From 0b39b1cbb70c6f37a30a3130e1c308ddd0ba36de Mon Sep 17 00:00:00 2001
From: Maria Matejka <mq@ucw.cz>
Date: Fri, 15 Feb 2019 13:53:17 +0100
Subject: [PATCH] Conf: Symbol implementation converted from void pointers to
 union

... and consted some declarations.
---
 conf/cf-lex.l      | 59 ++++++++++++++++++++--------------------------
 conf/conf.h        | 49 +++++++++++++++++++++++++++++++-------
 conf/confbase.Y    |  5 ++--
 filter/config.Y    | 53 ++++++++++++++++++++++-------------------
 filter/decl.m4     |  4 ++--
 filter/f-inst.c    | 10 ++++----
 filter/f-inst.h    |  5 ++--
 filter/f-util.c    |  4 ++--
 filter/filter.c    |  5 ++--
 filter/filter.h    |  6 ++---
 nest/config.Y      | 24 +++++++++----------
 nest/proto.c       |  6 ++---
 nest/protocol.h    |  6 ++---
 nest/route.h       |  4 ++--
 nest/rt-table.c    | 14 +++++------
 proto/mrt/mrt.h    |  6 ++---
 sysdep/unix/krt.c  |  2 +-
 sysdep/unix/main.c |  8 +++----
 18 files changed, 149 insertions(+), 121 deletions(-)

diff --git a/conf/cf-lex.l b/conf/cf-lex.l
index 6cc09425..f1b402a0 100644
--- a/conf/cf-lex.l
+++ b/conf/cf-lex.l
@@ -539,11 +539,8 @@ cf_new_symbol(byte *c)
   if (l > SYM_MAX_LEN)
     cf_error("Symbol too long");
 
-  s = cfg_alloc(sizeof(struct symbol) + l);
-  s->scope = conf_this_scope;
-  s->class = SYM_VOID;
-  s->def = NULL;
-  s->aux = 0;
+  s = cfg_allocz(sizeof(struct symbol) + l + 1);
+  *s = (struct symbol) { .scope = conf_this_scope, .class = SYM_VOID, };
   strcpy(s->name, c);
 
   if (!new_config->sym_hash.data)
@@ -574,6 +571,7 @@ cf_find_symbol(struct config *cfg, byte *c)
       (s = HASH_FIND(cfg->sym_hash, SYM, c, 1)))
     return s;
 
+  /* In CLI command parsing, fallback points to the current config, otherwise it is NULL. */
   if (cfg->fallback &&
       cfg->fallback->sym_hash.data &&
       (s = HASH_FIND(cfg->fallback->sym_hash, SYM, c, 1)))
@@ -597,6 +595,28 @@ cf_get_symbol(byte *c)
   return cf_find_symbol(new_config, c) ?: cf_new_symbol(c);
 }
 
+/**
+ * cf_localize_symbol - get the local instance of given symbol
+ * @sym: the symbol to localize
+ *
+ * This functions finds the symbol that is local to current scope
+ * for purposes of cf_define_symbol().
+ */
+struct symbol *
+cf_localize_symbol(struct symbol *sym)
+{
+  /* If the symbol type is void, it has been recently allocated just in this scope. */
+  if (!sym->class)
+    return sym;
+  
+  /* If the scope is the current, it is already defined in this scope. */
+  if (sym->scope == conf_this_scope)
+    cf_error("Symbol already defined");
+
+  /* Not allocated here yet, doing it now. */
+  return cf_new_symbol(sym->name);
+}
+
 struct symbol *
 cf_default_name(char *template, int *counter)
 {
@@ -616,35 +636,6 @@ cf_default_name(char *template, int *counter)
   cf_error("Unable to generate default name");
 }
 
-/**
- * cf_define_symbol - define meaning of a symbol
- * @sym: symbol to be defined
- * @type: symbol class to assign
- * @def: class dependent data
- *
- * Defines new meaning of a symbol. If the symbol is an undefined
- * one (%SYM_VOID), it's just re-defined to the new type. If it's defined
- * in different scope, a new symbol in current scope is created and the
- * meaning is assigned to it. If it's already defined in the current scope,
- * an error is reported via cf_error().
- *
- * Result: Pointer to the newly defined symbol. If we are in the top-level
- * scope, it's the same @sym as passed to the function.
- */
-struct symbol *
-cf_define_symbol(struct symbol *sym, int type, void *def)
-{
-  if (sym->class)
-    {
-      if (sym->scope == conf_this_scope)
-	cf_error("Symbol already defined");
-      sym = cf_new_symbol(sym->name);
-    }
-  sym->class = type;
-  sym->def = def;
-  return sym;
-}
-
 static void
 cf_lex_init_kh(void)
 {
diff --git a/conf/conf.h b/conf/conf.h
index 4e3addb3..21d4f1e2 100644
--- a/conf/conf.h
+++ b/conf/conf.h
@@ -105,11 +105,19 @@ extern int (*cf_read_hook)(byte *buf, uint max, int fd);
 struct symbol {
   struct symbol *next;
   struct sym_scope *scope;
-  int class;
-  int aux;
-  uint aux2;
-  void *def;
-  char name[1];
+  int class;				/* SYM_* */
+  uint flags;				/* SYM_FLAG_* */
+
+  union {
+    struct proto_config *proto;		/* For SYM_PROTO and SYM_TEMPLATE */
+    const struct f_line *function;	/* For SYM_FUNCTION */
+    const struct filter *filter;	/* For SYM_FILTER */
+    struct rtable_config *table;	/* For SYM_TABLE */
+    struct f_dynamic_attr *attribute;	/* For SYM_ATTRIBUTE */
+    struct f_val *val;			/* For SYM_CONSTANT or SYM_VARIABLE */
+  };
+
+  char name[0];
 };
 
 struct sym_scope {
@@ -134,8 +142,11 @@ struct sym_scope {
 #define SYM_CONSTANT 0x200	/* 0x200-0x2ff are variable types */
 #define SYM_CONSTANT_RANGE SYM_CONSTANT ... (SYM_CONSTANT | 0xff)
 
-#define SYM_TYPE(s) (((struct f_val *) (s)->def)->type)
-#define SYM_VAL(s) (((struct f_val *) (s)->def)->val)
+#define SYM_TYPE(s) ((s)->val->type)
+#define SYM_VAL(s) ((s)->val->val)
+
+/* Symbol flags */
+#define SYM_FLAG_SAME 0x1	/* For SYM_FUNCTION and SYM_FILTER */
 
 struct include_file_stack {
   void *buffer;				/* Internal lexer state */
@@ -160,7 +171,29 @@ struct symbol *cf_find_symbol(struct config *cfg, byte *c);
 
 struct symbol *cf_get_symbol(byte *c);
 struct symbol *cf_default_name(char *template, int *counter);
-struct symbol *cf_define_symbol(struct symbol *symbol, int type, void *def);
+struct symbol *cf_localize_symbol(struct symbol *sym);
+
+/**
+ * cf_define_symbol - define meaning of a symbol
+ * @sym: symbol to be defined
+ * @type: symbol class to assign
+ * @def: class dependent data
+ *
+ * Defines new meaning of a symbol. If the symbol is an undefined
+ * one (%SYM_VOID), it's just re-defined to the new type. If it's defined
+ * in different scope, a new symbol in current scope is created and the
+ * meaning is assigned to it. If it's already defined in the current scope,
+ * an error is reported via cf_error().
+ *
+ * Result: Pointer to the newly defined symbol. If we are in the top-level
+ * scope, it's the same @sym as passed to the function.
+ */
+#define cf_define_symbol(sym_, type_, var_, def_) ({ \
+    struct symbol *sym = cf_localize_symbol(sym_); \
+    sym->class = type_; \
+    sym->var_ = def_; \
+    sym; })
+
 void cf_push_scope(struct symbol *);
 void cf_pop_scope(void);
 char *cf_symbol_class_name(struct symbol *sym);
diff --git a/conf/confbase.Y b/conf/confbase.Y
index 2195e8fc..62415b4c 100644
--- a/conf/confbase.Y
+++ b/conf/confbase.Y
@@ -56,7 +56,8 @@ CF_DECLS
   struct f_dynamic_attr fda;
   struct f_static_attr fsa;
   struct f_lval flv;
-  struct filter *f;
+  const struct f_line *fl;
+  const struct filter *f;
   struct f_tree *e;
   struct f_trie *trie;
   struct f_val v;
@@ -130,7 +131,7 @@ definition:
    DEFINE CF_SYM_VOID '=' term ';' {
      struct f_val *val = cfg_alloc(sizeof(struct f_val));
      if (f_eval(f_postfixify($4), cfg_mem, val) > F_RETURN) cf_error("Runtime error");
-     cf_define_symbol($2, SYM_CONSTANT | val->type, val);
+     cf_define_symbol($2, SYM_CONSTANT | val->type, val, val);
    }
  ;
 
diff --git a/filter/config.Y b/filter/config.Y
index 488b9ced..b3a04958 100644
--- a/filter/config.Y
+++ b/filter/config.Y
@@ -451,7 +451,8 @@ CF_KEYWORDS(FUNCTION, PRINT, PRINTN, UNSET, RETURN,
 %type <x> term block cmd cmds constant constructor print_one print_list var_list var_listn function_call symbol_value bgp_path_expr bgp_path bgp_path_tail one_decl decls
 %type <fda> dynamic_attr
 %type <fsa> static_attr
-%type <f> filter filter_body where_filter
+%type <f> filter where_filter
+%type <fl> filter_body
 %type <flv> lvalue
 %type <i> type
 %type <ecs> ec_kind
@@ -467,11 +468,12 @@ CF_GRAMMAR
 
 conf: filter_def ;
 filter_def:
-   FILTER CF_SYM_VOID { $2 = cf_define_symbol($2, SYM_FILTER, NULL); cf_push_scope( $2 ); }
+   FILTER CF_SYM_VOID { $2 = cf_define_symbol($2, SYM_FILTER, filter, NULL); cf_push_scope( $2 ); }
      filter_body {
-     $2->def = $4;
-     $4->name = $2->name;
-     DBG( "We have new filter defined (%s)\n", $2->name );
+     struct filter *f = cfg_alloc(sizeof(struct filter));
+     *f = (struct filter) { .name = $2->name, .root = $4 };
+     $2->filter = f;
+
      cf_pop_scope();
    }
  ;
@@ -483,14 +485,14 @@ filter_eval:
 
 conf: custom_attr ;
 custom_attr: ATTRIBUTE type CF_SYM_VOID ';' {
-  cf_define_symbol($3, SYM_ATTRIBUTE, ca_lookup(new_config->pool, $3->name, $2)->fda);
+  cf_define_symbol($3, SYM_ATTRIBUTE, attribute, ca_lookup(new_config->pool, $3->name, $2)->fda);
 };
 
 conf: bt_test_suite ;
 bt_test_suite:
  BT_TEST_SUITE '(' CF_SYM_FUNCTION ',' text ')' {
   struct f_bt_test_suite *t = cfg_allocz(sizeof(struct f_bt_test_suite));
-  t->fn = $3->def;
+  t->fn = $3->function;
   t->fn_name = $3->name;
   t->dsc = $5;
 
@@ -502,8 +504,8 @@ conf: bt_test_same ;
 bt_test_same:
  BT_TEST_SAME '(' CF_SYM_FUNCTION ',' CF_SYM_FUNCTION ',' NUM ')' {
   struct f_bt_test_suite *t = cfg_allocz(sizeof(struct f_bt_test_suite));
-  t->fn = $3->def;
-  t->cmp = $5->def;
+  t->fn = $3->function;
+  t->cmp = $5->function;
   t->result = $7;
   t->fn_name = $3->name;
   t->dsc = $5->name;
@@ -553,7 +555,7 @@ one_decl:
    type CF_SYM_VOID {
      struct f_val * val = cfg_alloc(sizeof(struct f_val));
      val->type = T_VOID;
-     $2 = cf_define_symbol($2, SYM_VARIABLE | $1, val);
+     $2 = cf_define_symbol($2, SYM_VARIABLE | $1, val, val);
      DBG( "New variable %s type %x\n", $2->name, $1 );
      $$ = f_new_inst(FI_SET, NULL, $2);
    }
@@ -578,22 +580,24 @@ declsn: one_decl { $$.inst = $1; $$.count = 1; }
 
 filter_body:
    function_body {
-     $$ = cfg_alloc(sizeof(struct filter));
-     $$->name = NULL;
      if ($1[0]) {
        const struct f_inst *inst[2] = { $1[0], $1[1] };
-       $$->root = f_postfixify_concat(inst, 2);
+       $$ = f_postfixify_concat(inst, 2);
      }
      else
-       $$->root = f_postfixify($1[1]);
+       $$ = f_postfixify($1[1]);
    }
  ;
 
 filter:
    CF_SYM_FILTER {
-     $$ = $1->def;
+     $$ = $1->filter;
+   }
+ | filter_body {
+     struct filter *f = cfg_alloc(sizeof(struct filter));
+     *f = (struct filter) { .root = $1 };
+     $$ = f;
    }
- | filter_body
  ;
 
 where_filter:
@@ -618,7 +622,7 @@ function_body:
 conf: function_def ;
 function_def:
    FUNCTION CF_SYM_VOID { DBG( "Beginning of function %s\n", $2->name );
-     $2 = cf_define_symbol($2, SYM_FUNCTION, NULL);
+     $2 = cf_define_symbol($2, SYM_FUNCTION, function, NULL);
      cf_push_scope($2);
    } function_params function_body {
      const struct f_inst *catlist[4];
@@ -639,9 +643,10 @@ function_def:
      if ($5[1])
        catlist[count++] = $5[1];
 
-     $2->def = f_postfixify_concat(catlist, count);
-     $2->aux2 = $4.count;
-     DBG("Hmm, we've got one function here - %s\n", $2->name);
+     struct f_line *fl = f_postfixify_concat(catlist, count);
+     fl->args = $4.count;
+     $2->function = fl;
+
      cf_pop_scope();
    }
  ;
@@ -693,7 +698,7 @@ set_atom:
    }
  | CF_SYM_CONSTANT {
      if (!f_valid_set_type(SYM_TYPE($1))) cf_error("%s: set-incompatible type", $1->name);
-     $$ = *(struct f_val *)($1->def);
+     $$ = *$1->val;
    }
  ;
 
@@ -856,9 +861,9 @@ function_call:
  ;
 
 symbol_value:
-   CF_SYM_CONSTANT { $$ = f_new_inst(FI_CONSTANT_INDIRECT, $1->def); }
+   CF_SYM_CONSTANT { $$ = f_new_inst(FI_CONSTANT_INDIRECT, $1->val); }
  | CF_SYM_VARIABLE { $$ = f_new_inst(FI_VARIABLE, $1); }
- | CF_SYM_ATTRIBUTE { $$ = f_new_inst(FI_EA_GET, *((struct f_dynamic_attr *) $1->def)); }
+ | CF_SYM_ATTRIBUTE { $$ = f_new_inst(FI_EA_GET, *$1->attribute); }
  ;
 
 static_attr:
@@ -986,7 +991,7 @@ cmd:
      $$ = f_new_inst(FI_CONDITION, $2, $4, $6);
    }
  | CF_SYM_ATTRIBUTE '=' term ';' {
-   $$ = f_new_inst(FI_EA_SET, $3, *((struct f_dynamic_attr *) $1->def));
+   $$ = f_new_inst(FI_EA_SET, $3, *$1->attribute);
    }
  | CF_SYM_VARIABLE '=' term ';' {
    $$ = f_new_inst(FI_SET, $3, $1);
diff --git a/filter/decl.m4 b/filter/decl.m4
index 5ac62cbd..3043f4fc 100644
--- a/filter/decl.m4
+++ b/filter/decl.m4
@@ -188,9 +188,9 @@ const struct symbol *sym;
 FID_NEW_ARGS
 , const struct symbol *sym
 FID_NEW_BODY
-what->valp = (what->sym = sym)->def;
+what->valp = (what->sym = sym)->val;
 FID_POSTFIXIFY_BODY
-dest->items[pos].vp = (dest->items[pos].sym = what->sym)->def;
+dest->items[pos].vp = (dest->items[pos].sym = what->sym)->val;
 FID_SAME_BODY
 if (strcmp(f1->sym->name, f2->sym->name) || (f1->sym->class != f2->sym->class)) return 0;
 FID_DUMP_BODY
diff --git a/filter/f-inst.c b/filter/f-inst.c
index 4ab46529..6f563873 100644
--- a/filter/f-inst.c
+++ b/filter/f-inst.c
@@ -233,7 +233,7 @@
       /* IP->Quad implicit conversion */
       if ((sym->class == (SYM_VARIABLE | T_QUAD)) && val_is_ip4(&v1))
       {
-	*((struct f_val *) sym->def) = (struct f_val) {
+	*(sym->val) = (struct f_val) {
 	  .type = T_QUAD,
 	  .val.i = ipa_to_u32(v1.val.ip),
 	}; 
@@ -241,7 +241,7 @@
       }
       runtime( "Assigning to variable of incompatible type" );
     }
-    *((struct f_val *) sym->def) = v1;
+    *(sym->val) = v1;
   }
 
     /* some constants have value in a[1], some in *a[0].p, strange. */
@@ -709,7 +709,7 @@
 
     /* Postfixify extracts the function body from the symbol */
     FID_POSTFIXIFY_BODY
-    dest->items[pos].lines[0] = what->sym->def;
+    dest->items[pos].lines[0] = what->sym->function;
     FID_END
 
     /* First push the body on stack */
@@ -727,8 +727,8 @@
       for (const struct f_inst *inst = f1; inst; inst = inst->next)
 	count++;
 
-      if (count != sym->aux2)
-	cf_error("Function %s takes %u arguments, got %u.", sym->name, sym->aux2, count);
+      if (count != sym->function->args)
+	cf_error("Function %s takes %u arguments, got %u.", sym->name, sym->function->args, count);
     FID_END
 
     /* FIXME: Optimization of function comparison. */
diff --git a/filter/f-inst.h b/filter/f-inst.h
index e1d0b675..201be5f8 100644
--- a/filter/f-inst.h
+++ b/filter/f-inst.h
@@ -59,6 +59,7 @@ struct f_line_item {
 /* Line of instructions to be unconditionally executed one after another */
 struct f_line {
   uint len;				/* Line length */
+  u16 args;				/* Function: Args required  */
   struct f_line_item items[0];		/* The items themselves */
 };
 
@@ -81,8 +82,8 @@ extern void (*bt_assert_hook)(int result, const struct f_line_item *assert);
 /* Bird Tests */
 struct f_bt_test_suite {
   node n;			/* Node in config->tests */
-  struct f_line *fn;		/* Root of function */
-  struct f_line *cmp;		/* Compare to this function */
+  const struct f_line *fn;	/* Root of function */
+  const struct f_line *cmp;	/* Compare to this function */
   const char *fn_name;		/* Name of test */
   const char *dsc;		/* Description */
   int result;			/* Desired result */
diff --git a/filter/f-util.c b/filter/f-util.c
index 82aaa385..85f5d1c4 100644
--- a/filter/f-util.c
+++ b/filter/f-util.c
@@ -17,8 +17,8 @@
 
 #define P(a,b) ((a<<8) | b)
 
-char *
-filter_name(struct filter *filter)
+const char *
+filter_name(const struct filter *filter)
 {
   if (!filter)
     return "ACCEPT";
diff --git a/filter/filter.c b/filter/filter.c
index 29e78204..4249d4ee 100644
--- a/filter/filter.c
+++ b/filter/filter.c
@@ -359,15 +359,14 @@ f_eval_buf(const struct f_line *expr, struct linpool *tmp_pool, buffer *buf)
 /**
  * filter_same - compare two filters
  * @new: first filter to be compared
- * @old: second filter to be compared, notice that this filter is
- * damaged while comparing.
+ * @old: second filter to be compared
  *
  * Returns 1 in case filters are same, otherwise 0. If there are
  * underlying bugs, it will rather say 0 on same filters than say
  * 1 on different.
  */
 int
-filter_same(struct filter *new, struct filter *old)
+filter_same(const struct filter *new, const struct filter *old)
 {
   if (old == new)	/* Handle FILTER_ACCEPT and FILTER_REJECT */
     return 1;
diff --git a/filter/filter.h b/filter/filter.h
index d03c6438..26faeaa3 100644
--- a/filter/filter.h
+++ b/filter/filter.h
@@ -48,7 +48,7 @@ struct f_val;
 struct f_line;
 struct filter {
   char *name;
-  struct f_line *root;
+  const struct f_line *root;
 };
 
 struct rte;
@@ -58,8 +58,8 @@ enum filter_return f_eval_rte(const struct f_line *expr, struct rte **rte, struc
 uint f_eval_int(const struct f_line *expr);
 enum filter_return f_eval_buf(const struct f_line *expr, struct linpool *tmp_pool, buffer *buf);
 
-char *filter_name(struct filter *filter);
-int filter_same(struct filter *new, struct filter *old);
+const char *filter_name(const struct filter *filter);
+int filter_same(const struct filter *new, const struct filter *old);
 int f_same(const struct f_line *f1, const struct f_line *f2);
 
 #define FILTER_ACCEPT NULL
diff --git a/nest/config.Y b/nest/config.Y
index fb75c593..c2622ed2 100644
--- a/nest/config.Y
+++ b/nest/config.Y
@@ -179,28 +179,28 @@ proto_name:
    /* EMPTY */ {
      struct symbol *s = cf_default_name(this_proto->protocol->template, &this_proto->protocol->name_counter);
      s->class = this_proto->class;
-     s->def = this_proto;
+     s->proto = this_proto;
      this_proto->name = s->name;
      }
  | CF_SYM_VOID {
-     cf_define_symbol($1, this_proto->class, this_proto);
+     cf_define_symbol($1, this_proto->class, proto, this_proto);
      this_proto->name = $1->name;
    }
  | FROM sym_proto_or_template {
      struct symbol *s = cf_default_name(this_proto->protocol->template, &this_proto->protocol->name_counter);
      s->class = this_proto->class;
-     s->def = this_proto;
+     s->proto = this_proto;
      this_proto->name = s->name;
 
      if (($2->class != SYM_TEMPLATE) && ($2->class != SYM_PROTO)) cf_error("Template or protocol name expected");
-     proto_copy_config(this_proto, $2->def);
+     proto_copy_config(this_proto, $2->proto);
    }
  | CF_SYM_VOID FROM sym_proto_or_template {
-     cf_define_symbol($1, this_proto->class, this_proto);
+     cf_define_symbol($1, this_proto->class, proto, this_proto);
      this_proto->name = $1->name;
 
      if (($3->class != SYM_TEMPLATE) && ($3->class != SYM_PROTO)) cf_error("Template or protocol name expected");
-     proto_copy_config(this_proto, $3->def);
+     proto_copy_config(this_proto, $3->proto);
    }
  ;
 
@@ -256,7 +256,7 @@ channel_end:
 proto_channel: channel_start channel_opt_list channel_end;
 
 
-rtable: CF_SYM_TABLE { $$ = $1->def; } ;
+rtable: CF_SYM_TABLE { $$ = $1->table; } ;
 
 imexport:
    FILTER filter { $$ = $2; }
@@ -544,7 +544,7 @@ r_args:
    }
  | r_args TABLE CF_SYM_TABLE {
      $$ = $1;
-     rt_show_add_table($$, ((struct rtable_config *)$3->def)->table);
+     rt_show_add_table($$, $3->table->table);
      $$->tables_defined_by = RSD_TDB_DIRECT;
    }
  | r_args TABLE ALL {
@@ -556,7 +556,7 @@ r_args:
    }
  | r_args IMPORT TABLE CF_SYM_PROTO '.' r_args_channel {
      $$ = $1;
-     struct proto_config *cf = (void *) $4->def;
+     struct proto_config *cf = $4->proto;
      if (!cf->proto) cf_error("%s is not a protocol", $4->name);
      struct channel *c = proto_find_channel_by_name(cf->proto, $6);
      if (!c) cf_error("Channel %s.%s not found", $4->name, $6);
@@ -587,7 +587,7 @@ r_args:
      $$->filtered = 1;
    }
  | r_args export_mode CF_SYM_PROTO {
-     struct proto_config *c = (struct proto_config *) $3->def;
+     struct proto_config *c = (struct proto_config *) $3->proto;
      $$ = $1;
      if ($$->export_mode) cf_error("Export specified twice");
      if (!c->proto) cf_error("%s is not a protocol", $3->name);
@@ -596,7 +596,7 @@ r_args:
      $$->tables_defined_by = RSD_TDB_INDIRECT;
    }
  | r_args export_mode CF_SYM_PROTO '.' r_args_channel {
-     struct proto_config *c = (struct proto_config *) $3->def;
+     struct proto_config *c = (struct proto_config *) $3->proto;
      $$ = $1;
      if ($$->export_mode) cf_error("Export specified twice");
      if (!c->proto) cf_error("%s is not a protocol", $3->name);
@@ -606,7 +606,7 @@ r_args:
      $$->tables_defined_by = RSD_TDB_INDIRECT;
    }
  | r_args PROTOCOL CF_SYM_PROTO {
-     struct proto_config *c = (struct proto_config *) $3->def;
+     struct proto_config *c = (struct proto_config *) $3->proto;
      $$ = $1;
      if ($$->show_protocol) cf_error("Protocol specified twice");
      if (!c->proto) cf_error("%s is not a protocol", $3->name);
diff --git a/nest/proto.c b/nest/proto.c
index d4a333d0..77bf082a 100644
--- a/nest/proto.c
+++ b/nest/proto.c
@@ -977,7 +977,7 @@ protos_commit(struct config *new, struct config *old, int force_reconfig, int ty
       {
 	/* Found match, let's check if we can smoothly switch to new configuration */
 	/* No need to check description */
-	nc = sym->def;
+	nc = sym->proto;
 	nc->proto = p;
 
 	/* We will try to reconfigure protocol p */
@@ -1905,7 +1905,7 @@ proto_apply_cmd_symbol(struct symbol *s, void (* cmd)(struct proto *, uintptr_t,
     return;
   }
 
-  cmd(((struct proto_config *)s->def)->proto, arg, 0);
+  cmd(s->proto->proto, arg, 0);
   cli_msg(0, "");
 }
 
@@ -1948,7 +1948,7 @@ proto_get_named(struct symbol *sym, struct protocol *pr)
     if (sym->class != SYM_PROTO)
       cf_error("%s: Not a protocol", sym->name);
 
-    p = ((struct proto_config *) sym->def)->proto;
+    p = sym->proto->proto;
     if (!p || p->proto != pr)
       cf_error("%s: Not a %s protocol", sym->name, pr->name);
   }
diff --git a/nest/protocol.h b/nest/protocol.h
index 6c04071b..82b46261 100644
--- a/nest/protocol.h
+++ b/nest/protocol.h
@@ -489,7 +489,7 @@ struct channel_config {
 
   struct proto_config *parent;		/* Where channel is defined (proto or template) */
   struct rtable_config *table;		/* Table we're attached to */
-  struct filter *in_filter, *out_filter; /* Attached filters */
+  const struct filter *in_filter, *out_filter; /* Attached filters */
   struct channel_limit rx_limit;	/* Limit for receiving routes from protocol
 					   (relevant when in_keep_filtered is active) */
   struct channel_limit in_limit;	/* Limit for importing routes from protocol */
@@ -511,8 +511,8 @@ struct channel {
   struct proto *proto;
 
   struct rtable *table;
-  struct filter *in_filter;		/* Input filter */
-  struct filter *out_filter;		/* Output filter */
+  const struct filter *in_filter;	/* Input filter */
+  const struct filter *out_filter;	/* Output filter */
   struct channel_limit rx_limit;	/* Receive limit (for in_keep_filtered) */
   struct channel_limit in_limit;	/* Input limit */
   struct channel_limit out_limit;	/* Output limit */
diff --git a/nest/route.h b/nest/route.h
index c7ed80ff..7c9f3005 100644
--- a/nest/route.h
+++ b/nest/route.h
@@ -297,7 +297,7 @@ rte *rte_find(net *net, struct rte_src *src);
 rte *rte_get_temp(struct rta *);
 void rte_update2(struct channel *c, const net_addr *n, rte *new, struct rte_src *src);
 /* rte_update() moved to protocol.h to avoid dependency conflicts */
-int rt_examine(rtable *t, net_addr *a, struct proto *p, struct filter *filter);
+int rt_examine(rtable *t, net_addr *a, struct proto *p, const struct filter *filter);
 rte *rt_export_merged(struct channel *c, net *net, rte **rt_free, linpool *pool, int silent);
 void rt_refresh_begin(rtable *t, struct channel *c);
 void rt_refresh_end(rtable *t, struct channel *c);
@@ -335,7 +335,7 @@ struct rt_show_data {
   struct rt_show_data_rtable *last_table; /* Last table in output */
   struct fib_iterator fit;		/* Iterator over networks in table */
   int verbose, tables_defined_by;
-  struct filter *filter;
+  const struct filter *filter;
   struct proto *show_protocol;
   struct proto *export_protocol;
   struct channel *export_channel;
diff --git a/nest/rt-table.c b/nest/rt-table.c
index 6c8e662e..f05bd718 100644
--- a/nest/rt-table.c
+++ b/nest/rt-table.c
@@ -398,7 +398,7 @@ static rte *
 export_filter_(struct channel *c, rte *rt0, rte **rt_free, linpool *pool, int silent)
 {
   struct proto *p = c->proto;
-  struct filter *filter = c->out_filter;
+  const struct filter *filter = c->out_filter;
   struct proto_stats *stats = &c->stats;
   rte *rt;
   int v;
@@ -1362,7 +1362,7 @@ rte_update2(struct channel *c, const net_addr *n, rte *new, struct rte_src *src)
 {
   struct proto *p = c->proto;
   struct proto_stats *stats = &c->stats;
-  struct filter *filter = c->in_filter;
+  const struct filter *filter = c->in_filter;
   rte *dummy = NULL;
   net *nn;
 
@@ -1503,7 +1503,7 @@ rte_modify(rte *old)
 
 /* Check rtable for best route to given net whether it would be exported do p */
 int
-rt_examine(rtable *t, net_addr *a, struct proto *p, struct filter *filter)
+rt_examine(rtable *t, net_addr *a, struct proto *p, const struct filter *filter)
 {
   net *n = net_find(t, a);
   rte *rt = n ? n->routes : NULL;
@@ -2106,13 +2106,13 @@ rt_new_table(struct symbol *s, uint addr_type)
 {
   /* Hack that allows to 'redefine' the master table */
   if ((s->class == SYM_TABLE) &&
-      (s->def == new_config->def_tables[addr_type]) &&
+      (s->table == new_config->def_tables[addr_type]) &&
       ((addr_type == NET_IP4) || (addr_type == NET_IP6)))
-    return s->def;
+    return s->table;
 
   struct rtable_config *c = cfg_allocz(sizeof(struct rtable_config));
 
-  cf_define_symbol(s, SYM_TABLE, c);
+  cf_define_symbol(s, SYM_TABLE, table, c);
   c->name = s->name;
   c->addr_type = addr_type;
   c->gc_max_ops = 1000;
@@ -2171,7 +2171,7 @@ static struct rtable_config *
 rt_find_table_config(struct config *cf, char *name)
 {
   struct symbol *sym = cf_find_symbol(cf, name);
-  return (sym && (sym->class == SYM_TABLE)) ? sym->def : NULL;
+  return (sym && (sym->class == SYM_TABLE)) ? sym->table : NULL;
 }
 
 /**
diff --git a/proto/mrt/mrt.h b/proto/mrt/mrt.h
index b2cec09d..4dfb1b19 100644
--- a/proto/mrt/mrt.h
+++ b/proto/mrt/mrt.h
@@ -23,7 +23,7 @@ struct mrt_config {
 
   struct rtable_config *table_cf;
   const char *table_expr;
-  struct filter *filter;
+  const struct filter *filter;
   const char *filename;
   uint period;
   int always_add_path;
@@ -41,7 +41,7 @@ struct mrt_proto {
 struct mrt_dump_data {
   const char *table_expr;
   struct rtable *table_ptr;
-  struct filter *filter;
+  const struct filter *filter;
   char *filename;
 };
 
@@ -61,7 +61,7 @@ struct mrt_table_dump_state {
 					/* Configuration information */
   const char *table_expr;		/* Wildcard for table name (or NULL) */
   struct rtable *table_ptr;		/* Explicit table (or NULL) */
-  struct filter *filter;		/* Optional filter */
+  const struct filter *filter;		/* Optional filter */
   const char *filename;			/* Filename pattern */
   int always_add_path;			/* Always use *_ADDPATH message subtypes */
 
diff --git a/sysdep/unix/krt.c b/sysdep/unix/krt.c
index ded5dfe4..24a4168d 100644
--- a/sysdep/unix/krt.c
+++ b/sysdep/unix/krt.c
@@ -562,7 +562,7 @@ static struct rte *
 krt_export_net(struct krt_proto *p, net *net, rte **rt_free)
 {
   struct channel *c = p->p.main_channel;
-  struct filter *filter = c->out_filter;
+  const struct filter *filter = c->out_filter;
   rte *rt;
 
   if (c->ra_mode == RA_MERGED)
diff --git a/sysdep/unix/main.c b/sysdep/unix/main.c
index 0fdd5b34..b0d764fa 100644
--- a/sysdep/unix/main.c
+++ b/sysdep/unix/main.c
@@ -94,11 +94,9 @@ drop_gid(gid_t gid)
 static inline void
 add_num_const(char *name, int val)
 {
-  struct symbol *s = cf_get_symbol(name);
-  s->class = SYM_CONSTANT | T_INT;
-  s->def = cfg_allocz(sizeof(struct f_val));
-  SYM_TYPE(s) = T_INT;
-  SYM_VAL(s).i = val;
+  struct f_val *v = cfg_alloc(sizeof(struct f_val));
+  *v = (struct f_val) { .type = T_INT, .val.i = val };
+  cf_define_symbol(cf_get_symbol(name), SYM_CONSTANT | T_INT, val, v);
 }
 
 /* the code of read_iproute_table() is based on