Add a mechanism by which a dissector can be registered by name, another

dissector can get a "handle" for that dissector by name and then call
that dissector through the handle.

This allows dissectors that can't be called through a port table or a
heuristic table to be called from other dissectors without directly
referring to the dissector function - dynamically-loaded modules, under
Windows, cannot directly call functions in the main program, and
non-plugin dissectors are in the main program and thus cannot be called
from plugin dissectors unless either

	1) a pointer to the dissector is put in the Big Transfer Vector

or

	2) some other mechanism for getting a pointer to the dissector
	   is provided.

This mechanism could also support registering old-style dissectors and
calling them from new-style dissectors without the new-style dissector
having to do the argument translation itself (I didn't add support for
registering old-style dissectors because I'd prefer to have people
tvbuffify their code if they have to register a dissector...).

It could also, in the future, perhaps support

	disabling of protocols;

	setting "pinfo->current_proto";

inside "call_dissector()" - and inside "{old_}dissector_try_port()" and
"{old_"dissector_try_heuristic()" - allowing a pile of stuff that
currently has to be done in every dissector be done by common code.
(I have some ideas about how to do this, by

	having "proto_register_protocol()" take an abbreviation - of the
	sort that would be put in, for example, "pinfo->current_proto" -
	as an argument;

	having the calls to register dissectors take an index returned
	by "proto_register_protocol()" as an argument.

The abbreviation could be used elsewhere as well, e.g. in the "Decoding"
tab of the "Edit->Protocols" dialog box, and in a GUI for constructing
protocol filters.  Watch this space.)

Make "dissect_sdp()" the first client of this mechanism; it's now static
to "packet-sdp.c", and all dissectors that call it - including the MGCP
plugin - now call it through a dissector handle fetched by
"find_dissector()".  (Next step - see if Ethereal can now compile on
Windows as a result of this.)

svn path=/trunk/; revision=2647

1 files changed, 9 insertions, 3 deletions

diff --git a/packet-sap.c b/packet-sap.c
index 521c6a4146..5575bedf38 100644
--- a/packet-sap.c
+++ b/packet-sap.c
@@ -4,7 +4,7 @@
  *
  * Heikki Vatiainen <hessu@cs.tut.fi>
  *
- * $Id: packet-sap.c,v 1.13 2000/11/10 06:50:36 guy Exp $
+ * $Id: packet-sap.c,v 1.14 2000/11/15 07:07:43 guy Exp $
  *
  * Ethereal - Network traffic analyzer
  * By Gerald Combs <gerald@zing.org>
@@ -43,7 +43,6 @@
 #include <glib.h>
 #include "packet.h"
 #include "packet-ipv6.h"
-#include "packet-sdp.h"
 
 #define UDP_PORT_SAP	9875
 
@@ -126,6 +125,8 @@ static gint ett_sap_flags = -1;
 static gint ett_sap_auth = -1;
 static gint ett_sap_authf = -1;
 
+static dissector_handle_t sdp_handle;
+
 static void
 dissect_sap(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 {
@@ -277,7 +278,7 @@ dissect_sap(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
           }
           
           /* Done with SAP */
-          dissect_sdp(tvb, pinfo, tree);
+          call_dissector(sdp_handle, tvb, pinfo, tree);
 	}
 
         return;
@@ -363,4 +364,9 @@ void
 proto_reg_handoff_sap(void)
 {
   dissector_add("udp.port", UDP_PORT_SAP, dissect_sap);
+
+  /*
+   * Get a handle for the SDP dissector.
+   */
+  sdp_handle = find_dissector("sdp");
 }