Adding upstream version 1.20.1.upstream/1.20.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1079 insertions, 0 deletions

diff --git a/src/host.c b/src/host.c
new file mode 100644
index 0000000..2bf848f
--- /dev/null
+++ b/src/host.c
@@ -0,0 +1,1079 @@
+/* Host name resolution and matching.
+   Copyright (C) 1996-2012, 2015, 2018 Free Software Foundation, Inc.
+
+This file is part of GNU Wget.
+
+GNU Wget is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+GNU Wget is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with Wget.  If not, see <http://www.gnu.org/licenses/>.
+
+Additional permission under GNU GPL version 3 section 7
+
+If you modify this program, or any covered work, by linking or
+combining it with the OpenSSL project's OpenSSL library (or a
+modified version of that library), containing parts covered by the
+terms of the OpenSSL or SSLeay licenses, the Free Software Foundation
+grants you additional permission to convey the resulting work.
+Corresponding Source for a non-source form of such a combination
+shall include the source code for the parts of OpenSSL used as well
+as that of the covered work.  */
+
+#include "wget.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+#ifndef WINDOWS
+# include <sys/types.h>
+# include <sys/socket.h>
+# include <netinet/in.h>
+# ifndef __BEOS__
+#  include <arpa/inet.h>
+# endif
+# ifdef __VMS
+#  include "vms_ip.h"
+# else /* def __VMS */
+#  include <netdb.h>
+# endif /* def __VMS [else] */
+# define SET_H_ERRNO(err) ((void)(h_errno = (err)))
+#else  /* WINDOWS */
+# include <winsock2.h>
+# include <ws2tcpip.h>
+# define SET_H_ERRNO(err) WSASetLastError (err)
+#endif /* WINDOWS */
+
+#include <errno.h>
+
+#include "utils.h"
+#include "host.h"
+#include "url.h"
+#include "hash.h"
+#include "ptimer.h"
+
+#ifndef NO_ADDRESS
+# define NO_ADDRESS NO_DATA
+#endif
+
+#if !HAVE_DECL_H_ERRNO && !defined(WINDOWS)
+extern int h_errno;
+#endif
+
+
+/* Lists of IP addresses that result from running DNS queries.  See
+   lookup_host for details.  */
+
+struct address_list {
+  int count;                    /* number of adrresses */
+  ip_address *addresses;        /* pointer to the string of addresses */
+
+  int faulty;                   /* number of addresses known not to work. */
+  bool connected;               /* whether we were able to connect to
+                                   one of the addresses in the list,
+                                   at least once. */
+
+  int refcount;                 /* reference count; when it drops to
+                                   0, the entry is freed. */
+};
+
+/* Get the bounds of the address list.  */
+
+void
+address_list_get_bounds (const struct address_list *al, int *start, int *end)
+{
+  *start = al->faulty;
+  *end   = al->count;
+}
+
+/* Return a pointer to the address at position POS.  */
+
+const ip_address *
+address_list_address_at (const struct address_list *al, int pos)
+{
+  assert (pos >= al->faulty && pos < al->count);
+  return al->addresses + pos;
+}
+
+/* Return true if AL contains IP, false otherwise.  */
+
+bool
+address_list_contains (const struct address_list *al, const ip_address *ip)
+{
+  int i;
+  switch (ip->family)
+    {
+    case AF_INET:
+      for (i = 0; i < al->count; i++)
+        {
+          ip_address *cur = al->addresses + i;
+          if (cur->family == AF_INET
+              && (cur->data.d4.s_addr == ip->data.d4.s_addr))
+            return true;
+        }
+      return false;
+#ifdef ENABLE_IPV6
+    case AF_INET6:
+      for (i = 0; i < al->count; i++)
+        {
+          ip_address *cur = al->addresses + i;
+          if (cur->family == AF_INET6
+#ifdef HAVE_SOCKADDR_IN6_SCOPE_ID
+              && cur->ipv6_scope == ip->ipv6_scope
+#endif
+              && IN6_ARE_ADDR_EQUAL (&cur->data.d6, &ip->data.d6))
+            return true;
+        }
+      return false;
+#endif /* ENABLE_IPV6 */
+    default:
+      abort ();
+    }
+}
+
+/* Mark the INDEXth element of AL as faulty, so that the next time
+   this address list is used, the faulty element will be skipped.  */
+
+void
+address_list_set_faulty (struct address_list *al, int index)
+{
+  /* We assume that the address list is traversed in order, so that a
+     "faulty" attempt is always preceded with all-faulty addresses,
+     and this is how Wget uses it.  */
+  assert (index == al->faulty);
+  if (index != al->faulty)
+    {
+      logprintf (LOG_ALWAYS, "index: %d\nal->faulty: %d\n", index, al->faulty);
+      logprintf (LOG_ALWAYS, _("Error in handling the address list.\n"));
+      logprintf (LOG_ALWAYS, _("Please report this issue to bug-wget@gnu.org\n"));
+      abort();
+    }
+
+  ++al->faulty;
+  if (al->faulty >= al->count)
+    /* All addresses have been proven faulty.  Since there's not much
+       sense in returning the user an empty address list the next
+       time, we'll rather make them all clean, so that they can be
+       retried anew.  */
+    al->faulty = 0;
+}
+
+/* Set the "connected" flag to true.  This flag used by connect.c to
+   see if the host perhaps needs to be resolved again.  */
+
+void
+address_list_set_connected (struct address_list *al)
+{
+  al->connected = true;
+}
+
+/* Return the value of the "connected" flag. */
+
+bool
+address_list_connected_p (const struct address_list *al)
+{
+  return al->connected;
+}
+
+#ifdef ENABLE_IPV6
+
+/* Create an address_list from the addresses in the given struct
+   addrinfo.  */
+
+static struct address_list *
+address_list_from_addrinfo (const struct addrinfo *ai)
+{
+  struct address_list *al;
+  const struct addrinfo *ptr;
+  int cnt;
+  ip_address *ip;
+
+  cnt = 0;
+  for (ptr = ai; ptr != NULL ; ptr = ptr->ai_next)
+    if (ptr->ai_family == AF_INET || ptr->ai_family == AF_INET6)
+      ++cnt;
+  if (cnt == 0)
+    return NULL;
+
+  al = xnew0 (struct address_list);
+  al->addresses = xnew_array (ip_address, cnt);
+  al->count     = cnt;
+  al->refcount  = 1;
+
+  ip = al->addresses;
+  for (ptr = ai; ptr != NULL; ptr = ptr->ai_next)
+    if (ptr->ai_family == AF_INET6)
+      {
+        const struct sockaddr_in6 *sin6 =
+          (const struct sockaddr_in6 *)ptr->ai_addr;
+        ip->family = AF_INET6;
+        ip->data.d6 = sin6->sin6_addr;
+#ifdef HAVE_SOCKADDR_IN6_SCOPE_ID
+        ip->ipv6_scope = sin6->sin6_scope_id;
+#endif
+        ++ip;
+      }
+    else if (ptr->ai_family == AF_INET)
+      {
+        const struct sockaddr_in *sin =
+          (const struct sockaddr_in *)ptr->ai_addr;
+        ip->family = AF_INET;
+        ip->data.d4 = sin->sin_addr;
+        ++ip;
+      }
+  assert (ip - al->addresses == cnt);
+  return al;
+}
+
+#define IS_IPV4(addr) (((const ip_address *) addr)->family == AF_INET)
+
+/* Compare two IP addresses by family, giving preference to the IPv4
+   address (sorting it first).  In other words, return -1 if ADDR1 is
+   IPv4 and ADDR2 is IPv6, +1 if ADDR1 is IPv6 and ADDR2 is IPv4, and
+   0 otherwise.
+
+   This is intended to be used as the comparator arg to a qsort-like
+   sorting function, which is why it accepts generic pointers.  */
+
+static int
+cmp_prefer_ipv4 (const void *addr1, const void *addr2)
+{
+  return !IS_IPV4 (addr1) - !IS_IPV4 (addr2);
+}
+
+#define IS_IPV6(addr) (((const ip_address *) addr)->family == AF_INET6)
+
+/* Like the above, but give preference to the IPv6 address.  */
+
+static int
+cmp_prefer_ipv6 (const void *addr1, const void *addr2)
+{
+  return !IS_IPV6 (addr1) - !IS_IPV6 (addr2);
+}
+
+#else  /* not ENABLE_IPV6 */
+
+/* Create an address_list from a NULL-terminated vector of IPv4
+   addresses.  This kind of vector is returned by gethostbyname.  */
+
+static struct address_list *
+address_list_from_ipv4_addresses (char **vec)
+{
+  int count, i;
+  struct address_list *al = xnew0 (struct address_list);
+
+  count = 0;
+  while (vec[count])
+    ++count;
+  assert (count > 0);
+
+  al->addresses = xnew_array (ip_address, count);
+  al->count     = count;
+  al->refcount  = 1;
+
+  for (i = 0; i < count; i++)
+    {
+      ip_address *ip = &al->addresses[i];
+      ip->family = AF_INET;
+      memcpy (IP_INADDR_DATA (ip), vec[i], 4);
+    }
+
+  return al;
+}
+
+#endif /* not ENABLE_IPV6 */
+
+static void
+address_list_delete (struct address_list *al)
+{
+  xfree (al->addresses);
+  xfree (al);
+}
+
+/* Mark the address list as being no longer in use.  This will reduce
+   its reference count which will cause the list to be freed when the
+   count reaches 0.  */
+
+void
+address_list_release (struct address_list *al)
+{
+  --al->refcount;
+  DEBUGP (("Releasing 0x%0*lx (new refcount %d).\n", PTR_FORMAT (al),
+           al->refcount));
+  if (al->refcount <= 0)
+    {
+      DEBUGP (("Deleting unused 0x%0*lx.\n", PTR_FORMAT (al)));
+      address_list_delete (al);
+    }
+}
+
+/* Versions of gethostbyname and getaddrinfo that support timeout. */
+
+#ifndef ENABLE_IPV6
+
+struct ghbnwt_context {
+  const char *host_name;
+  struct hostent *hptr;
+};
+
+static void
+gethostbyname_with_timeout_callback (void *arg)
+{
+  struct ghbnwt_context *ctx = (struct ghbnwt_context *)arg;
+  ctx->hptr = gethostbyname (ctx->host_name);
+}
+
+/* Just like gethostbyname, except it times out after TIMEOUT seconds.
+   In case of timeout, NULL is returned and errno is set to ETIMEDOUT.
+   The function makes sure that when NULL is returned for reasons
+   other than timeout, errno is reset.  */
+
+static struct hostent *
+gethostbyname_with_timeout (const char *host_name, double timeout)
+{
+  struct ghbnwt_context ctx;
+  ctx.host_name = host_name;
+  if (run_with_timeout (timeout, gethostbyname_with_timeout_callback, &ctx))
+    {
+      SET_H_ERRNO (HOST_NOT_FOUND);
+      errno = ETIMEDOUT;
+      return NULL;
+    }
+  if (!ctx.hptr)
+    errno = 0;
+  return ctx.hptr;
+}
+
+/* Print error messages for host errors.  */
+static const char *
+host_errstr (int error)
+{
+  /* Can't use switch since some of these constants can be equal,
+     which makes the compiler complain about duplicate case
+     values.  */
+  if (error == HOST_NOT_FOUND
+      || error == NO_RECOVERY
+      || error == NO_DATA
+      || error == NO_ADDRESS)
+    return _("Unknown host");
+  else if (error == TRY_AGAIN)
+    /* Message modeled after what gai_strerror returns in similar
+       circumstances.  */
+    return _("Temporary failure in name resolution");
+  else
+    return _("Unknown error");
+}
+
+#else  /* ENABLE_IPV6 */
+
+struct gaiwt_context {
+  const char *node;
+  const char *service;
+  const struct addrinfo *hints;
+  struct addrinfo **res;
+  int exit_code;
+};
+
+static void
+getaddrinfo_with_timeout_callback (void *arg)
+{
+  struct gaiwt_context *ctx = (struct gaiwt_context *)arg;
+  ctx->exit_code = getaddrinfo (ctx->node, ctx->service, ctx->hints, ctx->res);
+}
+
+/* Just like getaddrinfo, except it times out after TIMEOUT seconds.
+   In case of timeout, the EAI_SYSTEM error code is returned and errno
+   is set to ETIMEDOUT.  */
+
+static int
+getaddrinfo_with_timeout (const char *node, const char *service,
+                          const struct addrinfo *hints, struct addrinfo **res,
+                          double timeout)
+{
+  struct gaiwt_context ctx;
+  ctx.node = node;
+  ctx.service = service;
+  ctx.hints = hints;
+  ctx.res = res;
+
+  if (run_with_timeout (timeout, getaddrinfo_with_timeout_callback, &ctx))
+    {
+      errno = ETIMEDOUT;
+      return EAI_SYSTEM;
+    }
+  return ctx.exit_code;
+}
+
+#endif /* ENABLE_IPV6 */
+
+/* Return a textual representation of ADDR, i.e. the dotted quad for
+   IPv4 addresses, and the colon-separated list of hex words (with all
+   zeros omitted, etc.) for IPv6 addresses.  */
+
+const char *
+print_address (const ip_address *addr)
+{
+  static char buf[64];
+
+  if (!inet_ntop (addr->family, IP_INADDR_DATA (addr), buf, sizeof buf))
+    snprintf (buf, sizeof buf, "<error: %s>", strerror (errno));
+
+  return buf;
+}
+
+/* The following two functions were adapted from glibc's
+   implementation of inet_pton, written by Paul Vixie. */
+
+static bool
+is_valid_ipv4_address (const char *str, const char *end)
+{
+  bool saw_digit = false;
+  int octets = 0;
+  int val = 0;
+
+  while (str < end)
+    {
+      int ch = *str++;
+
+      if (ch >= '0' && ch <= '9')
+        {
+          val = val * 10 + (ch - '0');
+
+          if (val > 255)
+            return false;
+          if (!saw_digit)
+            {
+              if (++octets > 4)
+                return false;
+              saw_digit = true;
+            }
+        }
+      else if (ch == '.' && saw_digit)
+        {
+          if (octets == 4)
+            return false;
+          val = 0;
+          saw_digit = false;
+        }
+      else
+        return false;
+    }
+  if (octets < 4)
+    return false;
+
+  return true;
+}
+
+bool
+is_valid_ipv6_address (const char *str, const char *end)
+{
+  /* Use lower-case for these to avoid clash with system headers.  */
+  enum {
+    ns_inaddrsz  = 4,
+    ns_in6addrsz = 16,
+    ns_int16sz   = 2
+  };
+
+  const char *curtok;
+  int tp;
+  const char *colonp;
+  bool saw_xdigit;
+  unsigned int val;
+
+  tp = 0;
+  colonp = NULL;
+
+  if (str == end)
+    return false;
+
+  /* Leading :: requires some special handling. */
+  if (*str == ':')
+    {
+      ++str;
+      if (str == end || *str != ':')
+        return false;
+    }
+
+  curtok = str;
+  saw_xdigit = false;
+  val = 0;
+
+  while (str < end)
+    {
+      int ch = *str++;
+
+      /* if ch is a number, add it to val. */
+      if (c_isxdigit (ch))
+        {
+          val <<= 4;
+          val |= XDIGIT_TO_NUM (ch);
+          if (val > 0xffff)
+            return false;
+          saw_xdigit = true;
+          continue;
+        }
+
+      /* if ch is a colon ... */
+      if (ch == ':')
+        {
+          curtok = str;
+          if (!saw_xdigit)
+            {
+              if (colonp != NULL)
+                return false;
+              colonp = str + tp;
+              continue;
+            }
+          else if (str == end)
+            return false;
+          if (tp > ns_in6addrsz - ns_int16sz)
+            return false;
+          tp += ns_int16sz;
+          saw_xdigit = false;
+          val = 0;
+          continue;
+        }
+
+      /* if ch is a dot ... */
+      if (ch == '.' && (tp <= ns_in6addrsz - ns_inaddrsz)
+          && is_valid_ipv4_address (curtok, end) == 1)
+        {
+          tp += ns_inaddrsz;
+          saw_xdigit = false;
+          break;
+        }
+
+      return false;
+    }
+
+  if (saw_xdigit)
+    {
+      if (tp > ns_in6addrsz - ns_int16sz)
+        return false;
+      tp += ns_int16sz;
+    }
+
+  if (colonp != NULL)
+    {
+      if (tp == ns_in6addrsz)
+        return false;
+      tp = ns_in6addrsz;
+    }
+
+  if (tp != ns_in6addrsz)
+    return false;
+
+  return true;
+}
+
+/* Simple host cache, used by lookup_host to speed up resolving.  The
+   cache doesn't handle TTL because Wget is a fairly short-lived
+   application.  Refreshing is attempted when connect fails, though --
+   see connect_to_host.  */
+
+/* Mapping between known hosts and to lists of their addresses. */
+static struct hash_table *host_name_addresses_map;
+
+
+/* Return the host's resolved addresses from the cache, if
+   available.  */
+
+static struct address_list *
+cache_query (const char *host)
+{
+  struct address_list *al;
+  if (!host_name_addresses_map)
+    return NULL;
+  al = hash_table_get (host_name_addresses_map, host);
+  if (al)
+    {
+      DEBUGP (("Found %s in host_name_addresses_map (%p)\n", host, (void *) al));
+      ++al->refcount;
+      return al;
+    }
+  return NULL;
+}
+
+/* Cache the DNS lookup of HOST.  Subsequent invocations of
+   lookup_host will return the cached value.  */
+
+static void
+cache_store (const char *host, struct address_list *al)
+{
+  if (!host_name_addresses_map)
+    host_name_addresses_map = make_nocase_string_hash_table (0);
+
+  ++al->refcount;
+  hash_table_put (host_name_addresses_map, xstrdup_lower (host), al);
+
+  IF_DEBUG
+    {
+      int i;
+      debug_logprintf ("Caching %s =>", host);
+      for (i = 0; i < al->count; i++)
+        debug_logprintf (" %s", print_address (al->addresses + i));
+      debug_logprintf ("\n");
+    }
+}
+
+/* Remove HOST from the DNS cache.  Does nothing is HOST is not in
+   the cache.  */
+
+static void
+cache_remove (const char *host)
+{
+  struct address_list *al;
+  if (!host_name_addresses_map)
+    return;
+  al = hash_table_get (host_name_addresses_map, host);
+  if (al)
+    {
+      address_list_release (al);
+      hash_table_remove (host_name_addresses_map, host);
+    }
+}
+
+#ifdef HAVE_LIBCARES
+#include <sys/select.h>
+#include <ares.h>
+extern ares_channel ares;
+
+static struct address_list *
+merge_address_lists (struct address_list *al1, struct address_list *al2)
+{
+  int count = al1->count + al2->count;
+
+  /* merge al2 into al1 */
+  al1->addresses = xrealloc (al1->addresses, sizeof (ip_address) * count);
+  memcpy (al1->addresses + al1->count, al2->addresses, sizeof (ip_address) * al2->count);
+  al1->count = count;
+
+  address_list_delete (al2);
+
+  return al1;
+}
+
+static struct address_list *
+address_list_from_hostent (struct hostent *host)
+{
+  int count, i;
+  struct address_list *al = xnew0 (struct address_list);
+
+  for (count = 0; host->h_addr_list[count]; count++)
+    ;
+
+  assert (count > 0);
+
+  al->addresses = xnew_array (ip_address, count);
+  al->count     = count;
+  al->refcount  = 1;
+
+  for (i = 0; i < count; i++)
+    {
+      ip_address *ip = &al->addresses[i];
+      ip->family = host->h_addrtype;
+      memcpy (IP_INADDR_DATA (ip), host->h_addr_list[i], ip->family == AF_INET ? 4 : 16);
+    }
+
+  return al;
+}
+
+/* Since GnuLib's select() (i.e. rpl_select()) cannot handle socket-numbers
+ * returned from C-ares, we must use the original select() from Winsock.
+ */
+#ifdef WINDOWS
+#undef select
+#endif
+
+static void
+wait_ares (ares_channel channel)
+{
+  struct ptimer *timer = NULL;
+
+  if (opt.dns_timeout)
+    timer = ptimer_new ();
+
+  for (;;)
+    {
+      struct timeval *tvp, tv;
+      fd_set read_fds, write_fds;
+      int nfds, rc;
+
+      FD_ZERO (&read_fds);
+      FD_ZERO (&write_fds);
+      nfds = ares_fds (channel, &read_fds, &write_fds);
+      if (nfds == 0)
+        break;
+
+      if (timer)
+        {
+          double max = opt.dns_timeout - ptimer_measure (timer);
+
+          tv.tv_sec = (long) max;
+          tv.tv_usec = 1000000 * (max - (long) max);
+          tvp = ares_timeout (channel, &tv, &tv);
+        }
+      else
+        tvp = ares_timeout (channel, NULL, &tv);
+
+      rc = select (nfds, &read_fds, &write_fds, NULL, tvp);
+      if (rc == 0 && timer && ptimer_measure (timer) >= opt.dns_timeout)
+        ares_cancel (channel);
+      else
+        ares_process (channel, &read_fds, &write_fds);
+    }
+  if (timer)
+    ptimer_destroy (timer);
+}
+
+static void
+callback (void *arg, int status, int timeouts _GL_UNUSED, struct hostent *host)
+{
+  struct address_list **al = (struct address_list **) arg;
+
+  if (!host || status != ARES_SUCCESS)
+    {
+      *al = NULL;
+      return;
+    }
+
+  *al = address_list_from_hostent (host);
+}
+#endif
+
+/* Look up HOST in DNS and return a list of IP addresses.
+
+   This function caches its result so that, if the same host is passed
+   the second time, the addresses are returned without DNS lookup.
+   (Use LH_REFRESH to force lookup, or set opt.dns_cache to 0 to
+   globally disable caching.)
+
+   The order of the returned addresses is affected by the setting of
+   opt.prefer_family: if it is set to prefer_ipv4, IPv4 addresses are
+   placed at the beginning; if it is prefer_ipv6, IPv6 ones are placed
+   at the beginning; otherwise, the order is left intact.  The
+   relative order of addresses with the same family is left
+   undisturbed in either case.
+
+   FLAGS can be a combination of:
+     LH_SILENT  - don't print the "resolving ... done" messages.
+     LH_BIND    - resolve addresses for use with bind, which under
+                  IPv6 means to use AI_PASSIVE flag to getaddrinfo.
+                  Passive lookups are not cached under IPv6.
+     LH_REFRESH - if HOST is cached, remove the entry from the cache
+                  and resolve it anew.  */
+
+struct address_list *
+lookup_host (const char *host, int flags)
+{
+  struct address_list *al;
+  bool silent = !!(flags & LH_SILENT);
+  bool use_cache;
+  bool numeric_address = false;
+  double timeout = opt.dns_timeout;
+
+#ifndef ENABLE_IPV6
+  /* If we're not using getaddrinfo, first check if HOST specifies a
+     numeric IPv4 address.  Some implementations of gethostbyname
+     (e.g. the Ultrix one and possibly Winsock) don't accept
+     dotted-decimal IPv4 addresses.  */
+  {
+    uint32_t addr_ipv4 = (uint32_t)inet_addr (host);
+    if (addr_ipv4 != (uint32_t) -1)
+      {
+        /* No need to cache host->addr relation, just return the
+           address.  */
+        char *vec[2];
+        vec[0] = (char *)&addr_ipv4;
+        vec[1] = NULL;
+        return address_list_from_ipv4_addresses (vec);
+      }
+  }
+#else  /* ENABLE_IPV6 */
+  /* If we're using getaddrinfo, at least check whether the address is
+     already numeric, in which case there is no need to print the
+     "Resolving..." output.  (This comes at no additional cost since
+     the is_valid_ipv*_address are already required for
+     url_parse.)  */
+  {
+    const char *end = host + strlen (host);
+    if (is_valid_ipv4_address (host, end) || is_valid_ipv6_address (host, end))
+      numeric_address = true;
+  }
+#endif
+
+  /* Cache is normally on, but can be turned off with --no-dns-cache.
+     Don't cache passive lookups under IPv6.  */
+  use_cache = opt.dns_cache;
+#ifdef ENABLE_IPV6
+  if ((flags & LH_BIND) || numeric_address)
+    use_cache = false;
+#endif
+
+  /* Try to find the host in the cache so we don't need to talk to the
+     resolver.  If LH_REFRESH is requested, remove HOST from the cache
+     instead.  */
+  if (use_cache)
+    {
+      if (!(flags & LH_REFRESH))
+        {
+          al = cache_query (host);
+          if (al)
+            return al;
+        }
+      else
+        cache_remove (host);
+    }
+
+  /* No luck with the cache; resolve HOST. */
+
+  if (!silent && !numeric_address)
+    {
+      char *str = NULL, *name;
+
+      if (opt.enable_iri && (name = idn_decode ((char *) host)) != NULL)
+        {
+          str = aprintf ("%s (%s)", name, host);
+          xfree (name);
+        }
+
+      logprintf (LOG_VERBOSE, _("Resolving %s... "),
+                 quotearg_style (escape_quoting_style, str ? str : host));
+
+      xfree (str);
+    }
+
+#ifdef ENABLE_IPV6
+#ifdef HAVE_LIBCARES
+  if (ares)
+    {
+      struct address_list *al4;
+      struct address_list *al6;
+
+      if (opt.ipv4_only || !opt.ipv6_only)
+        ares_gethostbyname (ares, host, AF_INET, callback, &al4);
+      if (opt.ipv6_only || !opt.ipv4_only)
+        ares_gethostbyname (ares, host, AF_INET6, callback, &al6);
+
+      wait_ares (ares);
+
+      if (al4 && al6)
+        al = merge_address_lists (al4, al6);
+      else if (al4)
+        al = al4;
+      else
+        al = al6;
+    }
+  else
+#endif
+    {
+      int err;
+      struct addrinfo hints, *res;
+
+      xzero (hints);
+      hints.ai_socktype = SOCK_STREAM;
+      if (opt.ipv4_only)
+        hints.ai_family = AF_INET;
+      else if (opt.ipv6_only)
+        hints.ai_family = AF_INET6;
+      else
+        /* We tried using AI_ADDRCONFIG, but removed it because: it
+           misinterprets IPv6 loopbacks, it is broken on AIX 5.1, and
+           it's unneeded since we sort the addresses anyway.  */
+        hints.ai_family = AF_UNSPEC;
+
+      if (flags & LH_BIND)
+        hints.ai_flags |= AI_PASSIVE;
+
+#ifdef AI_NUMERICHOST
+      if (numeric_address)
+        {
+          /* Where available, the AI_NUMERICHOST hint can prevent costly
+             access to DNS servers.  */
+          hints.ai_flags |= AI_NUMERICHOST;
+          timeout = 0; /* no timeout needed when "resolving"
+                                   numeric hosts -- avoid setting up
+                                   signal handlers and such. */
+        }
+#endif
+
+      err = getaddrinfo_with_timeout (host, NULL, &hints, &res, timeout);
+
+      if (err != 0 || res == NULL)
+        {
+          if (!silent)
+            logprintf (LOG_VERBOSE, _ ("failed: %s.\n"),
+                       err != EAI_SYSTEM ? gai_strerror (err) : strerror (errno));
+          return NULL;
+        }
+      al = address_list_from_addrinfo (res);
+      freeaddrinfo (res);
+    }
+
+  if (!al)
+    {
+      logprintf (LOG_VERBOSE,
+                 _ ("failed: No IPv4/IPv6 addresses for host.\n"));
+      return NULL;
+    }
+
+  /* Reorder addresses so that IPv4 ones (or IPv6 ones, as per
+     --prefer-family) come first.  Sorting is stable so the order of
+     the addresses with the same family is undisturbed.  */
+  if (al->count > 1 && opt.prefer_family != prefer_none)
+    stable_sort (al->addresses, al->count, sizeof (ip_address),
+                 opt.prefer_family == prefer_ipv4
+                 ? cmp_prefer_ipv4 : cmp_prefer_ipv6);
+#else  /* not ENABLE_IPV6 */
+#ifdef HAVE_LIBCARES
+  if (ares)
+    {
+      ares_gethostbyname (ares, host, AF_INET, callback, &al);
+      wait_ares (ares);
+    }
+  else
+#endif
+    {
+      struct hostent *hptr = gethostbyname_with_timeout (host, timeout);
+      if (!hptr)
+        {
+          if (!silent)
+            {
+              if (errno != ETIMEDOUT)
+                logprintf (LOG_VERBOSE, _ ("failed: %s.\n"),
+                           host_errstr (h_errno));
+              else
+                logputs (LOG_VERBOSE, _ ("failed: timed out.\n"));
+            }
+          return NULL;
+        }
+      /* Do older systems have h_addr_list?  */
+      al = address_list_from_ipv4_addresses (hptr->h_addr_list);
+    }
+#endif /* not ENABLE_IPV6 */
+
+  /* Print the addresses determined by DNS lookup, but no more than
+     three if show_all_dns_entries is not specified.  */
+  if (!silent && !numeric_address)
+    {
+      int i;
+      int printmax = al->count;
+
+      if (!opt.show_all_dns_entries && printmax > 3)
+          printmax = 3;
+
+      for (i = 0; i < printmax; i++)
+        {
+          logputs (LOG_VERBOSE, print_address (al->addresses + i));
+          if (i < printmax - 1)
+            logputs (LOG_VERBOSE, ", ");
+        }
+      if (printmax != al->count)
+        logputs (LOG_VERBOSE, ", ...");
+      logputs (LOG_VERBOSE, "\n");
+    }
+
+  /* Cache the lookup information. */
+  if (use_cache)
+    cache_store (host, al);
+
+  return al;
+}
+
+/* Determine whether a URL is acceptable to be followed, according to
+   a list of domains to accept.  */
+bool
+accept_domain (struct url *u)
+{
+  assert (u->host != NULL);
+  if (opt.domains)
+    {
+      if (!sufmatch ((const char **)opt.domains, u->host))
+        return false;
+    }
+  if (opt.exclude_domains)
+    {
+      if (sufmatch ((const char **)opt.exclude_domains, u->host))
+        return false;
+    }
+  return true;
+}
+
+/* Check whether WHAT is matched in LIST, each element of LIST being a
+   pattern to match WHAT against, using backward matching (see
+   match_backwards() in utils.c).
+
+   If an element of LIST matched, 1 is returned, 0 otherwise.  */
+bool
+sufmatch (const char **list, const char *what)
+{
+  int i, j, k, lw;
+
+  lw = strlen (what);
+
+  for (i = 0; list[i]; i++)
+    {
+      j = strlen (list[i]);
+      if (lw < j)
+        continue; /* what is no (sub)domain of list[i] */
+
+      for (k = lw; j >= 0 && k >= 0; j--, k--)
+        if (c_tolower (list[i][j]) != c_tolower (what[k]))
+          break;
+
+      /* Domain or subdomain match
+       * k == -1: exact match
+       * k >= 0 && what[k] == '.': subdomain match
+       * k >= 0 && list[i][0] == '.': dot-prefixed subdomain match
+       */
+      if (j == -1 && (k == -1 || what[k] == '.' || list[i][0] == '.'))
+        return true;
+    }
+
+  return false;
+}
+
+void
+host_cleanup (void)
+{
+  if (host_name_addresses_map)
+    {
+      hash_table_iterator iter;
+      for (hash_table_iterate (host_name_addresses_map, &iter);
+           hash_table_iter_next (&iter);
+           )
+        {
+          char *host = iter.key;
+          struct address_list *al = iter.value;
+          xfree (host);
+          assert (al->refcount == 1);
+          address_list_delete (al);
+        }
+      hash_table_destroy (host_name_addresses_map);
+      host_name_addresses_map = NULL;
+    }
+}
+
+bool
+is_valid_ip_address (const char *name)
+{
+  const char *endp;
+
+  endp = name + strlen(name);
+  if (is_valid_ipv4_address (name, endp))
+    return true;
+#ifdef ENABLE_IPV6
+  if (is_valid_ipv6_address (name, endp))
+    return true;
+#endif
+  return false;
+}