Gisle Vanem's init patch for Windows

  Changelog for the c-ares project

* June 10

- Gisle Vanem's init patch for Windows:

  The init_by_resolv_conf() function fetches the DNS-server(s)

  from a series of registry branches.

  This can be wrong in the case where DHCP has assigned nameservers, but the

  user has overridden these servers with other prefered settings. Then it's

  wrong to use the DHCPNAMESERVER setting in registry.

  In the case of no global DHCP-assigned or fixed servers, but DNS server(s)

  per adapter, one has to query the adapter branches.  But how can c-ares know

  which adapter is valid for use? AFAICS it can't. There could be one adapter

  that is down (e.g. a VPN adapter).

  So it's better to leave this to the IP Helper API (iphlapi) available in

  Win-98/2000 and later. My patch falls-back to the old way if not available.

* June 8

- James Bursa fixed an init issue for RISC OS.

#ifdef WIN32

#include "nameser.h"

#include <iphlpapi.h>

#include <malloc.h>

#else

#include <sys/param.h>

#include <sys/time.h>

  return ARES_SUCCESS;

}

#ifdef WIN32

static int get_res_size_nt(HKEY hKey, char *subkey, int *size)

{

  return RegQueryValueEx(hKey, subkey, 0, NULL, NULL, size);

}

/* Warning: returns a dynamically allocated buffer, the user MUST

#ifdef WIN32

/*

 * Warning: returns a dynamically allocated buffer, the user MUST

 * use free() if the function returns 1

 */

static int get_res_nt(HKEY hKey, char *subkey, char **obuf)

static int get_res_nt(HKEY hKey, const char *subkey, char **obuf)

{

  /* Test for the size we need */

  int size = 0;

  DWORD size = 0;

  int result;

  result = RegQueryValueEx(hKey, subkey, 0, NULL, NULL, &size);

  if ((result != ERROR_SUCCESS && result != ERROR_MORE_DATA) || !size)

    return 0;

  *obuf = malloc(size+1);

  if (!*obuf)

    return 0;

  if (RegQueryValueEx(hKey, subkey, 0, NULL, *obuf, &size) != ERROR_SUCCESS)

  {

  return 1;

}

static int get_res_interfaces_nt(HKEY hKey, char *subkey, char **obuf)

static int get_res_interfaces_nt(HKEY hKey, const char *subkey, char **obuf)

{

  char enumbuf[39]; /* GUIDs are 38 chars + 1 for NULL */

  int enum_size = 39;

  DWORD enum_size = 39;

  int idx = 0;

  HKEY hVal;

  while (RegEnumKeyEx(hKey, idx++, enumbuf, &enum_size, 0,

                      NULL, NULL, NULL) != ERROR_NO_MORE_ITEMS)

  {

    int rc;

    enum_size = 39;

    if (RegOpenKeyEx(hKey, enumbuf, 0, KEY_QUERY_VALUE, &hVal) !=

        ERROR_SUCCESS)

      continue;

    if (!get_res_nt(hVal, subkey, obuf))

      RegCloseKey(hVal);

    else

    {

    rc = get_res_nt(hVal, subkey, obuf);

      RegCloseKey(hVal);

    if (rc)

      return 1;

    }

  }

  return 0;

}

static int get_iphlpapi_dns_info (char *ret_buf, size_t ret_size)

{

  FIXED_INFO    *fi   = alloca (sizeof(*fi));

  DWORD          size = sizeof (*fi);

  DWORD WINAPI (*GetNetworkParams) (FIXED_INFO*, DWORD*);  /* available only on Win-98/2000+ */

  HMODULE        handle;

  IP_ADDR_STRING *ipAddr;

  int            i, count = 0;

  int            debug  = 0;

  size_t         ip_size = sizeof("255.255.255.255,")-1;

  size_t         left = ret_size;

  char          *ret = ret_buf;

  if (!fi)

     return (0);

  handle = LoadLibrary ("iphlpapi.dll");

  if (!handle)

     return (0);

  (void*)GetNetworkParams = GetProcAddress (handle, "GetNetworkParams");

  if (!GetNetworkParams)

     goto quit;

  if ((*GetNetworkParams) (fi, &size) != ERROR_BUFFER_OVERFLOW)

     goto quit;

  fi = alloca (size);

  if (!fi || (*GetNetworkParams) (fi, &size) != ERROR_SUCCESS)

     goto quit;

  if (debug)

  {

    printf ("Host Name: %s\n", fi->HostName);

    printf ("Domain Name: %s\n", fi->DomainName);

    printf ("DNS Servers:\n"

            "    %s (primary)\n", fi->DnsServerList.IpAddress.String);

  }

  if (inet_addr(fi->DnsServerList.IpAddress.String) != INADDR_NONE &&

      left > ip_size)

  {

    ret += sprintf (ret, "%s,", fi->DnsServerList.IpAddress.String);

    left -= ret - ret_buf;

    count++;

  }

  for (i = 0, ipAddr = fi->DnsServerList.Next; ipAddr && left > ip_size;

       ipAddr = ipAddr->Next, i++)

  {

    if (inet_addr(ipAddr->IpAddress.String) != INADDR_NONE)

    {

       ret += sprintf (ret, "%s,", ipAddr->IpAddress.String);

       left -= ret - ret_buf;

       count++;

    }

    if (debug)

       printf ("    %s (secondary %d)\n", ipAddr->IpAddress.String, i+1);

  }

quit:

  if (handle)

     FreeLibrary (handle);

  if (debug && left <= ip_size)

     printf ("Too many nameservers. Truncating to %d addressess", count);

  if (ret > ret_buf)

     ret[-1] = '\0';

  return (count);

}

#endif

static int init_by_resolv_conf(ares_channel channel)

#ifdef WIN32

    /*

  NameServer info via IPHLPAPI (IP helper API):

    GetNetworkParams() should be the trusted source for this.

    Available in Win-98/2000 and later. If that fail, fall-back to

    registry information.

  NameServer Registry:

   On Windows 9X, the DNS server can be found in:

  DWORD data_type;

  DWORD bytes;

  DWORD result;

  DWORD keysize = MAX_PATH;

  char  buf[256];

  status = ARES_EFILE;

  if (channel->nservers > -1)  /* don't override ARES_OPT_SERVER */

     return ARES_SUCCESS;

  if (get_iphlpapi_dns_info(buf,sizeof(buf)) > 0)

  {

    status = config_nameserver(&servers, &nservers, buf);

    if (status == ARES_SUCCESS)

       goto okay;

  }

  if (IsNT)

  {

    RegCloseKey(mykey);

  }

  if (status != ARES_EFILE)

  {

    /*

      if (!channel->lookups) {

      status = config_lookup(channel, "file bind");

      }

    */

  if (status == ARES_SUCCESS)

    status = ARES_EOF;

  }

#elif defined(riscos)

    }

  /* If we got any name server entries, fill them in. */

okay:

  if (servers)

    {

      channel->servers = servers;