Adding upstream version 1:10.5.12.upstream/1%10.5.12upstream

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

1 files changed, 979 insertions, 0 deletions

diff --git a/sql/hostname.cc b/sql/hostname.cc
new file mode 100644
index 00000000..edf31c11
--- /dev/null
+++ b/sql/hostname.cc
@@ -0,0 +1,979 @@
+/* Copyright (c) 2000, 2013, Oracle and/or its affiliates.
+   Copyright (c) 2011, 2014, SkySQL Ab.
+
+   This program 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; version 2 of the License.
+
+   This program 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 this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1335  USA */
+
+
+/**
+  @file
+
+  @brief
+  Get hostname for an IP address.
+
+  Hostnames are checked with reverse name lookup and checked that they
+  doesn't resemble an IP address.
+*/
+#include "mariadb.h"
+#include "sql_priv.h"
+#include "unireg.h"                             // SPECIAL_NO_HOST_CACHE
+#include "hostname.h"
+#ifndef __WIN__
+#include <netdb.h>        // getservbyname, servent
+#endif
+#include "hash_filo.h"
+#include <m_ctype.h>
+#include "log.h"                                // sql_print_warning,
+                                                // sql_print_information
+#include "violite.h"                            // vio_getnameinfo,
+                                                // vio_get_normalized_ip_string
+#ifdef	__cplusplus
+extern "C" {					// Because of SCO 3.2V4.2
+#endif
+#if !defined( __WIN__)
+#ifdef HAVE_SYS_UN_H
+#include <sys/un.h>
+#endif
+#include <sys/utsname.h>
+#endif // __WIN__
+#ifdef	__cplusplus
+}
+#endif
+
+Host_errors::Host_errors()
+: m_connect(0),
+  m_host_blocked(0),
+  m_nameinfo_transient(0),
+  m_nameinfo_permanent(0),
+  m_format(0),
+  m_addrinfo_transient(0),
+  m_addrinfo_permanent(0),
+  m_FCrDNS(0),
+  m_host_acl(0),
+  m_no_auth_plugin(0),
+  m_auth_plugin(0),
+  m_handshake(0),
+  m_proxy_user(0),
+  m_proxy_user_acl(0),
+  m_authentication(0),
+  m_ssl(0),
+  m_max_user_connection(0),
+  m_max_user_connection_per_hour(0),
+  m_default_database(0),
+  m_init_connect(0),
+  m_local(0)
+{}
+
+Host_errors::~Host_errors()
+{}
+
+void Host_errors::reset()
+{
+  m_connect= 0;
+  m_host_blocked= 0;
+  m_nameinfo_transient= 0;
+  m_nameinfo_permanent= 0;
+  m_format= 0;
+  m_addrinfo_transient= 0;
+  m_addrinfo_permanent= 0;
+  m_FCrDNS= 0;
+  m_host_acl= 0;
+  m_no_auth_plugin= 0;
+  m_auth_plugin= 0;
+  m_handshake= 0;
+  m_proxy_user= 0;
+  m_proxy_user_acl= 0;
+  m_authentication= 0;
+  m_ssl= 0;
+  m_max_user_connection= 0;
+  m_max_user_connection_per_hour= 0;
+  m_default_database= 0;
+  m_init_connect= 0;
+  m_local= 0;
+}
+
+void Host_errors::aggregate(const Host_errors *errors)
+{
+  m_connect+= errors->m_connect;
+  m_host_blocked+= errors->m_host_blocked;
+  m_nameinfo_transient+= errors->m_nameinfo_transient;
+  m_nameinfo_permanent+= errors->m_nameinfo_permanent;
+  m_format+= errors->m_format;
+  m_addrinfo_transient+= errors->m_addrinfo_transient;
+  m_addrinfo_permanent+= errors->m_addrinfo_permanent;
+  m_FCrDNS+= errors->m_FCrDNS;
+  m_host_acl+= errors->m_host_acl;
+  m_no_auth_plugin+= errors->m_no_auth_plugin;
+  m_auth_plugin+= errors->m_auth_plugin;
+  m_handshake+= errors->m_handshake;
+  m_proxy_user+= errors->m_proxy_user;
+  m_proxy_user_acl+= errors->m_proxy_user_acl;
+  m_authentication+= errors->m_authentication;
+  m_ssl+= errors->m_ssl;
+  m_max_user_connection+= errors->m_max_user_connection;
+  m_max_user_connection_per_hour+= errors->m_max_user_connection_per_hour;
+  m_default_database+= errors->m_default_database;
+  m_init_connect+= errors->m_init_connect;
+  m_local+= errors->m_local;
+}
+
+static Hash_filo<Host_entry> *hostname_cache;
+ulong host_cache_size;
+
+void hostname_cache_refresh()
+{
+  hostname_cache->clear();
+}
+
+uint hostname_cache_size()
+{
+  return hostname_cache->size();
+}
+
+void hostname_cache_resize(uint size)
+{
+  hostname_cache->resize(size);
+}
+
+bool hostname_cache_init()
+{
+  Host_entry tmp;
+  uint key_offset= (uint) ((char*) (&tmp.ip_key) - (char*) &tmp);
+
+  if (!(hostname_cache= new Hash_filo<Host_entry>(key_memory_host_cache_hostname,
+                             host_cache_size, key_offset, HOST_ENTRY_KEY_SIZE,
+                             NULL, (my_hash_free_key) free, &my_charset_bin)))
+    return 1;
+
+  hostname_cache->clear();
+
+  return 0;
+}
+
+void hostname_cache_free()
+{
+  delete hostname_cache;
+  hostname_cache= NULL;
+}
+
+void hostname_cache_lock()
+{
+  mysql_mutex_lock(&hostname_cache->lock);
+}
+
+void hostname_cache_unlock()
+{
+  mysql_mutex_unlock(&hostname_cache->lock);
+}
+
+static void prepare_hostname_cache_key(const char *ip_string,
+                                       char *ip_key)
+{
+  size_t ip_string_length= strlen(ip_string);
+  DBUG_ASSERT(ip_string_length < HOST_ENTRY_KEY_SIZE);
+
+  memset(ip_key, 0, HOST_ENTRY_KEY_SIZE);
+  memcpy(ip_key, ip_string, ip_string_length);
+}
+
+Host_entry *hostname_cache_first()
+{ return hostname_cache->first(); }
+
+static inline Host_entry *hostname_cache_search(const char *ip_key)
+{
+  return hostname_cache->search((uchar *) ip_key, 0);
+}
+
+static void add_hostname_impl(const char *ip_key, const char *hostname,
+                              bool validated, Host_errors *errors,
+                              ulonglong now)
+{
+  Host_entry *entry;
+  bool need_add= false;
+
+  entry= hostname_cache_search(ip_key);
+
+  if (likely(entry == NULL))
+  {
+    entry= (Host_entry *) malloc(sizeof (Host_entry));
+    if (entry == NULL)
+      return;
+
+    need_add= true;
+    memcpy(&entry->ip_key, ip_key, HOST_ENTRY_KEY_SIZE);
+    entry->m_errors.reset();
+    entry->m_hostname_length= 0;
+    entry->m_host_validated= false;
+    entry->m_first_seen= now;
+    entry->m_last_seen= now;
+    entry->m_first_error_seen= 0;
+    entry->m_last_error_seen= 0;
+  }
+  else
+  {
+    entry->m_last_seen= now;
+  }
+
+  if (validated)
+  {
+    if (hostname != NULL)
+    {
+      size_t len= strlen(hostname);
+      if (len > sizeof(entry->m_hostname) - 1)
+        len= sizeof(entry->m_hostname) - 1;
+      memcpy(entry->m_hostname, hostname, len);
+      entry->m_hostname[len]= '\0';
+      entry->m_hostname_length= (uint)len;
+
+      DBUG_PRINT("info",
+                 ("Adding/Updating '%s' -> '%s' (validated) to the hostname cache...'",
+                 (const char *) ip_key,
+                 (const char *) entry->m_hostname));
+    }
+    else
+    {
+      entry->m_hostname_length= 0;
+      DBUG_PRINT("info",
+                 ("Adding/Updating '%s' -> NULL (validated) to the hostname cache...'",
+                 (const char *) ip_key));
+    }
+    entry->m_host_validated= true;
+    /*
+      New errors that are considered 'blocking',
+      that will eventually cause the IP to be black listed and blocked.
+    */
+    errors->sum_connect_errors();
+  }
+  else
+  {
+    entry->m_hostname_length= 0;
+    entry->m_host_validated= false;
+    /* Do not count new blocking errors during DNS failures. */
+    errors->clear_connect_errors();
+    DBUG_PRINT("info",
+               ("Adding/Updating '%s' -> NULL (not validated) to the hostname cache...'",
+               (const char *) ip_key));
+  }
+
+  if (errors->has_error())
+    entry->set_error_timestamps(now);
+
+  entry->m_errors.aggregate(errors);
+
+  if (need_add)
+    hostname_cache->add(entry);
+
+  return;
+}
+
+static void add_hostname(const char *ip_key, const char *hostname,
+                         bool validated, Host_errors *errors)
+{
+  if (specialflag & SPECIAL_NO_HOST_CACHE)
+    return;
+
+  ulonglong now= my_hrtime().val;
+
+  mysql_mutex_lock(&hostname_cache->lock);
+
+  add_hostname_impl(ip_key, hostname, validated, errors, now);
+
+  mysql_mutex_unlock(&hostname_cache->lock);
+
+  return;
+}
+
+void inc_host_errors(const char *ip_string, Host_errors *errors)
+{
+  if (!ip_string)
+    return;
+
+  ulonglong now= my_hrtime().val;
+  char ip_key[HOST_ENTRY_KEY_SIZE];
+  prepare_hostname_cache_key(ip_string, ip_key);
+
+  mysql_mutex_lock(&hostname_cache->lock);
+
+  Host_entry *entry= hostname_cache_search(ip_key);
+
+  if (entry)
+  {
+    if (entry->m_host_validated)
+      errors->sum_connect_errors();
+    else
+      errors->clear_connect_errors();
+
+    entry->m_errors.aggregate(errors);
+    entry->set_error_timestamps(now);
+  }
+
+  mysql_mutex_unlock(&hostname_cache->lock);
+}
+
+void reset_host_connect_errors(const char *ip_string)
+{
+  if (!ip_string)
+    return;
+
+  char ip_key[HOST_ENTRY_KEY_SIZE];
+  prepare_hostname_cache_key(ip_string, ip_key);
+
+  mysql_mutex_lock(&hostname_cache->lock);
+
+  Host_entry *entry= hostname_cache_search(ip_key);
+
+  if (entry)
+    entry->m_errors.clear_connect_errors();
+
+  mysql_mutex_unlock(&hostname_cache->lock);
+}
+
+static inline bool is_ip_loopback(const struct sockaddr *ip)
+{
+  switch (ip->sa_family) {
+  case AF_INET:
+    {
+      /* Check for IPv4 127.0.0.1. */
+      struct in_addr *ip4= &((struct sockaddr_in *) ip)->sin_addr;
+      return ntohl(ip4->s_addr) == INADDR_LOOPBACK;
+    }
+
+#ifdef HAVE_IPV6
+  case AF_INET6:
+    {
+      /* Check for IPv6 ::1. */
+      struct in6_addr *ip6= &((struct sockaddr_in6 *) ip)->sin6_addr;
+      return IN6_IS_ADDR_LOOPBACK(ip6);
+    }
+#endif /* HAVE_IPV6 */
+
+  default:
+    return FALSE;
+  }
+}
+
+static inline bool is_hostname_valid(const char *hostname)
+{
+  /*
+    A hostname is invalid if it starts with a number followed by a dot
+    (IPv4 address).
+  */
+
+  if (!my_isdigit(&my_charset_latin1, hostname[0]))
+    return TRUE;
+
+  const char *p= hostname + 1;
+
+  while (my_isdigit(&my_charset_latin1, *p))
+    ++p;
+
+  return *p != '.';
+}
+
+/**
+  Resolve IP-address to host name.
+
+  This function does the following things:
+    - resolves IP-address;
+    - employs Forward Confirmed Reverse DNS technique to validate IP-address;
+    - returns host name if IP-address is validated;
+    - set value to out-variable connect_errors -- this variable represents the
+      number of connection errors from the specified IP-address.
+    - update the host_cache statistics
+
+  NOTE: connect_errors are counted (are supported) only for the clients
+  where IP-address can be resolved and FCrDNS check is passed.
+
+  @param [in]  ip_storage IP address (sockaddr). Must be set.
+  @param [in]  ip_string  IP address (string). Must be set.
+  @param [out] hostname
+  @param [out] connect_errors
+
+  @return Error status
+  @retval 0 Success
+  @retval RC_BLOCKED_HOST The host is blocked.
+
+  The function does not set/report MySQL server error in case of failure.
+  It's caller's responsibility to handle failures of this function
+  properly.
+*/
+
+int ip_to_hostname(struct sockaddr_storage *ip_storage,
+                   const char *ip_string,
+                   const char **hostname,
+                   uint *connect_errors)
+{
+  const struct sockaddr *ip= (const sockaddr *) ip_storage;
+  int err_code;
+  bool err_status __attribute__((unused));
+  Host_errors errors;
+
+  DBUG_ENTER("ip_to_hostname");
+  DBUG_PRINT("info", ("IP address: '%s'; family: %d.",
+                      (const char *) ip_string,
+                      (int) ip->sa_family));
+
+  /* Default output values, for most cases. */
+  *hostname= NULL;
+  *connect_errors= 0;
+
+  /* Check if we have loopback address (127.0.0.1 or ::1). */
+
+  if (is_ip_loopback(ip))
+  {
+    DBUG_PRINT("info", ("Loopback address detected."));
+
+    /* Do not count connect errors from localhost. */
+    *hostname= my_localhost;
+
+    DBUG_RETURN(0);
+  }
+
+  /* Prepare host name cache key. */
+
+  char ip_key[HOST_ENTRY_KEY_SIZE];
+  prepare_hostname_cache_key(ip_string, ip_key);
+
+  /* Check first if we have host name in the cache. */
+
+  if (!(specialflag & SPECIAL_NO_HOST_CACHE))
+  {
+    ulonglong now= my_hrtime().val;
+
+    mysql_mutex_lock(&hostname_cache->lock);
+
+    Host_entry *entry= hostname_cache_search(ip_key);
+
+    if (entry)
+    {
+      entry->m_last_seen= now;
+      *connect_errors= entry->m_errors.m_connect;
+
+      if (unlikely(entry->m_errors.m_connect >= max_connect_errors))
+      {
+        entry->m_errors.m_host_blocked++;
+        entry->set_error_timestamps(now);
+        mysql_mutex_unlock(&hostname_cache->lock);
+        DBUG_RETURN(RC_BLOCKED_HOST);
+      }
+
+      /*
+        If there is an IP -> HOSTNAME association in the cache,
+        but for a hostname that was not validated,
+        do not return that hostname: perform the network validation again.
+      */
+      if (entry->m_host_validated)
+      {
+        if (entry->m_hostname_length)
+          *hostname= my_strdup(key_memory_host_cache_hostname,
+                               entry->m_hostname, MYF(0));
+
+        DBUG_PRINT("info",("IP (%s) has been found in the cache. "
+                           "Hostname: '%s'",
+                           (const char *) ip_key,
+                           (const char *) (*hostname? *hostname : "null")
+                          ));
+
+        mysql_mutex_unlock(&hostname_cache->lock);
+
+        DBUG_RETURN(0);
+      }
+    }
+
+    mysql_mutex_unlock(&hostname_cache->lock);
+  }
+
+  /*
+    Resolve host name. Return an error if a host name can not be resolved
+    (instead of returning the numeric form of the host name).
+  */
+
+  char hostname_buffer[NI_MAXHOST];
+
+  DBUG_PRINT("info", ("Resolving '%s'...", (const char *) ip_key));
+
+  err_code= vio_getnameinfo(ip, hostname_buffer, NI_MAXHOST, NULL, 0,
+                            NI_NAMEREQD);
+
+  /*
+  ===========================================================================
+  DEBUG code only (begin)
+  Simulate various output from vio_getnameinfo().
+  ===========================================================================
+  */
+
+  DBUG_EXECUTE_IF("getnameinfo_error_noname",
+                  {
+                    strcpy(hostname_buffer, "<garbage>");
+                    err_code= EAI_NONAME;
+                  }
+                  );
+
+  DBUG_EXECUTE_IF("getnameinfo_error_again",
+                  {
+                    strcpy(hostname_buffer, "<garbage>");
+                    err_code= EAI_AGAIN;
+                  }
+                  );
+
+  DBUG_EXECUTE_IF("getnameinfo_fake_ipv4",
+                  {
+                    strcpy(hostname_buffer, "santa.claus.ipv4.example.com");
+                    err_code= 0;
+                  }
+                  );
+
+  DBUG_EXECUTE_IF("getnameinfo_fake_ipv6",
+                  {
+                    strcpy(hostname_buffer, "santa.claus.ipv6.example.com");
+                    err_code= 0;
+                  }
+                  );
+
+  DBUG_EXECUTE_IF("getnameinfo_format_ipv4",
+                  {
+                    strcpy(hostname_buffer, "12.12.12.12");
+                    err_code= 0;
+                  }
+                  );
+
+  DBUG_EXECUTE_IF("getnameinfo_format_ipv6",
+                  {
+                    strcpy(hostname_buffer, "12:DEAD:BEEF:0");
+                    err_code= 0;
+                  }
+                  );
+
+  /*
+  ===========================================================================
+  DEBUG code only (end)
+  ===========================================================================
+  */
+
+  if (err_code)
+  {
+    // NOTE: gai_strerror() returns a string ending by a dot.
+
+    DBUG_PRINT("error", ("IP address '%s' could not be resolved: %s",
+                         (const char *) ip_key,
+                         (const char *) gai_strerror(err_code)));
+
+    sql_print_warning("IP address '%s' could not be resolved: %s",
+                      (const char *) ip_key,
+                      (const char *) gai_strerror(err_code));
+
+    bool validated;
+    if (vio_is_no_name_error(err_code))
+    {
+      /*
+        The no-name error means that there is no reverse address mapping
+        for the IP address. A host name can not be resolved.
+      */
+      errors.m_nameinfo_permanent= 1;
+      validated= true;
+    }
+    else
+    {
+      /*
+        If it is not the no-name error, we should not cache the hostname
+        (or rather its absence), because the failure might be transient.
+        Only the ip error statistics are cached.
+      */
+      errors.m_nameinfo_transient= 1;
+      validated= false;
+    }
+    add_hostname(ip_key, NULL, validated, &errors);
+
+    DBUG_RETURN(0);
+  }
+
+  DBUG_PRINT("info", ("IP '%s' resolved to '%s'.",
+                      (const char *) ip_key,
+                      (const char *) hostname_buffer));
+
+  /*
+    Validate hostname: the server does not accept host names, which
+    resemble IP addresses.
+
+    The thing is that theoretically, a host name can be in a form of IPv4
+    address (123.example.org, or 1.2 or even 1.2.3.4). We have to deny such
+    host names because ACL-systems is not designed to work with them.
+
+    For example, it is possible to specify a host name mask (like
+    192.168.1.%) for an ACL rule. Then, if IPv4-like hostnames are allowed,
+    there is a security hole: instead of allowing access for
+    192.168.1.0/255 network (which was assumed by the user), the access
+    will be allowed for host names like 192.168.1.example.org.
+  */
+
+  if (!is_hostname_valid(hostname_buffer))
+  {
+    DBUG_PRINT("error", ("IP address '%s' has been resolved "
+                         "to the host name '%s', which resembles "
+                         "IPv4-address itself.",
+                         (const char *) ip_key,
+                         (const char *) hostname_buffer));
+
+    sql_print_warning("IP address '%s' has been resolved "
+                      "to the host name '%s', which resembles "
+                      "IPv4-address itself.",
+                      (const char *) ip_key,
+                      (const char *) hostname_buffer);
+
+    errors.m_format= 1;
+    add_hostname(ip_key, hostname_buffer, false, &errors);
+
+    DBUG_RETURN(false);
+  }
+
+  /* Get IP-addresses for the resolved host name (FCrDNS technique). */
+
+  struct addrinfo hints;
+  struct addrinfo *addr_info_list;
+  /*
+    Makes fault injection with DBUG_EXECUTE_IF easier.
+    Invoking free_addr_info(NULL) crashes on some platforms.
+  */
+  bool free_addr_info_list= false;
+
+  memset(&hints, 0, sizeof (struct addrinfo));
+  hints.ai_flags= AI_PASSIVE;
+  hints.ai_socktype= SOCK_STREAM;
+  hints.ai_family= AF_UNSPEC;
+
+  DBUG_PRINT("info", ("Getting IP addresses for hostname '%s'...",
+                      (const char *) hostname_buffer));
+
+  err_code= getaddrinfo(hostname_buffer, NULL, &hints, &addr_info_list);
+  if (err_code == 0)
+    free_addr_info_list= true;
+
+  /*
+  ===========================================================================
+  DEBUG code only (begin)
+  Simulate various output from getaddrinfo().
+  ===========================================================================
+  */
+  DBUG_EXECUTE_IF("getaddrinfo_error_noname",
+                  {
+                    if (free_addr_info_list)
+                      freeaddrinfo(addr_info_list);
+
+                    addr_info_list= NULL;
+                    err_code= EAI_NONAME;
+                    free_addr_info_list= false;
+                  }
+                  );
+
+  DBUG_EXECUTE_IF("getaddrinfo_error_again",
+                  {
+                    if (free_addr_info_list)
+                      freeaddrinfo(addr_info_list);
+
+                    addr_info_list= NULL;
+                    err_code= EAI_AGAIN;
+                    free_addr_info_list= false;
+                  }
+                  );
+
+  DBUG_EXECUTE_IF("getaddrinfo_fake_bad_ipv4",
+                  {
+                    if (free_addr_info_list)
+                      freeaddrinfo(addr_info_list);
+
+                    struct sockaddr_in *debug_addr;
+                    /*
+                      Not thread safe, which is ok.
+                      Only one connection at a time is tested with
+                      fault injection.
+                    */
+                    static struct sockaddr_in debug_sock_addr[2];
+                    static struct addrinfo debug_addr_info[2];
+                    /* Simulating ipv4 192.0.2.126 */
+                    debug_addr= & debug_sock_addr[0];
+                    debug_addr->sin_family= AF_INET;
+                    inet_pton(AF_INET,"192.0.2.126", &debug_addr->sin_addr);
+
+                    /* Simulating ipv4 192.0.2.127 */
+                    debug_addr= & debug_sock_addr[1];
+                    debug_addr->sin_family= AF_INET;
+                    inet_pton(AF_INET,"192.0.2.127", &debug_addr->sin_addr);
+
+                    debug_addr_info[0].ai_addr= (struct sockaddr*) & debug_sock_addr[0];
+                    debug_addr_info[0].ai_addrlen= sizeof (struct sockaddr_in);
+                    debug_addr_info[0].ai_next= & debug_addr_info[1];
+
+                    debug_addr_info[1].ai_addr= (struct sockaddr*) & debug_sock_addr[1];
+                    debug_addr_info[1].ai_addrlen= sizeof (struct sockaddr_in);
+                    debug_addr_info[1].ai_next= NULL;
+
+                    addr_info_list= & debug_addr_info[0];
+                    err_code= 0;
+                    free_addr_info_list= false;
+                  }
+                  );
+
+  DBUG_EXECUTE_IF("getaddrinfo_fake_good_ipv4",
+                  {
+                    if (free_addr_info_list)
+                      freeaddrinfo(addr_info_list);
+
+                    struct sockaddr_in *debug_addr;
+                    static struct sockaddr_in debug_sock_addr[2];
+                    static struct addrinfo debug_addr_info[2];
+                    /* Simulating ipv4 192.0.2.5 */
+                    debug_addr= & debug_sock_addr[0];
+                    debug_addr->sin_family= AF_INET;
+                    inet_pton(AF_INET,"192.0.2.5", &debug_addr->sin_addr);
+
+                    /* Simulating ipv4 192.0.2.4 */
+                    debug_addr= & debug_sock_addr[1];
+                    debug_addr->sin_family= AF_INET;
+                    inet_pton(AF_INET,"192.0.2.4", &debug_addr->sin_addr);
+
+                    debug_addr_info[0].ai_addr= (struct sockaddr*) & debug_sock_addr[0];
+                    debug_addr_info[0].ai_addrlen= sizeof (struct sockaddr_in);
+                    debug_addr_info[0].ai_next= & debug_addr_info[1];
+
+                    debug_addr_info[1].ai_addr= (struct sockaddr*) & debug_sock_addr[1];
+                    debug_addr_info[1].ai_addrlen= sizeof (struct sockaddr_in);
+                    debug_addr_info[1].ai_next= NULL;
+
+                    addr_info_list= & debug_addr_info[0];
+                    err_code= 0;
+                    free_addr_info_list= false;
+                  }
+                  );
+
+#ifdef HAVE_IPV6
+  DBUG_EXECUTE_IF("getaddrinfo_fake_bad_ipv6",
+                  {
+                    if (free_addr_info_list)
+                      freeaddrinfo(addr_info_list);
+
+                    struct sockaddr_in6 *debug_addr;
+                    struct in6_addr *ip6;
+                    /*
+                      Not thread safe, which is ok.
+                      Only one connection at a time is tested with
+                      fault injection.
+                    */
+                    static struct sockaddr_in6 debug_sock_addr[2];
+                    static struct addrinfo debug_addr_info[2];
+                    /* Simulating ipv6 2001:DB8::6:7E */
+                    debug_addr= & debug_sock_addr[0];
+                    debug_addr->sin6_family= AF_INET6;
+                    ip6= & debug_addr->sin6_addr;
+                    inet_pton(AF_INET6,"2001:DB8::6:7E",ip6);
+
+                    /* Simulating ipv6 2001:DB8::6:7F */
+                    debug_addr= & debug_sock_addr[1];
+                    debug_addr->sin6_family= AF_INET6;
+                    ip6= & debug_addr->sin6_addr;
+                    inet_pton(AF_INET6,"2001:DB8::6:7F",ip6);
+
+                    debug_addr_info[0].ai_addr= (struct sockaddr*) & debug_sock_addr[0];
+                    debug_addr_info[0].ai_addrlen= sizeof (struct sockaddr_in6);
+                    debug_addr_info[0].ai_next= & debug_addr_info[1];
+
+                    debug_addr_info[1].ai_addr= (struct sockaddr*) & debug_sock_addr[1];
+                    debug_addr_info[1].ai_addrlen= sizeof (struct sockaddr_in6);
+                    debug_addr_info[1].ai_next= NULL;
+
+                    addr_info_list= & debug_addr_info[0];
+                    err_code= 0;
+                    free_addr_info_list= false;
+                  }
+                  );
+
+  DBUG_EXECUTE_IF("getaddrinfo_fake_good_ipv6",
+                  {
+                    if (free_addr_info_list)
+                      freeaddrinfo(addr_info_list);
+
+                    struct sockaddr_in6 *debug_addr;
+                    struct in6_addr *ip6;
+                    /*
+                      Not thread safe, which is ok.
+                      Only one connection at a time is tested with
+                      fault injection.
+                    */
+                    static struct sockaddr_in6 debug_sock_addr[2];
+                    static struct addrinfo debug_addr_info[2];
+                    /* Simulating ipv6 2001:DB8::6:7 */
+                    debug_addr= & debug_sock_addr[0];
+                    debug_addr->sin6_family= AF_INET6;
+                    ip6= & debug_addr->sin6_addr;
+                    ip6->s6_addr[ 0] = 0x20;
+                    ip6->s6_addr[ 1] = 0x01;
+                    ip6->s6_addr[ 2] = 0x0d;
+                    ip6->s6_addr[ 3] = 0xb8;
+                    ip6->s6_addr[ 4] = 0x00;
+                    ip6->s6_addr[ 5] = 0x00;
+                    ip6->s6_addr[ 6] = 0x00;
+                    ip6->s6_addr[ 7] = 0x00;
+                    ip6->s6_addr[ 8] = 0x00;
+                    ip6->s6_addr[ 9] = 0x00;
+                    ip6->s6_addr[10] = 0x00;
+                    ip6->s6_addr[11] = 0x00;
+                    ip6->s6_addr[12] = 0x00;
+                    ip6->s6_addr[13] = 0x06;
+                    ip6->s6_addr[14] = 0x00;
+                    ip6->s6_addr[15] = 0x07;
+
+                    /* Simulating ipv6 2001:DB8::6:6 */
+                    debug_addr= & debug_sock_addr[1];
+                    debug_addr->sin6_family= AF_INET6;
+                    ip6= & debug_addr->sin6_addr;
+                    ip6->s6_addr[ 0] = 0x20;
+                    ip6->s6_addr[ 1] = 0x01;
+                    ip6->s6_addr[ 2] = 0x0d;
+                    ip6->s6_addr[ 3] = 0xb8;
+                    ip6->s6_addr[ 4] = 0x00;
+                    ip6->s6_addr[ 5] = 0x00;
+                    ip6->s6_addr[ 6] = 0x00;
+                    ip6->s6_addr[ 7] = 0x00;
+                    ip6->s6_addr[ 8] = 0x00;
+                    ip6->s6_addr[ 9] = 0x00;
+                    ip6->s6_addr[10] = 0x00;
+                    ip6->s6_addr[11] = 0x00;
+                    ip6->s6_addr[12] = 0x00;
+                    ip6->s6_addr[13] = 0x06;
+                    ip6->s6_addr[14] = 0x00;
+                    ip6->s6_addr[15] = 0x06;
+
+                    debug_addr_info[0].ai_addr= (struct sockaddr*) & debug_sock_addr[0];
+                    debug_addr_info[0].ai_addrlen= sizeof (struct sockaddr_in6);
+                    debug_addr_info[0].ai_next= & debug_addr_info[1];
+
+                    debug_addr_info[1].ai_addr= (struct sockaddr*) & debug_sock_addr[1];
+                    debug_addr_info[1].ai_addrlen= sizeof (struct sockaddr_in6);
+                    debug_addr_info[1].ai_next= NULL;
+
+                    addr_info_list= & debug_addr_info[0];
+                    err_code= 0;
+                    free_addr_info_list= false;
+                  }
+                  );
+#endif /* HAVE_IPV6 */
+
+  /*
+  ===========================================================================
+  DEBUG code only (end)
+  ===========================================================================
+  */
+
+  if (err_code != 0)
+  {
+    sql_print_warning("Host name '%s' could not be resolved: %s",
+                      (const char *) hostname_buffer,
+                      (const char *) gai_strerror(err_code));
+
+    bool validated;
+
+    if (err_code == EAI_NONAME)
+    {
+      errors.m_addrinfo_permanent= 1;
+      validated= true;
+    }
+    else
+    {
+      /*
+        Don't cache responses when the DNS server is down, as otherwise
+        transient DNS failure may leave any number of clients (those
+        that attempted to connect during the outage) unable to connect
+        indefinitely.
+        Only cache error statistics.
+      */
+      errors.m_addrinfo_transient= 1;
+      validated= false;
+    }
+    add_hostname(ip_key, NULL, validated, &errors);
+
+    DBUG_RETURN(false);
+  }
+
+  /* Check that getaddrinfo() returned the used IP (FCrDNS technique). */
+
+  DBUG_PRINT("info", ("The following IP addresses found for '%s':",
+                      (const char *) hostname_buffer));
+
+  for (struct addrinfo *addr_info= addr_info_list;
+       addr_info; addr_info= addr_info->ai_next)
+  {
+    char ip_buffer[HOST_ENTRY_KEY_SIZE];
+
+    {
+      err_status=
+        vio_get_normalized_ip_string(addr_info->ai_addr, (int)addr_info->ai_addrlen,
+                                     ip_buffer, sizeof (ip_buffer));
+      DBUG_ASSERT(!err_status);
+    }
+
+    DBUG_PRINT("info", ("  - '%s'", (const char *) ip_buffer));
+
+    if (strcasecmp(ip_key, ip_buffer) == 0)
+    {
+      /* Copy host name string to be stored in the cache. */
+
+      *hostname= my_strdup(key_memory_host_cache_hostname,
+                           hostname_buffer, MYF(0));
+
+      if (!*hostname)
+      {
+        DBUG_PRINT("error", ("Out of memory."));
+
+        if (free_addr_info_list)
+          freeaddrinfo(addr_info_list);
+        DBUG_RETURN(true);
+      }
+
+      break;
+    }
+  }
+
+  /* Log resolved IP-addresses if no match was found. */
+
+  if (!*hostname)
+  {
+    errors.m_FCrDNS= 1;
+
+    sql_print_warning("Hostname '%s' does not resolve to '%s'.",
+                      (const char *) hostname_buffer,
+                      (const char *) ip_key);
+    sql_print_information("Hostname '%s' has the following IP addresses:",
+                          (const char *) hostname_buffer);
+
+    for (struct addrinfo *addr_info= addr_info_list;
+         addr_info; addr_info= addr_info->ai_next)
+    {
+      char ip_buffer[HOST_ENTRY_KEY_SIZE];
+
+      err_status=
+        vio_get_normalized_ip_string(addr_info->ai_addr, (int)addr_info->ai_addrlen,
+                                     ip_buffer, sizeof (ip_buffer));
+      DBUG_ASSERT(!err_status);
+
+      sql_print_information(" - %s", (const char *) ip_buffer);
+    }
+  }
+
+  /* Add an entry for the IP to the cache. */
+  add_hostname(ip_key, *hostname, true, &errors);
+
+  /* Free the result of getaddrinfo(). */
+  if (free_addr_info_list)
+    freeaddrinfo(addr_info_list);
+
+  DBUG_RETURN(false);
+}