IPFIX support

VPP includes a high-performance IPFIX record exporter. This note explains how to use the internal APIs to export IPFIX data, and how to configure and send the required IPFIX templates.

As you’ll see, a bit of typing is required.

First: create an ipfix “report”

Include the flow report header file, fill out a @ref vnet_flow_report_add_del_args_t structure, and call vnet_flow_report_add_del.

#include <vnet/ipfix-export/flow_report.h>
/* Defined in flow_report.h, of interest when constructing reports */

/* ipfix field definitions for a particular report */
typedef struct
{
  u32 info_element;
  u32 size;
} ipfix_report_element_t;

/* Report add/del argument structure */
typedef struct
{
  /* Callback to flush current ipfix packet / frame */
  vnet_flow_data_callback_t *flow_data_callback;

  /* Callback to build the template packet rewrite string */
  vnet_flow_rewrite_callback_t *rewrite_callback;

  /* List of ipfix elements in the report */
  ipfix_report_element_t *report_elements;
  u32 n_report_elements;
  /* Kept in flow report, used e.g. by flow classifier */
  opaque_t opaque;
  /* Add / delete a report */
  int is_add;
  /* Ipfix "domain-ID", see RFC, set as desired */
  u32 domain_id;
  /* ipfix packet source port, often set to UDP_DST_PORT_ipfix */
  u16 src_port;
  /* Set by ipfix infra, needed to send data packets */
  u32 *stream_indexp;
} vnet_flow_report_add_del_args_t;

/* Private header file contents */

/* Report ipfix element definition */
#define foreach_simple_report_ipfix_element     \
_(sourceIPv4Address, 4)                         \
_(destinationIPv4Address, 4)                    \
_(sourceTransportPort, 2)                       \
_(destinationTransportPort, 2)                  \
_(protocolIdentifier, 1)                        \
_(flowStartMicroseconds, 8)                     \
_(flowEndMicroseconds, 8)

static ipfix_report_element_t simple_report_elements[] = {
#define _(a,b) {a,b},
  foreach_simple_report_ipfix_element
#undef _
};

typedef struct
{
  /** Buffers and frames, per thread */
  vlib_buffer_t **buffers_by_thread;
  vlib_frame_t **frames_by_thread;
  u32 *next_record_offset_by_thread;

  /** Template ID's */
  u16 *template_ids;

  /** Time reference pair */
  u64 usec_time_0;
  f64 vlib_time_0;

  /** Stream index */
  u32 stream_index;

  /* Convenience */
  flow_report_main_t *flow_report_main;
  vlib_main_t *vlib_main;
  vnet_main_t *vnet_main;
} my_logging_main_t;

extern my_logging_main_t my_logging_main;

...

/* Recitations */
flow_report_main_t *frm = &flow_report_main;
my_logging_main_t *mlm = &my_logging_main;
vnet_flow_report_add_del_args_t a;
int rv;
u16 template_id;

...

/* Init function: set up time reference pair */
mlm->vlib_time_0 = vlib_time_now (vm);
mlm->milisecond_time_0 = unix_time_now_nsec () * 1e-6;

...

/* Create a report */
memset (&a, 0, sizeof (a));
a.is_add = 1 /* to enable the report */;
a.domain_id = 1 /* pick a domain ID */;
a.src_port = UDP_DST_PORT_ipfix /* src port for reports */;

/* Use the generic template packet rewrite string generator */
a.rewrite_callback = vnet_flow_rewrite_generic_callback;

/* Supply a list of ipfix report elements */
a.report_elements = simple_report_elements;
a.n_report_elements = ARRAY_LEN (simple_report_elements);

/* Pointer to the ipfix stream index, set by the report infra */
a.stream_indexp = &mlm->stream_index;
a.flow_data_callback = my_flow_data_callback;

/* Create the report */
rv = vnet_flow_report_add_del (frm, &a, &template_id);
if (rv)
  oops...

/* Save the template-ID for later use */
mlm->template_id = template_id;

Several things are worth describing in more detail.

vnet_flow_rewrite_generic_callback programming

This generic callback helps build ipfix template packets. When registering an ipfix report, pass an (array, count) of ipfix elements as shown above.

my_flow_data_callback

The ipfix flow export infrastructure calls this callback to flush the current ipfix packet; to make sure that ipfix data is not retained for an unreasonably long period of time.

We typically code it as shown below, to call an application-specific function with (uninteresting arguments), and “do_flush = 1”:

vlib_frame_t *my_flow_data_callback
             (flow_report_main_t * frm,
         flow_report_t * fr,
     vlib_frame_t * f,
     u32 * to_next, u32 node_index)
{

   my_buffer_flow_record (0, ... , 0, 1 /* do_flush */);
   return f;
}

my_flow_data_header

This function creates the packet header for an ipfix data packet

static inline void
my_flow_report_header (flow_report_main_t * frm,
           vlib_buffer_t * b0, u32 * offset)
{
   my_logging_main_t *mlm = &my_logging_main;
   flow_report_stream_t *stream;
   ip4_ipfix_template_packet_t *tp;
   ipfix_message_header_t *h = 0;


   ipfix_set_header_t *s = 0;
   ip4_header_t *ip;
   udp_header_t *udp;

   stream = &frm->streams[mlm->stream_index];

   b0->current_data = 0;
   b0->current_length = sizeof (*ip) + sizeof (*udp) + sizeof (*h) +
     sizeof (*s);
   b0->flags |= (VLIB_BUFFER_TOTAL_LENGTH_VALID | VNET_BUFFER_F_FLOW_REPORT);
   vnet_buffer (b0)->sw_if_index[VLIB_RX] = 0;
   vnet_buffer (b0)->sw_if_index[VLIB_TX] = frm->fib_index;
   tp = vlib_buffer_get_current (b0);
   ip = (ip4_header_t *) & tp->ip4;
   udp = (udp_header_t *) (ip + 1);
   h = (ipfix_message_header_t *) (udp + 1);
   s = (ipfix_set_header_t *) (h + 1);

   ip->ip_version_and_header_length = 0x45;
   ip->ttl = 254;
   ip->protocol = IP_PROTOCOL_UDP;
   ip->flags_and_fragment_offset = 0;
   ip->src_address.as_u32 = frm->src_address.as_u32;
   ip->dst_address.as_u32 = frm->ipfix_collector.as_u32;
   udp->src_port = clib_host_to_net_u16 (stream->src_port);
   udp->dst_port = clib_host_to_net_u16 (frm->collector_port);
   udp->checksum = 0;

   h->export_time = clib_host_to_net_u32 ((u32)
                          (((f64) frm->unix_time_0) +
                           (vlib_time_now (frm->vlib_main) -
                            frm->vlib_time_0)));
      h->sequence_number = clib_host_to_net_u32 (stream->sequence_number++);
      h->domain_id = clib_host_to_net_u32 (stream->domain_id);

      *offset = (u32) (((u8 *) (s + 1)) - (u8 *) tp);
}

### fixup and transmit a flow record

static inline void
my_send_ipfix_pkt (flow_report_main_t * frm,
           vlib_frame_t * f, vlib_buffer_t * b0, u16 template_id)
{
  ip4_ipfix_template_packet_t *tp;
  ipfix_message_header_t *h = 0;
  ipfix_set_header_t *s = 0;
  ip4_header_t *ip;
  udp_header_t *udp;
  vlib_main_t *vm = frm->vlib_main;

  tp = vlib_buffer_get_current (b0);
  ip = (ip4_header_t *) & tp->ip4;
  udp = (udp_header_t *) (ip + 1);
  h = (ipfix_message_header_t *) (udp + 1);
  s = (ipfix_set_header_t *) (h + 1);

  s->set_id_length = ipfix_set_id_length (template_id,
                    b0->current_length -
                    (sizeof (*ip) + sizeof (*udp) +
                     sizeof (*h)));
  h->version_length = version_length (b0->current_length -
                    (sizeof (*ip) + sizeof (*udp)));

  ip->length = clib_host_to_net_u16 (b0->current_length);
  ip->checksum = ip4_header_checksum (ip);
  udp->length = clib_host_to_net_u16 (b0->current_length - sizeof (*ip));

  if (frm->udp_checksum)
    {
      udp->checksum = ip4_tcp_udp_compute_checksum (vm, b0, ip);
      if (udp->checksum == 0)
  udp->checksum = 0xffff;
    }

  ASSERT (ip4_header_checksum_is_valid (ip));

  vlib_put_frame_to_node (vm, ip4_lookup_node.index, f);
}

### my_buffer_flow_record

This is the key routine which paints individual flow records into an ipfix packet under construction. It’s pretty straightforward (albeit stateful) vpp data-plane code. The code shown below is thread-safe by construction.

static inline void
my_buffer_flow_record_internal (my_flow_record_t * rp, int do_flush,
                                    u32 thread_index)
{
  vlib_main_t *vm = vlib_mains[thread_index];
  my_logging_main_t *mlm = &jvp_ipfix_main;
  flow_report_main_t *frm = &flow_report_main;
  vlib_frame_t *f;
  vlib_buffer_t *b0 = 0;
  u32 bi0 = ~0;
  u32 offset;

  b0 = mlm->buffers_by_thread[thread_index];

  if (PREDICT_FALSE (b0 == 0))
    {
      if (do_flush)
 return;

      if (vlib_buffer_alloc (vm, &bi0, 1) != 1)
 {
   clib_warning ("can't allocate ipfix data buffer");
   return;
 }

      b0 = vlib_get_buffer (vm, bi0);
      offset = 0;
      mlm->buffers_by_thread[thread_index] = b0;
    }
  else
    {
      bi0 = vlib_get_buffer_index (vm, b0);
      offset = mlm->next_record_offset_by_thread[thread_index];
    }

  f = mlm->frames_by_thread[thread_index];
  if (PREDICT_FALSE (f == 0))
    {
      u32 *to_next;
      f = vlib_get_frame_to_node (vm, ip4_lookup_node.index);
      mlm->frames_by_thread[thread_index] = f;
      to_next = vlib_frame_vector_args (f);
      to_next[0] = bi0;
      f->n_vectors = 1;
      mlm->frames_by_thread[thread_index] = f;
    }

  if (PREDICT_FALSE (offset == 0))
    my_flow_report_header (frm, b0, &offset);

  if (PREDICT_TRUE (do_flush == 0))
    {
      /* Paint the new ipfix data record into the buffer */
      clib_memcpy (b0->data + offset, rp, sizeof (*rp));
      offset += sizeof (*rp);
      b0->current_length += sizeof (*rp);
    }

  if (PREDICT_FALSE (do_flush || (offset + sizeof (*rp)) > frm->path_mtu))
    {
      /* Nothing to send? */
      if (offset == 0)
 return;

      send_ipfix_pkt (frm, f, b0, mlm->template_ids[0]);
      mlm->buffers_by_thread[thread_index] = 0;
      mlm->frames_by_thread[thread_index] = 0;
      offset = 0;
    }
  mlm->next_record_offset_by_thread[thread_index] = offset;
}

static void
my_buffer_flow_record (my_flow_record_t * rp, int do_flush)
{
  u32 thread_index = vlib_get_thread_index();
  my_buffer_flow_record_internal (rp, do_flush, thread_index);
}