src/vnet/devices/virtio/device.c - fdio/vpp - Gitiles

 /*
  *------------------------------------------------------------------
  * Copyright (c) 2016 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 <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>

 #include <vlib/vlib.h>
 #include <vlib/unix/unix.h>
 #include <vnet/ethernet/ethernet.h>
 #include <vnet/gso/gso.h>
 #include <vnet/ip/ip4_packet.h>
 #include <vnet/ip/ip6_packet.h>
 #include <vnet/tcp/tcp_packet.h>
 #include <vnet/udp/udp_packet.h>
 #include <vnet/devices/virtio/virtio.h>

 #define foreach_virtio_tx_func_error	       \
 _(NO_FREE_SLOTS, "no free tx slots")           \
 _(TRUNC_PACKET, "packet > buffer size -- truncated in tx ring") \
 _(PENDING_MSGS, "pending msgs in tx ring") \
 _(NO_TX_QUEUES, "no tx queues")

 typedef enum
 {
 #define _(f,s) VIRTIO_TX_ERROR_##f,
   foreach_virtio_tx_func_error
 #undef _
     VIRTIO_TX_N_ERROR,
 } virtio_tx_func_error_t;

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

 static u8 *
 format_virtio_device (u8 * s, va_list * args)
 {
   u32 dev_instance = va_arg (*args, u32);
   int verbose = va_arg (*args, int);
   u32 indent = format_get_indent (s);

   s = format (s, "VIRTIO interface");
   if (verbose)
     {
       s = format (s, "\n%U instance %u", format_white_space, indent + 2,
 		  dev_instance);
     }
   return s;
 }

 static u8 *
 format_virtio_tx_trace (u8 * s, va_list * args)
 {
   s = format (s, "Unimplemented...");
   return s;
 }

 static_always_inline void
 virtio_free_used_device_desc (vlib_main_t * vm, virtio_vring_t * vring)
 {
   u16 used = vring->desc_in_use;
   u16 sz = vring->size;
   u16 mask = sz - 1;
   u16 last = vring->last_used_idx;
   u16 n_left = vring->used->idx - last;

   if (n_left == 0)
     return;

   while (n_left)
     {
       struct vring_used_elem *e = &vring->used->ring[last & mask];
       u16 slot, n_buffers;
       slot = n_buffers = e->id;

       while (e->id == n_buffers)
 	{
 	  n_left--;
 	  last++;
 	  n_buffers++;
 	  if (n_left == 0)
 	    break;
 	  e = &vring->used->ring[last & mask];
 	}
       vlib_buffer_free_from_ring (vm, vring->buffers, slot,
 				  sz, (n_buffers - slot));
       used -= (n_buffers - slot);

       if (n_left > 0)
 	{
 	  slot = e->id;

 	  vlib_buffer_free (vm, &vring->buffers[slot], 1);
 	  used--;
 	  last++;
 	  n_left--;
 	}
     }
   vring->desc_in_use = used;
   vring->last_used_idx = last;
 }

 static_always_inline void
 set_checksum_offsets (vlib_main_t * vm, virtio_if_t * vif, vlib_buffer_t * b,
 		      struct virtio_net_hdr_v1 *hdr)
 {
   if (b->flags & VNET_BUFFER_F_IS_IP4)
     {
       ip4_header_t *ip4;
       gso_header_offset_t gho = vnet_gso_header_offset_parser (b, 0);
       hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
       hdr->csum_start = gho.l4_hdr_offset;	// 0x22;
       if (b->flags & VNET_BUFFER_F_OFFLOAD_TCP_CKSUM)
 	hdr->csum_offset = STRUCT_OFFSET_OF (tcp_header_t, checksum);
       else if (b->flags & VNET_BUFFER_F_OFFLOAD_UDP_CKSUM)
 	hdr->csum_offset = STRUCT_OFFSET_OF (udp_header_t, checksum);

       /*
        * virtio devices do not support IP4 checksum offload. So driver takes care
        * of it while doing tx.
        */
       ip4 =
 	(ip4_header_t *) (vlib_buffer_get_current (b) + gho.l3_hdr_offset);
       if (b->flags & VNET_BUFFER_F_OFFLOAD_IP_CKSUM)
 	ip4->checksum = ip4_header_checksum (ip4);
     }
   else if (b->flags & VNET_BUFFER_F_IS_IP6)
     {
       gso_header_offset_t gho = vnet_gso_header_offset_parser (b, 1);
       hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
       hdr->csum_start = gho.l4_hdr_offset;	// 0x36;
       if (b->flags & VNET_BUFFER_F_OFFLOAD_TCP_CKSUM)
 	hdr->csum_offset = STRUCT_OFFSET_OF (tcp_header_t, checksum);
       else if (b->flags & VNET_BUFFER_F_OFFLOAD_UDP_CKSUM)
 	hdr->csum_offset = STRUCT_OFFSET_OF (udp_header_t, checksum);
     }
 }

 static_always_inline u16
 add_buffer_to_slot (vlib_main_t * vm, virtio_if_t * vif,
 		    virtio_vring_t * vring, u32 bi, u16 avail, u16 next,
 		    u16 mask, int do_gso, int csum_offload)
 {
   u16 n_added = 0;
   int hdr_sz = vif->virtio_net_hdr_sz;
   struct vring_desc *d;
   d = &vring->desc[next];
   vlib_buffer_t *b = vlib_get_buffer (vm, bi);
   struct virtio_net_hdr_v1 *hdr = vlib_buffer_get_current (b) - hdr_sz;

   clib_memset (hdr, 0, hdr_sz);

   if (do_gso && (b->flags & VNET_BUFFER_F_GSO))
     {
       if (b->flags & VNET_BUFFER_F_IS_IP4)
 	{
 	  ip4_header_t *ip4;
 	  gso_header_offset_t gho = vnet_gso_header_offset_parser (b, 0);
 	  hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
 	  hdr->gso_size = vnet_buffer2 (b)->gso_size;
 	  hdr->hdr_len = gho.l4_hdr_offset + gho.l4_hdr_sz;
 	  hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
 	  hdr->csum_start = gho.l4_hdr_offset;	// 0x22;
 	  hdr->csum_offset = STRUCT_OFFSET_OF (tcp_header_t, checksum);
 	  ip4 =
 	    (ip4_header_t *) (vlib_buffer_get_current (b) +
 			      gho.l3_hdr_offset);
 	  /*
 	   * virtio devices do not support IP4 checksum offload. So driver takes care
 	   * of it while doing tx.
 	   */
 	  if (b->flags & VNET_BUFFER_F_OFFLOAD_IP_CKSUM)
 	    ip4->checksum = ip4_header_checksum (ip4);
 	}
       else if (b->flags & VNET_BUFFER_F_IS_IP6)
 	{
 	  gso_header_offset_t gho = vnet_gso_header_offset_parser (b, 1);
 	  hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
 	  hdr->gso_size = vnet_buffer2 (b)->gso_size;
 	  hdr->hdr_len = gho.l4_hdr_offset + gho.l4_hdr_sz;
 	  hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
 	  hdr->csum_start = gho.l4_hdr_offset;	// 0x36;
 	  hdr->csum_offset = STRUCT_OFFSET_OF (tcp_header_t, checksum);
 	}
     }
   else if (csum_offload
 	   && (b->flags & (VNET_BUFFER_F_OFFLOAD_TCP_CKSUM |
 			   VNET_BUFFER_F_OFFLOAD_UDP_CKSUM)))
     {
       set_checksum_offsets (vm, vif, b, hdr);
     }

   if (PREDICT_TRUE ((b->flags & VLIB_BUFFER_NEXT_PRESENT) == 0))
     {
       d->addr =
 	((vif->type == VIRTIO_IF_TYPE_PCI) ? vlib_buffer_get_current_pa (vm,
 									 b) :
 	 pointer_to_uword (vlib_buffer_get_current (b))) - hdr_sz;
       d->len = b->current_length + hdr_sz;
       d->flags = 0;
     }
   else
     {
       /*
        * We are using single vlib_buffer_t for indirect descriptor(s)
        * chain. Single descriptor is 16 bytes and vlib_buffer_t
        * has 2048 bytes space. So maximum long chain can have 128
        * (=2048/16) indirect descriptors.
        * It can easily support 65535 bytes of Jumbo frames with
        * each data buffer size of 512 bytes minimum.
        */
       u32 indirect_buffer = 0;
       if (PREDICT_FALSE (vlib_buffer_alloc (vm, &indirect_buffer, 1) == 0))
 	return n_added;

       vlib_buffer_t *indirect_desc = vlib_get_buffer (vm, indirect_buffer);
       indirect_desc->current_data = 0;
       indirect_desc->flags |= VLIB_BUFFER_NEXT_PRESENT;
       indirect_desc->next_buffer = bi;
       bi = indirect_buffer;

       struct vring_desc *id =
 	(struct vring_desc *) vlib_buffer_get_current (indirect_desc);
       u32 count = 1;
       if (vif->type == VIRTIO_IF_TYPE_PCI)
 	{
 	  d->addr = vlib_physmem_get_pa (vm, id);
 	  id->addr = vlib_buffer_get_current_pa (vm, b) - hdr_sz;

 	  /*
 	   * If VIRTIO_F_ANY_LAYOUT is not negotiated, then virtio_net_hdr
 	   * should be presented in separate descriptor and data will start
 	   * from next descriptor.
 	   */
 	  if (PREDICT_TRUE
 	      (vif->features & VIRTIO_FEATURE (VIRTIO_F_ANY_LAYOUT)))
 	    id->len = b->current_length + hdr_sz;
 	  else
 	    {
 	      id->len = hdr_sz;
 	      id->flags = VRING_DESC_F_NEXT;
 	      id->next = count;
 	      count++;
 	      id++;
 	      id->addr = vlib_buffer_get_current_pa (vm, b);
 	      id->len = b->current_length;
 	    }
 	  while (b->flags & VLIB_BUFFER_NEXT_PRESENT)
 	    {
 	      id->flags = VRING_DESC_F_NEXT;
 	      id->next = count;
 	      count++;
 	      id++;
 	      b = vlib_get_buffer (vm, b->next_buffer);
 	      id->addr = vlib_buffer_get_current_pa (vm, b);
 	      id->len = b->current_length;
 	    }
 	}
       else			/* VIRTIO_IF_TYPE_TAP */
 	{
 	  d->addr = pointer_to_uword (id);
 	  /* first buffer in chain */
 	  id->addr = pointer_to_uword (vlib_buffer_get_current (b)) - hdr_sz;
 	  id->len = b->current_length + hdr_sz;

 	  while (b->flags & VLIB_BUFFER_NEXT_PRESENT)
 	    {
 	      id->flags = VRING_DESC_F_NEXT;
 	      id->next = count;
 	      count++;
 	      id++;
 	      b = vlib_get_buffer (vm, b->next_buffer);
 	      id->addr = pointer_to_uword (vlib_buffer_get_current (b));
 	      id->len = b->current_length;
 	    }
 	}
       id->flags = 0;
       id->next = 0;
       d->len = count * sizeof (struct vring_desc);
       d->flags = VRING_DESC_F_INDIRECT;
     }
   vring->buffers[next] = bi;
   vring->avail->ring[avail & mask] = next;
   n_added++;
   return n_added;
 }

 static_always_inline uword
 virtio_interface_tx_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 			    vlib_frame_t * frame, virtio_if_t * vif,
 			    int do_gso, int csum_offload)
 {
   u16 n_left = frame->n_vectors;
   virtio_vring_t *vring;
   u16 qid = vm->thread_index % vif->num_txqs;
   vring = vec_elt_at_index (vif->txq_vrings, qid);
   u16 used, next, avail;
   u16 sz = vring->size;
   u16 mask = sz - 1;
   u32 *buffers = vlib_frame_vector_args (frame);

   clib_spinlock_lock_if_init (&vring->lockp);

   if ((vring->used->flags & VIRTIO_RING_FLAG_MASK_INT) == 0 &&
       (vring->last_kick_avail_idx != vring->avail->idx))
     virtio_kick (vm, vring, vif);

   /* free consumed buffers */
   virtio_free_used_device_desc (vm, vring);

   used = vring->desc_in_use;
   next = vring->desc_next;
   avail = vring->avail->idx;

   while (n_left && used < sz)
     {
       u16 n_added = 0;
       n_added =
 	add_buffer_to_slot (vm, vif, vring, buffers[0], avail, next, mask,
 			    do_gso, csum_offload);
       if (!n_added)
 	break;
       avail += n_added;
       next = (next + n_added) & mask;
       used += n_added;
       buffers++;
       n_left--;
     }

   if (n_left != frame->n_vectors)
     {
       CLIB_MEMORY_STORE_BARRIER ();
       vring->avail->idx = avail;
       vring->desc_next = next;
       vring->desc_in_use = used;
       if ((vring->used->flags & VIRTIO_RING_FLAG_MASK_INT) == 0)
 	virtio_kick (vm, vring, vif);
     }

   if (n_left)
     {
       vlib_error_count (vm, node->node_index, VIRTIO_TX_ERROR_NO_FREE_SLOTS,
 			n_left);
       vlib_buffer_free (vm, buffers, n_left);
     }

   clib_spinlock_unlock_if_init (&vring->lockp);

   return frame->n_vectors - n_left;
 }

 VNET_DEVICE_CLASS_TX_FN (virtio_device_class) (vlib_main_t * vm,
 					       vlib_node_runtime_t * node,
 					       vlib_frame_t * frame)
 {
   vnet_main_t *vnm = vnet_get_main ();
   virtio_main_t *nm = &virtio_main;
   vnet_interface_output_runtime_t *rund = (void *) node->runtime_data;
   virtio_if_t *vif = pool_elt_at_index (nm->interfaces, rund->dev_instance);
   vnet_hw_interface_t *hw = vnet_get_hw_interface (vnm, vif->hw_if_index);

   if (hw->flags & VNET_HW_INTERFACE_FLAG_SUPPORTS_GSO)
     return virtio_interface_tx_inline (vm, node, frame, vif, 1 /* do_gso */ ,
 				       1);
   else if (hw->flags & VNET_HW_INTERFACE_FLAG_SUPPORTS_TX_L4_CKSUM_OFFLOAD)
     return virtio_interface_tx_inline (vm, node, frame, vif,
 				       0 /* no do_gso */ , 1);
   else
     return virtio_interface_tx_inline (vm, node, frame, vif,
 				       0 /* no do_gso */ , 0);
 }

 static void
 virtio_set_interface_next_node (vnet_main_t * vnm, u32 hw_if_index,
 				u32 node_index)
 {
   virtio_main_t *apm = &virtio_main;
   vnet_hw_interface_t *hw = vnet_get_hw_interface (vnm, hw_if_index);
   virtio_if_t *vif = pool_elt_at_index (apm->interfaces, hw->dev_instance);

   /* Shut off redirection */
   if (node_index == ~0)
     {
       vif->per_interface_next_index = node_index;
       return;
     }

   vif->per_interface_next_index =
     vlib_node_add_next (vlib_get_main (), virtio_input_node.index,
 			node_index);
 }

 static void
 virtio_clear_hw_interface_counters (u32 instance)
 {
   /* Nothing for now */
 }

 static clib_error_t *
 virtio_interface_rx_mode_change (vnet_main_t * vnm, u32 hw_if_index, u32 qid,
 				 vnet_hw_interface_rx_mode mode)
 {
   virtio_main_t *mm = &virtio_main;
   vnet_hw_interface_t *hw = vnet_get_hw_interface (vnm, hw_if_index);
   virtio_if_t *vif = pool_elt_at_index (mm->interfaces, hw->dev_instance);
   virtio_vring_t *vring = vec_elt_at_index (vif->rxq_vrings, qid);

   if (vif->type == VIRTIO_IF_TYPE_PCI && !(vif->support_int_mode))
     {
       vring->avail->flags |= VIRTIO_RING_FLAG_MASK_INT;
       return clib_error_return (0, "interrupt mode is not supported");
     }

   if (mode == VNET_HW_INTERFACE_RX_MODE_POLLING)
     vring->avail->flags |= VIRTIO_RING_FLAG_MASK_INT;
   else
     vring->avail->flags &= ~VIRTIO_RING_FLAG_MASK_INT;

   return 0;
 }

 static clib_error_t *
 virtio_interface_admin_up_down (vnet_main_t * vnm, u32 hw_if_index, u32 flags)
 {
   virtio_main_t *mm = &virtio_main;
   vnet_hw_interface_t *hw = vnet_get_hw_interface (vnm, hw_if_index);
   virtio_if_t *vif = pool_elt_at_index (mm->interfaces, hw->dev_instance);

   if (flags & VNET_SW_INTERFACE_FLAG_ADMIN_UP)
     vif->flags |= VIRTIO_IF_FLAG_ADMIN_UP;
   else
     vif->flags &= ~VIRTIO_IF_FLAG_ADMIN_UP;

   return 0;
 }

 static clib_error_t *
 virtio_subif_add_del_function (vnet_main_t * vnm,
 			       u32 hw_if_index,
 			       struct vnet_sw_interface_t *st, int is_add)
 {
   /* Nothing for now */
   return 0;
 }

 /* *INDENT-OFF* */
 VNET_DEVICE_CLASS (virtio_device_class) = {
   .name = "virtio",
   .format_device_name = format_virtio_device_name,
   .format_device = format_virtio_device,
   .format_tx_trace = format_virtio_tx_trace,
   .tx_function_n_errors = VIRTIO_TX_N_ERROR,
   .tx_function_error_strings = virtio_tx_func_error_strings,
   .rx_redirect_to_node = virtio_set_interface_next_node,
   .clear_counters = virtio_clear_hw_interface_counters,
   .admin_up_down_function = virtio_interface_admin_up_down,
   .subif_add_del_function = virtio_subif_add_del_function,
   .rx_mode_change_function = virtio_interface_rx_mode_change,
 };
 /* *INDENT-ON* */

 /*
  * fd.io coding-style-patch-verification: ON
  *
  * Local Variables:
  * eval: (c-set-style "gnu")
  * End:
  */
	/*
	*------------------------------------------------------------------
	* Copyright (c) 2016 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 <sys/types.h>
	#include <sys/stat.h>
	#include <fcntl.h>

	#include <vlib/vlib.h>
	#include <vlib/unix/unix.h>
	#include <vnet/ethernet/ethernet.h>
	#include <vnet/gso/gso.h>
	#include <vnet/ip/ip4_packet.h>
	#include <vnet/ip/ip6_packet.h>
	#include <vnet/tcp/tcp_packet.h>
	#include <vnet/udp/udp_packet.h>
	#include <vnet/devices/virtio/virtio.h>

	#define foreach_virtio_tx_func_error \
	_(NO_FREE_SLOTS, "no free tx slots") \
	_(TRUNC_PACKET, "packet > buffer size -- truncated in tx ring") \
	_(PENDING_MSGS, "pending msgs in tx ring") \
	_(NO_TX_QUEUES, "no tx queues")

	typedef enum
	{
	#define _(f,s) VIRTIO_TX_ERROR_##f,
	foreach_virtio_tx_func_error
	#undef _
	VIRTIO_TX_N_ERROR,
	} virtio_tx_func_error_t;

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

	static u8 *
	format_virtio_device (u8 * s, va_list * args)
	{
	u32 dev_instance = va_arg (*args, u32);
	int verbose = va_arg (*args, int);
	u32 indent = format_get_indent (s);

	s = format (s, "VIRTIO interface");
	if (verbose)
	{
	s = format (s, "\n%U instance %u", format_white_space, indent + 2,
	dev_instance);
	}
	return s;
	}

	static u8 *
	format_virtio_tx_trace (u8 * s, va_list * args)
	{
	s = format (s, "Unimplemented...");
	return s;
	}

	static_always_inline void
	virtio_free_used_device_desc (vlib_main_t * vm, virtio_vring_t * vring)
	{
	u16 used = vring->desc_in_use;
	u16 sz = vring->size;
	u16 mask = sz - 1;
	u16 last = vring->last_used_idx;
	u16 n_left = vring->used->idx - last;

	if (n_left == 0)
	return;

	while (n_left)
	{
	struct vring_used_elem *e = &vring->used->ring[last & mask];
	u16 slot, n_buffers;
	slot = n_buffers = e->id;

	while (e->id == n_buffers)
	{
	n_left--;
	last++;
	n_buffers++;
	if (n_left == 0)
	break;
	e = &vring->used->ring[last & mask];
	}
	vlib_buffer_free_from_ring (vm, vring->buffers, slot,
	sz, (n_buffers - slot));
	used -= (n_buffers - slot);

	if (n_left > 0)
	{
	slot = e->id;

	vlib_buffer_free (vm, &vring->buffers[slot], 1);
	used--;
	last++;
	n_left--;
	}
	}
	vring->desc_in_use = used;
	vring->last_used_idx = last;
	}

	static_always_inline void
	set_checksum_offsets (vlib_main_t * vm, virtio_if_t * vif, vlib_buffer_t * b,
	struct virtio_net_hdr_v1 *hdr)
	{
	if (b->flags & VNET_BUFFER_F_IS_IP4)
	{
	ip4_header_t *ip4;
	gso_header_offset_t gho = vnet_gso_header_offset_parser (b, 0);
	hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
	hdr->csum_start = gho.l4_hdr_offset; // 0x22;
	if (b->flags & VNET_BUFFER_F_OFFLOAD_TCP_CKSUM)
	hdr->csum_offset = STRUCT_OFFSET_OF (tcp_header_t, checksum);
	else if (b->flags & VNET_BUFFER_F_OFFLOAD_UDP_CKSUM)
	hdr->csum_offset = STRUCT_OFFSET_OF (udp_header_t, checksum);

	/*
	* virtio devices do not support IP4 checksum offload. So driver takes care
	* of it while doing tx.
	*/
	ip4 =
	(ip4_header_t *) (vlib_buffer_get_current (b) + gho.l3_hdr_offset);
	if (b->flags & VNET_BUFFER_F_OFFLOAD_IP_CKSUM)
	ip4->checksum = ip4_header_checksum (ip4);
	}
	else if (b->flags & VNET_BUFFER_F_IS_IP6)
	{
	gso_header_offset_t gho = vnet_gso_header_offset_parser (b, 1);
	hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
	hdr->csum_start = gho.l4_hdr_offset; // 0x36;
	if (b->flags & VNET_BUFFER_F_OFFLOAD_TCP_CKSUM)
	hdr->csum_offset = STRUCT_OFFSET_OF (tcp_header_t, checksum);
	else if (b->flags & VNET_BUFFER_F_OFFLOAD_UDP_CKSUM)
	hdr->csum_offset = STRUCT_OFFSET_OF (udp_header_t, checksum);
	}
	}

	static_always_inline u16
	add_buffer_to_slot (vlib_main_t * vm, virtio_if_t * vif,
	virtio_vring_t * vring, u32 bi, u16 avail, u16 next,
	u16 mask, int do_gso, int csum_offload)
	{
	u16 n_added = 0;
	int hdr_sz = vif->virtio_net_hdr_sz;
	struct vring_desc *d;
	d = &vring->desc[next];
	vlib_buffer_t *b = vlib_get_buffer (vm, bi);
	struct virtio_net_hdr_v1 *hdr = vlib_buffer_get_current (b) - hdr_sz;

	clib_memset (hdr, 0, hdr_sz);

	if (do_gso && (b->flags & VNET_BUFFER_F_GSO))
	{
	if (b->flags & VNET_BUFFER_F_IS_IP4)
	{
	ip4_header_t *ip4;
	gso_header_offset_t gho = vnet_gso_header_offset_parser (b, 0);
	hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
	hdr->gso_size = vnet_buffer2 (b)->gso_size;
	hdr->hdr_len = gho.l4_hdr_offset + gho.l4_hdr_sz;
	hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
	hdr->csum_start = gho.l4_hdr_offset; // 0x22;
	hdr->csum_offset = STRUCT_OFFSET_OF (tcp_header_t, checksum);
	ip4 =
	(ip4_header_t *) (vlib_buffer_get_current (b) +
	gho.l3_hdr_offset);
	/*
	* virtio devices do not support IP4 checksum offload. So driver takes care
	* of it while doing tx.
	*/
	if (b->flags & VNET_BUFFER_F_OFFLOAD_IP_CKSUM)
	ip4->checksum = ip4_header_checksum (ip4);
	}
	else if (b->flags & VNET_BUFFER_F_IS_IP6)
	{
	gso_header_offset_t gho = vnet_gso_header_offset_parser (b, 1);
	hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
	hdr->gso_size = vnet_buffer2 (b)->gso_size;
	hdr->hdr_len = gho.l4_hdr_offset + gho.l4_hdr_sz;
	hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
	hdr->csum_start = gho.l4_hdr_offset; // 0x36;
	hdr->csum_offset = STRUCT_OFFSET_OF (tcp_header_t, checksum);
	}
	}
	else if (csum_offload
	&& (b->flags & (VNET_BUFFER_F_OFFLOAD_TCP_CKSUM \|
	VNET_BUFFER_F_OFFLOAD_UDP_CKSUM)))
	{
	set_checksum_offsets (vm, vif, b, hdr);
	}

	if (PREDICT_TRUE ((b->flags & VLIB_BUFFER_NEXT_PRESENT) == 0))
	{
	d->addr =
	((vif->type == VIRTIO_IF_TYPE_PCI) ? vlib_buffer_get_current_pa (vm,
	b) :
	pointer_to_uword (vlib_buffer_get_current (b))) - hdr_sz;
	d->len = b->current_length + hdr_sz;
	d->flags = 0;
	}
	else
	{
	/*
	* We are using single vlib_buffer_t for indirect descriptor(s)
	* chain. Single descriptor is 16 bytes and vlib_buffer_t
	* has 2048 bytes space. So maximum long chain can have 128
	* (=2048/16) indirect descriptors.
	* It can easily support 65535 bytes of Jumbo frames with
	* each data buffer size of 512 bytes minimum.
	*/
	u32 indirect_buffer = 0;
	if (PREDICT_FALSE (vlib_buffer_alloc (vm, &indirect_buffer, 1) == 0))
	return n_added;

	vlib_buffer_t *indirect_desc = vlib_get_buffer (vm, indirect_buffer);
	indirect_desc->current_data = 0;
	indirect_desc->flags \|= VLIB_BUFFER_NEXT_PRESENT;
	indirect_desc->next_buffer = bi;
	bi = indirect_buffer;

	struct vring_desc *id =
	(struct vring_desc *) vlib_buffer_get_current (indirect_desc);
	u32 count = 1;
	if (vif->type == VIRTIO_IF_TYPE_PCI)
	{
	d->addr = vlib_physmem_get_pa (vm, id);
	id->addr = vlib_buffer_get_current_pa (vm, b) - hdr_sz;

	/*
	* If VIRTIO_F_ANY_LAYOUT is not negotiated, then virtio_net_hdr
	* should be presented in separate descriptor and data will start
	* from next descriptor.
	*/
	if (PREDICT_TRUE
	(vif->features & VIRTIO_FEATURE (VIRTIO_F_ANY_LAYOUT)))
	id->len = b->current_length + hdr_sz;
	else
	{
	id->len = hdr_sz;
	id->flags = VRING_DESC_F_NEXT;
	id->next = count;
	count++;
	id++;
	id->addr = vlib_buffer_get_current_pa (vm, b);
	id->len = b->current_length;
	}
	while (b->flags & VLIB_BUFFER_NEXT_PRESENT)
	{
	id->flags = VRING_DESC_F_NEXT;
	id->next = count;
	count++;
	id++;
	b = vlib_get_buffer (vm, b->next_buffer);
	id->addr = vlib_buffer_get_current_pa (vm, b);
	id->len = b->current_length;
	}
	}
	else /* VIRTIO_IF_TYPE_TAP */
	{
	d->addr = pointer_to_uword (id);
	/* first buffer in chain */
	id->addr = pointer_to_uword (vlib_buffer_get_current (b)) - hdr_sz;
	id->len = b->current_length + hdr_sz;

	while (b->flags & VLIB_BUFFER_NEXT_PRESENT)
	{
	id->flags = VRING_DESC_F_NEXT;
	id->next = count;
	count++;
	id++;
	b = vlib_get_buffer (vm, b->next_buffer);
	id->addr = pointer_to_uword (vlib_buffer_get_current (b));
	id->len = b->current_length;
	}
	}
	id->flags = 0;
	id->next = 0;
	d->len = count * sizeof (struct vring_desc);
	d->flags = VRING_DESC_F_INDIRECT;
	}
	vring->buffers[next] = bi;
	vring->avail->ring[avail & mask] = next;
	n_added++;
	return n_added;
	}

	static_always_inline uword
	virtio_interface_tx_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
	vlib_frame_t * frame, virtio_if_t * vif,
	int do_gso, int csum_offload)
	{
	u16 n_left = frame->n_vectors;
	virtio_vring_t *vring;
	u16 qid = vm->thread_index % vif->num_txqs;
	vring = vec_elt_at_index (vif->txq_vrings, qid);
	u16 used, next, avail;
	u16 sz = vring->size;
	u16 mask = sz - 1;
	u32 *buffers = vlib_frame_vector_args (frame);

	clib_spinlock_lock_if_init (&vring->lockp);

	if ((vring->used->flags & VIRTIO_RING_FLAG_MASK_INT) == 0 &&
	(vring->last_kick_avail_idx != vring->avail->idx))
	virtio_kick (vm, vring, vif);

	/* free consumed buffers */
	virtio_free_used_device_desc (vm, vring);

	used = vring->desc_in_use;
	next = vring->desc_next;
	avail = vring->avail->idx;

	while (n_left && used < sz)
	{
	u16 n_added = 0;
	n_added =
	add_buffer_to_slot (vm, vif, vring, buffers[0], avail, next, mask,
	do_gso, csum_offload);
	if (!n_added)
	break;
	avail += n_added;
	next = (next + n_added) & mask;
	used += n_added;
	buffers++;
	n_left--;
	}

	if (n_left != frame->n_vectors)
	{
	CLIB_MEMORY_STORE_BARRIER ();
	vring->avail->idx = avail;
	vring->desc_next = next;
	vring->desc_in_use = used;
	if ((vring->used->flags & VIRTIO_RING_FLAG_MASK_INT) == 0)
	virtio_kick (vm, vring, vif);
	}

	if (n_left)
	{
	vlib_error_count (vm, node->node_index, VIRTIO_TX_ERROR_NO_FREE_SLOTS,
	n_left);
	vlib_buffer_free (vm, buffers, n_left);
	}

	clib_spinlock_unlock_if_init (&vring->lockp);

	return frame->n_vectors - n_left;
	}

	VNET_DEVICE_CLASS_TX_FN (virtio_device_class) (vlib_main_t * vm,
	vlib_node_runtime_t * node,
	vlib_frame_t * frame)
	{
	vnet_main_t *vnm = vnet_get_main ();
	virtio_main_t *nm = &virtio_main;
	vnet_interface_output_runtime_t rund = (void ) node->runtime_data;
	virtio_if_t *vif = pool_elt_at_index (nm->interfaces, rund->dev_instance);
	vnet_hw_interface_t *hw = vnet_get_hw_interface (vnm, vif->hw_if_index);

	if (hw->flags & VNET_HW_INTERFACE_FLAG_SUPPORTS_GSO)
	return virtio_interface_tx_inline (vm, node, frame, vif, 1 /* do_gso */ ,
	1);
	else if (hw->flags & VNET_HW_INTERFACE_FLAG_SUPPORTS_TX_L4_CKSUM_OFFLOAD)
	return virtio_interface_tx_inline (vm, node, frame, vif,
	0 /* no do_gso */ , 1);
	else
	return virtio_interface_tx_inline (vm, node, frame, vif,
	0 /* no do_gso */ , 0);
	}

	static void
	virtio_set_interface_next_node (vnet_main_t * vnm, u32 hw_if_index,
	u32 node_index)
	{
	virtio_main_t *apm = &virtio_main;
	vnet_hw_interface_t *hw = vnet_get_hw_interface (vnm, hw_if_index);
	virtio_if_t *vif = pool_elt_at_index (apm->interfaces, hw->dev_instance);

	/* Shut off redirection */
	if (node_index == ~0)
	{
	vif->per_interface_next_index = node_index;
	return;
	}

	vif->per_interface_next_index =
	vlib_node_add_next (vlib_get_main (), virtio_input_node.index,
	node_index);
	}

	static void
	virtio_clear_hw_interface_counters (u32 instance)
	{
	/* Nothing for now */
	}

	static clib_error_t *
	virtio_interface_rx_mode_change (vnet_main_t * vnm, u32 hw_if_index, u32 qid,
	vnet_hw_interface_rx_mode mode)
	{
	virtio_main_t *mm = &virtio_main;
	vnet_hw_interface_t *hw = vnet_get_hw_interface (vnm, hw_if_index);
	virtio_if_t *vif = pool_elt_at_index (mm->interfaces, hw->dev_instance);
	virtio_vring_t *vring = vec_elt_at_index (vif->rxq_vrings, qid);

	if (vif->type == VIRTIO_IF_TYPE_PCI && !(vif->support_int_mode))
	{
	vring->avail->flags \|= VIRTIO_RING_FLAG_MASK_INT;
	return clib_error_return (0, "interrupt mode is not supported");
	}

	if (mode == VNET_HW_INTERFACE_RX_MODE_POLLING)
	vring->avail->flags \|= VIRTIO_RING_FLAG_MASK_INT;
	else
	vring->avail->flags &= ~VIRTIO_RING_FLAG_MASK_INT;

	return 0;
	}

	static clib_error_t *
	virtio_interface_admin_up_down (vnet_main_t * vnm, u32 hw_if_index, u32 flags)
	{
	virtio_main_t *mm = &virtio_main;
	vnet_hw_interface_t *hw = vnet_get_hw_interface (vnm, hw_if_index);
	virtio_if_t *vif = pool_elt_at_index (mm->interfaces, hw->dev_instance);

	if (flags & VNET_SW_INTERFACE_FLAG_ADMIN_UP)
	vif->flags \|= VIRTIO_IF_FLAG_ADMIN_UP;
	else
	vif->flags &= ~VIRTIO_IF_FLAG_ADMIN_UP;

	return 0;
	}

	static clib_error_t *
	virtio_subif_add_del_function (vnet_main_t * vnm,
	u32 hw_if_index,
	struct vnet_sw_interface_t *st, int is_add)
	{
	/* Nothing for now */
	return 0;
	}

	/* INDENT-OFF */
	VNET_DEVICE_CLASS (virtio_device_class) = {
	.name = "virtio",
	.format_device_name = format_virtio_device_name,
	.format_device = format_virtio_device,
	.format_tx_trace = format_virtio_tx_trace,
	.tx_function_n_errors = VIRTIO_TX_N_ERROR,
	.tx_function_error_strings = virtio_tx_func_error_strings,
	.rx_redirect_to_node = virtio_set_interface_next_node,
	.clear_counters = virtio_clear_hw_interface_counters,
	.admin_up_down_function = virtio_interface_admin_up_down,
	.subif_add_del_function = virtio_subif_add_del_function,
	.rx_mode_change_function = virtio_interface_rx_mode_change,
	};
	/* INDENT-ON */

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