dfilter: Add layer support for references

This adds support for using the layers filter
with field references.

Before:
    $ dftest 'ip.src != ${ip.src#2}'
    dftest: invalid character in macro name

After:
    $ dftest 'ip.src != ${ip.src#2}'
    Filter: ip.src != ${ip.src#2}

    Syntax tree:
     0 TEST_ALL_NE:
       1 FIELD(ip.src <FT_IPv4>)
       1 REFERENCE(ip.src#[2:1] <FT_IPv4>)

    Instructions:
    00000 READ_TREE		ip.src <FT_IPv4> -> reg#0
    00001 IF_FALSE_GOTO	5
    00002 READ_REFERENCE_R	${ip.src <FT_IPv4>} #[2:1] -> reg#1
    00003 IF_FALSE_GOTO	5
    00004 ALL_NE		reg#0 != reg#1
    00005 RETURN

This requires adding another level of complexity to references.
When loading references we need to copy the 'proto_layer_num'
and add the logic to filter on that.

The "layer" sttype is removed and replace by a new
field sttype with support for a range. This is a nice
cleanup for the semantic check and general simplification.
The grammar is better too with this design.

Range sttype is renamed to slice for clarity.

1 files changed, 13 insertions, 1 deletions

diff --git a/epan/dfilter/dfilter-int.h b/epan/dfilter/dfilter-int.h
index 5bdd6056fc..2082a6d992 100644
--- a/epan/dfilter/dfilter-int.h
+++ b/epan/dfilter/dfilter-int.h
@@ -16,6 +16,12 @@
 #include <epan/proto.h>
 #include <stdio.h>
 
+typedef struct {
+	const header_field_info *hfinfo;
+	fvalue_t *value;
+	int proto_layer_num;
+} df_reference_t;
+
 /* Passed back to user */
 struct epan_dfilter {
 	GPtrArray	*insns;
@@ -44,7 +50,7 @@ typedef struct {
 	int		next_insn_id;
 	int		next_register;
 	GPtrArray	*deprecated;
-	GHashTable	*references; /* hfinfo -> pointer to GSList of fvalues */
+	GHashTable	*references; /* hfinfo -> pointer to array of references */
 	GHashTable	*loaded_references;
 	char		*expanded_text;
 	stloc_t		err_loc;
@@ -119,4 +125,10 @@ dfilter_fvalue_from_charconst(dfwork_t *dfw, ftenum_t ftype, stnode_t *st);
 
 const char *tokenstr(int token);
 
+df_reference_t *
+reference_new(const field_info *finfo);
+
+void
+reference_free(df_reference_t *ref);
+
 #endif