node.c

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/*
 * Copyright (c) 2018 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 <vlib/vlib.h>
#include <vnet/vnet.h>
#include <vppinfra/error.h>
#include <vnet/ethernet/ethernet.h>
#include <vnet/feature/feature.h>
#include <vnet/gso/gso.h>
#include <vnet/gso/hdr_offset_parser.h>
#include <vnet/ip/icmp46_packet.h>
#include <vnet/ip/ip4.h>
#include <vnet/ip/ip6.h>
#include <vnet/udp/udp_packet.h>

typedef struct
{
  u32 flags;
  u16 gso_size;
  u8 gso_l4_hdr_sz;
  generic_header_offset_t gho;
} gso_trace_t;

static u8 *
format_gso_trace (u8 * s, va_list * args)
{
  CLIB_UNUSED (vlib_main_t * vm) = va_arg (*args, vlib_main_t *);
  CLIB_UNUSED (vlib_node_t * node) = va_arg (*args, vlib_node_t *);
  gso_trace_t *t = va_arg (*args, gso_trace_t *);

  if (t->flags & VNET_BUFFER_F_GSO)
    {
      s = format (s, "gso_sz %d gso_l4_hdr_sz %d\n%U",
                  t->gso_size, t->gso_l4_hdr_sz, format_generic_header_offset,
                  &t->gho);
    }
  else
    {
      s =
        format (s, "non-gso buffer\n%U", format_generic_header_offset,
                &t->gho);
    }

  return s;
}

static_always_inline u16
tso_segment_ipip_tunnel_fixup (vlib_main_t * vm,
                               vnet_interface_per_thread_data_t * ptd,
                               vlib_buffer_t * sb0,
                               generic_header_offset_t * gho)
{
  u16 n_tx_bufs = vec_len (ptd->split_buffers);
  u16 i = 0, n_tx_bytes = 0;

  while (i < n_tx_bufs)
    {
      vlib_buffer_t *b0 = vlib_get_buffer (vm, ptd->split_buffers[i]);
      vnet_get_outer_header (b0, gho);
      clib_memcpy_fast (vlib_buffer_get_current (b0),
                        vlib_buffer_get_current (sb0), gho->outer_hdr_sz);

      ip4_header_t *ip4 =
        (ip4_header_t *) (vlib_buffer_get_current (b0) +
                          gho->outer_l3_hdr_offset);
      ip6_header_t *ip6 =
        (ip6_header_t *) (vlib_buffer_get_current (b0) +
                          gho->outer_l3_hdr_offset);

      if (gho->gho_flags & GHO_F_OUTER_IP4)
        {
          ip4->length =
            clib_host_to_net_u16 (b0->current_length -
                                  gho->outer_l3_hdr_offset);
          ip4->checksum = ip4_header_checksum (ip4);
        }
      else if (gho->gho_flags & GHO_F_OUTER_IP6)
        {
          ip6->payload_length =
            clib_host_to_net_u16 (b0->current_length -
                                  gho->outer_l4_hdr_offset);
        }

      n_tx_bytes += gho->outer_hdr_sz;
      i++;
    }
  return n_tx_bytes;
}

static_always_inline void
tso_segment_vxlan_tunnel_headers_fixup (vlib_main_t * vm, vlib_buffer_t * b,
                                        generic_header_offset_t * gho)
{
  u8 proto = 0;
  ip4_header_t *ip4 = 0;
  ip6_header_t *ip6 = 0;
  udp_header_t *udp = 0;

  ip4 =
    (ip4_header_t *) (vlib_buffer_get_current (b) + gho->outer_l3_hdr_offset);
  ip6 =
    (ip6_header_t *) (vlib_buffer_get_current (b) + gho->outer_l3_hdr_offset);
  udp =
    (udp_header_t *) (vlib_buffer_get_current (b) + gho->outer_l4_hdr_offset);

  if (gho->gho_flags & GHO_F_OUTER_IP4)
    {
      proto = ip4->protocol;
      ip4->length =
        clib_host_to_net_u16 (b->current_length - gho->outer_l3_hdr_offset);
      ip4->checksum = ip4_header_checksum (ip4);
    }
  else if (gho->gho_flags & GHO_F_OUTER_IP6)
    {
      proto = ip6->protocol;
      ip6->payload_length =
        clib_host_to_net_u16 (b->current_length - gho->outer_l4_hdr_offset);
    }
  if (proto == IP_PROTOCOL_UDP)
    {
      int bogus;
      udp->length =
        clib_host_to_net_u16 (b->current_length - gho->outer_l4_hdr_offset);
      udp->checksum = 0;
      if (gho->gho_flags & GHO_F_OUTER_IP6)
        {
          udp->checksum =
            ip6_tcp_udp_icmp_compute_checksum (vm, b, ip6, &bogus);
        }
      else if (gho->gho_flags & GHO_F_OUTER_IP4)
        {
          udp->checksum = ip4_tcp_udp_compute_checksum (vm, b, ip4);
        }
      /* FIXME: it should be OUTER_UDP_CKSUM */
      vnet_buffer_offload_flags_clear (b, VNET_BUFFER_OFFLOAD_F_UDP_CKSUM);
    }
}

static_always_inline u16
tso_segment_vxlan_tunnel_fixup (vlib_main_t * vm,
                                vnet_interface_per_thread_data_t * ptd,
                                vlib_buffer_t * sb0,
                                generic_header_offset_t * gho)
{
  u16 n_tx_bufs = vec_len (ptd->split_buffers);
  u16 i = 0, n_tx_bytes = 0;

  while (i < n_tx_bufs)
    {
      vlib_buffer_t *b0 = vlib_get_buffer (vm, ptd->split_buffers[i]);
      vnet_get_outer_header (b0, gho);
      clib_memcpy_fast (vlib_buffer_get_current (b0),
                        vlib_buffer_get_current (sb0), gho->outer_hdr_sz);

      tso_segment_vxlan_tunnel_headers_fixup (vm, b0, gho);
      n_tx_bytes += gho->outer_hdr_sz;
      i++;
    }
  return n_tx_bytes;
}

static_always_inline u16
tso_alloc_tx_bufs (vlib_main_t * vm,
                   vnet_interface_per_thread_data_t * ptd,
                   vlib_buffer_t * b0, u32 n_bytes_b0, u16 l234_sz,
                   u16 gso_size, u16 first_data_size,
                   generic_header_offset_t * gho)
{
  u16 n_alloc, size;
  u16 first_packet_length = l234_sz + first_data_size;

  /*
   * size is the amount of data per segmented buffer except the 1st
   * segmented buffer.
   * l2_hdr_offset is an offset == current_data of vlib_buffer_t.
   * l234_sz is hdr_sz from l2_hdr_offset.
   */
  size =
    clib_min (gso_size, vlib_buffer_get_default_data_size (vm) - l234_sz
              - gho->l2_hdr_offset);

  /*
   * First segmented buffer length is calculated separately.
   * As it may contain less data than gso_size (when gso_size is
   * greater than current_length of 1st buffer from GSO chained
   * buffers) and/or size calculated above.
   */
  u16 n_bufs = 1;

  /*
   * Total packet length minus first packet length including l234 header.
   * rounded-up division
   */
  ASSERT (n_bytes_b0 > first_packet_length);
  n_bufs += ((n_bytes_b0 - first_packet_length + (size - 1)) / size);

  vec_validate (ptd->split_buffers, n_bufs - 1);

  n_alloc = vlib_buffer_alloc (vm, ptd->split_buffers, n_bufs);
  if (n_alloc < n_bufs)
    {
      vlib_buffer_free (vm, ptd->split_buffers, n_alloc);
      return 0;
    }
  return n_alloc;
}

static_always_inline void
tso_init_buf_from_template_base (vlib_buffer_t * nb0, vlib_buffer_t * b0,
                                 u32 flags, u16 length)
{
  /* copying objects from cacheline 0 */
  nb0->current_data = b0->current_data;
  nb0->current_length = length;
  nb0->flags = VLIB_BUFFER_TOTAL_LENGTH_VALID | flags;
  nb0->flow_id = b0->flow_id;
  nb0->error = b0->error;
  nb0->current_config_index = b0->current_config_index;
  clib_memcpy_fast (&nb0->opaque, &b0->opaque, sizeof (nb0->opaque));

  /* copying objects from cacheline 1 */
  nb0->trace_handle = b0->trace_handle;
  nb0->total_length_not_including_first_buffer = 0;

  /* copying data */
  clib_memcpy_fast (vlib_buffer_get_current (nb0),
                    vlib_buffer_get_current (b0), length);
}

static_always_inline void
tso_init_buf_from_template (vlib_main_t * vm, vlib_buffer_t * nb0,
                            vlib_buffer_t * b0, u16 template_data_sz,
                            u16 gso_size, u8 ** p_dst_ptr, u16 * p_dst_left,
                            u32 next_tcp_seq, u32 flags,
                            generic_header_offset_t * gho)
{
  tso_init_buf_from_template_base (nb0, b0, flags, template_data_sz);

  *p_dst_left =
    clib_min (gso_size,
              vlib_buffer_get_default_data_size (vm) - (template_data_sz +
                                                        nb0->current_data));
  *p_dst_ptr = vlib_buffer_get_current (nb0) + template_data_sz;

  tcp_header_t *tcp =
    (tcp_header_t *) (vlib_buffer_get_current (nb0) + gho->l4_hdr_offset);
  tcp->seq_number = clib_host_to_net_u32 (next_tcp_seq);
}

static_always_inline void
tso_fixup_segmented_buf (vlib_main_t * vm, vlib_buffer_t * b0, u8 tcp_flags,
                         int is_l2, int is_ip6, generic_header_offset_t * gho)
{
  ip4_header_t *ip4 =
    (ip4_header_t *) (vlib_buffer_get_current (b0) + gho->l3_hdr_offset);
  ip6_header_t *ip6 =
    (ip6_header_t *) (vlib_buffer_get_current (b0) + gho->l3_hdr_offset);
  tcp_header_t *tcp =
    (tcp_header_t *) (vlib_buffer_get_current (b0) + gho->l4_hdr_offset);

  tcp->flags = tcp_flags;

  if (is_ip6)
    {
      ip6->payload_length =
        clib_host_to_net_u16 (b0->current_length - gho->l4_hdr_offset);
      if (gho->gho_flags & GHO_F_TCP)
        {
          int bogus = 0;
          tcp->checksum = 0;
          tcp->checksum =
            ip6_tcp_udp_icmp_compute_checksum (vm, b0, ip6, &bogus);
          vnet_buffer_offload_flags_clear (b0,
                                           VNET_BUFFER_OFFLOAD_F_TCP_CKSUM);
        }
    }
  else
    {
      ip4->length =
        clib_host_to_net_u16 (b0->current_length - gho->l3_hdr_offset);
      if (gho->gho_flags & GHO_F_IP4)
        ip4->checksum = ip4_header_checksum (ip4);
      if (gho->gho_flags & GHO_F_TCP)
        {
          tcp->checksum = 0;
          tcp->checksum = ip4_tcp_udp_compute_checksum (vm, b0, ip4);
        }
      vnet_buffer_offload_flags_clear (b0, (VNET_BUFFER_OFFLOAD_F_IP_CKSUM |
                                            VNET_BUFFER_OFFLOAD_F_TCP_CKSUM));
    }

  if (!is_l2 && ((gho->gho_flags & GHO_F_TUNNEL) == 0))
    {
      u32 adj_index0 = vnet_buffer (b0)->ip.adj_index[VLIB_TX];

      ip_adjacency_t *adj0 = adj_get (adj_index0);

      if (adj0->lookup_next_index == IP_LOOKUP_NEXT_MIDCHAIN &&
          adj0->sub_type.midchain.fixup_func)
        /* calls e.g. ipip44_fixup */
        adj0->sub_type.midchain.fixup_func
          (vm, adj0, b0, adj0->sub_type.midchain.fixup_data);
    }
}

/**
 * Allocate the necessary number of ptd->split_buffers,
 * and segment the possibly chained buffer(s) from b0 into
 * there.
 *
 * Return the cumulative number of bytes sent or zero
 * if allocation failed.
 */

static_always_inline u32
tso_segment_buffer (vlib_main_t * vm, vnet_interface_per_thread_data_t * ptd,
                    u32 sbi0, vlib_buffer_t * sb0,
                    generic_header_offset_t * gho, u32 n_bytes_b0, int is_l2,
                    int is_ip6)
{
  u32 n_tx_bytes = 0;
  u16 gso_size = vnet_buffer2 (sb0)->gso_size;

  u8 save_tcp_flags = 0;
  u8 tcp_flags_no_fin_psh = 0;
  u32 next_tcp_seq = 0;

  tcp_header_t *tcp =
    (tcp_header_t *) (vlib_buffer_get_current (sb0) + gho->l4_hdr_offset);
  next_tcp_seq = clib_net_to_host_u32 (tcp->seq_number);
  /* store original flags for last packet and reset FIN and PSH */
  save_tcp_flags = tcp->flags;
  tcp_flags_no_fin_psh = tcp->flags & ~(TCP_FLAG_FIN | TCP_FLAG_PSH);
  tcp->checksum = 0;

  u32 default_bflags =
    sb0->flags & ~(VNET_BUFFER_F_GSO | VLIB_BUFFER_NEXT_PRESENT);
  u16 l234_sz = gho->hdr_sz;
  int first_data_size = clib_min (gso_size, sb0->current_length - l234_sz);
  next_tcp_seq += first_data_size;

  if (PREDICT_FALSE
      (!tso_alloc_tx_bufs
       (vm, ptd, sb0, n_bytes_b0, l234_sz, gso_size, first_data_size, gho)))
    return 0;

  vlib_buffer_t *b0 = vlib_get_buffer (vm, ptd->split_buffers[0]);
  tso_init_buf_from_template_base (b0, sb0, default_bflags,
                                   l234_sz + first_data_size);

  u32 total_src_left = n_bytes_b0 - l234_sz - first_data_size;
  if (total_src_left)
    {
      /* Need to copy more segments */
      u8 *src_ptr, *dst_ptr;
      u16 src_left, dst_left;
      /* current source buffer */
      vlib_buffer_t *csb0 = sb0;
      u32 csbi0 = sbi0;
      /* current dest buffer */
      vlib_buffer_t *cdb0;
      u16 dbi = 1;              /* the buffer [0] is b0 */

      src_ptr = vlib_buffer_get_current (sb0) + l234_sz + first_data_size;
      src_left = sb0->current_length - l234_sz - first_data_size;

      tso_fixup_segmented_buf (vm, b0, tcp_flags_no_fin_psh, is_l2, is_ip6,
                               gho);

      /* grab a second buffer and prepare the loop */
      ASSERT (dbi < vec_len (ptd->split_buffers));
      cdb0 = vlib_get_buffer (vm, ptd->split_buffers[dbi++]);
      tso_init_buf_from_template (vm, cdb0, b0, l234_sz, gso_size, &dst_ptr,
                                  &dst_left, next_tcp_seq, default_bflags,
                                  gho);

      /* an arbitrary large number to catch the runaway loops */
      int nloops = 2000;
      while (total_src_left)
        {
          if (nloops-- <= 0)
            clib_panic ("infinite loop detected");
          u16 bytes_to_copy = clib_min (src_left, dst_left);

          clib_memcpy_fast (dst_ptr, src_ptr, bytes_to_copy);

          src_left -= bytes_to_copy;
          src_ptr += bytes_to_copy;
          total_src_left -= bytes_to_copy;
          dst_left -= bytes_to_copy;
          dst_ptr += bytes_to_copy;
          next_tcp_seq += bytes_to_copy;
          cdb0->current_length += bytes_to_copy;

          if (0 == src_left)
            {
              int has_next = (csb0->flags & VLIB_BUFFER_NEXT_PRESENT);
              u32 next_bi = csb0->next_buffer;

              /* init src to the next buffer in chain */
              if (has_next)
                {
                  csbi0 = next_bi;
                  csb0 = vlib_get_buffer (vm, csbi0);
                  src_left = csb0->current_length;
                  src_ptr = vlib_buffer_get_current (csb0);
                }
              else
                {
                  ASSERT (total_src_left == 0);
                  break;
                }
            }
          if (0 == dst_left && total_src_left)
            {
              n_tx_bytes += cdb0->current_length;
              tso_fixup_segmented_buf (vm, cdb0, tcp_flags_no_fin_psh, is_l2,
                                       is_ip6, gho);
              ASSERT (dbi < vec_len (ptd->split_buffers));
              cdb0 = vlib_get_buffer (vm, ptd->split_buffers[dbi++]);
              tso_init_buf_from_template (vm, cdb0, b0, l234_sz,
                                          gso_size, &dst_ptr, &dst_left,
                                          next_tcp_seq, default_bflags, gho);
            }
        }

      tso_fixup_segmented_buf (vm, cdb0, save_tcp_flags, is_l2, is_ip6, gho);

      n_tx_bytes += cdb0->current_length;
    }
  n_tx_bytes += b0->current_length;
  return n_tx_bytes;
}

static_always_inline void
drop_one_buffer_and_count (vlib_main_t * vm, vnet_main_t * vnm,
                           vlib_node_runtime_t * node, u32 * pbi0,
                           u32 sw_if_index, u32 drop_error_code)
{
  u32 thread_index = vm->thread_index;

  vlib_simple_counter_main_t *cm;
  cm =
    vec_elt_at_index (vnm->interface_main.sw_if_counters,
                      VNET_INTERFACE_COUNTER_TX_ERROR);
  vlib_increment_simple_counter (cm, thread_index, sw_if_index, 1);

  vlib_error_drop_buffers (vm, node, pbi0,
                           /* buffer stride */ 1,
                           /* n_buffers */ 1,
                           VNET_INTERFACE_OUTPUT_NEXT_DROP,
                           node->node_index, drop_error_code);
}

static_always_inline uword
vnet_gso_node_inline (vlib_main_t * vm,
                      vlib_node_runtime_t * node,
                      vlib_frame_t * frame,
                      vnet_main_t * vnm,
                      vnet_hw_interface_t * hi,
                      int is_l2, int is_ip4, int is_ip6, int do_segmentation)
{
  u32 *to_next;
  u32 next_index = node->cached_next_index;
  u32 *from = vlib_frame_vector_args (frame);
  u32 n_left_from = frame->n_vectors;
  u32 *from_end = from + n_left_from;
  u32 thread_index = vm->thread_index;
  vnet_interface_main_t *im = &vnm->interface_main;
  vnet_interface_per_thread_data_t *ptd =
    vec_elt_at_index (im->per_thread_data, thread_index);
  vlib_buffer_t *bufs[VLIB_FRAME_SIZE], **b = bufs;

  vlib_get_buffers (vm, from, b, n_left_from);

  while (n_left_from > 0)
    {
      u32 n_left_to_next;

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

      if (!do_segmentation)
        while (from + 8 <= from_end && n_left_to_next >= 4)
          {
            u32 bi0, bi1, bi2, bi3;
            u32 next0, next1, next2, next3;
            u32 swif0, swif1, swif2, swif3;
            gso_trace_t *t0, *t1, *t2, *t3;
            vnet_hw_interface_t *hi0, *hi1, *hi2, *hi3;

            /* Prefetch next iteration. */
            vlib_prefetch_buffer_header (b[4], LOAD);
            vlib_prefetch_buffer_header (b[5], LOAD);
            vlib_prefetch_buffer_header (b[6], LOAD);
            vlib_prefetch_buffer_header (b[7], LOAD);

            bi0 = from[0];
            bi1 = from[1];
            bi2 = from[2];
            bi3 = from[3];
            to_next[0] = bi0;
            to_next[1] = bi1;
            to_next[2] = bi2;
            to_next[3] = bi3;

            swif0 = vnet_buffer (b[0])->sw_if_index[VLIB_TX];
            swif1 = vnet_buffer (b[1])->sw_if_index[VLIB_TX];
            swif2 = vnet_buffer (b[2])->sw_if_index[VLIB_TX];
            swif3 = vnet_buffer (b[3])->sw_if_index[VLIB_TX];

            if (PREDICT_FALSE (hi->sw_if_index != swif0))
              {
                hi0 = vnet_get_sup_hw_interface (vnm, swif0);
                if ((hi0->caps & VNET_HW_INTERFACE_CAP_SUPPORTS_TCP_GSO) ==
                      0 &&
                    (b[0]->flags & VNET_BUFFER_F_GSO))
                  break;
              }
            if (PREDICT_FALSE (hi->sw_if_index != swif1))
              {
                hi1 = vnet_get_sup_hw_interface (vnm, swif1);
                if (!(hi1->caps & VNET_HW_INTERFACE_CAP_SUPPORTS_TCP_GSO) &&
                    (b[1]->flags & VNET_BUFFER_F_GSO))
                  break;
              }
            if (PREDICT_FALSE (hi->sw_if_index != swif2))
              {
                hi2 = vnet_get_sup_hw_interface (vnm, swif2);
                if ((hi2->caps & VNET_HW_INTERFACE_CAP_SUPPORTS_TCP_GSO) ==
                      0 &&
                    (b[2]->flags & VNET_BUFFER_F_GSO))
                  break;
              }
            if (PREDICT_FALSE (hi->sw_if_index != swif3))
              {
                hi3 = vnet_get_sup_hw_interface (vnm, swif3);
                if (!(hi3->caps & VNET_HW_INTERFACE_CAP_SUPPORTS_TCP_GSO) &&
                    (b[3]->flags & VNET_BUFFER_F_GSO))
                  break;
              }

            if (b[0]->flags & VLIB_BUFFER_IS_TRACED)
              {
                t0 = vlib_add_trace (vm, node, b[0], sizeof (t0[0]));
                t0->flags = b[0]->flags & VNET_BUFFER_F_GSO;
                t0->gso_size = vnet_buffer2 (b[0])->gso_size;
                t0->gso_l4_hdr_sz = vnet_buffer2 (b[0])->gso_l4_hdr_sz;
                vnet_generic_header_offset_parser (b[0], &t0->gho, is_l2,
                                                   is_ip4, is_ip6);
              }
            if (b[1]->flags & VLIB_BUFFER_IS_TRACED)
              {
                t1 = vlib_add_trace (vm, node, b[1], sizeof (t1[0]));
                t1->flags = b[1]->flags & VNET_BUFFER_F_GSO;
                t1->gso_size = vnet_buffer2 (b[1])->gso_size;
                t1->gso_l4_hdr_sz = vnet_buffer2 (b[1])->gso_l4_hdr_sz;
                vnet_generic_header_offset_parser (b[1], &t1->gho, is_l2,
                                                   is_ip4, is_ip6);
              }
            if (b[2]->flags & VLIB_BUFFER_IS_TRACED)
              {
                t2 = vlib_add_trace (vm, node, b[2], sizeof (t2[0]));
                t2->flags = b[2]->flags & VNET_BUFFER_F_GSO;
                t2->gso_size = vnet_buffer2 (b[2])->gso_size;
                t2->gso_l4_hdr_sz = vnet_buffer2 (b[2])->gso_l4_hdr_sz;
                vnet_generic_header_offset_parser (b[2], &t2->gho, is_l2,
                                                   is_ip4, is_ip6);
              }
            if (b[3]->flags & VLIB_BUFFER_IS_TRACED)
              {
                t3 = vlib_add_trace (vm, node, b[3], sizeof (t3[0]));
                t3->flags = b[3]->flags & VNET_BUFFER_F_GSO;
                t3->gso_size = vnet_buffer2 (b[3])->gso_size;
                t3->gso_l4_hdr_sz = vnet_buffer2 (b[3])->gso_l4_hdr_sz;
                vnet_generic_header_offset_parser (b[3], &t3->gho, is_l2,
                                                   is_ip4, is_ip6);
              }

            from += 4;
            to_next += 4;
            n_left_to_next -= 4;
            n_left_from -= 4;

            next0 = next1 = 0;
            next2 = next3 = 0;
            vnet_feature_next (&next0, b[0]);
            vnet_feature_next (&next1, b[1]);
            vnet_feature_next (&next2, b[2]);
            vnet_feature_next (&next3, b[3]);
            vlib_validate_buffer_enqueue_x4 (vm, node, next_index, to_next,
                                             n_left_to_next, bi0, bi1, bi2,
                                             bi3, next0, next1, next2, next3);
            b += 4;
          }

      while (from + 1 <= from_end && n_left_to_next > 0)
        {
          u32 bi0, swif0;
          gso_trace_t *t0;
          vnet_hw_interface_t *hi0;
          u32 next0 = 0;
          u32 do_segmentation0 = 0;

          swif0 = vnet_buffer (b[0])->sw_if_index[VLIB_TX];
          if (PREDICT_FALSE (hi->sw_if_index != swif0))
            {
              hi0 = vnet_get_sup_hw_interface (vnm, swif0);
              if ((hi0->caps & VNET_HW_INTERFACE_CAP_SUPPORTS_TCP_GSO) == 0 &&
                  (b[0]->flags & VNET_BUFFER_F_GSO))
                do_segmentation0 = 1;
            }
          else
            do_segmentation0 = do_segmentation;

          /* speculatively enqueue b0 to the current next frame */
          to_next[0] = bi0 = from[0];
          to_next += 1;
          n_left_to_next -= 1;
          from += 1;
          n_left_from -= 1;

          if (b[0]->flags & VLIB_BUFFER_IS_TRACED)
            {
              t0 = vlib_add_trace (vm, node, b[0], sizeof (t0[0]));
              t0->flags = b[0]->flags & VNET_BUFFER_F_GSO;
              t0->gso_size = vnet_buffer2 (b[0])->gso_size;
              t0->gso_l4_hdr_sz = vnet_buffer2 (b[0])->gso_l4_hdr_sz;
              vnet_generic_header_offset_parser (b[0], &t0->gho, is_l2,
                                                 is_ip4, is_ip6);
            }

          if (do_segmentation0)
            {
              if (PREDICT_FALSE (b[0]->flags & VNET_BUFFER_F_GSO))
                {
                  /*
                   * Undo the enqueue of the b0 - it is not going anywhere,
                   * and will be freed either after it's segmented or
                   * when dropped, if there is no buffers to segment into.
                   */
                  to_next -= 1;
                  n_left_to_next += 1;
                  /* undo the counting. */
                  generic_header_offset_t gho = { 0 };
                  u32 n_bytes_b0 = vlib_buffer_length_in_chain (vm, b[0]);
                  u32 n_tx_bytes = 0;
                  u32 inner_is_ip6 = is_ip6;

                  vnet_generic_header_offset_parser (b[0], &gho, is_l2,
                                                     is_ip4, is_ip6);

                  if (PREDICT_FALSE (gho.gho_flags & GHO_F_TUNNEL))
                    {
                      if (PREDICT_FALSE
                          (gho.gho_flags & (GHO_F_GRE_TUNNEL |
                                            GHO_F_GENEVE_TUNNEL)))
                        {
                          /* not supported yet */
                          drop_one_buffer_and_count (vm, vnm, node, from - 1,
                                                     hi->sw_if_index,
                                                     VNET_INTERFACE_OUTPUT_ERROR_UNHANDLED_GSO_TYPE);
                          b += 1;
                          continue;
                        }

                      vnet_get_inner_header (b[0], &gho);

                      n_bytes_b0 -= gho.outer_hdr_sz;
                      inner_is_ip6 = (gho.gho_flags & GHO_F_IP6) != 0;
                    }

                  n_tx_bytes =
                    tso_segment_buffer (vm, ptd, bi0, b[0], &gho, n_bytes_b0,
                                        is_l2, inner_is_ip6);

                  if (PREDICT_FALSE (n_tx_bytes == 0))
                    {
                      drop_one_buffer_and_count (vm, vnm, node, from - 1,
                                                 hi->sw_if_index,
                                                 VNET_INTERFACE_OUTPUT_ERROR_NO_BUFFERS_FOR_GSO);
                      b += 1;
                      continue;
                    }


                  if (PREDICT_FALSE (gho.gho_flags & GHO_F_VXLAN_TUNNEL))
                    {
                      vnet_get_outer_header (b[0], &gho);
                      n_tx_bytes +=
                        tso_segment_vxlan_tunnel_fixup (vm, ptd, b[0], &gho);
                    }
                  else
                    if (PREDICT_FALSE
                        (gho.gho_flags & (GHO_F_IPIP_TUNNEL |
                                          GHO_F_IPIP6_TUNNEL)))
                    {
                      vnet_get_outer_header (b[0], &gho);
                      n_tx_bytes +=
                        tso_segment_ipip_tunnel_fixup (vm, ptd, b[0], &gho);
                    }

                  u16 n_tx_bufs = vec_len (ptd->split_buffers);
                  u32 *from_seg = ptd->split_buffers;

                  while (n_tx_bufs > 0)
                    {
                      u32 sbi0;
                      vlib_buffer_t *sb0;
                      while (n_tx_bufs > 0 && n_left_to_next > 0)
                        {
                          sbi0 = to_next[0] = from_seg[0];
                          sb0 = vlib_get_buffer (vm, sbi0);
                          ASSERT (sb0->current_length > 0);
                          to_next += 1;
                          from_seg += 1;
                          n_left_to_next -= 1;
                          n_tx_bufs -= 1;
                          next0 = 0;
                          vnet_feature_next (&next0, sb0);
                          vlib_validate_buffer_enqueue_x1 (vm, node,
                                                           next_index,
                                                           to_next,
                                                           n_left_to_next,
                                                           sbi0, next0);
                        }
                      vlib_put_next_frame (vm, node, next_index,
                                           n_left_to_next);
                      if (n_tx_bufs > 0)
                        vlib_get_next_frame (vm, node, next_index,
                                             to_next, n_left_to_next);
                    }
                  /* The buffers were enqueued. Reset the length */
                  _vec_len (ptd->split_buffers) = 0;
                  /* Free the now segmented buffer */
                  vlib_buffer_free_one (vm, bi0);
                  b += 1;
                  continue;
                }
            }

          vnet_feature_next (&next0, b[0]);
          vlib_validate_buffer_enqueue_x1 (vm, node, next_index, to_next,
                                           n_left_to_next, bi0, next0);
          b += 1;
        }
      vlib_put_next_frame (vm, node, next_index, n_left_to_next);
    }

  return frame->n_vectors;
}

static_always_inline uword
vnet_gso_inline (vlib_main_t * vm,
                 vlib_node_runtime_t * node, vlib_frame_t * frame, int is_l2,
                 int is_ip4, int is_ip6)
{
  vnet_main_t *vnm = vnet_get_main ();
  vnet_hw_interface_t *hi;

  if (frame->n_vectors > 0)
    {
      u32 *from = vlib_frame_vector_args (frame);
      vlib_buffer_t *b = vlib_get_buffer (vm, from[0]);
      hi = vnet_get_sup_hw_interface (vnm,
                                      vnet_buffer (b)->sw_if_index[VLIB_TX]);

      if (hi->caps & VNET_HW_INTERFACE_CAP_SUPPORTS_TCP_GSO)
        return vnet_gso_node_inline (vm, node, frame, vnm, hi,
                                     is_l2, is_ip4, is_ip6,
                                     /* do_segmentation */ 0);
      else
        return vnet_gso_node_inline (vm, node, frame, vnm, hi,
                                     is_l2, is_ip4, is_ip6,
                                     /* do_segmentation */ 1);
    }
  return 0;
}

VLIB_NODE_FN (gso_l2_ip4_node) (vlib_main_t * vm, vlib_node_runtime_t * node,
                                vlib_frame_t * frame)
{
  return vnet_gso_inline (vm, node, frame, 1 /* l2 */ , 1 /* ip4 */ ,
                          0 /* ip6 */ );
}

VLIB_NODE_FN (gso_l2_ip6_node) (vlib_main_t * vm, vlib_node_runtime_t * node,
                                vlib_frame_t * frame)
{
  return vnet_gso_inline (vm, node, frame, 1 /* l2 */ , 0 /* ip4 */ ,
                          1 /* ip6 */ );
}

VLIB_NODE_FN (gso_ip4_node) (vlib_main_t * vm, vlib_node_runtime_t * node,
                             vlib_frame_t * frame)
{
  return vnet_gso_inline (vm, node, frame, 0 /* l2 */ , 1 /* ip4 */ ,
                          0 /* ip6 */ );
}

VLIB_NODE_FN (gso_ip6_node) (vlib_main_t * vm, vlib_node_runtime_t * node,
                             vlib_frame_t * frame)
{
  return vnet_gso_inline (vm, node, frame, 0 /* l2 */ , 0 /* ip4 */ ,
                          1 /* ip6 */ );
}

/* *INDENT-OFF* */

VLIB_REGISTER_NODE (gso_l2_ip4_node) = {
  .vector_size = sizeof (u32),
  .format_trace = format_gso_trace,
  .type = VLIB_NODE_TYPE_INTERNAL,
  .n_errors = 0,
  .n_next_nodes = 0,
  .name = "gso-l2-ip4",
};

VLIB_REGISTER_NODE (gso_l2_ip6_node) = {
  .vector_size = sizeof (u32),
  .format_trace = format_gso_trace,
  .type = VLIB_NODE_TYPE_INTERNAL,
  .n_errors = 0,
  .n_next_nodes = 0,
  .name = "gso-l2-ip6",
};

VLIB_REGISTER_NODE (gso_ip4_node) = {
  .vector_size = sizeof (u32),
  .format_trace = format_gso_trace,
  .type = VLIB_NODE_TYPE_INTERNAL,
  .n_errors = 0,
  .n_next_nodes = 0,
  .name = "gso-ip4",
};

VLIB_REGISTER_NODE (gso_ip6_node) = {
  .vector_size = sizeof (u32),
  .format_trace = format_gso_trace,
  .type = VLIB_NODE_TYPE_INTERNAL,
  .n_errors = 0,
  .n_next_nodes = 0,
  .name = "gso-ip6",
};

VNET_FEATURE_INIT (gso_l2_ip4_node, static) = {
  .arc_name = "l2-output-ip4",
  .node_name = "gso-l2-ip4",
  .runs_before = VNET_FEATURES ("l2-output-feat-arc-end"),
};

VNET_FEATURE_INIT (gso_l2_ip6_node, static) = {
  .arc_name = "l2-output-ip6",
  .node_name = "gso-l2-ip6",
  .runs_before = VNET_FEATURES ("l2-output-feat-arc-end"),
};

VNET_FEATURE_INIT (gso_ip4_node, static) = {
  .arc_name = "ip4-output",
  .node_name = "gso-ip4",
  .runs_before = VNET_FEATURES ("ipsec4-output-feature"),
};

VNET_FEATURE_INIT (gso_ip6_node, static) = {
  .arc_name = "ip6-output",
  .node_name = "gso-ip6",
  .runs_before = VNET_FEATURES ("ipsec6-output-feature"),
};

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