/* Copyright 1998, 2011, 2013 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.

 */

#include "ares_setup.h"

#ifdef HAVE_NETINET_IN_H

#  include <netinet/in.h>

#endif

#ifdef HAVE_NETDB_H

#  include <netdb.h>

#endif

#ifdef HAVE_ARPA_INET_H

#  include <arpa/inet.h>

#endif

#ifdef HAVE_ARPA_NAMESER_H

#  include <arpa/nameser.h>

#else

#  include "nameser.h"

#endif

#ifdef HAVE_ARPA_NAMESER_COMPAT_H

#  include <arpa/nameser_compat.h>

#endif

#ifdef HAVE_STRINGS_H

#include <strings.h>

#endif

#include "ares.h"

#include "ares_inet_net_pton.h"

#include "bitncmp.h"

#include "ares_platform.h"

#include "ares_nowarn.h"

#include "ares_private.h"

#ifdef WATT32

#undef WIN32

#endif

struct host_query {

  /* Arguments passed to ares_gethostbyname() */

  ares_channel channel;

  char *name;

  ares_host_callback callback;

  void *arg;

  int sent_family; /* this family is what was is being used */

  int want_family; /* this family is what is asked for in the API */

  const char *remaining_lookups;

  int timeouts;

};

static void next_lookup(struct host_query *hquery, int status_code);

static void host_callback(void *arg, int status, int timeouts,

                          unsigned char *abuf, int alen);

static void end_hquery(struct host_query *hquery, int status,

                       struct hostent *host);

static int fake_hostent(const char *name, int family,

                        ares_host_callback callback, void *arg);

static int file_lookup(const char *name, int family, struct hostent **host);

static void sort_addresses(struct hostent *host,

                           const struct apattern *sortlist, int nsort);

static void sort6_addresses(struct hostent *host,

                            const struct apattern *sortlist, int nsort);

static int get_address_index(const struct in_addr *addr,

                             const struct apattern *sortlist, int nsort);

static int get6_address_index(const struct ares_in6_addr *addr,

                              const struct apattern *sortlist, int nsort);

void ares_gethostbyname(ares_channel channel, const char *name, int family,

                        ares_host_callback callback, void *arg)

{

  struct host_query *hquery;

  /* Right now we only know how to look up Internet addresses - and unspec

     means try both basically. */

  switch (family) {

  case AF_INET:

  case AF_INET6:

  case AF_UNSPEC:

    break;

  default:

    callback(arg, ARES_ENOTIMP, 0, NULL);

    return;

  }

  if (fake_hostent(name, family, callback, arg))

    return;

  /* Allocate and fill in the host query structure. */

  hquery = ares_malloc(sizeof(struct host_query));

  if (!hquery)

    {

      callback(arg, ARES_ENOMEM, 0, NULL);

      return;

    }

  hquery->channel = channel;

  hquery->name = ares_strdup(name);

  hquery->want_family = family;

  hquery->sent_family = -1; /* nothing is sent yet */

  if (!hquery->name) {

    ares_free(hquery);

    callback(arg, ARES_ENOMEM, 0, NULL);

    return;

  }

  hquery->callback = callback;

  hquery->arg = arg;

  hquery->remaining_lookups = channel->lookups;

  hquery->timeouts = 0;

  /* Start performing lookups according to channel->lookups. */

  next_lookup(hquery, ARES_ECONNREFUSED /* initial error code */);

}

static void next_lookup(struct host_query *hquery, int status_code)

{

  const char *p;

  struct hostent *host;

  int status = status_code;

  for (p = hquery->remaining_lookups; *p; p++)

    {

      switch (*p)

        {

        case 'b':

          /* DNS lookup */

          hquery->remaining_lookups = p + 1;

          if ((hquery->want_family == AF_INET6) ||

              (hquery->want_family == AF_UNSPEC)) {

            /* if inet6 or unspec, start out with AAAA */

            hquery->sent_family = AF_INET6;

            ares_search(hquery->channel, hquery->name, C_IN, T_AAAA,

                        host_callback, hquery);

          }

          else {

            hquery->sent_family = AF_INET;

            ares_search(hquery->channel, hquery->name, C_IN, T_A,

                        host_callback, hquery);

          }

          return;

        case 'f':

          /* Host file lookup */

          status = file_lookup(hquery->name, hquery->want_family, &host);

          /* this status check below previously checked for !ARES_ENOTFOUND,

             but we should not assume that this single error code is the one

             that can occur, as that is in fact no longer the case */

          if (status == ARES_SUCCESS)

            {

              end_hquery(hquery, status, host);

              return;

            }

          status = status_code;   /* Use original status code */

          break;

        }

    }

  end_hquery(hquery, status, NULL);

}

static void host_callback(void *arg, int status, int timeouts,

                          unsigned char *abuf, int alen)

{

  struct host_query *hquery = (struct host_query *) arg;

  ares_channel channel = hquery->channel;

  struct hostent *host = NULL;

  hquery->timeouts += timeouts;

  if (status == ARES_SUCCESS)

    {

      if (hquery->sent_family == AF_INET)

        {

          status = ares_parse_a_reply(abuf, alen, &host, NULL, NULL);

          if (host && channel->nsort)

            sort_addresses(host, channel->sortlist, channel->nsort);

        }

      else if (hquery->sent_family == AF_INET6)

        {

          status = ares_parse_aaaa_reply(abuf, alen, &host, NULL, NULL);

          if ((status == ARES_ENODATA || status == ARES_EBADRESP ||

               (status == ARES_SUCCESS && host && host->h_addr_list[0] == NULL)) &&

                hquery->want_family == AF_UNSPEC) {

            /* The query returned something but either there were no AAAA

               records (e.g. just CNAME) or the response was malformed.  Try

               looking up A instead. */

            if (host)

              ares_free_hostent(host);

            hquery->sent_family = AF_INET;

            ares_search(hquery->channel, hquery->name, C_IN, T_A,

                        host_callback, hquery);

            return;

          }

          if (host && channel->nsort)

            sort6_addresses(host, channel->sortlist, channel->nsort);

        }

      end_hquery(hquery, status, host);

    }

  else if ((status == ARES_ENODATA || status == ARES_EBADRESP ||

            status == ARES_ETIMEOUT) && (hquery->sent_family == AF_INET6 &&

            hquery->want_family == AF_UNSPEC))

    {

      /* The AAAA query yielded no useful result.  Now look up an A instead. */

      hquery->sent_family = AF_INET;

      ares_search(hquery->channel, hquery->name, C_IN, T_A, host_callback,

                  hquery);

    }

  else if (status == ARES_EDESTRUCTION)

    end_hquery(hquery, status, NULL);

  else

    next_lookup(hquery, status);

}

static void end_hquery(struct host_query *hquery, int status,

                       struct hostent *host)

{

  hquery->callback(hquery->arg, status, hquery->timeouts, host);

  if (host)

    ares_free_hostent(host);

  ares_free(hquery->name);

  ares_free(hquery);

}

/* If the name looks like an IP address, fake up a host entry, end the

 * query immediately, and return true.  Otherwise return false.

 */

static int fake_hostent(const char *name, int family,

                        ares_host_callback callback, void *arg)

{

  struct hostent hostent;

  char *aliases[1] = { NULL };

  char *addrs[2];

  int result = 0;

  struct in_addr in;

  struct ares_in6_addr in6;

  if (family == AF_INET || family == AF_INET6)

    {

      /* It only looks like an IP address if it's all numbers and dots. */

      int numdots = 0, valid = 1;

      const char *p;

      for (p = name; *p; p++)

        {

          if (!ISDIGIT(*p) && *p != '.') {

            valid = 0;

            break;

          } else if (*p == '.') {

            numdots++;

          }

        }

      /* if we don't have 3 dots, it is illegal

       * (although inet_addr doesn't think so).

       */

      if (numdots != 3 || !valid)

        result = 0;

      else

        result = ((in.s_addr = inet_addr(name)) == INADDR_NONE ? 0 : 1);

      if (result)

        family = AF_INET;

    }

  if (family == AF_INET6)

    result = (ares_inet_pton(AF_INET6, name, &in6) < 1 ? 0 : 1);

  if (!result)

    return 0;

  if (family == AF_INET)

    {

      hostent.h_length = (int)sizeof(struct in_addr);

      addrs[0] = (char *)∈

    }

  else if (family == AF_INET6)

    {

      hostent.h_length = (int)sizeof(struct ares_in6_addr);

      addrs[0] = (char *)&in6;

    }

  /* Duplicate the name, to avoid a constness violation. */

  hostent.h_name = ares_strdup(name);

  if (!hostent.h_name)

    {

      callback(arg, ARES_ENOMEM, 0, NULL);

      return 1;

    }

  /* Fill in the rest of the host structure and terminate the query. */

  addrs[1] = NULL;

  hostent.h_aliases = aliases;

  hostent.h_addrtype = aresx_sitoss(family);

  hostent.h_addr_list = addrs;

  callback(arg, ARES_SUCCESS, 0, &hostent);

  ares_free((char *)(hostent.h_name));

  return 1;

}

/* This is an API method */

int ares_gethostbyname_file(ares_channel channel, const char *name,

                            int family, struct hostent **host)

{

  int result;

  /* We only take the channel to ensure that ares_init() been called. */

  if(channel == NULL)

    {

      /* Anything will do, really.  This seems fine, and is consistent with

         other error cases. */

      *host = NULL;

      return ARES_ENOTFOUND;

    }

  /* Just chain to the internal implementation we use here; it's exactly

   * what we want.

   */

  result = file_lookup(name, family, host);

  if(result != ARES_SUCCESS)

    {

      /* We guarantee a NULL hostent on failure. */

      *host = NULL;

    }

  return result;

}

static int file_lookup(const char *name, int family, struct hostent **host)

{

  FILE *fp;

  char **alias;

  int status;

  int error;

#ifdef WIN32

  char PATH_HOSTS[MAX_PATH];

  win_platform platform;

  PATH_HOSTS[0] = '\0';

  platform = ares__getplatform();

  if (platform == WIN_NT) {

    char tmp[MAX_PATH];

    HKEY hkeyHosts;

    if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_NT_KEY, 0, KEY_READ,

                     &hkeyHosts) == ERROR_SUCCESS)

    {

      DWORD dwLength = MAX_PATH;

      RegQueryValueEx(hkeyHosts, DATABASEPATH, NULL, NULL, (LPBYTE)tmp,

                      &dwLength);

      ExpandEnvironmentStrings(tmp, PATH_HOSTS, MAX_PATH);

      RegCloseKey(hkeyHosts);

    }

  }

  else if (platform == WIN_9X)

    GetWindowsDirectory(PATH_HOSTS, MAX_PATH);

  else

    return ARES_ENOTFOUND;

  strcat(PATH_HOSTS, WIN_PATH_HOSTS);

#elif defined(WATT32)

  extern const char *_w32_GetHostsFile (void);

  const char *PATH_HOSTS = _w32_GetHostsFile();

  if (!PATH_HOSTS)

    return ARES_ENOTFOUND;

#endif

  fp = fopen(PATH_HOSTS, "r");

  if (!fp)

    {

      error = ERRNO;

      switch(error)

        {

        case ENOENT:

        case ESRCH:

          return ARES_ENOTFOUND;

        default:

          DEBUGF(fprintf(stderr, "fopen() failed with error: %d %s\n",

                         error, strerror(error)));

          DEBUGF(fprintf(stderr, "Error opening file: %s\n",

                         PATH_HOSTS));

          *host = NULL;

          return ARES_EFILE;

        }

    }

  while ((status = ares__get_hostent(fp, family, host)) == ARES_SUCCESS)

    {

      if (strcasecmp((*host)->h_name, name) == 0)

        break;

      for (alias = (*host)->h_aliases; *alias; alias++)

        {

          if (strcasecmp(*alias, name) == 0)

            break;

        }

      if (*alias)

        break;

      ares_free_hostent(*host);

    }

  fclose(fp);

  if (status == ARES_EOF)

    status = ARES_ENOTFOUND;

  if (status != ARES_SUCCESS)

    *host = NULL;

  return status;

}

static void sort_addresses(struct hostent *host,

                           const struct apattern *sortlist, int nsort)

{

  struct in_addr a1, a2;

  int i1, i2, ind1, ind2;

  /* This is a simple insertion sort, not optimized at all.  i1 walks

   * through the address list, with the loop invariant that everything

   * to the left of i1 is sorted.  In the loop body, the value at i1 is moved

   * back through the list (via i2) until it is in sorted order.

   */

  for (i1 = 0; host->h_addr_list[i1]; i1++)

    {

      memcpy(&a1, host->h_addr_list[i1], sizeof(struct in_addr));

      ind1 = get_address_index(&a1, sortlist, nsort);

      for (i2 = i1 - 1; i2 >= 0; i2--)

        {

          memcpy(&a2, host->h_addr_list[i2], sizeof(struct in_addr));

          ind2 = get_address_index(&a2, sortlist, nsort);

          if (ind2 <= ind1)

            break;

          memcpy(host->h_addr_list[i2 + 1], &a2, sizeof(struct in_addr));

        }

      memcpy(host->h_addr_list[i2 + 1], &a1, sizeof(struct in_addr));

    }

}

/* Find the first entry in sortlist which matches addr.  Return nsort

 * if none of them match.

 */

static int get_address_index(const struct in_addr *addr,

                             const struct apattern *sortlist,

                             int nsort)

{

  int i;

  for (i = 0; i < nsort; i++)

    {

      if (sortlist[i].family != AF_INET)

        continue;

      if (sortlist[i].type == PATTERN_MASK)

        {

          if ((addr->s_addr & sortlist[i].mask.addr4.s_addr)

              == sortlist[i].addrV4.s_addr)

            break;

        }

      else

        {

          if (!ares__bitncmp(&addr->s_addr, &sortlist[i].addrV4.s_addr,

                             sortlist[i].mask.bits))

            break;

        }

    }

  return i;

}

static void sort6_addresses(struct hostent *host,

                            const struct apattern *sortlist, int nsort)

{

  struct ares_in6_addr a1, a2;

  int i1, i2, ind1, ind2;

  /* This is a simple insertion sort, not optimized at all.  i1 walks

   * through the address list, with the loop invariant that everything

   * to the left of i1 is sorted.  In the loop body, the value at i1 is moved

   * back through the list (via i2) until it is in sorted order.

   */

  for (i1 = 0; host->h_addr_list[i1]; i1++)

    {

      memcpy(&a1, host->h_addr_list[i1], sizeof(struct ares_in6_addr));

      ind1 = get6_address_index(&a1, sortlist, nsort);

      for (i2 = i1 - 1; i2 >= 0; i2--)

        {

          memcpy(&a2, host->h_addr_list[i2], sizeof(struct ares_in6_addr));

          ind2 = get6_address_index(&a2, sortlist, nsort);

          if (ind2 <= ind1)

            break;

          memcpy(host->h_addr_list[i2 + 1], &a2, sizeof(struct ares_in6_addr));

        }

      memcpy(host->h_addr_list[i2 + 1], &a1, sizeof(struct ares_in6_addr));

    }

}

/* Find the first entry in sortlist which matches addr.  Return nsort

 * if none of them match.

 */

static int get6_address_index(const struct ares_in6_addr *addr,

                              const struct apattern *sortlist,

                              int nsort)

{

  int i;

  for (i = 0; i < nsort; i++)

    {

      if (sortlist[i].family != AF_INET6)

        continue;

      if (!ares__bitncmp(addr, &sortlist[i].addrV6, sortlist[i].mask.bits))

        break;

    }

  return i;

}