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>

4 files changed, 29 insertions, 6 deletions

diff --git a/epan/dissectors/packet-frame.c b/epan/dissectors/packet-frame.c
index d5c793404f..b4f17367b4 100644
--- a/epan/dissectors/packet-frame.c
+++ b/epan/dissectors/packet-frame.c
@@ -75,6 +75,7 @@ static int hf_frame_color_filter_name = -1;
 static int hf_frame_color_filter_text = -1;
 static int hf_frame_interface_id = -1;
 static int hf_frame_interface_name = -1;
+static int hf_frame_interface_description = -1;
 static int hf_frame_pack_flags = -1;
 static int hf_frame_pack_direction = -1;
 static int hf_frame_pack_reception_type = -1;
@@ -342,21 +343,26 @@ dissect_frame(tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent_tree, void*
 		fh_tree = proto_item_add_subtree(ti, ett_frame);
 
 		if (pinfo->phdr->presence_flags & WTAP_HAS_INTERFACE_ID &&
-		   (proto_field_is_referenced(tree, hf_frame_interface_id) ||
-		    proto_field_is_referenced(tree, hf_frame_interface_name))) {
+		   (proto_field_is_referenced(tree, hf_frame_interface_id) || proto_field_is_referenced(tree, hf_frame_interface_name) || proto_field_is_referenced(tree, hf_frame_interface_description))) {
 			const char *interface_name = epan_get_interface_name(pinfo->epan, pinfo->phdr->interface_id);
+			const char *interface_description = epan_get_interface_description(pinfo->epan, pinfo->phdr->interface_id);
+			proto_tree *if_tree;
+			proto_item *if_item;
 
 			if (interface_name) {
-				proto_tree *if_tree;
-				proto_item *if_item;
 				if_item = proto_tree_add_uint_format_value(fh_tree, hf_frame_interface_id, tvb, 0, 0,
 									   pinfo->phdr->interface_id, "%u (%s)",
 									   pinfo->phdr->interface_id, interface_name);
 				if_tree = proto_item_add_subtree(if_item, ett_ifname);
 				proto_tree_add_string(if_tree, hf_frame_interface_name, tvb, 0, 0, interface_name);
 			} else {
-				proto_tree_add_uint(fh_tree, hf_frame_interface_id, tvb, 0, 0, pinfo->phdr->interface_id);
+				if_item = proto_tree_add_uint(fh_tree, hf_frame_interface_id, tvb, 0, 0, pinfo->phdr->interface_id);
 			}
+
+                        if (interface_description) {
+				if_tree = proto_item_add_subtree(if_item, ett_ifname);
+				proto_tree_add_string(if_tree, hf_frame_interface_description, tvb, 0, 0, interface_description);
+                        }
 		}
 
 		if (pinfo->phdr->presence_flags & WTAP_HAS_PACK_FLAGS) {
@@ -816,6 +822,11 @@ proto_register_frame(void)
 		    FT_STRING, BASE_NONE, NULL, 0x0,
 		    "The friendly name for this interface", HFILL }},
 
+		{ &hf_frame_interface_description,
+		  { "Interface description", "frame.interface_description",
+		    FT_STRING, BASE_NONE, NULL, 0x0,
+		    "The descriptionfor this interface", HFILL }},
+
 		{ &hf_frame_pack_flags,
 		  { "Packet flags", "frame.packet_flags",
 		    FT_UINT32, BASE_HEX, NULL, 0x0,
diff --git a/epan/epan-int.h b/epan/epan-int.h
index 35e91975be..15b059f388 100644
--- a/epan/epan-int.h
+++ b/epan/epan-int.h
@@ -30,6 +30,7 @@ struct epan_session {
 
 	const nstime_t *(*get_frame_ts)(void *data, guint32 frame_num);
 	const char *(*get_interface_name)(void *data, guint32 interface_id);
+	const char *(*get_interface_description)(void *data, guint32 interface_id);
 	const char *(*get_user_comment)(void *data, const frame_data *fd);
 };
 
diff --git a/epan/epan.c b/epan/epan.c
index 54d5292fe8..e0ebd5b215 100644
--- a/epan/epan.c
+++ b/epan/epan.c
@@ -271,6 +271,15 @@ epan_get_interface_name(const epan_t *session, guint32 interface_id)
 	return NULL;
 }
 
+const char *
+epan_get_interface_description(const epan_t *session, guint32 interface_id)
+{
+	if (session->get_interface_description)
+		return session->get_interface_description(session->data, interface_id);
+
+	return NULL;
+}
+
 const nstime_t *
 epan_get_frame_ts(const epan_t *session, guint32 frame_num)
 {
diff --git a/epan/epan.h b/epan/epan.h
index e1dacdc390..3a1e742d14 100644
--- a/epan/epan.h
+++ b/epan/epan.h
@@ -131,7 +131,7 @@ void epan_circuit_cleanup(void);
 /** A client will create one epan_t for an entire dissection session.
  * A single epan_t will be used to analyze the entire sequence of packets,
  * sequentially, in a single session. A session corresponds to a single
- * packet trace file. The reaons epan_t exists is that some packets in
+ * packet trace file. The reasons epan_t exists is that some packets in
  * some protocols cannot be decoded without knowledge of previous packets.
  * This inter-packet "state" is stored in the epan_t.
  */
@@ -143,6 +143,8 @@ WS_DLL_PUBLIC const char *epan_get_user_comment(const epan_t *session, const fra
 
 WS_DLL_PUBLIC const char *epan_get_interface_name(const epan_t *session, guint32 interface_id);
 
+WS_DLL_PUBLIC const char *epan_get_interface_description(const epan_t *session, guint32 interface_id);
+
 const nstime_t *epan_get_frame_ts(const epan_t *session, guint32 frame_num);
 
 WS_DLL_PUBLIC void epan_free(epan_t *session);