Add an API to let a postdissector specify fields whose values it needs.

Currently, this is only used to determine whether a protocol tree needs
to be built on the first pass or not - if there are postdissectors that
need fields, it does - but eventually we should be able to use it to
prime the dissection to deliver those fields in cases where we don't
need the *entire* protocol tree (rather than using a hack such as
cooking up a fake tap with a fake filter to do that).

Update MATE and TRANSUM to use it.

Clean up code to check whether we need a protocol tree, and add comments
before that code indicating, in each case, what the criteria are.

The array of postdissectors includes a length, so we don't need to
separately keep track of the number of postdissectors.

Clean up indentation while we're at it.

Change-Id: I71d4025848206d144bc54cc82941089a50e80ab7
Reviewed-on: https://code.wireshark.org/review/21029
Reviewed-by: Guy Harris <guy@alum.mit.edu>

1 files changed, 68 insertions, 16 deletions

diff --git a/epan/packet.c b/epan/packet.c
index de0a84854a..4a3b5cbd64 100644
--- a/epan/packet.c
+++ b/epan/packet.c
@@ -127,8 +127,24 @@ static GHashTable *depend_dissector_lists = NULL;
  * the final cleanup. */
 static GSList *postseq_cleanup_routines;
 
-static GPtrArray* post_dissectors = NULL;
-static guint num_of_postdissectors = 0;
+/*
+ * Post-dissector information - handle for the dissector and a list
+ * of hfids for the fields the post-dissector wants.
+ */
+typedef struct {
+	dissector_handle_t handle;
+	GArray *wanted_fields;
+} postdissector;
+
+/*
+ * Array of all postdissectors.
+ */
+static GArray *postdissectors = NULL;
+
+/*
+ * i-th element of that array.
+ */
+#define POSTDISSECTORS(i)	g_array_index(postdissectors, postdissector, i)
 
 static void
 destroy_depend_dissector_list(void *data)
@@ -248,8 +264,8 @@ packet_cleanup(void)
 	g_hash_table_destroy(heuristic_short_names);
 	g_slist_foreach(shutdown_routines, &call_routine, NULL);
 	g_slist_free(shutdown_routines);
-	if (post_dissectors)
-		g_ptr_array_free(post_dissectors, TRUE);
+	if (postdissectors)
+		g_array_free(postdissectors, TRUE);
 }
 
 /*
@@ -3252,20 +3268,43 @@ dissector_dump_dissector_tables(void)
 void
 register_postdissector(dissector_handle_t handle)
 {
-	if (!post_dissectors)
-		post_dissectors = g_ptr_array_new();
+	postdissector p;
 
-	g_ptr_array_add(post_dissectors, handle);
-	num_of_postdissectors++;
+	if (!postdissectors)
+		postdissectors = g_array_sized_new(FALSE, FALSE, (guint)sizeof(postdissector), 1);
+
+	p.handle = handle;
+	p.wanted_fields = NULL;
+	postdissectors = g_array_append_val(postdissectors, p);
+}
+
+void
+set_postdissector_wanted_fields(dissector_handle_t handle, GArray *wanted_fields)
+{
+    guint i;
+
+    if (!postdissectors) return;
+
+    for (i = 0; i < postdissectors->len; i++) {
+        if (POSTDISSECTORS(i).handle == handle) {
+            POSTDISSECTORS(i).wanted_fields = wanted_fields;
+            break;
+        }
+    }
 }
 
 void
 deregister_postdissector(dissector_handle_t handle)
 {
-    if (!post_dissectors) return;
+    guint i;
+
+    if (!postdissectors) return;
 
-    if (g_ptr_array_remove(post_dissectors, handle)) {
-        num_of_postdissectors--;
+    for (i = 0; i < postdissectors->len; i++) {
+        if (POSTDISSECTORS(i).handle == handle) {
+            postdissectors = g_array_remove_index_fast(postdissectors, i);
+            break;
+        }
     }
 }
 
@@ -3275,8 +3314,8 @@ have_postdissector(void)
 	guint i;
 	dissector_handle_t handle;
 
-	for(i = 0; i < num_of_postdissectors; i++) {
-		handle = (dissector_handle_t) g_ptr_array_index(post_dissectors,i);
+	for (i = 0; i < postdissectors->len; i++) {
+		handle = POSTDISSECTORS(i).handle;
 
 		if (handle->protocol != NULL
 		    && proto_is_protocol_enabled(handle->protocol)) {
@@ -3292,12 +3331,25 @@ call_all_postdissectors(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 {
 	guint i;
 
-	for(i = 0; i < num_of_postdissectors; i++) {
-		call_dissector_only((dissector_handle_t) g_ptr_array_index(post_dissectors,i),
-				    tvb,pinfo,tree, NULL);
+	for (i = 0; i < postdissectors->len; i++) {
+		call_dissector_only(POSTDISSECTORS(i).handle,
+				    tvb, pinfo, tree, NULL);
 	}
 }
 
+gboolean
+postdissectors_want_fields(void)
+{
+	guint i;
+
+	for (i = 0; i < postdissectors->len; i++) {
+		if (POSTDISSECTORS(i).wanted_fields != NULL &&
+		    POSTDISSECTORS(i).wanted_fields->len != 0)
+			return TRUE;
+	}
+	return FALSE;
+}
+
 /*
  * Editor modelines  -  http://www.wireshark.org/tools/modelines.html
  *