bird/conf/cf-lex.l

/*
 *	BIRD -- Configuration Lexer
 *
 *	(c) 1998--2000 Martin Mares <mj@ucw.cz>
 *
 *	Can be freely distributed and used under the terms of the GNU GPL.
 */

/**
 * DOC: Lexical analyzer
 *
 * The lexical analyzer used for configuration files and CLI commands
 * is generated using the |flex| tool accompanied by a couple of
 * functions maintaining the hash tables containing information about
 * symbols and keywords.
 *
 * Each symbol is represented by a &symbol structure containing name
 * of the symbol, its lexical scope, symbol class (%SYM_PROTO for a name of a protocol,
 * %SYM_NUMBER for a numeric constant etc.) and class dependent data.
 * When an unknown symbol is encountered, it's automatically added to the
 * symbol table with class %SYM_VOID.
 *
 * The keyword tables are generated from the grammar templates
 * using the |gen_keywords.m4| script.
 */

%{
#undef REJECT     /* Avoid name clashes */

#include <errno.h>
#include <stdlib.h>
#include <stdarg.h>

#include "nest/bird.h"
#include "nest/route.h"
#include "filter/filter.h"
#include "conf/conf.h"
#include "conf/cf-parse.tab.h"
#include "lib/string.h"

struct keyword {
  byte *name;
  int value;
  struct keyword *next;
};

#include "conf/keywords.h"

#define KW_HASH_SIZE 64
static struct keyword *kw_hash[KW_HASH_SIZE];
static int kw_hash_inited;

#define SYM_HASH_SIZE 128
#define SYM_MAX_LEN 32

struct sym_scope {
  struct sym_scope *next;		/* Next on scope stack */
  struct symbol *name;			/* Name of this scope */
  int active;				/* Currently entered */
};
static struct sym_scope *conf_this_scope;

int conf_lino;

static int cf_hash(byte *c);
static struct symbol *cf_find_sym(byte *c, unsigned int h0);

linpool *cfg_mem;

int (*cf_read_hook)(byte *buf, unsigned int max);

#define YY_INPUT(buf,result,max) result = cf_read_hook(buf, max);
#define YY_NO_UNPUT
#define YY_FATAL_ERROR(msg) cf_error(msg)

%}

%option noyywrap

%x COMMENT CCOMM CLI

ALPHA [a-zA-Z_]
DIGIT [0-9]
XIGIT [0-9a-fA-F]
ALNUM [a-zA-Z_0-9]
WHITE [ \t]

%%

{DIGIT}+\.{DIGIT}+\.{DIGIT}+\.{DIGIT}+ {
#ifdef IPV6
  if (ipv4_pton_u32(yytext, &cf_lval.i32))
    return RTRID;
  cf_error("Invalid IPv4 address %s", yytext);
#else
  if (ip_pton(yytext, &cf_lval.a))
    return IPA;
  cf_error("Invalid IP address %s", yytext);
#endif
}

({XIGIT}*::|({XIGIT}*:){3,})({XIGIT}*|{DIGIT}+\.{DIGIT}+\.{DIGIT}+\.{DIGIT}+) {
#ifdef IPV6
  if (ip_pton(yytext, &cf_lval.a))
    return IPA;
  cf_error("Invalid IP address %s", yytext);
#else
  cf_error("This is an IPv4 router, therefore IPv6 addresses are not supported");
#endif
}

0x{DIGIT}+ {
  char *e;
  long int l;
  errno = 0;
  l = strtoul(yytext+2, &e, 16);
  if (e && *e || errno == ERANGE || (long int)(int) l != l)
    cf_error("Number out of range");
  cf_lval.i = l;
  return NUM;
}

{DIGIT}+ {
  char *e;
  long int l;
  errno = 0;
  l = strtoul(yytext, &e, 10);
  if (e && *e || errno == ERANGE || (long int)(int) l != l)
    cf_error("Number out of range");
  cf_lval.i = l;
  return NUM;
}

{ALPHA}{ALNUM}* {
  unsigned int h = cf_hash(yytext);
  struct keyword *k = kw_hash[h & (KW_HASH_SIZE-1)];
  while (k)
    {
      if (!strcmp(k->name, yytext))
	{
	  if (k->value > 0)
	    return k->value;
	  else
	    {
	      cf_lval.i = -k->value;
	      return ENUM;
	    }
	}
      k=k->next;
    }
  cf_lval.s = cf_find_sym(yytext, h);
  return SYM;
}

<CLI>(.|\n) {
  BEGIN(INITIAL);
  return CLI_MARKER;
}

[={}:;,.()+*/%<>~\[\]?!-] {
  return yytext[0];
}

["][^"\n]*["] {
  yytext[yyleng-1] = 0;
  cf_lval.t = cfg_strdup(yytext+1);
  return TEXT;
}

["][^"\n]*\n	cf_error("Unterminated string");

<INITIAL,COMMENT><<EOF>>	return END;

{WHITE}+

\n	conf_lino++;

#	BEGIN(COMMENT);

\/\*	BEGIN(CCOMM);

.	cf_error("Unknown character");

<COMMENT>\n {
  conf_lino++;
  BEGIN(INITIAL);
}

<COMMENT>.

<CCOMM>\*\/	BEGIN(INITIAL);
<CCOMM>\n	conf_lino++;
<CCOMM>\/\*	cf_error("Comment nesting not supported");
<CCOMM><<EOF>>	cf_error("Unterminated comment");
<CCOMM>.

\!\= return NEQ;
\<\= return LEQ;
\>\= return GEQ;
\&\& return AND;
\|\| return OR;

%%

static int
cf_hash(byte *c)
{
  unsigned int h = 13;

  while (*c)
    h = (h * 37) + *c++;
  return h;
}

static struct symbol *
cf_new_sym(byte *c, unsigned int h)
{
  struct symbol *s, **ht;
  int l;

  if (!new_config->sym_hash)
    new_config->sym_hash = cfg_allocz(SYM_HASH_SIZE * sizeof(struct keyword *));
  ht = new_config->sym_hash;
  l = strlen(c);
  if (l > SYM_MAX_LEN)
    cf_error("Symbol too long");
  s = cfg_alloc(sizeof(struct symbol) + l);
  s->next = ht[h];
  ht[h] = s;
  s->scope = conf_this_scope;
  s->class = SYM_VOID;
  s->def = NULL;
  s->aux = 0;
  strcpy(s->name, c);
  return s;
}

static struct symbol *
cf_find_sym(byte *c, unsigned int h0)
{
  unsigned int h = h0 & (SYM_HASH_SIZE-1);
  struct symbol *s, **ht;

  if (ht = new_config->sym_hash)
    {
      for(s = ht[h]; s; s=s->next)
	if (!strcmp(s->name, c) && s->scope->active)
	  return s;
    }
  if (new_config->sym_fallback)
    {
      /* We know only top-level scope is active */
      for(s = new_config->sym_fallback[h]; s; s=s->next)
	if (!strcmp(s->name, c) && s->scope->active)
	  return s;
    }
  return cf_new_sym(c, h);
}

/**
 * cf_find_symbol - find a symbol by name
 * @c: symbol name
 *
 * This functions searches the symbol table for a symbol of given
 * name. First it examines the current scope, then the second recent
 * one and so on until it either finds the symbol and returns a pointer
 * to its &symbol structure or reaches the end of the scope chain
 * and returns %NULL to signify no match.
 */
struct symbol *
cf_find_symbol(byte *c)
{
  return cf_find_sym(c, cf_hash(c));
}

struct symbol *
cf_default_name(char *template, int *counter)
{
  char buf[32];
  struct symbol *s;
  char *perc = strchr(template, '%');

  for(;;)
    {
      bsprintf(buf, template, ++(*counter));
      s = cf_find_sym(buf, cf_hash(buf));
      if (!s)
	break;
      if (s->class == SYM_VOID)
	return s;
      if (!perc)
	break;
    }
  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_sym(sym->name, cf_hash(sym->name) & (SYM_HASH_SIZE-1));
    }
  sym->class = type;
  sym->def = def;
  return sym;
}

static void
cf_lex_init_kh(void)
{
  struct keyword *k;

  for(k=keyword_list; k->name; k++)
    {
      unsigned h = cf_hash(k->name) & (KW_HASH_SIZE-1);
      k->next = kw_hash[h];
      kw_hash[h] = k;
    }
  kw_hash_inited = 1;
}

/**
 * cf_lex_init - initialize the lexer
 * @is_cli: true if we're going to parse CLI command, false for configuration
 *
 * cf_lex_init() initializes the lexical analyzer and prepares it for
 * parsing of a new input.
 */
void
cf_lex_init(int is_cli)
{
  if (!kw_hash_inited)
    cf_lex_init_kh();
  conf_lino = 1;
  yyrestart(NULL);
  if (is_cli)
    BEGIN(CLI);
  else
    BEGIN(INITIAL);
  conf_this_scope = cfg_allocz(sizeof(struct sym_scope));
  conf_this_scope->active = 1;
}

/**
 * cf_push_scope - enter new scope
 * @sym: symbol representing scope name
 *
 * If we want to enter a new scope to process declarations inside
 * a nested block, we can just call cf_push_scope() to push a new
 * scope onto the scope stack which will cause all new symbols to be
 * defined in this scope and all existing symbols to be sought for
 * in all scopes stored on the stack.
 */
void
cf_push_scope(struct symbol *sym)
{
  struct sym_scope *s = cfg_alloc(sizeof(struct sym_scope));

  s->next = conf_this_scope;
  conf_this_scope = s;
  s->active = 1;
  s->name = sym;
}

/**
 * cf_pop_scope - leave a scope
 *
 * cf_pop_scope() pops the topmost scope from the scope stack,
 * leaving all its symbols in the symbol table, but making them
 * invisible to the rest of the config.
 */
void
cf_pop_scope(void)
{
  conf_this_scope->active = 0;
  conf_this_scope = conf_this_scope->next;
  ASSERT(conf_this_scope);
}

struct symbol *
cf_walk_symbols(struct config *cf, struct symbol *sym, int *pos)
{
  for(;;)
    {
      if (!sym)
	{
	  if (*pos >= SYM_HASH_SIZE)
	    return NULL;
	  sym = cf->sym_hash[(*pos)++];
	}
      else
	sym = sym->next;
      if (sym && sym->scope->active)
	return sym;
    }
}

/**
 * cf_symbol_class_name - get name of a symbol class
 * @sym: symbol
 *
 * This function returns a string representing the class
 * of the given symbol.
 */
char *
cf_symbol_class_name(struct symbol *sym)
{
  switch (sym->class)
    {
    case SYM_VOID:
      return "undefined";
    case SYM_PROTO:
      return "protocol";
    case SYM_NUMBER:
      return "numeric constant";
    case SYM_FUNCTION:
      return "function";
    case SYM_FILTER:
      return "filter";
    case SYM_TABLE:
      return "routing table";
    case SYM_IPA:
      return "network address";
    default:
      return "unknown type";
    }
}


/**
 * DOC: Parser
 *
 * Both the configuration and CLI commands are analyzed using a syntax
 * driven parser generated by the |bison| tool from a grammar which
 * is constructed from information gathered from grammar snippets by
 * the |gen_parser.m4| script.
 *
 * Grammar snippets are files (usually with extension |.Y|) contributed
 * by various BIRD modules in order to provide information about syntax of their
 * configuration and their CLI commands. Each snipped consists of several
 * section, each of them starting with a special keyword: |CF_HDR| for
 * a list of |#include| directives needed by the C code, |CF_DEFINES|
 * for a list of C declarations, |CF_DECLS| for |bison| declarations
 * including keyword definitions specified as |CF_KEYWORDS|, |CF_GRAMMAR|
 * for the grammar rules, |CF_CODE| for auxiliary C code and finally
 * |CF_END| at the end of the snippet.
 *
 * To create references between the snippets, it's possible to define
 * multi-part rules by utilizing the |CF_ADDTO| macro which adds a new
 * alternative to a multi-part rule.
 *
 * CLI commands are defined using a |CF_CLI| macro. Its parameters are:
 * the list of keywords determining the command, the list of parameters,
 * help text for the parameters and help text for the command.
 *
 * Values of |enum| filter types can be defined using |CF_ENUM| with
 * the following parameters: name of filter type, prefix common for all
 * literals of this type, names of all the possible values.
 */