input.c

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/*
 * 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.
 */
/*
 * pg_input.c: buffer generator input
 *
 * 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.
 */

#include <vlib/vlib.h>
#include <vnet/pg/pg.h>
#include <vnet/vnet.h>

#if DPDK==1
#include <vnet/devices/dpdk/dpdk.h>
#endif

static inline void 
pg_set_mbuf_metadata (pg_main_t * pg, u32 * buffers, u32 n_alloc)
{
#if DPDK == 1
  vlib_main_t * vm = vlib_get_main();
  vlib_buffer_t * b;
  struct rte_mbuf * mb;
  i16 delta;
  u16 new_data_len;
  u16 new_pkt_len;

  int i;

  for (i = 0; i < n_alloc; i++)
    {
      b = vlib_get_buffer (vm, buffers[i]);
      mb = rte_mbuf_from_vlib_buffer(b);

      delta = vlib_buffer_length_in_chain (vm, b) - (i16) mb->pkt_len;
      new_data_len = (u16)((i16) mb->data_len + delta);
      new_pkt_len = (u16)((i16) mb->pkt_len + delta);

      mb->data_len = new_data_len;
      mb->pkt_len = new_pkt_len;
      mb->data_off = (u16)((RTE_PKTMBUF_HEADROOM) + b->current_data);
    }
#endif  
}

static int
validate_buffer_data2 (vlib_buffer_t * b, pg_stream_t * s,
                       u32 data_offset, u32 n_bytes)
{
  u8 * bd, * pd, * pm;
  u32 i;

  bd = b->data;
  pd = s->fixed_packet_data + data_offset;
  pm = s->fixed_packet_data_mask + data_offset;

  if (pd + n_bytes >= vec_end (s->fixed_packet_data))
    n_bytes = (pd < vec_end (s->fixed_packet_data)
               ? vec_end (s->fixed_packet_data) - pd
               : 0);

  for (i = 0; i < n_bytes; i++)
    if ((bd[i] & pm[i]) != pd[i])
      break;

  if (i >= n_bytes)
    return 1;

  clib_warning ("buffer %U", format_vlib_buffer, b);
  clib_warning ("differ at index %d", i);
  clib_warning ("is     %U", format_hex_bytes, bd, n_bytes);
  clib_warning ("mask   %U", format_hex_bytes, pm, n_bytes);
  clib_warning ("expect %U", format_hex_bytes, pd, n_bytes);
  return 0;
}

static int
validate_buffer_data (vlib_buffer_t * b, pg_stream_t * s)
{ return validate_buffer_data2 (b, s, 0, s->buffer_bytes); }

always_inline void
set_1 (void * a0,
       u64 v0,
       u64 v_min, u64 v_max,
       u32 n_bits,
       u32 is_net_byte_order)
{
  ASSERT (v0 >= v_min && v0 <= v_max);
  if (n_bits == BITS (u8))
    {
      ((u8 *) a0)[0] = v0;
    }
  else if (n_bits == BITS (u16))
    {
      if (is_net_byte_order)
        v0 = clib_host_to_net_u16 (v0);
      clib_mem_unaligned (a0, u16) = v0;
    }
  else if (n_bits == BITS (u32))
    {
      if (is_net_byte_order)
        v0 = clib_host_to_net_u32 (v0);
      clib_mem_unaligned (a0, u32) = v0;
    }
  else if (n_bits == BITS (u64))
    {
      if (is_net_byte_order)
        v0 = clib_host_to_net_u64 (v0);
      clib_mem_unaligned (a0, u64) = v0;
    }
}

always_inline void
set_2 (void * a0, void * a1,
       u64 v0, u64 v1,
       u64 v_min, u64 v_max,
       u32 n_bits,
       u32 is_net_byte_order,
       u32 is_increment)
{
  ASSERT (v0 >= v_min && v0 <= v_max);
  ASSERT (v1 >= v_min && v1 <= (v_max + is_increment));
  if (n_bits == BITS (u8))
    {
      ((u8 *) a0)[0] = v0;
      ((u8 *) a1)[0] = v1;
    }
  else if (n_bits == BITS (u16))
    {
      if (is_net_byte_order)
        {
          v0 = clib_host_to_net_u16 (v0);
          v1 = clib_host_to_net_u16 (v1);
        }
      clib_mem_unaligned (a0, u16) = v0;
      clib_mem_unaligned (a1, u16) = v1;
    }
  else if (n_bits == BITS (u32))
    {
      if (is_net_byte_order)
        {
          v0 = clib_host_to_net_u32 (v0);
          v1 = clib_host_to_net_u32 (v1);
        }
      clib_mem_unaligned (a0, u32) = v0;
      clib_mem_unaligned (a1, u32) = v1;
    }
  else if (n_bits == BITS (u64))
    {
      if (is_net_byte_order)
        {
          v0 = clib_host_to_net_u64 (v0);
          v1 = clib_host_to_net_u64 (v1);
        }
      clib_mem_unaligned (a0, u64) = v0;
      clib_mem_unaligned (a1, u64) = v1;
    }
}

static_always_inline void
do_set_fixed (pg_main_t * pg,
              pg_stream_t * s,
              u32 * buffers,
              u32 n_buffers,
              u32 n_bits,
              u32 byte_offset,
              u32 is_net_byte_order,
              u64 v_min, u64 v_max)

{
  vlib_main_t * vm = pg->vlib_main;

  while (n_buffers >= 4)
    {
      vlib_buffer_t * b0, * b1, * b2, * b3;
      void * a0, * a1;

      b0 = vlib_get_buffer (vm, buffers[0]);
      b1 = vlib_get_buffer (vm, buffers[1]);
      b2 = vlib_get_buffer (vm, buffers[2]);
      b3 = vlib_get_buffer (vm, buffers[3]);
      buffers += 2;
      n_buffers -= 2;

      a0 = (void *) b0 + byte_offset;
      a1 = (void *) b1 + byte_offset;
      CLIB_PREFETCH ((void *) b2 + byte_offset, sizeof (v_min), WRITE);
      CLIB_PREFETCH ((void *) b3 + byte_offset, sizeof (v_min), WRITE);

      set_2 (a0, a1, v_min, v_min,
             v_min, v_max,
             n_bits, is_net_byte_order,
             /* is_increment */ 0);

      ASSERT (validate_buffer_data (b0, s));
      ASSERT (validate_buffer_data (b1, s));
    }

  while (n_buffers > 0)
    {
      vlib_buffer_t * b0;
      void * a0;

      b0 = vlib_get_buffer (vm, buffers[0]);
      buffers += 1;
      n_buffers -= 1;

      a0 = (void *) b0 + byte_offset;

      set_1 (a0, v_min,
             v_min, v_max,
             n_bits, is_net_byte_order);

      ASSERT (validate_buffer_data (b0, s));
    }
}

static_always_inline u64
do_set_increment (pg_main_t * pg,
                  pg_stream_t * s,
                  u32 * buffers,
                  u32 n_buffers,
                  u32 n_bits,
                  u32 byte_offset,
                  u32 is_net_byte_order,
                  u32 want_sum,
                  u64 * sum_result,
                  u64 v_min, u64 v_max,
                  u64 v)
{
  vlib_main_t * vm = pg->vlib_main;
  u64 sum = 0;

  ASSERT (v >= v_min && v <= v_max);

  while (n_buffers >= 4)
    {
      vlib_buffer_t * b0, * b1, * b2, * b3;
      void * a0, * a1;
      u64 v_old;

      b0 = vlib_get_buffer (vm, buffers[0]);
      b1 = vlib_get_buffer (vm, buffers[1]);
      b2 = vlib_get_buffer (vm, buffers[2]);
      b3 = vlib_get_buffer (vm, buffers[3]);
      buffers += 2;
      n_buffers -= 2;

      a0 = (void *) b0 + byte_offset;
      a1 = (void *) b1 + byte_offset;
      CLIB_PREFETCH ((void *) b2 + byte_offset, sizeof (v_min), WRITE);
      CLIB_PREFETCH ((void *) b3 + byte_offset, sizeof (v_min), WRITE);

      v_old = v;
      v = v_old + 2;
      v = v > v_max ? v_min : v;
      set_2 (a0, a1,
             v_old + 0, v_old + 1,
             v_min, v_max,
             n_bits, is_net_byte_order,
             /* is_increment */ 1);

      if (want_sum)
        sum += 2*v_old + 1;

      if (PREDICT_FALSE (v_old + 1 > v_max))
        {
          if (want_sum)
            sum -= 2*v_old + 1;

          v = v_old;
          set_1 (a0, v + 0, v_min, v_max, n_bits, is_net_byte_order);
          if (want_sum)
            sum += v;
          v += 1;

          v = v > v_max ? v_min : v;
          set_1 (a1, v + 0, v_min, v_max, n_bits, is_net_byte_order);
          if (want_sum)
            sum += v;
          v += 1;
        }

      ASSERT (validate_buffer_data (b0, s));
      ASSERT (validate_buffer_data (b1, s));
    }

  while (n_buffers > 0)
    {
      vlib_buffer_t * b0;
      void * a0;
      u64 v_old;

      b0 = vlib_get_buffer (vm, buffers[0]);
      buffers += 1;
      n_buffers -= 1;

      a0 = (void *) b0 + byte_offset;

      v_old = v;
      if (want_sum)
        sum += v_old;
      v += 1;
      v = v > v_max ? v_min : v;

      ASSERT (v_old >= v_min && v_old <= v_max);
      set_1 (a0, v_old, v_min, v_max, n_bits, is_net_byte_order);

      ASSERT (validate_buffer_data (b0, s));
    }

  if (want_sum)
    *sum_result = sum;

  return v;
}

static_always_inline void
do_set_random (pg_main_t * pg,
               pg_stream_t * s,
               u32 * buffers,
               u32 n_buffers,
               u32 n_bits,
               u32 byte_offset,
               u32 is_net_byte_order,
               u32 want_sum,
               u64 * sum_result,
               u64 v_min, u64 v_max)

{
  vlib_main_t * vm = pg->vlib_main;
  u64 v_diff = v_max - v_min + 1;
  u64 r_mask = max_pow2 (v_diff) - 1;
  u64 v0, v1;
  u64 sum = 0;
  void * random_data;

  random_data = clib_random_buffer_get_data
    (&vm->random_buffer, n_buffers * n_bits / BITS (u8));

  v0 = v1 = v_min;

  while (n_buffers >= 4)
    {
      vlib_buffer_t * b0, * b1, * b2, * b3;
      void * a0, * a1;
      u64 r0=0, r1=0;           /* warnings be gone */

      b0 = vlib_get_buffer (vm, buffers[0]);
      b1 = vlib_get_buffer (vm, buffers[1]);
      b2 = vlib_get_buffer (vm, buffers[2]);
      b3 = vlib_get_buffer (vm, buffers[3]);
      buffers += 2;
      n_buffers -= 2;

      a0 = (void *) b0 + byte_offset;
      a1 = (void *) b1 + byte_offset;
      CLIB_PREFETCH ((void *) b2 + byte_offset, sizeof (v_min), WRITE);
      CLIB_PREFETCH ((void *) b3 + byte_offset, sizeof (v_min), WRITE);

      switch (n_bits)
        {
#define _(n)                                    \
          case BITS (u##n):                     \
            {                                   \
              u##n * r = random_data;           \
              r0 = r[0];                        \
              r1 = r[1];                        \
              random_data = r + 2;              \
            }                                   \
          break;

          _ (8);
          _ (16);
          _ (32);
          _ (64);

#undef _
        }

      /* Add power of 2 sized random number which may be out of range. */
      v0 += r0 & r_mask;
      v1 += r1 & r_mask;

      /* Twice should be enough to reduce to v_min .. v_max range. */
      v0 = v0 > v_max ? v0 - v_diff : v0;
      v1 = v1 > v_max ? v1 - v_diff : v1;
      v0 = v0 > v_max ? v0 - v_diff : v0;
      v1 = v1 > v_max ? v1 - v_diff : v1;

      if (want_sum)
        sum += v0 + v1;

      set_2 (a0, a1,
             v0, v1,
             v_min, v_max,
             n_bits, is_net_byte_order,
             /* is_increment */ 0);

      ASSERT (validate_buffer_data (b0, s));
      ASSERT (validate_buffer_data (b1, s));
    }

  while (n_buffers > 0)
    {
      vlib_buffer_t * b0;
      void * a0;
      u64 r0 = 0;               /* warnings be gone */

      b0 = vlib_get_buffer (vm, buffers[0]);
      buffers += 1;
      n_buffers -= 1;

      a0 = (void *) b0 + byte_offset;

      switch (n_bits)
        {
#define _(n)                                    \
          case BITS (u##n):                     \
            {                                   \
              u##n * r = random_data;           \
              r0 = r[0];                        \
              random_data = r + 1;              \
            }                                   \
          break;

          _ (8);
          _ (16);
          _ (32);
          _ (64);

#undef _
        }

      /* Add power of 2 sized random number which may be out of range. */
      v0 += r0 & r_mask;

      /* Twice should be enough to reduce to v_min .. v_max range. */
      v0 = v0 > v_max ? v0 - v_diff : v0;
      v0 = v0 > v_max ? v0 - v_diff : v0;

      if (want_sum)
        sum += v0;

      set_1 (a0, v0, v_min, v_max, n_bits, is_net_byte_order);

      ASSERT (validate_buffer_data (b0, s));
    }

  if (want_sum)
    *sum_result = sum;
}

#define _(i,t)                                                  \
  clib_mem_unaligned (a##i, t) =                                \
    clib_host_to_net_##t ((clib_net_to_host_mem_##t (a##i) &~ mask)     \
                          | (v##i << shift))
  
always_inline void
setbits_1 (void * a0,
           u64 v0,
           u64 v_min, u64 v_max,
           u32 max_bits,
           u32 n_bits,
           u64 mask,
           u32 shift)
{
  ASSERT (v0 >= v_min && v0 <= v_max);
  if (max_bits == BITS (u8))
    ((u8 *) a0)[0] = (((u8 *) a0)[0] &~ mask) | (v0 << shift);

  else if (max_bits == BITS (u16))
    {
      _ (0, u16);
    }
  else if (max_bits == BITS (u32))
    {
      _ (0, u32);
    }
  else if (max_bits == BITS (u64))
    {
      _ (0, u64);
    }
}

always_inline void
setbits_2 (void * a0, void * a1,
           u64 v0, u64 v1,
           u64 v_min, u64 v_max,
           u32 max_bits,
           u32 n_bits,
           u64 mask,
           u32 shift,
           u32 is_increment)
{
  ASSERT (v0 >= v_min && v0 <= v_max);
  ASSERT (v1 >= v_min && v1 <= v_max + is_increment);
  if (max_bits == BITS (u8))
    {
      ((u8 *) a0)[0] = (((u8 *) a0)[0] &~ mask) | (v0 << shift);
      ((u8 *) a1)[0] = (((u8 *) a1)[0] &~ mask) | (v1 << shift);
    }

  else if (max_bits == BITS (u16))
    {
      _ (0, u16);
      _ (1, u16);
    }
  else if (max_bits == BITS (u32))
    {
      _ (0, u32);
      _ (1, u32);
    }
  else if (max_bits == BITS (u64))
    {
      _ (0, u64);
      _ (1, u64);
    }
}

#undef _

static_always_inline void
do_setbits_fixed (pg_main_t * pg,
                  pg_stream_t * s,
                  u32 * buffers,
                  u32 n_buffers,
                  u32 max_bits,
                  u32 n_bits,
                  u32 byte_offset,
                  u64 v_min, u64 v_max,
                  u64 mask,
                  u32 shift)

{
  vlib_main_t * vm = pg->vlib_main;

  while (n_buffers >= 4)
    {
      vlib_buffer_t * b0, * b1, * b2, * b3;
      void * a0, * a1;

      b0 = vlib_get_buffer (vm, buffers[0]);
      b1 = vlib_get_buffer (vm, buffers[1]);
      b2 = vlib_get_buffer (vm, buffers[2]);
      b3 = vlib_get_buffer (vm, buffers[3]);
      buffers += 2;
      n_buffers -= 2;

      a0 = (void *) b0 + byte_offset;
      a1 = (void *) b1 + byte_offset;
      CLIB_PREFETCH ((void *) b2 + byte_offset, sizeof (v_min), WRITE);
      CLIB_PREFETCH ((void *) b3 + byte_offset, sizeof (v_min), WRITE);

      setbits_2 (a0, a1,
                 v_min, v_min,
                 v_min, v_max,
                 max_bits, n_bits, mask, shift,
                 /* is_increment */ 0);

      ASSERT (validate_buffer_data (b0, s));
      ASSERT (validate_buffer_data (b1, s));
    }

  while (n_buffers > 0)
    {
      vlib_buffer_t * b0;
      void * a0;

      b0 = vlib_get_buffer (vm, buffers[0]);
      buffers += 1;
      n_buffers -= 1;

      a0 = (void *) b0 + byte_offset;

      setbits_1 (a0, v_min, v_min, v_max, max_bits, n_bits, mask, shift);
      ASSERT (validate_buffer_data (b0, s));
    }
}

static_always_inline u64
do_setbits_increment (pg_main_t * pg,
                      pg_stream_t * s,
                      u32 * buffers,
                      u32 n_buffers,
                      u32 max_bits,
                      u32 n_bits,
                      u32 byte_offset,
                      u64 v_min, u64 v_max,
                      u64 v,
                      u64 mask,
                      u32 shift)
{
  vlib_main_t * vm = pg->vlib_main;

  ASSERT (v >= v_min && v <= v_max);

  while (n_buffers >= 4)
    {
      vlib_buffer_t * b0, * b1, * b2, * b3;
      void * a0, * a1;
      u64 v_old;

      b0 = vlib_get_buffer (vm, buffers[0]);
      b1 = vlib_get_buffer (vm, buffers[1]);
      b2 = vlib_get_buffer (vm, buffers[2]);
      b3 = vlib_get_buffer (vm, buffers[3]);
      buffers += 2;
      n_buffers -= 2;

      a0 = (void *) b0 + byte_offset;
      a1 = (void *) b1 + byte_offset;
      CLIB_PREFETCH ((void *) b2 + byte_offset, sizeof (v_min), WRITE);
      CLIB_PREFETCH ((void *) b3 + byte_offset, sizeof (v_min), WRITE);

      v_old = v;
      v = v_old + 2;
      v = v > v_max ? v_min : v;
      setbits_2 (a0, a1,
                 v_old + 0, v_old + 1,
                 v_min, v_max,
                 max_bits, n_bits, mask, shift,
                 /* is_increment */ 1);

      if (PREDICT_FALSE (v_old + 1 > v_max))
        {
          v = v_old;
          setbits_1 (a0, v + 0, v_min, v_max, max_bits, n_bits, mask, shift);
          v += 1;

          v = v > v_max ? v_min : v;
          setbits_1 (a1, v + 0, v_min, v_max, max_bits, n_bits, mask, shift);
          v += 1;
        }
      ASSERT (validate_buffer_data (b0, s));
      ASSERT (validate_buffer_data (b1, s));
    }

  while (n_buffers > 0)
    {
      vlib_buffer_t * b0;
      void * a0;
      u64 v_old;

      b0 = vlib_get_buffer (vm, buffers[0]);
      buffers += 1;
      n_buffers -= 1;

      a0 = (void *) b0 + byte_offset;

      v_old = v;
      v = v_old + 1;
      v = v > v_max ? v_min : v;

      ASSERT (v_old >= v_min && v_old <= v_max);
      setbits_1 (a0, v_old, v_min, v_max, max_bits, n_bits, mask, shift);

      ASSERT (validate_buffer_data (b0, s));
    }

  return v;
}

static_always_inline void
do_setbits_random (pg_main_t * pg,
                   pg_stream_t * s,
                   u32 * buffers,
                   u32 n_buffers,
                   u32 max_bits,
                   u32 n_bits,
                   u32 byte_offset,
                   u64 v_min, u64 v_max,
                   u64 mask,
                   u32 shift)
{
  vlib_main_t * vm = pg->vlib_main;
  u64 v_diff = v_max - v_min + 1;
  u64 r_mask = max_pow2 (v_diff) - 1;
  u64 v0, v1;
  void * random_data;

  random_data = clib_random_buffer_get_data
    (&vm->random_buffer, n_buffers * max_bits / BITS (u8));
  v0 = v1 = v_min;

  while (n_buffers >= 4)
    {
      vlib_buffer_t * b0, * b1, * b2, * b3;
      void * a0, * a1;
      u64 r0=0, r1=0;           /* warnings be gone */

      b0 = vlib_get_buffer (vm, buffers[0]);
      b1 = vlib_get_buffer (vm, buffers[1]);
      b2 = vlib_get_buffer (vm, buffers[2]);
      b3 = vlib_get_buffer (vm, buffers[3]);
      buffers += 2;
      n_buffers -= 2;

      a0 = (void *) b0 + byte_offset;
      a1 = (void *) b1 + byte_offset;
      CLIB_PREFETCH ((void *) b2 + byte_offset, sizeof (v_min), WRITE);
      CLIB_PREFETCH ((void *) b3 + byte_offset, sizeof (v_min), WRITE);

      switch (max_bits)
        {
#define _(n)                                    \
          case BITS (u##n):                     \
            {                                   \
              u##n * r = random_data;           \
              r0 = r[0];                        \
              r1 = r[1];                        \
              random_data = r + 2;              \
            }                                   \
          break;

          _ (8);
          _ (16);
          _ (32);
          _ (64);

#undef _
        }

      /* Add power of 2 sized random number which may be out of range. */
      v0 += r0 & r_mask;
      v1 += r1 & r_mask;

      /* Twice should be enough to reduce to v_min .. v_max range. */
      v0 = v0 > v_max ? v0 - v_diff : v0;
      v1 = v1 > v_max ? v1 - v_diff : v1;
      v0 = v0 > v_max ? v0 - v_diff : v0;
      v1 = v1 > v_max ? v1 - v_diff : v1;

      setbits_2 (a0, a1,
                 v0, v1,
                 v_min, v_max,
                 max_bits, n_bits, mask, shift,
                 /* is_increment */ 0);

      ASSERT (validate_buffer_data (b0, s));
      ASSERT (validate_buffer_data (b1, s));
    }

  while (n_buffers > 0)
    {
      vlib_buffer_t * b0;
      void * a0;
      u64 r0 = 0;               /* warnings be gone */

      b0 = vlib_get_buffer (vm, buffers[0]);
      buffers += 1;
      n_buffers -= 1;

      a0 = (void *) b0 + byte_offset;

      switch (max_bits)
        {
#define _(n)                                    \
          case BITS (u##n):                     \
            {                                   \
              u##n * r = random_data;           \
              r0 = r[0];                        \
              random_data = r + 1;              \
            }                                   \
          break;

          _ (8);
          _ (16);
          _ (32);
          _ (64);

#undef _
        }

      /* Add power of 2 sized random number which may be out of range. */
      v0 += r0 & r_mask;

      /* Twice should be enough to reduce to v_min .. v_max range. */
      v0 = v0 > v_max ? v0 - v_diff : v0;
      v0 = v0 > v_max ? v0 - v_diff : v0;

      setbits_1 (a0, v0, v_min, v_max, max_bits, n_bits, mask, shift);

      ASSERT (validate_buffer_data (b0, s));
    }
}

static u64 do_it (pg_main_t * pg,
                  pg_stream_t * s,
                  u32 * buffers,
                  u32 n_buffers,
                  u32 lo_bit, u32 hi_bit,
                  u64 v_min, u64 v_max,
                  u64 v,
                  pg_edit_type_t edit_type)
{
  u32 max_bits, l0, l1, h1, start_bit;

  if (v_min == v_max)
    edit_type = PG_EDIT_FIXED;

  l0 = lo_bit / BITS (u8);
  l1 = lo_bit % BITS (u8);
  h1 = hi_bit % BITS (u8);

  start_bit = l0 * BITS (u8);

  max_bits = hi_bit - start_bit;
  ASSERT (max_bits <= 64);

#define _(n)                                            \
  case (n):                                             \
    if (edit_type == PG_EDIT_INCREMENT)                 \
      v = do_set_increment (pg, s, buffers, n_buffers,  \
                            BITS (u##n),                \
                            l0,                         \
                            /* is_net_byte_order */ 1,  \
                            /* want sum */ 0, 0,        \
                            v_min, v_max,               \
                            v);                         \
    else if (edit_type == PG_EDIT_RANDOM)               \
      do_set_random (pg, s, buffers, n_buffers,         \
                     BITS (u##n),                       \
                     l0,                                \
                     /* is_net_byte_order */ 1,         \
                     /* want sum */ 0, 0,               \
                     v_min, v_max);                     \
    else /* edit_type == PG_EDIT_FIXED */               \
      do_set_fixed (pg, s, buffers, n_buffers,          \
                    BITS (u##n),                        \
                    l0,                                 \
                    /* is_net_byte_order */ 1,          \
                    v_min, v_max);                      \
  goto done;

  if (l1 == 0 && h1 == 0)
    {
      switch (max_bits)
        {
          _ (8);
          _ (16);
          _ (32);
          _ (64);
        }
    }

#undef _

  {
    u64 mask;
    u32 shift = l1;
    u32 n_bits = max_bits; 

    max_bits = clib_max (max_pow2 (n_bits), 8);

    mask = ((u64) 1 << (u64) n_bits) - 1;
    mask &= ~(((u64) 1 << (u64) shift) - 1);

    mask <<= max_bits - n_bits;
    shift += max_bits - n_bits;

    switch (max_bits)
      {
#define _(n)                                                            \
        case (n):                                                       \
          if (edit_type == PG_EDIT_INCREMENT)                           \
            v = do_setbits_increment (pg, s, buffers, n_buffers,        \
                                      BITS (u##n), n_bits,              \
                                      l0, v_min, v_max, v,              \
                                      mask, shift);                     \
          else if (edit_type == PG_EDIT_RANDOM)                         \
            do_setbits_random (pg, s, buffers, n_buffers,               \
                               BITS (u##n), n_bits,                     \
                               l0, v_min, v_max,                        \
                               mask, shift);                            \
          else /* edit_type == PG_EDIT_FIXED */                         \
            do_setbits_fixed (pg, s, buffers, n_buffers,                \
                              BITS (u##n), n_bits,                      \
                              l0, v_min, v_max,                         \
                              mask, shift);                             \
        goto done;

        _ (8);
        _ (16);
        _ (32);
        _ (64);

#undef _
      }
  }

 done:
  return v;
}

static void
pg_generate_set_lengths (pg_main_t * pg,
                         pg_stream_t * s,
                         u32 * buffers,
                         u32 n_buffers)
{
  u64 v_min, v_max, length_sum;
  pg_edit_type_t edit_type;

  v_min = s->min_packet_bytes;
  v_max = s->max_packet_bytes;
  edit_type = s->packet_size_edit_type;

  if (edit_type == PG_EDIT_INCREMENT)
    s->last_increment_packet_size
      = do_set_increment (pg, s, buffers, n_buffers,
                          8 * STRUCT_SIZE_OF (vlib_buffer_t, current_length),
                          STRUCT_OFFSET_OF (vlib_buffer_t, current_length),
                          /* is_net_byte_order */ 0,
                          /* want sum */ 1, &length_sum,
                          v_min, v_max,
                          s->last_increment_packet_size);

  else if (edit_type == PG_EDIT_RANDOM)
    do_set_random (pg, s, buffers, n_buffers,
                   8 * STRUCT_SIZE_OF (vlib_buffer_t, current_length),
                   STRUCT_OFFSET_OF (vlib_buffer_t, current_length),
                   /* is_net_byte_order */ 0,
                   /* want sum */ 1, &length_sum,
                   v_min, v_max);

  else /* edit_type == PG_EDIT_FIXED */
    {
      do_set_fixed (pg, s, buffers, n_buffers,
                    8 * STRUCT_SIZE_OF (vlib_buffer_t, current_length),
                    STRUCT_OFFSET_OF (vlib_buffer_t, current_length),
                    /* is_net_byte_order */ 0,
                    v_min, v_max);
      length_sum = v_min * n_buffers;
    }

  {
    vnet_main_t * vnm = vnet_get_main();
    vnet_interface_main_t * im = &vnm->interface_main;
    vnet_sw_interface_t * si = vnet_get_sw_interface (vnm, s->sw_if_index[VLIB_RX]);

    vlib_increment_combined_counter (im->combined_sw_if_counters
                                     + VNET_INTERFACE_COUNTER_RX,
                                     os_get_cpu_number(),
                                     si->sw_if_index,
                                     n_buffers,
                                     length_sum);
  }

  pg_set_mbuf_metadata (pg, buffers, n_buffers);
}

static void
pg_generate_fix_multi_buffer_lengths (pg_main_t * pg,
                                      pg_stream_t * s,
                                      u32 * buffers,
                                      u32 n_buffers)
{
  vlib_main_t * vm = pg->vlib_main;
  pg_buffer_index_t * pbi;
  uword n_bytes_left;
  static u32 * unused_buffers = 0;

  while (n_buffers > 0)
    {
      vlib_buffer_t * b;
      u32 bi;

      bi = buffers[0];
      b = vlib_get_buffer (vm, bi);

      /* Current length here is length of whole packet. */
      n_bytes_left = b->current_length;

      pbi = s->buffer_indices;
      while (1)
        {
          uword n = clib_min (n_bytes_left, s->buffer_bytes);

          b->current_length = n;
          n_bytes_left -= n;
          if (n_bytes_left > 0)
            b->flags |= VLIB_BUFFER_NEXT_PRESENT;
          else
            b->flags &= ~VLIB_BUFFER_NEXT_PRESENT;

          /* Return unused buffers to fifos. */
          if (n == 0)
            vec_add1 (unused_buffers, bi);

          pbi++;
          if (pbi >= vec_end (s->buffer_indices))
            break;

          bi = b->next_buffer;
          b = vlib_get_buffer (vm, bi);
        }
      ASSERT (n_bytes_left == 0);

      buffers += 1;
      n_buffers -= 1;
    }

  if (vec_len (unused_buffers) > 0)
    {
      vlib_buffer_free_no_next (vm, unused_buffers,
                                vec_len (unused_buffers));
      _vec_len (unused_buffers) = 0;
    }
}

static void
pg_generate_edit (pg_main_t * pg,
                  pg_stream_t * s,
                  u32 * buffers,
                  u32 n_buffers)
{
  pg_edit_t * e;

  vec_foreach (e, s->non_fixed_edits)
    {
      switch (e->type)
        {
        case PG_EDIT_RANDOM:
        case PG_EDIT_INCREMENT:
          {
            u32 lo_bit, hi_bit;
            u64 v_min, v_max;

            v_min = pg_edit_get_value (e, PG_EDIT_LO);
            v_max = pg_edit_get_value (e, PG_EDIT_HI);

            hi_bit = (BITS (u8) * STRUCT_OFFSET_OF (vlib_buffer_t, data)
                      + BITS (u8)
                      + e->lsb_bit_offset);
            lo_bit = hi_bit - e->n_bits;

            e->last_increment_value
              = do_it (pg, s, buffers, n_buffers, lo_bit, hi_bit, v_min, v_max,
                       e->last_increment_value,
                       e->type);
          }
          break;

        case PG_EDIT_UNSPECIFIED:
          break;

        default:
          /* Should not be any fixed edits left. */
          ASSERT (0);
          break;
        }
    }

  /* Call any edit functions to e.g. completely IP lengths, checksums, ... */
  {
    int i;
    for (i = vec_len (s->edit_groups) - 1; i >= 0; i--)
      {
        pg_edit_group_t * g = s->edit_groups + i;
        if (g->edit_function)
          g->edit_function (pg, s, g, buffers, n_buffers);
      }
  }
}

static void
pg_set_next_buffer_pointers (pg_main_t * pg,
                             pg_stream_t * s,
                             u32 * buffers,
                             u32 * next_buffers,
                             u32 n_buffers)
{
  vlib_main_t * vm = pg->vlib_main;

  while (n_buffers >= 4)
    {
      u32 ni0, ni1;
      vlib_buffer_t * b0, * b1;

      b0 = vlib_get_buffer (vm, buffers[0]);
      b1 = vlib_get_buffer (vm, buffers[1]);
      ni0 = next_buffers[0];
      ni1 = next_buffers[1];

      vlib_prefetch_buffer_with_index (vm, buffers[2], WRITE);
      vlib_prefetch_buffer_with_index (vm, buffers[3], WRITE);

      b0->flags |= VLIB_BUFFER_NEXT_PRESENT;
      b1->flags |= VLIB_BUFFER_NEXT_PRESENT;
      b0->next_buffer = ni0;
      b1->next_buffer = ni1;

      buffers += 2;
      next_buffers += 2;
      n_buffers -= 2;
    }

  while (n_buffers > 0)
    {
      u32 ni0;
      vlib_buffer_t * b0;

      b0 = vlib_get_buffer (vm, buffers[0]);
      ni0 = next_buffers[0];
      buffers += 1;
      next_buffers += 1;
      n_buffers -= 1;

      b0->flags |= VLIB_BUFFER_NEXT_PRESENT;
      b0->next_buffer = ni0;
    }
}

static_always_inline void
init_replay_buffers_inline (vlib_main_t * vm,
                            pg_stream_t * s,
                            u32 * buffers,
                            u32 n_buffers,
                            u32 data_offset,
                            u32 n_data)
{
  u32 n_left, * b, i, l;

  n_left = n_buffers;
  b = buffers;
  i = s->current_replay_packet_index;
  l = vec_len (s->replay_packet_templates);

  while (n_left >= 1)
    {
      u32 bi0, n0;
      vlib_buffer_t * b0;
      u8 * d0;

      bi0 = b[0];
      b += 1;
      n_left -= 1;

      b0 = vlib_get_buffer (vm, bi0);

      vnet_buffer (b0)->sw_if_index[VLIB_RX] = s->sw_if_index[VLIB_RX];
      /* was s->sw_if_index[VLIB_TX]; */
      vnet_buffer (b0)->sw_if_index[VLIB_TX] = (u32)~0;

      d0 = vec_elt (s->replay_packet_templates, i);

      n0 = n_data;
      if (data_offset + n_data >= vec_len (d0))
        n0 = vec_len (d0) > data_offset ? vec_len (d0) - data_offset : 0;

      b0->current_length = n0;

      clib_memcpy (b0->data, d0 + data_offset, n0);
      i = i + 1 == l ? 0 : i + 1;
    }
}

static_always_inline void
init_buffers_inline (vlib_main_t * vm,
                     pg_stream_t * s,
                     u32 * buffers,
                     u32 n_buffers,
                     u32 data_offset,
                     u32 n_data,
                     u32 set_data)
{
  u32 n_left, * b;
  u8 * data, * mask;

  if (vec_len (s->replay_packet_templates) > 0)
    return init_replay_buffers_inline (vm, s, buffers, n_buffers, data_offset, n_data);

  data = s->fixed_packet_data + data_offset;
  mask = s->fixed_packet_data_mask + data_offset;
  if (data + n_data >= vec_end (s->fixed_packet_data))
    n_data = (data < vec_end (s->fixed_packet_data)
              ? vec_end (s->fixed_packet_data) - data
              : 0);
  if (n_data > 0)
    {
      ASSERT (data + n_data <= vec_end (s->fixed_packet_data));
      ASSERT (mask + n_data <= vec_end (s->fixed_packet_data_mask));
    }

  n_left = n_buffers;
  b = buffers;

  while (n_left >= 4)
    {
      u32 bi0, bi1;
      vlib_buffer_t * b0, * b1;

      /* Prefetch next iteration. */
      vlib_prefetch_buffer_with_index (vm, b[2], STORE);
      vlib_prefetch_buffer_with_index (vm, b[3], STORE);

      bi0 = b[0];
      bi1 = b[1];
      b += 2;
      n_left -= 2;

      b0 = vlib_get_buffer (vm, bi0);
      b1 = vlib_get_buffer (vm, bi1);

      vnet_buffer (b0)->sw_if_index[VLIB_RX] =
        vnet_buffer (b1)->sw_if_index[VLIB_RX] = s->sw_if_index[VLIB_RX];

      vnet_buffer (b0)->sw_if_index[VLIB_TX] =
        vnet_buffer (b1)->sw_if_index[VLIB_TX] = (u32)~0;

      if (set_data)
        {
          clib_memcpy (b0->data, data, n_data);
          clib_memcpy (b1->data, data, n_data);
        }
      else
        {
          ASSERT (validate_buffer_data2 (b0, s, data_offset, n_data));
          ASSERT (validate_buffer_data2 (b1, s, data_offset, n_data));
        }
    }

  while (n_left >= 1)
    {
      u32 bi0;
      vlib_buffer_t * b0;

      bi0 = b[0];
      b += 1;
      n_left -= 1;

      b0 = vlib_get_buffer (vm, bi0);
      vnet_buffer (b0)->sw_if_index[VLIB_RX] = s->sw_if_index[VLIB_RX];
      /* s->sw_if_index[VLIB_TX]; */
      vnet_buffer (b0)->sw_if_index[VLIB_TX] = (u32)~0;

      if (set_data)
        clib_memcpy (b0->data, data, n_data);
      else
        ASSERT (validate_buffer_data2 (b0, s, data_offset, n_data));
    }
}

static void pg_buffer_init (vlib_main_t * vm,
                            vlib_buffer_free_list_t * fl,
                            u32 * buffers,
                            u32 n_buffers)
{
  pg_main_t * pg = &pg_main;
  pg_stream_t * s;
  uword bi, si;

  si = fl->buffer_init_function_opaque & pow2_mask (24);
  bi = fl->buffer_init_function_opaque >> 24;

  s = pool_elt_at_index (pg->streams, si);

  init_buffers_inline (vm, s, buffers, n_buffers,
                       /* data_offset */ bi * s->buffer_bytes,
                       /* n_data */ s->buffer_bytes,
                       /* set_data */ 1);
}

static u32
pg_stream_fill_helper (pg_main_t * pg,
                       pg_stream_t * s,
                       pg_buffer_index_t * bi,
                       u32 * buffers,
                       u32 * next_buffers,
                       u32 n_alloc)
{
  vlib_main_t * vm = pg->vlib_main;
  vlib_buffer_free_list_t * f;
  uword is_start_of_packet = bi == s->buffer_indices;
  u32 n_allocated;

  f = vlib_buffer_get_free_list (vm, bi->free_list_index);

  /* 
   * Historically, the pg maintained its own free lists and
   * device drivers tx paths would return pkts. With the DPDK,
   * that doesn't happen.
   */
  if (DPDK == 0 && ! (s->flags & PG_STREAM_FLAGS_DISABLE_BUFFER_RECYCLE))
    f->buffer_init_function = pg_buffer_init;
  f->buffer_init_function_opaque = 
    (s - pg->streams) | ((bi - s->buffer_indices) << 24);

  if (is_start_of_packet)
    vnet_buffer (&f->buffer_init_template)->sw_if_index[VLIB_RX] 
      = vnet_main.local_interface_sw_if_index;

  n_allocated = vlib_buffer_alloc_from_free_list (vm,
                                                  buffers,
                                                  n_alloc,
                                                  bi->free_list_index);
  if (n_allocated == 0)
    return 0;

  /* 
   * We can't assume we got all the buffers we asked for... 
   * This never worked until recently.
   */
  n_alloc = n_allocated;

  /* Reinitialize buffers */
  if (DPDK == 0 || CLIB_DEBUG > 0 
      || (s->flags & PG_STREAM_FLAGS_DISABLE_BUFFER_RECYCLE))
    init_buffers_inline
      (vm, s,
       buffers,
       n_alloc,
       (bi - s->buffer_indices) * s->buffer_bytes /* data offset */,
       s->buffer_bytes,
       /* set_data */
       DPDK == 1 || (s->flags & PG_STREAM_FLAGS_DISABLE_BUFFER_RECYCLE) != 0);
  
  /* $$$ this doesn't work at the moment */
  ASSERT(next_buffers == 0);
  if (next_buffers)
    pg_set_next_buffer_pointers (pg, s, buffers, next_buffers, n_alloc);

  if (is_start_of_packet)
    {
      if (vec_len (s->replay_packet_templates) > 0)
        {
          vnet_main_t * vnm = vnet_get_main();
          vnet_interface_main_t * im = &vnm->interface_main;
          vnet_sw_interface_t * si = 
            vnet_get_sw_interface (vnm, s->sw_if_index[VLIB_RX]);
          u32 l = 0;
          u32 i;
          for (i = 0; i < n_alloc; i++)
            l += vlib_buffer_index_length_in_chain (vm, buffers[i]);
          vlib_increment_combined_counter (im->combined_sw_if_counters
                                           + VNET_INTERFACE_COUNTER_RX,
                                           os_get_cpu_number(),
                                           si->sw_if_index,
                                           n_alloc,
                                           l);
          s->current_replay_packet_index += n_alloc;
          s->current_replay_packet_index %= 
            vec_len (s->replay_packet_templates);
        }
      else
        {
          pg_generate_set_lengths (pg, s, buffers, n_alloc);
          if (vec_len (s->buffer_indices) > 1)
            pg_generate_fix_multi_buffer_lengths (pg, s, buffers, n_alloc);

          pg_generate_edit (pg, s, buffers, n_alloc);
        }
    }

  return n_alloc;
}

static u32
pg_stream_fill (pg_main_t * pg, pg_stream_t * s, u32 n_buffers)
{
  pg_buffer_index_t * bi;
  word i, n_in_fifo, n_alloc, n_free, n_added;
  u32 * tail, * start, * end, * last_tail, * last_start;

  bi = s->buffer_indices;

  n_in_fifo = clib_fifo_elts (bi->buffer_fifo);
  if (n_in_fifo >= n_buffers)
    return n_in_fifo;

  n_alloc = n_buffers - n_in_fifo;

  /* Round up, but never generate more than limit. */
  n_alloc = clib_max (VLIB_FRAME_SIZE, n_alloc);

  if (s->n_packets_limit > 0
      && s->n_packets_generated + n_in_fifo + n_alloc >= s->n_packets_limit)
    {
      n_alloc = s->n_packets_limit - s->n_packets_generated - n_in_fifo;
      if (n_alloc < 0)
        n_alloc = 0;
    }

  /* All buffer fifos should have the same size. */
  if (CLIB_DEBUG > 0)
    {
      uword l = ~0, e;
      vec_foreach (bi, s->buffer_indices)
        {
          e = clib_fifo_elts (bi->buffer_fifo);
          if (bi == s->buffer_indices)
            l = e;
          ASSERT (l == e);
        }
    }

  last_tail = last_start = 0;
  n_added = n_alloc;

  for (i = vec_len (s->buffer_indices) - 1; i >= 0; i--)
    {
      bi = vec_elt_at_index (s->buffer_indices, i);

      n_free = clib_fifo_free_elts (bi->buffer_fifo);
      if (n_free < n_alloc)
        clib_fifo_resize (bi->buffer_fifo, n_alloc - n_free);

      tail = clib_fifo_advance_tail (bi->buffer_fifo, n_alloc);
      start = bi->buffer_fifo;
      end = clib_fifo_end (bi->buffer_fifo);

      if (tail + n_alloc <= end)
        {
          n_added = pg_stream_fill_helper (pg, s, bi, tail, last_tail, n_alloc);
        }
      else
        {
          u32 n = clib_min (end - tail, n_alloc);
          n_added = pg_stream_fill_helper (pg, s, bi, tail, last_tail, n);

          if (n_added == n && n_alloc > n_added)
            {
              n_added += pg_stream_fill_helper 
                (pg, s, bi, start, last_start, n_alloc - n_added);
            }
        }

      if (PREDICT_FALSE (n_added < n_alloc))
        tail = clib_fifo_advance_tail (bi->buffer_fifo, n_added - n_alloc);

      last_tail = tail;
      last_start = start;

      /* Verify that pkts in the fifo are properly allocated */
#if DPDK == 1
      if (CLIB_DEBUG > 0)
        {
          u32 *bi0;
          vlib_main_t * vm = vlib_get_main();
          clib_fifo_foreach (bi0, bi->buffer_fifo, 
          ({
            vlib_buffer_t * b;
            struct rte_mbuf *mb;

            b = vlib_get_buffer(vm, bi0[0]);
            mb = rte_mbuf_from_vlib_buffer(b);
            ASSERT(rte_mbuf_refcnt_read(mb) == 1);
          }));
        }
#endif
    }
  
  return n_in_fifo + n_added;
}

typedef struct {
  u32 stream_index;

  u32 packet_length;

  /* Use pre data for packet data. */
  vlib_buffer_t buffer;
} pg_input_trace_t;

static u8 * format_pg_input_trace (u8 * s, va_list * va)
{
  vlib_main_t * vm = va_arg (*va, vlib_main_t *);
  CLIB_UNUSED (vlib_node_t * node) = va_arg (*va, vlib_node_t *);
  pg_input_trace_t * t = va_arg (*va, pg_input_trace_t *);
  pg_main_t * pg = &pg_main;
  pg_stream_t * stream;
  vlib_node_t * n;
  uword indent = format_get_indent (s);

  stream = 0;
  if (! pool_is_free_index (pg->streams, t->stream_index))
    stream = pool_elt_at_index (pg->streams, t->stream_index);

  if (stream)
    s = format (s, "stream %v", pg->streams[t->stream_index].name);
  else
    s = format (s, "stream %d", t->stream_index);

  s = format (s, ", %d bytes", t->packet_length);

  s = format (s, "\n%U%U",
              format_white_space, indent,
              format_vlib_buffer, &t->buffer);

  s = format (s, "\n%U",
              format_white_space, indent);

  n = 0;
  if (stream)
    n = vlib_get_node (vm, stream->node_index);

  if (n && n->format_buffer)
    s = format (s, "%U", n->format_buffer,
                t->buffer.pre_data,
                sizeof (t->buffer.pre_data));
  else
    s = format (s, "%U", 
                format_hex_bytes, t->buffer.pre_data,
                ARRAY_LEN (t->buffer.pre_data));
  return s;
}

static void
pg_input_trace (pg_main_t * pg,
                vlib_node_runtime_t * node,
                pg_stream_t * s,
                u32 * buffers,
                u32 n_buffers)
{
  vlib_main_t * vm = pg->vlib_main;
  u32 * b, n_left, stream_index, next_index;

  n_left = n_buffers;
  b = buffers;
  stream_index = s - pg->streams;
  next_index = s->next_index;

  while (n_left >= 2)
    {
      u32 bi0, bi1;
      vlib_buffer_t * b0, * b1;
      pg_input_trace_t * t0, * t1;

      bi0 = b[0];
      bi1 = b[1];
      b += 2;
      n_left -= 2;

      b0 = vlib_get_buffer (vm, bi0);
      b1 = vlib_get_buffer (vm, bi1);

      vlib_trace_buffer (vm, node, next_index, b0, /* follow_chain */ 1);
      vlib_trace_buffer (vm, node, next_index, b1, /* follow_chain */ 1);

      t0 = vlib_add_trace (vm, node, b0, sizeof (t0[0]));
      t1 = vlib_add_trace (vm, node, b1, sizeof (t1[0]));

      t0->stream_index = stream_index;
      t1->stream_index = stream_index;

      t0->packet_length = vlib_buffer_length_in_chain (vm, b0);
      t1->packet_length = vlib_buffer_length_in_chain (vm, b1);

      clib_memcpy (&t0->buffer, b0, sizeof (b0[0]) - sizeof (b0->pre_data));
      clib_memcpy (&t1->buffer, b1, sizeof (b1[0]) - sizeof (b1->pre_data));

      clib_memcpy (t0->buffer.pre_data, b0->data, sizeof (t0->buffer.pre_data));
      clib_memcpy (t1->buffer.pre_data, b1->data, sizeof (t1->buffer.pre_data));
    }

  while (n_left >= 1)
    {
      u32 bi0;
      vlib_buffer_t * b0;
      pg_input_trace_t * t0;

      bi0 = b[0];
      b += 1;
      n_left -= 1;

      b0 = vlib_get_buffer (vm, bi0);

      vlib_trace_buffer (vm, node, next_index, b0, /* follow_chain */ 1);
      t0 = vlib_add_trace (vm, node, b0, sizeof (t0[0]));

      t0->stream_index = stream_index;
      t0->packet_length = vlib_buffer_length_in_chain (vm, b0);
      clib_memcpy (&t0->buffer, b0, sizeof (b0[0]) - sizeof (b0->pre_data));
      clib_memcpy (t0->buffer.pre_data, b0->data, sizeof (t0->buffer.pre_data));
    }
}

static uword
pg_generate_packets (vlib_node_runtime_t * node,
                     pg_main_t * pg,
                     pg_stream_t * s,
                     uword n_packets_to_generate)
{
  vlib_main_t * vm = pg->vlib_main;
  u32 * to_next, n_this_frame, n_left, n_trace, n_packets_in_fifo;
  uword n_packets_generated;
  pg_buffer_index_t * bi, * bi0;

  bi0 = s->buffer_indices;

  n_packets_in_fifo = pg_stream_fill (pg, s, n_packets_to_generate);
  n_packets_to_generate = clib_min (n_packets_in_fifo, n_packets_to_generate);
  n_packets_generated = 0;

  while (n_packets_to_generate > 0)
    {
      u32 * head, * start, * end;

      vlib_get_next_frame (vm, node, s->next_index, to_next, n_left);

      n_this_frame = n_packets_to_generate;
      if (n_this_frame > n_left)
        n_this_frame = n_left;

      start = bi0->buffer_fifo;
      end = clib_fifo_end (bi0->buffer_fifo);
      head = clib_fifo_head (bi0->buffer_fifo);

      if (head + n_this_frame <= end)
        vlib_copy_buffers (to_next, head, n_this_frame);
      else
        {
          u32 n = end - head;
          vlib_copy_buffers (to_next + 0, head, n);
          vlib_copy_buffers (to_next + n, start, n_this_frame - n);
        }

      vec_foreach (bi, s->buffer_indices)
        clib_fifo_advance_head (bi->buffer_fifo, n_this_frame);

      n_trace = vlib_get_trace_count (vm, node);
      if (n_trace > 0)
        {
          u32 n = clib_min (n_trace, n_this_frame);
          pg_input_trace (pg, node, s, to_next, n);
          vlib_set_trace_count (vm, node, n_trace - n);
        }
      n_packets_to_generate -= n_this_frame;
      n_packets_generated += n_this_frame;
      n_left -= n_this_frame;
      vlib_put_next_frame (vm, node, s->next_index, n_left);
    }

  return n_packets_generated;
}

static uword
pg_input_stream (vlib_node_runtime_t * node,
                 pg_main_t * pg,
                 pg_stream_t * s)
{
  vlib_main_t * vm = pg->vlib_main;
  uword n_packets;
  f64 time_now, dt;

  if (s->n_packets_limit > 0
      && s->n_packets_generated >= s->n_packets_limit)
    {
      pg_stream_enable_disable (pg, s, /* want_enabled */ 0);
      return 0;
    }

  /* Apply rate limit. */
  time_now = vlib_time_now (vm);
  if (s->time_last_generate == 0)
    s->time_last_generate = time_now;

  dt = time_now - s->time_last_generate;
  s->time_last_generate = time_now;

  n_packets = VLIB_FRAME_SIZE;
  if (s->rate_packets_per_second > 0)
    {
      s->packet_accumulator += dt * s->rate_packets_per_second;
      n_packets = s->packet_accumulator;

      /* Never allow accumulator to grow if we get behind. */
      s->packet_accumulator -= n_packets;
    }

  /* Apply fixed limit. */
  if (s->n_packets_limit > 0
      && s->n_packets_generated + n_packets > s->n_packets_limit)
    n_packets = s->n_packets_limit - s->n_packets_generated;

  /* Generate up to one frame's worth of packets. */
  if (n_packets > VLIB_FRAME_SIZE)
    n_packets = VLIB_FRAME_SIZE;

  if (n_packets > 0)
    n_packets = pg_generate_packets (node, pg, s, n_packets);

  s->n_packets_generated += n_packets;

  return n_packets;
}

uword
pg_input (vlib_main_t * vm,
          vlib_node_runtime_t * node,
          vlib_frame_t * frame)
{
  uword i;
  pg_main_t * pg = &pg_main;
  uword n_packets = 0;

  clib_bitmap_foreach (i, pg->enabled_streams, ({
    n_packets += pg_input_stream (node, pg, vec_elt_at_index (pg->streams, i));
  }));

  return n_packets;
}

VLIB_REGISTER_NODE (pg_input_node) = {
  .function = pg_input,
  .name = "pg-input",
  .type = VLIB_NODE_TYPE_INPUT,

  .format_trace = format_pg_input_trace,

  /* Input node will be left disabled until a stream is active. */
  .state = VLIB_NODE_STATE_DISABLED,
};