text: /*
   *	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/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/sctp.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 <linux/uaccess.h>
  #include <trace/events/skb.h>
  #include <linux/highmem.h>
  #include <linux/capability.h>
  #include <linux/user_namespace.h>
  
  struct kmem_cache *skbuff_head_cache __ro_after_init;
  static struct kmem_cache *skbuff_fclone_cache __ro_after_init;
  int sysctl_max_skb_frags __read_mostly = MAX_SKB_FRAGS;
  EXPORT_SYMBOL(sysctl_max_skb_frags);
  
  /**
   *	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.
   *
   */
  
  /**
   *	__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;
  	refcount_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);
  
  	if (flags & SKB_ALLOC_FCLONE) {
  		struct sk_buff_fclones *fclones;
  
  		fclones = container_of(skb, struct sk_buff_fclones, skb1);
  
  		skb->fclone = SKB_FCLONE_ORIG;
  		refcount_set(&fclones->fclone_ref, 1);
  
  		fclones->skb2.fclone = SKB_FCLONE_CLONE;
  	}
  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 data, 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
   *  or vmalloc()
   * 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);
  	refcount_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);
  
  	return skb;
  }
  
  /* build_skb() is wrapper over __build_skb(), that specifically
   * takes care of skb->head and skb->pfmemalloc
   * This means that if @frag_size is not zero, then @data must be backed
   * by a page fragment, not kmalloc() or vmalloc()
   */
  struct sk_buff *build_skb(void *data, unsigned int frag_size)
  {
  	struct sk_buff *skb = __build_skb(data, frag_size);
  
  	if (skb && frag_size) {
  		skb->head_frag = 1;
  		if (page_is_pfmemalloc(virt_to_head_page(data)))
  			skb->pfmemalloc = 1;
  	}
  	return skb;
  }
  EXPORT_SYMBOL(build_skb);
  
  #define NAPI_SKB_CACHE_SIZE	64
  
  struct napi_alloc_cache {
  	struct page_frag_cache page;
  	unsigned int skb_count;
  	void *skb_cache[NAPI_SKB_CACHE_SIZE];
  };
  
  static DEFINE_PER_CPU(struct page_frag_cache, netdev_alloc_cache);
  static DEFINE_PER_CPU(struct napi_alloc_cache, napi_alloc_cache);
  
  static void *__netdev_alloc_frag(unsigned int fragsz, gfp_t gfp_mask)
  {
  	struct page_frag_cache *nc;
  	unsigned long flags;
  	void *data;
  
  	local_irq_save(flags);
  	nc = this_cpu_ptr(&netdev_alloc_cache);
  	data = page_frag_alloc(nc, 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)
  {
  	fragsz = SKB_DATA_ALIGN(fragsz);
  
  	return __netdev_alloc_frag(fragsz, GFP_ATOMIC);
  }
  EXPORT_SYMBOL(netdev_alloc_frag);
  
  static void *__napi_alloc_frag(unsigned int fragsz, gfp_t gfp_mask)
  {
  	struct napi_alloc_cache *nc = this_cpu_ptr(&napi_alloc_cache);
  
  	return page_frag_alloc(&nc->page, fragsz, gfp_mask);
  }
  
  void *napi_alloc_frag(unsigned int fragsz)
  {
  	fragsz = SKB_DATA_ALIGN(fragsz);
  
  	return __napi_alloc_frag(fragsz, GFP_ATOMIC);
  }
  EXPORT_SYMBOL(napi_alloc_frag);
  
  /**
   *	__netdev_alloc_skb - allocate an skbuff for rx on a specific device
   *	@dev: network device to receive on
   *	@len: 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 NET_SKB_PAD 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 len,
  				   gfp_t gfp_mask)
  {
  	struct page_frag_cache *nc;
  	unsigned long flags;
  	struct sk_buff *skb;
  	bool pfmemalloc;
  	void *data;
  
  	len += NET_SKB_PAD;
  
  	if ((len > SKB_WITH_OVERHEAD(PAGE_SIZE)) ||
  	    (gfp_mask & (__GFP_DIRECT_RECLAIM | GFP_DMA))) {
  		skb = __alloc_skb(len, gfp_mask, SKB_ALLOC_RX, NUMA_NO_NODE);
  		if (!skb)
  			goto skb_fail;
  		goto skb_success;
  	}
  
  	len += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
  	len = SKB_DATA_ALIGN(len);
  
  	if (sk_memalloc_socks())
  		gfp_mask |= __GFP_MEMALLOC;
  
  	local_irq_save(flags);
  
  	nc = this_cpu_ptr(&netdev_alloc_cache);
  	data = page_frag_alloc(nc, len, gfp_mask);
  	pfmemalloc = nc->pfmemalloc;
  
  	local_irq_restore(flags);
  
  	if (unlikely(!data))
  		return NULL;
  
  	skb = __build_skb(data, len);
  	if (unlikely(!skb)) {
  		skb_free_frag(data);
  		return NULL;
  	}
  
  	/* use OR instead of assignment to avoid clearing of bits in mask */
  	if (pfmemalloc)
  		skb->pfmemalloc = 1;
  	skb->head_frag = 1;
  
  skb_success:
  	skb_reserve(skb, NET_SKB_PAD);
  	skb->dev = dev;
  
  skb_fail:
  	return skb;
  }
  EXPORT_SYMBOL(__netdev_alloc_skb);
  
  /**
   *	__napi_alloc_skb - allocate skbuff for rx in a specific NAPI instance
   *	@napi: napi instance this buffer was allocated for
   *	@len: length to allocate
   *	@gfp_mask: get_free_pages mask, passed to alloc_skb and alloc_pages
   *
   *	Allocate a new sk_buff for use in NAPI receive.  This buffer will
   *	attempt to allocate the head from a special reserved region used
   *	only for NAPI Rx allocation.  By doing this we can save several
   *	CPU cycles by avoiding having to disable and re-enable IRQs.
   *
   *	%NULL is returned if there is no free memory.
   */
  struct sk_buff *__napi_alloc_skb(struct napi_struct *napi, unsigned int len,
  				 gfp_t gfp_mask)
  {
  	struct napi_alloc_cache *nc = this_cpu_ptr(&napi_alloc_cache);
  	struct sk_buff *skb;
  	void *data;
  
  	len += NET_SKB_PAD + NET_IP_ALIGN;
  
  	if ((len > SKB_WITH_OVERHEAD(PAGE_SIZE)) ||
  	    (gfp_mask & (__GFP_DIRECT_RECLAIM | GFP_DMA))) {
  		skb = __alloc_skb(len, gfp_mask, SKB_ALLOC_RX, NUMA_NO_NODE);
  		if (!skb)
  			goto skb_fail;
  		goto skb_success;
  	}
  
  	len += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
  	len = SKB_DATA_ALIGN(len);
  
  	if (sk_memalloc_socks())
  		gfp_mask |= __GFP_MEMALLOC;
  
  	data = page_frag_alloc(&nc->page, len, gfp_mask);
  	if (unlikely(!data))
  		return NULL;
  
  	skb = __build_skb(data, len);
  	if (unlikely(!skb)) {
  		skb_free_frag(data);
  		return NULL;
  	}
  
  	/* use OR instead of assignment to avoid clearing of bits in mask */
  	if (nc->page.pfmemalloc)
  		skb->pfmemalloc = 1;
  	skb->head_frag = 1;
  
  skb_success:
  	skb_reserve(skb, NET_SKB_PAD + NET_IP_ALIGN);
  	skb->dev = napi->dev;
  
  skb_fail:
  	return skb;
  }
  EXPORT_SYMBOL(__napi_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)
  {
  	unsigned char *head = skb->head;
  
  	if (skb->head_frag)
  		skb_free_frag(head);
  	else
  		kfree(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 (shinfo->frag_list)
  		kfree_skb_list(shinfo->frag_list);
  
  	skb_zcopy_clear(skb, true);
  	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 (refcount_read(&fclones->fclone_ref) == 1)
  			goto fastpath;
  		break;
  
  	default: /* SKB_FCLONE_CLONE */
  		fclones = container_of(skb, struct sk_buff_fclones, skb2);
  		break;
  	}
  	if (!refcount_dec_and_test(&fclones->fclone_ref))
  		return;
  fastpath:
  	kmem_cache_free(skbuff_fclone_cache, fclones);
  }
  
  void skb_release_head_state(struct sk_buff *skb)
  {
  	skb_dst_drop(skb);
  	secpath_reset(skb);
  	if (skb->destructor) {
  		WARN_ON(in_irq());
  		skb->destructor(skb);
  	}
  #if IS_ENABLED(CONFIG_NF_CONNTRACK)
  	nf_conntrack_put(skb_nfct(skb));
  #endif
  #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
  	nf_bridge_put(skb->nf_bridge);
  #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 (!skb_unref(skb))
  		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)
  {
  	skb_zcopy_clear(skb, true);
  }
  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 (!skb_unref(skb))
  		return;
  
  	trace_consume_skb(skb);
  	__kfree_skb(skb);
  }
  EXPORT_SYMBOL(consume_skb);
  
  /**
   *	consume_stateless_skb - free an skbuff, assuming it is stateless
   *	@skb: buffer to free
   *
   *	Alike consume_skb(), but this variant assumes that this is the last
   *	skb reference and all the head states have been already dropped
   */
  void __consume_stateless_skb(struct sk_buff *skb)
  {
  	trace_consume_skb(skb);
  	skb_release_data(skb);
  	kfree_skbmem(skb);
  }
  
  void __kfree_skb_flush(void)
  {
  	struct napi_alloc_cache *nc = this_cpu_ptr(&napi_alloc_cache);
  
  	/* flush skb_cache if containing objects */
  	if (nc->skb_count) {
  		kmem_cache_free_bulk(skbuff_head_cache, nc->skb_count,
  				     nc->skb_cache);
  		nc->skb_count = 0;
  	}
  }
  
  static inline void _kfree_skb_defer(struct sk_buff *skb)
  {
  	struct napi_alloc_cache *nc = this_cpu_ptr(&napi_alloc_cache);
  
  	/* drop skb->head and call any destructors for packet */
  	skb_release_all(skb);
  
  	/* record skb to CPU local list */
  	nc->skb_cache[nc->skb_count++] = skb;
  
  #ifdef CONFIG_SLUB
  	/* SLUB writes into objects when freeing */
  	prefetchw(skb);
  #endif
  
  	/* flush skb_cache if it is filled */
  	if (unlikely(nc->skb_count == NAPI_SKB_CACHE_SIZE)) {
  		kmem_cache_free_bulk(skbuff_head_cache, NAPI_SKB_CACHE_SIZE,
  				     nc->skb_cache);
  		nc->skb_count = 0;
  	}
  }
  void __kfree_skb_defer(struct sk_buff *skb)
  {
  	_kfree_skb_defer(skb);
  }
  
  void napi_consume_skb(struct sk_buff *skb, int budget)
  {
  	if (unlikely(!skb))
  		return;
  
  	/* Zero budget indicate non-NAPI context called us, like netpoll */
  	if (unlikely(!budget)) {
  		dev_consume_skb_any(skb);
  		return;
  	}
  
  	if (!skb_unref(skb))
  		return;
  
  	/* if reaching here SKB is ready to free */
  	trace_consume_skb(skb);
  
  	/* if SKB is a clone, don't handle this case */
  	if (skb->fclone != SKB_FCLONE_UNAVAILABLE) {
  		__kfree_skb(skb);
  		return;
  	}
  
  	_kfree_skb_defer(skb);
  }
  EXPORT_SYMBOL(napi_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_XPS
  	CHECK_SKB_FIELD(sender_cpu);
  #endif
  #ifdef CONFIG_NET_SCHED
  	CHECK_SKB_FIELD(tc_index);
  #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->peeked = 0;
  	C(pfmemalloc);
  	n->destructor = NULL;
  	C(tail);
  	C(end);
  	C(head);
  	C(head_frag);
  	C(data);
  	C(truesize);
  	refcount_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);
  
  int mm_account_pinned_pages(struct mmpin *mmp, size_t size)
  {
  	unsigned long max_pg, num_pg, new_pg, old_pg;
  	struct user_struct *user;
  
  	if (capable(CAP_IPC_LOCK) || !size)
  		return 0;
  
  	num_pg = (size >> PAGE_SHIFT) + 2;	/* worst case */
  	max_pg = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
  	user = mmp->user ? : current_user();
  
  	do {
  		old_pg = atomic_long_read(&user->locked_vm);
  		new_pg = old_pg + num_pg;
  		if (new_pg > max_pg)
  			return -ENOBUFS;
  	} while (atomic_long_cmpxchg(&user->locked_vm, old_pg, new_pg) !=
  		 old_pg);
  
  	if (!mmp->user) {
  		mmp->user = get_uid(user);
  		mmp->num_pg = num_pg;
  	} else {
  		mmp->num_pg += num_pg;
  	}
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(mm_account_pinned_pages);
  
  void mm_unaccount_pinned_pages(struct mmpin *mmp)
  {
  	if (mmp->user) {
  		atomic_long_sub(mmp->num_pg, &mmp->user->locked_vm);
  		free_uid(mmp->user);
  	}
  }
  EXPORT_SYMBOL_GPL(mm_unaccount_pinned_pages);
  
  struct ubuf_info *sock_zerocopy_alloc(struct sock *sk, size_t size)
  {
  	struct ubuf_info *uarg;
  	struct sk_buff *skb;
  
  	WARN_ON_ONCE(!in_task());
  
  	skb = sock_omalloc(sk, 0, GFP_KERNEL);
  	if (!skb)
  		return NULL;
  
  	BUILD_BUG_ON(sizeof(*uarg) > sizeof(skb->cb));
  	uarg = (void *)skb->cb;
  	uarg->mmp.user = NULL;
  
  	if (mm_account_pinned_pages(&uarg->mmp, size)) {
  		kfree_skb(skb);
  		return NULL;
  	}
  
  	uarg->callback = sock_zerocopy_callback;
  	uarg->id = ((u32)atomic_inc_return(&sk->sk_zckey)) - 1;
  	uarg->len = 1;
  	uarg->bytelen = size;
  	uarg->zerocopy = 1;
  	refcount_set(&uarg->refcnt, 1);
  	sock_hold(sk);
  
  	return uarg;
  }
  EXPORT_SYMBOL_GPL(sock_zerocopy_alloc);
  
  static inline struct sk_buff *skb_from_uarg(struct ubuf_info *uarg)
  {
  	return container_of((void *)uarg, struct sk_buff, cb);
  }
  
  struct ubuf_info *sock_zerocopy_realloc(struct sock *sk, size_t size,
  					struct ubuf_info *uarg)
  {
  	if (uarg) {
  		const u32 byte_limit = 1 << 19;		/* limit to a few TSO */
  		u32 bytelen, next;
  
  		/* realloc only when socket is locked (TCP, UDP cork),
  		 * so uarg->len and sk_zckey access is serialized
  		 */
  		if (!sock_owned_by_user(sk)) {
  			WARN_ON_ONCE(1);
  			return NULL;
  		}
  
  		bytelen = uarg->bytelen + size;
  		if (uarg->len == USHRT_MAX - 1 || bytelen > byte_limit) {
  			/* TCP can create new skb to attach new uarg */
  			if (sk->sk_type == SOCK_STREAM)
  				goto new_alloc;
  			return NULL;
  		}
  
  		next = (u32)atomic_read(&sk->sk_zckey);
  		if ((u32)(uarg->id + uarg->len) == next) {
  			if (mm_account_pinned_pages(&uarg->mmp, size))
  				return NULL;
  			uarg->len++;
  			uarg->bytelen = bytelen;
  			atomic_set(&sk->sk_zckey, ++next);
  			sock_zerocopy_get(uarg);
  			return uarg;
  		}
  	}
  
  new_alloc:
  	return sock_zerocopy_alloc(sk, size);
  }
  EXPORT_SYMBOL_GPL(sock_zerocopy_realloc);
  
  static bool skb_zerocopy_notify_extend(struct sk_buff *skb, u32 lo, u16 len)
  {
  	struct sock_exterr_skb *serr = SKB_EXT_ERR(skb);
  	u32 old_lo, old_hi;
  	u64 sum_len;
  
  	old_lo = serr->ee.ee_info;
  	old_hi = serr->ee.ee_data;
  	sum_len = old_hi - old_lo + 1ULL + len;
  
  	if (sum_len >= (1ULL << 32))
  		return false;
  
  	if (lo != old_hi + 1)
  		return false;
  
  	serr->ee.ee_data += len;
  	return true;
  }
  
  void sock_zerocopy_callback(struct ubuf_info *uarg, bool success)
  {
  	struct sk_buff *tail, *skb = skb_from_uarg(uarg);
  	struct sock_exterr_skb *serr;
  	struct sock *sk = skb->sk;
  	struct sk_buff_head *q;
  	unsigned long flags;
  	u32 lo, hi;
  	u16 len;
  
  	mm_unaccount_pinned_pages(&uarg->mmp);
  
  	/* if !len, there was only 1 call, and it was aborted
  	 * so do not queue a completion notification
  	 */
  	if (!uarg->len || sock_flag(sk, SOCK_DEAD))
  		goto release;
  
  	len = uarg->len;
  	lo = uarg->id;
  	hi = uarg->id + len - 1;
  
  	serr = SKB_EXT_ERR(skb);
  	memset(serr, 0, sizeof(*serr));
  	serr->ee.ee_errno = 0;
  	serr->ee.ee_origin = SO_EE_ORIGIN_ZEROCOPY;
  	serr->ee.ee_data = hi;
  	serr->ee.ee_info = lo;
  	if (!success)
  		serr->ee.ee_code |= SO_EE_CODE_ZEROCOPY_COPIED;
  
  	q = &sk->sk_error_queue;
  	spin_lock_irqsave(&q->lock, flags);
  	tail = skb_peek_tail(q);
  	if (!tail || SKB_EXT_ERR(tail)->ee.ee_origin != SO_EE_ORIGIN_ZEROCOPY ||
  	    !skb_zerocopy_notify_extend(tail, lo, len)) {
  		__skb_queue_tail(q, skb);
  		skb = NULL;
  	}
  	spin_unlock_irqrestore(&q->lock, flags);
  
  	sk->sk_error_report(sk);
  
  release:
  	consume_skb(skb);
  	sock_put(sk);
  }
  EXPORT_SYMBOL_GPL(sock_zerocopy_callback);
  
  void sock_zerocopy_put(struct ubuf_info *uarg)
  {
  	if (uarg && refcount_dec_and_test(&uarg->refcnt)) {
  		if (uarg->callback)
  			uarg->callback(uarg, uarg->zerocopy);
  		else
  			consume_skb(skb_from_uarg(uarg));
  	}
  }
  EXPORT_SYMBOL_GPL(sock_zerocopy_put);
  
  void sock_zerocopy_put_abort(struct ubuf_info *uarg)
  {
  	if (uarg) {
  		struct sock *sk = skb_from_uarg(uarg)->sk;
  
  		atomic_dec(&sk->sk_zckey);
  		uarg->len--;
  
  		sock_zerocopy_put(uarg);
  	}
  }
  EXPORT_SYMBOL_GPL(sock_zerocopy_put_abort);
  
  extern int __zerocopy_sg_from_iter(struct sock *sk, struct sk_buff *skb,
  				   struct iov_iter *from, size_t length);
  
  int skb_zerocopy_iter_stream(struct sock *sk, struct sk_buff *skb,
  			     struct msghdr *msg, int len,
  			     struct ubuf_info *uarg)
  {
  	struct ubuf_info *orig_uarg = skb_zcopy(skb);
  	struct iov_iter orig_iter = msg->msg_iter;
  	int err, orig_len = skb->len;
  
  	/* An skb can only point to one uarg. This edge case happens when
  	 * TCP appends to an skb, but zerocopy_realloc triggered a new alloc.
  	 */
  	if (orig_uarg && uarg != orig_uarg)
  		return -EEXIST;
  
  	err = __zerocopy_sg_from_iter(sk, skb, &msg->msg_iter, len);
  	if (err == -EFAULT || (err == -EMSGSIZE && skb->len == orig_len)) {
  		struct sock *save_sk = skb->sk;
  
  		/* Streams do not free skb on error. Reset to prev state. */
  		msg->msg_iter = orig_iter;
  		skb->sk = sk;
  		___pskb_trim(skb, orig_len);
  		skb->sk = save_sk;
  		return err;
  	}
  
  	skb_zcopy_set(skb, uarg);
  	return skb->len - orig_len;
  }
  EXPORT_SYMBOL_GPL(skb_zerocopy_iter_stream);
  
  static int skb_zerocopy_clone(struct sk_buff *nskb, struct sk_buff *orig,
  			      gfp_t gfp_mask)
  {
  	if (skb_zcopy(orig)) {
  		if (skb_zcopy(nskb)) {
  			/* !gfp_mask callers are verified to !skb_zcopy(nskb) */
  			if (!gfp_mask) {
  				WARN_ON_ONCE(1);
  				return -ENOMEM;
  			}
  			if (skb_uarg(nskb) == skb_uarg(orig))
  				return 0;
  			if (skb_copy_ubufs(nskb, GFP_ATOMIC))
  				return -EIO;
  		}
  		skb_zcopy_set(nskb, skb_uarg(orig));
  	}
  	return 0;
  }
  
  /**
   *	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 num_frags = skb_shinfo(skb)->nr_frags;
  	struct page *page, *head = NULL;
  	int i, new_frags;
  	u32 d_off;
  
  	if (skb_shared(skb) || skb_unclone(skb, gfp_mask))
  		return -EINVAL;
  
  	if (!num_frags)
  		goto release;
  
  	new_frags = (__skb_pagelen(skb) + PAGE_SIZE - 1) >> PAGE_SHIFT;
  	for (i = 0; i < new_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;
  		}
  		set_page_private(page, (unsigned long)head);
  		head = page;
  	}
  
  	page = head;
  	d_off = 0;
  	for (i = 0; i < num_frags; i++) {
  		skb_frag_t *f = &skb_shinfo(skb)->frags[i];
  		u32 p_off, p_len, copied;
  		struct page *p;
  		u8 *vaddr;
  
  		skb_frag_foreach_page(f, f->page_offset, skb_frag_size(f),
  				      p, p_off, p_len, copied) {
  			u32 copy, done = 0;
  			vaddr = kmap_atomic(p);
  
  			while (done < p_len) {
  				if (d_off == PAGE_SIZE) {
  					d_off = 0;
  					page = (struct page *)page_private(page);
  				}
  				copy = min_t(u32, PAGE_SIZE - d_off, p_len - done);
  				memcpy(page_address(page) + d_off,
  				       vaddr + p_off + done, copy);
  				done += copy;
  				d_off += copy;
  			}
  			kunmap_atomic(vaddr);
  		}
  	}
  
  	/* skb frags release userspace buffers */
  	for (i = 0; i < num_frags; i++)
  		skb_frag_unref(skb, i);
  
  	/* skb frags point to kernel buffers */
  	for (i = 0; i < new_frags - 1; i++) {
  		__skb_fill_page_desc(skb, i, head, 0, PAGE_SIZE);
  		head = (struct page *)page_private(head);
  	}
  	__skb_fill_page_desc(skb, new_frags - 1, head, 0, d_off);
  	skb_shinfo(skb)->nr_frags = new_frags;
  
  release:
  	skb_zcopy_clear(skb, false);
  	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 &&
  	    refcount_read(&fclones->fclone_ref) == 1) {
  		n = &fclones->skb2;
  		refcount_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;
  
  		n->fclone = SKB_FCLONE_UNAVAILABLE;
  	}
  
  	return __skb_clone(n, skb);
  }
  EXPORT_SYMBOL(skb_clone);
  
  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;
  }
  EXPORT_SYMBOL(skb_headers_offset_update);
  
  void skb_copy_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;
  }
  EXPORT_SYMBOL(skb_copy_header);
  
  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);
  
  	BUG_ON(skb_copy_bits(skb, -headerlen, n->head, headerlen + skb->len));
  
  	skb_copy_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) ||
  		    skb_zerocopy_clone(n, 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);
  	}
  
  	skb_copy_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, osize = skb_end_offset(skb);
  	int size = osize + nhead + ntail;
  	long off;
  	u8 *data;
  
  	BUG_ON(nhead < 0);
  
  	BUG_ON(skb_shared(skb));
  
  	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)) {
  		if (skb_orphan_frags(skb, gfp_mask))
  			goto nofrags;
  		if (skb_zcopy(skb))
  			refcount_inc(&skb_uarg(skb)->refcnt);
  		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);
  
  	skb_metadata_clear(skb);
  
  	/* It is not generally safe to change skb->truesize.
  	 * For the moment, we really care of rx path, or
  	 * when skb is orphaned (not attached to a socket).
  	 */
  	if (!skb->sk || skb->destructor == sock_edemux)
  		skb->truesize += size - osize;
  
  	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. */
  	BUG_ON(skb_copy_bits(skb, -head_copy_len, n->head + head_copy_off,
  			     skb->len + head_copy_len));
  
  	skb_copy_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
   *	@free_on_error: free buffer on error
   *
   *	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
   *	if @free_on_error is true.
   */
  
  int __skb_pad(struct sk_buff *skb, int pad, bool free_on_error)
  {
  	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:
  	if (free_on_error)
  		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.
   */
  
  void *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.
   */
  void *skb_put(struct sk_buff *skb, unsigned int len)
  {
  	void *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.
   */
  void *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.
   */
  void *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);
  	}
  
  	if (!skb->sk || skb->destructor == sock_edemux)
  		skb_condense(skb);
  	return 0;
  }
  EXPORT_SYMBOL(___pskb_trim);
  
  /* Note : use pskb_trim_rcsum() instead of calling this directly
   */
  int pskb_trim_rcsum_slow(struct sk_buff *skb, unsigned int len)
  {
  	if (skb->ip_summed == CHECKSUM_COMPLETE) {
  		int delta = skb->len - len;
  
  		skb->csum = csum_block_sub(skb->csum,
  					   skb_checksum(skb, len, delta, 0),
  					   len);
  	}
  	return __pskb_trim(skb, len);
  }
  EXPORT_SYMBOL(pskb_trim_rcsum_slow);
  
  /**
   *	__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.
   */
  void *__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;
  	}
  
  	BUG_ON(skb_copy_bits(skb, skb_headlen(skb),
  			     skb_tail_pointer(skb), delta));
  
  	/* 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 is 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);
  				if (!i)
  					goto end;
  				eat = 0;
  			}
  			k++;
  		}
  	}
  	skb_shinfo(skb)->nr_frags = k;
  
  end:
  	skb->tail     += delta;
  	skb->data_len -= delta;
  
  	if (!skb->data_len)
  		skb_zcopy_clear(skb, false);
  
  	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) {
  			u32 p_off, p_len, copied;
  			struct page *p;
  			u8 *vaddr;
  
  			if (copy > len)
  				copy = len;
  
  			skb_frag_foreach_page(f,
  					      f->page_offset + offset - start,
  					      copy, p, p_off, p_len, copied) {
  				vaddr = kmap_atomic(p);
  				memcpy(to + copied, vaddr + p_off, p_len);
  				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;
  	struct sk_buff *iter;
  
  	/* 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;
  	}
  
  	skb_walk_frags(skb, iter) {
  		if (*offset >= iter->len) {
  			*offset -= iter->len;
  			continue;
  		}
  		/* __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(iter, pipe, offset, len, spd, sk))
  			return true;
  	}
  
  	return false;
  }
  
  /*
   * Map data from the skb to a pipe. Should handle both the linear part,
   * the fragments, and the frag list.
   */
  int skb_splice_bits(struct sk_buff *skb, struct sock *sk, 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,
  		.ops = &nosteal_pipe_buf_ops,
  		.spd_release = sock_spd_release,
  	};
  	int ret = 0;
  
  	__skb_splice_bits(skb, pipe, &offset, &tlen, &spd, sk);
  
  	if (spd.nr_pages)
  		ret = splice_to_pipe(pipe, &spd);
  
  	return ret;
  }
  EXPORT_SYMBOL_GPL(skb_splice_bits);
  
  /* Send skb data on a socket. Socket must be locked. */
  int skb_send_sock_locked(struct sock *sk, struct sk_buff *skb, int offset,
  			 int len)
  {
  	unsigned int orig_len = len;
  	struct sk_buff *head = skb;
  	unsigned short fragidx;
  	int slen, ret;
  
  do_frag_list:
  
  	/* Deal with head data */
  	while (offset < skb_headlen(skb) && len) {
  		struct kvec kv;
  		struct msghdr msg;
  
  		slen = min_t(int, len, skb_headlen(skb) - offset);
  		kv.iov_base = skb->data + offset;
  		kv.iov_len = slen;
  		memset(&msg, 0, sizeof(msg));
  		msg.msg_flags = MSG_DONTWAIT;
  
  		ret = kernel_sendmsg_locked(sk, &msg, &kv, 1, slen);
  		if (ret <= 0)
  			goto error;
  
  		offset += ret;
  		len -= ret;
  	}
  
  	/* All the data was skb head? */
  	if (!len)
  		goto out;
  
  	/* Make offset relative to start of frags */
  	offset -= skb_headlen(skb);
  
  	/* Find where we are in frag list */
  	for (fragidx = 0; fragidx < skb_shinfo(skb)->nr_frags; fragidx++) {
  		skb_frag_t *frag  = &skb_shinfo(skb)->frags[fragidx];
  
  		if (offset < frag->size)
  			break;
  
  		offset -= frag->size;
  	}
  
  	for (; len && fragidx < skb_shinfo(skb)->nr_frags; fragidx++) {
  		skb_frag_t *frag  = &skb_shinfo(skb)->frags[fragidx];
  
  		slen = min_t(size_t, len, frag->size - offset);
  
  		while (slen) {
  			ret = kernel_sendpage_locked(sk, frag->page.p,
  						     frag->page_offset + offset,
  						     slen, MSG_DONTWAIT);
  			if (ret <= 0)
  				goto error;
  
  			len -= ret;
  			offset += ret;
  			slen -= ret;
  		}
  
  		offset = 0;
  	}
  
  	if (len) {
  		/* Process any frag lists */
  
  		if (skb == head) {
  			if (skb_has_frag_list(skb)) {
  				skb = skb_shinfo(skb)->frag_list;
  				goto do_frag_list;
  			}
  		} else if (skb->next) {
  			skb = skb->next;
  			goto do_frag_list;
  		}
  	}
  
  out:
  	return orig_len - len;
  
  error:
  	return orig_len == len ? ret : orig_len - len;
  }
  EXPORT_SYMBOL_GPL(skb_send_sock_locked);
  
  /* Send skb data on a socket. */
  int skb_send_sock(struct sock *sk, struct sk_buff *skb, int offset, int len)
  {
  	int ret = 0;
  
  	lock_sock(sk);
  	ret = skb_send_sock_locked(sk, skb, offset, len);
  	release_sock(sk);
  
  	return ret;
  }
  EXPORT_SYMBOL_GPL(skb_send_sock);
  
  /**
   *	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) {
  			u32 p_off, p_len, copied;
  			struct page *p;
  			u8 *vaddr;
  
  			if (copy > len)
  				copy = len;
  
  			skb_frag_foreach_page(frag,
  					      frag->page_offset + offset - start,
  					      copy, p, p_off, p_len, copied) {
  				vaddr = kmap_atomic(p);
  				memcpy(vaddr + p_off, from + copied, p_len);
  				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) {
  			u32 p_off, p_len, copied;
  			struct page *p;
  			__wsum csum2;
  			u8 *vaddr;
  
  			if (copy > len)
  				copy = len;
  
  			skb_frag_foreach_page(frag,
  					      frag->page_offset + offset - start,
  					      copy, p, p_off, p_len, copied) {
  				vaddr = kmap_atomic(p);
  				csum2 = ops->update(vaddr + p_off, p_len, 0);
  				kunmap_atomic(vaddr);
  				csum = ops->combine(csum, csum2, pos, p_len);
  				pos += p_len;
  			}
  
  			if (!(len -= copy))
  				return csum;
  			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) {
  			__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) {
  			skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
  			u32 p_off, p_len, copied;
  			struct page *p;
  			__wsum csum2;
  			u8 *vaddr;
  
  			if (copy > len)
  				copy = len;
  
  			skb_frag_foreach_page(frag,
  					      frag->page_offset + offset - start,
  					      copy, p, p_off, p_len, copied) {
  				vaddr = kmap_atomic(p);
  				csum2 = csum_partial_copy_nocheck(vaddr + p_off,
  								  to + copied,
  								  p_len, 0);
  				kunmap_atomic(vaddr);
  				csum = csum_block_add(csum, csum2, pos);
  				pos += p_len;
  			}
  
  			if (!(len -= copy))
  				return csum;
  			offset += copy;
  			to     += 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);
  
  static __wsum warn_crc32c_csum_update(const void *buff, int len, __wsum sum)
  {
  	net_warn_ratelimited(
  		"%s: attempt to compute crc32c without libcrc32c.ko\n",
  		__func__);
  	return 0;
  }
  
  static __wsum warn_crc32c_csum_combine(__wsum csum, __wsum csum2,
  				       int offset, int len)
  {
  	net_warn_ratelimited(
  		"%s: attempt to compute crc32c without libcrc32c.ko\n",
  		__func__);
  	return 0;
  }
  
  static const struct skb_checksum_ops default_crc32c_ops = {
  	.update  = warn_crc32c_csum_update,
  	.combine = warn_crc32c_csum_combine,
  };
  
  const struct skb_checksum_ops *crc32c_csum_stub __read_mostly =
  	&default_crc32c_ops;
  EXPORT_SYMBOL(crc32c_csum_stub);
  
   /**
   *	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;
  	}
  	skb_zerocopy_clone(to, from, GFP_ATOMIC);
  
  	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_rbtree_purge - empty a skb rbtree
   *	@root: root of the rbtree to empty
   *	Return value: the sum of truesizes of all purged skbs.
   *
   *	Delete all buffers on an &sk_buff rbtree. Each buffer is removed from
   *	the list and one reference dropped. This function does not take
   *	any lock. Synchronization should be handled by the caller (e.g., TCP
   *	out-of-order queue is protected by the socket lock).
   */
  unsigned int skb_rbtree_purge(struct rb_root *root)
  {
  	struct rb_node *p = rb_first(root);
  	unsigned int sum = 0;
  
  	while (p) {
  		struct sk_buff *skb = rb_entry(p, struct sk_buff, rbnode);
  
  		p = rb_next(p);
  		rb_erase(&skb->rbnode, root);
  		sum += skb->truesize;
  		kfree_skb(skb);
  	}
  	return sum;
  }
  
  /**
   *	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;
  	skb_zerocopy_clone(skb1, skb, 0);
  	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);
  
  	if (skb_headlen(skb))
  		return 0;
  	if (skb_zcopy(tgt) || skb_zcopy(skb))
  		return 0;
  
  	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
   *
   * 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;
  		refcount_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);
  
  int skb_append_pagefrags(struct sk_buff *skb, struct page *page,
  			 int offset, size_t size)
  {
  	int i = skb_shinfo(skb)->nr_frags;
  
  	if (skb_can_coalesce(skb, i, page, offset)) {
  		skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], size);
  	} else if (i < MAX_SKB_FRAGS) {
  		get_page(page);
  		skb_fill_page_desc(skb, i, page, offset, size);
  	} else {
  		return -EMSGSIZE;
  	}
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(skb_append_pagefrags);
  
  /**
   *	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.
   */
  void *skb_pull_rcsum(struct sk_buff *skb, unsigned int len)
  {
  	unsigned char *data = skb->data;
  
  	BUG_ON(len > skb->len);
  	__skb_pull(skb, len);
  	skb_postpull_rcsum(skb, data, len);
  	return skb->data;
  }
  EXPORT_SYMBOL_GPL(skb_pull_rcsum);
  
  static inline skb_frag_t skb_head_frag_to_page_desc(struct sk_buff *frag_skb)
  {
  	skb_frag_t head_frag;
  	struct page *page;
  
  	page = virt_to_head_page(frag_skb->head);
  	head_frag.page.p = page;
  	head_frag.page_offset = frag_skb->data -
  		(unsigned char *)page_address(page);
  	head_frag.size = skb_headlen(frag_skb);
  	return head_frag;
  }
  
  /**
   *	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 partial_segs = 0;
  	unsigned int headroom;
  	unsigned int len = head_skb->len;
  	__be16 proto;
  	bool csum, sg;
  	int nfrags = skb_shinfo(head_skb)->nr_frags;
  	int err = -ENOMEM;
  	int i = 0;
  	int pos;
  	int dummy;
  
  	if (list_skb && !list_skb->head_frag && skb_headlen(list_skb) &&
  	    (skb_shinfo(head_skb)->gso_type & SKB_GSO_DODGY)) {
  		/* gso_size is untrusted, and we have a frag_list with a linear
  		 * non head_frag head.
  		 *
  		 * (we assume checking the first list_skb member suffices;
  		 * i.e if either of the list_skb members have non head_frag
  		 * head, then the first one has too).
  		 *
  		 * If head_skb's headlen does not fit requested gso_size, it
  		 * means that the frag_list members do NOT terminate on exact
  		 * gso_size boundaries. Hence we cannot perform skb_frag_t page
  		 * sharing. Therefore we must fallback to copying the frag_list
  		 * skbs; we do so by disabling SG.
  		 */
  		if (mss != GSO_BY_FRAGS && mss != skb_headlen(head_skb))
  			features &= ~NETIF_F_SG;
  	}
  
  	__skb_push(head_skb, doffset);
  	proto = skb_network_protocol(head_skb, &dummy);
  	if (unlikely(!proto))
  		return ERR_PTR(-EINVAL);
  
  	sg = !!(features & NETIF_F_SG);
  	csum = !!can_checksum_protocol(features, proto);
  
  	if (sg && csum && (mss != GSO_BY_FRAGS))  {
  		if (!(features & NETIF_F_GSO_PARTIAL)) {
  			struct sk_buff *iter;
  			unsigned int frag_len;
  
  			if (!list_skb ||
  			    !net_gso_ok(features, skb_shinfo(head_skb)->gso_type))
  				goto normal;
  
  			/* If we get here then all the required
  			 * GSO features except frag_list are supported.
  			 * Try to split the SKB to multiple GSO SKBs
  			 * with no frag_list.
  			 * Currently we can do that only when the buffers don't
  			 * have a linear part and all the buffers except
  			 * the last are of the same length.
  			 */
  			frag_len = list_skb->len;
  			skb_walk_frags(head_skb, iter) {
  				if (frag_len != iter->len && iter->next)
  					goto normal;
  				if (skb_headlen(iter) && !iter->head_frag)
  					goto normal;
  
  				len -= iter->len;
  			}
  
  			if (len != frag_len)
  				goto normal;
  		}
  
  		/* GSO partial only requires that we trim off any excess that
  		 * doesn't fit into an MSS sized block, so take care of that
  		 * now.
  		 */
  		partial_segs = len / mss;
  		if (partial_segs > 1)
  			mss *= partial_segs;
  		else
  			partial_segs = 0;
  	}
  
  normal:
  	headroom = skb_headroom(head_skb);
  	pos = skb_headlen(head_skb);
  
  	do {
  		struct sk_buff *nskb;
  		skb_frag_t *nskb_frag;
  		int hsize;
  		int size;
  
  		if (unlikely(mss == GSO_BY_FRAGS)) {
  			len = list_skb->len;
  		} else {
  			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) {
  			if (!nskb->remcsum_offload)
  				nskb->ip_summed = CHECKSUM_NONE;
  			SKB_GSO_CB(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;
  
  		if (skb_orphan_frags(frag_skb, GFP_ATOMIC) ||
  		    skb_zerocopy_clone(nskb, frag_skb, GFP_ATOMIC))
  			goto err;
  
  		while (pos < offset + len) {
  			if (i >= nfrags) {
  				i = 0;
  				nfrags = skb_shinfo(list_skb)->nr_frags;
  				frag = skb_shinfo(list_skb)->frags;
  				frag_skb = list_skb;
  				if (!skb_headlen(list_skb)) {
  					BUG_ON(!nfrags);
  				} else {
  					BUG_ON(!list_skb->head_frag);
  
  					/* to make room for head_frag. */
  					i--;
  					frag--;
  				}
  				if (skb_orphan_frags(frag_skb, GFP_ATOMIC) ||
  				    skb_zerocopy_clone(nskb, frag_skb,
  						       GFP_ATOMIC))
  					goto err;
  
  				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);
  				err = -EINVAL;
  				goto err;
  			}
  
  			*nskb_frag = (i < 0) ? skb_head_frag_to_page_desc(frag_skb) : *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) {
  			if (skb_has_shared_frag(nskb) &&
  			    __skb_linearize(nskb))
  				goto err;
  
  			if (!nskb->remcsum_offload)
  				nskb->ip_summed = CHECKSUM_NONE;
  			SKB_GSO_CB(nskb)->csum =
  				skb_checksum(nskb, doffset,
  					     nskb->len - doffset, 0);
  			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;
  
  	if (partial_segs) {
  		struct sk_buff *iter;
  		int type = skb_shinfo(head_skb)->gso_type;
  		unsigned short gso_size = skb_shinfo(head_skb)->gso_size;
  
  		/* Update type to add partial and then remove dodgy if set */
  		type |= (features & NETIF_F_GSO_PARTIAL) / NETIF_F_GSO_PARTIAL * SKB_GSO_PARTIAL;
  		type &= ~SKB_GSO_DODGY;
  
  		/* Update GSO info and prepare to start updating headers on
  		 * our way back down the stack of protocols.
  		 */
  		for (iter = segs; iter; iter = iter->next) {
  			skb_shinfo(iter)->gso_size = gso_size;
  			skb_shinfo(iter)->gso_segs = partial_segs;
  			skb_shinfo(iter)->gso_type = type;
  			SKB_GSO_CB(iter)->data_offset = skb_headroom(iter) + doffset;
  		}
  
  		if (tail->len - doffset <= gso_size)
  			skb_shinfo(tail)->gso_size = 0;
  		else if (tail != segs)
  			skb_shinfo(tail)->gso_segs = DIV_ROUND_UP(tail->len - doffset, gso_size);
  	}
  
  	/* 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 *p, 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);
  	unsigned int len = skb_gro_len(skb);
  	unsigned int delta_truesize;
  	struct sk_buff *lp;
  
  	if (unlikely(p->len + len >= 65536 || NAPI_GRO_CB(skb)->flush))
  		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;
  	}
  
  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;
  }
  EXPORT_SYMBOL_GPL(skb_gro_receive);
  
  void __init skb_init(void)
  {
  	skbuff_head_cache = kmem_cache_create_usercopy("skbuff_head_cache",
  					      sizeof(struct sk_buff),
  					      0,
  					      SLAB_HWCACHE_ALIGN|SLAB_PANIC,
  					      offsetof(struct sk_buff, cb),
  					      sizeof_field(struct sk_buff, cb),
  					      NULL);
  	skbuff_fclone_cache = kmem_cache_create("skbuff_fclone_cache",
  						sizeof(struct sk_buff_fclones),
  						0,
  						SLAB_HWCACHE_ALIGN|SLAB_PANIC,
  						NULL);
  }
  
  static int
  __skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len,
  	       unsigned int recursion_level)
  {
  	int start = skb_headlen(skb);
  	int i, copy = start - offset;
  	struct sk_buff *frag_iter;
  	int elt = 0;
  
  	if (unlikely(recursion_level >= 24))
  		return -EMSGSIZE;
  
  	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 (unlikely(elt && sg_is_last(&sg[elt - 1])))
  				return -EMSGSIZE;
  
  			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, ret;
  
  		WARN_ON(start > offset + len);
  
  		end = start + frag_iter->len;
  		if ((copy = end - offset) > 0) {
  			if (unlikely(elt && sg_is_last(&sg[elt - 1])))
  				return -EMSGSIZE;
  
  			if (copy > len)
  				copy = len;
  			ret = __skb_to_sgvec(frag_iter, sg+elt, offset - start,
  					      copy, recursion_level + 1);
  			if (unlikely(ret < 0))
  				return ret;
  			elt += ret;
  			if ((len -= copy) == 0)
  				return elt;
  			offset += copy;
  		}
  		start = end;
  	}
  	BUG_ON(len);
  	return elt;
  }
  
  /**
   *	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. Returns either
   *	the number of scatterlist items used, or -EMSGSIZE if the contents
   *	could not fit.
   */
  int skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
  {
  	int nsg = __skb_to_sgvec(skb, sg, offset, len, 0);
  
  	if (nsg <= 0)
  		return nsg;
  
  	sg_mark_end(&sg[nsg - 1]);
  
  	return nsg;
  }
  EXPORT_SYMBOL_GPL(skb_to_sgvec);
  
  /* 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, 0);
  }
  EXPORT_SYMBOL_GPL(skb_to_sgvec_nomark);
  
  
  
  /**
   *	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);
  }
  
  static void skb_set_err_queue(struct sk_buff *skb)
  {
  	/* pkt_type of skbs received on local sockets is never PACKET_OUTGOING.
  	 * So, it is safe to (mis)use it to mark skbs on the error queue.
  	 */
  	skb->pkt_type = PACKET_OUTGOING;
  	BUILD_BUG_ON(PACKET_OUTGOING == 0);
  }
  
  /*
   * 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);
  	skb_set_err_queue(skb);
  
  	/* 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_error_report(sk);
  	return 0;
  }
  EXPORT_SYMBOL(sock_queue_err_skb);
  
  static bool is_icmp_err_skb(const struct sk_buff *skb)
  {
  	return skb && (SKB_EXT_ERR(skb)->ee.ee_origin == SO_EE_ORIGIN_ICMP ||
  		       SKB_EXT_ERR(skb)->ee.ee_origin == SO_EE_ORIGIN_ICMP6);
  }
  
  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 = NULL;
  	bool icmp_next = false;
  	unsigned long flags;
  
  	spin_lock_irqsave(&q->lock, flags);
  	skb = __skb_dequeue(q);
  	if (skb && (skb_next = skb_peek(q))) {
  		icmp_next = is_icmp_err_skb(skb_next);
  		if (icmp_next)
  			sk->sk_err = SKB_EXT_ERR(skb_next)->ee.ee_origin;
  	}
  	spin_unlock_irqrestore(&q->lock, flags);
  
  	if (is_icmp_err_skb(skb) && !icmp_next)
  		sk->sk_err = 0;
  
  	if (skb_next)
  		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 || !refcount_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,
  					bool opt_stats)
  {
  	struct sock_exterr_skb *serr;
  	int err;
  
  	BUILD_BUG_ON(sizeof(struct sock_exterr_skb) > sizeof(skb->cb));
  
  	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;
  	serr->opt_stats = opt_stats;
  	serr->header.h4.iif = skb->dev ? skb->dev->ifindex : 0;
  	if (sk->sk_tsflags & SOF_TIMESTAMPING_OPT_ID) {
  		serr->ee.ee_data = skb_shinfo(skb)->tskey;
  		if (sk->sk_protocol == IPPROTO_TCP &&
  		    sk->sk_type == SOCK_STREAM)
  			serr->ee.ee_data -= sk->sk_tskey;
  	}
  
  	err = sock_queue_err_skb(sk, skb);
  
  	if (err)
  		kfree_skb(skb);
  }
  
  static bool skb_may_tx_timestamp(struct sock *sk, bool tsonly)
  {
  	bool ret;
  
  	if (likely(sysctl_tstamp_allow_data || tsonly))
  		return true;
  
  	read_lock_bh(&sk->sk_callback_lock);
  	ret = sk->sk_socket && sk->sk_socket->file &&
  	      file_ns_capable(sk->sk_socket->file, &init_user_ns, CAP_NET_RAW);
  	read_unlock_bh(&sk->sk_callback_lock);
  	return ret;
  }
  
  void skb_complete_tx_timestamp(struct sk_buff *skb,
  			       struct skb_shared_hwtstamps *hwtstamps)
  {
  	struct sock *sk = skb->sk;
  
  	if (!skb_may_tx_timestamp(sk, false))
  		goto err;
  
  	/* Take a reference to prevent skb_orphan() from freeing the socket,
  	 * but only if the socket refcount is not zero.
  	 */
  	if (likely(refcount_inc_not_zero(&sk->sk_refcnt))) {
  		*skb_hwtstamps(skb) = *hwtstamps;
  		__skb_complete_tx_timestamp(skb, sk, SCM_TSTAMP_SND, false);
  		sock_put(sk);
  		return;
  	}
  
  err:
  	kfree_skb(skb);
  }
  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;
  	bool tsonly, opt_stats = false;
  
  	if (!sk)
  		return;
  
  	if (!hwtstamps && !(sk->sk_tsflags & SOF_TIMESTAMPING_OPT_TX_SWHW) &&
  	    skb_shinfo(orig_skb)->tx_flags & SKBTX_IN_PROGRESS)
  		return;
  
  	tsonly = sk->sk_tsflags & SOF_TIMESTAMPING_OPT_TSONLY;
  	if (!skb_may_tx_timestamp(sk, tsonly))
  		return;
  
  	if (tsonly) {
  #ifdef CONFIG_INET
  		if ((sk->sk_tsflags & SOF_TIMESTAMPING_OPT_STATS) &&
  		    sk->sk_protocol == IPPROTO_TCP &&
  		    sk->sk_type == SOCK_STREAM) {
  			skb = tcp_get_timestamping_opt_stats(sk);
  			opt_stats = true;
  		} else
  #endif
  			skb = alloc_skb(0, GFP_ATOMIC);
  	} else {
  		skb = skb_clone(orig_skb, GFP_ATOMIC);
  	}
  	if (!skb)
  		return;
  
  	if (tsonly) {
  		skb_shinfo(skb)->tx_flags |= skb_shinfo(orig_skb)->tx_flags &
  					     SKBTX_ANY_TSTAMP;
  		skb_shinfo(skb)->tskey = skb_shinfo(orig_skb)->tskey;
  	}
  
  	if (hwtstamps)
  		*skb_hwtstamps(skb) = *hwtstamps;
  	else
  		skb->tstamp = ktime_get_real();
  
  	__skb_complete_tx_timestamp(skb, sk, tstype, opt_stats);
  }
  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 = 1;
  
  	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,
  	 * but only if the socket refcount is not zero.
  	 */
  	if (likely(refcount_inc_not_zero(&sk->sk_refcnt))) {
  		err = sock_queue_err_skb(sk, skb);
  		sock_put(sk);
  	}
  	if (err)
  		kfree_skb(skb);
  }
  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)
  {
  	u32 csum_end = (u32)start + (u32)off + sizeof(__sum16);
  	u32 csum_start = skb_headroom(skb) + (u32)start;
  
  	if (unlikely(csum_start > U16_MAX || csum_end > skb_headlen(skb))) {
  		net_warn_ratelimited("bad partial csum: csum=%u/%u headroom=%u headlen=%u\n",
  				     start, off, skb_headroom(skb), skb_headlen(skb));
  		return false;
  	}
  	skb->ip_summed = CHECKSUM_PARTIAL;
  	skb->csum_start = csum_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);
  
  /**
   * skb_checksum_maybe_trim - maybe trims the given skb
   * @skb: the skb to check
   * @transport_len: the data length beyond the network header
   *
   * Checks whether the given skb has data beyond the given transport length.
   * If so, returns a cloned skb trimmed to this transport length.
   * Otherwise returns the provided skb. Returns NULL in error cases
   * (e.g. transport_len exceeds skb length or out-of-memory).
   *
   * Caller needs to set the skb transport header and free any returned skb if it
   * differs from the provided skb.
   */
  static struct sk_buff *skb_checksum_maybe_trim(struct sk_buff *skb,
  					       unsigned int transport_len)
  {
  	struct sk_buff *skb_chk;
  	unsigned int len = skb_transport_offset(skb) + transport_len;
  	int ret;
  
  	if (skb->len < len)
  		return NULL;
  	else if (skb->len == len)
  		return skb;
  
  	skb_chk = skb_clone(skb, GFP_ATOMIC);
  	if (!skb_chk)
  		return NULL;
  
  	ret = pskb_trim_rcsum(skb_chk, len);
  	if (ret) {
  		kfree_skb(skb_chk);
  		return NULL;
  	}
  
  	return skb_chk;
  }
  
  /**
   * skb_checksum_trimmed - validate checksum of an skb
   * @skb: the skb to check
   * @transport_len: the data length beyond the network header
   * @skb_chkf: checksum function to use
   *
   * Applies the given checksum function skb_chkf to the provided skb.
   * Returns a checked and maybe trimmed skb. Returns NULL on error.
   *
   * If the skb has data beyond the given transport length, then a
   * trimmed & cloned skb is checked and returned.
   *
   * Caller needs to set the skb transport header and free any returned skb if it
   * differs from the provided skb.
   */
  struct sk_buff *skb_checksum_trimmed(struct sk_buff *skb,
  				     unsigned int transport_len,
  				     __sum16(*skb_chkf)(struct sk_buff *skb))
  {
  	struct sk_buff *skb_chk;
  	unsigned int offset = skb_transport_offset(skb);
  	__sum16 ret;
  
  	skb_chk = skb_checksum_maybe_trim(skb, transport_len);
  	if (!skb_chk)
  		goto err;
  
  	if (!pskb_may_pull(skb_chk, offset))
  		goto err;
  
  	skb_pull_rcsum(skb_chk, offset);
  	ret = skb_chkf(skb_chk);
  	skb_push_rcsum(skb_chk, offset);
  
  	if (ret)
  		goto err;
  
  	return skb_chk;
  
  err:
  	if (skb_chk && skb_chk != skb)
  		kfree_skb(skb_chk);
  
  	return NULL;
  
  }
  EXPORT_SYMBOL(skb_checksum_trimmed);
  
  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)
  {
  	struct skb_shared_info *to_shinfo, *from_shinfo;
  	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;
  	}
  
  	to_shinfo = skb_shinfo(to);
  	from_shinfo = skb_shinfo(from);
  	if (to_shinfo->frag_list || from_shinfo->frag_list)
  		return false;
  	if (skb_zcopy(to) || skb_zcopy(from))
  		return false;
  
  	if (skb_headlen(from) != 0) {
  		struct page *page;
  		unsigned int offset;
  
  		if (to_shinfo->nr_frags +
  		    from_shinfo->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, to_shinfo->nr_frags,
  				   page, offset, skb_headlen(from));
  		*fragstolen = true;
  	} else {
  		if (to_shinfo->nr_frags +
  		    from_shinfo->nr_frags > MAX_SKB_FRAGS)
  			return false;
  
  		delta = from->truesize - SKB_TRUESIZE(skb_end_offset(from));
  	}
  
  	WARN_ON_ONCE(delta < len);
  
  	memcpy(to_shinfo->frags + to_shinfo->nr_frags,
  	       from_shinfo->frags,
  	       from_shinfo->nr_frags * sizeof(skb_frag_t));
  	to_shinfo->nr_frags += from_shinfo->nr_frags;
  
  	if (!skb_cloned(from))
  		from_shinfo->nr_frags = 0;
  
  	/* if the skb is not cloned this does nothing
  	 * since we set nr_frags to 0.
  	 */
  	for (i = 0; i < from_shinfo->nr_frags; i++)
  		__skb_frag_ref(&from_shinfo->frags[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)
  {
  	skb->pkt_type = PACKET_HOST;
  	skb->skb_iif = 0;
  	skb->ignore_df = 0;
  	skb_dst_drop(skb);
  	secpath_reset(skb);
  	nf_reset(skb);
  	nf_reset_trace(skb);
  
  #ifdef CONFIG_NET_SWITCHDEV
  	skb->offload_fwd_mark = 0;
  	skb->offload_mr_fwd_mark = 0;
  #endif
  
  	if (!xnet)
  		return;
  
  	ipvs_reset(skb);
  	skb->mark = 0;
  	skb->tstamp = 0;
  }
  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.
   */
  static 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);
  	} else if (unlikely(skb_is_gso_sctp(skb))) {
  		thlen = sizeof(struct sctphdr);
  	} else if (shinfo->gso_type & SKB_GSO_UDP_L4) {
  		thlen = sizeof(struct udphdr);
  	}
  	/* 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;
  }
  
  /**
   * skb_gso_network_seglen - Return length of individual segments of a gso packet
   *
   * @skb: GSO skb
   *
   * skb_gso_network_seglen is used to determine the real size of the
   * individual segments, including Layer3 (IP, IPv6) and L4 headers (TCP/UDP).
   *
   * The MAC/L2 header is not accounted for.
   */
  static unsigned int skb_gso_network_seglen(const struct sk_buff *skb)
  {
  	unsigned int hdr_len = skb_transport_header(skb) -
  			       skb_network_header(skb);
  
  	return hdr_len + skb_gso_transport_seglen(skb);
  }
  
  /**
   * skb_gso_mac_seglen - Return length of individual segments of a gso packet
   *
   * @skb: GSO skb
   *
   * skb_gso_mac_seglen is used to determine the real size of the
   * individual segments, including MAC/L2, Layer3 (IP, IPv6) and L4
   * headers (TCP/UDP).
   */
  static unsigned int skb_gso_mac_seglen(const struct sk_buff *skb)
  {
  	unsigned int hdr_len = skb_transport_header(skb) - skb_mac_header(skb);
  
  	return hdr_len + skb_gso_transport_seglen(skb);
  }
  
  /**
   * skb_gso_size_check - check the skb size, considering GSO_BY_FRAGS
   *
   * There are a couple of instances where we have a GSO skb, and we
   * want to determine what size it would be after it is segmented.
   *
   * We might want to check:
   * -    L3+L4+payload size (e.g. IP forwarding)
   * - L2+L3+L4+payload size (e.g. sanity check before passing to driver)
   *
   * This is a helper to do that correctly considering GSO_BY_FRAGS.
   *
   * @seg_len: The segmented length (from skb_gso_*_seglen). In the
   *           GSO_BY_FRAGS case this will be [header sizes + GSO_BY_FRAGS].
   *
   * @max_len: The maximum permissible length.
   *
   * Returns true if the segmented length <= max length.
   */
  static inline bool skb_gso_size_check(const struct sk_buff *skb,
  				      unsigned int seg_len,
  				      unsigned int max_len) {
  	const struct skb_shared_info *shinfo = skb_shinfo(skb);
  	const struct sk_buff *iter;
  
  	if (shinfo->gso_size != GSO_BY_FRAGS)
  		return seg_len <= max_len;
  
  	/* Undo this so we can re-use header sizes */
  	seg_len -= GSO_BY_FRAGS;
  
  	skb_walk_frags(skb, iter) {
  		if (seg_len + skb_headlen(iter) > max_len)
  			return false;
  	}
  
  	return true;
  }
  
  /**
   * skb_gso_validate_network_len - Will a split GSO skb fit into a given MTU?
   *
   * @skb: GSO skb
   * @mtu: MTU to validate against
   *
   * skb_gso_validate_network_len validates if a given skb will fit a
   * wanted MTU once split. It considers L3 headers, L4 headers, and the
   * payload.
   */
  bool skb_gso_validate_network_len(const struct sk_buff *skb, unsigned int mtu)
  {
  	return skb_gso_size_check(skb, skb_gso_network_seglen(skb), mtu);
  }
  EXPORT_SYMBOL_GPL(skb_gso_validate_network_len);
  
  /**
   * skb_gso_validate_mac_len - Will a split GSO skb fit in a given length?
   *
   * @skb: GSO skb
   * @len: length to validate against
   *
   * skb_gso_validate_mac_len validates if a given skb will fit a wanted
   * length once split, including L2, L3 and L4 headers and the payload.
   */
  bool skb_gso_validate_mac_len(const struct sk_buff *skb, unsigned int len)
  {
  	return skb_gso_size_check(skb, skb_gso_mac_seglen(skb), len);
  }
  EXPORT_SYMBOL_GPL(skb_gso_validate_mac_len);
  
  static struct sk_buff *skb_reorder_vlan_header(struct sk_buff *skb)
  {
  	int mac_len, meta_len;
  	void *meta;
  
  	if (skb_cow(skb, skb_headroom(skb)) < 0) {
  		kfree_skb(skb);
  		return NULL;
  	}
  
  	mac_len = skb->data - skb_mac_header(skb);
  	if (likely(mac_len > VLAN_HLEN + ETH_TLEN)) {
  		memmove(skb_mac_header(skb) + VLAN_HLEN, skb_mac_header(skb),
  			mac_len - VLAN_HLEN - ETH_TLEN);
  	}
  
  	meta_len = skb_metadata_len(skb);
  	if (meta_len) {
  		meta = skb_metadata_end(skb) - meta_len;
  		memmove(meta + VLAN_HLEN, meta, meta_len);
  	}
  
  	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(skb_vlan_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.
   * expects a non skb_vlan_tag_present skb with a vlan tag payload
   */
  int __skb_vlan_pop(struct sk_buff *skb, u16 *vlan_tci)
  {
  	struct vlan_hdr *vhdr;
  	int offset = skb->data - skb_mac_header(skb);
  	int err;
  
  	if (WARN_ONCE(offset,
  		      "__skb_vlan_pop got skb with skb->data not at mac header (offset %d)\n",
  		      offset)) {
  		return -EINVAL;
  	}
  
  	err = skb_ensure_writable(skb, VLAN_ETH_HLEN);
  	if (unlikely(err))
  		return err;
  
  	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);
  
  	return err;
  }
  EXPORT_SYMBOL(__skb_vlan_pop);
  
  /* Pop a vlan tag either from hwaccel or from payload.
   * Expects skb->data at mac header.
   */
  int skb_vlan_pop(struct sk_buff *skb)
  {
  	u16 vlan_tci;
  	__be16 vlan_proto;
  	int err;
  
  	if (likely(skb_vlan_tag_present(skb))) {
  		skb->vlan_tci = 0;
  	} else {
  		if (unlikely(!eth_type_vlan(skb->protocol)))
  			return 0;
  
  		err = __skb_vlan_pop(skb, &vlan_tci);
  		if (err)
  			return err;
  	}
  	/* move next vlan tag to hw accel tag */
  	if (likely(!eth_type_vlan(skb->protocol)))
  		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);
  
  /* Push a vlan tag either into hwaccel or into payload (if hwaccel tag present).
   * Expects skb->data at mac header.
   */
  int skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci)
  {
  	if (skb_vlan_tag_present(skb)) {
  		int offset = skb->data - skb_mac_header(skb);
  		int err;
  
  		if (WARN_ONCE(offset,
  			      "skb_vlan_push got skb with skb->data not at mac header (offset %d)\n",
  			      offset)) {
  			return -EINVAL;
  		}
  
  		err = __vlan_insert_tag(skb, skb->vlan_proto,
  					skb_vlan_tag_get(skb));
  		if (err)
  			return err;
  
  		skb->protocol = skb->vlan_proto;
  		skb->mac_len += VLAN_HLEN;
  
  		skb_postpush_rcsum(skb, skb->data + (2 * ETH_ALEN), VLAN_HLEN);
  	}
  	__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;
  	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;
  
  	*errcode = -ENOBUFS;
  	skb = alloc_skb(header_len, gfp_mask);
  	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_DIRECT_RECLAIM) |
  						   __GFP_COMP |
  						   __GFP_NOWARN,
  						   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);
  
  /* carve out the first off bytes from skb when off < headlen */
  static int pskb_carve_inside_header(struct sk_buff *skb, const u32 off,
  				    const int headlen, gfp_t gfp_mask)
  {
  	int i;
  	int size = skb_end_offset(skb);
  	int new_hlen = headlen - off;
  	u8 *data;
  
  	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)
  		return -ENOMEM;
  
  	size = SKB_WITH_OVERHEAD(ksize(data));
  
  	/* Copy real data, and all frags */
  	skb_copy_from_linear_data_offset(skb, off, data, new_hlen);
  	skb->len -= off;
  
  	memcpy((struct skb_shared_info *)(data + size),
  	       skb_shinfo(skb),
  	       offsetof(struct skb_shared_info,
  			frags[skb_shinfo(skb)->nr_frags]));
  	if (skb_cloned(skb)) {
  		/* drop the old head gracefully */
  		if (skb_orphan_frags(skb, gfp_mask)) {
  			kfree(data);
  			return -ENOMEM;
  		}
  		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 {
  		/* we can reuse existing recount- all we did was
  		 * relocate values
  		 */
  		skb_free_head(skb);
  	}
  
  	skb->head = data;
  	skb->data = data;
  	skb->head_frag = 0;
  #ifdef NET_SKBUFF_DATA_USES_OFFSET
  	skb->end = size;
  #else
  	skb->end = skb->head + size;
  #endif
  	skb_set_tail_pointer(skb, skb_headlen(skb));
  	skb_headers_offset_update(skb, 0);
  	skb->cloned = 0;
  	skb->hdr_len = 0;
  	skb->nohdr = 0;
  	atomic_set(&skb_shinfo(skb)->dataref, 1);
  
  	return 0;
  }
  
  static int pskb_carve(struct sk_buff *skb, const u32 off, gfp_t gfp);
  
  /* carve out the first eat bytes from skb's frag_list. May recurse into
   * pskb_carve()
   */
  static int pskb_carve_frag_list(struct sk_buff *skb,
  				struct skb_shared_info *shinfo, int eat,
  				gfp_t gfp_mask)
  {
  	struct sk_buff *list = shinfo->frag_list;
  	struct sk_buff *clone = NULL;
  	struct sk_buff *insp = NULL;
  
  	do {
  		if (!list) {
  			pr_err("Not enough bytes to eat. Want %d\n", eat);
  			return -EFAULT;
  		}
  		if (list->len <= eat) {
  			/* Eaten as whole. */
  			eat -= list->len;
  			list = list->next;
  			insp = list;
  		} else {
  			/* Eaten partially. */
  			if (skb_shared(list)) {
  				clone = skb_clone(list, gfp_mask);
  				if (!clone)
  					return -ENOMEM;
  				insp = list->next;
  				list = clone;
  			} else {
  				/* This may be pulled without problems. */
  				insp = list;
  			}
  			if (pskb_carve(list, eat, gfp_mask) < 0) {
  				kfree_skb(clone);
  				return -ENOMEM;
  			}
  			break;
  		}
  	} while (eat);
  
  	/* Free pulled out fragments. */
  	while ((list = shinfo->frag_list) != insp) {
  		shinfo->frag_list = list->next;
  		kfree_skb(list);
  	}
  	/* And insert new clone at head. */
  	if (clone) {
  		clone->next = list;
  		shinfo->frag_list = clone;
  	}
  	return 0;
  }
  
  /* carve off first len bytes from skb. Split line (off) is in the
   * non-linear part of skb
   */
  static int pskb_carve_inside_nonlinear(struct sk_buff *skb, const u32 off,
  				       int pos, gfp_t gfp_mask)
  {
  	int i, k = 0;
  	int size = skb_end_offset(skb);
  	u8 *data;
  	const int nfrags = skb_shinfo(skb)->nr_frags;
  	struct skb_shared_info *shinfo;
  
  	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)
  		return -ENOMEM;
  
  	size = SKB_WITH_OVERHEAD(ksize(data));
  
  	memcpy((struct skb_shared_info *)(data + size),
  	       skb_shinfo(skb), offsetof(struct skb_shared_info,
  					 frags[skb_shinfo(skb)->nr_frags]));
  	if (skb_orphan_frags(skb, gfp_mask)) {
  		kfree(data);
  		return -ENOMEM;
  	}
  	shinfo = (struct skb_shared_info *)(data + size);
  	for (i = 0; i < nfrags; i++) {
  		int fsize = skb_frag_size(&skb_shinfo(skb)->frags[i]);
  
  		if (pos + fsize > off) {
  			shinfo->frags[k] = skb_shinfo(skb)->frags[i];
  
  			if (pos < off) {
  				/* 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.
  				 */
  				shinfo->frags[0].page_offset += off - pos;
  				skb_frag_size_sub(&shinfo->frags[0], off - pos);
  			}
  			skb_frag_ref(skb, i);
  			k++;
  		}
  		pos += fsize;
  	}
  	shinfo->nr_frags = k;
  	if (skb_has_frag_list(skb))
  		skb_clone_fraglist(skb);
  
  	if (k == 0) {
  		/* split line is in frag list */
  		pskb_carve_frag_list(skb, shinfo, off - pos, gfp_mask);
  	}
  	skb_release_data(skb);
  
  	skb->head = data;
  	skb->head_frag = 0;
  	skb->data = data;
  #ifdef NET_SKBUFF_DATA_USES_OFFSET
  	skb->end = size;
  #else
  	skb->end = skb->head + size;
  #endif
  	skb_reset_tail_pointer(skb);
  	skb_headers_offset_update(skb, 0);
  	skb->cloned   = 0;
  	skb->hdr_len  = 0;
  	skb->nohdr    = 0;
  	skb->len -= off;
  	skb->data_len = skb->len;
  	atomic_set(&skb_shinfo(skb)->dataref, 1);
  	return 0;
  }
  
  /* remove len bytes from the beginning of the skb */
  static int pskb_carve(struct sk_buff *skb, const u32 len, gfp_t gfp)
  {
  	int headlen = skb_headlen(skb);
  
  	if (len < headlen)
  		return pskb_carve_inside_header(skb, len, headlen, gfp);
  	else
  		return pskb_carve_inside_nonlinear(skb, len, headlen, gfp);
  }
  
  /* Extract to_copy bytes starting at off from skb, and return this in
   * a new skb
   */
  struct sk_buff *pskb_extract(struct sk_buff *skb, int off,
  			     int to_copy, gfp_t gfp)
  {
  	struct sk_buff  *clone = skb_clone(skb, gfp);
  
  	if (!clone)
  		return NULL;
  
  	if (pskb_carve(clone, off, gfp) < 0 ||
  	    pskb_trim(clone, to_copy)) {
  		kfree_skb(clone);
  		return NULL;
  	}
  	return clone;
  }
  EXPORT_SYMBOL(pskb_extract);
  
  /**
   * skb_condense - try to get rid of fragments/frag_list if possible
   * @skb: buffer
   *
   * Can be used to save memory before skb is added to a busy queue.
   * If packet has bytes in frags and enough tail room in skb->head,
   * pull all of them, so that we can free the frags right now and adjust
   * truesize.
   * Notes:
   *	We do not reallocate skb->head thus can not fail.
   *	Caller must re-evaluate skb->truesize if needed.
   */
  void skb_condense(struct sk_buff *skb)
  {
  	if (skb->data_len) {
  		if (skb->data_len > skb->end - skb->tail ||
  		    skb_cloned(skb))
  			return;
  
  		/* Nice, we can free page frag(s) right now */
  		__pskb_pull_tail(skb, skb->data_len);
  	}
  	/* At this point, skb->truesize might be over estimated,
  	 * because skb had a fragment, and fragments do not tell
  	 * their truesize.
  	 * When we pulled its content into skb->head, fragment
  	 * was freed, but __pskb_pull_tail() could not possibly
  	 * adjust skb->truesize, not knowing the frag truesize.
  	 */
  	skb->truesize = SKB_TRUESIZE(skb_end_offset(skb));
  }
  