Move pcap rx/tx trace code out of the dpdk plugin

Moved code to the ethernet input node, and the interface output
path(s). Since we no longer skip ethernet-input, there's no reason
for device drivers to know anything about pcap rx tracing, etc.

Change-Id: I08d32fb1b90cbee1bd4f609837d533e047b36fa4
Signed-off-by: Dave Barach <dave@barachs.net>

8 files changed, 390 insertions, 388 deletions

diff --git a/src/plugins/dpdk/device/cli.c b/src/plugins/dpdk/device/cli.c
index 41f3fdef838..765b298f8a9 100644
--- a/src/plugins/dpdk/device/cli.c
+++ b/src/plugins/dpdk/device/cli.c
@@ -95,291 +95,6 @@ done:
 }
 #endif
 
-static inline clib_error_t *
-pcap_trace_command_internal (vlib_main_t * vm,
-			     unformat_input_t * input,
-			     vlib_cli_command_t * cmd, int rx_tx)
-{
-#define PCAP_DEF_PKT_TO_CAPTURE (100)
-
-  unformat_input_t _line_input, *line_input = &_line_input;
-  dpdk_main_t *dm = &dpdk_main;
-  u8 *filename;
-  u8 *chroot_filename = 0;
-  u32 max = 0;
-  int enabled = 0;
-  int errorFlag = 0;
-  clib_error_t *error = 0;
-
-  /* Get a line of input. */
-  if (!unformat_user (input, unformat_line_input, line_input))
-    return 0;
-
-  while (unformat_check_input (line_input) != UNFORMAT_END_OF_INPUT)
-    {
-      if (unformat (line_input, "on"))
-	{
-	  if (dm->pcap[rx_tx].pcap_enable == 0)
-	    {
-	      enabled = 1;
-	    }
-	  else
-	    {
-	      vlib_cli_output (vm, "pcap tx capture already on...");
-	      errorFlag = 1;
-	      break;
-	    }
-	}
-      else if (unformat (line_input, "off"))
-	{
-	  if (dm->pcap[rx_tx].pcap_enable)
-	    {
-	      vlib_cli_output
-		(vm, "captured %d pkts...",
-		 dm->pcap[rx_tx].pcap_main.n_packets_captured);
-	      if (dm->pcap[rx_tx].pcap_main.n_packets_captured)
-		{
-		  dm->pcap[rx_tx].pcap_main.n_packets_to_capture =
-		    dm->pcap[rx_tx].pcap_main.n_packets_captured;
-		  error = pcap_write (&dm->pcap[rx_tx].pcap_main);
-		  if (error)
-		    clib_error_report (error);
-		  else
-		    vlib_cli_output (vm, "saved to %s...",
-				     dm->pcap[rx_tx].pcap_main.file_name);
-		}
-
-	      dm->pcap[rx_tx].pcap_enable = 0;
-	    }
-	  else
-	    {
-	      vlib_cli_output (vm, "pcap tx capture already off...");
-	      errorFlag = 1;
-	      break;
-	    }
-	}
-      else if (unformat (line_input, "max %d", &max))
-	{
-	  if (dm->pcap[rx_tx].pcap_enable)
-	    {
-	      vlib_cli_output
-		(vm,
-		 "can't change max value while pcap tx capture active...");
-	      errorFlag = 1;
-	      break;
-	    }
-	  dm->pcap[rx_tx].pcap_main.n_packets_to_capture = max;
-	}
-      else if (unformat (line_input, "intfc %U",
-			 unformat_vnet_sw_interface, dm->vnet_main,
-			 &dm->pcap[rx_tx].pcap_sw_if_index))
-	;
-
-      else if (unformat (line_input, "intfc any"))
-	{
-	  dm->pcap[rx_tx].pcap_sw_if_index = 0;
-	}
-      else if (unformat (line_input, "file %s", &filename))
-	{
-	  if (dm->pcap[rx_tx].pcap_enable)
-	    {
-	      vlib_cli_output
-		(vm, "can't change file while pcap tx capture active...");
-	      errorFlag = 1;
-	      break;
-	    }
-
-	  /* Brain-police user path input */
-	  if (strstr ((char *) filename, "..")
-	      || index ((char *) filename, '/'))
-	    {
-	      vlib_cli_output (vm, "illegal characters in filename '%s'",
-			       filename);
-	      vlib_cli_output (vm, "Hint: .. and / are not allowed.");
-	      vec_free (filename);
-	      errorFlag = 1;
-	      break;
-	    }
-
-	  chroot_filename = format (0, "/tmp/%s%c", filename, 0);
-	  vec_free (filename);
-	}
-      else if (unformat (line_input, "status"))
-	{
-	  if (dm->pcap[rx_tx].pcap_sw_if_index == 0)
-	    {
-	      vlib_cli_output
-		(vm, "max is %d for any interface to file %s",
-		 dm->pcap[rx_tx].pcap_main.n_packets_to_capture ?
-		 dm->pcap[rx_tx].pcap_main.n_packets_to_capture
-		 : PCAP_DEF_PKT_TO_CAPTURE,
-		 dm->pcap[rx_tx].pcap_main.file_name ?
-		 (u8 *) dm->pcap[rx_tx].pcap_main.file_name :
-		 (u8 *) "/tmp/vpe.pcap");
-	    }
-	  else
-	    {
-	      vlib_cli_output (vm, "max is %d for interface %U to file %s",
-			       dm->pcap[rx_tx].pcap_main.n_packets_to_capture
-			       ? dm->pcap[rx_tx].
-			       pcap_main.n_packets_to_capture :
-			       PCAP_DEF_PKT_TO_CAPTURE,
-			       format_vnet_sw_if_index_name, dm->vnet_main,
-			       dm->pcap_sw_if_index,
-			       dm->pcap[rx_tx].
-			       pcap_main.file_name ? (u8 *) dm->pcap[rx_tx].
-			       pcap_main.file_name : (u8 *) "/tmp/vpe.pcap");
-	    }
-
-	  if (dm->pcap[rx_tx].pcap_enable == 0)
-	    {
-	      vlib_cli_output (vm, "pcap %s capture is off...",
-			       (rx_tx == VLIB_RX) ? "rx" : "tx");
-	    }
-	  else
-	    {
-	      vlib_cli_output (vm, "pcap %s capture is on: %d of %d pkts...",
-			       (rx_tx == VLIB_RX) ? "rx" : "tx",
-			       dm->pcap[rx_tx].pcap_main.n_packets_captured,
-			       dm->pcap[rx_tx].
-			       pcap_main.n_packets_to_capture);
-	    }
-	  break;
-	}
-
-      else
-	{
-	  error = clib_error_return (0, "unknown input `%U'",
-				     format_unformat_error, line_input);
-	  errorFlag = 1;
-	  break;
-	}
-    }
-  unformat_free (line_input);
-
-
-  if (errorFlag == 0)
-    {
-      /* Since no error, save configured values. */
-      if (chroot_filename)
-	{
-	  if (dm->pcap[rx_tx].pcap_main.file_name)
-	    vec_free (dm->pcap[rx_tx].pcap_main.file_name);
-	  vec_add1 (chroot_filename, 0);
-	  dm->pcap[rx_tx].pcap_main.file_name = (char *) chroot_filename;
-	}
-
-      if (max)
-	dm->pcap[rx_tx].pcap_main.n_packets_to_capture = max;
-
-      if (enabled)
-	{
-	  if (dm->pcap[rx_tx].pcap_main.file_name == 0)
-	    dm->pcap[rx_tx].pcap_main.file_name
-	      = (char *) format (0, "/tmp/vpe.pcap%c", 0);
-
-	  dm->pcap[rx_tx].pcap_main.n_packets_captured = 0;
-	  dm->pcap[rx_tx].pcap_main.packet_type = PCAP_PACKET_TYPE_ethernet;
-	  if (dm->pcap[rx_tx].pcap_main.lock == 0)
-	    clib_spinlock_init (&(dm->pcap[rx_tx].pcap_main.lock));
-	  dm->pcap[rx_tx].pcap_enable = 1;
-	  vlib_cli_output (vm, "pcap %s capture on...",
-			   rx_tx == VLIB_RX ? "rx" : "tx");
-	}
-    }
-  else if (chroot_filename)
-    vec_free (chroot_filename);
-
-  return error;
-}
-
-static clib_error_t *
-pcap_rx_trace_command_fn (vlib_main_t * vm,
-			  unformat_input_t * input, vlib_cli_command_t * cmd)
-{
-  return pcap_trace_command_internal (vm, input, cmd, VLIB_RX);
-}
-
-static clib_error_t *
-pcap_tx_trace_command_fn (vlib_main_t * vm,
-			  unformat_input_t * input, vlib_cli_command_t * cmd)
-{
-  return pcap_trace_command_internal (vm, input, cmd, VLIB_TX);
-}
-
-
-/*?
- * This command is used to start or stop a packet capture, or show
- * the status of packet capture. Note that both "pcap rx trace" and
- * "pcap tx trace" are implemented. The command syntax is identical,
- * simply substitute rx for tx as needed.
- *
- * This command has the following optional parameters:
- *
- * - <b>on|off</b> - Used to start or stop a packet capture.
- *
- * - <b>max <nn></b> - Depth of local buffer. Once '<em>nn</em>' number
- *   of packets have been received, buffer is flushed to file. Once another
- *   '<em>nn</em>' number of packets have been received, buffer is flushed
- *   to file, overwriting previous write. If not entered, value defaults
- *   to 100. Can only be updated if packet capture is off.
- *
- * - <b>intfc <interface>|any</b> - Used to specify a given interface,
- *   or use '<em>any</em>' to run packet capture on all interfaces.
- *   '<em>any</em>' is the default if not provided. Settings from a previous
- *   packet capture are preserved, so '<em>any</em>' can be used to reset
- *   the interface setting.
- *
- * - <b>file <name></b> - Used to specify the output filename. The file will
- *   be placed in the '<em>/tmp</em>' directory, so only the filename is
- *   supported. Directory should not be entered. If file already exists, file
- *   will be overwritten. If no filename is provided, '<em>/tmp/vpe.pcap</em>'
- *   will be used. Can only be updated if packet capture is off.
- *
- * - <b>status</b> - Displays the current status and configured attributes
- *   associated with a packet capture. If packet capture is in progress,
- *   '<em>status</em>' also will return the number of packets currently in
- *   the local buffer. All additional attributes entered on command line
- *   with '<em>status</em>' will be ignored and not applied.
- *
- * @cliexpar
- * Example of how to display the status of a tx packet capture when off:
- * @cliexstart{pcap tx trace status}
- * max is 100, for any interface to file /tmp/vpe.pcap
- * pcap tx capture is off...
- * @cliexend
- * Example of how to start a tx packet capture:
- * @cliexstart{pcap tx trace on max 35 intfc GigabitEthernet0/8/0 file vppTest.pcap}
- * pcap tx capture on...
- * @cliexend
- * Example of how to display the status of a tx packet capture in progress:
- * @cliexstart{pcap tx trace status}
- * max is 35, for interface GigabitEthernet0/8/0 to file /tmp/vppTest.pcap
- * pcap tx capture is on: 20 of 35 pkts...
- * @cliexend
- * Example of how to stop a tx packet capture:
- * @cliexstart{vppctl pcap tx trace off}
- * captured 21 pkts...
- * saved to /tmp/vppTest.pcap...
- * @cliexend
-?*/
-/* *INDENT-OFF* */
-
-VLIB_CLI_COMMAND (pcap_tx_trace_command, static) = {
-    .path = "pcap tx trace",
-    .short_help =
-    "pcap tx trace [on|off] [max <nn>] [intfc <interface>|any] [file <name>] [status]",
-    .function = pcap_tx_trace_command_fn,
-};
-VLIB_CLI_COMMAND (pcap_rx_trace_command, static) = {
-    .path = "pcap rx trace",
-    .short_help =
-    "pcap rx trace [on|off] [max <nn>] [intfc <interface>|any] [file <name>] [status]",
-    .function = pcap_rx_trace_command_fn,
-};
-/* *INDENT-ON* */
-
-
 static clib_error_t *
 show_dpdk_buffer (vlib_main_t * vm, unformat_input_t * input,
 		  vlib_cli_command_t * cmd)
diff --git a/src/plugins/dpdk/device/device.c b/src/plugins/dpdk/device/device.c
index 466abc37e68..6285d93ac96 100644
--- a/src/plugins/dpdk/device/device.c
+++ b/src/plugins/dpdk/device/device.c
@@ -271,7 +271,6 @@ VNET_DEVICE_CLASS_TX_FN (dpdk_device_class) (vlib_main_t * vm,
   dpdk_device_t *xd = vec_elt_at_index (dm->devices, rd->dev_instance);
   u32 n_packets = f->n_vectors;
   u32 n_left;
-  u32 *from;
   u32 thread_index = vm->thread_index;
   int queue_id = thread_index;
   u32 tx_pkts = 0, all_or_flags = 0;
@@ -280,33 +279,13 @@ VNET_DEVICE_CLASS_TX_FN (dpdk_device_class) (vlib_main_t * vm,
   struct rte_mbuf **mb;
   vlib_buffer_t *b[4];
 
-  from = vlib_frame_vector_args (f);
-
   ASSERT (n_packets <= VLIB_FRAME_SIZE);
 
-  /* TX PCAP tracing */
-  if (PREDICT_FALSE (dm->pcap[VLIB_TX].pcap_enable))
-    {
-      n_left = n_packets;
-      while (n_left > 0)
-	{
-	  u32 bi0 = from[0];
-	  vlib_buffer_t *b0 = vlib_get_buffer (vm, bi0);
-	  if (dm->pcap[VLIB_TX].pcap_sw_if_index == 0 ||
-	      dm->pcap[VLIB_TX].pcap_sw_if_index
-	      == vnet_buffer (b0)->sw_if_index[VLIB_TX])
-	    pcap_add_buffer (&dm->pcap[VLIB_TX].pcap_main, vm, bi0, 512);
-	  from++;
-	  n_left--;
-	}
-    }
-
   /* calculate rte_mbuf pointers out of buffer indices */
   vlib_get_buffers_with_offset (vm, vlib_frame_vector_args (f),
 				(void **) ptd->mbufs, n_packets,
 				-(i32) sizeof (struct rte_mbuf));
 
-  from = vlib_frame_vector_args (f);
   n_left = n_packets;
   mb = ptd->mbufs;
 
diff --git a/src/plugins/dpdk/device/dpdk.h b/src/plugins/dpdk/device/dpdk.h
index b2ca56cbe4d..5d8368b06c3 100644
--- a/src/plugins/dpdk/device/dpdk.h
+++ b/src/plugins/dpdk/device/dpdk.h
@@ -44,7 +44,6 @@
 #include <rte_bus_pci.h>
 #include <rte_flow.h>
 
-#include <vppinfra/pcap.h>
 #include <vnet/devices/devices.h>
 
 #if CLIB_DEBUG > 0
@@ -399,13 +398,6 @@ typedef struct
 
 typedef struct
 {
-  int pcap_enable;
-  u32 pcap_sw_if_index;
-  pcap_main_t pcap_main;
-} dpdk_pcap_t;
-
-typedef struct
-{
 
   /* Devices */
   dpdk_device_t *devices;
@@ -415,15 +407,6 @@ typedef struct
   /* buffer flags template, configurable to enable/disable tcp / udp cksum */
   u32 buffer_flags_template;
 
-  /* pcap tracing */
-  dpdk_pcap_t pcap[VLIB_N_RX_TX];
-
-  int pcap_enable;
-  pcap_main_t pcap_main;
-  u8 *pcap_filename;
-  u32 pcap_sw_if_index;
-  u32 pcap_pkts_to_capture;
-
   /*
    * flag indicating that a posted admin up/down
    * (via post_sw_interface_set_flags) is in progress
diff --git a/src/plugins/dpdk/device/node.c b/src/plugins/dpdk/device/node.c
index 31ca5419ee4..4edce1a3677 100644
--- a/src/plugins/dpdk/device/node.c
+++ b/src/plugins/dpdk/device/node.c
@@ -438,54 +438,6 @@ dpdk_device_input (vlib_main_t * vm, dpdk_main_t * dm, dpdk_device_t * xd,
       vlib_set_trace_count (vm, node, n_trace);
     }
 
-  /* rx pcap capture if enabled */
-  if (PREDICT_FALSE (dm->pcap[VLIB_RX].pcap_enable))
-    {
-      u32 bi0;
-
-      if (single_next)
-	vlib_get_buffer_indices_with_offset (vm, (void **) ptd->mbufs,
-					     ptd->buffers, n_rx_packets,
-					     sizeof (struct rte_mbuf));
-
-      n_left = n_rx_packets;
-      buffers = ptd->buffers;
-      while (n_left)
-	{
-	  bi0 = buffers[0];
-	  b0 = vlib_get_buffer (vm, bi0);
-	  buffers++;
-
-	  if (dm->pcap[VLIB_RX].pcap_sw_if_index == 0 ||
-	      dm->pcap[VLIB_RX].pcap_sw_if_index
-	      == vnet_buffer (b0)->sw_if_index[VLIB_RX])
-	    {
-	      struct rte_mbuf *mb;
-	      i16 data_start;
-	      i32 temp_advance;
-
-	      /*
-	       * Note: current_data will have advanced
-	       * when we skip ethernet input.
-	       * Temporarily back up to the original DMA
-	       * target, so we capture a valid ethernet frame
-	       */
-	      mb = rte_mbuf_from_vlib_buffer (b0);
-
-	      /* Figure out the original data_start */
-	      data_start = (mb->buf_addr + mb->data_off) - (void *) b0->data;
-	      /* Back up that far */
-	      temp_advance = b0->current_data - data_start;
-	      vlib_buffer_advance (b0, -temp_advance);
-	      /* Trace the packet */
-	      pcap_add_buffer (&dm->pcap[VLIB_RX].pcap_main, vm, bi0, 512);
-	      /* and advance again */
-	      vlib_buffer_advance (b0, temp_advance);
-	    }
-	  n_left--;
-	}
-    }
-
   vlib_increment_combined_counter
     (vnet_get_main ()->interface_main.combined_sw_if_counters
      + VNET_INTERFACE_COUNTER_RX, thread_index, xd->sw_if_index,
diff --git a/src/vlib/main.h b/src/vlib/main.h
index 4192c3f2720..2c5bb45417f 100644
--- a/src/vlib/main.h
+++ b/src/vlib/main.h
@@ -58,6 +58,13 @@
 #define VLIB_ELOG_MAIN_LOOP 0
 #endif
 
+typedef struct
+{
+  int pcap_enable;
+  u32 pcap_sw_if_index;
+  pcap_main_t pcap_main;
+} vnet_pcap_t;
+
 typedef struct vlib_main_t
 {
   CLIB_CACHE_LINE_ALIGN_MARK (cacheline0);
@@ -138,6 +145,15 @@ typedef struct vlib_main_t
   uword dispatch_pcap_enable;
   u8 *pcap_buffer;
 
+  /* pcap rx / tx tracing */
+  vnet_pcap_t pcap[VLIB_N_RX_TX];
+
+  int pcap_enable;
+  pcap_main_t pcap_main;
+  u8 *pcap_filename;
+  u32 pcap_sw_if_index;
+  u32 pcap_pkts_to_capture;
+
   /* Error handling. */
   vlib_error_main_t error_main;
 
diff --git a/src/vnet/ethernet/node.c b/src/vnet/ethernet/node.c
index 3264bdc03af..950a962217c 100755
--- a/src/vnet/ethernet/node.c
+++ b/src/vnet/ethernet/node.c
@@ -963,29 +963,54 @@ ethernet_input_trace (vlib_main_t * vm, vlib_node_runtime_t * node,
 		      vlib_frame_t * from_frame)
 {
   u32 *from, n_left;
-  if ((node->flags & VLIB_NODE_FLAG_TRACE) == 0)
-    return;
+  if (PREDICT_FALSE ((node->flags & VLIB_NODE_FLAG_TRACE) == 0))
+    {
+      from = vlib_frame_vector_args (from_frame);
+      n_left = from_frame->n_vectors;
 
-  from = vlib_frame_vector_args (from_frame);
-  n_left = from_frame->n_vectors;
+      while (n_left)
+	{
+	  ethernet_input_trace_t *t0;
+	  vlib_buffer_t *b0 = vlib_get_buffer (vm, from[0]);
 
-  while (n_left)
+	  if (b0->flags & VLIB_BUFFER_IS_TRACED)
+	    {
+	      t0 = vlib_add_trace (vm, node, b0,
+				   sizeof (ethernet_input_trace_t));
+	      clib_memcpy_fast (t0->packet_data, b0->data + b0->current_data,
+				sizeof (t0->packet_data));
+	      t0->frame_flags = from_frame->flags;
+	      clib_memcpy_fast (&t0->frame_data,
+				vlib_frame_scalar_args (from_frame),
+				sizeof (ethernet_input_frame_t));
+	    }
+	  from += 1;
+	  n_left -= 1;
+	}
+    }
+
+  /* rx pcap capture if enabled */
+  if (PREDICT_FALSE (vm->pcap[VLIB_RX].pcap_enable))
     {
-      ethernet_input_trace_t *t0;
-      vlib_buffer_t *b0 = vlib_get_buffer (vm, from[0]);
+      u32 bi0;
 
-      if (b0->flags & VLIB_BUFFER_IS_TRACED)
+      from = vlib_frame_vector_args (from_frame);
+      n_left = from_frame->n_vectors;
+      while (n_left > 0)
 	{
-	  t0 = vlib_add_trace (vm, node, b0, sizeof (ethernet_input_trace_t));
-	  clib_memcpy_fast (t0->packet_data, b0->data + b0->current_data,
-			    sizeof (t0->packet_data));
-	  t0->frame_flags = from_frame->flags;
-	  clib_memcpy_fast (&t0->frame_data,
-			    vlib_frame_scalar_args (from_frame),
-			    sizeof (ethernet_input_frame_t));
+	  vlib_buffer_t *b0;
+	  bi0 = from[0];
+	  from++;
+	  b0 = vlib_get_buffer (vm, bi0);
+
+	  if (vm->pcap[VLIB_RX].pcap_sw_if_index == 0 ||
+	      vm->pcap[VLIB_RX].pcap_sw_if_index
+	      == vnet_buffer (b0)->sw_if_index[VLIB_RX])
+	    {
+	      pcap_add_buffer (&vm->pcap[VLIB_RX].pcap_main, vm, bi0, 512);
+	    }
+	  n_left--;
 	}
-      from += 1;
-      n_left -= 1;
     }
 }
 
diff --git a/src/vnet/interface_cli.c b/src/vnet/interface_cli.c
index b15d283fe49..12310eba52a 100644
--- a/src/vnet/interface_cli.c
+++ b/src/vnet/interface_cli.c
@@ -1705,6 +1705,292 @@ VLIB_CLI_COMMAND (cmd_set_if_rx_placement,static) = {
     .is_mp_safe = 1,
 };
 /* *INDENT-ON* */
+
+static inline clib_error_t *
+pcap_trace_command_internal (vlib_main_t * vm,
+			     unformat_input_t * input,
+			     vlib_cli_command_t * cmd, int rx_tx)
+{
+#define PCAP_DEF_PKT_TO_CAPTURE (1000)
+
+  unformat_input_t _line_input, *line_input = &_line_input;
+  u8 *filename;
+  u8 *chroot_filename = 0;
+  u32 max = 0;
+  int enabled = 0;
+  int errorFlag = 0;
+  clib_error_t *error = 0;
+  vnet_main_t *vnm = vnet_get_main ();
+
+  /* Get a line of input. */
+  if (!unformat_user (input, unformat_line_input, line_input))
+    return 0;
+
+  while (unformat_check_input (line_input) != UNFORMAT_END_OF_INPUT)
+    {
+      if (unformat (line_input, "on"))
+	{
+	  if (vm->pcap[rx_tx].pcap_enable == 0)
+	    {
+	      enabled = 1;
+	    }
+	  else
+	    {
+	      vlib_cli_output (vm, "pcap tx capture already on...");
+	      errorFlag = 1;
+	      break;
+	    }
+	}
+      else if (unformat (line_input, "off"))
+	{
+	  if (vm->pcap[rx_tx].pcap_enable)
+	    {
+	      vlib_cli_output
+		(vm, "captured %d pkts...",
+		 vm->pcap[rx_tx].pcap_main.n_packets_captured);
+	      if (vm->pcap[rx_tx].pcap_main.n_packets_captured)
+		{
+		  vm->pcap[rx_tx].pcap_main.n_packets_to_capture =
+		    vm->pcap[rx_tx].pcap_main.n_packets_captured;
+		  error = pcap_write (&vm->pcap[rx_tx].pcap_main);
+		  if (error)
+		    clib_error_report (error);
+		  else
+		    vlib_cli_output (vm, "saved to %s...",
+				     vm->pcap[rx_tx].pcap_main.file_name);
+		}
+
+	      vm->pcap[rx_tx].pcap_enable = 0;
+	    }
+	  else
+	    {
+	      vlib_cli_output (vm, "pcap tx capture already off...");
+	      errorFlag = 1;
+	      break;
+	    }
+	}
+      else if (unformat (line_input, "max %d", &max))
+	{
+	  if (vm->pcap[rx_tx].pcap_enable)
+	    {
+	      vlib_cli_output
+		(vm,
+		 "can't change max value while pcap tx capture active...");
+	      errorFlag = 1;
+	      break;
+	    }
+	  vm->pcap[rx_tx].pcap_main.n_packets_to_capture = max;
+	}
+      else if (unformat (line_input, "intfc %U",
+			 unformat_vnet_sw_interface, vnm,
+			 &vm->pcap[rx_tx].pcap_sw_if_index))
+	;
+
+      else if (unformat (line_input, "intfc any"))
+	{
+	  vm->pcap[rx_tx].pcap_sw_if_index = 0;
+	}
+      else if (unformat (line_input, "file %s", &filename))
+	{
+	  if (vm->pcap[rx_tx].pcap_enable)
+	    {
+	      vlib_cli_output
+		(vm, "can't change file while pcap tx capture active...");
+	      errorFlag = 1;
+	      break;
+	    }
+
+	  /* Brain-police user path input */
+	  if (strstr ((char *) filename, "..")
+	      || index ((char *) filename, '/'))
+	    {
+	      vlib_cli_output (vm, "illegal characters in filename '%s'",
+			       filename);
+	      vlib_cli_output (vm, "Hint: .. and / are not allowed.");
+	      vec_free (filename);
+	      errorFlag = 1;
+	      break;
+	    }
+
+	  chroot_filename = format (0, "/tmp/%s%c", filename, 0);
+	  vec_free (filename);
+	}
+      else if (unformat (line_input, "status"))
+	{
+	  if (vm->pcap[rx_tx].pcap_sw_if_index == 0)
+	    {
+	      vlib_cli_output
+		(vm, "max is %d for any interface to file %s",
+		 vm->pcap[rx_tx].pcap_main.n_packets_to_capture ?
+		 vm->pcap[rx_tx].pcap_main.n_packets_to_capture
+		 : PCAP_DEF_PKT_TO_CAPTURE,
+		 vm->pcap[rx_tx].pcap_main.file_name ?
+		 (u8 *) vm->pcap[rx_tx].pcap_main.file_name :
+		 (u8 *) "/tmp/vpe.pcap");
+	    }
+	  else
+	    {
+	      vlib_cli_output (vm, "max is %d for interface %U to file %s",
+			       vm->pcap[rx_tx].pcap_main.n_packets_to_capture
+			       ? vm->pcap[rx_tx].
+			       pcap_main.n_packets_to_capture :
+			       PCAP_DEF_PKT_TO_CAPTURE,
+			       format_vnet_sw_if_index_name, vnm,
+			       vm->pcap_sw_if_index,
+			       vm->pcap[rx_tx].
+			       pcap_main.file_name ? (u8 *) vm->pcap[rx_tx].
+			       pcap_main.file_name : (u8 *) "/tmp/vpe.pcap");
+	    }
+
+	  if (vm->pcap[rx_tx].pcap_enable == 0)
+	    {
+	      vlib_cli_output (vm, "pcap %s capture is off...",
+			       (rx_tx == VLIB_RX) ? "rx" : "tx");
+	    }
+	  else
+	    {
+	      vlib_cli_output (vm, "pcap %s capture is on: %d of %d pkts...",
+			       (rx_tx == VLIB_RX) ? "rx" : "tx",
+			       vm->pcap[rx_tx].pcap_main.n_packets_captured,
+			       vm->pcap[rx_tx].
+			       pcap_main.n_packets_to_capture);
+	    }
+	  break;
+	}
+
+      else
+	{
+	  error = clib_error_return (0, "unknown input `%U'",
+				     format_unformat_error, line_input);
+	  errorFlag = 1;
+	  break;
+	}
+    }
+  unformat_free (line_input);
+
+
+  if (errorFlag == 0)
+    {
+      /* Since no error, save configured values. */
+      if (chroot_filename)
+	{
+	  if (vm->pcap[rx_tx].pcap_main.file_name)
+	    vec_free (vm->pcap[rx_tx].pcap_main.file_name);
+	  vec_add1 (chroot_filename, 0);
+	  vm->pcap[rx_tx].pcap_main.file_name = (char *) chroot_filename;
+	}
+
+      if (max)
+	vm->pcap[rx_tx].pcap_main.n_packets_to_capture = max;
+
+      if (enabled)
+	{
+	  if (vm->pcap[rx_tx].pcap_main.file_name == 0)
+	    vm->pcap[rx_tx].pcap_main.file_name
+	      = (char *) format (0, "/tmp/vpe.pcap%c", 0);
+
+	  vm->pcap[rx_tx].pcap_main.n_packets_captured = 0;
+	  vm->pcap[rx_tx].pcap_main.packet_type = PCAP_PACKET_TYPE_ethernet;
+	  if (vm->pcap[rx_tx].pcap_main.lock == 0)
+	    clib_spinlock_init (&(vm->pcap[rx_tx].pcap_main.lock));
+	  vm->pcap[rx_tx].pcap_enable = 1;
+	  vlib_cli_output (vm, "pcap %s capture on...",
+			   rx_tx == VLIB_RX ? "rx" : "tx");
+	}
+    }
+  else if (chroot_filename)
+    vec_free (chroot_filename);
+
+  return error;
+}
+
+static clib_error_t *
+pcap_rx_trace_command_fn (vlib_main_t * vm,
+			  unformat_input_t * input, vlib_cli_command_t * cmd)
+{
+  return pcap_trace_command_internal (vm, input, cmd, VLIB_RX);
+}
+
+static clib_error_t *
+pcap_tx_trace_command_fn (vlib_main_t * vm,
+			  unformat_input_t * input, vlib_cli_command_t * cmd)
+{
+  return pcap_trace_command_internal (vm, input, cmd, VLIB_TX);
+}
+
+
+/*?
+ * This command is used to start or stop a packet capture, or show
+ * the status of packet capture. Note that both "pcap rx trace" and
+ * "pcap tx trace" are implemented. The command syntax is identical,
+ * simply substitute rx for tx as needed.
+ *
+ * This command has the following optional parameters:
+ *
+ * - <b>on|off</b> - Used to start or stop a packet capture.
+ *
+ * - <b>max <nn></b> - Depth of local buffer. Once '<em>nn</em>' number
+ *   of packets have been received, buffer is flushed to file. Once another
+ *   '<em>nn</em>' number of packets have been received, buffer is flushed
+ *   to file, overwriting previous write. If not entered, value defaults
+ *   to 100. Can only be updated if packet capture is off.
+ *
+ * - <b>intfc <interface>|any</b> - Used to specify a given interface,
+ *   or use '<em>any</em>' to run packet capture on all interfaces.
+ *   '<em>any</em>' is the default if not provided. Settings from a previous
+ *   packet capture are preserved, so '<em>any</em>' can be used to reset
+ *   the interface setting.
+ *
+ * - <b>file <name></b> - Used to specify the output filename. The file will
+ *   be placed in the '<em>/tmp</em>' directory, so only the filename is
+ *   supported. Directory should not be entered. If file already exists, file
+ *   will be overwritten. If no filename is provided, '<em>/tmp/vpe.pcap</em>'
+ *   will be used. Can only be updated if packet capture is off.
+ *
+ * - <b>status</b> - Displays the current status and configured attributes
+ *   associated with a packet capture. If packet capture is in progress,
+ *   '<em>status</em>' also will return the number of packets currently in
+ *   the local buffer. All additional attributes entered on command line
+ *   with '<em>status</em>' will be ignored and not applied.
+ *
+ * @cliexpar
+ * Example of how to display the status of a tx packet capture when off:
+ * @cliexstart{pcap tx trace status}
+ * max is 100, for any interface to file /tmp/vpe.pcap
+ * pcap tx capture is off...
+ * @cliexend
+ * Example of how to start a tx packet capture:
+ * @cliexstart{pcap tx trace on max 35 intfc GigabitEthernet0/8/0 file vppTest.pcap}
+ * pcap tx capture on...
+ * @cliexend
+ * Example of how to display the status of a tx packet capture in progress:
+ * @cliexstart{pcap tx trace status}
+ * max is 35, for interface GigabitEthernet0/8/0 to file /tmp/vppTest.pcap
+ * pcap tx capture is on: 20 of 35 pkts...
+ * @cliexend
+ * Example of how to stop a tx packet capture:
+ * @cliexstart{vppctl pcap tx trace off}
+ * captured 21 pkts...
+ * saved to /tmp/vppTest.pcap...
+ * @cliexend
+?*/
+/* *INDENT-OFF* */
+
+VLIB_CLI_COMMAND (pcap_tx_trace_command, static) = {
+    .path = "pcap tx trace",
+    .short_help =
+    "pcap tx trace [on|off] [max <nn>] [intfc <interface>|any] [file <name>] [status]",
+    .function = pcap_tx_trace_command_fn,
+};
+VLIB_CLI_COMMAND (pcap_rx_trace_command, static) = {
+    .path = "pcap rx trace",
+    .short_help =
+    "pcap rx trace [on|off] [max <nn>] [intfc <interface>|any] [file <name>] [status]",
+    .function = pcap_rx_trace_command_fn,
+};
+/* *INDENT-ON* */
+
+
 /*
  * fd.io coding-style-patch-verification: ON
  *
diff --git a/src/vnet/interface_output.c b/src/vnet/interface_output.c
index 251ff34ac9a..6c2345be270 100644
--- a/src/vnet/interface_output.c
+++ b/src/vnet/interface_output.c
@@ -802,6 +802,43 @@ vnet_interface_output_node_inline_gso (vlib_main_t * vm,
   return n_buffers;
 }
 
+static_always_inline void vnet_interface_pcap_tx_trace
+  (vlib_main_t * vm, vlib_node_runtime_t * node, vlib_frame_t * frame,
+   int sw_if_index_from_buffer)
+{
+  u32 n_left_from, *from;
+  u32 sw_if_index;
+
+  if (PREDICT_TRUE (vm->pcap[VLIB_TX].pcap_enable == 0))
+    return;
+
+  if (sw_if_index_from_buffer == 0)
+    {
+      vnet_interface_output_runtime_t *rt = (void *) node->runtime_data;
+      sw_if_index = rt->sw_if_index;
+    }
+  else
+    sw_if_index = ~0;
+
+  n_left_from = frame->n_vectors;
+  from = vlib_frame_vector_args (frame);
+
+  while (n_left_from > 0)
+    {
+      u32 bi0 = from[0];
+      vlib_buffer_t *b0 = vlib_get_buffer (vm, bi0);
+
+      if (sw_if_index_from_buffer)
+	sw_if_index = vnet_buffer (b0)->sw_if_index[VLIB_TX];
+
+      if (vm->pcap[VLIB_TX].pcap_sw_if_index == 0 ||
+	  vm->pcap[VLIB_TX].pcap_sw_if_index == sw_if_index)
+	pcap_add_buffer (&vm->pcap[VLIB_TX].pcap_main, vm, bi0, 512);
+      from++;
+      n_left_from--;
+    }
+}
+
 static_always_inline uword
 vnet_interface_output_node_inline (vlib_main_t * vm,
 				   vlib_node_runtime_t * node,
@@ -809,6 +846,9 @@ vnet_interface_output_node_inline (vlib_main_t * vm,
 				   vnet_hw_interface_t * hi,
 				   int do_tx_offloads)
 {
+  vnet_interface_pcap_tx_trace (vm, node, frame,
+				0 /* sw_if_index_from_buffer */ );
+
   /*
    * The 3-headed "if" is here because we want to err on the side
    * of not impacting the non-GSO performance - so for the more
@@ -838,6 +878,9 @@ vnet_interface_output_node (vlib_main_t * vm, vlib_node_runtime_t * node,
   vnet_interface_output_runtime_t *rt = (void *) node->runtime_data;
   hi = vnet_get_sup_hw_interface (vnm, rt->sw_if_index);
 
+  vnet_interface_pcap_tx_trace (vm, node, frame,
+				0 /* sw_if_index_from_buffer */ );
+
   if (hi->flags & VNET_HW_INTERFACE_FLAG_SUPPORTS_TX_L4_CKSUM_OFFLOAD)
     return vnet_interface_output_node_inline (vm, node, frame, vnm, hi,
 					      /* do_tx_offloads */ 0);
@@ -856,6 +899,9 @@ vnet_per_buffer_interface_output (vlib_main_t * vm,
   u32 n_left_to_next, *from, *to_next;
   u32 n_left_from, next_index;
 
+  vnet_interface_pcap_tx_trace (vm, node, frame,
+				1 /* sw_if_index_from_buffer */ );
+
   n_left_from = frame->n_vectors;
 
   from = vlib_frame_vector_args (frame);