fix pcap_write function

when use pcap cli to capture pcakets into two files rx01.pcap && rx02.pcap,
the first time:
1)pcap rx trace on max 100 intfc any file rx01.pcap
2)......the process of capture data to buffer......
3)pcap rx trace off

the second time:
4)pcap rx trace on max 100 intfc any file rx02.pcap
5)......the process of capture data to buffer......
6)pcap rx trace off

the pcap_write function bug in this two lines
pm->n_packets_captured = 0;
if (pm->n_packets_captured >= pm->n_packets_to_capture) referring to calling pcap_close()
will result in that the twice pcap cli both writes the packets
into rx01.pcap, but nothing into rx02.pcap. Beside, the rx02.pcap
file will not be created.

solution: separate the pcap_close() out of pcap_write()

Change-Id: Iedeb46f9cf0a4cb12449fd75a4014f95f3bb3fa8
Signed-off-by: Jack Xu <jack.c.xu@ericsson.com>

src/vlib/main.c

@@ -2204,6 +2204,8 @@ pcap_dispatch_trace_command_internal (vlib_main_t * vm,
 		{
 		  pm->n_packets_to_capture = pm->n_packets_captured;
 		  error = pcap_write (pm);
+		  if (pm->file_descriptor >= 0)
+		    pcap_close (pm);
 		  if (error)
 		    clib_error_report (error);
 		  else

src/vnet/interface_cli.c

@@ -1743,6 +1743,8 @@ pcap_trace_command_internal (vlib_main_t * vm,
 		  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 (vm->pcap[rx_tx].pcap_main.file_descriptor >= 0)
+		    pcap_close (&vm->pcap[rx_tx].pcap_main);
 		  if (error)
 		    clib_error_report (error);
 		  else

src/vnet/interface_output.c

@@ -1439,6 +1439,8 @@ pcap_drop_trace_command_fn (vlib_main_t * vm,
 		  im->pcap_main.n_packets_to_capture =
 		    im->pcap_main.n_packets_captured;
 		  error = pcap_write (&im->pcap_main);
+		  if (im->pcap_main.file_descriptor >= 0)
+		    pcap_close (&im->pcap_main);
 		  if (error)
 		    clib_error_report (error);
 		  else

src/vnet/pg/output.c

@@ -79,7 +79,10 @@ pg_output (vlib_main_t * vm, vlib_node_runtime_t * node, vlib_frame_t * frame)
     }
   if (pif->pcap_file_name != 0)
     pcap_write (&pif->pcap_main);
-
+  if (pif->pcap_main.file_descriptor >= 0
+      && pif->pcap_main.n_packets_captured >=
+      pif->pcap_main.n_packets_to_capture)
+    pcap_close (&pif->pcap_main);
 
   vlib_buffer_free (vm, vlib_frame_vector_args (frame), n_buffers);
   if (PREDICT_FALSE (pif->lockp != 0))

src/vppinfra/pcap.c

@@ -157,9 +157,6 @@ pcap_write (pcap_main_t * pm)
       pm->n_pcap_data_written = 0;
     }
 
-  if (pm->n_packets_captured >= pm->n_packets_to_capture)
-    pcap_close (pm);
-
 done:
   if (error)
     {

src/vppinfra/pcap_funcs.h

@@ -22,6 +22,9 @@ clib_error_t *pcap_write (pcap_main_t * pm);
 /** Read data from file. */
 clib_error_t *pcap_read (pcap_main_t * pm);
 
+/** Close the file created by pcap_write function. */
+clib_error_t *pcap_close (pcap_main_t * pm);
+
 /**
  * @brief Add packet
  *