src/vlib/buffer_funcs.h

/*
 * Copyright (c) 2015 Cisco and/or its affiliates.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * buffer_funcs.h: VLIB buffer related functions/inlines
 *
 * Copyright (c) 2008 Eliot Dresselhaus
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 *  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 *  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 *  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
 *  LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 *  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 *  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

#ifndef included_vlib_buffer_funcs_h
#define included_vlib_buffer_funcs_h

#include <vppinfra/hash.h>
#include <vppinfra/fifo.h>

/** \file
    vlib buffer access methods.
*/


/** \brief Translate buffer index into buffer pointer

    @param vm - (vlib_main_t *) vlib main data structure pointer
    @param buffer_index - (u32) buffer index
    @return - (vlib_buffer_t *) buffer pointer
*/
always_inline vlib_buffer_t *
vlib_get_buffer (vlib_main_t * vm, u32 buffer_index)
{
  vlib_buffer_main_t *bm = vm->buffer_main;
  uword offset = ((uword) buffer_index) << CLIB_LOG2_CACHE_LINE_BYTES;
  ASSERT (offset < bm->buffer_mem_size);

  return uword_to_pointer (bm->buffer_mem_start + offset, void *);
}

static_always_inline void
vlib_buffer_copy_indices (u32 * dst, u32 * src, u32 n_indices)
{
  clib_memcpy_fast (dst, src, n_indices * sizeof (u32));
}

static_always_inline void
vlib_buffer_copy_template (vlib_buffer_t * b, vlib_buffer_t * bt)
{
  clib_memcpy_fast (b, bt, STRUCT_OFFSET_OF (vlib_buffer_t, template_end));
}

/** \brief Translate array of buffer indices into buffer pointers with offset

    @param vm - (vlib_main_t *) vlib main data structure pointer
    @param bi - (u32 *) array of buffer indices
    @param b - (void **) array to store buffer pointers
    @param count - (uword) number of elements
    @param offset - (i32) offset applied to each pointer
*/
static_always_inline void
vlib_get_buffers_with_offset (vlib_main_t * vm, u32 * bi, void **b, int count,
			      i32 offset)
{
  uword buffer_mem_start = vm->buffer_main->buffer_mem_start;
#ifdef CLIB_HAVE_VEC256
  u64x4 off = u64x4_splat (buffer_mem_start + offset);
  /* if count is not const, compiler will not unroll while loop
     se we maintain two-in-parallel variant */
  while (count >= 8)
    {
      u64x4 b0 = u32x4_extend_to_u64x4 (u32x4_load_unaligned (bi));
      u64x4 b1 = u32x4_extend_to_u64x4 (u32x4_load_unaligned (bi + 4));
      /* shift and add to get vlib_buffer_t pointer */
      u64x4_store_unaligned ((b0 << CLIB_LOG2_CACHE_LINE_BYTES) + off, b);
      u64x4_store_unaligned ((b1 << CLIB_LOG2_CACHE_LINE_BYTES) + off, b + 4);
      b += 8;
      bi += 8;
      count -= 8;
    }
#endif
  while (count >= 4)
    {
#ifdef CLIB_HAVE_VEC256
      u64x4 b0 = u32x4_extend_to_u64x4 (u32x4_load_unaligned (bi));
      /* shift and add to get vlib_buffer_t pointer */
      u64x4_store_unaligned ((b0 << CLIB_LOG2_CACHE_LINE_BYTES) + off, b);
#elif defined (CLIB_HAVE_VEC128)
      u64x2 off = u64x2_splat (buffer_mem_start + offset);
      u32x4 bi4 = u32x4_load_unaligned (bi);
      u64x2 b0 = u32x4_extend_to_u64x2 ((u32x4) bi4);
#if defined (__aarch64__)
      u64x2 b1 = u32x4_extend_to_u64x2_high ((u32x4) bi4);
#else
      bi4 = u32x4_shuffle (bi4, 2, 3, 0, 1);
      u64x2 b1 = u32x4_extend_to_u64x2 ((u32x4) bi4);
#endif
      u64x2_store_unaligned ((b0 << CLIB_LOG2_CACHE_LINE_BYTES) + off, b);
      u64x2_store_unaligned ((b1 << CLIB_LOG2_CACHE_LINE_BYTES) + off, b + 2);
#else
      b[0] = ((u8 *) vlib_get_buffer (vm, bi[0])) + offset;
      b[1] = ((u8 *) vlib_get_buffer (vm, bi[1])) + offset;
      b[2] = ((u8 *) vlib_get_buffer (vm, bi[2])) + offset;
      b[3] = ((u8 *) vlib_get_buffer (vm, bi[3])) + offset;
#endif
      b += 4;
      bi += 4;
      count -= 4;
    }
  while (count)
    {
      b[0] = ((u8 *) vlib_get_buffer (vm, bi[0])) + offset;
      b += 1;
      bi += 1;
      count -= 1;
    }
}

/** \brief Translate array of buffer indices into buffer pointers

    @param vm - (vlib_main_t *) vlib main data structure pointer
    @param bi - (u32 *) array of buffer indices
    @param b - (vlib_buffer_t **) array to store buffer pointers
    @param count - (uword) number of elements
*/

static_always_inline void
vlib_get_buffers (vlib_main_t * vm, u32 * bi, vlib_buffer_t ** b, int count)
{
  vlib_get_buffers_with_offset (vm, bi, (void **) b, count, 0);
}

/** \brief Translate buffer pointer into buffer index

    @param vm - (vlib_main_t *) vlib main data structure pointer
    @param p - (void *) buffer pointer
    @return - (u32) buffer index
*/

always_inline u32
vlib_get_buffer_index (vlib_main_t * vm, void *p)
{
  vlib_buffer_main_t *bm = vm->buffer_main;
  uword offset = pointer_to_uword (p) - bm->buffer_mem_start;
  ASSERT (pointer_to_uword (p) >= bm->buffer_mem_start);
  ASSERT (offset < bm->buffer_mem_size);
  ASSERT ((offset % (1 << CLIB_LOG2_CACHE_LINE_BYTES)) == 0);
  return offset >> CLIB_LOG2_CACHE_LINE_BYTES;
}

/** \brief Translate array of buffer pointers into buffer indices with offset

    @param vm - (vlib_main_t *) vlib main data structure pointer
    @param b - (void **) array of buffer pointers
    @param bi - (u32 *) array to store buffer indices
    @param count - (uword) number of elements
    @param offset - (i32) offset applied to each pointer
*/
static_always_inline void
vlib_get_buffer_indices_with_offset (vlib_main_t * vm, void **b, u32 * bi,
				     uword count, i32 offset)
{
#ifdef CLIB_HAVE_VEC256
  u32x8 mask = { 0, 2, 4, 6, 1, 3, 5, 7 };
  u64x4 off4 = u64x4_splat (vm->buffer_main->buffer_mem_start - offset);

  while (count >= 8)
    {
      /* load 4 pointers into 256-bit register */
      u64x4 v0 = u64x4_load_unaligned (b);
      u64x4 v1 = u64x4_load_unaligned (b + 4);
      u32x8 v2, v3;

      v0 -= off4;
      v1 -= off4;

      v0 >>= CLIB_LOG2_CACHE_LINE_BYTES;
      v1 >>= CLIB_LOG2_CACHE_LINE_BYTES;

      /* permute 256-bit register so lower u32s of each buffer index are
       * placed into lower 128-bits */
      v2 = u32x8_permute ((u32x8) v0, mask);
      v3 = u32x8_permute ((u32x8) v1, mask);

      /* extract lower 128-bits and save them to the array of buffer indices */
      u32x4_store_unaligned (u32x8_extract_lo (v2), bi);
      u32x4_store_unaligned (u32x8_extract_lo (v3), bi + 4);
      bi += 8;
      b += 8;
      count -= 8;
    }
#endif
  while (count >= 4)
    {
      /* equivalent non-nector implementation */
      bi[0] = vlib_get_buffer_index (vm, ((u8 *) b[0]) + offset);
      bi[1] = vlib_get_buffer_index (vm, ((u8 *) b[1]) + offset);
      bi[2] = vlib_get_buffer_index (vm, ((u8 *) b[2]) + offset);
      bi[3] = vlib_get_buffer_index (vm, ((u8 *) b[3]) + offset);
      bi += 4;
      b += 4;
      count -= 4;
    }
  while (count)
    {
      bi[0] = vlib_get_buffer_index (vm, ((u8 *) b[0]) + offset);
      bi += 1;
      b += 1;
      count -= 1;
    }
}

/** \brief Translate array of buffer pointers into buffer indices

    @param vm - (vlib_main_t *) vlib main data structure pointer
    @param b - (vlib_buffer_t **) array of buffer pointers
    @param bi - (u32 *) array to store buffer indices
    @param count - (uword) number of elements
*/
static_always_inline void
vlib_get_buffer_indices (vlib_main_t * vm, vlib_buffer_t ** b, u32 * bi,
			 uword count)
{
  vlib_get_buffer_indices_with_offset (vm, (void **) b, bi, count, 0);
}

/** \brief Get next buffer in buffer linklist, or zero for end of list.

    @param vm - (vlib_main_t *) vlib main data structure pointer
    @param b - (void *) buffer pointer
    @return - (vlib_buffer_t *) next buffer, or NULL
*/
always_inline vlib_buffer_t *
vlib_get_next_buffer (vlib_main_t * vm, vlib_buffer_t * b)
{
  return (b->flags & VLIB_BUFFER_NEXT_PRESENT
	  ? vlib_get_buffer (vm, b->next_buffer) : 0);
}

uword vlib_buffer_length_in_chain_slow_path (vlib_main_t * vm,
					     vlib_buffer_t * b_first);

/** \brief Get length in bytes of the buffer chain

    @param vm - (vlib_main_t *) vlib main data structure pointer
    @param b - (void *) buffer pointer
    @return - (uword) length of buffer chain
*/
always_inline uword
vlib_buffer_length_in_chain (vlib_main_t * vm, vlib_buffer_t * b)
{
  uword len = b->current_length;

  if (PREDICT_TRUE ((b->flags & VLIB_BUFFER_NEXT_PRESENT) == 0))
    return len;

  if (PREDICT_TRUE (b->flags & VLIB_BUFFER_TOTAL_LENGTH_VALID))
    return len + b->total_length_not_including_first_buffer;

  return vlib_buffer_length_in_chain_slow_path (vm, b);
}

/** \brief Get length in bytes of the buffer index buffer chain

    @param vm - (vlib_main_t *) vlib main data structure pointer
    @param bi - (u32) buffer index
    @return - (uword) length of buffer chain
*/
always_inline uword
vlib_buffer_index_length_in_chain (vlib_main_t * vm, u32 bi)
{
  vlib_buffer_t *b = vlib_get_buffer (vm, bi);
  return vlib_buffer_length_in_chain (vm, b);
}

/** \brief Copy buffer contents to memory

    @param vm - (vlib_main_t *) vlib main data structure pointer
    @param buffer_index - (u32) buffer index
    @param contents - (u8 *) memory, <strong>must be large enough</strong>
    @return - (uword) length of buffer chain
*/
always_inline uword
vlib_buffer_contents (vlib_main_t * vm, u32 buffer_index, u8 * contents)
{
  uword content_len = 0;
  uword l;
  vlib_buffer_t *b;

  while (1)
    {
      b = vlib_get_buffer (vm, buffer_index);
      l = b->current_length;
      clib_memcpy_fast (contents + content_len, b->data + b->current_data, l);
      content_len += l;
      if (!(b->flags & VLIB_BUFFER_NEXT_PRESENT))
	break;
      buffer_index = b->next_buffer;
    }

  return content_len;
}

always_inline uword
vlib_buffer_get_pa (vlib_main_t * vm, vlib_buffer_t * b)
{
  return vlib_physmem_get_pa (vm, b->data);
}

always_inline uword
vlib_buffer_get_current_pa (vlib_main_t * vm, vlib_buffer_t * b)
{
  return vlib_buffer_get_pa (vm, b) + b->current_data;
}

/** \brief Prefetch buffer metadata by buffer index
    The first 64 bytes of buffer contains most header information

    @param vm - (vlib_main_t *) vlib main data structure pointer
    @param bi - (u32) buffer index
    @param type - LOAD, STORE. In most cases, STORE is the right answer
*/
/* Prefetch buffer header given index. */
#define vlib_prefetch_buffer_with_index(vm,bi,type)	\
  do {							\
    vlib_buffer_t * _b = vlib_get_buffer (vm, bi);	\
    vlib_prefetch_buffer_header (_b, type);		\
  } while (0)

typedef enum
{
  /* Index is unknown. */
  VLIB_BUFFER_UNKNOWN,

  /* Index is known and free/allocated. */
  VLIB_BUFFER_KNOWN_FREE,
  VLIB_BUFFER_KNOWN_ALLOCATED,
} vlib_buffer_known_state_t;

void vlib_buffer_validate_alloc_free (vlib_main_t * vm, u32 * buffers,
				      uword n_buffers,
				      vlib_buffer_known_state_t
				      expected_state);

always_inline vlib_buffer_known_state_t
vlib_buffer_is_known (vlib_main_t * vm, u32 buffer_index)
{
  vlib_buffer_main_t *bm = vm->buffer_main;

  clib_spinlock_lock (&bm->buffer_known_hash_lockp);
  uword *p = hash_get (bm->buffer_known_hash, buffer_index);
  clib_spinlock_unlock (&bm->buffer_known_hash_lockp);
  return p ? p[0] : VLIB_BUFFER_UNKNOWN;
}

always_inline void
vlib_buffer_set_known_state (vlib_main_t * vm, u32 buffer_index,
			     vlib_buffer_known_state_t state)
{
  vlib_buffer_main_t *bm = vm->buffer_main;

  clib_spinlock_lock (&bm->buffer_known_hash_lockp);
  hash_set (bm->buffer_known_hash, buffer_index, state);
  clib_spinlock_unlock (&bm->buffer_known_hash_lockp);
}

/* Validates sanity of a single buffer.
   Returns format'ed vector with error message if any. */
u8 *vlib_validate_buffer (vlib_main_t * vm, u32 buffer_index,
			  uword follow_chain);

always_inline u32
vlib_buffer_round_size (u32 size)
{
  return round_pow2 (size, sizeof (vlib_buffer_t));
}

/** \brief Allocate buffers from specific freelist into supplied array

    @param vm - (vlib_main_t *) vlib main data structure pointer
    @param buffers - (u32 * ) buffer index array
    @param n_buffers - (u32) number of buffers requested
    @return - (u32) number of buffers actually allocated, may be
    less than the number requested or zero
*/
always_inline u32
vlib_buffer_alloc_from_free_list (vlib_main_t * vm,
				  u32 * buffers,
				  u32 n_buffers,
				  vlib_buffer_free_list_index_t index)
{
  vlib_buffer_free_list_t *fl;
  vlib_buffer_main_t *bm = vm->buffer_main;
  u32 *src;
  uword len;

  ASSERT (bm->cb.vlib_buffer_fill_free_list_cb);

  fl = pool_elt_at_index (vm->buffer_free_list_pool, index);

  len = vec_len (fl->buffers);

  if (PREDICT_FALSE (len < n_buffers))
    {
      bm->cb.vlib_buffer_fill_free_list_cb (vm, fl, n_buffers);
      if (PREDICT_FALSE ((len = vec_len (fl->buffers)) == 0))
	return 0;

      /* even if fill free list didn't manage to refill free list
         we should give what we have */
      n_buffers = clib_min (len, n_buffers);

      /* following code is intentionaly duplicated to allow compiler
         to optimize fast path when n_buffers is constant value */
      src = fl->buffers + len - n_buffers;
      vlib_buffer_copy_indices (buffers, src, n_buffers);
      _vec_len (fl->buffers) -= n_buffers;

      /* Verify that buffers are known free. */
      vlib_buffer_validate_alloc_free (vm, buffers, n_buffers,
				       VLIB_BUFFER_KNOWN_FREE);

      return n_buffers;
    }

  src = fl->buffers + len - n_buffers;
  vlib_buffer_copy_indices (buffers, src, n_buffers);
  _vec_len (fl->buffers) -= n_buffers;

  /* Verify that buffers are known free. */
  vlib_buffer_validate_alloc_free (vm, buffers, n_buffers,
				   VLIB_BUFFER_KNOWN_FREE);

  return n_buffers;
}

/** \brief Allocate buffers into supplied array

    @param vm - (vlib_main_t *) vlib main data structure pointer
    @param buffers - (u32 * ) buffer index array
    @param n_buffers - (u32) number of buffers requested
    @return - (u32) number of buffers actually allocated, may be
    less than the number requested or zero
*/
always_inline u32
vlib_buffer_alloc (vlib_main_t * vm, u32 * buffers, u32 n_buffers)
{
  return vlib_buffer_alloc_from_free_list (vm, buffers, n_buffers,
					   VLIB_BUFFER_DEFAULT_FREE_LIST_INDEX);
}

/** \brief Allocate buffers into ring

    @param vm - (vlib_main_t *) vlib main data structure pointer
    @param buffers - (u32 * ) buffer index ring
    @param start - (u32) first slot in the ring
    @param ring_size - (u32) ring size
    @param n_buffers - (u32) number of buffers requested
    @return - (u32) number of buffers actually allocated, may be
    less than the number requested or zero
*/
always_inline u32
vlib_buffer_alloc_to_ring (vlib_main_t * vm, u32 * ring, u32 start,
			   u32 ring_size, u32 n_buffers)
{
  u32 n_alloc;

  ASSERT (n_buffers <= ring_size);

  if (PREDICT_TRUE (start + n_buffers <= ring_size))
    return vlib_buffer_alloc (vm, ring + start, n_buffers);

  n_alloc = vlib_buffer_alloc (vm, ring + start, ring_size - start);

  if (PREDICT_TRUE (n_alloc == ring_size - start))
    n_alloc += vlib_buffer_alloc (vm, ring, n_buffers - n_alloc);

  return n_alloc;
}

/** \brief Free buffers
    Frees the entire buffer chain for each buffer

    @param vm - (vlib_main_t *) vlib main data structure pointer
    @param buffers - (u32 * ) buffer index array
    @param n_buffers - (u32) number of buffers to free

*/
always_inline void
vlib_buffer_free (vlib_main_t * vm,
		  /* pointer to first buffer */
		  u32 * buffers,
		  /* number of buffers to free */
		  u32 n_buffers)
{
  vlib_buffer_main_t *bm = vm->buffer_main;

  ASSERT (bm->cb.vlib_buffer_free_cb);

  return bm->cb.vlib_buffer_free_cb (vm, buffers, n_buffers);
}

/** \brief Free buffers, does not free the buffer chain for each buffer

    @param vm - (vlib_main_t *) vlib main data structure pointer
    @param buffers - (u32 * ) buffer index array
    @param n_buffers - (u32) number of buffers to free

*/
always_inline void
vlib_buffer_free_no_next (vlib_main_t * vm,
			  /* pointer to first buffer */
			  u32 * buffers,
			  /* number of buffers to free */
			  u32 n_buffers)
{
  vlib_buffer_main_t *bm = vm->buffer_main;

  ASSERT (bm->cb.vlib_buffer_free_no_next_cb);

  return bm->cb.vlib_buffer_free_no_next_cb (vm, buffers, n_buffers);
}

/** \brief Free one buffer
    Shorthand to free a single buffer chain.

    @param vm - (vlib_main_t *) vlib main data structure pointer
    @param buffer_index - (u32) buffer index to free
*/
always_inline void
vlib_buffer_free_one (vlib_main_t * vm, u32 buffer_index)
{
  vlib_buffer_free (vm, &buffer_index, /* n_buffers */ 1);
}

/** \brief Free buffers from ring

    @param vm - (vlib_main_t *) vlib main data structure pointer
    @param buffers - (u32 * ) buffer index ring
    @param start - (u32) first slot in the ring
    @param ring_size - (u32) ring size
    @param n_buffers - (u32) number of buffers
*/
always_inline void
vlib_buffer_free_from_ring (vlib_main_t * vm, u32 * ring, u32 start,
			    u32 ring_size, u32 n_buffers)
{
  ASSERT (n_buffers <= ring_size);

  if (PREDICT_TRUE (start + n_buffers <= ring_size))
    {
      vlib_buffer_free (vm, ring + start, n_buffers);
    }
  else
    {
      vlib_buffer_free (vm, ring + start, ring_size - start);
      vlib_buffer_free (vm, ring, n_buffers - (ring_size - start));
    }
}

/** \brief Free buffers from ring without freeing tail buffers

    @param vm - (vlib_main_t *) vlib main data structure pointer
    @param buffers - (u32 * ) buffer index ring
    @param start - (u32) first slot in the ring
    @param ring_size - (u32) ring size
    @param n_buffers - (u32) number of buffers
*/
always_inline void
vlib_buffer_free_from_ring_no_next (vlib_main_t * vm, u32 * ring, u32 start,
				    u32 ring_size, u32 n_buffers)
{
  ASSERT (n_buffers <= ring_size);

  if (PREDICT_TRUE (start + n_buffers <= ring_size))
    {
      vlib_buffer_free_no_next (vm, ring + start, n_buffers);
    }
  else
    {
      vlib_buffer_free_no_next (vm, ring + start, ring_size - start);
      vlib_buffer_free_no_next (vm, ring, n_buffers - (ring_size - start));
    }
}

/* Add/delete buffer free lists. */
vlib_buffer_free_list_index_t vlib_buffer_create_free_list (vlib_main_t * vm,
							    u32 n_data_bytes,
							    char *fmt, ...);
always_inline void
vlib_buffer_delete_free_list (vlib_main_t * vm,
			      vlib_buffer_free_list_index_t free_list_index)
{
  vlib_buffer_main_t *bm = vm->buffer_main;

  ASSERT (bm->cb.vlib_buffer_delete_free_list_cb);

  bm->cb.vlib_buffer_delete_free_list_cb (vm, free_list_index);
}

/* Make sure we have at least given number of unaligned buffers. */
void vlib_buffer_free_list_fill_unaligned (vlib_main_t * vm,
					   vlib_buffer_free_list_t *
					   free_list,
					   uword n_unaligned_buffers);

always_inline vlib_buffer_free_list_t *
vlib_buffer_get_free_list (vlib_main_t * vm,
			   vlib_buffer_free_list_index_t free_list_index)
{
  vlib_buffer_free_list_t *f;

  f = pool_elt_at_index (vm->buffer_free_list_pool, free_list_index);

  /* Sanity: indices must match. */
  ASSERT (f->index == free_list_index);

  return f;
}

always_inline u32
vlib_buffer_free_list_buffer_size (vlib_main_t * vm,
				   vlib_buffer_free_list_index_t index)
{
  vlib_buffer_free_list_t *f = vlib_buffer_get_free_list (vm, index);
  return f->n_data_bytes;
}

/* Append given data to end of buffer, possibly allocating new buffers. */
int vlib_buffer_add_data (vlib_main_t * vm, u32 * buffer_index, void *data,
			  u32 n_data_bytes);

/* duplicate all buffers in chain */
always_inline vlib_buffer_t *
vlib_buffer_copy (vlib_main_t * vm, vlib_buffer_t * b)
{
  vlib_buffer_t *s, *d, *fd;
  uword n_alloc, n_buffers = 1;
  u32 flag_mask = VLIB_BUFFER_NEXT_PRESENT | VLIB_BUFFER_TOTAL_LENGTH_VALID;
  int i;

  s = b;
  while (s->flags & VLIB_BUFFER_NEXT_PRESENT)
    {
      n_buffers++;
      s = vlib_get_buffer (vm, s->next_buffer);
    }
  u32 new_buffers[n_buffers];

  n_alloc = vlib_buffer_alloc (vm, new_buffers, n_buffers);

  /* No guarantee that we'll get all the buffers we asked for */
  if (PREDICT_FALSE (n_alloc < n_buffers))
    {
      if (n_alloc > 0)
	vlib_buffer_free (vm, new_buffers, n_alloc);
      return 0;
    }

  /* 1st segment */
  s = b;
  fd = d = vlib_get_buffer (vm, new_buffers[0]);
  d->current_data = s->current_data;
  d->current_length = s->current_length;
  d->flags = s->flags & flag_mask;
  d->total_length_not_including_first_buffer =
    s->total_length_not_including_first_buffer;
  clib_memcpy_fast (d->opaque, s->opaque, sizeof (s->opaque));
  clib_memcpy_fast (d->opaque2, s->opaque2, sizeof (s->opaque2));
  clib_memcpy_fast (vlib_buffer_get_current (d),
		    vlib_buffer_get_current (s), s->current_length);

  /* next segments */
  for (i = 1; i < n_buffers; i++)
    {
      /* previous */
      d->next_buffer = new_buffers[i];
      /* current */
      s = vlib_get_buffer (vm, s->next_buffer);
      d = vlib_get_buffer (vm, new_buffers[i]);
      d->current_data = s->current_data;
      d->current_length = s->current_length;
      clib_memcpy_fast (vlib_buffer_get_current (d),
			vlib_buffer_get_current (s), s->current_length);
      d->flags = s->flags & flag_mask;
    }

  return fd;
}

/** \brief Create a maximum of 256 clones of buffer and store them
    in the supplied array

    @param vm - (vlib_main_t *) vlib main data structure pointer
    @param src_buffer - (u32) source buffer index
    @param buffers - (u32 * ) buffer index array
    @param n_buffers - (u16) number of buffer clones requested (<=256)
    @param head_end_offset - (u16) offset relative to current position
           where packet head ends
    @return - (u16) number of buffers actually cloned, may be
    less than the number requested or zero
*/
always_inline u16
vlib_buffer_clone_256 (vlib_main_t * vm, u32 src_buffer, u32 * buffers,
		       u16 n_buffers, u16 head_end_offset)
{
  u16 i;
  vlib_buffer_t *s = vlib_get_buffer (vm, src_buffer);

  ASSERT (s->n_add_refs == 0);
  ASSERT (n_buffers);
  ASSERT (n_buffers <= 256);

  if (s->current_length <= head_end_offset + CLIB_CACHE_LINE_BYTES * 2)
    {
      buffers[0] = src_buffer;
      for (i = 1; i < n_buffers; i++)
	{
	  vlib_buffer_t *d;
	  d = vlib_buffer_copy (vm, s);
	  if (d == 0)
	    return i;
	  buffers[i] = vlib_get_buffer_index (vm, d);

	}
      return n_buffers;
    }

  if (PREDICT_FALSE (n_buffers == 1))
    {
      buffers[0] = src_buffer;
      return 1;
    }

  n_buffers = vlib_buffer_alloc (vm, buffers, n_buffers);

  for (i = 0; i < n_buffers; i++)
    {
      vlib_buffer_t *d = vlib_get_buffer (vm, buffers[i]);
      d->current_data = s->current_data;
      d->current_length = head_end_offset;
      d->total_length_not_including_first_buffer = s->current_length -
	head_end_offset;
      if (PREDICT_FALSE (s->flags & VLIB_BUFFER_NEXT_PRESENT))
	{
	  d->total_length_not_including_first_buffer +=
	    s->total_length_not_including_first_buffer;
	}
      d->flags = s->flags | VLIB_BUFFER_NEXT_PRESENT;
      d->flags &= ~VLIB_BUFFER_EXT_HDR_VALID;
      clib_memcpy_fast (d->opaque, s->opaque, sizeof (s->opaque));
      clib_memcpy_fast (d->opaque2, s->opaque2, sizeof (s->opaque2));
      clib_memcpy_fast (vlib_buffer_get_current (d),
			vlib_buffer_get_current (s), head_end_offset);
      d->next_buffer = src_buffer;
    }
  vlib_buffer_advance (s, head_end_offset);
  s->n_add_refs = n_buffers - 1;
  while (s->flags & VLIB_BUFFER_NEXT_PRESENT)
    {
      s = vlib_get_buffer (vm, s->next_buffer);
      s->n_add_refs = n_buffers - 1;
    }

  return n_buffers;
}

/** \brief Create multiple clones of buffer and store them
    in the supplied array

    @param vm - (vlib_main_t *) vlib main data structure pointer
    @param src_buffer - (u32) source buffer index
    @param buffers - (u32 * ) buffer index array
    @param n_buffers - (u16) number of buffer clones requested (<=256)
    @param head_end_offset - (u16) offset relative to current position
           where packet head ends
    @return - (u16) number of buffers actually cloned, may be
    less than the number requested or zero
*/
always_inline u16
vlib_buffer_clone (vlib_main_t * vm, u32 src_buffer, u32 * buffers,
		   u16 n_buffers, u16 head_end_offset)
{
  vlib_buffer_t *s = vlib_get_buffer (vm, src_buffer);
  u16 n_cloned = 0;

  while (n_buffers > 256)
    {
      vlib_buffer_t *copy;
      copy = vlib_buffer_copy (vm, s);
      n_cloned += vlib_buffer_clone_256 (vm,
					 vlib_get_buffer_index (vm, copy),
					 (buffers + n_cloned),
					 256, head_end_offset);
      n_buffers -= 256;
    }
  n_cloned += vlib_buffer_clone_256 (vm, src_buffer,
				     buffers + n_cloned,
				     n_buffers, head_end_offset);

  return n_cloned;
}

/** \brief Attach cloned tail to the buffer

    @param vm - (vlib_main_t *) vlib main data structure pointer
    @param head - (vlib_buffer_t *) head buffer
    @param tail - (Vlib buffer_t *) tail buffer to clone and attach to head
*/

always_inline void
vlib_buffer_attach_clone (vlib_main_t * vm, vlib_buffer_t * head,
			  vlib_buffer_t * tail)
{
  ASSERT ((head->flags & VLIB_BUFFER_NEXT_PRESENT) == 0);

  head->flags |= VLIB_BUFFER_NEXT_PRESENT;
  head->flags &= ~VLIB_BUFFER_TOTAL_LENGTH_VALID;
  head->flags &= ~VLIB_BUFFER_EXT_HDR_VALID;
  head->flags |= (tail->flags & VLIB_BUFFER_TOTAL_LENGTH_VALID);
  head->next_buffer = vlib_get_buffer_index (vm, tail);
  head->total_length_not_including_first_buffer = tail->current_length +
    tail->total_length_not_including_first_buffer;

next_segment:
  clib_atomic_add_fetch (&tail->n_add_refs, 1);

  if (tail->flags & VLIB_BUFFER_NEXT_PRESENT)
    {
      tail = vlib_get_buffer (vm, tail->next_buffer);
      goto next_segment;
    }
}

/* Initializes the buffer as an empty packet with no chained buffers. */
always_inline void
vlib_buffer_chain_init (vlib_buffer_t * first)
{
  first->total_length_not_including_first_buffer = 0;
  first->current_length = 0;
  first->flags &= ~VLIB_BUFFER_NEXT_PRESENT;
  first->flags |= VLIB_BUFFER_TOTAL_LENGTH_VALID;
}

/* The provided next_bi buffer index is appended to the end of the packet. */
always_inline vlib_buffer_t *
vlib_buffer_chain_buffer (vlib_main_t * vm, vlib_buffer_t * last, u32 next_bi)
{
  vlib_buffer_t *next_buffer = vlib_get_buffer (vm, next_bi);
  last->next_buffer = next_bi;
  last->flags |= VLIB_BUFFER_NEXT_PRESENT;
  next_buffer->current_length = 0;
  next_buffer->flags &= ~VLIB_BUFFER_NEXT_PRESENT;
  return next_buffer;
}

/* Increases or decreases the packet length.
 * It does not allocate or deallocate new buffers.
 * Therefore, the added length must be compatible
 * with the last buffer. */
always_inline void
vlib_buffer_chain_increase_length (vlib_buffer_t * first,
				   vlib_buffer_t * last, i32 len)
{
  last->current_length += len;
  if (first != last)
    first->total_length_not_including_first_buffer += len;
}

/* Copy data to the end of the packet and increases its length.
 * It does not allocate new buffers.
 * Returns the number of copied bytes. */
always_inline u16
vlib_buffer_chain_append_data (vlib_main_t * vm,
			       vlib_buffer_free_list_index_t free_list_index,
			       vlib_buffer_t * first,
			       vlib_buffer_t * last, void *data, u16 data_len)
{
  u32 n_buffer_bytes =
    vlib_buffer_free_list_buffer_size (vm, free_list_index);
  ASSERT (n_buffer_bytes >= last->current_length + last->current_data);
  u16 len = clib_min (data_len,
		      n_buffer_bytes - last->current_length -
		      last->current_data);
  clib_memcpy_fast (vlib_buffer_get_current (last) + last->current_length,
		    data, len);
  vlib_buffer_chain_increase_length (first, last, len);
  return len;
}

/* Copy data to the end of the packet and increases its length.
 * Allocates additional buffers from the free list if necessary.
 * Returns the number of copied bytes.
 * 'last' value is modified whenever new buffers are allocated and
 * chained and points to the last buffer in the chain. */
u16
vlib_buffer_chain_append_data_with_alloc (vlib_main_t * vm,
					  vlib_buffer_free_list_index_t
					  free_list_index,
					  vlib_buffer_t * first,
					  vlib_buffer_t ** last, void *data,
					  u16 data_len);
void vlib_buffer_chain_validate (vlib_main_t * vm, vlib_buffer_t * first);

format_function_t format_vlib_buffer, format_vlib_buffer_and_data,
  format_vlib_buffer_contents;

typedef struct
{
  /* Vector of packet data. */
  u8 *packet_data;

  /* Number of buffers to allocate in each call to allocator. */
  u32 min_n_buffers_each_alloc;

  /* Buffer free list for this template. */
  vlib_buffer_free_list_index_t free_list_index;

  u32 *free_buffers;

  u8 *name;
} vlib_packet_template_t;

void vlib_packet_template_get_packet_helper (vlib_main_t * vm,
					     vlib_packet_template_t * t);

void vlib_packet_template_init (vlib_main_t * vm,
				vlib_packet_template_t * t,
				void *packet_data,
				uword n_packet_data_bytes,
				uword min_n_buffers_each_alloc,
				char *fmt, ...);

void *vlib_packet_template_get_packet (vlib_main_t * vm,
				       vlib_packet_template_t * t,
				       u32 * bi_result);

always_inline void
vlib_packet_template_free (vlib_main_t * vm, vlib_packet_template_t * t)
{
  vec_free (t->packet_data);
}

/* Set a buffer quickly into "uninitialized" state.  We want this to
   be extremely cheap and arrange for all fields that need to be
   initialized to be in the first 128 bits of the buffer. */
always_inline void
vlib_buffer_init_for_free_list (vlib_buffer_t * dst,
				vlib_buffer_free_list_t * fl)
{
  vlib_buffer_t *src = &fl->buffer_init_template;

  /* Make sure vlib_buffer_t is cacheline aligned and sized */
  ASSERT (STRUCT_OFFSET_OF (vlib_buffer_t, cacheline0) == 0);
  ASSERT (STRUCT_OFFSET_OF (vlib_buffer_t, cacheline1) ==
	  CLIB_CACHE_LINE_BYTES);
  ASSERT (STRUCT_OFFSET_OF (vlib_buffer_t, cacheline2) ==
	  CLIB_CACHE_LINE_BYTES * 2);

  /* Make sure buffer template is sane. */
  vlib_buffer_copy_template (dst, src);

  /* Not in the first 16 octets. */
  dst->n_add_refs = src->n_add_refs;

  /* Make sure it really worked. */
#define _(f) ASSERT (dst->f == src->f);
  _(current_data);
  _(current_length);
  _(flags);
#undef _
  /* ASSERT (dst->total_length_not_including_first_buffer == 0); */
  /* total_length_not_including_first_buffer is not in the template anymore
   * so it may actually not zeroed for some buffers. One option is to
   * uncomment the line lower (comes at a cost), the other, is to just  not
   * care */
  /* dst->total_length_not_including_first_buffer = 0; */
  ASSERT (dst->n_add_refs == 0);
}

static_always_inline vlib_buffer_pool_t *
vlib_buffer_pool_get (vlib_main_t * vm, u8 buffer_pool_index)
{
  vlib_buffer_main_t *bm = vm->buffer_main;
  return vec_elt_at_index (bm->buffer_pools, buffer_pool_index);
}

always_inline void
vlib_buffer_add_to_free_list (vlib_main_t * vm,
			      vlib_buffer_free_list_t * f,
			      u32 buffer_index, u8 do_init)
{
  vlib_buffer_pool_t *bp = vlib_buffer_pool_get (vm, f->buffer_pool_index);
  vlib_buffer_t *b;
  b = vlib_get_buffer (vm, buffer_index);
  if (PREDICT_TRUE (do_init))
    vlib_buffer_init_for_free_list (b, f);
  vec_add1_aligned (f->buffers, buffer_index, CLIB_CACHE_LINE_BYTES);

  if (vec_len (f->buffers) > 4 * VLIB_FRAME_SIZE)
    {
      clib_spinlock_lock (&bp->lock);
      /* keep last stored buffers, as they are more likely hot in the cache */
      vec_add_aligned (bp->buffers, f->buffers, VLIB_FRAME_SIZE,
		       CLIB_CACHE_LINE_BYTES);
      vec_delete (f->buffers, VLIB_FRAME_SIZE, 0);
      f->n_alloc -= VLIB_FRAME_SIZE;
      clib_spinlock_unlock (&bp->lock);
    }
}

#if CLIB_DEBUG > 0
extern u32 *vlib_buffer_state_validation_lock;
extern uword *vlib_buffer_state_validation_hash;
extern void *vlib_buffer_state_heap;
#endif

static inline void
vlib_validate_buffer_in_use (vlib_buffer_t * b, u32 expected)
{
#if CLIB_DEBUG > 0
  uword *p;
  void *oldheap;

  oldheap = clib_mem_set_heap (vlib_buffer_state_heap);

  while (clib_atomic_test_and_set (vlib_buffer_state_validation_lock))
    ;

  p = hash_get (vlib_buffer_state_validation_hash, b);

  /* If we don't know about b, declare it to be in the expected state */
  if (!p)
    {
      hash_set (vlib_buffer_state_validation_hash, b, expected);
      goto out;
    }

  if (p[0] != expected)
    {
      void cj_stop (void);
      u32 bi;
      vlib_main_t *vm = &vlib_global_main;

      cj_stop ();

      bi = vlib_get_buffer_index (vm, b);

      clib_mem_set_heap (oldheap);
      clib_warning ("%.6f buffer %llx (%d): %s, not %s",
		    vlib_time_now (vm), bi,
		    p[0] ? "busy" : "free", expected ? "busy" : "free");
      os_panic ();
    }
out:
  CLIB_MEMORY_BARRIER ();
  *vlib_buffer_state_validation_lock = 0;
  clib_mem_set_heap (oldheap);
#endif
}

static inline void
vlib_validate_buffer_set_in_use (vlib_buffer_t * b, u32 expected)
{
#if CLIB_DEBUG > 0
  void *oldheap;

  oldheap = clib_mem_set_heap (vlib_buffer_state_heap);

  while (clib_atomic_test_and_set (vlib_buffer_state_validation_lock))
    ;

  hash_set (vlib_buffer_state_validation_hash, b, expected);

  CLIB_MEMORY_BARRIER ();
  *vlib_buffer_state_validation_lock = 0;
  clib_mem_set_heap (oldheap);
#endif
}

/** minimum data size of first buffer in a buffer chain */
#define VLIB_BUFFER_CHAIN_MIN_FIRST_DATA_SIZE (256)

/**
 * @brief compress buffer chain in a way where the first buffer is at least
 * VLIB_BUFFER_CHAIN_MIN_FIRST_DATA_SIZE long
 *
 * @param[in] vm - vlib_main
 * @param[in,out] first - first buffer in chain
 * @param[in,out] discard_vector - vector of buffer indexes which were removed
 * from the chain
 */
always_inline void
vlib_buffer_chain_compress (vlib_main_t * vm,
			    vlib_buffer_t * first, u32 ** discard_vector)
{
  if (first->current_length >= VLIB_BUFFER_CHAIN_MIN_FIRST_DATA_SIZE ||
      !(first->flags & VLIB_BUFFER_NEXT_PRESENT))
    {
      /* this is already big enough or not a chain */
      return;
    }
  /* probe free list to find allocated buffer size to avoid overfill */
  vlib_buffer_free_list_t *free_list;

  free_list = pool_elt_at_index (vm->buffer_free_list_pool,
				 VLIB_BUFFER_DEFAULT_FREE_LIST_INDEX);

  u32 want_first_size = clib_min (VLIB_BUFFER_CHAIN_MIN_FIRST_DATA_SIZE,
				  free_list->n_data_bytes -
				  first->current_data);
  do
    {
      vlib_buffer_t *second = vlib_get_buffer (vm, first->next_buffer);
      u32 need = want_first_size - first->current_length;
      u32 amount_to_copy = clib_min (need, second->current_length);
      clib_memcpy_fast (((u8 *) vlib_buffer_get_current (first)) +
			first->current_length,
			vlib_buffer_get_current (second), amount_to_copy);
      first->current_length += amount_to_copy;
      second->current_data += amount_to_copy;
      second->current_length -= amount_to_copy;
      if (first->flags & VLIB_BUFFER_TOTAL_LENGTH_VALID)
	{
	  first->total_length_not_including_first_buffer -= amount_to_copy;
	}
      if (!second->current_length)
	{
	  vec_add1 (*discard_vector, first->next_buffer);
	  if (second->flags & VLIB_BUFFER_NEXT_PRESENT)
	    {
	      first->next_buffer = second->next_buffer;
	    }
	  else
	    {
	      first->flags &= ~VLIB_BUFFER_NEXT_PRESENT;
	    }
	  second->flags &= ~VLIB_BUFFER_NEXT_PRESENT;
	}
    }
  while ((first->current_length < want_first_size) &&
	 (first->flags & VLIB_BUFFER_NEXT_PRESENT));
}

/**
 * @brief linearize buffer chain - the first buffer is filled, if needed,
 * buffers are allocated and filled, returns free space in last buffer or
 * negative on failure
 *
 * @param[in] vm - vlib_main
 * @param[in,out] first - first buffer in chain
 */
always_inline int
vlib_buffer_chain_linearize (vlib_main_t * vm, vlib_buffer_t * first)
{
  vlib_buffer_t *b = first;
  vlib_buffer_free_list_t *fl =
    vlib_buffer_get_free_list (vm, VLIB_BUFFER_DEFAULT_FREE_LIST_INDEX);
  u32 buf_len = fl->n_data_bytes;
  // free buffer chain starting from the second buffer
  int free_count = (b->flags & VLIB_BUFFER_NEXT_PRESENT) != 0;
  u32 chain_to_free = b->next_buffer;

  u32 len = vlib_buffer_length_in_chain (vm, b);
  u32 free_len = buf_len - b->current_data - b->current_length;
  int alloc_len = clib_max (len - free_len, 0);	//use the free len in the first buffer
  int n_buffers = (alloc_len + buf_len - 1) / buf_len;
  u32 new_buffers[n_buffers];

  u32 n_alloc = vlib_buffer_alloc (vm, new_buffers, n_buffers);
  if (n_alloc != n_buffers)
    {
      vlib_buffer_free_no_next (vm, new_buffers, n_alloc);
      return -1;
    }

  vlib_buffer_t *s = b;
  while (s->flags & VLIB_BUFFER_NEXT_PRESENT)
    {
      s = vlib_get_buffer (vm, s->next_buffer);
      int d_free_len = buf_len - b->current_data - b->current_length;
      ASSERT (d_free_len >= 0);
      // chain buf and split write
      u32 copy_len = clib_min (d_free_len, s->current_length);
      u8 *d = vlib_buffer_put_uninit (b, copy_len);
      clib_memcpy (d, vlib_buffer_get_current (s), copy_len);
      int rest = s->current_length - copy_len;
      if (rest > 0)
	{
	  //prev buf is full
	  ASSERT (vlib_buffer_get_tail (b) == b->data + buf_len);
	  ASSERT (n_buffers > 0);
	  b = vlib_buffer_chain_buffer (vm, b, new_buffers[--n_buffers]);
	  //make full use of the new buffers
	  b->current_data = 0;
	  d = vlib_buffer_put_uninit (b, rest);
	  clib_memcpy (d, vlib_buffer_get_current (s) + copy_len, rest);
	}
    }
  vlib_buffer_free (vm, &chain_to_free, free_count);
  b->flags &= ~VLIB_BUFFER_TOTAL_LENGTH_VALID;
  if (b == first)		/* no buffers addeed */
    b->flags &= ~VLIB_BUFFER_NEXT_PRESENT;
  ASSERT (len == vlib_buffer_length_in_chain (vm, first));
  ASSERT (n_buffers == 0);
  return buf_len - b->current_data - b->current_length;
}

#endif /* included_vlib_buffer_funcs_h */

/*
 * fd.io coding-style-patch-verification: ON
 *
 * Local Variables:
 * eval: (c-set-style "gnu")
 * End:
 */