Skip to content
Snippets Groups Projects
Select Git revision
  • 3f66116e89521ef71ab0d63dc07a639def88a577
  • add-vdpu381-and-383-to-rkvdec
  • prepare-add-vdpu381-and-383-to-rkvdec
  • add-rkvdec2-driver-vdpu383-hevc
  • add-rkvdec2-driver-vdpu383
  • add-rkvdec2-driver-hevc
  • rkvdec-mov-to-structs
  • av1-fix-postproc-leak
  • add-rkvdec2-driver-iommu-422-10bits
  • patch-queue/jamba/trixie
  • hdmi-fix-1080p-rock4d-6.11
  • upstreaming/rk3576-rock4d-spi-v1
  • upstreaming/rk3576-rock4d-support-v5
  • upstreaming/rk3588-hdmi-audio-6
  • upstreaming/rk3576-rock4d-support-v3
  • upstreaming/rk3576-rock4d-support-v1
  • upstreaming/rk3576-rock4d-support
  • add-rkvdec2-driver-iommu
  • upstream/rk3576-rock-4d
  • rk3588-hdmi-audio-2
  • fix-rk3588-i2s-tdm-clocks
  • v6.3
  • v6.3-rc1
  • v6.2-rc1
  • v6.0-rc1
  • v5.19-rc3
  • v5.19-rc2
  • v5.19-rc1
  • v5.18
  • v5.18-rc7
  • v5.18-rc6
  • v5.18-rc5
  • v5.18-rc4
  • v5.18-rc3
  • v5.18-rc2
  • v5.18-rc1
  • v5.17
  • v5.17-rc8
  • v5.17-rc7
  • v5.17-rc6
  • v5.17-rc5
41 results

af_unix.c

Blame
  • Forked from hardware-enablement / Rockchip upstream enablement efforts / linux
    Source project has a limited visibility.
    skbuff.c 108.06 KiB
    /*
     *	Routines having to do with the 'struct sk_buff' memory handlers.
     *
     *	Authors:	Alan Cox <alan@lxorguk.ukuu.org.uk>
     *			Florian La Roche <rzsfl@rz.uni-sb.de>
     *
     *	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/tcp.h>
    #include <linux/udp.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 <linux/if_vlan.h>
    
    #include <net/protocol.h>
    #include <net/dst.h>
    #include <net/sock.h>
    #include <net/checksum.h>
    #include <net/ip6_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;
    
    /**
     *	skb_panic - private function for out-of-line support
     *	@skb:	buffer
     *	@sz:	size
     *	@addr:	address
     *	@msg:	skb_over_panic or skb_under_panic
     *
     *	Out-of-line support for skb_put() and skb_push().
     *	Called via the wrapper skb_over_panic() or skb_under_panic().
     *	Keep out of line to prevent kernel bloat.
     *	__builtin_return_address is not used because it is not always reliable.
     */
    static void skb_panic(struct sk_buff *skb, unsigned int sz, void *addr,
    		      const char msg[])
    {
    	pr_emerg("%s: text:%p len:%d put:%d head:%p data:%p tail:%#lx end:%#lx dev:%s\n",
    		 msg, addr, 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_over_panic(struct sk_buff *skb, unsigned int sz, void *addr)
    {
    	skb_panic(skb, sz, addr, __func__);
    }
    
    static void skb_under_panic(struct sk_buff *skb, unsigned int sz, void *addr)
    {
    	skb_panic(skb, sz, addr, __func__);
    }
    
    /*
     * 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)
    
    static 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_head(gfp_t gfp_mask, int node)
    {
    	struct sk_buff *skb;
    
    	/* Get the HEAD */
    	skb = kmem_cache_alloc_node(skbuff_head_cache,
    				    gfp_mask & ~__GFP_DMA, node);
    	if (!skb)
    		goto out;
    
    	/*
    	 * 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));
    	skb->head = NULL;
    	skb->truesize = sizeof(struct sk_buff);
    	atomic_set(&skb->users, 1);
    
    	skb->mac_header = (typeof(skb->mac_header))~0U;
    out:
    	return skb;
    }
    
    /**
     *	__alloc_skb	-	allocate a network buffer
     *	@size: size to allocate
     *	@gfp_mask: allocation mask
     *	@flags: If SKB_ALLOC_FCLONE is set, allocate from fclone cache
     *		instead of head cache and allocate a cloned (child) skb.
     *		If SKB_ALLOC_RX is set, __GFP_MEMALLOC will be used for
     *		allocations in case the data is required for writeback
     *	@node: numa node to allocate memory on
     *
     *	Allocate a new &sk_buff. The returned buffer has no headroom and a
     *	tail room of at least size bytes. The object has a reference count
     *	of one. The return is the buffer. On a failure the return is %NULL.
     *
     *	Buffers may only be allocated from interrupts using a @gfp_mask of
     *	%GFP_ATOMIC.
     */
    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;
    	skb->mac_header = (typeof(skb->mac_header))~0U;
    	skb->transport_header = (typeof(skb->transport_header))~0U;
    
    	/* 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_fclones *fclones;
    
    		fclones = container_of(skb, struct sk_buff_fclones, skb1);
    
    		kmemcheck_annotate_bitfield(&fclones->skb2, flags1);
    		skb->fclone = SKB_FCLONE_ORIG;
    		atomic_set(&fclones->fclone_ref, 1);
    
    		fclones->skb2.fclone = SKB_FCLONE_CLONE;
    		fclones->skb2.pfmemalloc = pfmemalloc;
    	}
    out:
    	return skb;
    nodata:
    	kmem_cache_free(cache, skb);
    	skb = NULL;
    	goto out;
    }
    EXPORT_SYMBOL(__alloc_skb);
    
    /**
     * build_skb - build a network buffer
     * @data: data buffer provided by caller
     * @frag_size: size of fragment, or 0 if head was kmalloced
     *
     * Allocate a new &sk_buff. Caller provides space holding head and
     * skb_shared_info. @data must have been allocated by kmalloc() only if
     * @frag_size is 0, otherwise data should come from the page allocator.
     * The return is the new skb buffer.
     * On a failure the return is %NULL, and @data is not freed.
     * Notes :
     *  Before IO, driver allocates only data buffer where NIC put incoming frame
     *  Driver should add room at head (NET_SKB_PAD) and
     *  MUST add room at tail (SKB_DATA_ALIGN(skb_shared_info))
     *  After IO, driver calls build_skb(), to allocate sk_buff and populate it
     *  before giving packet to stack.
     *  RX rings only contains data buffers, not full skbs.
     */
    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;
    	skb->mac_header = (typeof(skb->mac_header))~0U;
    	skb->transport_header = (typeof(skb->transport_header))~0U;
    
    	/* 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);
    static DEFINE_PER_CPU(struct netdev_alloc_cache, napi_alloc_cache);
    
    static struct page *__page_frag_refill(struct netdev_alloc_cache *nc,
    				       gfp_t gfp_mask)
    {
    	const unsigned int order = NETDEV_FRAG_PAGE_MAX_ORDER;
    	struct page *page = NULL;
    	gfp_t gfp = gfp_mask;
    
    	if (order) {
    		gfp_mask |= __GFP_COMP | __GFP_NOWARN | __GFP_NORETRY;
    		page = alloc_pages_node(NUMA_NO_NODE, gfp_mask, order);
    		nc->frag.size = PAGE_SIZE << (page ? order : 0);
    	}
    
    	if (unlikely(!page))
    		page = alloc_pages_node(NUMA_NO_NODE, gfp, 0);
    
    	nc->frag.page = page;
    
    	return page;
    }
    
    static void *__alloc_page_frag(struct netdev_alloc_cache __percpu *cache,
    			       unsigned int fragsz, gfp_t gfp_mask)
    {
    	struct netdev_alloc_cache *nc = this_cpu_ptr(cache);
    	struct page *page = nc->frag.page;
    	unsigned int size;
    	int offset;
    
    	if (unlikely(!page)) {
    refill:
    		page = __page_frag_refill(nc, gfp_mask);
    		if (!page)
    			return NULL;
    
    		/* if size can vary use frag.size else just use PAGE_SIZE */
    		size = NETDEV_FRAG_PAGE_MAX_ORDER ? nc->frag.size : PAGE_SIZE;
    
    		/* Even if we own the page, we do not use atomic_set().
    		 * This would break get_page_unless_zero() users.
    		 */
    		atomic_add(size - 1, &page->_count);
    
    		/* reset page count bias and offset to start of new frag */
    		nc->pagecnt_bias = size;
    		nc->frag.offset = size;
    	}
    
    	offset = nc->frag.offset - fragsz;
    	if (unlikely(offset < 0)) {
    		if (!atomic_sub_and_test(nc->pagecnt_bias, &page->_count))
    			goto refill;
    
    		/* if size can vary use frag.size else just use PAGE_SIZE */
    		size = NETDEV_FRAG_PAGE_MAX_ORDER ? nc->frag.size : PAGE_SIZE;
    
    		/* OK, page count is 0, we can safely set it */
    		atomic_set(&page->_count, size);
    
    		/* reset page count bias and offset to start of new frag */
    		nc->pagecnt_bias = size;
    		offset = size - fragsz;
    	}
    
    	nc->pagecnt_bias--;
    	nc->frag.offset = offset;
    
    	return page_address(page) + offset;
    }
    
    static void *__netdev_alloc_frag(unsigned int fragsz, gfp_t gfp_mask)
    {
    	unsigned long flags;
    	void *data;
    
    	local_irq_save(flags);
    	data = __alloc_page_frag(&netdev_alloc_cache, fragsz, gfp_mask);
    	local_irq_restore(flags);
    	return data;
    }
    
    /**
     * netdev_alloc_frag - allocate a page fragment
     * @fragsz: fragment size
     *
     * Allocates a frag from a page for receive buffer.
     * Uses GFP_ATOMIC allocations.
     */
    void *netdev_alloc_frag(unsigned int fragsz)
    {
    	return __netdev_alloc_frag(fragsz, GFP_ATOMIC | __GFP_COLD);
    }
    EXPORT_SYMBOL(netdev_alloc_frag);
    
    static void *__napi_alloc_frag(unsigned int fragsz, gfp_t gfp_mask)
    {
    	return __alloc_page_frag(&napi_alloc_cache, fragsz, gfp_mask);
    }
    
    void *napi_alloc_frag(unsigned int fragsz)
    {
    	return __napi_alloc_frag(fragsz, GFP_ATOMIC | __GFP_COLD);
    }
    EXPORT_SYMBOL(napi_alloc_frag);
    
    /**
     *	__netdev_alloc_skb - allocate an skbuff for rx on a specific device
     *	@dev: network device to receive on
     *	@length: length to allocate
     *	@gfp_mask: get_free_pages mask, passed to alloc_skb
     *
     *	Allocate a new &sk_buff and assign it a usage count of one. The
     *	buffer has unspecified headroom built in. Users should allocate
     *	the headroom they think they need without accounting for the
     *	built in space. The built in space is used for optimisations.
     *
     *	%NULL is returned if there is no free memory.
     */
    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);
    
    void skb_coalesce_rx_frag(struct sk_buff *skb, int i, int size,
    			  unsigned int truesize)
    {
    	skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
    
    	skb_frag_size_add(frag, size);
    	skb->len += size;
    	skb->data_len += size;
    	skb->truesize += truesize;
    }
    EXPORT_SYMBOL(skb_coalesce_rx_frag);
    
    static void skb_drop_list(struct sk_buff **listp)
    {
    	kfree_skb_list(*listp);
    	*listp = NULL;
    }
    
    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)
    {
    	struct skb_shared_info *shinfo = skb_shinfo(skb);
    	int i;
    
    	if (skb->cloned &&
    	    atomic_sub_return(skb->nohdr ? (1 << SKB_DATAREF_SHIFT) + 1 : 1,
    			      &shinfo->dataref))
    		return;
    
    	for (i = 0; i < shinfo->nr_frags; i++)
    		__skb_frag_unref(&shinfo->frags[i]);
    
    	/*
    	 * If skb buf is from userspace, we need to notify the caller
    	 * the lower device DMA has done;
    	 */
    	if (shinfo->tx_flags & SKBTX_DEV_ZEROCOPY) {
    		struct ubuf_info *uarg;
    
    		uarg = shinfo->destructor_arg;
    		if (uarg->callback)
    			uarg->callback(uarg, true);
    	}
    
    	if (shinfo->frag_list)
    		kfree_skb_list(shinfo->frag_list);
    
    	skb_free_head(skb);
    }
    
    /*
     *	Free an skbuff by memory without cleaning the state.
     */
    static void kfree_skbmem(struct sk_buff *skb)
    {
    	struct sk_buff_fclones *fclones;
    
    	switch (skb->fclone) {
    	case SKB_FCLONE_UNAVAILABLE:
    		kmem_cache_free(skbuff_head_cache, skb);
    		return;
    
    	case SKB_FCLONE_ORIG:
    		fclones = container_of(skb, struct sk_buff_fclones, skb1);
    
    		/* We usually free the clone (TX completion) before original skb
    		 * This test would have no chance to be true for the clone,
    		 * while here, branch prediction will be good.
    		 */
    		if (atomic_read(&fclones->fclone_ref) == 1)
    			goto fastpath;
    		break;
    
    	default: /* SKB_FCLONE_CLONE */
    		fclones = container_of(skb, struct sk_buff_fclones, skb2);
    		break;
    	}
    	if (!atomic_dec_and_test(&fclones->fclone_ref))
    		return;
    fastpath:
    	kmem_cache_free(skbuff_fclone_cache, fclones);
    }
    
    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
    #if IS_ENABLED(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);
    	if (likely(skb->head))
    		skb_release_data(skb);
    }
    
    /**
     *	__kfree_skb - private function
     *	@skb: buffer
     *
     *	Free an sk_buff. Release anything attached to the buffer.
     *	Clean the state. This is an internal helper function. Users should
     *	always call kfree_skb
     */
    
    void __kfree_skb(struct sk_buff *skb)
    {
    	skb_release_all(skb);
    	kfree_skbmem(skb);
    }
    EXPORT_SYMBOL(__kfree_skb);
    
    /**
     *	kfree_skb - free an sk_buff
     *	@skb: buffer to free
     *
     *	Drop a reference to the buffer and free it if the usage count has
     *	hit zero.
     */
    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 kfree_skb_list(struct sk_buff *segs)
    {
    	while (segs) {
    		struct sk_buff *next = segs->next;
    
    		kfree_skb(segs);
    		segs = next;
    	}
    }
    EXPORT_SYMBOL(kfree_skb_list);
    
    /**
     *	skb_tx_error - report an sk_buff xmit error
     *	@skb: buffer that triggered an error
     *
     *	Report xmit error if a device callback is tracking this skb.
     *	skb must be freed afterwards.
     */
    void skb_tx_error(struct sk_buff *skb)
    {
    	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, false);
    		skb_shinfo(skb)->tx_flags &= ~SKBTX_DEV_ZEROCOPY;
    	}
    }
    EXPORT_SYMBOL(skb_tx_error);
    
    /**
     *	consume_skb - free an skbuff
     *	@skb: buffer to free
     *
     *	Drop a ref to the buffer and free it if the usage count has hit zero
     *	Functions identically to kfree_skb, but kfree_skb assumes that the frame
     *	is being dropped after a failure and notes that
     */
    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);
    
    /* Make sure a field is enclosed inside headers_start/headers_end section */
    #define CHECK_SKB_FIELD(field) \
    	BUILD_BUG_ON(offsetof(struct sk_buff, field) <		\
    		     offsetof(struct sk_buff, headers_start));	\
    	BUILD_BUG_ON(offsetof(struct sk_buff, field) >		\
    		     offsetof(struct sk_buff, headers_end));	\
    
    static void __copy_skb_header(struct sk_buff *new, const struct sk_buff *old)
    {
    	new->tstamp		= old->tstamp;
    	/* We do not copy old->sk */
    	new->dev		= old->dev;
    	memcpy(new->cb, old->cb, sizeof(old->cb));
    	skb_dst_copy(new, old);
    #ifdef CONFIG_XFRM
    	new->sp			= secpath_get(old->sp);
    #endif
    	__nf_copy(new, old, false);
    
    	/* Note : this field could be in headers_start/headers_end section
    	 * It is not yet because we do not want to have a 16 bit hole
    	 */
    	new->queue_mapping = old->queue_mapping;
    
    	memcpy(&new->headers_start, &old->headers_start,
    	       offsetof(struct sk_buff, headers_end) -
    	       offsetof(struct sk_buff, headers_start));
    	CHECK_SKB_FIELD(protocol);
    	CHECK_SKB_FIELD(csum);
    	CHECK_SKB_FIELD(hash);
    	CHECK_SKB_FIELD(priority);
    	CHECK_SKB_FIELD(skb_iif);
    	CHECK_SKB_FIELD(vlan_proto);
    	CHECK_SKB_FIELD(vlan_tci);
    	CHECK_SKB_FIELD(transport_header);
    	CHECK_SKB_FIELD(network_header);
    	CHECK_SKB_FIELD(mac_header);
    	CHECK_SKB_FIELD(inner_protocol);
    	CHECK_SKB_FIELD(inner_transport_header);
    	CHECK_SKB_FIELD(inner_network_header);
    	CHECK_SKB_FIELD(inner_mac_header);
    	CHECK_SKB_FIELD(mark);
    #ifdef CONFIG_NETWORK_SECMARK
    	CHECK_SKB_FIELD(secmark);
    #endif
    #ifdef CONFIG_NET_RX_BUSY_POLL
    	CHECK_SKB_FIELD(napi_id);
    #endif
    #ifdef CONFIG_NET_SCHED
    	CHECK_SKB_FIELD(tc_index);
    #ifdef CONFIG_NET_CLS_ACT
    	CHECK_SKB_FIELD(tc_verd);
    #endif
    #endif
    
    }
    
    /*
     * 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
    }
    
    /**
     *	skb_morph	-	morph one skb into another
     *	@dst: the skb to receive the contents
     *	@src: the skb to supply the contents
     *
     *	This is identical to skb_clone except that the target skb is
     *	supplied by the user.
     *
     *	The target skb is returned upon exit.
     */
    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);
    
    /**
     *	skb_copy_ubufs	-	copy userspace skb frags buffers to kernel
     *	@skb: the skb to modify
     *	@gfp_mask: allocation priority
     *
     *	This must be called on SKBTX_DEV_ZEROCOPY skb.
     *	It will copy all frags into kernel and drop the reference
     *	to userspace pages.
     *
     *	If this function is called from an interrupt gfp_mask() must be
     *	%GFP_ATOMIC.
     *
     *	Returns 0 on success or a negative error code on failure
     *	to allocate kernel memory to copy to.
     */
    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 *)page_private(head);
    				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);
    		set_page_private(page, (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, false);
    
    	/* 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 *)page_private(head);
    	}
    
    	skb_shinfo(skb)->tx_flags &= ~SKBTX_DEV_ZEROCOPY;
    	return 0;
    }
    EXPORT_SYMBOL_GPL(skb_copy_ubufs);
    
    /**
     *	skb_clone	-	duplicate an sk_buff
     *	@skb: buffer to clone
     *	@gfp_mask: allocation priority
     *
     *	Duplicate an &sk_buff. The new one is not owned by a socket. Both
     *	copies share the same packet data but not structure. The new
     *	buffer has a reference count of 1. If the allocation fails the
     *	function returns %NULL otherwise the new buffer is returned.
     *
     *	If this function is called from an interrupt gfp_mask() must be
     *	%GFP_ATOMIC.
     */
    
    struct sk_buff *skb_clone(struct sk_buff *skb, gfp_t gfp_mask)
    {
    	struct sk_buff_fclones *fclones = container_of(skb,
    						       struct sk_buff_fclones,
    						       skb1);
    	struct sk_buff *n;
    
    	if (skb_orphan_frags(skb, gfp_mask))
    		return NULL;
    
    	if (skb->fclone == SKB_FCLONE_ORIG &&
    	    atomic_read(&fclones->fclone_ref) == 1) {
    		n = &fclones->skb2;
    		atomic_set(&fclones->fclone_ref, 2);
    	} 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);
    		n->fclone = SKB_FCLONE_UNAVAILABLE;
    	}
    
    	return __skb_clone(n, skb);
    }
    EXPORT_SYMBOL(skb_clone);
    
    static void skb_headers_offset_update(struct sk_buff *skb, int off)
    {
    	/* Only adjust this if it actually is csum_start rather than csum */
    	if (skb->ip_summed == CHECKSUM_PARTIAL)
    		skb->csum_start += off;
    	/* {transport,network,mac}_header and tail are relative to skb->head */
    	skb->transport_header += off;
    	skb->network_header   += off;
    	if (skb_mac_header_was_set(skb))
    		skb->mac_header += off;
    	skb->inner_transport_header += off;
    	skb->inner_network_header += off;
    	skb->inner_mac_header += off;
    }
    
    static void copy_skb_header(struct sk_buff *new, const struct sk_buff *old)
    {
    	__copy_skb_header(new, old);
    
    	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;
    }
    
    /**
     *	skb_copy	-	create private copy of an sk_buff
     *	@skb: buffer to copy
     *	@gfp_mask: allocation priority
     *
     *	Make a copy of both an &sk_buff and its data. This is used when the
     *	caller wishes to modify the data and needs a private copy of the
     *	data to alter. Returns %NULL on failure or the pointer to the buffer
     *	on success. The returned buffer has a reference count of 1.
     *
     *	As by-product this function converts non-linear &sk_buff to linear
     *	one, so that &sk_buff becomes completely private and caller is allowed
     *	to modify all the data of returned buffer. This means that this
     *	function is not recommended for use in circumstances when only
     *	header is going to be modified. Use pskb_copy() instead.
     */
    
    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);
    
    /**
     *	__pskb_copy_fclone	-  create copy of an sk_buff with private head.
     *	@skb: buffer to copy
     *	@headroom: headroom of new skb
     *	@gfp_mask: allocation priority
     *	@fclone: if true allocate the copy of the skb from the fclone
     *	cache instead of the head cache; it is recommended to set this
     *	to true for the cases where the copy will likely be cloned
     *
     *	Make a copy of both an &sk_buff and part of its data, located
     *	in header. Fragmented data remain shared. This is used when
     *	the caller wishes to modify only header of &sk_buff and needs
     *	private copy of the header to alter. Returns %NULL on failure
     *	or the pointer to the buffer on success.
     *	The returned buffer has a reference count of 1.
     */
    
    struct sk_buff *__pskb_copy_fclone(struct sk_buff *skb, int headroom,
    				   gfp_t gfp_mask, bool fclone)
    {
    	unsigned int size = skb_headlen(skb) + headroom;
    	int flags = skb_alloc_rx_flag(skb) | (fclone ? SKB_ALLOC_FCLONE : 0);
    	struct sk_buff *n = __alloc_skb(size, gfp_mask, flags, 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_fclone);
    
    /**
     *	pskb_expand_head - reallocate header of &sk_buff
     *	@skb: buffer to reallocate
     *	@nhead: room to add at head
     *	@ntail: room to add at tail
     *	@gfp_mask: allocation priority
     *
     *	Expands (or creates identical copy, if @nhead and @ntail are zero)
     *	header of @skb. &sk_buff itself is not changed. &sk_buff MUST have
     *	reference count of 1. Returns zero in the case of success or error,
     *	if expansion failed. In the last case, &sk_buff is not changed.
     *
     *	All the pointers pointing into skb header may change and must be
     *	reloaded after call to this function.
     */
    
    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
    	skb->tail	      += off;
    	skb_headers_offset_update(skb, 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);
    
    /**
     *	skb_copy_expand	-	copy and expand sk_buff
     *	@skb: buffer to copy
     *	@newheadroom: new free bytes at head
     *	@newtailroom: new free bytes at tail
     *	@gfp_mask: allocation priority
     *
     *	Make a copy of both an &sk_buff and its data and while doing so
     *	allocate additional space.
     *
     *	This is used when the caller wishes to modify the data and needs a
     *	private copy of the data to alter as well as more space for new fields.
     *	Returns %NULL on failure or the pointer to the buffer
     *	on success. The returned buffer has a reference count of 1.
     *
     *	You must pass %GFP_ATOMIC as the allocation priority if this function
     *	is called from an interrupt.
     */
    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;
    
    	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);
    
    	skb_headers_offset_update(n, newheadroom - oldheadroom);
    
    	return n;
    }
    EXPORT_SYMBOL(skb_copy_expand);
    
    /**
     *	skb_pad			-	zero pad the tail of an skb
     *	@skb: buffer to pad
     *	@pad: space to pad
     *
     *	Ensure that a buffer is followed by a padding area that is zero
     *	filled. Used by network drivers which may DMA or transfer data
     *	beyond the buffer end onto the wire.
     *
     *	May return error in out of memory cases. The skb is freed on error.
     */
    
    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);
    
    /**
     *	pskb_put - add data to the tail of a potentially fragmented buffer
     *	@skb: start of the buffer to use
     *	@tail: tail fragment of the buffer to use
     *	@len: amount of data to add
     *
     *	This function extends the used data area of the potentially
     *	fragmented buffer. @tail must be the last fragment of @skb -- or
     *	@skb itself. If this would exceed the total buffer size the kernel
     *	will panic. A pointer to the first byte of the extra data is
     *	returned.
     */
    
    unsigned char *pskb_put(struct sk_buff *skb, struct sk_buff *tail, int len)
    {
    	if (tail != skb) {
    		skb->data_len += len;
    		skb->len += len;
    	}
    	return skb_put(tail, len);
    }
    EXPORT_SYMBOL_GPL(pskb_put);
    
    /**
     *	skb_put - add data to a buffer
     *	@skb: buffer to use
     *	@len: amount of data to add
     *
     *	This function extends the used data area of the buffer. If this would
     *	exceed the total buffer size the kernel will panic. A pointer to the
     *	first byte of the extra data is returned.
     */
    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);
    
    /**
     *	skb_push - add data to the start of a buffer
     *	@skb: buffer to use
     *	@len: amount of data to add
     *
     *	This function extends the used data area of the buffer at the buffer
     *	start. If this would exceed the total buffer headroom the kernel will
     *	panic. A pointer to the first byte of the extra data is returned.
     */
    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);
    
    /**
     *	skb_pull - remove data from the start of a buffer
     *	@skb: buffer to use
     *	@len: amount of data to remove
     *
     *	This function removes data from the start of a buffer, returning
     *	the memory to the headroom. A pointer to the next data in the buffer
     *	is returned. Once the data has been pulled future pushes will overwrite
     *	the old data.
     */
    unsigned char *skb_pull(struct sk_buff *skb, unsigned int len)
    {
    	return skb_pull_inline(skb, len);
    }
    EXPORT_SYMBOL(skb_pull);
    
    /**
     *	skb_trim - remove end from a buffer
     *	@skb: buffer to alter
     *	@len: new length
     *
     *	Cut the length of a buffer down by removing data from the tail. If
     *	the buffer is already under the length specified it is not modified.
     *	The skb must be linear.
     */
    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);
    
    /**
     *	__pskb_pull_tail - advance tail of skb header
     *	@skb: buffer to reallocate
     *	@delta: number of bytes to advance tail
     *
     *	The function makes a sense only on a fragmented &sk_buff,
     *	it expands header moving its tail forward and copying necessary
     *	data from fragmented part.
     *
     *	&sk_buff MUST have reference count of 1.
     *
     *	Returns %NULL (and &sk_buff does not change) if pull failed
     *	or value of new tail of skb in the case of success.
     *
     *	All the pointers pointing into skb header may change and must be
     *	reloaded after call to this function.
     */
    
    /* 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);
    
    /**
     *	skb_copy_bits - copy bits from skb to kernel buffer
     *	@skb: source skb
     *	@offset: offset in source
     *	@to: destination buffer
     *	@len: number of bytes to copy
     *
     *	Copy the specified number of bytes from the source skb to the
     *	destination buffer.
     *
     *	CAUTION ! :
     *		If its prototype is ever changed,
     *		check arch/{*}/net/{*}.S files,
     *		since it is called from BPF assembly code.
     */
    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 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,
    			  bool linear,
    			  struct sock *sk)
    {
    	if (unlikely(spd->nr_pages == MAX_SKB_FRAGS))
    		return true;
    
    	if (linear) {
    		page = linear_to_page(page, len, &offset, 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 bool __splice_segment(struct page *page, unsigned int poff,
    			     unsigned int plen, unsigned int *off,
    			     unsigned int *len,
    			     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 */
    	poff += *off;
    	plen -= *off;
    	*off = 0;
    
    	do {
    		unsigned int flen = min(*len, plen);
    
    		if (spd_fill_page(spd, pipe, page, &flen, poff,
    				  linear, sk))
    			return true;
    		poff += flen;
    		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, 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, 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 = &nosteal_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;
    }
    
    /**
     *	skb_store_bits - store bits from kernel buffer to skb
     *	@skb: destination buffer
     *	@offset: offset in destination
     *	@from: source buffer
     *	@len: number of bytes to copy
     *
     *	Copy the specified number of bytes from the source buffer to the
     *	destination skb.  This function handles all the messy bits of
     *	traversing fragment lists and such.
     */
    
    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, const struct skb_checksum_ops *ops)
    {
    	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 = ops->update(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 = ops->update(vaddr + frag->page_offset +
    					    offset - start, copy, 0);
    			kunmap_atomic(vaddr);
    			csum = ops->combine(csum, csum2, pos, copy);
    			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, ops);
    			csum = ops->combine(csum, csum2, pos, copy);
    			if ((len -= copy) == 0)
    				return csum;
    			offset += copy;
    			pos    += copy;
    		}
    		start = end;
    	}
    	BUG_ON(len);
    
    	return csum;
    }
    EXPORT_SYMBOL(__skb_checksum);
    
    __wsum skb_checksum(const struct sk_buff *skb, int offset,
    		    int len, __wsum csum)
    {
    	const struct skb_checksum_ops ops = {
    		.update  = csum_partial_ext,
    		.combine = csum_block_add_ext,
    	};
    
    	return __skb_checksum(skb, offset, len, csum, &ops);
    }
    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);
    
     /**
     *	skb_zerocopy_headlen - Calculate headroom needed for skb_zerocopy()
     *	@from: source buffer
     *
     *	Calculates the amount of linear headroom needed in the 'to' skb passed
     *	into skb_zerocopy().
     */
    unsigned int
    skb_zerocopy_headlen(const struct sk_buff *from)
    {
    	unsigned int hlen = 0;
    
    	if (!from->head_frag ||
    	    skb_headlen(from) < L1_CACHE_BYTES ||
    	    skb_shinfo(from)->nr_frags >= MAX_SKB_FRAGS)
    		hlen = skb_headlen(from);
    
    	if (skb_has_frag_list(from))
    		hlen = from->len;
    
    	return hlen;
    }
    EXPORT_SYMBOL_GPL(skb_zerocopy_headlen);
    
    /**
     *	skb_zerocopy - Zero copy skb to skb
     *	@to: destination buffer
     *	@from: source buffer
     *	@len: number of bytes to copy from source buffer
     *	@hlen: size of linear headroom in destination buffer
     *
     *	Copies up to `len` bytes from `from` to `to` by creating references
     *	to the frags in the source buffer.
     *
     *	The `hlen` as calculated by skb_zerocopy_headlen() specifies the
     *	headroom in the `to` buffer.
     *
     *	Return value:
     *	0: everything is OK
     *	-ENOMEM: couldn't orphan frags of @from due to lack of memory
     *	-EFAULT: skb_copy_bits() found some problem with skb geometry
     */
    int
    skb_zerocopy(struct sk_buff *to, struct sk_buff *from, int len, int hlen)
    {
    	int i, j = 0;
    	int plen = 0; /* length of skb->head fragment */
    	int ret;
    	struct page *page;
    	unsigned int offset;
    
    	BUG_ON(!from->head_frag && !hlen);
    
    	/* dont bother with small payloads */
    	if (len <= skb_tailroom(to))
    		return skb_copy_bits(from, 0, skb_put(to, len), len);
    
    	if (hlen) {
    		ret = skb_copy_bits(from, 0, skb_put(to, hlen), hlen);
    		if (unlikely(ret))
    			return ret;
    		len -= hlen;
    	} else {
    		plen = min_t(int, skb_headlen(from), len);
    		if (plen) {
    			page = virt_to_head_page(from->head);
    			offset = from->data - (unsigned char *)page_address(page);
    			__skb_fill_page_desc(to, 0, page, offset, plen);
    			get_page(page);
    			j = 1;
    			len -= plen;
    		}
    	}
    
    	to->truesize += len + plen;
    	to->len += len + plen;
    	to->data_len += len + plen;
    
    	if (unlikely(skb_orphan_frags(from, GFP_ATOMIC))) {
    		skb_tx_error(from);
    		return -ENOMEM;
    	}
    
    	for (i = 0; i < skb_shinfo(from)->nr_frags; i++) {
    		if (!len)
    			break;
    		skb_shinfo(to)->frags[j] = skb_shinfo(from)->frags[i];
    		skb_shinfo(to)->frags[j].size = min_t(int, skb_shinfo(to)->frags[j].size, len);
    		len -= skb_shinfo(to)->frags[j].size;
    		skb_frag_ref(to, j);
    		j++;
    	}
    	skb_shinfo(to)->nr_frags = j;
    
    	return 0;
    }
    EXPORT_SYMBOL_GPL(skb_zerocopy);
    
    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);
    
    /**
     *	skb_dequeue - remove from the head of the queue
     *	@list: list to dequeue from
     *
     *	Remove the head of the list. The list lock is taken so the function
     *	may be used safely with other locking list functions. The head item is
     *	returned or %NULL if the list is empty.
     */
    
    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);
    
    /**
     *	skb_dequeue_tail - remove from the tail of the queue
     *	@list: list to dequeue from
     *
     *	Remove the tail of the list. The list lock is taken so the function
     *	may be used safely with other locking list functions. The tail item is
     *	returned or %NULL if the list is empty.
     */
    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);
    
    /**
     *	skb_queue_purge - empty a list
     *	@list: list to empty
     *
     *	Delete all buffers on an &sk_buff list. Each buffer is removed from
     *	the list and one reference dropped. This function takes the list
     *	lock and is atomic with respect to other list locking functions.
     */
    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);
    
    /**
     *	skb_queue_head - queue a buffer at the list head
     *	@list: list to use
     *	@newsk: buffer to queue
     *
     *	Queue a buffer at the start of the list. This function takes the
     *	list lock and can be used safely with other locking &sk_buff functions
     *	safely.
     *
     *	A buffer cannot be placed on two lists at the same time.
     */
    void skb_queue_head(struct sk_buff_head *list, struct sk_buff *newsk)
    {
    	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);
    
    /**
     *	skb_queue_tail - queue a buffer at the list tail
     *	@list: list to use
     *	@newsk: buffer to queue
     *
     *	Queue a buffer at the tail of the list. This function takes the
     *	list lock and can be used safely with other locking &sk_buff functions
     *	safely.
     *
     *	A buffer cannot be placed on two lists at the same time.
     */
    void skb_queue_tail(struct sk_buff_head *list, struct sk_buff *newsk)
    {
    	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);
    
    /**
     *	skb_unlink	-	remove a buffer from a list
     *	@skb: buffer to remove
     *	@list: list to use
     *
     *	Remove a packet from a list. The list locks are taken and this
     *	function is atomic with respect to other list locked calls
     *
     *	You must know what list the SKB is on.
     */
    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);
    
    /**
     *	skb_append	-	append a buffer
     *	@old: buffer to insert after
     *	@newsk: buffer to insert
     *	@list: list to use
     *
     *	Place a packet after a given packet in a list. The list locks are taken
     *	and this function is atomic with respect to other list locked calls.
     *	A buffer cannot be placed on two lists at the same time.
     */
    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);
    
    /**
     *	skb_insert	-	insert a buffer
     *	@old: buffer to insert before
     *	@newsk: buffer to insert
     *	@list: list to use
     *
     *	Place a packet before a given packet in a list. The list locks are
     * 	taken and this function is atomic with respect to other list locked
     *	calls.
     *
     *	A buffer cannot be placed on two lists at the same time.
     */
    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;
    }
    
    /**
     * skb_split - Split fragmented skb to two parts at length len.
     * @skb: the buffer to split
     * @skb1: the buffer to receive the second part
     * @len: new length for skb
     */
    void skb_split(struct sk_buff *skb, struct sk_buff *skb1, const u32 len)
    {
    	int pos = skb_headlen(skb);
    
    	skb_shinfo(skb1)->tx_flags = skb_shinfo(skb)->tx_flags & SKBTX_SHARED_FRAG;
    	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);
    }
    
    /**
     * skb_shift - Shifts paged data partially from skb to another
     * @tgt: buffer into which tail data gets added
     * @skb: buffer from which the paged data comes from
     * @shiftlen: shift up to this many bytes
     *
     * Attempts to shift up to shiftlen worth of bytes, which may be less than
     * the length of the skb, from skb to tgt. Returns number bytes shifted.
     * It's up to caller to free skb if everything was shifted.
     *
     * If @tgt runs out of frags, the whole operation is aborted.
     *
     * Skb cannot include anything else but paged data while tgt is allowed
     * to have non-paged data as well.
     *
     * TODO: full sized shift could be optimized but that would need
     * specialized skb free'er to handle frags without up-to-date nr_frags.
     */
    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;
    }
    
    /**
     * skb_prepare_seq_read - Prepare a sequential read of skb data
     * @skb: the buffer to read
     * @from: lower offset of data to be read
     * @to: upper offset of data to be read
     * @st: state variable
     *
     * Initializes the specified state variable. Must be called before
     * invoking skb_seq_read() for the first time.
     */
    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);
    
    /**
     * skb_seq_read - Sequentially read skb data
     * @consumed: number of bytes consumed by the caller so far
     * @data: destination pointer for data to be returned
     * @st: state variable
     *
     * Reads a block of skb data at @consumed relative to the
     * lower offset specified to skb_prepare_seq_read(). Assigns
     * the head of the data block to @data and returns the length
     * of the block or 0 if the end of the skb data or the upper
     * offset has been reached.
     *
     * The caller is not required to consume all of the data
     * returned, i.e. @consumed is typically set to the number
     * of bytes already consumed and the next call to
     * skb_seq_read() will return the remaining part of the block.
     *
     * Note 1: The size of each block of data returned can be arbitrary,
     *       this limitation is the cost for zerocopy sequential
     *       reads of potentially non linear data.
     *
     * Note 2: Fragment lists within fragments are not implemented
     *       at the moment, state->root_skb could be replaced with
     *       a stack for this purpose.
     */
    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)) {
    		if (st->frag_data) {
    			kunmap_atomic(st->frag_data);
    			st->frag_data = NULL;
    		}
    		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);
    
    /**
     * skb_abort_seq_read - Abort a sequential read of skb data
     * @st: state variable
     *
     * Must be called if skb_seq_read() was not called until it
     * returned 0.
     */
    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));
    }
    
    /**
     * skb_find_text - Find a text pattern in skb data
     * @skb: the buffer to look in
     * @from: search offset
     * @to: search limit
     * @config: textsearch configuration
     * @state: uninitialized textsearch state variable
     *
     * Finds a pattern in the skb data according to the specified
     * textsearch configuration. Use textsearch_next() to retrieve
     * subsequent occurrences of the pattern. Returns the offset
     * to the first occurrence or UINT_MAX if no match was found.
     */
    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);
    
    /**
     * skb_append_datato_frags - append the user data to a skb
     * @sk: sock  structure
     * @skb: skb structure to be appended with user data.
     * @getfrag: call back function to be used for getting the user data
     * @from: pointer to user message iov
     * @length: length of the iov message
     *
     * Description: This procedure append the user data in the fragment part
     * of the skb if any page alloc fails user this procedure returns  -ENOMEM
     */
    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 = skb_shinfo(skb)->nr_frags;
    	int copy;
    	int offset = 0;
    	int ret;
    	struct page_frag *pfrag = &current->task_frag;
    
    	do {
    		/* Return error if we don't have space for new frag */
    		if (frg_cnt >= MAX_SKB_FRAGS)
    			return -EMSGSIZE;
    
    		if (!sk_page_frag_refill(sk, pfrag))
    			return -ENOMEM;
    
    		/* copy the user data to page */
    		copy = min_t(int, length, pfrag->size - pfrag->offset);
    
    		ret = getfrag(from, page_address(pfrag->page) + pfrag->offset,
    			      offset, copy, 0, skb);
    		if (ret < 0)
    			return -EFAULT;
    
    		/* copy was successful so update the size parameters */
    		skb_fill_page_desc(skb, frg_cnt, pfrag->page, pfrag->offset,
    				   copy);
    		frg_cnt++;
    		pfrag->offset += copy;
    		get_page(pfrag->page);
    
    		skb->truesize += copy;
    		atomic_add(copy, &sk->sk_wmem_alloc);
    		skb->len += copy;
    		skb->data_len += copy;
    		offset += copy;
    		length -= copy;
    
    	} while (length > 0);
    
    	return 0;
    }
    EXPORT_SYMBOL(skb_append_datato_frags);
    
    /**
     *	skb_pull_rcsum - pull skb and update receive checksum
     *	@skb: buffer to update
     *	@len: length of data pulled
     *
     *	This function performs an skb_pull on the packet and updates
     *	the CHECKSUM_COMPLETE checksum.  It should be used on
     *	receive path processing instead of skb_pull unless you know
     *	that the checksum difference is zero (e.g., a valid IP header)
     *	or you are setting ip_summed to CHECKSUM_NONE.
     */
    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);
    
    /**
     *	skb_segment - Perform protocol segmentation on skb.
     *	@head_skb: buffer to segment
     *	@features: features for the output path (see dev->features)
     *
     *	This function performs segmentation on the given skb.  It returns
     *	a pointer to the first in a list of new skbs for the segments.
     *	In case of error it returns ERR_PTR(err).
     */
    struct sk_buff *skb_segment(struct sk_buff *head_skb,
    			    netdev_features_t features)
    {
    	struct sk_buff *segs = NULL;
    	struct sk_buff *tail = NULL;
    	struct sk_buff *list_skb = skb_shinfo(head_skb)->frag_list;
    	skb_frag_t *frag = skb_shinfo(head_skb)->frags;
    	unsigned int mss = skb_shinfo(head_skb)->gso_size;
    	unsigned int doffset = head_skb->data - skb_mac_header(head_skb);
    	struct sk_buff *frag_skb = head_skb;
    	unsigned int offset = doffset;
    	unsigned int tnl_hlen = skb_tnl_header_len(head_skb);
    	unsigned int headroom;
    	unsigned int len;
    	__be16 proto;
    	bool csum;
    	int sg = !!(features & NETIF_F_SG);
    	int nfrags = skb_shinfo(head_skb)->nr_frags;
    	int err = -ENOMEM;
    	int i = 0;
    	int pos;
    	int dummy;
    
    	__skb_push(head_skb, doffset);
    	proto = skb_network_protocol(head_skb, &dummy);
    	if (unlikely(!proto))
    		return ERR_PTR(-EINVAL);
    
    	csum = !head_skb->encap_hdr_csum &&
    	    !!can_checksum_protocol(features, proto);
    
    	headroom = skb_headroom(head_skb);
    	pos = skb_headlen(head_skb);
    
    	do {
    		struct sk_buff *nskb;
    		skb_frag_t *nskb_frag;
    		int hsize;
    		int size;
    
    		len = head_skb->len - offset;
    		if (len > mss)
    			len = mss;
    
    		hsize = skb_headlen(head_skb) - offset;
    		if (hsize < 0)
    			hsize = 0;
    		if (hsize > len || !sg)
    			hsize = len;
    
    		if (!hsize && i >= nfrags && skb_headlen(list_skb) &&
    		    (skb_headlen(list_skb) == len || sg)) {
    			BUG_ON(skb_headlen(list_skb) > len);
    
    			i = 0;
    			nfrags = skb_shinfo(list_skb)->nr_frags;
    			frag = skb_shinfo(list_skb)->frags;
    			frag_skb = list_skb;
    			pos += skb_headlen(list_skb);
    
    			while (pos < offset + len) {
    				BUG_ON(i >= nfrags);
    
    				size = skb_frag_size(frag);
    				if (pos + size > offset + len)
    					break;
    
    				i++;
    				pos += size;
    				frag++;
    			}
    
    			nskb = skb_clone(list_skb, GFP_ATOMIC);
    			list_skb = list_skb->next;
    
    			if (unlikely(!nskb))
    				goto err;
    
    			if (unlikely(pskb_trim(nskb, len))) {
    				kfree_skb(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(head_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, head_skb);
    
    		skb_headers_offset_update(nskb, skb_headroom(nskb) - headroom);
    		skb_reset_mac_len(nskb);
    
    		skb_copy_from_linear_data_offset(head_skb, -tnl_hlen,
    						 nskb->data - tnl_hlen,
    						 doffset + tnl_hlen);
    
    		if (nskb->len == len + doffset)
    			goto perform_csum_check;
    
    		if (!sg && !nskb->remcsum_offload) {
    			nskb->ip_summed = CHECKSUM_NONE;
    			nskb->csum = skb_copy_and_csum_bits(head_skb, offset,
    							    skb_put(nskb, len),
    							    len, 0);
    			SKB_GSO_CB(nskb)->csum_start =
    			    skb_headroom(nskb) + doffset;
    			continue;
    		}
    
    		nskb_frag = skb_shinfo(nskb)->frags;
    
    		skb_copy_from_linear_data_offset(head_skb, offset,
    						 skb_put(nskb, hsize), hsize);
    
    		skb_shinfo(nskb)->tx_flags = skb_shinfo(head_skb)->tx_flags &
    			SKBTX_SHARED_FRAG;
    
    		while (pos < offset + len) {
    			if (i >= nfrags) {
    				BUG_ON(skb_headlen(list_skb));
    
    				i = 0;
    				nfrags = skb_shinfo(list_skb)->nr_frags;
    				frag = skb_shinfo(list_skb)->frags;
    				frag_skb = list_skb;
    
    				BUG_ON(!nfrags);
    
    				list_skb = list_skb->next;
    			}
    
    			if (unlikely(skb_shinfo(nskb)->nr_frags >=
    				     MAX_SKB_FRAGS)) {
    				net_warn_ratelimited(
    					"skb_segment: too many frags: %u %u\n",
    					pos, mss);
    				goto err;
    			}
    
    			if (unlikely(skb_orphan_frags(frag_skb, GFP_ATOMIC)))
    				goto err;
    
    			*nskb_frag = *frag;
    			__skb_frag_ref(nskb_frag);
    			size = skb_frag_size(nskb_frag);
    
    			if (pos < offset) {
    				nskb_frag->page_offset += offset - pos;
    				skb_frag_size_sub(nskb_frag, offset - pos);
    			}
    
    			skb_shinfo(nskb)->nr_frags++;
    
    			if (pos + size <= offset + len) {
    				i++;
    				frag++;
    				pos += size;
    			} else {
    				skb_frag_size_sub(nskb_frag, pos + size - (offset + len));
    				goto skip_fraglist;
    			}
    
    			nskb_frag++;
    		}
    
    skip_fraglist:
    		nskb->data_len = len - hsize;
    		nskb->len += nskb->data_len;
    		nskb->truesize += nskb->data_len;
    
    perform_csum_check:
    		if (!csum && !nskb->remcsum_offload) {
    			nskb->csum = skb_checksum(nskb, doffset,
    						  nskb->len - doffset, 0);
    			nskb->ip_summed = CHECKSUM_NONE;
    			SKB_GSO_CB(nskb)->csum_start =
    			    skb_headroom(nskb) + doffset;
    		}
    	} while ((offset += len) < head_skb->len);
    
    	/* Some callers want to get the end of the list.
    	 * Put it in segs->prev to avoid walking the list.
    	 * (see validate_xmit_skb_list() for example)
    	 */
    	segs->prev = tail;
    
    	/* Following permits correct backpressure, for protocols
    	 * using skb_set_owner_w().
    	 * Idea is to tranfert ownership from head_skb to last segment.
    	 */
    	if (head_skb->destructor == sock_wfree) {
    		swap(tail->truesize, head_skb->truesize);
    		swap(tail->destructor, head_skb->destructor);
    		swap(tail->sk, head_skb->sk);
    	}
    	return segs;
    
    err:
    	kfree_skb_list(segs);
    	return ERR_PTR(err);
    }
    EXPORT_SYMBOL_GPL(skb_segment);
    
    int skb_gro_receive(struct sk_buff **head, struct sk_buff *skb)
    {
    	struct skb_shared_info *pinfo, *skbinfo = skb_shinfo(skb);
    	unsigned int offset = skb_gro_offset(skb);
    	unsigned int headlen = skb_headlen(skb);
    	struct sk_buff *nskb, *lp, *p = *head;
    	unsigned int len = skb_gro_len(skb);
    	unsigned int delta_truesize;
    	unsigned int headroom;
    
    	if (unlikely(p->len + len >= 65536))
    		return -E2BIG;
    
    	lp = NAPI_GRO_CB(p)->last;
    	pinfo = skb_shinfo(lp);
    
    	if (headlen <= offset) {
    		skb_frag_t *frag;
    		skb_frag_t *frag2;
    		int i = skbinfo->nr_frags;
    		int nr_frags = pinfo->nr_frags + i;
    
    		if (nr_frags > MAX_SKB_FRAGS)
    			goto merge;
    
    		offset -= headlen;
    		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)
    			goto merge;
    
    		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;
    	}
    	/* switch back to head shinfo */
    	pinfo = skb_shinfo(p);
    
    	if (pinfo->frag_list)
    		goto merge;
    	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));
    
    	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);
    
    	if (NAPI_GRO_CB(p)->last == p)
    		skb_shinfo(p)->frag_list = skb;
    	else
    		NAPI_GRO_CB(p)->last->next = skb;
    	NAPI_GRO_CB(p)->last = skb;
    	__skb_header_release(skb);
    	lp = p;
    
    done:
    	NAPI_GRO_CB(p)->count++;
    	p->data_len += len;
    	p->truesize += delta_truesize;
    	p->len += len;
    	if (lp != p) {
    		lp->data_len += len;
    		lp->truesize += delta_truesize;
    		lp->len += len;
    	}
    	NAPI_GRO_CB(skb)->same_flow = 1;
    	return 0;
    }
    
    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",
    						sizeof(struct sk_buff_fclones),
    						0,
    						SLAB_HWCACHE_ALIGN|SLAB_PANIC,
    						NULL);
    }
    
    /**
     *	skb_to_sgvec - Fill a scatter-gather list from a socket buffer
     *	@skb: Socket buffer containing the buffers to be mapped
     *	@sg: The scatter-gather list to map into
     *	@offset: The offset into the buffer's contents to start mapping
     *	@len: Length of buffer space to be mapped
     *
     *	Fill the specified scatter-gather list with mappings/pointers into a
     *	region of the buffer space attached to a socket buffer.
     */
    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;
    }
    
    /* As compared with skb_to_sgvec, skb_to_sgvec_nomark only map skb to given
     * sglist without mark the sg which contain last skb data as the end.
     * So the caller can mannipulate sg list as will when padding new data after
     * the first call without calling sg_unmark_end to expend sg list.
     *
     * Scenario to use skb_to_sgvec_nomark:
     * 1. sg_init_table
     * 2. skb_to_sgvec_nomark(payload1)
     * 3. skb_to_sgvec_nomark(payload2)
     *
     * This is equivalent to:
     * 1. sg_init_table
     * 2. skb_to_sgvec(payload1)
     * 3. sg_unmark_end
     * 4. skb_to_sgvec(payload2)
     *
     * When mapping mutilple payload conditionally, skb_to_sgvec_nomark
     * is more preferable.
     */
    int skb_to_sgvec_nomark(struct sk_buff *skb, struct scatterlist *sg,
    			int offset, int len)
    {
    	return __skb_to_sgvec(skb, sg, offset, len);
    }
    EXPORT_SYMBOL_GPL(skb_to_sgvec_nomark);
    
    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);
    
    /**
     *	skb_cow_data - Check that a socket buffer's data buffers are writable
     *	@skb: The socket buffer to check.
     *	@tailbits: Amount of trailing space to be added
     *	@trailer: Returned pointer to the skb where the @tailbits space begins
     *
     *	Make sure that the data buffers attached to a socket buffer are
     *	writable. If they are not, private copies are made of the data buffers
     *	and the socket buffer is set to use these instead.
     *
     *	If @tailbits is given, make sure that there is space to write @tailbits
     *	bytes of data beyond current end of socket buffer.  @trailer will be
     *	set to point to the skb in which this space begins.
     *
     *	The number of scatterlist elements required to completely map the
     *	COW'd and extended socket buffer will be returned.
     */
    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)
    {
    	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);
    	return 0;
    }
    EXPORT_SYMBOL(sock_queue_err_skb);
    
    struct sk_buff *sock_dequeue_err_skb(struct sock *sk)
    {
    	struct sk_buff_head *q = &sk->sk_error_queue;
    	struct sk_buff *skb, *skb_next;
    	int err = 0;
    
    	spin_lock_bh(&q->lock);
    	skb = __skb_dequeue(q);
    	if (skb && (skb_next = skb_peek(q)))
    		err = SKB_EXT_ERR(skb_next)->ee.ee_errno;
    	spin_unlock_bh(&q->lock);
    
    	sk->sk_err = err;
    	if (err)
    		sk->sk_error_report(sk);
    
    	return skb;
    }
    EXPORT_SYMBOL(sock_dequeue_err_skb);
    
    /**
     * skb_clone_sk - create clone of skb, and take reference to socket
     * @skb: the skb to clone
     *
     * This function creates a clone of a buffer that holds a reference on
     * sk_refcnt.  Buffers created via this function are meant to be
     * returned using sock_queue_err_skb, or free via kfree_skb.
     *
     * When passing buffers allocated with this function to sock_queue_err_skb
     * it is necessary to wrap the call with sock_hold/sock_put in order to
     * prevent the socket from being released prior to being enqueued on
     * the sk_error_queue.
     */
    struct sk_buff *skb_clone_sk(struct sk_buff *skb)
    {
    	struct sock *sk = skb->sk;
    	struct sk_buff *clone;
    
    	if (!sk || !atomic_inc_not_zero(&sk->sk_refcnt))
    		return NULL;
    
    	clone = skb_clone(skb, GFP_ATOMIC);
    	if (!clone) {
    		sock_put(sk);
    		return NULL;
    	}
    
    	clone->sk = sk;
    	clone->destructor = sock_efree;
    
    	return clone;
    }
    EXPORT_SYMBOL(skb_clone_sk);
    
    static void __skb_complete_tx_timestamp(struct sk_buff *skb,
    					struct sock *sk,
    					int tstype)
    {
    	struct sock_exterr_skb *serr;
    	int err;
    
    	serr = SKB_EXT_ERR(skb);
    	memset(serr, 0, sizeof(*serr));
    	serr->ee.ee_errno = ENOMSG;
    	serr->ee.ee_origin = SO_EE_ORIGIN_TIMESTAMPING;
    	serr->ee.ee_info = tstype;
    	if (sk->sk_tsflags & SOF_TIMESTAMPING_OPT_ID) {
    		serr->ee.ee_data = skb_shinfo(skb)->tskey;
    		if (sk->sk_protocol == IPPROTO_TCP)
    			serr->ee.ee_data -= sk->sk_tskey;
    	}
    
    	err = sock_queue_err_skb(sk, skb);
    
    	if (err)
    		kfree_skb(skb);
    }
    
    void skb_complete_tx_timestamp(struct sk_buff *skb,
    			       struct skb_shared_hwtstamps *hwtstamps)
    {
    	struct sock *sk = skb->sk;
    
    	/* take a reference to prevent skb_orphan() from freeing the socket */
    	sock_hold(sk);
    
    	*skb_hwtstamps(skb) = *hwtstamps;
    	__skb_complete_tx_timestamp(skb, sk, SCM_TSTAMP_SND);
    
    	sock_put(sk);
    }
    EXPORT_SYMBOL_GPL(skb_complete_tx_timestamp);
    
    void __skb_tstamp_tx(struct sk_buff *orig_skb,
    		     struct skb_shared_hwtstamps *hwtstamps,
    		     struct sock *sk, int tstype)
    {
    	struct sk_buff *skb;
    
    	if (!sk)
    		return;
    
    	if (hwtstamps)
    		*skb_hwtstamps(orig_skb) = *hwtstamps;
    	else
    		orig_skb->tstamp = ktime_get_real();
    
    	skb = skb_clone(orig_skb, GFP_ATOMIC);
    	if (!skb)
    		return;
    
    	__skb_complete_tx_timestamp(skb, sk, tstype);
    }
    EXPORT_SYMBOL_GPL(__skb_tstamp_tx);
    
    void skb_tstamp_tx(struct sk_buff *orig_skb,
    		   struct skb_shared_hwtstamps *hwtstamps)
    {
    	return __skb_tstamp_tx(orig_skb, hwtstamps, orig_skb->sk,
    			       SCM_TSTAMP_SND);
    }
    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;
    
    	/* take a reference to prevent skb_orphan() from freeing the socket */
    	sock_hold(sk);
    
    	err = sock_queue_err_skb(sk, skb);
    	if (err)
    		kfree_skb(skb);
    
    	sock_put(sk);
    }
    EXPORT_SYMBOL_GPL(skb_complete_wifi_ack);
    
    
    /**
     * skb_partial_csum_set - set up and verify partial csum values for packet
     * @skb: the skb to set
     * @start: the number of bytes after skb->data to start checksumming.
     * @off: the offset from start to place the checksum.
     *
     * For untrusted partially-checksummed packets, we need to make sure the values
     * for skb->csum_start and skb->csum_offset are valid so we don't oops.
     *
     * This function checks and sets those values and skb->ip_summed: if this
     * returns false you should drop the packet.
     */
    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;
    	skb_set_transport_header(skb, start);
    	return true;
    }
    EXPORT_SYMBOL_GPL(skb_partial_csum_set);
    
    static int skb_maybe_pull_tail(struct sk_buff *skb, unsigned int len,
    			       unsigned int max)
    {
    	if (skb_headlen(skb) >= len)
    		return 0;
    
    	/* If we need to pullup then pullup to the max, so we
    	 * won't need to do it again.
    	 */
    	if (max > skb->len)
    		max = skb->len;
    
    	if (__pskb_pull_tail(skb, max - skb_headlen(skb)) == NULL)
    		return -ENOMEM;
    
    	if (skb_headlen(skb) < len)
    		return -EPROTO;
    
    	return 0;
    }
    
    #define MAX_TCP_HDR_LEN (15 * 4)
    
    static __sum16 *skb_checksum_setup_ip(struct sk_buff *skb,
    				      typeof(IPPROTO_IP) proto,
    				      unsigned int off)
    {
    	switch (proto) {
    		int err;
    
    	case IPPROTO_TCP:
    		err = skb_maybe_pull_tail(skb, off + sizeof(struct tcphdr),
    					  off + MAX_TCP_HDR_LEN);
    		if (!err && !skb_partial_csum_set(skb, off,
    						  offsetof(struct tcphdr,
    							   check)))
    			err = -EPROTO;
    		return err ? ERR_PTR(err) : &tcp_hdr(skb)->check;
    
    	case IPPROTO_UDP:
    		err = skb_maybe_pull_tail(skb, off + sizeof(struct udphdr),
    					  off + sizeof(struct udphdr));
    		if (!err && !skb_partial_csum_set(skb, off,
    						  offsetof(struct udphdr,
    							   check)))
    			err = -EPROTO;
    		return err ? ERR_PTR(err) : &udp_hdr(skb)->check;
    	}
    
    	return ERR_PTR(-EPROTO);
    }
    
    /* This value should be large enough to cover a tagged ethernet header plus
     * maximally sized IP and TCP or UDP headers.
     */
    #define MAX_IP_HDR_LEN 128
    
    static int skb_checksum_setup_ipv4(struct sk_buff *skb, bool recalculate)
    {
    	unsigned int off;
    	bool fragment;
    	__sum16 *csum;
    	int err;
    
    	fragment = false;
    
    	err = skb_maybe_pull_tail(skb,
    				  sizeof(struct iphdr),
    				  MAX_IP_HDR_LEN);
    	if (err < 0)
    		goto out;
    
    	if (ip_hdr(skb)->frag_off & htons(IP_OFFSET | IP_MF))
    		fragment = true;
    
    	off = ip_hdrlen(skb);
    
    	err = -EPROTO;
    
    	if (fragment)
    		goto out;
    
    	csum = skb_checksum_setup_ip(skb, ip_hdr(skb)->protocol, off);
    	if (IS_ERR(csum))
    		return PTR_ERR(csum);
    
    	if (recalculate)
    		*csum = ~csum_tcpudp_magic(ip_hdr(skb)->saddr,
    					   ip_hdr(skb)->daddr,
    					   skb->len - off,
    					   ip_hdr(skb)->protocol, 0);
    	err = 0;
    
    out:
    	return err;
    }
    
    /* This value should be large enough to cover a tagged ethernet header plus
     * an IPv6 header, all options, and a maximal TCP or UDP header.
     */
    #define MAX_IPV6_HDR_LEN 256
    
    #define OPT_HDR(type, skb, off) \
    	(type *)(skb_network_header(skb) + (off))
    
    static int skb_checksum_setup_ipv6(struct sk_buff *skb, bool recalculate)
    {
    	int err;
    	u8 nexthdr;
    	unsigned int off;
    	unsigned int len;
    	bool fragment;
    	bool done;
    	__sum16 *csum;
    
    	fragment = false;
    	done = false;
    
    	off = sizeof(struct ipv6hdr);
    
    	err = skb_maybe_pull_tail(skb, off, MAX_IPV6_HDR_LEN);
    	if (err < 0)
    		goto out;
    
    	nexthdr = ipv6_hdr(skb)->nexthdr;
    
    	len = sizeof(struct ipv6hdr) + ntohs(ipv6_hdr(skb)->payload_len);
    	while (off <= len && !done) {
    		switch (nexthdr) {
    		case IPPROTO_DSTOPTS:
    		case IPPROTO_HOPOPTS:
    		case IPPROTO_ROUTING: {
    			struct ipv6_opt_hdr *hp;
    
    			err = skb_maybe_pull_tail(skb,
    						  off +
    						  sizeof(struct ipv6_opt_hdr),
    						  MAX_IPV6_HDR_LEN);
    			if (err < 0)
    				goto out;
    
    			hp = OPT_HDR(struct ipv6_opt_hdr, skb, off);
    			nexthdr = hp->nexthdr;
    			off += ipv6_optlen(hp);
    			break;
    		}
    		case IPPROTO_AH: {
    			struct ip_auth_hdr *hp;
    
    			err = skb_maybe_pull_tail(skb,
    						  off +
    						  sizeof(struct ip_auth_hdr),
    						  MAX_IPV6_HDR_LEN);
    			if (err < 0)
    				goto out;
    
    			hp = OPT_HDR(struct ip_auth_hdr, skb, off);
    			nexthdr = hp->nexthdr;
    			off += ipv6_authlen(hp);
    			break;
    		}
    		case IPPROTO_FRAGMENT: {
    			struct frag_hdr *hp;
    
    			err = skb_maybe_pull_tail(skb,
    						  off +
    						  sizeof(struct frag_hdr),
    						  MAX_IPV6_HDR_LEN);
    			if (err < 0)
    				goto out;
    
    			hp = OPT_HDR(struct frag_hdr, skb, off);
    
    			if (hp->frag_off & htons(IP6_OFFSET | IP6_MF))
    				fragment = true;
    
    			nexthdr = hp->nexthdr;
    			off += sizeof(struct frag_hdr);
    			break;
    		}
    		default:
    			done = true;
    			break;
    		}
    	}
    
    	err = -EPROTO;
    
    	if (!done || fragment)
    		goto out;
    
    	csum = skb_checksum_setup_ip(skb, nexthdr, off);
    	if (IS_ERR(csum))
    		return PTR_ERR(csum);
    
    	if (recalculate)
    		*csum = ~csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
    					 &ipv6_hdr(skb)->daddr,
    					 skb->len - off, nexthdr, 0);
    	err = 0;
    
    out:
    	return err;
    }
    
    /**
     * skb_checksum_setup - set up partial checksum offset
     * @skb: the skb to set up
     * @recalculate: if true the pseudo-header checksum will be recalculated
     */
    int skb_checksum_setup(struct sk_buff *skb, bool recalculate)
    {
    	int err;
    
    	switch (skb->protocol) {
    	case htons(ETH_P_IP):
    		err = skb_checksum_setup_ipv4(skb, recalculate);
    		break;
    
    	case htons(ETH_P_IPV6):
    		err = skb_checksum_setup_ipv6(skb, recalculate);
    		break;
    
    	default:
    		err = -EPROTO;
    		break;
    	}
    
    	return err;
    }
    EXPORT_SYMBOL(skb_checksum_setup);
    
    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);
    
    /**
     * skb_try_coalesce - try to merge skb to prior one
     * @to: prior buffer
     * @from: buffer to add
     * @fragstolen: pointer to boolean
     * @delta_truesize: how much more was allocated than was requested
     */
    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)) {
    		if (len)
    			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);
    
    /**
     * skb_scrub_packet - scrub an skb
     *
     * @skb: buffer to clean
     * @xnet: packet is crossing netns
     *
     * skb_scrub_packet can be used after encapsulating or decapsulting a packet
     * into/from a tunnel. Some information have to be cleared during these
     * operations.
     * skb_scrub_packet can also be used to clean a skb before injecting it in
     * another namespace (@xnet == true). We have to clear all information in the
     * skb that could impact namespace isolation.
     */
    void skb_scrub_packet(struct sk_buff *skb, bool xnet)
    {
    	if (xnet)
    		skb_orphan(skb);
    	skb->tstamp.tv64 = 0;
    	skb->pkt_type = PACKET_HOST;
    	skb->skb_iif = 0;
    	skb->ignore_df = 0;
    	skb_dst_drop(skb);
    	skb->mark = 0;
    	secpath_reset(skb);
    	nf_reset(skb);
    	nf_reset_trace(skb);
    }
    EXPORT_SYMBOL_GPL(skb_scrub_packet);
    
    /**
     * skb_gso_transport_seglen - Return length of individual segments of a gso packet
     *
     * @skb: GSO skb
     *
     * skb_gso_transport_seglen is used to determine the real size of the
     * individual segments, including Layer4 headers (TCP/UDP).
     *
     * The MAC/L2 or network (IP, IPv6) headers are not accounted for.
     */
    unsigned int skb_gso_transport_seglen(const struct sk_buff *skb)
    {
    	const struct skb_shared_info *shinfo = skb_shinfo(skb);
    	unsigned int thlen = 0;
    
    	if (skb->encapsulation) {
    		thlen = skb_inner_transport_header(skb) -
    			skb_transport_header(skb);
    
    		if (likely(shinfo->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6)))
    			thlen += inner_tcp_hdrlen(skb);
    	} else if (likely(shinfo->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6))) {
    		thlen = tcp_hdrlen(skb);
    	}
    	/* UFO sets gso_size to the size of the fragmentation
    	 * payload, i.e. the size of the L4 (UDP) header is already
    	 * accounted for.
    	 */
    	return thlen + shinfo->gso_size;
    }
    EXPORT_SYMBOL_GPL(skb_gso_transport_seglen);
    
    static struct sk_buff *skb_reorder_vlan_header(struct sk_buff *skb)
    {
    	if (skb_cow(skb, skb_headroom(skb)) < 0) {
    		kfree_skb(skb);
    		return NULL;
    	}
    
    	memmove(skb->data - ETH_HLEN, skb->data - VLAN_ETH_HLEN, 2 * ETH_ALEN);
    	skb->mac_header += VLAN_HLEN;
    	return skb;
    }
    
    struct sk_buff *skb_vlan_untag(struct sk_buff *skb)
    {
    	struct vlan_hdr *vhdr;
    	u16 vlan_tci;
    
    	if (unlikely(vlan_tx_tag_present(skb))) {
    		/* vlan_tci is already set-up so leave this for another time */
    		return skb;
    	}
    
    	skb = skb_share_check(skb, GFP_ATOMIC);
    	if (unlikely(!skb))
    		goto err_free;
    
    	if (unlikely(!pskb_may_pull(skb, VLAN_HLEN)))
    		goto err_free;
    
    	vhdr = (struct vlan_hdr *)skb->data;
    	vlan_tci = ntohs(vhdr->h_vlan_TCI);
    	__vlan_hwaccel_put_tag(skb, skb->protocol, vlan_tci);
    
    	skb_pull_rcsum(skb, VLAN_HLEN);
    	vlan_set_encap_proto(skb, vhdr);
    
    	skb = skb_reorder_vlan_header(skb);
    	if (unlikely(!skb))
    		goto err_free;
    
    	skb_reset_network_header(skb);
    	skb_reset_transport_header(skb);
    	skb_reset_mac_len(skb);
    
    	return skb;
    
    err_free:
    	kfree_skb(skb);
    	return NULL;
    }
    EXPORT_SYMBOL(skb_vlan_untag);
    
    int skb_ensure_writable(struct sk_buff *skb, int write_len)
    {
    	if (!pskb_may_pull(skb, write_len))
    		return -ENOMEM;
    
    	if (!skb_cloned(skb) || skb_clone_writable(skb, write_len))
    		return 0;
    
    	return pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
    }
    EXPORT_SYMBOL(skb_ensure_writable);
    
    /* remove VLAN header from packet and update csum accordingly. */
    static int __skb_vlan_pop(struct sk_buff *skb, u16 *vlan_tci)
    {
    	struct vlan_hdr *vhdr;
    	unsigned int offset = skb->data - skb_mac_header(skb);
    	int err;
    
    	__skb_push(skb, offset);
    	err = skb_ensure_writable(skb, VLAN_ETH_HLEN);
    	if (unlikely(err))
    		goto pull;
    
    	skb_postpull_rcsum(skb, skb->data + (2 * ETH_ALEN), VLAN_HLEN);
    
    	vhdr = (struct vlan_hdr *)(skb->data + ETH_HLEN);
    	*vlan_tci = ntohs(vhdr->h_vlan_TCI);
    
    	memmove(skb->data + VLAN_HLEN, skb->data, 2 * ETH_ALEN);
    	__skb_pull(skb, VLAN_HLEN);
    
    	vlan_set_encap_proto(skb, vhdr);
    	skb->mac_header += VLAN_HLEN;
    
    	if (skb_network_offset(skb) < ETH_HLEN)
    		skb_set_network_header(skb, ETH_HLEN);
    
    	skb_reset_mac_len(skb);
    pull:
    	__skb_pull(skb, offset);
    
    	return err;
    }
    
    int skb_vlan_pop(struct sk_buff *skb)
    {
    	u16 vlan_tci;
    	__be16 vlan_proto;
    	int err;
    
    	if (likely(vlan_tx_tag_present(skb))) {
    		skb->vlan_tci = 0;
    	} else {
    		if (unlikely((skb->protocol != htons(ETH_P_8021Q) &&
    			      skb->protocol != htons(ETH_P_8021AD)) ||
    			     skb->len < VLAN_ETH_HLEN))
    			return 0;
    
    		err = __skb_vlan_pop(skb, &vlan_tci);
    		if (err)
    			return err;
    	}
    	/* move next vlan tag to hw accel tag */
    	if (likely((skb->protocol != htons(ETH_P_8021Q) &&
    		    skb->protocol != htons(ETH_P_8021AD)) ||
    		   skb->len < VLAN_ETH_HLEN))
    		return 0;
    
    	vlan_proto = skb->protocol;
    	err = __skb_vlan_pop(skb, &vlan_tci);
    	if (unlikely(err))
    		return err;
    
    	__vlan_hwaccel_put_tag(skb, vlan_proto, vlan_tci);
    	return 0;
    }
    EXPORT_SYMBOL(skb_vlan_pop);
    
    int skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci)
    {
    	if (vlan_tx_tag_present(skb)) {
    		unsigned int offset = skb->data - skb_mac_header(skb);
    		int err;
    
    		/* __vlan_insert_tag expect skb->data pointing to mac header.
    		 * So change skb->data before calling it and change back to
    		 * original position later
    		 */
    		__skb_push(skb, offset);
    		err = __vlan_insert_tag(skb, skb->vlan_proto,
    					vlan_tx_tag_get(skb));
    		if (err)
    			return err;
    		skb->protocol = skb->vlan_proto;
    		skb->mac_len += VLAN_HLEN;
    		__skb_pull(skb, offset);
    
    		if (skb->ip_summed == CHECKSUM_COMPLETE)
    			skb->csum = csum_add(skb->csum, csum_partial(skb->data
    					+ (2 * ETH_ALEN), VLAN_HLEN, 0));
    	}
    	__vlan_hwaccel_put_tag(skb, vlan_proto, vlan_tci);
    	return 0;
    }
    EXPORT_SYMBOL(skb_vlan_push);
    
    /**
     * alloc_skb_with_frags - allocate skb with page frags
     *
     * @header_len: size of linear part
     * @data_len: needed length in frags
     * @max_page_order: max page order desired.
     * @errcode: pointer to error code if any
     * @gfp_mask: allocation mask
     *
     * This can be used to allocate a paged skb, given a maximal order for frags.
     */
    struct sk_buff *alloc_skb_with_frags(unsigned long header_len,
    				     unsigned long data_len,
    				     int max_page_order,
    				     int *errcode,
    				     gfp_t gfp_mask)
    {
    	int npages = (data_len + (PAGE_SIZE - 1)) >> PAGE_SHIFT;
    	unsigned long chunk;
    	struct sk_buff *skb;
    	struct page *page;
    	gfp_t gfp_head;
    	int i;
    
    	*errcode = -EMSGSIZE;
    	/* Note this test could be relaxed, if we succeed to allocate
    	 * high order pages...
    	 */
    	if (npages > MAX_SKB_FRAGS)
    		return NULL;
    
    	gfp_head = gfp_mask;
    	if (gfp_head & __GFP_WAIT)
    		gfp_head |= __GFP_REPEAT;
    
    	*errcode = -ENOBUFS;
    	skb = alloc_skb(header_len, gfp_head);
    	if (!skb)
    		return NULL;
    
    	skb->truesize += npages << PAGE_SHIFT;
    
    	for (i = 0; npages > 0; i++) {
    		int order = max_page_order;
    
    		while (order) {
    			if (npages >= 1 << order) {
    				page = alloc_pages(gfp_mask |
    						   __GFP_COMP |
    						   __GFP_NOWARN |
    						   __GFP_NORETRY,
    						   order);
    				if (page)
    					goto fill_page;
    				/* Do not retry other high order allocations */
    				order = 1;
    				max_page_order = 0;
    			}
    			order--;
    		}
    		page = alloc_page(gfp_mask);
    		if (!page)
    			goto failure;
    fill_page:
    		chunk = min_t(unsigned long, data_len,
    			      PAGE_SIZE << order);
    		skb_fill_page_desc(skb, i, page, 0, chunk);
    		data_len -= chunk;
    		npages -= 1 << order;
    	}
    	return skb;
    
    failure:
    	kfree_skb(skb);
    	return NULL;
    }
    EXPORT_SYMBOL(alloc_skb_with_frags);