ares_init.c

rtlinux-3.2源码

/* Copyright 1998 by the Massachusetts Institute of Technology.
 *
 * Permission to use, copy, modify, and distribute this
 * software and its documentation for any purpose and without
 * fee is hereby granted, provided that the above copyright
 * notice appear in all copies and that both that copyright
 * notice and this permission notice appear in supporting
 * documentation, and that the name of M.I.T. not be used in
 * advertising or publicity pertaining to distribution of the
 * software without specific, written prior permission.
 * M.I.T. makes no representations about the suitability of
 * this software for any purpose.  It is provided "as is"
 * without express or implied warranty.
 *
 * CHANGELOG: this file has been modified by Sergio Perez Alca駃z <[e-mail]> 
 *            Departamento de Inform醫ica de Sistemas y Computadores          
 *            Universidad Polit閏nica de Valencia                             
 *            Valencia (Spain)    
 *            Date: April 2003                                          
 *
 */

#include "ares_private.h"

#define htons HTONS
#define htonl HTONL

extern int gettimeofday(struct timeval *tv, struct timezone *tz);

static int init_by_options(ares_channel channel, struct ares_options *options,
			   int optmask);
static int init_by_defaults(ares_channel channel);

int ares_init(ares_channel *channelptr)
{
  return ares_init_options(channelptr, NULL, 0);
}


int ares_init_options(ares_channel *channelptr, struct ares_options *options,
		      int optmask)
{
  ares_channel channel;
  int i, status;
  struct server_state *server;

  channel = malloc(sizeof(struct ares_channeldata));
  if (!channel)
    return ARES_ENOMEM;

  /* Set everything to distinguished values so we know they haven't
   * been set yet.
   */
  channel->flags = -1;
  channel->timeout = -1;
  channel->tries = -1;
  channel->ndots = -1;
  channel->udp_port = -1;
  channel->tcp_port = -1;
  channel->nservers = -1;
  channel->ndomains = -1;
  channel->nsort = -1;
  channel->lookups = NULL;

  /* Initialize configuration by each of the four sources, from highest
   * precedence to lowest.
   */
  status = init_by_options(channel, options, optmask);
  if (status == ARES_SUCCESS)
    status = init_by_defaults(channel);
  if (status != ARES_SUCCESS)
    {
      /* Something failed; clean up memory we may have allocated. */
      if (channel->nservers != -1)
	free(channel->servers);
      if (channel->ndomains != -1)
	{
	  for (i = 0; i < channel->ndomains; i++)
	    free(channel->domains[i]);
	  free(channel->domains);
	}
      if (channel->nsort != -1)
	free(channel->sortlist);
      free(channel->lookups);
      free(channel);
      return status;
    }

  /* Trim to one server if ARES_FLAG_PRIMARY is set. */
  if ((channel->flags & ARES_FLAG_PRIMARY) && channel->nservers > 1)
    channel->nservers = 1;

  /* Initialize server states. */
  for (i = 0; i < channel->nservers; i++)
    {
      server = &channel->servers[i];
      server->udp_socket = -1;
      server->tcp_socket = -1;
      server->tcp_lenbuf_pos = 0;
      server->tcp_buffer = NULL;
      server->qhead = NULL;
      server->qtail = NULL;
    }

  /* Choose a somewhat random query ID.  The main point is to avoid
   * collisions with stale queries.  An attacker trying to spoof a DNS
   * answer also has to guess the query ID, but it's only a 16-bit
   * field, so there's not much to be done about that.
   */

//  channel->next_id = (RetrieveClock() ^ os_current_process()) & 0xffff;
  {
    struct timeval time;
    gettimeofday(&time,NULL);
    channel->next_id = (time.tv_usec ^ time.tv_sec) & 0xffff;
  }

  channel->queries = NULL;

  *channelptr = channel;
  return ARES_SUCCESS;
}

static int init_by_options(ares_channel channel, struct ares_options *options,
			   int optmask)
{
  int i;

  /* Easy stuff. */
  if ((optmask & ARES_OPT_FLAGS) && channel->flags == -1)
    channel->flags = options->flags;
  if ((optmask & ARES_OPT_TIMEOUT) && channel->timeout == -1)
    channel->timeout = options->timeout;
  if ((optmask & ARES_OPT_TRIES) && channel->tries == -1)
    channel->tries = options->tries;
  if ((optmask & ARES_OPT_NDOTS) && channel->ndots == -1)
    channel->ndots = options->ndots;
  if ((optmask & ARES_OPT_UDP_PORT) && channel->udp_port == -1)
    channel->udp_port = options->udp_port;
  if ((optmask & ARES_OPT_TCP_PORT) && channel->tcp_port == -1)
    channel->tcp_port = options->tcp_port;

  /* Copy the servers, if given. */
  if ((optmask & ARES_OPT_SERVERS) && channel->nservers == -1)
    {
      channel->servers =
	malloc(options->nservers * sizeof(struct server_state));
      if (!channel->servers && options->nservers != 0)
	return ARES_ENOMEM;
      for (i = 0; i < options->nservers; i++)
	channel->servers[i].addr = options->servers[i];
      channel->nservers = options->nservers;
    }

  /* Copy the domains, if given.  Keep channel->ndomains consistent so
   * we can clean up in case of error.
   */
  if ((optmask & ARES_OPT_DOMAINS) && channel->ndomains == -1)
    {
      channel->domains = malloc(options->ndomains * sizeof(char *));
      if (!channel->domains && options->ndomains != 0)
	return ARES_ENOMEM;
      for (i = 0; i < options->ndomains; i++)
	{
	  channel->ndomains = i;
	  channel->domains[i] = strdup(options->domains[i]);
	  if (!channel->domains[i])
	    return ARES_ENOMEM;
	}
      channel->ndomains = options->ndomains;
    }

  /* Set lookups, if given. */
  if ((optmask & ARES_OPT_LOOKUPS) && !channel->lookups)
    {
      channel->lookups = strdup(options->lookups);
      if (!channel->lookups)
	return ARES_ENOMEM;
    }

  return ARES_SUCCESS;
}

static int init_by_defaults(ares_channel channel)
{
  if (channel->flags == -1)
    channel->flags = 0;
  if (channel->timeout == -1)
    channel->timeout = DEFAULT_TIMEOUT;
  if (channel->tries == -1)
    channel->tries = DEFAULT_TRIES;
  if (channel->ndots == -1)
    channel->ndots = 1;
  if (channel->udp_port == -1)
    channel->udp_port = htons(NAMESERVER_PORT);
  if (channel->tcp_port == -1)
    channel->tcp_port = htons(NAMESERVER_PORT);

  if (channel->nservers == -1)
    {
      /* If nobody specified servers, try a local named. */
      channel->servers = malloc(sizeof(struct server_state));
      if (!channel->servers)
	return ARES_ENOMEM;
      channel->servers[0].addr.s_addr = htonl(INADDR_LOOPBACK);
      channel->nservers = 1;
    }

  if (channel->ndomains == -1)
    {
      channel->domains = malloc(0);
      channel->ndomains = 0;
    }

  if (channel->nsort == -1)
    {
      channel->sortlist = NULL;
      channel->nsort = 0;
    }

  if (!channel->lookups)
    {
      channel->lookups = strdup("bf");
      if (!channel->lookups)
	return ARES_ENOMEM;
    }

  return ARES_SUCCESS;
}