node.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.
 */
#include <vnet/vnet.h>
#include <vppinfra/vec.h>
#include <vppinfra/error.h>
#include <vppinfra/format.h>
#include <vppinfra/xxhash.h>

#include <vnet/ethernet/ethernet.h>
#include <vnet/devices/dpdk/dpdk.h>
#include <vnet/classify/vnet_classify.h>
#include <vnet/mpls/packet.h>
#include <vnet/handoff.h>
#include <vnet/devices/devices.h>
#include <vnet/feature/feature.h>

#include "dpdk_priv.h"

static char *dpdk_error_strings[] = {
#define _(n,s) s,
  foreach_dpdk_error
#undef _
};

always_inline int
vlib_buffer_is_ip4 (vlib_buffer_t * b)
{
  ethernet_header_t *h = (ethernet_header_t *) b->data;
  return (h->type == clib_host_to_net_u16 (ETHERNET_TYPE_IP4));
}

always_inline int
vlib_buffer_is_ip6 (vlib_buffer_t * b)
{
  ethernet_header_t *h = (ethernet_header_t *) b->data;
  return (h->type == clib_host_to_net_u16 (ETHERNET_TYPE_IP6));
}

always_inline int
vlib_buffer_is_mpls (vlib_buffer_t * b)
{
  ethernet_header_t *h = (ethernet_header_t *) b->data;
  return (h->type == clib_host_to_net_u16 (ETHERNET_TYPE_MPLS_UNICAST));
}

#if RTE_VERSION < RTE_VERSION_NUM(16, 11, 0, 0)
/* New ol_flags bits added in DPDK-16.11 */
#define PKT_RX_IP_CKSUM_GOOD    (1ULL << 7)
#endif

always_inline u32
dpdk_rx_next_from_etype (struct rte_mbuf * mb, vlib_buffer_t * b0)
{
  if (PREDICT_TRUE (vlib_buffer_is_ip4 (b0)))
    if (PREDICT_TRUE ((mb->ol_flags & PKT_RX_IP_CKSUM_GOOD) != 0))
      return VNET_DEVICE_INPUT_NEXT_IP4_NCS_INPUT;
    else
      return VNET_DEVICE_INPUT_NEXT_IP4_INPUT;
  else if (PREDICT_TRUE (vlib_buffer_is_ip6 (b0)))
    return VNET_DEVICE_INPUT_NEXT_IP6_INPUT;
  else if (PREDICT_TRUE (vlib_buffer_is_mpls (b0)))
    return VNET_DEVICE_INPUT_NEXT_MPLS_INPUT;
  else
    return VNET_DEVICE_INPUT_NEXT_ETHERNET_INPUT;
}

always_inline int
dpdk_mbuf_is_vlan (struct rte_mbuf *mb)
{
#if RTE_VERSION >= RTE_VERSION_NUM(16, 11, 0, 0)
  return (mb->packet_type & RTE_PTYPE_L2_ETHER_VLAN) ==
    RTE_PTYPE_L2_ETHER_VLAN;
#else
  return
    (mb->ol_flags &
     (PKT_RX_VLAN_PKT | PKT_RX_VLAN_STRIPPED | PKT_RX_QINQ_STRIPPED)) ==
    PKT_RX_VLAN_PKT;
#endif
}

always_inline int
dpdk_mbuf_is_ip4 (struct rte_mbuf *mb)
{
  return RTE_ETH_IS_IPV4_HDR (mb->packet_type) != 0;
}

always_inline int
dpdk_mbuf_is_ip6 (struct rte_mbuf *mb)
{
  return RTE_ETH_IS_IPV6_HDR (mb->packet_type) != 0;
}

always_inline u32
dpdk_rx_next_from_mb (struct rte_mbuf * mb, vlib_buffer_t * b0)
{
  if (PREDICT_FALSE (dpdk_mbuf_is_vlan (mb)))
    return VNET_DEVICE_INPUT_NEXT_ETHERNET_INPUT;
  else if (PREDICT_TRUE (dpdk_mbuf_is_ip4 (mb)))
    return VNET_DEVICE_INPUT_NEXT_IP4_NCS_INPUT;
  else if (PREDICT_TRUE (dpdk_mbuf_is_ip6 (mb)))
    return VNET_DEVICE_INPUT_NEXT_IP6_INPUT;
  else if (PREDICT_TRUE (vlib_buffer_is_mpls (b0)))
    return VNET_DEVICE_INPUT_NEXT_MPLS_INPUT;
  else
    return dpdk_rx_next_from_etype (mb, b0);
}

always_inline void
dpdk_rx_error_from_mb (struct rte_mbuf *mb, u32 * next, u8 * error)
{
  if (mb->ol_flags & PKT_RX_IP_CKSUM_BAD)
    {
      *error = DPDK_ERROR_IP_CHECKSUM_ERROR;
      *next = VNET_DEVICE_INPUT_NEXT_DROP;
    }
  else
    *error = DPDK_ERROR_NONE;
}

void
dpdk_rx_trace (dpdk_main_t * dm,
               vlib_node_runtime_t * node,
               dpdk_device_t * xd,
               u16 queue_id, u32 * buffers, uword n_buffers)
{
  vlib_main_t *vm = vlib_get_main ();
  u32 *b, n_left;
  u32 next0;

  n_left = n_buffers;
  b = buffers;

  while (n_left >= 1)
    {
      u32 bi0;
      vlib_buffer_t *b0;
      dpdk_rx_dma_trace_t *t0;
      struct rte_mbuf *mb;
      u8 error0;

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

      b0 = vlib_get_buffer (vm, bi0);
      mb = rte_mbuf_from_vlib_buffer (b0);

      if (PREDICT_FALSE (xd->per_interface_next_index != ~0))
        next0 = xd->per_interface_next_index;
      else if (PREDICT_TRUE
               ((xd->flags & DPDK_DEVICE_FLAG_PMD_SUPPORTS_PTYPE) != 0))
        next0 = dpdk_rx_next_from_mb (mb, b0);
      else
        next0 = dpdk_rx_next_from_etype (mb, b0);

      dpdk_rx_error_from_mb (mb, &next0, &error0);

      vlib_trace_buffer (vm, node, next0, b0, /* follow_chain */ 0);
      t0 = vlib_add_trace (vm, node, b0, sizeof (t0[0]));
      t0->queue_index = queue_id;
      t0->device_index = xd->device_index;
      t0->buffer_index = bi0;

      clib_memcpy (&t0->mb, mb, sizeof (t0->mb));
      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));
      clib_memcpy (&t0->data, mb->buf_addr + mb->data_off, sizeof (t0->data));

      b += 1;
    }
}

static inline u32
dpdk_rx_burst (dpdk_main_t * dm, dpdk_device_t * xd, u16 queue_id)
{
  u32 n_buffers;
  u32 n_left;
  u32 n_this_chunk;

  n_left = VLIB_FRAME_SIZE;
  n_buffers = 0;

  if (PREDICT_TRUE (xd->flags & DPDK_DEVICE_FLAG_PMD))
    {
      while (n_left)
        {
          n_this_chunk = rte_eth_rx_burst (xd->device_index, queue_id,
                                           xd->rx_vectors[queue_id] +
                                           n_buffers, n_left);
          n_buffers += n_this_chunk;
          n_left -= n_this_chunk;

          /* Empirically, DPDK r1.8 produces vectors w/ 32 or fewer elts */
          if (n_this_chunk < 32)
            break;
        }
    }
  else
    {
      ASSERT (0);
    }

  return n_buffers;
}


static_always_inline void
dpdk_process_subseq_segs (vlib_main_t * vm, vlib_buffer_t * b,
                          struct rte_mbuf *mb, vlib_buffer_free_list_t * fl)
{
  u8 nb_seg = 1;
  struct rte_mbuf *mb_seg = 0;
  vlib_buffer_t *b_seg, *b_chain = 0;
  mb_seg = mb->next;
  b_chain = b;

  while ((mb->nb_segs > 1) && (nb_seg < mb->nb_segs))
    {
      ASSERT (mb_seg != 0);

      b_seg = vlib_buffer_from_rte_mbuf (mb_seg);
      vlib_buffer_init_for_free_list (b_seg, fl);

      ASSERT ((b_seg->flags & VLIB_BUFFER_NEXT_PRESENT) == 0);
      ASSERT (b_seg->current_data == 0);

      /*
       * The driver (e.g. virtio) may not put the packet data at the start
       * of the segment, so don't assume b_seg->current_data == 0 is correct.
       */
      b_seg->current_data =
        (mb_seg->buf_addr + mb_seg->data_off) - (void *) b_seg->data;

      b_seg->current_length = mb_seg->data_len;
      b->total_length_not_including_first_buffer += mb_seg->data_len;

      b_chain->flags |= VLIB_BUFFER_NEXT_PRESENT;
      b_chain->next_buffer = vlib_get_buffer_index (vm, b_seg);

      b_chain = b_seg;
      mb_seg = mb_seg->next;
      nb_seg++;
    }
}

static_always_inline void
dpdk_prefetch_buffer (struct rte_mbuf *mb)
{
  vlib_buffer_t *b = vlib_buffer_from_rte_mbuf (mb);
  CLIB_PREFETCH (mb, CLIB_CACHE_LINE_BYTES, LOAD);
  CLIB_PREFETCH (b, CLIB_CACHE_LINE_BYTES, STORE);
}

/*
 * This function is used when there are no worker threads.
 * The main thread performs IO and forwards the packets.
 */
static_always_inline u32
dpdk_device_input (dpdk_main_t * dm, dpdk_device_t * xd,
                   vlib_node_runtime_t * node, u32 cpu_index, u16 queue_id)
{
  u32 n_buffers;
  u32 next_index = VNET_DEVICE_INPUT_NEXT_ETHERNET_INPUT;
  u32 n_left_to_next, *to_next;
  u32 mb_index;
  vlib_main_t *vm = vlib_get_main ();
  uword n_rx_bytes = 0;
  u32 n_trace, trace_cnt __attribute__ ((unused));
  vlib_buffer_free_list_t *fl;
  u32 buffer_flags_template;

  if ((xd->flags & DPDK_DEVICE_FLAG_ADMIN_UP) == 0)
    return 0;

  n_buffers = dpdk_rx_burst (dm, xd, queue_id);

  if (n_buffers == 0)
    {
      return 0;
    }

  buffer_flags_template = dm->buffer_flags_template;

  vec_reset_length (xd->d_trace_buffers[cpu_index]);
  trace_cnt = n_trace = vlib_get_trace_count (vm, node);

  if (n_trace > 0)
    {
      u32 n = clib_min (n_trace, n_buffers);
      mb_index = 0;

      while (n--)
        {
          struct rte_mbuf *mb = xd->rx_vectors[queue_id][mb_index++];
          vlib_buffer_t *b = vlib_buffer_from_rte_mbuf (mb);
          vec_add1 (xd->d_trace_buffers[cpu_index],
                    vlib_get_buffer_index (vm, b));
        }
    }

  fl = vlib_buffer_get_free_list (vm, VLIB_BUFFER_DEFAULT_FREE_LIST_INDEX);

  mb_index = 0;

  while (n_buffers > 0)
    {
      vlib_buffer_t *b0, *b1, *b2, *b3;
      u32 bi0, next0, l3_offset0;
      u32 bi1, next1, l3_offset1;
      u32 bi2, next2, l3_offset2;
      u32 bi3, next3, l3_offset3;
      u8 error0, error1, error2, error3;
      u64 or_ol_flags;

      vlib_get_next_frame (vm, node, next_index, to_next, n_left_to_next);

      while (n_buffers > 8 && n_left_to_next > 4)
        {
          struct rte_mbuf *mb0 = xd->rx_vectors[queue_id][mb_index];
          struct rte_mbuf *mb1 = xd->rx_vectors[queue_id][mb_index + 1];
          struct rte_mbuf *mb2 = xd->rx_vectors[queue_id][mb_index + 2];
          struct rte_mbuf *mb3 = xd->rx_vectors[queue_id][mb_index + 3];

          dpdk_prefetch_buffer (xd->rx_vectors[queue_id][mb_index + 4]);
          dpdk_prefetch_buffer (xd->rx_vectors[queue_id][mb_index + 5]);
          dpdk_prefetch_buffer (xd->rx_vectors[queue_id][mb_index + 6]);
          dpdk_prefetch_buffer (xd->rx_vectors[queue_id][mb_index + 7]);

          if (xd->flags & DPDK_DEVICE_FLAG_MAYBE_MULTISEG)
            {
              if (PREDICT_FALSE (mb0->nb_segs > 1))
                dpdk_prefetch_buffer (mb0->next);
              if (PREDICT_FALSE (mb1->nb_segs > 1))
                dpdk_prefetch_buffer (mb1->next);
              if (PREDICT_FALSE (mb2->nb_segs > 1))
                dpdk_prefetch_buffer (mb2->next);
              if (PREDICT_FALSE (mb3->nb_segs > 1))
                dpdk_prefetch_buffer (mb3->next);
            }

          ASSERT (mb0);
          ASSERT (mb1);
          ASSERT (mb2);
          ASSERT (mb3);

          or_ol_flags = (mb0->ol_flags | mb1->ol_flags |
                         mb2->ol_flags | mb3->ol_flags);
          b0 = vlib_buffer_from_rte_mbuf (mb0);
          b1 = vlib_buffer_from_rte_mbuf (mb1);
          b2 = vlib_buffer_from_rte_mbuf (mb2);
          b3 = vlib_buffer_from_rte_mbuf (mb3);

          vlib_buffer_init_for_free_list (b0, fl);
          vlib_buffer_init_for_free_list (b1, fl);
          vlib_buffer_init_for_free_list (b2, fl);
          vlib_buffer_init_for_free_list (b3, fl);

          bi0 = vlib_get_buffer_index (vm, b0);
          bi1 = vlib_get_buffer_index (vm, b1);
          bi2 = vlib_get_buffer_index (vm, b2);
          bi3 = vlib_get_buffer_index (vm, b3);

          to_next[0] = bi0;
          to_next[1] = bi1;
          to_next[2] = bi2;
          to_next[3] = bi3;
          to_next += 4;
          n_left_to_next -= 4;

          if (PREDICT_FALSE (xd->per_interface_next_index != ~0))
            {
              next0 = next1 = next2 = next3 = xd->per_interface_next_index;
            }
          else if (PREDICT_TRUE
                   ((xd->flags & DPDK_DEVICE_FLAG_PMD_SUPPORTS_PTYPE) != 0))
            {
              next0 = dpdk_rx_next_from_mb (mb0, b0);
              next1 = dpdk_rx_next_from_mb (mb1, b1);
              next2 = dpdk_rx_next_from_mb (mb2, b2);
              next3 = dpdk_rx_next_from_mb (mb3, b3);
            }
          else
            {
              next0 = dpdk_rx_next_from_etype (mb0, b0);
              next1 = dpdk_rx_next_from_etype (mb1, b1);
              next2 = dpdk_rx_next_from_etype (mb2, b2);
              next3 = dpdk_rx_next_from_etype (mb3, b3);
            }

          if (PREDICT_FALSE (or_ol_flags & PKT_RX_IP_CKSUM_BAD))
            {
              dpdk_rx_error_from_mb (mb0, &next0, &error0);
              dpdk_rx_error_from_mb (mb1, &next1, &error1);
              dpdk_rx_error_from_mb (mb2, &next2, &error2);
              dpdk_rx_error_from_mb (mb3, &next3, &error3);
              b0->error = node->errors[error0];
              b1->error = node->errors[error1];
              b2->error = node->errors[error2];
              b3->error = node->errors[error3];
            }
          else
            {
              b0->error = b1->error = node->errors[DPDK_ERROR_NONE];
              b2->error = b3->error = node->errors[DPDK_ERROR_NONE];
            }

          l3_offset0 = device_input_next_node_advance[next0];
          l3_offset1 = device_input_next_node_advance[next1];
          l3_offset2 = device_input_next_node_advance[next2];
          l3_offset3 = device_input_next_node_advance[next3];

          b0->current_data = l3_offset0 + mb0->data_off;
          b1->current_data = l3_offset1 + mb1->data_off;
          b2->current_data = l3_offset2 + mb2->data_off;
          b3->current_data = l3_offset3 + mb3->data_off;

          b0->current_data -= RTE_PKTMBUF_HEADROOM;
          b1->current_data -= RTE_PKTMBUF_HEADROOM;
          b2->current_data -= RTE_PKTMBUF_HEADROOM;
          b3->current_data -= RTE_PKTMBUF_HEADROOM;

          b0->current_length = mb0->data_len - l3_offset0;
          b1->current_length = mb1->data_len - l3_offset1;
          b2->current_length = mb2->data_len - l3_offset2;
          b3->current_length = mb3->data_len - l3_offset3;

          b0->flags = buffer_flags_template;
          b1->flags = buffer_flags_template;
          b2->flags = buffer_flags_template;
          b3->flags = buffer_flags_template;

          vnet_buffer (b0)->sw_if_index[VLIB_RX] = xd->vlib_sw_if_index;
          vnet_buffer (b1)->sw_if_index[VLIB_RX] = xd->vlib_sw_if_index;
          vnet_buffer (b2)->sw_if_index[VLIB_RX] = xd->vlib_sw_if_index;
          vnet_buffer (b3)->sw_if_index[VLIB_RX] = xd->vlib_sw_if_index;

          vnet_buffer (b0)->sw_if_index[VLIB_TX] = (u32) ~ 0;
          vnet_buffer (b1)->sw_if_index[VLIB_TX] = (u32) ~ 0;
          vnet_buffer (b2)->sw_if_index[VLIB_TX] = (u32) ~ 0;
          vnet_buffer (b3)->sw_if_index[VLIB_TX] = (u32) ~ 0;

          n_rx_bytes += mb0->pkt_len;
          n_rx_bytes += mb1->pkt_len;
          n_rx_bytes += mb2->pkt_len;
          n_rx_bytes += mb3->pkt_len;

          /* Process subsequent segments of multi-segment packets */
          if (xd->flags & DPDK_DEVICE_FLAG_MAYBE_MULTISEG)
            {
              dpdk_process_subseq_segs (vm, b0, mb0, fl);
              dpdk_process_subseq_segs (vm, b1, mb1, fl);
              dpdk_process_subseq_segs (vm, b2, mb2, fl);
              dpdk_process_subseq_segs (vm, b3, mb3, fl);
            }

          /*
           * Turn this on if you run into
           * "bad monkey" contexts, and you want to know exactly
           * which nodes they've visited... See main.c...
           */
          VLIB_BUFFER_TRACE_TRAJECTORY_INIT (b0);
          VLIB_BUFFER_TRACE_TRAJECTORY_INIT (b1);
          VLIB_BUFFER_TRACE_TRAJECTORY_INIT (b2);
          VLIB_BUFFER_TRACE_TRAJECTORY_INIT (b3);

          /* Do we have any driver RX features configured on the interface? */
          vnet_feature_start_device_input_x4 (xd->vlib_sw_if_index,
                                              &next0, &next1, &next2, &next3,
                                              b0, b1, b2, b3,
                                              l3_offset0, l3_offset1,
                                              l3_offset2, l3_offset3);

          vlib_validate_buffer_enqueue_x4 (vm, node, next_index,
                                           to_next, n_left_to_next,
                                           bi0, bi1, bi2, bi3,
                                           next0, next1, next2, next3);
          n_buffers -= 4;
          mb_index += 4;
        }
      while (n_buffers > 0 && n_left_to_next > 0)
        {
          struct rte_mbuf *mb0 = xd->rx_vectors[queue_id][mb_index];

          ASSERT (mb0);

          b0 = vlib_buffer_from_rte_mbuf (mb0);

          /* Prefetch one next segment if it exists. */
          if (PREDICT_FALSE (mb0->nb_segs > 1))
            dpdk_prefetch_buffer (mb0->next);

          vlib_buffer_init_for_free_list (b0, fl);

          bi0 = vlib_get_buffer_index (vm, b0);

          to_next[0] = bi0;
          to_next++;
          n_left_to_next--;

          if (PREDICT_FALSE (xd->per_interface_next_index != ~0))
            next0 = xd->per_interface_next_index;
          else if (PREDICT_TRUE
                   ((xd->flags & DPDK_DEVICE_FLAG_PMD_SUPPORTS_PTYPE) != 0))
            next0 = dpdk_rx_next_from_mb (mb0, b0);
          else
            next0 = dpdk_rx_next_from_etype (mb0, b0);

          dpdk_rx_error_from_mb (mb0, &next0, &error0);
          b0->error = node->errors[error0];

          l3_offset0 = device_input_next_node_advance[next0];

          b0->current_data = l3_offset0;
          b0->current_data += mb0->data_off - RTE_PKTMBUF_HEADROOM;
          b0->current_length = mb0->data_len - l3_offset0;

          b0->flags = buffer_flags_template;

          vnet_buffer (b0)->sw_if_index[VLIB_RX] = xd->vlib_sw_if_index;
          vnet_buffer (b0)->sw_if_index[VLIB_TX] = (u32) ~ 0;
          n_rx_bytes += mb0->pkt_len;

          /* Process subsequent segments of multi-segment packets */
          dpdk_process_subseq_segs (vm, b0, mb0, fl);

          /*
           * Turn this on if you run into
           * "bad monkey" contexts, and you want to know exactly
           * which nodes they've visited... See main.c...
           */
          VLIB_BUFFER_TRACE_TRAJECTORY_INIT (b0);

          /* Do we have any driver RX features configured on the interface? */
          vnet_feature_start_device_input_x1 (xd->vlib_sw_if_index, &next0,
                                              b0, l3_offset0);

          vlib_validate_buffer_enqueue_x1 (vm, node, next_index,
                                           to_next, n_left_to_next,
                                           bi0, next0);
          n_buffers--;
          mb_index++;
        }
      vlib_put_next_frame (vm, node, next_index, n_left_to_next);
    }

  if (PREDICT_FALSE (vec_len (xd->d_trace_buffers[cpu_index]) > 0))
    {
      dpdk_rx_trace (dm, node, xd, queue_id, xd->d_trace_buffers[cpu_index],
                     vec_len (xd->d_trace_buffers[cpu_index]));
      vlib_set_trace_count (vm, node, n_trace -
                            vec_len (xd->d_trace_buffers[cpu_index]));
    }

  vlib_increment_combined_counter
    (vnet_get_main ()->interface_main.combined_sw_if_counters
     + VNET_INTERFACE_COUNTER_RX,
     cpu_index, xd->vlib_sw_if_index, mb_index, n_rx_bytes);

  dpdk_worker_t *dw = vec_elt_at_index (dm->workers, cpu_index);
  dw->aggregate_rx_packets += mb_index;

  return mb_index;
}

static inline void
poll_rate_limit (dpdk_main_t * dm)
{
  /* Limit the poll rate by sleeping for N msec between polls */
  if (PREDICT_FALSE (dm->poll_sleep != 0))
    {
      struct timespec ts, tsrem;

      ts.tv_sec = 0;
      ts.tv_nsec = 1000 * 1000 * dm->poll_sleep;        /* 1ms */

      while (nanosleep (&ts, &tsrem) < 0)
        {
          ts = tsrem;
        }
    }
}

/** \brief Main DPDK input node
    @node dpdk-input

    This is the main DPDK input node: across each assigned interface,
    call rte_eth_rx_burst(...) or similar to obtain a vector of
    packets to process. Handle early packet discard. Derive @c
    vlib_buffer_t metadata from <code>struct rte_mbuf</code> metadata,
    Depending on the resulting metadata: adjust <code>b->current_data,
    b->current_length </code> and dispatch directly to
    ip4-input-no-checksum, or ip6-input. Trace the packet if required.

    @param vm   vlib_main_t corresponding to the current thread
    @param node vlib_node_runtime_t
    @param f    vlib_frame_t input-node, not used.

    @par Graph mechanics: buffer metadata, next index usage

    @em Uses:
    - <code>struct rte_mbuf mb->ol_flags</code>
        - PKT_RX_IP_CKSUM_BAD
    - <code> RTE_ETH_IS_xxx_HDR(mb->packet_type) </code>
        - packet classification result

    @em Sets:
    - <code>b->error</code> if the packet is to be dropped immediately
    - <code>b->current_data, b->current_length</code>
        - adjusted as needed to skip the L2 header in  direct-dispatch cases
    - <code>vnet_buffer(b)->sw_if_index[VLIB_RX]</code>
        - rx interface sw_if_index
    - <code>vnet_buffer(b)->sw_if_index[VLIB_TX] = ~0</code>
        - required by ipX-lookup
    - <code>b->flags</code>
        - to indicate multi-segment pkts (VLIB_BUFFER_NEXT_PRESENT), etc.

    <em>Next Nodes:</em>
    - Static arcs to: error-drop, ethernet-input,
      ip4-input-no-checksum, ip6-input, mpls-input
    - per-interface redirection, controlled by
      <code>xd->per_interface_next_index</code>
*/

static uword
dpdk_input (vlib_main_t * vm, vlib_node_runtime_t * node, vlib_frame_t * f)
{
  dpdk_main_t *dm = &dpdk_main;
  dpdk_device_t *xd;
  uword n_rx_packets = 0;
  dpdk_device_and_queue_t *dq;
  u32 cpu_index = os_get_cpu_number ();

  /*
   * Poll all devices on this cpu for input/interrupts.
   */
  /* *INDENT-OFF* */
  vec_foreach (dq, dm->devices_by_cpu[cpu_index])
    {
      xd = vec_elt_at_index(dm->devices, dq->device);
      n_rx_packets += dpdk_device_input (dm, xd, node, cpu_index, dq->queue_id);
    }
  /* *INDENT-ON* */

  poll_rate_limit (dm);

  return n_rx_packets;
}

/* *INDENT-OFF* */
VLIB_REGISTER_NODE (dpdk_input_node) = {
  .function = dpdk_input,
  .type = VLIB_NODE_TYPE_INPUT,
  .name = "dpdk-input",
  .sibling_of = "device-input",

  /* Will be enabled if/when hardware is detected. */
  .state = VLIB_NODE_STATE_DISABLED,

  .format_buffer = format_ethernet_header_with_length,
  .format_trace = format_dpdk_rx_dma_trace,

  .n_errors = DPDK_N_ERROR,
  .error_strings = dpdk_error_strings,
};

VLIB_NODE_FUNCTION_MULTIARCH (dpdk_input_node, dpdk_input);
/* *INDENT-ON* */

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