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, 10 insertions, 2 deletions

diff --git a/packet-sdp.c b/packet-sdp.c
index 0dfc80b311..1c0a639547 100644
--- a/packet-sdp.c
+++ b/packet-sdp.c
@@ -4,7 +4,7 @@
  * Jason Lango <jal@netapp.com>
  * Liberally copied from packet-http.c, by Guy Harris <guy@alum.mit.edu>
  *
- * $Id: packet-sdp.c,v 1.15 2000/11/13 08:58:12 guy Exp $
+ * $Id: packet-sdp.c,v 1.16 2000/11/15 07:07:44 guy Exp $
  *
  * Ethereal - Network traffic analyzer
  * By Gerald Combs <gerald@zing.org>
@@ -45,7 +45,7 @@ static int proto_sdp = -1;
 
 static int ett_sdp = -1;
 
-void
+static void
 dissect_sdp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 {
 	proto_tree	*sdp_tree;
@@ -218,4 +218,12 @@ proto_register_sdp(void)
         proto_sdp = proto_register_protocol("Session Description Protocol", "sdp");
  /*       proto_register_field_array(proto_sdp, hf, array_length(hf));*/
 	proto_register_subtree_array(ett, array_length(ett));
+
+	/*
+	 * Register the dissector by name, so other dissectors can
+	 * grab it by name rather than just referring to it directly
+	 * (you can't refer to it directly from a plugin dissector
+	 * on Windows without stuffing it into the Big Transfer Vector).
+	 */
+	register_dissector("sdp", dissect_sdp);
 }