Make the capture file's interface description filterable

This patch introduces the frame.interface_description field.

While testing this new functionality it became obvious that we have
a non-optimal interaction between the existing cfile.c's
cap_file_get_interface_name(), the recently added frame.interface_name
field and this new frame.interface_description field.

The string returned from cap_file_get_interface_name() may in fact
come from one of three different sources: the idb's interface name
(if it exists) or the idb's interface description (if that exists)
or a default text of "unknown".  The string ultimately becomes the
rame.interface_name whether or not the idb had an interface name
option to begin with.  This behavior does not allow one to test for
the simple presence of frame.interface_name.  The new peer function
cap_file_get_interface_description() added by this patch returns
NULL instead of "unknown" if the idb does not have an interface
description.  Should cap_file_get_interface_name() be similarly
modified to return NULL if the idb does not have an interface name?

Bug: 9781
Change-Id: Ie479f373c5080c004dd22bd88919838feca71e95
Reviewed-on: https://code.wireshark.org/review/19861
Petri-Dish: Stig Bjørlykke <stig@bjorlykke.org>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Petri-Dish: Alexis La Goutte <alexis.lagoutte@gmail.com>
Reviewed-by: Alexis La Goutte <alexis.lagoutte@gmail.com>
Reviewed-by: Anders Broman <a.broman58@gmail.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/cfile.c b/cfile.c
index ef0f31a8d8..cf30f3b899 100644
--- a/cfile.c
+++ b/cfile.c
@@ -54,6 +54,28 @@ cap_file_get_interface_name(void *data, guint32 interface_id)
   return "unknown";
 }
 
+const char *
+cap_file_get_interface_description(void *data, guint32 interface_id)
+{
+  capture_file *cf = (capture_file *) data;
+  wtapng_iface_descriptions_t *idb_info;
+  wtap_block_t wtapng_if_descr = NULL;
+  char* interface_name;
+
+  idb_info = wtap_file_get_idb_info(cf->wth);
+
+  if (interface_id < idb_info->interface_data->len)
+    wtapng_if_descr = g_array_index(idb_info->interface_data, wtap_block_t, interface_id);
+
+  g_free(idb_info);
+
+  if (wtapng_if_descr) {
+    if (wtap_block_get_string_option_value(wtapng_if_descr, OPT_IDB_DESCR, &interface_name) == WTAP_OPTTYPE_SUCCESS)
+      return interface_name;
+  }
+  return NULL;
+}
+
 void
 cap_file_init(capture_file *cf)
 {