dhcp_client_detect.c

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/*
 * DHCP feature; applied as an input feature to select DHCP packets
 *
 * 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.
 */

#include <vnet/dhcp/client.h>
#include <vnet/udp/udp.h>

#define foreach_dhcp_client_detect                    \
  _(EXTRACT, "Extract")

typedef enum
{
#define _(sym,str) DHCP_CLIENT_DETECT_ERROR_##sym,
  foreach_dhcp_client_detect
#undef _
    DHCP_CLIENT_DETECT_N_ERROR,
} dhcp_client_detect_error_t;

static char *dhcp_client_detect_error_strings[] = {
#define _(sym,string) string,
  foreach_dhcp_client_detect
#undef _
};

typedef enum
{
#define _(sym,str) DHCP_CLIENT_DETECT_NEXT_##sym,
  foreach_dhcp_client_detect
#undef _
    DHCP_CLIENT_DETECT_N_NEXT,
} dhcp_client_detect_next_t;

/**
 * per-packet trace data
 */
typedef struct dhcp_client_detect_trace_t_
{
  /* per-pkt trace data */
  u8 extracted;
} dhcp_client_detect_trace_t;

static uword
dhcp_client_detect_node_fn (vlib_main_t * vm,
                            vlib_node_runtime_t * node, vlib_frame_t * frame)
{
  dhcp_client_detect_next_t next_index;
  u16 dhcp_client_port_network_order;
  u32 n_left_from, *from, *to_next;
  u32 extractions;

  dhcp_client_port_network_order =
    clib_net_to_host_u16 (UDP_DST_PORT_dhcp_to_client);
  next_index = 0;
  extractions = 0;
  n_left_from = frame->n_vectors;
  from = vlib_frame_vector_args (frame);

  while (n_left_from > 0)
    {
      u32 n_left_to_next;

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

      /*
       * This loop is optimised not so we can really quickly process DHCp
       * offers... but so we can quickly sift them out when the interface
       * is also receving 'normal' packets
       */
      while (n_left_from >= 8 && n_left_to_next >= 4)
        {
          udp_header_t *udp0, *udp1, *udp2, *udp3;
          ip4_header_t *ip0, *ip1, *ip2, *ip3;
          vlib_buffer_t *b0, *b1, *b2, *b3;
          u32 next0, next1, next2, next3;
          u32 bi0, bi1, bi2, bi3;

          next0 = next1 = next2 = next3 = ~0;
          bi0 = to_next[0] = from[0];
          bi1 = to_next[1] = from[1];
          bi2 = to_next[2] = from[2];
          bi3 = to_next[3] = from[3];

          /* Prefetch next iteration. */
          {
            vlib_buffer_t *p2, *p3, *p4, *p5;

            p2 = vlib_get_buffer (vm, from[2]);
            p3 = vlib_get_buffer (vm, from[3]);
            p4 = vlib_get_buffer (vm, from[4]);
            p5 = vlib_get_buffer (vm, from[5]);

            vlib_prefetch_buffer_header (p2, STORE);
            vlib_prefetch_buffer_header (p3, STORE);
            vlib_prefetch_buffer_header (p4, STORE);
            vlib_prefetch_buffer_header (p5, STORE);

            CLIB_PREFETCH (p2->data, sizeof (ip0[0]) + sizeof (udp0[0]),
                           STORE);
            CLIB_PREFETCH (p3->data, sizeof (ip0[0]) + sizeof (udp0[0]),
                           STORE);
            CLIB_PREFETCH (p4->data, sizeof (ip0[0]) + sizeof (udp0[0]),
                           STORE);
            CLIB_PREFETCH (p5->data, sizeof (ip0[0]) + sizeof (udp0[0]),
                           STORE);
          }

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

          b0 = vlib_get_buffer (vm, bi0);
          b1 = vlib_get_buffer (vm, bi1);
          b2 = vlib_get_buffer (vm, bi2);
          b3 = vlib_get_buffer (vm, bi3);
          ip0 = vlib_buffer_get_current (b0);
          ip1 = vlib_buffer_get_current (b1);
          ip2 = vlib_buffer_get_current (b2);
          ip3 = vlib_buffer_get_current (b2);

          vnet_feature_next (&next0, b0);
          vnet_feature_next (&next1, b1);
          vnet_feature_next (&next2, b2);
          vnet_feature_next (&next3, b3);

          if (ip0->protocol == IP_PROTOCOL_UDP)
            {
              udp0 = (udp_header_t *) (ip0 + 1);

              if (dhcp_client_port_network_order == udp0->dst_port)
                {
                  next0 = DHCP_CLIENT_DETECT_NEXT_EXTRACT;
                  extractions++;
                }
            }
          if (ip1->protocol == IP_PROTOCOL_UDP)
            {
              udp1 = (udp_header_t *) (ip1 + 1);

              if (dhcp_client_port_network_order == udp1->dst_port)
                {
                  next1 = DHCP_CLIENT_DETECT_NEXT_EXTRACT;
                  extractions++;
                }
            }
          if (ip2->protocol == IP_PROTOCOL_UDP)
            {
              udp2 = (udp_header_t *) (ip2 + 1);

              if (dhcp_client_port_network_order == udp2->dst_port)
                {
                  next2 = DHCP_CLIENT_DETECT_NEXT_EXTRACT;
                  extractions++;
                }
            }
          if (ip3->protocol == IP_PROTOCOL_UDP)
            {
              udp3 = (udp_header_t *) (ip3 + 1);

              if (dhcp_client_port_network_order == udp3->dst_port)
                {
                  next3 = DHCP_CLIENT_DETECT_NEXT_EXTRACT;
                  extractions++;
                }
            }

          if (PREDICT_FALSE (b0->flags & VLIB_BUFFER_IS_TRACED))
            {
              dhcp_client_detect_trace_t *t =
                vlib_add_trace (vm, node, b0, sizeof (*t));
              t->extracted = (next0 == DHCP_CLIENT_DETECT_NEXT_EXTRACT);
            }
          if (PREDICT_FALSE (b1->flags & VLIB_BUFFER_IS_TRACED))
            {
              dhcp_client_detect_trace_t *t =
                vlib_add_trace (vm, node, b1, sizeof (*t));
              t->extracted = (next1 == DHCP_CLIENT_DETECT_NEXT_EXTRACT);
            }
          if (PREDICT_FALSE (b2->flags & VLIB_BUFFER_IS_TRACED))
            {
              dhcp_client_detect_trace_t *t =
                vlib_add_trace (vm, node, b2, sizeof (*t));
              t->extracted = (next2 == DHCP_CLIENT_DETECT_NEXT_EXTRACT);
            }
          if (PREDICT_FALSE (b3->flags & VLIB_BUFFER_IS_TRACED))
            {
              dhcp_client_detect_trace_t *t =
                vlib_add_trace (vm, node, b3, sizeof (*t));
              t->extracted = (next3 == DHCP_CLIENT_DETECT_NEXT_EXTRACT);
            }

          /* verify speculative enqueue, maybe switch current next frame */
          vlib_validate_buffer_enqueue_x4 (vm, node, next_index,
                                           to_next, n_left_to_next,
                                           bi0, bi1, bi2, bi3,
                                           next0, next1, next2, next3);
        }

      while (n_left_from > 0 && n_left_to_next > 0)
        {
          udp_header_t *udp0;
          vlib_buffer_t *b0;
          ip4_header_t *ip0;
          u32 next0 = ~0;
          u32 bi0;

          bi0 = from[0];
          to_next[0] = bi0;
          from += 1;
          to_next += 1;
          n_left_from -= 1;
          n_left_to_next -= 1;

          b0 = vlib_get_buffer (vm, bi0);
          ip0 = vlib_buffer_get_current (b0);

          /*
           * when this feature is applied on an interface that is already
           * accepting packets (because e.g. the interface has other addresses
           * assigned) we are looking for the preverbial needle in the haystack
           * so assume the packet is not the one we are looking for.
           */
          vnet_feature_next (&next0, b0);

          /*
           * all we are looking for here is DHCP/BOOTP packet-to-client
           * UDO port.
           */
          if (ip0->protocol == IP_PROTOCOL_UDP)
            {
              udp0 = (udp_header_t *) (ip0 + 1);

              if (dhcp_client_port_network_order == udp0->dst_port)
                {
                  next0 = DHCP_CLIENT_DETECT_NEXT_EXTRACT;
                  extractions++;
                }
            }

          if (PREDICT_FALSE (b0->flags & VLIB_BUFFER_IS_TRACED))
            {
              dhcp_client_detect_trace_t *t =
                vlib_add_trace (vm, node, b0, sizeof (*t));
              t->extracted = (next0 == DHCP_CLIENT_DETECT_NEXT_EXTRACT);
            }

          /* verify speculative enqueue, maybe switch current next frame */
          vlib_validate_buffer_enqueue_x1 (vm, node, next_index,
                                           to_next, n_left_to_next,
                                           bi0, next0);
        }

      vlib_put_next_frame (vm, node, next_index, n_left_to_next);
    }

  vlib_node_increment_counter (vm, node->node_index,
                               DHCP_CLIENT_DETECT_ERROR_EXTRACT, extractions);

  return frame->n_vectors;
}

/* packet trace format function */
static u8 *
format_dhcp_client_detect_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 *);
  dhcp_client_detect_trace_t *t =
    va_arg (*args, dhcp_client_detect_trace_t *);

  s = format (s, "dhcp-client-detect: %s", (t->extracted ? "yes" : "no"));

  return s;
}

/* *INDENT-OFF* */
VLIB_REGISTER_NODE (dhcp_client_detect_node) = {
  .function = dhcp_client_detect_node_fn,
  .name = "ip4-dhcp-client-detect",
  .vector_size = sizeof (u32),
  .format_trace = format_dhcp_client_detect_trace,
  .type = VLIB_NODE_TYPE_INTERNAL,

  .n_errors = ARRAY_LEN(dhcp_client_detect_error_strings),
  .error_strings = dhcp_client_detect_error_strings,

  .n_next_nodes = DHCP_CLIENT_DETECT_N_NEXT,
  .next_nodes = {
    /*
     * Jump straight to the UDP dispatch node thus avoiding
     * the RPF checks in ip4-local that will fail
     */
    [DHCP_CLIENT_DETECT_NEXT_EXTRACT] = "ip4-udp-lookup",
  },
};

VLIB_NODE_FUNCTION_MULTIARCH (dhcp_client_detect_node,
                              dhcp_client_detect_node_fn);

VNET_FEATURE_INIT (ip4_dvr_reinject_feat_node, static) =
{
  .arc_name = "ip4-unicast",
  .node_name = "ip4-dhcp-client-detect",
  .runs_before = VNET_FEATURES ("ip4-not-enabled"),
};

/* *INDENT-ON* */

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