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, 75 insertions, 20 deletions

diff --git a/tshark.c b/tshark.c
index d8e70622a6..dee68f3c96 100644
--- a/tshark.c
+++ b/tshark.c
@@ -2561,11 +2561,29 @@ capture_input_new_packets(capture_session *cap_session, int to_read)
     gboolean create_proto_tree;
     epan_dissect_t *edt;
 
-    if (cf->rfcode || cf->dfcode || print_details || filtering_tap_listeners ||
-        (tap_flags & TL_REQUIRES_PROTO_TREE) || have_custom_cols(&cf->cinfo))
-      create_proto_tree = TRUE;
-    else
-      create_proto_tree = FALSE;
+    /*
+     * Determine whether we need to create a protocol tree.
+     * We do if:
+     *
+     *    we're going to apply a read filter;
+     *
+     *    we're going to apply a display filter;
+     *
+     *    we're going to print the protocol tree;
+     *
+     *    one of the tap listeners is going to apply a filter;
+     *
+     *    one of the tap listeners requires a protocol tree;
+     *
+     *    a postdissector wants field values on the first pass;
+     *
+     *    we have custom columns (which require field values, which
+     *    currently requires that we build a protocol tree).
+     */
+    create_proto_tree =
+      (cf->rfcode || cf->dfcode || print_details || filtering_tap_listeners ||
+        (tap_flags & TL_REQUIRES_PROTO_TREE) || postdissectors_want_fields() ||
+        have_custom_cols(&cf->cinfo));
 
     /* The protocol tree will be "visible", i.e., printed, only if we're
        printing packet details, which is true if we're printing stuff
@@ -3078,12 +3096,20 @@ load_cap_file(capture_file *cf, char *save_file, int out_file_type,
     cf->frames = new_frame_data_sequence();
 
     if (do_dissection) {
-       gboolean create_proto_tree = FALSE;
+      gboolean create_proto_tree;
 
-      /* If we're going to be applying a filter, we'll need to
-         create a protocol tree against which to apply the filter. */
-      if (cf->rfcode || cf->dfcode)
-        create_proto_tree = TRUE;
+      /*
+       * Determine whether we need to create a protocol tree.
+       * We do if:
+       *
+       *    we're going to apply a read filter;
+       *
+       *    we're going to apply a display filter;
+       *
+       *    a postdissector wants field values on the first pass.
+       */
+      create_proto_tree =
+        (cf->rfcode != NULL || cf->dfcode != NULL || postdissectors_want_fields());
 
       tshark_debug("tshark: create_proto_tree = %s", create_proto_tree ? "TRUE" : "FALSE");
 
@@ -3131,11 +3157,22 @@ load_cap_file(capture_file *cf, char *save_file, int out_file_type,
     if (do_dissection) {
       gboolean create_proto_tree;
 
-      if (cf->dfcode || print_details || filtering_tap_listeners ||
-         (tap_flags & TL_REQUIRES_PROTO_TREE) || have_custom_cols(&cf->cinfo))
-           create_proto_tree = TRUE;
-      else
-           create_proto_tree = FALSE;
+      /*
+       * Determine whether we need to create a protocol tree.
+       * We do if:
+       *
+       *    we're going to apply a display filter;
+       *
+       *    we're going to print the protocol tree;
+       *
+       *    one of the tap listeners requires a protocol tree;
+       *
+       *    we have custom columns (which require field values, which
+       *    currently requires that we build a protocol tree).
+       */
+      create_proto_tree =
+        (cf->dfcode || print_details || filtering_tap_listeners ||
+         (tap_flags & TL_REQUIRES_PROTO_TREE) || have_custom_cols(&cf->cinfo));
 
       tshark_debug("tshark: create_proto_tree = %s", create_proto_tree ? "TRUE" : "FALSE");
 
@@ -3257,11 +3294,29 @@ load_cap_file(capture_file *cf, char *save_file, int out_file_type,
     if (do_dissection) {
       gboolean create_proto_tree;
 
-      if (cf->rfcode || cf->dfcode || print_details || filtering_tap_listeners ||
-          (tap_flags & TL_REQUIRES_PROTO_TREE) || have_custom_cols(&cf->cinfo))
-        create_proto_tree = TRUE;
-      else
-        create_proto_tree = FALSE;
+      /*
+       * Determine whether we need to create a protocol tree.
+       * We do if:
+       *
+       *    we're going to apply a read filter;
+       *
+       *    we're going to apply a display filter;
+       *
+       *    we're going to print the protocol tree;
+       *
+       *    one of the tap listeners is going to apply a filter;
+       *
+       *    one of the tap listeners requires a protocol tree;
+       *
+       *    a postdissector wants field values on the first pass;
+       *
+       *    we have custom columns (which require field values, which
+       *    currently requires that we build a protocol tree).
+       */
+      create_proto_tree =
+        (cf->rfcode || cf->dfcode || print_details || filtering_tap_listeners ||
+          (tap_flags & TL_REQUIRES_PROTO_TREE) || postdissectors_want_fields() ||
+          have_custom_cols(&cf->cinfo))
 
       tshark_debug("tshark: create_proto_tree = %s", create_proto_tree ? "TRUE" : "FALSE");