l2_vtr.h

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/*
 * l2_vtr.h : layer 2 vlan tag rewrite processing
 *
 * Copyright (c) 2013 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.
 */

#ifndef included_vnet_l2_vtr_h
#define included_vnet_l2_vtr_h

#include <vlib/vlib.h>
#include <vnet/vnet.h>
#include <vnet/ethernet/packet.h>
#include <vnet/l2/l2_vtr.h>

// VTR config options for API and CLI support
typedef enum {
  L2_VTR_DISABLED,
  L2_VTR_PUSH_1,
  L2_VTR_PUSH_2,
  L2_VTR_POP_1,
  L2_VTR_POP_2,
  L2_VTR_TRANSLATE_1_1,
  L2_VTR_TRANSLATE_1_2,
  L2_VTR_TRANSLATE_2_1,
  L2_VTR_TRANSLATE_2_2
} l2_vtr_op_t;

// Per-interface vlan tag rewrite configuration
// There will be one instance of this struct for each sw_if_index 
// for both input vtr and output vtr
typedef struct {
  union {
    // Up to two vlan tags to push. 
    // if there is only one vlan tag to push, it is in tags[1].
    ethernet_vlan_header_tv_t tags[2];
    u64 raw_tags;
  };

  union {
    struct {
      u8 push_bytes;  // number of bytes to push for up to 2 vlans (0,4,8)
      u8 pop_bytes;   // number of bytes to pop for up to 2 vlans (0,4,8)
    };
    u16 push_and_pop_bytes;  // if 0 then the feature is disabled
  };
} vtr_config_t;


// Perform the configured tag rewrite on the packet.
// Return 0 if ok, 1 if packet should be dropped (e.g. tried to pop too many tags)
always_inline u32
l2_vtr_process (vlib_buffer_t * b0,
                vtr_config_t * config)
{
  u64 temp_8;
  u32 temp_4;
  u8 * eth;

  eth = vlib_buffer_get_current (b0);

  // copy the 12B dmac and smac to a temporary location
  temp_8 = *((u64 *)eth);
  temp_4 = *((u32 *)(eth+8));

  // adjust for popped tags
  eth += config->pop_bytes;

  // if not enough tags to pop then drop packet
  if (PREDICT_FALSE ((vnet_buffer(b0)->l2.l2_len - 12) < config->pop_bytes)) {
    return 1;
  }

  // copy the 2 new tags to the start of the packet 
  *((u64 *)(eth + 12 - 8)) = config->raw_tags;

  // TODO: set cos bits

  // adjust for pushed tags:
  eth -= config->push_bytes;

  // copy the 12 dmac and smac back to the packet
  *((u64 *)eth) = temp_8;
  *((u32 *)(eth+8)) = temp_4;

  // Update l2_len
  vnet_buffer(b0)->l2.l2_len += (word)config->push_bytes - (word)config->pop_bytes;

  // Update vlan tag count
  ethernet_buffer_adjust_vlan_count_by_bytes(b0,
                (word)config->push_bytes - (word)config->pop_bytes);

  // Update packet len
  vlib_buffer_advance(b0, (word)config->pop_bytes - (word)config->push_bytes);

  return 0;
}


// Perform the egress pre-vlan tag rewrite EFP Filter check. The post-vlan tag rewrite
// check is a separate graph node.
//
// This check insures that a packet being output to an interface (before output vtr
// is performed) has vlan tags that match those on a packet received from that
// interface (after vtr has been performed).
// This means verifying that any tags pushed by input vtr are present on the packet.
//
// Return 0 if ok, 1 if packet should be dropped.
// This function should be passed the input vtr config for the interface.
always_inline u8
l2_efp_filter_process (vlib_buffer_t * b0,
                       vtr_config_t * in_config)
{
  u8 * eth;
  u64 packet_tags;
  u64 tag_mask;

  eth = vlib_buffer_get_current (b0);

  // If there are 2 tags pushed, they must match config->tags[0] and config->tags[1].
  // If there is one tag pushed, it must match config->tag[1]. 
  // If there are 0 tags pushed, the check passes.

  // mask for two vlan id and ethertypes, no cos bits
  tag_mask = clib_net_to_host_u64(0xFFFF0FFFFFFF0FFF);
  // mask for one vlan id and ethertype, no cos bits
  tag_mask = (in_config->push_bytes == 4) ? clib_net_to_host_u64(0xFFFF0FFF) : tag_mask;
  // mask for always match
  tag_mask = (in_config->push_bytes == 0) ? 0 : tag_mask;

  // Read 8B from the packet, getting the proper set of vlan tags
  // For 0 push bytes, the address doesn't matter since the mask clears the data to 0.
  packet_tags = *((u64 *)(eth + 4 + in_config->push_bytes));

  // Check if the packet tags match the configured tags
  return (packet_tags & tag_mask) != in_config->raw_tags;
}


// Configure vtag tag rewrite on the given interface.
// Return 1 if there is an error, 0 if ok
u32 l2vtr_configure(vlib_main_t * vlib_main,
                    vnet_main_t * vnet_main,
                    u32           sw_if_index,
                    u32           vtr_op,
                    u32           push_dot1q,
                    u32           vtr_tag1,
                    u32           vtr_tag2);

// Get vtag tag rewrite on the given interface.
// Return 1 if there is an error, 0 if ok
u32 l2vtr_get (vlib_main_t * vlib_main,
               vnet_main_t * vnet_main,
               u32           sw_if_index,
               u32           *vtr_op,
               u32           *push_dot1q,
               u32           *vtr_tag1,
               u32           *vtr_tag2);

#endif // included_vnet_l2_vtr_h