C++ res_init函数代码示例

int 
main(int count, char **options) {
        int 		res;
        
        if (strcmp(options[1], "-d") != 0) {
            res = daemon(0, 0);
            printf("return value: %s\n", res);        
        }
        res_init();
        _res.retrans = 4;
        _res.retry = 2;
        int 		running = 1;
        if (parse_config()) {
            printf("error reading configuration!\n");
            return 1;
        }
        if (open_status_socket())
            printf("error opening status socket; no status will be provided\n");
        stat(config_file, &config_last_mod);
        printf("last config modified time: %s\n", ctime(&config_last_mod.st_mtime));
        while (running) {
            struct config_interfaces *cur = config;
            printf("checking if conf file has changed\n");
            if (config_changed()) {
                printf("modifying:\n");
                clear_config(config);
                cur = 0;
                if (parse_config())
                   printf("error reading configuration!\n");
                else
                    cur = config;
            }
            while (cur) {
                if (check_interface(cur)) {
                    printf("media type: %s\n", mediatype(cur->if_name));
                    if (strcmp(mediatype(cur->if_name), "Ethernet") == 0) {
                        if (setup_ethernetinterface(cur))
                            break;
                    } else if (strcmp(mediatype(cur->if_name), "IEEE802.11") == 0) {
                        if (setup_wlaninterface(cur))
                            break;
                    }
                }
                cur = cur->next;
            }
            printf("Sleeping... waiting %d seconds\n", poll_wait);
            sleep(poll_wait);
            printf("restarto\n");
        }
        return 0;
}

int
nres_search(struct nres *block)
{
	register char	*cp, *domain;
	int		n;

	if ((_res.options & RES_INIT) == 0 && res_init() == -1)
		return (-1);

	block->retries = 0;	/* start clock */
	if (block->search_index < 0)
		return (-1);
	/* only try exact match for reverse cases */
	if (block->reverse) {
		(void) nres_querydomain(block->name, (char *)NULL,
							block->search_name);
		block->search_index = -1;
		return (0);
	}

	for (cp = block->name, n = 0; *cp; cp++)
		if (*cp == '.')
			n++;
	/* n indicates the presence of trailing dots */

	if (block->search_index == 0) {
		if (n == 0 && (cp = nres_hostalias(block->name))) {
			(void) strncpy(block->search_name, cp, 2 * MAXDNAME);
			block->search_index = -1; /* if hostalias try 1 name */
			return (0);
		}
	}
	if ((n == 0 || *--cp != '.') && (_res.options & RES_DEFNAMES)) {
		domain = _res.dnsrch[block->search_index];
		if (domain) {
			(void) nres_querydomain(block->name, domain,
							block->search_name);
			block->search_index++;
			return (0);
		}
	}
	if (n) {
		(void) nres_querydomain(block->name, (char *)NULL,
							block->search_name);
		block->search_index = -1;
		return (0);
	}
	block->search_index = -1;
	return (-1);
}

errno_t
monitor_common_res_init(TALLOC_CTX *mem_ctx,
                        struct sbus_request *sbus_req,
                        void *no_data)
{
    int ret;

    ret = res_init();
    if (ret != 0) {
        return EIO;
    }

    return EOK;
}

static void resolver_init(void)
{
#ifdef G_OS_UNIX
	static time_t resolv_conf_mtime = 0;
	struct stat s;

	if (g_stat("/etc/resolv.conf", &s) == 0 &&
	    s.st_mtime != resolv_conf_mtime) {
		debug_print("Reloading /etc/resolv.conf\n");
		resolv_conf_mtime = s.st_mtime;
		res_init();
	}
#endif
}

int
utGetDomainInfo(char **szDefDomain, char **szDefServer)
{
  if (res_init() != 0)
    return 1;
  *szDefDomain = calloc(257, sizeof(char));
  memcpy(*szDefDomain, _res.defdname, 256);
  if (strnlen(*szDefDomain, 256) == 0)
    *szDefDomain[0] = '-';
  *szDefServer = calloc(IFNAMSIZ, sizeof(char));
  memcpy(*szDefServer, inet_ntoa(_res.nsaddr_list[0].sin_addr), IFNAMSIZ-1);
  res_close();
  return 0;
}

static int my_res_init()
{
#ifdef JDNS_OS_MAC
    res_init_func mac_res_init;

    // look up res_init in the system library (qt does this, not sure why)
    mac_res_init = (res_init_func)dlsym(RTLD_NEXT, "res_init");
    if(!mac_res_init)
        return -1;
    return mac_res_init();
#else
    return res_init();
#endif
}

std::vector<std::string> CNetworkLinux::GetNameServers(void)
{
   std::vector<std::string> result;

#if defined(TARGET_DARWIN)
  FILE* pipe = popen("scutil --dns | grep \"nameserver\" | tail -n2", "r");
  usleep(100000);
  if (pipe)
  {
    std::vector<std::string> tmpStr;
    char buffer[256] = {'\0'};
    if (fread(buffer, sizeof(char), sizeof(buffer), pipe) > 0 && !ferror(pipe))
    {
      tmpStr = StringUtils::Split(buffer, "\n");
      for (unsigned int i = 0; i < tmpStr.size(); i ++)
      {
        // result looks like this - > '  nameserver[0] : 192.168.1.1'
        // 2 blank spaces + 13 in 'nameserver[0]' + blank + ':' + blank == 18 :)
        if (tmpStr[i].length() >= 18)
          result.push_back(tmpStr[i].substr(18));
      }
    }
    pclose(pipe);
  } 
  if (result.empty())
    CLog::Log(LOGWARNING, "Unable to determine nameserver");
#elif defined(TARGET_ANDROID)
  char nameserver[PROP_VALUE_MAX];

  if (__system_property_get("net.dns1",nameserver))
    result.push_back(nameserver);
  if (__system_property_get("net.dns2",nameserver))
    result.push_back(nameserver);
  if (__system_property_get("net.dns3",nameserver))
    result.push_back(nameserver);

  if (!result.size())
       CLog::Log(LOGWARNING, "Unable to determine nameserver");
#else
   res_init();

   for (int i = 0; i < _res.nscount; i ++)
   {
      std::string ns = inet_ntoa(((struct sockaddr_in *)&_res.nsaddr_list[i])->sin_addr);
      result.push_back(ns);
   }
#endif
   return result;
}

static int make_resolv (char *ifname, dhcp_t *dhcp, int wait)
{
  FILE *f;
  struct stat buf;
  char resolvconf[PATH_MAX];
  address_t *address;

  if (!stat ("/sbin/resolvconf", &buf))
    {
      logger (LOG_DEBUG, "sending DNS information to resolvconf");
      snprintf (resolvconf, PATH_MAX, "/sbin/resolvconf -a %s", ifname);
      f = popen (resolvconf, "w");

      if (!f)
	logger (LOG_ERR, "popen: %m");
    }
  else
    {
      if (! (f = fopen(RESOLVFILE, "w")))
	logger (LOG_ERR, "fopen `%s': %m", RESOLVFILE);
    }

  if (f) 
    {
      fprintf (f, "# Generated by dhcpcd for interface %s\n", ifname);
      if (dhcp->dnssearch)
	fprintf (f, "search %s\n", dhcp->dnssearch);
      else if (dhcp->dnsdomain) {
	fprintf (f, "search %s\n", dhcp->dnsdomain);
      }

      for (address = dhcp->dnsservers; address; address = address->next)
	fprintf (f, "nameserver %s\n", inet_ntoa (address->address));

      if (resolvconf)
	{
	  pclose (f);
	  logger (LOG_DEBUG, "resolvconf completed");
	}
      else
	fclose (f);
    }
  else
    return -1;

  /* Refresh the local resolver */
  res_init ();
  return 0;
}

struct hostent *
gethostbyname(const char *name)
{
  struct hostent *hp = NULL;

  if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
    h_errno = NETDB_INTERNAL;
    return (NULL);
  }
  if (_res.options & RES_USE_INET6) {		/* XXX */
    hp = gethostbyname2(name, AF_INET6);	/* XXX */
    if (hp)					/* XXX */
      return (hp);			        /* XXX */
  }						/* XXX */
  return (gethostbyname2(name, AF_INET));
}

int main( int argc, char ** argv ) {

   char domain[ MYMAX ];
   int len = 0;
   unsigned int res;
   int a, i, j, k, l, n, t;

   res_init();

   len = res_query( argv[1], C_IN, T_MX, buff, MYMAX );

   printf( "MX records for gmail.com len =%d\n", len );

   a = ReadHeader();

   if ( getAnswerRecordCount() > 0 ) {
      printf("\n;; Answer section:\n");
      for ( i = 0; i < getAnswerRecordCount(); i++ ) {
         a = ReadRecord( a );
      }
   }

   if ( getAuthRecordCount() > 0 ) {
      printf("\n;; Authority section:\n");
      for ( i = 0; i < getAuthRecordCount(); i++ ) {
         a = ReadRecord( a );
      }
   }

   if ( getAdditionalRecordCount() > 0 ) {
      printf("\n;; Additional section:\n");
      for ( i = 0; i < getAdditionalRecordCount(); i++ ) {
         a = ReadRecord( a );
      }
   }

/*
   for( a=0; a < len; a++ ) {
      printf( "[ %d ] = %d, %c\n", a, buff[ a ], buff[ a ] );
   }

   for( ; a < len; a++ ) {
      printf( "buff[ %d ] = %d, %c\n", a, buff[ a ], buff[ a ] );
   }
*/   

}

std::vector<IpAddr>
ip_utils::getLocalNameservers()
{
    std::vector<IpAddr> res;
#if defined __ANDROID__ || defined _WIN32 || TARGET_OS_IPHONE
#ifdef _MSC_VER
#pragma message (__FILE__ "(" STR2(__LINE__) ") : -NOTE- " "Not implemented")
#else
#warning "Not implemented"
#endif
#else
    if (not (_res.options & RES_INIT))
        res_init();
    res.insert(res.end(), _res.nsaddr_list, _res.nsaddr_list + _res.nscount);
#endif
    return res;
}

void Resolver::setNameserver(char *nameserver) throw (std::invalid_argument)
{
	if (nameserver == NULL) {
		throw std::invalid_argument("Cannot use empty nameserver");
	}

	int ret;
	struct addrinfo *result;
	struct addrinfo hints;

	memset(&hints, 0, sizeof(hints));
	hints.ai_family = AF_UNSPEC;
	hints.ai_protocol = 0;

	ret = getaddrinfo(nameserver, "domain", &hints, &result);
	if (ret != 0) {
		std::string err = std::string("Unable to resolve address '") + nameserver + "': " + gai_strerror(ret);
		throw std::invalid_argument(err);
	}

	res_init();

	if (result->ai_addr->sa_family == AF_INET) {
#ifdef DEBUG
		std::cerr << "Setting up IPv4 DNS server with address " << nameserver << std::endl;
#endif
		struct sockaddr_in *sock4 = (struct sockaddr_in *) result->ai_addr;
		memcpy((void *)&_res.nsaddr_list[0], sock4, result->ai_addrlen);
		_res.nscount = 1;
	} else if (result->ai_addr->sa_family == AF_INET6) {
		std::cerr << "IPv6 addresses are not supported for DNS server." << std::endl;
		/*
		struct sockaddr_in6 *sock6 = (struct sockaddr_in6 *) result->ai_addr;
		memcpy((void *)&_res.nsaddr_list[0], sock6, result->ai_addrlen);
		_res.nscount = 1;
		*/
	} else {
		std::string err = std::string("Unable to resolve address for ") + nameserver + ": " + "Unknown address family";
		throw std::invalid_argument(err);
	}

	freeaddrinfo(result);

	this->nameserver = nameserver;
}

/* ________________________________________________________________________ */
int nslookup_main(int argc, char **argv)
{
	struct hostent *host;

	if (argc < 2 || *argv[1]=='-') {
		show_usage();
	}

	res_init();
	server_print();
	if (is_ip_address(argv[1])) {
		host = gethostbyaddr_wrapper(argv[1]);
	} else {
		host = gethostbyname(argv[1]);
	}
	hostent_fprint(host, 0);
	return EXIT_SUCCESS;
}

struct nb_dns_info *
nb_dns_init(char *errstr)
{
	register struct nb_dns_info *nd;

	nd = (struct nb_dns_info *)malloc(sizeof(*nd));
	if (nd == NULL) {
		snprintf(errstr, NB_DNS_ERRSIZE, "nb_dns_init: malloc(): %s",
		    my_strerror(errno));
		return (NULL);
	}
	memset(nd, 0, sizeof(*nd));
	nd->s = -1;

	/* XXX should be able to init static hostent struct some other way */
	(void)gethostbyname("localhost.");

	if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
		snprintf(errstr, NB_DNS_ERRSIZE, "res_init() failed");
		free(nd);
		return (NULL);
	}
	nd->s = socket(PF_INET, SOCK_DGRAM, 0);
	if (nd->s < 0) {
		snprintf(errstr, NB_DNS_ERRSIZE, "socket(): %s",
		    my_strerror(errno));
		free(nd);
		return (NULL);
	}

	/* XXX should use resolver config */
	nd->server = _res.nsaddr_list[0];

	if (connect(nd->s, (struct sockaddr *)&nd->server,
	    sizeof(struct sockaddr)) < 0) {
		snprintf(errstr, NB_DNS_ERRSIZE, "connect(%s): %s",
		    inet_ntoa(nd->server.sin_addr), my_strerror(errno));
		close(nd->s);
		free(nd);
		return (NULL);
	}

	return (nd);
}

struct hostent *
gethostbyname2(const char *name, int af)
{
	int	r;

	res_init();

	r = _gethostbyname(name, af, &_hostent, _entbuf, sizeof(_entbuf),
	    &h_errno);
	if (r) {
		h_errno = NETDB_INTERNAL;
		errno = r;
	}

	if (h_errno)
		return (NULL);

	return (&_hostent);
}