For ISDN, don't create an endpoint by ID and then use it.

That isn't working, because it depends on the notion that for every
"endpoint type" there's a "port type" for the packet_info structure;
that's not true for ISDN channels.

The whole point of "use the packet_info structure when trying to find a
conversation and create it if it doesn't exist" is to use address
information *already filled in by somebody for use by other dissectors*;
we don't do that with the ISDN channel number, because there's no *need*
to do so.

So just add a new find_or_create_conversation_by_id() routine, which
passes the packet_info structure to get the frame number, and explicitly
passes the endpoint type and ID.  Use that in the ISDN dissector.

Bug: 15018
Change-Id: Id0e997254b0eaf7cbc9261a2adff639ecbf083c0
Reviewed-on: https://code.wireshark.org/review/28904
Reviewed-by: Guy Harris <guy@alum.mit.edu>

4 files changed, 29 insertions, 3 deletions

diff --git a/debian/libwireshark0.symbols b/debian/libwireshark0.symbols
index e7ebc510a9..9392832a4b 100644
--- a/debian/libwireshark0.symbols
+++ b/debian/libwireshark0.symbols
@@ -630,6 +630,7 @@ libwireshark.so.0 libwireshark0 #MINVER#
  find_heur_dissector_by_unique_short_name@Base 1.99.8
  find_heur_dissector_list@Base 1.99.2
  find_or_create_conversation@Base 1.9.1
+ find_or_create_conversation_by_id@Base 2.6.3
  find_protocol_by_id@Base 1.9.1
  find_sid_name@Base 1.9.1
  find_stream_circ@Base 1.9.1
diff --git a/epan/conversation.c b/epan/conversation.c
index b2a8ef8b1b..fc94e3d65b 100644
--- a/epan/conversation.c
+++ b/epan/conversation.c
@@ -1508,6 +1508,26 @@ find_or_create_conversation(packet_info *pinfo)
 	return conv;
 }
 
+conversation_t *
+find_or_create_conversation_by_id(packet_info *pinfo, const endpoint_type etype, const guint32 id)
+{
+	conversation_t *conv=NULL;
+
+	/* Have we seen this conversation before? */
+	if ((conv = find_conversation_by_id(pinfo->num, etype, id, 0)) == NULL) {
+		/* No, this is a new conversation. */
+		DPRINT(("did not find previous conversation for frame #%u",
+				pinfo->num));
+		DINDENT();
+		conv = conversation_new_by_id(pinfo->num, etype, id, 0);
+		DENDENT();
+	}
+
+	DENDENT();
+
+	return conv;
+}
+
 void conversation_create_endpoint(struct _packet_info *pinfo, address* addr1, address* addr2,
     endpoint_type etype, guint32 port1, guint32	port2, const guint options)
 {
diff --git a/epan/conversation.h b/epan/conversation.h
index 0059703868..d345fe19e3 100644
--- a/epan/conversation.h
+++ b/epan/conversation.h
@@ -188,6 +188,12 @@ WS_DLL_PUBLIC conversation_t *find_conversation_pinfo(packet_info *pinfo, const
  */
 WS_DLL_PUBLIC conversation_t *find_or_create_conversation(packet_info *pinfo);
 
+/**  A helper function that calls find_conversation_by_id() and, if a
+ *  conversation is not found, calls conversation_new_by_id().
+ *  The frame number is taken from pinfo.
+ */
+WS_DLL_PUBLIC conversation_t *find_or_create_conversation_by_id(packet_info *pinfo, const endpoint_type etype, const guint32 id);
+
 WS_DLL_PUBLIC void conversation_add_proto_data(conversation_t *conv, const int proto,
     void *proto_data);
 WS_DLL_PUBLIC void *conversation_get_proto_data(const conversation_t *conv, const int proto);
diff --git a/epan/dissectors/packet-isdn.c b/epan/dissectors/packet-isdn.c
index 846996b278..a2171eed83 100644
--- a/epan/dissectors/packet-isdn.c
+++ b/epan/dissectors/packet-isdn.c
@@ -96,8 +96,6 @@ dissect_isdn(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_
 		col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "Network");
 	}
 
-	conversation_create_endpoint_by_id(pinfo, ENDPOINT_ISDN, pinfo->pseudo_header->isdn.channel, 0);
-
 	if (tree) {
 		ti = proto_tree_add_item(tree, proto_isdn, tvb, 0, 0, ENC_NA);
 		isdn_tree = proto_item_add_subtree(ti, ett_isdn);
@@ -109,7 +107,8 @@ dissect_isdn(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_
 	/*
 	 * Set up a circuit for this channel, and assign it a dissector.
 	 */
-	conv = find_or_create_conversation(pinfo);
+	conv = find_or_create_conversation_by_id(pinfo, ENDPOINT_ISDN,
+	    pinfo->pseudo_header->isdn.channel);
 
 	if (conversation_get_dissector(conv, 0) == NULL) {
 		/*