text: /*
   * net/tipc/msg.c: TIPC message header routines
   *
   * Copyright (c) 2000-2006, 2014-2015, Ericsson AB
   * Copyright (c) 2005, 2010-2011, Wind River Systems
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are met:
   *
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. Neither the names of the copyright holders nor the names of its
   *    contributors may be used to endorse or promote products derived from
   *    this software without specific prior written permission.
   *
   * Alternatively, this software may be distributed under the terms of the
   * GNU General Public License ("GPL") version 2 as published by the Free
   * Software Foundation.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
   * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   * POSSIBILITY OF SUCH DAMAGE.
   */
  
  #include <net/sock.h>
  #include "core.h"
  #include "msg.h"
  #include "addr.h"
  #include "name_table.h"
  #include "crypto.h"
  
  #define MAX_FORWARD_SIZE 1024
  #ifdef CONFIG_TIPC_CRYPTO
  #define BUF_HEADROOM ALIGN(((LL_MAX_HEADER + 48) + EHDR_MAX_SIZE), 16)
  #define BUF_OVERHEAD (BUF_HEADROOM + TIPC_AES_GCM_TAG_SIZE)
  #else
  #define BUF_HEADROOM (LL_MAX_HEADER + 48)
  #define BUF_OVERHEAD BUF_HEADROOM
  #endif
  
  const int one_page_mtu = PAGE_SIZE - SKB_DATA_ALIGN(BUF_OVERHEAD) -
  			 SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
  
  static unsigned int align(unsigned int i)
  {
  	return (i + 3) & ~3u;
  }
  
  /**
   * tipc_buf_acquire - creates a TIPC message buffer
   * @size: message size (including TIPC header)
   * @gfp: memory allocation flags
   *
   * Return: a new buffer with data pointers set to the specified size.
   *
   * NOTE:
   * Headroom is reserved to allow prepending of a data link header.
   * There may also be unrequested tailroom present at the buffer's end.
   */
  struct sk_buff *tipc_buf_acquire(u32 size, gfp_t gfp)
  {
  	struct sk_buff *skb;
  
  	skb = alloc_skb_fclone(BUF_OVERHEAD + size, gfp);
  	if (skb) {
  		skb_reserve(skb, BUF_HEADROOM);
  		skb_put(skb, size);
  		skb->next = NULL;
  	}
  	return skb;
  }
  
  void tipc_msg_init(u32 own_node, struct tipc_msg *m, u32 user, u32 type,
  		   u32 hsize, u32 dnode)
  {
  	memset(m, 0, hsize);
  	msg_set_version(m);
  	msg_set_user(m, user);
  	msg_set_hdr_sz(m, hsize);
  	msg_set_size(m, hsize);
  	msg_set_prevnode(m, own_node);
  	msg_set_type(m, type);
  	if (hsize > SHORT_H_SIZE) {
  		msg_set_orignode(m, own_node);
  		msg_set_destnode(m, dnode);
  	}
  }
  
  struct sk_buff *tipc_msg_create(uint user, uint type,
  				uint hdr_sz, uint data_sz, u32 dnode,
  				u32 onode, u32 dport, u32 oport, int errcode)
  {
  	struct tipc_msg *msg;
  	struct sk_buff *buf;
  
  	buf = tipc_buf_acquire(hdr_sz + data_sz, GFP_ATOMIC);
  	if (unlikely(!buf))
  		return NULL;
  
  	msg = buf_msg(buf);
  	tipc_msg_init(onode, msg, user, type, hdr_sz, dnode);
  	msg_set_size(msg, hdr_sz + data_sz);
  	msg_set_origport(msg, oport);
  	msg_set_destport(msg, dport);
  	msg_set_errcode(msg, errcode);
  	return buf;
  }
  
  /* tipc_buf_append(): Append a buffer to the fragment list of another buffer
   * @*headbuf: in:  NULL for first frag, otherwise value returned from prev call
   *            out: set when successful non-complete reassembly, otherwise NULL
   * @*buf:     in:  the buffer to append. Always defined
   *            out: head buf after successful complete reassembly, otherwise NULL
   * Returns 1 when reassembly complete, otherwise 0
   */
  int tipc_buf_append(struct sk_buff **headbuf, struct sk_buff **buf)
  {
  	struct sk_buff *head = *headbuf;
  	struct sk_buff *frag = *buf;
  	struct sk_buff *tail = NULL;
  	struct tipc_msg *msg;
  	u32 fragid;
  	int delta;
  	bool headstolen;
  
  	if (!frag)
  		goto err;
  
  	msg = buf_msg(frag);
  	fragid = msg_type(msg);
  	frag->next = NULL;
  	skb_pull(frag, msg_hdr_sz(msg));
  
  	if (fragid == FIRST_FRAGMENT) {
  		if (unlikely(head))
  			goto err;
  		*buf = NULL;
  		if (skb_has_frag_list(frag) && __skb_linearize(frag))
  			goto err;
  		frag = skb_unshare(frag, GFP_ATOMIC);
  		if (unlikely(!frag))
  			goto err;
  		head = *headbuf = frag;
  		TIPC_SKB_CB(head)->tail = NULL;
  		return 0;
  	}
  
  	if (!head)
  		goto err;
  
  	if (skb_try_coalesce(head, frag, &headstolen, &delta)) {
  		kfree_skb_partial(frag, headstolen);
  	} else {
  		tail = TIPC_SKB_CB(head)->tail;
  		if (!skb_has_frag_list(head))
  			skb_shinfo(head)->frag_list = frag;
  		else
  			tail->next = frag;
  		head->truesize += frag->truesize;
  		head->data_len += frag->len;
  		head->len += frag->len;
  		TIPC_SKB_CB(head)->tail = frag;
  	}
  
  	if (fragid == LAST_FRAGMENT) {
  		TIPC_SKB_CB(head)->validated = 0;
  		if (unlikely(!tipc_msg_validate(&head)))
  			goto err;
  		*buf = head;
  		TIPC_SKB_CB(head)->tail = NULL;
  		*headbuf = NULL;
  		return 1;
  	}
  	*buf = NULL;
  	return 0;
  err:
  	kfree_skb(*buf);
  	kfree_skb(*headbuf);
  	*buf = *headbuf = NULL;
  	return 0;
  }
  
  /**
   * tipc_msg_append(): Append data to tail of an existing buffer queue
   * @_hdr: header to be used
   * @m: the data to be appended
   * @mss: max allowable size of buffer
   * @dlen: size of data to be appended
   * @txq: queue to append to
   *
   * Return: the number of 1k blocks appended or errno value
   */
  int tipc_msg_append(struct tipc_msg *_hdr, struct msghdr *m, int dlen,
  		    int mss, struct sk_buff_head *txq)
  {
  	struct sk_buff *skb;
  	int accounted, total, curr;
  	int mlen, cpy, rem = dlen;
  	struct tipc_msg *hdr;
  
  	skb = skb_peek_tail(txq);
  	accounted = skb ? msg_blocks(buf_msg(skb)) : 0;
  	total = accounted;
  
  	do {
  		if (!skb || skb->len >= mss) {
  			skb = tipc_buf_acquire(mss, GFP_KERNEL);
  			if (unlikely(!skb))
  				return -ENOMEM;
  			skb_orphan(skb);
  			skb_trim(skb, MIN_H_SIZE);
  			hdr = buf_msg(skb);
  			skb_copy_to_linear_data(skb, _hdr, MIN_H_SIZE);
  			msg_set_hdr_sz(hdr, MIN_H_SIZE);
  			msg_set_size(hdr, MIN_H_SIZE);
  			__skb_queue_tail(txq, skb);
  			total += 1;
  		}
  		hdr = buf_msg(skb);
  		curr = msg_blocks(hdr);
  		mlen = msg_size(hdr);
  		cpy = min_t(size_t, rem, mss - mlen);
  		if (cpy != copy_from_iter(skb->data + mlen, cpy, &m->msg_iter))
  			return -EFAULT;
  		msg_set_size(hdr, mlen + cpy);
  		skb_put(skb, cpy);
  		rem -= cpy;
  		total += msg_blocks(hdr) - curr;
  	} while (rem > 0);
  	return total - accounted;
  }
  
  /* tipc_msg_validate - validate basic format of received message
   *
   * This routine ensures a TIPC message has an acceptable header, and at least
   * as much data as the header indicates it should.  The routine also ensures
   * that the entire message header is stored in the main fragment of the message
   * buffer, to simplify future access to message header fields.
   *
   * Note: Having extra info present in the message header or data areas is OK.
   * TIPC will ignore the excess, under the assumption that it is optional info
   * introduced by a later release of the protocol.
   */
  bool tipc_msg_validate(struct sk_buff **_skb)
  {
  	struct sk_buff *skb = *_skb;
  	struct tipc_msg *hdr;
  	int msz, hsz;
  
  	/* Ensure that flow control ratio condition is satisfied */
  	if (unlikely(skb->truesize / buf_roundup_len(skb) >= 4)) {
  		skb = skb_copy_expand(skb, BUF_HEADROOM, 0, GFP_ATOMIC);
  		if (!skb)
  			return false;
  		kfree_skb(*_skb);
  		*_skb = skb;
  	}
  
  	if (unlikely(TIPC_SKB_CB(skb)->validated))
  		return true;
  
  	if (unlikely(!pskb_may_pull(skb, MIN_H_SIZE)))
  		return false;
  
  	hsz = msg_hdr_sz(buf_msg(skb));
  	if (unlikely(hsz < MIN_H_SIZE) || (hsz > MAX_H_SIZE))
  		return false;
  	if (unlikely(!pskb_may_pull(skb, hsz)))
  		return false;
  
  	hdr = buf_msg(skb);
  	if (unlikely(msg_version(hdr) != TIPC_VERSION))
  		return false;
  
  	msz = msg_size(hdr);
  	if (unlikely(msz < hsz))
  		return false;
  	if (unlikely((msz - hsz) > TIPC_MAX_USER_MSG_SIZE))
  		return false;
  	if (unlikely(skb->len < msz))
  		return false;
  
  	TIPC_SKB_CB(skb)->validated = 1;
  	return true;
  }
  
  /**
   * tipc_msg_fragment - build a fragment skb list for TIPC message
   *
   * @skb: TIPC message skb
   * @hdr: internal msg header to be put on the top of the fragments
   * @pktmax: max size of a fragment incl. the header
   * @frags: returned fragment skb list
   *
   * Return: 0 if the fragmentation is successful, otherwise: -EINVAL
   * or -ENOMEM
   */
  int tipc_msg_fragment(struct sk_buff *skb, const struct tipc_msg *hdr,
  		      int pktmax, struct sk_buff_head *frags)
  {
  	int pktno, nof_fragms, dsz, dmax, eat;
  	struct tipc_msg *_hdr;
  	struct sk_buff *_skb;
  	u8 *data;
  
  	/* Non-linear buffer? */
  	if (skb_linearize(skb))
  		return -ENOMEM;
  
  	data = (u8 *)skb->data;
  	dsz = msg_size(buf_msg(skb));
  	dmax = pktmax - INT_H_SIZE;
  	if (dsz <= dmax || !dmax)
  		return -EINVAL;
  
  	nof_fragms = dsz / dmax + 1;
  	for (pktno = 1; pktno <= nof_fragms; pktno++) {
  		if (pktno < nof_fragms)
  			eat = dmax;
  		else
  			eat = dsz % dmax;
  		/* Allocate a new fragment */
  		_skb = tipc_buf_acquire(INT_H_SIZE + eat, GFP_ATOMIC);
  		if (!_skb)
  			goto error;
  		skb_orphan(_skb);
  		__skb_queue_tail(frags, _skb);
  		/* Copy header & data to the fragment */
  		skb_copy_to_linear_data(_skb, hdr, INT_H_SIZE);
  		skb_copy_to_linear_data_offset(_skb, INT_H_SIZE, data, eat);
  		data += eat;
  		/* Update the fragment's header */
  		_hdr = buf_msg(_skb);
  		msg_set_fragm_no(_hdr, pktno);
  		msg_set_nof_fragms(_hdr, nof_fragms);
  		msg_set_size(_hdr, INT_H_SIZE + eat);
  	}
  	return 0;
  
  error:
  	__skb_queue_purge(frags);
  	__skb_queue_head_init(frags);
  	return -ENOMEM;
  }
  
  /**
   * tipc_msg_build - create buffer chain containing specified header and data
   * @mhdr: Message header, to be prepended to data
   * @m: User message
   * @offset: buffer offset for fragmented messages (FIXME)
   * @dsz: Total length of user data
   * @pktmax: Max packet size that can be used
   * @list: Buffer or chain of buffers to be returned to caller
   *
   * Note that the recursive call we are making here is safe, since it can
   * logically go only one further level down.
   *
   * Return: message data size or errno: -ENOMEM, -EFAULT
   */
  int tipc_msg_build(struct tipc_msg *mhdr, struct msghdr *m, int offset,
  		   int dsz, int pktmax, struct sk_buff_head *list)
  {
  	int mhsz = msg_hdr_sz(mhdr);
  	struct tipc_msg pkthdr;
  	int msz = mhsz + dsz;
  	int pktrem = pktmax;
  	struct sk_buff *skb;
  	int drem = dsz;
  	int pktno = 1;
  	char *pktpos;
  	int pktsz;
  	int rc;
  
  	msg_set_size(mhdr, msz);
  
  	/* No fragmentation needed? */
  	if (likely(msz <= pktmax)) {
  		skb = tipc_buf_acquire(msz, GFP_KERNEL);
  
  		/* Fall back to smaller MTU if node local message */
  		if (unlikely(!skb)) {
  			if (pktmax != MAX_MSG_SIZE)
  				return -ENOMEM;
  			rc = tipc_msg_build(mhdr, m, offset, dsz,
  					    one_page_mtu, list);
  			if (rc != dsz)
  				return rc;
  			if (tipc_msg_assemble(list))
  				return dsz;
  			return -ENOMEM;
  		}
  		skb_orphan(skb);
  		__skb_queue_tail(list, skb);
  		skb_copy_to_linear_data(skb, mhdr, mhsz);
  		pktpos = skb->data + mhsz;
  		if (copy_from_iter_full(pktpos, dsz, &m->msg_iter))
  			return dsz;
  		rc = -EFAULT;
  		goto error;
  	}
  
  	/* Prepare reusable fragment header */
  	tipc_msg_init(msg_prevnode(mhdr), &pkthdr, MSG_FRAGMENTER,
  		      FIRST_FRAGMENT, INT_H_SIZE, msg_destnode(mhdr));
  	msg_set_size(&pkthdr, pktmax);
  	msg_set_fragm_no(&pkthdr, pktno);
  	msg_set_importance(&pkthdr, msg_importance(mhdr));
  
  	/* Prepare first fragment */
  	skb = tipc_buf_acquire(pktmax, GFP_KERNEL);
  	if (!skb)
  		return -ENOMEM;
  	skb_orphan(skb);
  	__skb_queue_tail(list, skb);
  	pktpos = skb->data;
  	skb_copy_to_linear_data(skb, &pkthdr, INT_H_SIZE);
  	pktpos += INT_H_SIZE;
  	pktrem -= INT_H_SIZE;
  	skb_copy_to_linear_data_offset(skb, INT_H_SIZE, mhdr, mhsz);
  	pktpos += mhsz;
  	pktrem -= mhsz;
  
  	do {
  		if (drem < pktrem)
  			pktrem = drem;
  
  		if (!copy_from_iter_full(pktpos, pktrem, &m->msg_iter)) {
  			rc = -EFAULT;
  			goto error;
  		}
  		drem -= pktrem;
  
  		if (!drem)
  			break;
  
  		/* Prepare new fragment: */
  		if (drem < (pktmax - INT_H_SIZE))
  			pktsz = drem + INT_H_SIZE;
  		else
  			pktsz = pktmax;
  		skb = tipc_buf_acquire(pktsz, GFP_KERNEL);
  		if (!skb) {
  			rc = -ENOMEM;
  			goto error;
  		}
  		skb_orphan(skb);
  		__skb_queue_tail(list, skb);
  		msg_set_type(&pkthdr, FRAGMENT);
  		msg_set_size(&pkthdr, pktsz);
  		msg_set_fragm_no(&pkthdr, ++pktno);
  		skb_copy_to_linear_data(skb, &pkthdr, INT_H_SIZE);
  		pktpos = skb->data + INT_H_SIZE;
  		pktrem = pktsz - INT_H_SIZE;
  
  	} while (1);
  	msg_set_type(buf_msg(skb), LAST_FRAGMENT);
  	return dsz;
  error:
  	__skb_queue_purge(list);
  	__skb_queue_head_init(list);
  	return rc;
  }
  
  /**
   * tipc_msg_bundle - Append contents of a buffer to tail of an existing one
   * @bskb: the bundle buffer to append to
   * @msg: message to be appended
   * @max: max allowable size for the bundle buffer
   *
   * Return: "true" if bundling has been performed, otherwise "false"
   */
  static bool tipc_msg_bundle(struct sk_buff *bskb, struct tipc_msg *msg,
  			    u32 max)
  {
  	struct tipc_msg *bmsg = buf_msg(bskb);
  	u32 msz, bsz, offset, pad;
  
  	msz = msg_size(msg);
  	bsz = msg_size(bmsg);
  	offset = align(bsz);
  	pad = offset - bsz;
  
  	if (unlikely(skb_tailroom(bskb) < (pad + msz)))
  		return false;
  	if (unlikely(max < (offset + msz)))
  		return false;
  
  	skb_put(bskb, pad + msz);
  	skb_copy_to_linear_data_offset(bskb, offset, msg, msz);
  	msg_set_size(bmsg, offset + msz);
  	msg_set_msgcnt(bmsg, msg_msgcnt(bmsg) + 1);
  	return true;
  }
  
  /**
   * tipc_msg_try_bundle - Try to bundle a new message to the last one
   * @tskb: the last/target message to which the new one will be appended
   * @skb: the new message skb pointer
   * @mss: max message size (header inclusive)
   * @dnode: destination node for the message
   * @new_bundle: if this call made a new bundle or not
   *
   * Return: "true" if the new message skb is potential for bundling this time or
   * later, in the case a bundling has been done this time, the skb is consumed
   * (the skb pointer = NULL).
   * Otherwise, "false" if the skb cannot be bundled at all.
   */
  bool tipc_msg_try_bundle(struct sk_buff *tskb, struct sk_buff **skb, u32 mss,
  			 u32 dnode, bool *new_bundle)
  {
  	struct tipc_msg *msg, *inner, *outer;
  	u32 tsz;
  
  	/* First, check if the new buffer is suitable for bundling */
  	msg = buf_msg(*skb);
  	if (msg_user(msg) == MSG_FRAGMENTER)
  		return false;
  	if (msg_user(msg) == TUNNEL_PROTOCOL)
  		return false;
  	if (msg_user(msg) == BCAST_PROTOCOL)
  		return false;
  	if (mss <= INT_H_SIZE + msg_size(msg))
  		return false;
  
  	/* Ok, but the last/target buffer can be empty? */
  	if (unlikely(!tskb))
  		return true;
  
  	/* Is it a bundle already? Try to bundle the new message to it */
  	if (msg_user(buf_msg(tskb)) == MSG_BUNDLER) {
  		*new_bundle = false;
  		goto bundle;
  	}
  
  	/* Make a new bundle of the two messages if possible */
  	tsz = msg_size(buf_msg(tskb));
  	if (unlikely(mss < align(INT_H_SIZE + tsz) + msg_size(msg)))
  		return true;
  	if (unlikely(pskb_expand_head(tskb, INT_H_SIZE, mss - tsz - INT_H_SIZE,
  				      GFP_ATOMIC)))
  		return true;
  	inner = buf_msg(tskb);
  	skb_push(tskb, INT_H_SIZE);
  	outer = buf_msg(tskb);
  	tipc_msg_init(msg_prevnode(inner), outer, MSG_BUNDLER, 0, INT_H_SIZE,
  		      dnode);
  	msg_set_importance(outer, msg_importance(inner));
  	msg_set_size(outer, INT_H_SIZE + tsz);
  	msg_set_msgcnt(outer, 1);
  	*new_bundle = true;
  
  bundle:
  	if (likely(tipc_msg_bundle(tskb, msg, mss))) {
  		consume_skb(*skb);
  		*skb = NULL;
  	}
  	return true;
  }
  
  /**
   *  tipc_msg_extract(): extract bundled inner packet from buffer
   *  @skb: buffer to be extracted from.
   *  @iskb: extracted inner buffer, to be returned
   *  @pos: position in outer message of msg to be extracted.
   *  Returns position of next msg.
   *  Consumes outer buffer when last packet extracted
   *  Return: true when there is an extracted buffer, otherwise false
   */
  bool tipc_msg_extract(struct sk_buff *skb, struct sk_buff **iskb, int *pos)
  {
  	struct tipc_msg *hdr, *ihdr;
  	int imsz;
  
  	*iskb = NULL;
  	if (unlikely(skb_linearize(skb)))
  		goto none;
  
  	hdr = buf_msg(skb);
  	if (unlikely(*pos > (msg_data_sz(hdr) - MIN_H_SIZE)))
  		goto none;
  
  	ihdr = (struct tipc_msg *)(msg_data(hdr) + *pos);
  	imsz = msg_size(ihdr);
  
  	if ((*pos + imsz) > msg_data_sz(hdr))
  		goto none;
  
  	*iskb = tipc_buf_acquire(imsz, GFP_ATOMIC);
  	if (!*iskb)
  		goto none;
  
  	skb_copy_to_linear_data(*iskb, ihdr, imsz);
  	if (unlikely(!tipc_msg_validate(iskb)))
  		goto none;
  
  	*pos += align(imsz);
  	return true;
  none:
  	kfree_skb(skb);
  	kfree_skb(*iskb);
  	*iskb = NULL;
  	return false;
  }
  
  /**
   * tipc_msg_reverse(): swap source and destination addresses and add error code
   * @own_node: originating node id for reversed message
   * @skb:  buffer containing message to be reversed; will be consumed
   * @err:  error code to be set in message, if any
   * Replaces consumed buffer with new one when successful
   * Return: true if success, otherwise false
   */
  bool tipc_msg_reverse(u32 own_node,  struct sk_buff **skb, int err)
  {
  	struct sk_buff *_skb = *skb;
  	struct tipc_msg *_hdr, *hdr;
  	int hlen, dlen;
  
  	if (skb_linearize(_skb))
  		goto exit;
  	_hdr = buf_msg(_skb);
  	dlen = min_t(uint, msg_data_sz(_hdr), MAX_FORWARD_SIZE);
  	hlen = msg_hdr_sz(_hdr);
  
  	if (msg_dest_droppable(_hdr))
  		goto exit;
  	if (msg_errcode(_hdr))
  		goto exit;
  
  	/* Never return SHORT header */
  	if (hlen == SHORT_H_SIZE)
  		hlen = BASIC_H_SIZE;
  
  	/* Don't return data along with SYN+, - sender has a clone */
  	if (msg_is_syn(_hdr) && err == TIPC_ERR_OVERLOAD)
  		dlen = 0;
  
  	/* Allocate new buffer to return */
  	*skb = tipc_buf_acquire(hlen + dlen, GFP_ATOMIC);
  	if (!*skb)
  		goto exit;
  	memcpy((*skb)->data, _skb->data, msg_hdr_sz(_hdr));
  	memcpy((*skb)->data + hlen, msg_data(_hdr), dlen);
  
  	/* Build reverse header in new buffer */
  	hdr = buf_msg(*skb);
  	msg_set_hdr_sz(hdr, hlen);
  	msg_set_errcode(hdr, err);
  	msg_set_non_seq(hdr, 0);
  	msg_set_origport(hdr, msg_destport(_hdr));
  	msg_set_destport(hdr, msg_origport(_hdr));
  	msg_set_destnode(hdr, msg_prevnode(_hdr));
  	msg_set_prevnode(hdr, own_node);
  	msg_set_orignode(hdr, own_node);
  	msg_set_size(hdr, hlen + dlen);
  	skb_orphan(_skb);
  	kfree_skb(_skb);
  	return true;
  exit:
  	kfree_skb(_skb);
  	*skb = NULL;
  	return false;
  }
  
  bool tipc_msg_skb_clone(struct sk_buff_head *msg, struct sk_buff_head *cpy)
  {
  	struct sk_buff *skb, *_skb;
  
  	skb_queue_walk(msg, skb) {
  		_skb = skb_clone(skb, GFP_ATOMIC);
  		if (!_skb) {
  			__skb_queue_purge(cpy);
  			pr_err_ratelimited("Failed to clone buffer chain\n");
  			return false;
  		}
  		__skb_queue_tail(cpy, _skb);
  	}
  	return true;
  }
  
  /**
   * tipc_msg_lookup_dest(): try to find new destination for named message
   * @net: pointer to associated network namespace
   * @skb: the buffer containing the message.
   * @err: error code to be used by caller if lookup fails
   * Does not consume buffer
   * Return: true if a destination is found, false otherwise
   */
  bool tipc_msg_lookup_dest(struct net *net, struct sk_buff *skb, int *err)
  {
  	struct tipc_msg *msg = buf_msg(skb);
  	u32 dport, dnode;
  	u32 onode = tipc_own_addr(net);
  
  	if (!msg_isdata(msg))
  		return false;
  	if (!msg_named(msg))
  		return false;
  	if (msg_errcode(msg))
  		return false;
  	*err = TIPC_ERR_NO_NAME;
  	if (skb_linearize(skb))
  		return false;
  	msg = buf_msg(skb);
  	if (msg_reroute_cnt(msg))
  		return false;
  	dnode = tipc_scope2node(net, msg_lookup_scope(msg));
  	dport = tipc_nametbl_translate(net, msg_nametype(msg),
  				       msg_nameinst(msg), &dnode);
  	if (!dport)
  		return false;
  	msg_incr_reroute_cnt(msg);
  	if (dnode != onode)
  		msg_set_prevnode(msg, onode);
  	msg_set_destnode(msg, dnode);
  	msg_set_destport(msg, dport);
  	*err = TIPC_OK;
  
  	return true;
  }
  
  /* tipc_msg_assemble() - assemble chain of fragments into one message
   */
  bool tipc_msg_assemble(struct sk_buff_head *list)
  {
  	struct sk_buff *skb, *tmp = NULL;
  
  	if (skb_queue_len(list) == 1)
  		return true;
  
  	while ((skb = __skb_dequeue(list))) {
  		skb->next = NULL;
  		if (tipc_buf_append(&tmp, &skb)) {
  			__skb_queue_tail(list, skb);
  			return true;
  		}
  		if (!tmp)
  			break;
  	}
  	__skb_queue_purge(list);
  	__skb_queue_head_init(list);
  	pr_warn("Failed do assemble buffer\n");
  	return false;
  }
  
  /* tipc_msg_reassemble() - clone a buffer chain of fragments and
   *                         reassemble the clones into one message
   */
  bool tipc_msg_reassemble(struct sk_buff_head *list, struct sk_buff_head *rcvq)
  {
  	struct sk_buff *skb, *_skb;
  	struct sk_buff *frag = NULL;
  	struct sk_buff *head = NULL;
  	int hdr_len;
  
  	/* Copy header if single buffer */
  	if (skb_queue_len(list) == 1) {
  		skb = skb_peek(list);
  		hdr_len = skb_headroom(skb) + msg_hdr_sz(buf_msg(skb));
  		_skb = __pskb_copy(skb, hdr_len, GFP_ATOMIC);
  		if (!_skb)
  			return false;
  		__skb_queue_tail(rcvq, _skb);
  		return true;
  	}
  
  	/* Clone all fragments and reassemble */
  	skb_queue_walk(list, skb) {
  		frag = skb_clone(skb, GFP_ATOMIC);
  		if (!frag)
  			goto error;
  		frag->next = NULL;
  		if (tipc_buf_append(&head, &frag))
  			break;
  		if (!head)
  			goto error;
  	}
  	__skb_queue_tail(rcvq, frag);
  	return true;
  error:
  	pr_warn("Failed do clone local mcast rcv buffer\n");
  	kfree_skb(head);
  	return false;
  }
  
  bool tipc_msg_pskb_copy(u32 dst, struct sk_buff_head *msg,
  			struct sk_buff_head *cpy)
  {
  	struct sk_buff *skb, *_skb;
  
  	skb_queue_walk(msg, skb) {
  		_skb = pskb_copy(skb, GFP_ATOMIC);
  		if (!_skb) {
  			__skb_queue_purge(cpy);
  			return false;
  		}
  		msg_set_destnode(buf_msg(_skb), dst);
  		__skb_queue_tail(cpy, _skb);
  	}
  	return true;
  }
  
  /* tipc_skb_queue_sorted(); sort pkt into list according to sequence number
   * @list: list to be appended to
   * @seqno: sequence number of buffer to add
   * @skb: buffer to add
   */
  bool __tipc_skb_queue_sorted(struct sk_buff_head *list, u16 seqno,
  			     struct sk_buff *skb)
  {
  	struct sk_buff *_skb, *tmp;
  
  	if (skb_queue_empty(list) || less(seqno, buf_seqno(skb_peek(list)))) {
  		__skb_queue_head(list, skb);
  		return true;
  	}
  
  	if (more(seqno, buf_seqno(skb_peek_tail(list)))) {
  		__skb_queue_tail(list, skb);
  		return true;
  	}
  
  	skb_queue_walk_safe(list, _skb, tmp) {
  		if (more(seqno, buf_seqno(_skb)))
  			continue;
  		if (seqno == buf_seqno(_skb))
  			break;
  		__skb_queue_before(list, _skb, skb);
  		return true;
  	}
  	kfree_skb(skb);
  	return false;
  }
  
  void tipc_skb_reject(struct net *net, int err, struct sk_buff *skb,
  		     struct sk_buff_head *xmitq)
  {
  	if (tipc_msg_reverse(tipc_own_addr(net), &skb, err))
  		__skb_queue_tail(xmitq, skb);
  }
  