memcpy(page_address(pfrag->page) + pfrag->offset,
           page_address(page) + *offset, *len);
    *offset = pfrag->offset;
    pfrag->offset += *len;

    return pfrag->page;
}

static bool spd_can_coalesce(const struct splice_pipe_desc *spd,
                 struct page *page,
                 unsigned int offset)
{
    return  spd->nr_pages &&
        spd->pages[spd->nr_pages - 1] == page &&
        (spd->partial[spd->nr_pages - 1].offset +
         spd->partial[spd->nr_pages - 1].len == offset);
}

/*
 * Fill page/offset/length into spd, if it can hold more pages.
 */
static bool spd_fill_page(struct splice_pipe_desc *spd,
              struct pipe_inode_info *pipe, struct page *page,
              unsigned int *len, unsigned int offset,
              struct sk_buff *skb, bool linear,
              struct sock *sk)
{
    if (unlikely(spd->nr_pages == MAX_SKB_FRAGS))
        return true;

    if (linear) {
        page = linear_to_page(page, len, &offset, skb, sk);
        if (!page)
            return true;
    }
    if (spd_can_coalesce(spd, page, offset)) {
        spd->partial[spd->nr_pages - 1].len += *len;
        return false;
    }
    get_page(page);
    spd->pages[spd->nr_pages] = page;
    spd->partial[spd->nr_pages].len = *len;
    spd->partial[spd->nr_pages].offset = offset;
    spd->nr_pages++;

    return false;
}

static inline void __segment_seek(struct page **page, unsigned int *poff,
                  unsigned int *plen, unsigned int off)
{
    unsigned long n;

    *poff += off;
    n = *poff / PAGE_SIZE;
    if (n)
        *page = nth_page(*page, n);

    *poff = *poff % PAGE_SIZE;
    *plen -= off;
}

static bool __splice_segment(struct page *page, unsigned int poff,
                 unsigned int plen, unsigned int *off,
                 unsigned int *len, struct sk_buff *skb,
                 struct splice_pipe_desc *spd, bool linear,
                 struct sock *sk,
                 struct pipe_inode_info *pipe)
{
    if (!*len)
        return true;

    /* skip this segment if already processed */
    if (*off >= plen) {
        *off -= plen;
        return false;
    }

    /* ignore any bits we already processed */
    if (*off) {
        __segment_seek(&page, &poff, &plen, *off);
        *off = 0;
    }

    do {
        unsigned int flen = min(*len, plen);

        /* the linear region may spread across several pages  */
        flen = min_t(unsigned int, flen, PAGE_SIZE - poff);

        if (spd_fill_page(spd, pipe, page, &flen, poff, skb, linear, sk))
            return true;

        __segment_seek(&page, &poff, &plen, flen);
        *len -= flen;

    } while (*len && plen);

    return false;
}

/*
 * Map linear and fragment data from the skb to spd. It reports true if the
 * pipe is full or if we already spliced the requested length.
 */
static bool __skb_splice_bits(struct sk_buff *skb, struct pipe_inode_info *pipe,
                  unsigned int *offset, unsigned int *len,
                  struct splice_pipe_desc *spd, struct sock *sk)
{
    int seg;

    /* map the linear part :
     * If skb->head_frag is set, this 'linear' part is backed by a
     * fragment, and if the head is not shared with any clones then
     * we can avoid a copy since we own the head portion of this page.
     */
    if (__splice_segment(virt_to_page(skb->data),
                 (unsigned long) skb->data & (PAGE_SIZE - 1),
                 skb_headlen(skb),
                 offset, len, skb, spd,
                 skb_head_is_locked(skb),
                 sk, pipe))
        return true;

    /*
     * then map the fragments
     */
    for (seg = 0; seg < skb_shinfo(skb)->nr_frags; seg++) {
        const skb_frag_t *f = &skb_shinfo(skb)->frags[seg];

        if (__splice_segment(skb_frag_page(f),
                     f->page_offset, skb_frag_size(f),
                     offset, len, skb, spd, false, sk, pipe))
            return true;
    }

    return false;
}

/*
 * Map data from the skb to a pipe. Should handle both the linear part,
 * the fragments, and the frag list. It does NOT handle frag lists within
 * the frag list, if such a thing exists. We'd probably need to recurse to
 * handle that cleanly.
 */
int skb_splice_bits(struct sk_buff *skb, unsigned int offset,
            struct pipe_inode_info *pipe, unsigned int tlen,
            unsigned int flags)
{
    struct partial_page partial[MAX_SKB_FRAGS];
    struct page *pages[MAX_SKB_FRAGS];
    struct splice_pipe_desc spd = {
        .pages = pages,
        .partial = partial,
        .nr_pages_max = MAX_SKB_FRAGS,
        .flags = flags,
        .ops = &sock_pipe_buf_ops,
        .spd_release = sock_spd_release,
    };
    struct sk_buff *frag_iter;
    struct sock *sk = skb->sk;
    int ret = 0;

    /*
     * __skb_splice_bits() only fails if the output has no room left,
     * so no point in going over the frag_list for the error case.
     */
    if (__skb_splice_bits(skb, pipe, &offset, &tlen, &spd, sk))
        goto done;
    else if (!tlen)
        goto done;

    /*
     * now see if we have a frag_list to map
     */
    skb_walk_frags(skb, frag_iter) {
        if (!tlen)
            break;
        if (__skb_splice_bits(frag_iter, pipe, &offset, &tlen, &spd, sk))
            break;
    }

done:
    if (spd.nr_pages) {
        /*
         * Drop the socket lock, otherwise we have reverse
         * locking dependencies between sk_lock and i_mutex
         * here as compared to sendfile(). We enter here
         * with the socket lock held, and splice_to_pipe() will
         * grab the pipe inode lock. For sendfile() emulation,
         * we call into ->sendpage() with the i_mutex lock held
         * and networking will grab the socket lock.
         */
        release_sock(sk);
        ret = splice_to_pipe(pipe, &spd);
        lock_sock(sk);
    }

    return ret;
}

int skb_store_bits(struct sk_buff *skb, int offset, const void *from, int len)
{
    int start = skb_headlen(skb);
    struct sk_buff *frag_iter;
    int i, copy;

    if (offset > (int)skb->len - len)
        goto fault;

    if ((copy = start - offset) > 0) {
        if (copy > len)
            copy = len;
        skb_copy_to_linear_data_offset(skb, offset, from, copy);
        if ((len -= copy) == 0)
            return 0;
        offset += copy;
        from += copy;
    }

    for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
        skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
        int end;

        WARN_ON(start > offset + len);

        end = start + skb_frag_size(frag);
        if ((copy = end - offset) > 0) {
            u8 *vaddr;

            if (copy > len)
                copy = len;

            vaddr = kmap_atomic(skb_frag_page(frag));
            memcpy(vaddr + frag->page_offset + offset - start,
                   from, copy);
            kunmap_atomic(vaddr);

            if ((len -= copy) == 0)
                return 0;
            offset += copy;
            from += copy;
        }
        start = end;
    }

    skb_walk_frags(skb, frag_iter) {
        int end;

        WARN_ON(start > offset + len);

        end = start + frag_iter->len;
        if ((copy = end - offset) > 0) {
            if (copy > len)
                copy = len;
            if (skb_store_bits(frag_iter, offset - start,
                       from, copy))
                goto fault;
            if ((len -= copy) == 0)
                return 0;
            offset += copy;
            from += copy;
        }
        start = end;
    }
    if (!len)
        return 0;

fault:
    return -EFAULT;
}
EXPORT_SYMBOL(skb_store_bits);

/* Checksum skb data. */

__wsum skb_checksum(const struct sk_buff *skb, int offset,
              int len, __wsum csum)
{
    int start = skb_headlen(skb);
    int i, copy = start - offset;
    struct sk_buff *frag_iter;
    int pos = 0;

    /* Checksum header. */
    if (copy > 0) {
        if (copy > len)
            copy = len;
        csum = csum_partial(skb->data + offset, copy, csum);
        if ((len -= copy) == 0)
            return csum;
        offset += copy;
        pos = copy;
    }

    for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
        int end;
        skb_frag_t *frag = &skb_shinfo(skb)->frags[i];

        WARN_ON(start > offset + len);

        end = start + skb_frag_size(frag);
        if ((copy = end - offset) > 0) {
            __wsum csum2;
            u8 *vaddr;

            if (copy > len)
                copy = len;
            vaddr = kmap_atomic(skb_frag_page(frag));
            csum2 = csum_partial(vaddr + frag->page_offset +
                         offset - start, copy, 0);
            kunmap_atomic(vaddr);
            csum = csum_block_add(csum, csum2, pos);
            if (!(len -= copy))
                return csum;
            offset += copy;
            pos    += copy;
        }
        start = end;
    }

    skb_walk_frags(skb, frag_iter) {
        int end;

        WARN_ON(start > offset + len);

        end = start + frag_iter->len;
        if ((copy = end - offset) > 0) {
            __wsum csum2;
            if (copy > len)
                copy = len;
            csum2 = skb_checksum(frag_iter, offset - start,
                         copy, 0);
            csum = csum_block_add(csum, csum2, pos);
            if ((len -= copy) == 0)
                return csum;
            offset += copy;
            pos    += copy;
        }
        start = end;
    }
    BUG_ON(len);

    return csum;
}
EXPORT_SYMBOL(skb_checksum);

/* Both of above in one bottle. */

__wsum skb_copy_and_csum_bits(const struct sk_buff *skb, int offset,
                    u8 *to, int len, __wsum csum)
{
    int start = skb_headlen(skb);
    int i, copy = start - offset;
    struct sk_buff *frag_iter;
    int pos = 0;

    /* Copy header. */
    if (copy > 0) {
        if (copy > len)
            copy = len;
        csum = csum_partial_copy_nocheck(skb->data + offset, to,
                         copy, csum);
        if ((len -= copy) == 0)
            return csum;
        offset += copy;
        to     += copy;
        pos = copy;
    }

    for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
        int end;

        WARN_ON(start > offset + len);

        end = start + skb_frag_size(&skb_shinfo(skb)->frags[i]);
        if ((copy = end - offset) > 0) {
            __wsum csum2;
            u8 *vaddr;
            skb_frag_t *frag = &skb_shinfo(skb)->frags[i];

            if (copy > len)
                copy = len;
            vaddr = kmap_atomic(skb_frag_page(frag));
            csum2 = csum_partial_copy_nocheck(vaddr +
                              frag->page_offset +
                              offset - start, to,
                              copy, 0);
            kunmap_atomic(vaddr);
            csum = csum_block_add(csum, csum2, pos);
            if (!(len -= copy))
                return csum;
            offset += copy;
            to     += copy;
            pos    += copy;
        }
        start = end;
    }

    skb_walk_frags(skb, frag_iter) {
        __wsum csum2;
        int end;

        WARN_ON(start > offset + len);

        end = start + frag_iter->len;
        if ((copy = end - offset) > 0) {
            if (copy > len)
                copy = len;
            csum2 = skb_copy_and_csum_bits(frag_iter,
                               offset - start,
                               to, copy, 0);
            csum = csum_block_add(csum, csum2, pos);
            if ((len -= copy) == 0)
                return csum;
            offset += copy;
            to     += copy;
            pos    += copy;
        }
        start = end;
    }
    BUG_ON(len);
    return csum;
}
EXPORT_SYMBOL(skb_copy_and_csum_bits);

void skb_copy_and_csum_dev(const struct sk_buff *skb, u8 *to)
{
    __wsum csum;
    long csstart;

    if (skb->ip_summed == CHECKSUM_PARTIAL)
        csstart = skb_checksum_start_offset(skb);
    else
        csstart = skb_headlen(skb);

    BUG_ON(csstart > skb_headlen(skb));

    skb_copy_from_linear_data(skb, to, csstart);

    csum = 0;
    if (csstart != skb->len)
        csum = skb_copy_and_csum_bits(skb, csstart, to + csstart,
                          skb->len - csstart, 0);

    if (skb->ip_summed == CHECKSUM_PARTIAL) {
        long csstuff = csstart + skb->csum_offset;

        *((__sum16 *)(to + csstuff)) = csum_fold(csum);
    }
}
EXPORT_SYMBOL(skb_copy_and_csum_dev);

struct sk_buff *skb_dequeue(struct sk_buff_head *list)
{
    unsigned long flags;
    struct sk_buff *result;

    spin_lock_irqsave(&list->lock, flags);
    result = __skb_dequeue(list);
    spin_unlock_irqrestore(&list->lock, flags);
    return result;
}
EXPORT_SYMBOL(skb_dequeue);

struct sk_buff *skb_dequeue_tail(struct sk_buff_head *list)
{
    unsigned long flags;
    struct sk_buff *result;

    spin_lock_irqsave(&list->lock, flags);
    result = __skb_dequeue_tail(list);
    spin_unlock_irqrestore(&list->lock, flags);
    return result;
}
EXPORT_SYMBOL(skb_dequeue_tail);

void skb_queue_purge(struct sk_buff_head *list)
{
    struct sk_buff *skb;
    while ((skb = skb_dequeue(list)) != NULL)
        kfree_skb(skb);
}
EXPORT_SYMBOL(skb_queue_purge);

void skb_queue_head(struct sk_buff_head *list, struct sk_buff *newsk)
{
    unsigned long flags;

    spin_lock_irqsave(&list->lock, flags);
    __skb_queue_head(list, newsk);
    spin_unlock_irqrestore(&list->lock, flags);
}
EXPORT_SYMBOL(skb_queue_head);

void skb_queue_tail(struct sk_buff_head *list, struct sk_buff *newsk)
{
    unsigned long flags;

    spin_lock_irqsave(&list->lock, flags);
    __skb_queue_tail(list, newsk);
    spin_unlock_irqrestore(&list->lock, flags);
}
EXPORT_SYMBOL(skb_queue_tail);

void skb_unlink(struct sk_buff *skb, struct sk_buff_head *list)
{
    unsigned long flags;

    spin_lock_irqsave(&list->lock, flags);
    __skb_unlink(skb, list);
    spin_unlock_irqrestore(&list->lock, flags);
}
EXPORT_SYMBOL(skb_unlink);

void skb_append(struct sk_buff *old, struct sk_buff *newsk, struct sk_buff_head *list)
{
    unsigned long flags;

    spin_lock_irqsave(&list->lock, flags);
    __skb_queue_after(list, old, newsk);
    spin_unlock_irqrestore(&list->lock, flags);
}
EXPORT_SYMBOL(skb_append);

void skb_insert(struct sk_buff *old, struct sk_buff *newsk, struct sk_buff_head *list)
{
    unsigned long flags;

    spin_lock_irqsave(&list->lock, flags);
    __skb_insert(newsk, old->prev, old, list);
    spin_unlock_irqrestore(&list->lock, flags);
}
EXPORT_SYMBOL(skb_insert);

static inline void skb_split_inside_header(struct sk_buff *skb,
                       struct sk_buff* skb1,
                       const u32 len, const int pos)
{
    int i;

    skb_copy_from_linear_data_offset(skb, len, skb_put(skb1, pos - len),
                     pos - len);
    /* And move data appendix as is. */
    for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
        skb_shinfo(skb1)->frags[i] = skb_shinfo(skb)->frags[i];

    skb_shinfo(skb1)->nr_frags = skb_shinfo(skb)->nr_frags;
    skb_shinfo(skb)->nr_frags  = 0;
    skb1->data_len         = skb->data_len;
    skb1->len          += skb1->data_len;
    skb->data_len          = 0;
    skb->len           = len;
    skb_set_tail_pointer(skb, len);
}

static inline void skb_split_no_header(struct sk_buff *skb,
                       struct sk_buff* skb1,
                       const u32 len, int pos)
{
    int i, k = 0;
    const int nfrags = skb_shinfo(skb)->nr_frags;

    skb_shinfo(skb)->nr_frags = 0;
    skb1->len         = skb1->data_len = skb->len - len;
    skb->len          = len;
    skb->data_len         = len - pos;

    for (i = 0; i < nfrags; i++) {
        int size = skb_frag_size(&skb_shinfo(skb)->frags[i]);

        if (pos + size > len) {
            skb_shinfo(skb1)->frags[k] = skb_shinfo(skb)->frags[i];

            if (pos < len) {
                /* Split frag.
                 * We have two variants in this case:
                 * 1. Move all the frag to the second
                 *    part, if it is possible. F.e.
                 *    this approach is mandatory for TUX,
                 *    where splitting is expensive.
                 * 2. Split is accurately. We make this.
                 */
                skb_frag_ref(skb, i);
                skb_shinfo(skb1)->frags[0].page_offset += len - pos;
                skb_frag_size_sub(&skb_shinfo(skb1)->frags[0], len - pos);
                skb_frag_size_set(&skb_shinfo(skb)->frags[i], len - pos);
                skb_shinfo(skb)->nr_frags++;
            }
            k++;
        } else
            skb_shinfo(skb)->nr_frags++;
        pos += size;
    }
    skb_shinfo(skb1)->nr_frags = k;
}

void skb_split(struct sk_buff *skb, struct sk_buff *skb1, const u32 len)
{
    int pos = skb_headlen(skb);

    if (len < pos)  /* Split line is inside header. */
        skb_split_inside_header(skb, skb1, len, pos);
    else        /* Second chunk has no header, nothing to copy. */
        skb_split_no_header(skb, skb1, len, pos);
}
EXPORT_SYMBOL(skb_split);

/* Shifting from/to a cloned skb is a no-go.
 *
 * Caller cannot keep skb_shinfo related pointers past calling here!
 */
static int skb_prepare_for_shift(struct sk_buff *skb)
{
    return skb_cloned(skb) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
}

int skb_shift(struct sk_buff *tgt, struct sk_buff *skb, int shiftlen)
{
    int from, to, merge, todo;
    struct skb_frag_struct *fragfrom, *fragto;

    BUG_ON(shiftlen > skb->len);
    BUG_ON(skb_headlen(skb));   /* Would corrupt stream */

    todo = shiftlen;
    from = 0;
    to = skb_shinfo(tgt)->nr_frags;
    fragfrom = &skb_shinfo(skb)->frags[from];

    /* Actual merge is delayed until the point when we know we can
     * commit all, so that we don't have to undo partial changes
     */
    if (!to ||
        !skb_can_coalesce(tgt, to, skb_frag_page(fragfrom),
                  fragfrom->page_offset)) {
        merge = -1;
    } else {
        merge = to - 1;

        todo -= skb_frag_size(fragfrom);
        if (todo < 0) {
            if (skb_prepare_for_shift(skb) ||
                skb_prepare_for_shift(tgt))
                return 0;

            /* All previous frag pointers might be stale! */
            fragfrom = &skb_shinfo(skb)->frags[from];
            fragto = &skb_shinfo(tgt)->frags[merge];

            skb_frag_size_add(fragto, shiftlen);
            skb_frag_size_sub(fragfrom, shiftlen);
            fragfrom->page_offset += shiftlen;

            goto onlymerged;
        }

        from++;
    }

    /* Skip full, not-fitting skb to avoid expensive operations */
    if ((shiftlen == skb->len) &&
        (skb_shinfo(skb)->nr_frags - from) > (MAX_SKB_FRAGS - to))
        return 0;

    if (skb_prepare_for_shift(skb) || skb_prepare_for_shift(tgt))
        return 0;

    while ((todo > 0) && (from < skb_shinfo(skb)->nr_frags)) {
        if (to == MAX_SKB_FRAGS)
            return 0;

        fragfrom = &skb_shinfo(skb)->frags[from];
        fragto = &skb_shinfo(tgt)->frags[to];

        if (todo >= skb_frag_size(fragfrom)) {
            *fragto = *fragfrom;
            todo -= skb_frag_size(fragfrom);
            from++;
            to++;

        } else {
            __skb_frag_ref(fragfrom);
            fragto->page = fragfrom->page;
            fragto->page_offset = fragfrom->page_offset;
            skb_frag_size_set(fragto, todo);

            fragfrom->page_offset += todo;
            skb_frag_size_sub(fragfrom, todo);
            todo = 0;

            to++;
            break;
        }
    }

    /* Ready to "commit" this state change to tgt */
    skb_shinfo(tgt)->nr_frags = to;

    if (merge >= 0) {
        fragfrom = &skb_shinfo(skb)->frags[0];
        fragto = &skb_shinfo(tgt)->frags[merge];

        skb_frag_size_add(fragto, skb_frag_size(fragfrom));
        __skb_frag_unref(fragfrom);
    }

    /* Reposition in the original skb */
    to = 0;
    while (from < skb_shinfo(skb)->nr_frags)
        skb_shinfo(skb)->frags[to++] = skb_shinfo(skb)->frags[from++];
    skb_shinfo(skb)->nr_frags = to;

    BUG_ON(todo > 0 && !skb_shinfo(skb)->nr_frags);

onlymerged:
    /* Most likely the tgt won't ever need its checksum anymore, skb on
     * the other hand might need it if it needs to be resent
     */
    tgt->ip_summed = CHECKSUM_PARTIAL;
    skb->ip_summed = CHECKSUM_PARTIAL;

    /* Yak, is it really working this way? Some helper please? */
    skb->len -= shiftlen;
    skb->data_len -= shiftlen;
    skb->truesize -= shiftlen;
    tgt->len += shiftlen;
    tgt->data_len += shiftlen;
    tgt->truesize += shiftlen;

    return shiftlen;
}

void skb_prepare_seq_read(struct sk_buff *skb, unsigned int from,
              unsigned int to, struct skb_seq_state *st)
{
    st->lower_offset = from;
    st->upper_offset = to;
    st->root_skb = st->cur_skb = skb;
    st->frag_idx = st->stepped_offset = 0;
    st->frag_data = NULL;
}
EXPORT_SYMBOL(skb_prepare_seq_read);

unsigned int skb_seq_read(unsigned int consumed, const u8 **data,
              struct skb_seq_state *st)
{
    unsigned int block_limit, abs_offset = consumed + st->lower_offset;
    skb_frag_t *frag;

    if (unlikely(abs_offset >= st->upper_offset))
        return 0;

next_skb:
    block_limit = skb_headlen(st->cur_skb) + st->stepped_offset;

    if (abs_offset < block_limit && !st->frag_data) {
        *data = st->cur_skb->data + (abs_offset - st->stepped_offset);
        return block_limit - abs_offset;
    }

    if (st->frag_idx == 0 && !st->frag_data)
        st->stepped_offset += skb_headlen(st->cur_skb);

    while (st->frag_idx < skb_shinfo(st->cur_skb)->nr_frags) {
        frag = &skb_shinfo(st->cur_skb)->frags[st->frag_idx];
        block_limit = skb_frag_size(frag) + st->stepped_offset;

        if (abs_offset < block_limit) {
            if (!st->frag_data)
                st->frag_data = kmap_atomic(skb_frag_page(frag));

            *data = (u8 *) st->frag_data + frag->page_offset +
                (abs_offset - st->stepped_offset);

            return block_limit - abs_offset;
        }

        if (st->frag_data) {
            kunmap_atomic(st->frag_data);
            st->frag_data = NULL;
        }

        st->frag_idx++;
        st->stepped_offset += skb_frag_size(frag);
    }

    if (st->frag_data) {
        kunmap_atomic(st->frag_data);
        st->frag_data = NULL;
    }

    if (st->root_skb == st->cur_skb && skb_has_frag_list(st->root_skb)) {
        st->cur_skb = skb_shinfo(st->root_skb)->frag_list;
        st->frag_idx = 0;
        goto next_skb;
    } else if (st->cur_skb->next) {
        st->cur_skb = st->cur_skb->next;
        st->frag_idx = 0;
        goto next_skb;
    }

    return 0;
}
EXPORT_SYMBOL(skb_seq_read);

void skb_abort_seq_read(struct skb_seq_state *st)
{
    if (st->frag_data)
        kunmap_atomic(st->frag_data);
}
EXPORT_SYMBOL(skb_abort_seq_read);

#define TS_SKB_CB(state)    ((struct skb_seq_state *) &((state)->cb))

static unsigned int skb_ts_get_next_block(unsigned int offset, const u8 **text,
                      struct ts_config *conf,
                      struct ts_state *state)
{
    return skb_seq_read(offset, text, TS_SKB_CB(state));
}

static void skb_ts_finish(struct ts_config *conf, struct ts_state *state)
{
    skb_abort_seq_read(TS_SKB_CB(state));
}

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

    config->get_next_block = skb_ts_get_next_block;
    config->finish = skb_ts_finish;

    skb_prepare_seq_read(skb, from, to, TS_SKB_CB(state));

    ret = textsearch_find(config, state);
    return (ret <= to - from ? ret : UINT_MAX);
}
EXPORT_SYMBOL(skb_find_text);

int skb_append_datato_frags(struct sock *sk, struct sk_buff *skb,
            int (*getfrag)(void *from, char *to, int offset,
                    int len, int odd, struct sk_buff *skb),
            void *from, int length)
{
    int frg_cnt = 0;
    skb_frag_t *frag = NULL;
    struct page *page = NULL;
    int copy, left;
    int offset = 0;
    int ret;

    do {
        /* Return error if we don't have space for new frag */
        frg_cnt = skb_shinfo(skb)->nr_frags;
        if (frg_cnt >= MAX_SKB_FRAGS)
            return -EFAULT;

        /* allocate a new page for next frag */
        page = alloc_pages(sk->sk_allocation, 0);

        /* If alloc_page fails just return failure and caller will
         * free previous allocated pages by doing kfree_skb()
         */
        if (page == NULL)
            return -ENOMEM;

        /* initialize the next frag */
        skb_fill_page_desc(skb, frg_cnt, page, 0, 0);
        skb->truesize += PAGE_SIZE;
        atomic_add(PAGE_SIZE, &sk->sk_wmem_alloc);

        /* get the new initialized frag */
        frg_cnt = skb_shinfo(skb)->nr_frags;
        frag = &skb_shinfo(skb)->frags[frg_cnt - 1];

        /* copy the user data to page */
        left = PAGE_SIZE - frag->page_offset;
        copy = (length > left)? left : length;

        ret = getfrag(from, skb_frag_address(frag) + skb_frag_size(frag),
                offset, copy, 0, skb);
        if (ret < 0)
            return -EFAULT;

        /* copy was successful so update the size parameters */
        skb_frag_size_add(frag, copy);
        skb->len += copy;
        skb->data_len += copy;
        offset += copy;
        length -= copy;

    } while (length > 0);

    return 0;
}
EXPORT_SYMBOL(skb_append_datato_frags);

unsigned char *skb_pull_rcsum(struct sk_buff *skb, unsigned int len)
{
    BUG_ON(len > skb->len);
    skb->len -= len;
    BUG_ON(skb->len < skb->data_len);
    skb_postpull_rcsum(skb, skb->data, len);
    return skb->data += len;
}
EXPORT_SYMBOL_GPL(skb_pull_rcsum);

struct sk_buff *skb_segment(struct sk_buff *skb, netdev_features_t features)
{
    struct sk_buff *segs = NULL;
    struct sk_buff *tail = NULL;
    struct sk_buff *fskb = skb_shinfo(skb)->frag_list;
    unsigned int mss = skb_shinfo(skb)->gso_size;
    unsigned int doffset = skb->data - skb_mac_header(skb);
    unsigned int offset = doffset;
    unsigned int headroom;
    unsigned int len;
    int sg = !!(features & NETIF_F_SG);
    int nfrags = skb_shinfo(skb)->nr_frags;
    int err = -ENOMEM;
    int i = 0;
    int pos;

    __skb_push(skb, doffset);
    headroom = skb_headroom(skb);
    pos = skb_headlen(skb);

    do {
        struct sk_buff *nskb;
        skb_frag_t *frag;
        int hsize;
        int size;

        len = skb->len - offset;
        if (len > mss)
            len = mss;

        hsize = skb_headlen(skb) - offset;
        if (hsize < 0)
            hsize = 0;
        if (hsize > len || !sg)
            hsize = len;

        if (!hsize && i >= nfrags) {
            BUG_ON(fskb->len != len);

            pos += len;
            nskb = skb_clone(fskb, GFP_ATOMIC);
            fskb = fskb->next;

            if (unlikely(!nskb))
                goto err;

            hsize = skb_end_offset(nskb);
            if (skb_cow_head(nskb, doffset + headroom)) {
                kfree_skb(nskb);
                goto err;
            }

            nskb->truesize += skb_end_offset(nskb) - hsize;
            skb_release_head_state(nskb);
            __skb_push(nskb, doffset);
        } else {
            nskb = __alloc_skb(hsize + doffset + headroom,
                       GFP_ATOMIC, skb_alloc_rx_flag(skb),
                       NUMA_NO_NODE);

            if (unlikely(!nskb))
                goto err;

            skb_reserve(nskb, headroom);
            __skb_put(nskb, doffset);
        }

        if (segs)
            tail->next = nskb;
        else
            segs = nskb;
        tail = nskb;

        __copy_skb_header(nskb, skb);
        nskb->mac_len = skb->mac_len;

        /* nskb and skb might have different headroom */
        if (nskb->ip_summed == CHECKSUM_PARTIAL)
            nskb->csum_start += skb_headroom(nskb) - headroom;

        skb_reset_mac_header(nskb);
        skb_set_network_header(nskb, skb->mac_len);
        nskb->transport_header = (nskb->network_header +
                      skb_network_header_len(skb));
        skb_copy_from_linear_data(skb, nskb->data, doffset);

        if (fskb != skb_shinfo(skb)->frag_list)
            continue;

        if (!sg) {
            nskb->ip_summed = CHECKSUM_NONE;
            nskb->csum = skb_copy_and_csum_bits(skb, offset,
                                skb_put(nskb, len),
                                len, 0);
            continue;
        }

        frag = skb_shinfo(nskb)->frags;

        skb_copy_from_linear_data_offset(skb, offset,
                         skb_put(nskb, hsize), hsize);

        while (pos < offset + len && i < nfrags) {
            *frag = skb_shinfo(skb)->frags[i];
            __skb_frag_ref(frag);
            size = skb_frag_size(frag);

            if (pos < offset) {
                frag->page_offset += offset - pos;
                skb_frag_size_sub(frag, offset - pos);
            }

            skb_shinfo(nskb)->nr_frags++;

            if (pos + size <= offset + len) {
                i++;
                pos += size;
            } else {
                skb_frag_size_sub(frag, pos + size - (offset + len));
                goto skip_fraglist;
            }

            frag++;
        }

        if (pos < offset + len) {
            struct sk_buff *fskb2 = fskb;

            BUG_ON(pos + fskb->len != offset + len);

            pos += fskb->len;
            fskb = fskb->next;

            if (fskb2->next) {
                fskb2 = skb_clone(fskb2, GFP_ATOMIC);
                if (!fskb2)
                    goto err;
            } else
                skb_get(fskb2);

            SKB_FRAG_ASSERT(nskb);
            skb_shinfo(nskb)->frag_list = fskb2;
        }

skip_fraglist:
        nskb->data_len = len - hsize;
        nskb->len += nskb->data_len;
        nskb->truesize += nskb->data_len;
    } while ((offset += len) < skb->len);

    return segs;

err:
    while ((skb = segs)) {
        segs = skb->next;
        kfree_skb(skb);
    }
    return ERR_PTR(err);
}
EXPORT_SYMBOL_GPL(skb_segment);

int skb_gro_receive(struct sk_buff **head, struct sk_buff *skb)
{
    struct sk_buff *p = *head;
    struct sk_buff *nskb;
    struct skb_shared_info *skbinfo = skb_shinfo(skb);
    struct skb_shared_info *pinfo = skb_shinfo(p);
    unsigned int headroom;
    unsigned int len = skb_gro_len(skb);
    unsigned int offset = skb_gro_offset(skb);
    unsigned int headlen = skb_headlen(skb);
    unsigned int delta_truesize;

    if (p->len + len >= 65536)
        return -E2BIG;

    if (pinfo->frag_list)
        goto merge;
    else if (headlen <= offset) {
        skb_frag_t *frag;
        skb_frag_t *frag2;
        int i = skbinfo->nr_frags;
        int nr_frags = pinfo->nr_frags + i;

        offset -= headlen;

        if (nr_frags > MAX_SKB_FRAGS)
            return -E2BIG;

        pinfo->nr_frags = nr_frags;
        skbinfo->nr_frags = 0;

        frag = pinfo->frags + nr_frags;
        frag2 = skbinfo->frags + i;
        do {
            *--frag = *--frag2;
        } while (--i);

        frag->page_offset += offset;
        skb_frag_size_sub(frag, offset);

        /* all fragments truesize : remove (head size + sk_buff) */
        delta_truesize = skb->truesize -
                 SKB_TRUESIZE(skb_end_offset(skb));

        skb->truesize -= skb->data_len;
        skb->len -= skb->data_len;
        skb->data_len = 0;

        NAPI_GRO_CB(skb)->free = NAPI_GRO_FREE;
        goto done;
    } else if (skb->head_frag) {
        int nr_frags = pinfo->nr_frags;
        skb_frag_t *frag = pinfo->frags + nr_frags;
        struct page *page = virt_to_head_page(skb->head);
        unsigned int first_size = headlen - offset;
        unsigned int first_offset;

        if (nr_frags + 1 + skbinfo->nr_frags > MAX_SKB_FRAGS)
            return -E2BIG;

        first_offset = skb->data -
                   (unsigned char *)page_address(page) +
                   offset;

        pinfo->nr_frags = nr_frags + 1 + skbinfo->nr_frags;

        frag->page.p      = page;
        frag->page_offset = first_offset;
        skb_frag_size_set(frag, first_size);

        memcpy(frag + 1, skbinfo->frags, sizeof(*frag) * skbinfo->nr_frags);
        /* We dont need to clear skbinfo->nr_frags here */

        delta_truesize = skb->truesize - SKB_DATA_ALIGN(sizeof(struct sk_buff));
        NAPI_GRO_CB(skb)->free = NAPI_GRO_FREE_STOLEN_HEAD;
        goto done;
    } else if (skb_gro_len(p) != pinfo->gso_size)
        return -E2BIG;

    headroom = skb_headroom(p);
    nskb = alloc_skb(headroom + skb_gro_offset(p), GFP_ATOMIC);
    if (unlikely(!nskb))
        return -ENOMEM;

    __copy_skb_header(nskb, p);
    nskb->mac_len = p->mac_len;

    skb_reserve(nskb, headroom);
    __skb_put(nskb, skb_gro_offset(p));

    skb_set_mac_header(nskb, skb_mac_header(p) - p->data);
    skb_set_network_header(nskb, skb_network_offset(p));
    skb_set_transport_header(nskb, skb_transport_offset(p));

    __skb_pull(p, skb_gro_offset(p));
    memcpy(skb_mac_header(nskb), skb_mac_header(p),
           p->data - skb_mac_header(p));

    *NAPI_GRO_CB(nskb) = *NAPI_GRO_CB(p);
    skb_shinfo(nskb)->frag_list = p;
    skb_shinfo(nskb)->gso_size = pinfo->gso_size;
    pinfo->gso_size = 0;
    skb_header_release(p);
    NAPI_GRO_CB(nskb)->last = p;

    nskb->data_len += p->len;
    nskb->truesize += p->truesize;
    nskb->len += p->len;

    *head = nskb;
    nskb->next = p->next;
    p->next = NULL;

    p = nskb;

merge:
    delta_truesize = skb->truesize;
    if (offset > headlen) {
        unsigned int eat = offset - headlen;

        skbinfo->frags[0].page_offset += eat;
        skb_frag_size_sub(&skbinfo->frags[0], eat);
        skb->data_len -= eat;
        skb->len -= eat;
        offset = headlen;
    }

    __skb_pull(skb, offset);

    NAPI_GRO_CB(p)->last->next = skb;
    NAPI_GRO_CB(p)->last = skb;
    skb_header_release(skb);

done:
    NAPI_GRO_CB(p)->count++;
    p->data_len += len;
    p->truesize += delta_truesize;
    p->len += len;

    NAPI_GRO_CB(skb)->same_flow = 1;
    return 0;
}
EXPORT_SYMBOL_GPL(skb_gro_receive);

void __init skb_init(void)
{
    skbuff_head_cache = kmem_cache_create("skbuff_head_cache",
                          sizeof(struct sk_buff),
                          0,
                          SLAB_HWCACHE_ALIGN|SLAB_PANIC,
                          NULL);
    skbuff_fclone_cache = kmem_cache_create("skbuff_fclone_cache",
                        (2*sizeof(struct sk_buff)) +
                        sizeof(atomic_t),
                        0,
                        SLAB_HWCACHE_ALIGN|SLAB_PANIC,
                        NULL);
}

static int
__skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
{
    int start = skb_headlen(skb);
    int i, copy = start - offset;
    struct sk_buff *frag_iter;
    int elt = 0;

    if (copy > 0) {
        if (copy > len)
            copy = len;
        sg_set_buf(sg, skb->data + offset, copy);
        elt++;
        if ((len -= copy) == 0)
            return elt;
        offset += copy;
    }

    for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
        int end;

        WARN_ON(start > offset + len);

        end = start + skb_frag_size(&skb_shinfo(skb)->frags[i]);
        if ((copy = end - offset) > 0) {
            skb_frag_t *frag = &skb_shinfo(skb)->frags[i];

            if (copy > len)
                copy = len;
            sg_set_page(&sg[elt], skb_frag_page(frag), copy,
                    frag->page_offset+offset-start);
            elt++;
            if (!(len -= copy))
                return elt;
            offset += copy;
        }
        start = end;
    }

    skb_walk_frags(skb, frag_iter) {
        int end;

        WARN_ON(start > offset + len);

        end = start + frag_iter->len;
        if ((copy = end - offset) > 0) {
            if (copy > len)
                copy = len;
            elt += __skb_to_sgvec(frag_iter, sg+elt, offset - start,
                          copy);
            if ((len -= copy) == 0)
                return elt;
            offset += copy;
        }
        start = end;
    }
    BUG_ON(len);
    return elt;
}

int skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
{
    int nsg = __skb_to_sgvec(skb, sg, offset, len);

    sg_mark_end(&sg[nsg - 1]);

    return nsg;
}
EXPORT_SYMBOL_GPL(skb_to_sgvec);

int skb_cow_data(struct sk_buff *skb, int tailbits, struct sk_buff **trailer)
{
    int copyflag;
    int elt;
    struct sk_buff *skb1, **skb_p;

    /* If skb is cloned or its head is paged, reallocate
     * head pulling out all the pages (pages are considered not writable
     * at the moment even if they are anonymous).
     */
    if ((skb_cloned(skb) || skb_shinfo(skb)->nr_frags) &&
        __pskb_pull_tail(skb, skb_pagelen(skb)-skb_headlen(skb)) == NULL)
        return -ENOMEM;

    /* Easy case. Most of packets will go this way. */
    if (!skb_has_frag_list(skb)) {
        /* A little of trouble, not enough of space for trailer.
         * This should not happen, when stack is tuned to generate
         * good frames. OK, on miss we reallocate and reserve even more
         * space, 128 bytes is fair. */

        if (skb_tailroom(skb) < tailbits &&
            pskb_expand_head(skb, 0, tailbits-skb_tailroom(skb)+128, GFP_ATOMIC))
            return -ENOMEM;

        /* Voila! */
        *trailer = skb;
        return 1;
    }

    /* Misery. We are in troubles, going to mincer fragments... */

    elt = 1;
    skb_p = &skb_shinfo(skb)->frag_list;
    copyflag = 0;

    while ((skb1 = *skb_p) != NULL) {
        int ntail = 0;

        /* The fragment is partially pulled by someone,
         * this can happen on input. Copy it and everything
         * after it. */

        if (skb_shared(skb1))
            copyflag = 1;

        /* If the skb is the last, worry about trailer. */

        if (skb1->next == NULL && tailbits) {
            if (skb_shinfo(skb1)->nr_frags ||
                skb_has_frag_list(skb1) ||
                skb_tailroom(skb1) < tailbits)
                ntail = tailbits + 128;
        }

        if (copyflag ||
            skb_cloned(skb1) ||
            ntail ||
            skb_shinfo(skb1)->nr_frags ||
            skb_has_frag_list(skb1)) {
            struct sk_buff *skb2;

            /* Fuck, we are miserable poor guys... */
            if (ntail == 0)
                skb2 = skb_copy(skb1, GFP_ATOMIC);
            else
                skb2 = skb_copy_expand(skb1,
                               skb_headroom(skb1),
                               ntail,
                               GFP_ATOMIC);
            if (unlikely(skb2 == NULL))
                return -ENOMEM;

            if (skb1->sk)
                skb_set_owner_w(skb2, skb1->sk);

            /* Looking around. Are we still alive?
             * OK, link new skb, drop old one */

            skb2->next = skb1->next;
            *skb_p = skb2;
            kfree_skb(skb1);
            skb1 = skb2;
        }
        elt++;
        *trailer = skb1;
        skb_p = &skb1->next;
    }

    return elt;
}
EXPORT_SYMBOL_GPL(skb_cow_data);

static void sock_rmem_free(struct sk_buff *skb)
{
    struct sock *sk = skb->sk;

    atomic_sub(skb->truesize, &sk->sk_rmem_alloc);
}

/*
 * Note: We dont mem charge error packets (no sk_forward_alloc changes)
 */
int sock_queue_err_skb(struct sock *sk, struct sk_buff *skb)
{
    int len = skb->len;

    if (atomic_read(&sk->sk_rmem_alloc) + skb->truesize >=
        (unsigned int)sk->sk_rcvbuf)
        return -ENOMEM;

    skb_orphan(skb);
    skb->sk = sk;
    skb->destructor = sock_rmem_free;
    atomic_add(skb->truesize, &sk->sk_rmem_alloc);

    /* before exiting rcu section, make sure dst is refcounted */
    skb_dst_force(skb);

    skb_queue_tail(&sk->sk_error_queue, skb);
    if (!sock_flag(sk, SOCK_DEAD))
        sk->sk_data_ready(sk, len);
    return 0;
}
EXPORT_SYMBOL(sock_queue_err_skb);

void skb_tstamp_tx(struct sk_buff *orig_skb,
        struct skb_shared_hwtstamps *hwtstamps)
{
    struct sock *sk = orig_skb->sk;
    struct sock_exterr_skb *serr;
    struct sk_buff *skb;
    int err;

    if (!sk)
        return;

    skb = skb_clone(orig_skb, GFP_ATOMIC);
    if (!skb)
        return;

    if (hwtstamps) {
        *skb_hwtstamps(skb) =
            *hwtstamps;
    } else {
        /*
         * no hardware time stamps available,
         * so keep the shared tx_flags and only
         * store software time stamp
         */
        skb->tstamp = ktime_get_real();
    }

    serr = SKB_EXT_ERR(skb);
    memset(serr, 0, sizeof(*serr));
    serr->ee.ee_errno = ENOMSG;
    serr->ee.ee_origin = SO_EE_ORIGIN_TIMESTAMPING;

    err = sock_queue_err_skb(sk, skb);

    if (err)
        kfree_skb(skb);
}
EXPORT_SYMBOL_GPL(skb_tstamp_tx);

void skb_complete_wifi_ack(struct sk_buff *skb, bool acked)
{
    struct sock *sk = skb->sk;
    struct sock_exterr_skb *serr;
    int err;

    skb->wifi_acked_valid = 1;
    skb->wifi_acked = acked;

    serr = SKB_EXT_ERR(skb);
    memset(serr, 0, sizeof(*serr));
    serr->ee.ee_errno = ENOMSG;
    serr->ee.ee_origin = SO_EE_ORIGIN_TXSTATUS;

    err = sock_queue_err_skb(sk, skb);
    if (err)
        kfree_skb(skb);
}
EXPORT_SYMBOL_GPL(skb_complete_wifi_ack);


bool skb_partial_csum_set(struct sk_buff *skb, u16 start, u16 off)
{
    if (unlikely(start > skb_headlen(skb)) ||
        unlikely((int)start + off > skb_headlen(skb) - 2)) {
        net_warn_ratelimited("bad partial csum: csum=%u/%u len=%u\n",
                     start, off, skb_headlen(skb));
        return false;
    }
    skb->ip_summed = CHECKSUM_PARTIAL;
    skb->csum_start = skb_headroom(skb) + start;
    skb->csum_offset = off;
    return true;
}
EXPORT_SYMBOL_GPL(skb_partial_csum_set);

void __skb_warn_lro_forwarding(const struct sk_buff *skb)
{
    net_warn_ratelimited("%s: received packets cannot be forwarded while LRO is enabled\n",
                 skb->dev->name);
}
EXPORT_SYMBOL(__skb_warn_lro_forwarding);

void kfree_skb_partial(struct sk_buff *skb, bool head_stolen)
{
    if (head_stolen) {
        skb_release_head_state(skb);
        kmem_cache_free(skbuff_head_cache, skb);
    } else {
        __kfree_skb(skb);
    }
}
EXPORT_SYMBOL(kfree_skb_partial);

bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from,
              bool *fragstolen, int *delta_truesize)
{
    int i, delta, len = from->len;

    *fragstolen = false;

    if (skb_cloned(to))
        return false;

    if (len <= skb_tailroom(to)) {
        BUG_ON(skb_copy_bits(from, 0, skb_put(to, len), len));
        *delta_truesize = 0;
        return true;
    }

    if (skb_has_frag_list(to) || skb_has_frag_list(from))
        return false;

    if (skb_headlen(from) != 0) {
        struct page *page;
        unsigned int offset;

        if (skb_shinfo(to)->nr_frags +
            skb_shinfo(from)->nr_frags >= MAX_SKB_FRAGS)
            return false;

        if (skb_head_is_locked(from))
            return false;

        delta = from->truesize - SKB_DATA_ALIGN(sizeof(struct sk_buff));

        page = virt_to_head_page(from->head);
        offset = from->data - (unsigned char *)page_address(page);

        skb_fill_page_desc(to, skb_shinfo(to)->nr_frags,
                   page, offset, skb_headlen(from));
        *fragstolen = true;
    } else {
        if (skb_shinfo(to)->nr_frags +
            skb_shinfo(from)->nr_frags > MAX_SKB_FRAGS)
            return false;

        delta = from->truesize - SKB_TRUESIZE(skb_end_offset(from));
    }

    WARN_ON_ONCE(delta < len);

    memcpy(skb_shinfo(to)->frags + skb_shinfo(to)->nr_frags,
           skb_shinfo(from)->frags,
           skb_shinfo(from)->nr_frags * sizeof(skb_frag_t));
    skb_shinfo(to)->nr_frags += skb_shinfo(from)->nr_frags;

    if (!skb_cloned(from))
        skb_shinfo(from)->nr_frags = 0;

    /* if the skb is not cloned this does nothing
     * since we set nr_frags to 0.
     */
    for (i = 0; i < skb_shinfo(from)->nr_frags; i++)
        skb_frag_ref(from, i);

    to->truesize += delta;
    to->len += len;
    to->data_len += len;

    *delta_truesize = delta;
    return true;
}
EXPORT_SYMBOL(skb_try_coalesce);