UAT: Allow missing fields.

Add uat_set_default_values, which lets us provide default values for
fields that might be missing from the end of a UAT line. Set a default
value for the I/O Graph dialog's Y Axis Factor. Fixes the backward
compatibility issue described in #17623

debian/libwireshark0.symbols

@@ -1937,6 +1937,7 @@ libwireshark.so.0 libwireshark0 #MINVER#
  uat_new@Base 1.9.1
  uat_remove_record_idx@Base 1.9.1
  uat_save@Base 1.9.1
+ uat_set_default_values@Base 3.6.0
  uat_swap@Base 1.9.1
  uat_update_record@Base 1.99.3
  udp_dissect_pdus@Base 1.99.3

epan/uat-int.h

@@ -52,6 +52,7 @@ struct epan_uat {
     uat_reset_cb_t reset_cb;
 
     uat_field_t* fields;
+    const char** default_values;
     guint ncols;
     GArray* user_data;  /**< An array of valid records that will be exposed to the dissector. */
     GArray* raw_data;   /**< An array of records containing possibly invalid data. For internal use only. */

epan/uat.c

@@ -85,6 +85,7 @@ uat_t* uat_new(const char* name,
     uat->post_update_cb = post_update_cb;
     uat->reset_cb = reset_cb;
     uat->fields = flds_array;
+    uat->default_values = NULL;
     uat->user_data = g_array_new(FALSE,FALSE,(guint)uat->record_size);
     uat->raw_data = g_array_new(FALSE,FALSE,(guint)uat->record_size);
     uat->valid_data = g_array_new(FALSE,FALSE,sizeof(gboolean));
@@ -265,6 +266,11 @@ uat_t* uat_get_table_by_name(const char* name) {
     return NULL;
 }
 
+void uat_set_default_values(uat_t *uat_in, const char *default_values[])
+{
+    uat_in->default_values = default_values;
+}
+
 char *uat_fld_tostr(void *rec, uat_field_t *f) {
     guint        len;
     char       *ptr;

epan/uat.h

@@ -258,7 +258,7 @@ typedef struct _uat_field_t {
 #define UAT_AFFECTS_DISSECTION	0x00000001	/* affects packet dissection */
 #define UAT_AFFECTS_FIELDS	0x00000002	/* affects what named fields exist */
 
-/** Create a new uat
+/** Create a new UAT.
  *
  * @param name The name of the table
  * @param size The size of the structure
@@ -293,12 +293,12 @@ uat_t* uat_new(const char* name,
 			   uat_reset_cb_t reset_cb,
 			   uat_field_t* flds_array);
 
-/** Cleanup all Uats
+/** Cleanup all UATs.
  *
  */
 void uat_cleanup(void);
 
-/** Populate a uat using its file.
+/** Populate a UAT using its file.
  *
  * @param uat_in Pointer to a uat. Must not be NULL.
  * @param filename Filename to load, NULL to fetch from current profile.
@@ -309,7 +309,7 @@ void uat_cleanup(void);
 WS_DLL_PUBLIC
 gboolean uat_load(uat_t* uat_in, const gchar *filename, char** err);
 
-/** Create or update a single uat entry using a string.
+/** Create or update a single UAT entry using a string.
  *
  * @param uat_in Pointer to a uat. Must not be NULL.
  * @param entry The string representation of the entry. Format must match
@@ -320,7 +320,7 @@ gboolean uat_load(uat_t* uat_in, const gchar *filename, char** err);
  */
 gboolean uat_load_str(uat_t* uat_in, char* entry, char** err);
 
-/** Given a uat name or filename, find its pointer.
+/** Given a UAT name or filename, find its pointer.
  *
  * @param name The name or filename of the uat
  *
@@ -331,6 +331,22 @@ uat_t *uat_find(gchar *name);
 WS_DLL_PUBLIC
 uat_t* uat_get_table_by_name(const char* name);
 
+/**
+ * Provide default field values for a UAT.
+ *
+ * This can be used to provide forward compatibility when fields are added
+ * to a UAT.
+ *
+ * @param uat_in Pointer to a uat. Must not be NULL.
+ * @param default_values An array of strings with default values. Must
+ * be the same length as flds_array. Individual elements can be NULL,
+ * and can be used to distinguish between mandatory and optional fields,
+ * e.g. { NULL, NULL, NULL, "default value (optional)" }
+ * @todo Use this to provide default values for empty tables.
+ */
+WS_DLL_PUBLIC
+void uat_set_default_values(uat_t *uat_in, const char *default_values[]);
+
 /*
  * Some common uat_fld_chk_cbs
  */

epan/uat_load.l

@@ -246,7 +246,7 @@ comment #[^\n]*\n
 	BEGIN NEXT_FIELD;
 }
 
-<START_OF_LINE,NEXT_FIELD>{newline}   {
+<START_OF_LINE,NEXT_FIELD>{newline} {
 	yyextra->ptrx = g_strdup("");
 	yyextra->len = 0;
 
@@ -298,8 +298,34 @@ comment #[^\n]*\n
 }
 
 <SEPARATOR>{newline} {
+	DUMP("separator->newline");
+
+	/*
+	 * We've run out of fields. Check to see if we have any default
+	 * values that we can fill in. The field for the current column
+	 * will be filled in below in <END_OF_RECORD>{newline}.
+	 */
+	guint save_colnum = yyextra->colnum;
+	yyextra->colnum++;
+	while (yyextra->colnum < yyextra->uat->ncols) {
+		const char *default_value = yyextra->uat->default_values[yyextra->colnum];
+		if (!default_value) {
+			break;
+		}
+		yyextra->uat->fields[yyextra->colnum].cb.set(yyextra->record, default_value, (guint) strlen(default_value), yyextra->uat->fields[yyextra->colnum].cbdata.chk, yyextra->uat->fields[yyextra->colnum].fld_data);
+		ws_log(WS_LOG_DOMAIN, LOG_LEVEL_INFO, "%s:%d: Set %s to %s.",
+			yyextra->uat->filename, yyextra->linenum, yyextra->uat->fields[yyextra->colnum].name, default_value);
+		yyextra->colnum++;
+	}
+
+	if (yyextra->colnum < yyextra->uat->ncols) {
+		ERROR(("expecting field %s", yyextra->uat->fields[yyextra->colnum].name));
+	}
+
+	yyextra->colnum = save_colnum;
 	yyextra->linenum++;
-	ERROR(("expecting field %s in previous line",yyextra->uat->fields[yyextra->colnum].name));
+	BEGIN END_OF_RECORD;
+	yyless(0);
 }
 
 <SEPARATOR>. {
@@ -348,7 +374,7 @@ comment #[^\n]*\n
  }
 
 <END_OF_RECORD>. {
-	ERROR(("unexpected char while looking for end of line"));
+	ERROR(("unexpected char %s while looking for end of line", yytext));
 }
 
 <ERRORED>{newline} { yyextra->linenum++; BEGIN START_OF_LINE; }

ui/qt/io_graph_dialog.cpp

@@ -130,6 +130,11 @@ static io_graph_settings_t *iog_settings_ = NULL;
 static guint num_io_graphs_ = 0;
 static uat_t *iog_uat_ = NULL;
 
+// y_axis_factor was added in 3.6. Provide backward compatibility.
+static const char *iog_uat_defaults_[] = {
+    NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, "1"
+};
+
 extern "C" {
 
 //Allow the enable/disable field to be a checkbox, but for backwards compatibility,
@@ -1202,6 +1207,8 @@ void IOGraphDialog::loadProfileGraphs()
                            NULL,
                            io_graph_fields);
 
+        uat_set_default_values(iog_uat_, iog_uat_defaults_);
+
         char* err = NULL;
         if (!uat_load(iog_uat_, NULL, &err)) {
             report_failure("Error while loading %s: %s.  Default graph values will be used", iog_uat_->name, err);