hostip.c

/***************************************************************************
 *                                  _   _ ____  _     
 *  Project                     ___| | | |  _ \| |    
 *                             / __| | | | |_) | |    
 *                            | (__| |_| |  _ <| |___ 
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2004, Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
 * are also available at http://curl.haxx.se/docs/copyright.html.
 * 
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the COPYING file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 * $Id$
 ***************************************************************************/

#include "setup.h"

#include <string.h>
#include <errno.h>

#define _REENTRANT

#if defined(WIN32) && !defined(__GNUC__) || defined(__MINGW32__)
#include <malloc.h>
#else
#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#ifdef HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif
#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_STDLIB_H
#include <stdlib.h>	/* required for free() prototypes */
#endif
#ifdef	VMS
#include <in.h>
#include <inet.h>
#include <stdlib.h>
#endif
#endif

#ifdef HAVE_SETJMP_H
#include <setjmp.h>
#endif

#ifdef WIN32
#include <process.h>
#endif

#if (defined(NETWARE) && defined(__NOVELL_LIBC__))
#undef in_addr_t
#define in_addr_t unsigned long
#endif

#include "urldata.h"
#include "sendf.h"
#include "hostip.h"
#include "hash.h"
#include "share.h"
#include "strerror.h"
#include "url.h"

#define _MPRINTF_REPLACE /* use our functions only */
#include <curl/mprintf.h>

#if defined(HAVE_INET_NTOA_R) && !defined(HAVE_INET_NTOA_R_DECL)
#include "inet_ntoa_r.h"
#endif

/* The last #include file should be: */
#ifdef CURLDEBUG
#include "memdebug.h"
#endif

#ifndef ARES_SUCCESS
#define ARES_SUCCESS CURLE_OK
#endif

#define CURL_TIMEOUT_RESOLVE 300 /* when using asynch methods, we allow this
                                    many seconds for a name resolve */

/* These two symbols are for the global DNS cache */
static curl_hash hostname_cache;
static int host_cache_initialized;


static void freednsentry(void *freethis);

/*
 * my_getaddrinfo() is the generic low-level name resolve API within this
 * source file. There exist three versions of this function - for different
 * name resolve layers (selected at build-time). They all take this same set
 * of arguments
 */
static Curl_addrinfo *my_getaddrinfo(struct connectdata *conn,
                                     char *hostname,
                                     int port,
                                     int *waitp);

#if (!defined(HAVE_GETHOSTBYNAME_R) || defined(USE_ARES) || \
     defined(USE_THREADING_GETHOSTBYNAME)) && \
     !defined(ENABLE_IPV6)
static struct hostent* pack_hostent(char** buf, struct hostent* orig);
#endif

#ifdef USE_THREADING_GETHOSTBYNAME
#ifdef DEBUG_THREADING_GETHOSTBYNAME
/* If this is defined, provide tracing */
#define TRACE(args)  \
 do { trace_it("%u: ", __LINE__); trace_it args; } while (0)

static void trace_it (const char *fmt, ...);
#else
#define TRACE(x)
#endif

static bool init_gethostbyname_thread (struct connectdata *conn,
                                       const char *hostname, int port);
struct thread_data {
  HANDLE thread_hnd;
  unsigned thread_id;
  DWORD  thread_status;
  curl_socket_t dummy_sock;   /* dummy for Curl_multi_ares_fdset() */
};
#endif

/*
 * Curl_global_host_cache_init() initializes and sets up a global DNS cache.
 * Global DNS cache is general badness. Do not use. This will be removed in
 * a future version. Use the share interface instead!
 */
void Curl_global_host_cache_init(void)
{
  if (!host_cache_initialized) {
    Curl_hash_init(&hostname_cache, 7, freednsentry);
    host_cache_initialized = 1;
  }
}

/*
 * Return a pointer to the global cache
 */
curl_hash *Curl_global_host_cache_get(void)
{
  return &hostname_cache;
}

/*
 * Destroy and cleanup the global DNS cache
 */
void Curl_global_host_cache_dtor(void)
{
  if (host_cache_initialized) {
    Curl_hash_clean(&hostname_cache);
    host_cache_initialized = 0;
  }
}

/*
 * Minor utility-function:
 * Count the number of characters that an integer takes up.
 */
static int _num_chars(int i)
{
  int chars = 0;

  /* While the number divided by 10 is greater than one, 
   * re-divide the number by 10, and increment the number of 
   * characters by 1.
   *
   * this relies on the fact that for every multiple of 10, 
   * a new digit is added onto every number
   */
  do {
    chars++;

    i = (int) i / 10;
  } while (i >= 1);

  return chars;
}

/*
 * Minor utility-function:
 * Create a hostcache id string for the DNS caching.
 */
static char *
create_hostcache_id(char *server, int port, size_t *entry_len)
{
  char *id = NULL;

  /* Get the length of the new entry id */
  *entry_len = strlen(server) + /* Hostname length */
    1 +                         /* ':' seperator */
    _num_chars(port);     /* number of characters the port will take up */
  
  /* Allocate the new entry id */
  id = malloc(*entry_len + 1); /* 1 extra for the zero terminator */
  if (!id)
    return NULL;

  /* Create the new entry */
  sprintf(id, "%s:%d", server, port);

  return id; /* return pointer to the string */
}

struct hostcache_prune_data {
  int cache_timeout;
  time_t now;
};

/*
 * This function is set as a callback to be called for every entry in the DNS
 * cache when we want to prune old unused entries.
 *
 * Returning non-zero means remove the entry, return 0 to keep it in the
 * cache.
 */
static int
hostcache_timestamp_remove(void *datap, void *hc)
{
  struct hostcache_prune_data *data = 
    (struct hostcache_prune_data *) datap;
  struct Curl_dns_entry *c = (struct Curl_dns_entry *) hc;
  
  if ((data->now - c->timestamp < data->cache_timeout) ||
      c->inuse) {
    /* please don't remove */
    return 0;
  }
  
  /* fine, remove */
  return 1;
}

/*
 * Prune the DNS cache. This assumes that a lock has already been taken.
 */
static void
hostcache_prune(curl_hash *hostcache, int cache_timeout, time_t now)
{
  struct hostcache_prune_data user;

  user.cache_timeout = cache_timeout;
  user.now = now;

  Curl_hash_clean_with_criterium(hostcache, 
                                 (void *) &user, 
                                 hostcache_timestamp_remove);
}

/*
 * Library-wide function for pruning the DNS cache. This function takes and
 * returns the appropriate locks.
 */
void Curl_hostcache_prune(struct SessionHandle *data)
{
  time_t now;

  if(data->set.dns_cache_timeout == -1)
    /* cache forever means never prune! */
    return;

  if(data->share)
    Curl_share_lock(data, CURL_LOCK_DATA_DNS, CURL_LOCK_ACCESS_SINGLE);

  time(&now);

  /* Remove outdated and unused entries from the hostcache */
  hostcache_prune(data->hostcache,
                  data->set.dns_cache_timeout,
                  now);

  if(data->share)
    Curl_share_unlock(data, CURL_LOCK_DATA_DNS);
}

#ifdef HAVE_SIGSETJMP
/* Beware this is a global and unique instance. This is used to store the
   return address that we can jump back to from inside a signal handler. This
   is not thread-safe stuff. */
sigjmp_buf curl_jmpenv;
#endif


/*
 * cache_resolv_response() stores a 'Curl_addrinfo' struct in the DNS cache.
 *
 * When calling Curl_resolv() has resulted in a response with a returned
 * address, we call this function to store the information in the dns
 * cache etc
 *
 * Returns the Curl_dns_entry entry pointer or NULL if the storage failed.
 */
static struct Curl_dns_entry *
cache_resolv_response(struct SessionHandle *data,
                      Curl_addrinfo *addr,
                      char *hostname,
                      int port)
{
  char *entry_id;
  size_t entry_len;
  struct Curl_dns_entry *dns;
  time_t now;

  /* Create an entry id, based upon the hostname and port */
  entry_id = create_hostcache_id(hostname, port, &entry_len);
  /* If we can't create the entry id, fail */
  if (!entry_id)
    return NULL;

  /* Create a new cache entry */
  dns = (struct Curl_dns_entry *) malloc(sizeof(struct Curl_dns_entry));
  if (!dns) {
    Curl_freeaddrinfo(addr);
    free(entry_id);
    return NULL;
  }

  dns->inuse = 0;   /* init to not used */
  dns->addr = addr; /* this is the address(es) */

  /* Store the resolved data in our DNS cache. This function may return a
     pointer to an existing struct already present in the hash, and it may
     return the same argument we pass in. Make no assumptions. */
  dns = Curl_hash_add(data->hostcache, entry_id, entry_len+1, (void *)dns);
  if(!dns) {
    /* Major badness, run away. When this happens, the 'dns' data has
       already been cleared up by Curl_hash_add(). */
    free(entry_id);
    return NULL;
  }
  time(&now);

  dns->timestamp = now; /* used now */
  dns->inuse++;         /* mark entry as in-use */

  /* free the allocated entry_id again */
  free(entry_id);

  return dns;
}

/*
 * Curl_resolv() is the main name resolve function within libcurl. It resolves
 * a name and returns a pointer to the entry in the 'entry' argument (if one
 * is provided). This function might return immediately if we're using asynch
 * resolves. See the return codes.
 *
 * The cache entry we return will get its 'inuse' counter increased when this
 * function is used. You MUST call Curl_resolv_unlock() later (when you're
 * done using this struct) to decrease the counter again.
 *
 * Return codes:
 *
 * -1 = error, no pointer
 * 0 = OK, pointer provided
 * 1 = waiting for response, no pointer
 */
int Curl_resolv(struct connectdata *conn,
                char *hostname,
                int port,
                struct Curl_dns_entry **entry)
{
  char *entry_id = NULL;
  struct Curl_dns_entry *dns = NULL;
  size_t entry_len;
  int wait;
  struct SessionHandle *data = conn->data;
  CURLcode result;

  /* default to failure */
  int rc = -1;
  *entry = NULL;

#ifdef HAVE_SIGSETJMP
  /* this allows us to time-out from the name resolver, as the timeout
     will generate a signal and we will siglongjmp() from that here */
  if(!data->set.no_signal && sigsetjmp(curl_jmpenv, 1)) {
    /* this is coming from a siglongjmp() */
    failf(data, "name lookup timed out");
    return -1;
  }
#endif

  /* Create an entry id, based upon the hostname and port */
  entry_id = create_hostcache_id(hostname, port, &entry_len);
  /* If we can't create the entry id, fail */
  if (!entry_id)
    return -1;

  if(data->share)
    Curl_share_lock(data, CURL_LOCK_DATA_DNS, CURL_LOCK_ACCESS_SINGLE);

  /* See if its already in our dns cache */
  dns = Curl_hash_pick(data->hostcache, entry_id, entry_len+1);
  
  if(data->share)
    Curl_share_unlock(data, CURL_LOCK_DATA_DNS);

  /* free the allocated entry_id again */
  free(entry_id);

  if (!dns) {
    /* The entry was not in the cache. Resolve it to IP address */
      
    /* If my_getaddrinfo() returns NULL, 'wait' might be set to a non-zero
       value indicating that we need to wait for the response to the resolve
       call */
    Curl_addrinfo *addr = my_getaddrinfo(conn, hostname, port, &wait);
    
    if (!addr) {
      if(wait) {
        /* the response to our resolve call will come asynchronously at 
           a later time, good or bad */
        /* First, check that we haven't received the info by now */
        result = Curl_is_resolved(conn, &dns);
        if(result) /* error detected */
          return -1;
        if(dns)
          rc = 0; /* pointer provided */
        else
          rc = 1; /* no info yet */
      }
    }
    else {
      if(data->share)
        Curl_share_lock(data, CURL_LOCK_DATA_DNS, CURL_LOCK_ACCESS_SINGLE);

      /* we got a response, store it in the cache */
      dns = cache_resolv_response(data, addr, hostname, port);
      
      if(data->share)
        Curl_share_unlock(data, CURL_LOCK_DATA_DNS);

      if(!dns)
        /* returned failure, bail out nicely */
        Curl_freeaddrinfo(addr);
      else
        rc = 0;
    }
  }
  else {
    dns->inuse++; /* we use it! */
    rc = 0;
  }

  *entry = dns;

  return rc;
}

/*
 * Curl_resolv_unlock() unlocks the given cached DNS entry. When this has been
 * made, the struct may be destroyed due to pruning. It is important that only
 * one unlock is made for each Curl_resolv() call.
 */
void Curl_resolv_unlock(struct SessionHandle *data, struct Curl_dns_entry *dns)
{
  if(data->share)
    Curl_share_lock(data, CURL_LOCK_DATA_DNS, CURL_LOCK_ACCESS_SINGLE);

  dns->inuse--;

#ifdef CURLDEBUG
  if(dns->inuse < 0) {
    infof(data, "Interal host cache screw-up!");
    *(char **)0=NULL;
  }
#endif

  if(data->share)
    Curl_share_unlock(data, CURL_LOCK_DATA_DNS);
}

/*
 * This is a wrapper function for freeing name information in a protocol
 * independent way. This takes care of using the appropriate underlaying
 * function.
 */
void Curl_freeaddrinfo(Curl_addrinfo *p)
{
#ifdef ENABLE_IPV6
  freeaddrinfo(p);
#else
  free(p); /* works fine for the ARES case too */
#endif
}

/*
 * File-internal: free a cache dns entry.
 */
static void freednsentry(void *freethis)
{
  struct Curl_dns_entry *p = (struct Curl_dns_entry *) freethis;

  Curl_freeaddrinfo(p->addr);

  free(p);
}

/*
 * Curl_mk_dnscache() creates a new DNS cache and returns the handle for it.
 */
curl_hash *Curl_mk_dnscache(void)
{
  return Curl_hash_alloc(7, freednsentry);
}

/* --- resolve name or IP-number --- */

/* Allocate enough memory to hold the full name information structs and
 * everything. OSF1 is known to require at least 8872 bytes. The buffer
 * required for storing all possible aliases and IP numbers is according to
 * Stevens' Unix Network Programming 2nd edition, p. 304: 8192 bytes!
 */
#define CURL_NAMELOOKUP_SIZE 9000

#ifdef USE_ARES

/*
 * Curl_multi_ares_fdset() is called when someone from the outside world
 * (using curl_multi_fdset()) wants to get our fd_set setup and we're talking
 * with ares. The caller must make sure that this function is only called when
 * we have a working ares channel.
 *
 * Returns: CURLE_OK always!
 */

CURLcode Curl_multi_ares_fdset(struct connectdata *conn,
                               fd_set *read_fd_set,
                               fd_set *write_fd_set,
                               int *max_fdp)

{
  int max = ares_fds(conn->data->state.areschannel,
                     read_fd_set, write_fd_set);
  *max_fdp = max;

  return CURLE_OK;
}

/*
 * Curl_is_resolved() is called repeatedly to check if a previous name resolve
 * request has completed. It should also make sure to time-out if the
 * operation seems to take too long.
 *
 * Returns normal CURLcode errors.
 */
CURLcode Curl_is_resolved(struct connectdata *conn,
                          struct Curl_dns_entry **dns)
{
  fd_set read_fds, write_fds;
  struct timeval tv={0,0};
  int count;
  struct SessionHandle *data = conn->data;
  int nfds;

  FD_ZERO(&read_fds);
  FD_ZERO(&write_fds);

  nfds = ares_fds(data->state.areschannel, &read_fds, &write_fds);

  count = select(nfds, &read_fds, &write_fds, NULL,
                 (struct timeval *)&tv);

  /* Call ares_process() unconditonally here, even if we simply timed out
     above, as otherwise the ares name resolve won't timeout! */
  ares_process(data->state.areschannel, &read_fds, &write_fds);

  *dns = NULL;

  if(conn->async.done) {
    /* we're done, kill the ares handle */
    if(!conn->async.dns)
      return CURLE_COULDNT_RESOLVE_HOST;
    *dns = conn->async.dns;
  }

  return CURLE_OK;
}

/*
 * Curl_wait_for_resolv() waits for a resolve to finish. This function should
 * be avoided since using this risk getting the multi interface to "hang".
 *
 * If 'entry' is non-NULL, make it point to the resolved dns entry
 *
 * Returns CURLE_COULDNT_RESOLVE_HOST if the host was not resolved, and
 * CURLE_OPERATION_TIMEDOUT if a time-out occurred.
 */
CURLcode Curl_wait_for_resolv(struct connectdata *conn,
                              struct Curl_dns_entry **entry)
{
  CURLcode rc=CURLE_OK;
  struct SessionHandle *data = conn->data;
  long timeout = CURL_TIMEOUT_RESOLVE; /* default name resolve timeout */

  /* now, see if there's a connect timeout or a regular timeout to
     use instead of the default one */
  if(conn->data->set.connecttimeout)
    timeout = conn->data->set.connecttimeout;
  else if(conn->data->set.timeout)
    timeout = conn->data->set.timeout;

  /* We convert the number of seconds into number of milliseconds here: */
  if(timeout < 2147483)
    /* maximum amount of seconds that can be multiplied with 1000 and
       still fit within 31 bits */
    timeout *= 1000;
  else
    timeout = 0x7fffffff; /* ridiculous amount of time anyway */

  /* Wait for the name resolve query to complete. */
  while (1) {
    int nfds=0;
    fd_set read_fds, write_fds;
    struct timeval *tvp, tv, store;
    int count;
    struct timeval now = Curl_tvnow();
    long timediff;

    store.tv_sec = (int)timeout/1000;
    store.tv_usec = (timeout%1000)*1000;
    
    FD_ZERO(&read_fds);
    FD_ZERO(&write_fds);
    nfds = ares_fds(data->state.areschannel, &read_fds, &write_fds);
    if (nfds == 0)
      /* no file descriptors means we're done waiting */
      break;
    tvp = ares_timeout(data->state.areschannel, &store, &tv);
    count = select(nfds, &read_fds, &write_fds, NULL, tvp);
    if (count < 0 && errno != EINVAL)
      break;

    ares_process(data->state.areschannel, &read_fds, &write_fds);

    timediff = Curl_tvdiff(Curl_tvnow(), now); /* spent time */
    timeout -= timediff?timediff:1; /* always deduct at least 1 */
    if (timeout < 0) {
      /* our timeout, so we cancel the ares operation */
      ares_cancel(data->state.areschannel);
      break;
    }
  }

  /* Operation complete, if the lookup was successful we now have the entry
     in the cache. */
    
  if(entry)
    *entry = conn->async.dns;

  if(!conn->async.dns) {
    /* a name was not resolved */
    if((timeout < 0) || (conn->async.status == ARES_ETIMEOUT)) {
      failf(data, "Resolving host timed out: %s", conn->hostname);
      rc = CURLE_OPERATION_TIMEDOUT;
    }
    else if(conn->async.done) {
      failf(data, "Could not resolve host: %s (%s)", conn->hostname,
            ares_strerror(conn->async.status));
      rc = CURLE_COULDNT_RESOLVE_HOST;
    }
    else
      rc = CURLE_OPERATION_TIMEDOUT;

    /* close the connection, since we can't return failure here without
       cleaning up this connection properly */
    Curl_disconnect(conn);
  }
  
  return rc;
}
#endif

#if defined(USE_ARES) || defined(USE_THREADING_GETHOSTBYNAME)

/*
 * host_callback() gets called by ares/gethostbyname_thread() when we got the
 * name resolved (or not!).
 *
 * If the status argument is ARES_SUCCESS, we must copy the hostent field
 * since ares will free it when this function returns. This operation stores
 * the resolved data in the DNS cache.
 *
 * The storage operation locks and unlocks the DNS cache.
 */
static void host_callback(void *arg, /* "struct connectdata *" */
                          int status,
                          struct hostent *hostent)
{
  struct connectdata *conn = (struct connectdata *)arg;
  struct Curl_dns_entry *dns = NULL;

  conn->async.done = TRUE;
  conn->async.status = status;

  if(ARES_SUCCESS == status) {
    /* we got a resolved name in 'hostent' */
    char *bufp = (char *)malloc(CURL_NAMELOOKUP_SIZE);
    if(bufp) {

      /* pack_hostent() copies to and shrinks the target buffer */
      struct hostent *he = pack_hostent(&bufp, hostent);

      struct SessionHandle *data = conn->data;

      if(data->share)
        Curl_share_lock(data, CURL_LOCK_DATA_DNS, CURL_LOCK_ACCESS_SINGLE);

      dns = cache_resolv_response(data, he,
                                  conn->async.hostname, conn->async.port);

      if(data->share)
        Curl_share_unlock(data, CURL_LOCK_DATA_DNS);
    }
  }

  conn->async.dns = dns;

  /* The input hostent struct will be freed by ares when we return from this
     function */
}
#endif

#ifdef USE_ARES
/*
 * my_getaddrinfo() when using ares for name resolves.
 *
 * Returns name information about the given hostname and port number. If
 * successful, the 'hostent' is returned and the forth argument will point to
 * memory we need to free after use. That memory *MUST* be freed with
 * Curl_freeaddrinfo(), nothing else.
 */
static Curl_addrinfo *my_getaddrinfo(struct connectdata *conn,
                                     char *hostname,
                                     int port,
                                     int *waitp)
{
  char *bufp;
  struct SessionHandle *data = conn->data;

  *waitp = FALSE;
  
  if(data->set.ip_version == CURL_IPRESOLVE_V6)
    /* an ipv6 address was requested and we can't get/use one */
    return NULL;

  bufp = strdup(hostname);

  if(bufp) {
    Curl_safefree(conn->async.hostname);
    conn->async.hostname = bufp;
    conn->async.port = port;
    conn->async.done = FALSE; /* not done */
    conn->async.status = 0;   /* clear */
    conn->async.dns = NULL;   /* clear */

    /* areschannel is already setup in the Curl_open() function */
    ares_gethostbyname(data->state.areschannel, hostname, PF_INET,
                       host_callback, conn);
      
    *waitp = TRUE; /* please wait for the response */
  }
  return NULL; /* no struct yet */
}
#endif

#if !defined(USE_ARES) && !defined(USE_THREADING_GETHOSTBYNAME)

/*
 * Curl_wait_for_resolv() for builds without ARES and threaded gethostbyname,
 * Curl_resolv() can never return wait==TRUE, so this function will never be
 * called. If it still gets called, we return failure at once.
 *
 * We provide this function only to allow multi.c to remain unaware if we are
 * doing asynch resolves or not.
 */
CURLcode Curl_wait_for_resolv(struct connectdata *conn,
                              struct Curl_dns_entry **entry)
{
  (void)conn;
  *entry=NULL;
  return CURLE_COULDNT_RESOLVE_HOST;
}

/*
 * This function will never be called when built with ares or threaded
 * resolves. If it still gets called, we return failure at once.
 *
 * We provide this function only to allow multi.c to remain unaware if we are
 * doing asynch resolves or not.
 */
CURLcode Curl_is_resolved(struct connectdata *conn,
                          struct Curl_dns_entry **dns)
{
  (void)conn;
  *dns = NULL;

  return CURLE_COULDNT_RESOLVE_HOST;
}
#endif

#if !defined(USE_ARES)
/*
 * Non-ares build. If we are using threading gethostbyname, then this must
 * set the fd_set for the threaded resolve socket. If not, we just return OK.
 */
CURLcode Curl_multi_ares_fdset(struct connectdata *conn,
                               fd_set *read_fd_set,
                               fd_set *write_fd_set,
                               int *max_fdp)
{
#ifdef USE_THREADING_GETHOSTBYNAME
  const struct thread_data *td =
    (const struct thread_data *) conn->async.os_specific;

  if (td && td->dummy_sock != CURL_SOCKET_BAD) {
    FD_SET(td->dummy_sock,write_fd_set);
    *max_fdp = td->dummy_sock;
  }
#else /* if not USE_THREADING_GETHOSTBYNAME */
  (void)conn;
  (void)read_fd_set;
  (void)write_fd_set;
  (void)max_fdp;
#endif
  return CURLE_OK;
}
#endif /* !USE_ARES */

#if defined(ENABLE_IPV6) && !defined(USE_ARES)

#ifdef CURLDEBUG
/* These two are strictly for memory tracing and are using the same
 * style as the family otherwise present in memdebug.c. I put these ones
 * here since they require a bunch of struct types I didn't wanna include
 * in memdebug.c
 */
int curl_getaddrinfo(char *hostname, char *service,
                     struct addrinfo *hints,
                     struct addrinfo **result,
                     int line, const char *source)
{
  int res=(getaddrinfo)(hostname, service, hints, result);
  if(0 == res) {
    /* success */
    if(logfile)
      fprintf(logfile, "ADDR %s:%d getaddrinfo() = %p\n",
              source, line, (void *)*result);
  }
  else {
    if(logfile)
      fprintf(logfile, "ADDR %s:%d getaddrinfo() failed\n",
              source, line);
  }
  return res;
}

void curl_freeaddrinfo(struct addrinfo *freethis,
                       int line, const char *source)
{
  (freeaddrinfo)(freethis);
  if(logfile)
    fprintf(logfile, "ADDR %s:%d freeaddrinfo(%p)\n",
            source, line, (void *)freethis);
}

#endif

/*
 * my_getaddrinfo() when built ipv6-enabled.
 *
 * Returns name information about the given hostname and port number. If
 * successful, the 'addrinfo' is returned and the forth argument will point to
 * memory we need to free after use. That memory *MUST* be freed with
 * Curl_freeaddrinfo(), nothing else.
 */
static Curl_addrinfo *my_getaddrinfo(struct connectdata *conn,
                                     char *hostname,
                                     int port,
                                     int *waitp)
{
  struct addrinfo hints, *res;
  int error;
  char sbuf[NI_MAXSERV];
  int s, pf;
  struct SessionHandle *data = conn->data;

  *waitp=0; /* don't wait, we have the response now */

  /* see if we have an IPv6 stack */
  s = socket(PF_INET6, SOCK_DGRAM, 0);
  if (s < 0) {
    /* Some non-IPv6 stacks have been found to make very slow name resolves
     * when PF_UNSPEC is used, so thus we switch to a mere PF_INET lookup if
     * the stack seems to be a non-ipv6 one. */

    if(data->set.ip_version == CURL_IPRESOLVE_V6)
      /* an ipv6 address was requested and we can't get/use one */
      return NULL;

    pf = PF_INET;
  }
  else {
    /* This seems to be an IPv6-capable stack, use PF_UNSPEC for the widest
     * possible checks. And close the socket again.
     */
    sclose(s);

    /*
     * Check if a more limited name resolve has been requested.
     */
    switch(data->set.ip_version) {
    case CURL_IPRESOLVE_V4:
      pf = PF_INET;
      break;
    case CURL_IPRESOLVE_V6:
      pf = PF_INET6;
      break;
    default:
      pf = PF_UNSPEC;
      break;
    }
  }
 
  memset(&hints, 0, sizeof(hints));
  hints.ai_family = pf;
  hints.ai_socktype = SOCK_STREAM;
  hints.ai_flags = AI_CANONNAME;
  snprintf(sbuf, sizeof(sbuf), "%d", port);
  error = getaddrinfo(hostname, sbuf, &hints, &res);
  if (error) {
    infof(data, "getaddrinfo(3) failed for %s:%d\n", hostname, port);    
    return NULL;
  }

  return res;
}
#else /* following code is IPv4-only */

#if !defined(HAVE_GETHOSTBYNAME_R) || defined(USE_ARES) || \
    defined(USE_THREADING_GETHOSTBYNAME)
static void hostcache_fixoffset(struct hostent *h, long offset);

/*
 * pack_hostent() is a file-local function that performs a "deep" copy of a
 * hostent into a buffer (returns a pointer to the copy). Make absolutely sure
 * the destination buffer is big enough!
 */
static struct hostent* pack_hostent(char** buf, struct hostent* orig)
{
  char *bufptr;
  char *newbuf;
  struct hostent* copy;

  int i;
  char *str;
  size_t len;

  bufptr = *buf;
  copy = (struct hostent*)bufptr;

  bufptr += sizeof(struct hostent);
  copy->h_name = bufptr;
  len = strlen(orig->h_name) + 1;
  strncpy(bufptr, orig->h_name, len);
  bufptr += len;

  /* we align on even 64bit boundaries for safety */
#define MEMALIGN(x) ((x)+(8-(((unsigned long)(x))&0x7)))

  /* This must be aligned properly to work on many CPU architectures! */
  bufptr = MEMALIGN(bufptr);
  
  copy->h_aliases = (char**)bufptr;

  /* Figure out how many aliases there are */
  for (i = 0; orig->h_aliases && orig->h_aliases[i]; ++i);

  /* Reserve room for the array */