/*
     This file is part of GNUnet.
     Copyright (C) 2011 GNUnet e.V.

     GNUnet is free software: you can redistribute it and/or modify it
     under the terms of the GNU Affero General Public License as published
     by the Free Software Foundation, either version 3 of the License,
     or (at your option) any later version.

     GNUnet 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
     Affero General Public License for more details.

     You should have received a copy of the GNU Affero General Public License
     along with this program.  If not, see <http://www.gnu.org/licenses/>.

     SPDX-License-Identifier: AGPL3.0-or-later
 */

/**
 * @file src/dns/gnunet-dns-monitor.c
 * @brief Tool to monitor DNS queries
 * @author Christian Grothoff
 */

#include "platform.h"
#include "gnunet_util_lib.h"
#include "gnunet_dns_service.h"

/**
 * Handle to transport service.
 */
static struct GNUNET_DNS_Handle *handle;

/**
 * Option -i.
 */
static int inbound_only;

/**
 * Option -o.
 */
static int outbound_only;

/**
 * Global return value (0 success).
 */
static int ret;

/**
 * Selected level of verbosity.
 */
static unsigned int verbosity;


/**
 * Convert numeric DNS record type to a string.
 *
 * @param type type to convert
 * @return type as string, only valid until the next call to this function
 */
static const char *
get_type (uint16_t type)
{
  static char buf[6];

  switch (type)
  {
  case GNUNET_DNSPARSER_TYPE_A: return "A";

  case GNUNET_DNSPARSER_TYPE_NS: return "NS";

  case GNUNET_DNSPARSER_TYPE_CNAME: return "CNAME";

  case GNUNET_DNSPARSER_TYPE_SOA: return "SOA";

  case GNUNET_DNSPARSER_TYPE_PTR: return "PTR";

  case GNUNET_DNSPARSER_TYPE_MX: return "MX";

  case GNUNET_DNSPARSER_TYPE_TXT: return "TXT";

  case GNUNET_DNSPARSER_TYPE_AAAA: return "AAAA";

  case GNUNET_DNSPARSER_TYPE_SRV: return "SRV";

  case GNUNET_DNSPARSER_TYPE_URI: return "URI";
  }
  GNUNET_snprintf (buf, sizeof(buf), "%u", (unsigned int) type);
  return buf;
}


/**
 * Convert numeric DNS record class to a string.
 *
 * @param class class to convert
 * @return class as string, only valid until the next call to this function
 */
static const char *
get_class (uint16_t class)
{
  static char buf[6];

  switch (class)
  {
  case GNUNET_TUN_DNS_CLASS_INTERNET: return "IN";

  case GNUNET_TUN_DNS_CLASS_CHAOS: return "CHAOS";

  case GNUNET_TUN_DNS_CLASS_HESIOD: return "HESIOD";
  }
  GNUNET_snprintf (buf, sizeof(buf), "%u", (unsigned int) class);
  return buf;
}


/**
 * Output the given DNS query to stdout.
 *
 * @param query query to display.
 */
static void
display_query (const struct GNUNET_DNSPARSER_Query *query)
{
  fprintf (stdout,
           "\t\t%s %s: %s\n",
           get_class (query->dns_traffic_class),
           get_type (query->type),
           query->name);
}


/**
 * Output the given DNS record to stdout.
 *
 * @param record record to display.
 */
static void
display_record (const struct GNUNET_DNSPARSER_Record *record)
{
  const char *format;
  char buf[INET6_ADDRSTRLEN];
  char *tmp;

  tmp = NULL;
  switch (record->type)
  {
  case GNUNET_DNSPARSER_TYPE_A:
    if (record->data.raw.data_len != sizeof(struct in_addr))
      format = "<invalid>";
    else
      format = inet_ntop (AF_INET, record->data.raw.data, buf, sizeof(buf));
    break;

  case GNUNET_DNSPARSER_TYPE_AAAA:
    if (record->data.raw.data_len != sizeof(struct in6_addr))
      format = "<invalid>";
    else
      format = inet_ntop (AF_INET6, record->data.raw.data, buf, sizeof(buf));
    break;

  case GNUNET_DNSPARSER_TYPE_NS:
  case GNUNET_DNSPARSER_TYPE_CNAME:
  case GNUNET_DNSPARSER_TYPE_PTR:
    format = record->data.hostname;
    break;

  case GNUNET_DNSPARSER_TYPE_SOA:
    if (NULL == record->data.soa)
      format = "<invalid>";
    else
    {
      GNUNET_asprintf (&tmp,
                       "origin: %s, mail: %s, serial = %u, refresh = %u s, retry = %u s, expire = %u s, minimum = %u s",
                       record->data.soa->mname,
                       record->data.soa->rname,
                       (unsigned int) record->data.soa->serial,
                       (unsigned int) record->data.soa->refresh,
                       (unsigned int) record->data.soa->retry,
                       (unsigned int) record->data.soa->expire,
                       (unsigned int) record->data.soa->minimum_ttl);
      format = tmp;
    }
    break;

  case GNUNET_DNSPARSER_TYPE_MX:
    if (record->data.mx == NULL)
      format = "<invalid>";
    else
    {
      GNUNET_asprintf (&tmp,
                       "%u: %s",
                       record->data.mx->preference,
                       record->data.mx->mxhost);
      format = tmp;
    }
    break;

  case GNUNET_DNSPARSER_TYPE_SRV:
    if (NULL == record->data.srv)
      format = "<invalid>";
    else
    {
      GNUNET_asprintf (&tmp,
                       "priority %u, weight = %u, port = %u, target = %s",
                       (unsigned int) record->data.srv->priority,
                       (unsigned int) record->data.srv->weight,
                       (unsigned int) record->data.srv->port,
                       record->data.srv->target);
      format = tmp;
    }
    break;

  case GNUNET_DNSPARSER_TYPE_URI:
    if (NULL == record->data.uri)
      format = "<invalid>";
    else
    {
      GNUNET_asprintf (&tmp,
                       "priority %u, weight = %u, target = \"%s\"",
                       (unsigned int) record->data.uri->priority,
                       (unsigned int) record->data.uri->weight,
                       record->data.uri->target);
      format = tmp;
    }
    break;


  case GNUNET_DNSPARSER_TYPE_TXT:
    GNUNET_asprintf (&tmp,
                     "%.*s",
                     (unsigned int) record->data.raw.data_len,
                     (char*) record->data.raw.data);
    format = tmp;
    break;

  default:
    format = "<payload>";
    break;
  }
  fprintf (stdout,
           "\t\t%s %s: %s = %s (%u s)\n",
           get_class (record->dns_traffic_class),
           get_type (record->type),
           record->name,
           format,
           (unsigned int) (GNUNET_TIME_absolute_get_remaining (
                             record->expiration_time).rel_value_us / 1000LL
                           / 1000LL));
  GNUNET_free (tmp);
}


/**
 * Signature of a function that is called whenever the DNS service
 * encounters a DNS request and needs to do something with it.  The
 * function has then the chance to generate or modify the response by
 * calling one of the three "GNUNET_DNS_request_*" continuations.
 *
 * When a request is intercepted, this function is called first to
 * give the client a chance to do the complete address resolution;
 * "rdata" will be NULL for this first call for a DNS request, unless
 * some other client has already filled in a response.
 *
 * If multiple clients exist, all of them are called before the global
 * DNS.  The global DNS is only called if all of the clients'
 * functions call GNUNET_DNS_request_forward.  Functions that call
 * GNUNET_DNS_request_forward will be called again before a final
 * response is returned to the application.  If any of the clients'
 * functions call GNUNET_DNS_request_drop, the response is dropped.
 *
 * @param cls closure
 * @param rh request handle to user for reply
 * @param request_length number of bytes in request
 * @param request udp payload of the DNS request
 */
static void
display_request (void *cls,
                 struct GNUNET_DNS_RequestHandle *rh,
                 size_t request_length,
                 const char *request)
{
  static const char *return_codes[] = {
    "No error", "Format error", "Server failure", "Name error",
    "Not implemented", "Refused", "YXDomain", "YXRRset",
    "NXRRset", "NOT AUTH", "NOT ZONE", "<invalid>",
    "<invalid>", "<invalid>", "<invalid>", "<invalid>"
  };
  static const char *op_codes[] = {
    "Query", "Inverse query", "Status", "<invalid>",
    "<invalid>", "<invalid>", "<invalid>", "<invalid>",
    "<invalid>", "<invalid>", "<invalid>", "<invalid>",
    "<invalid>", "<invalid>", "<invalid>", "<invalid>"
  };
  struct GNUNET_DNSPARSER_Packet *p;
  unsigned int i;

  p = GNUNET_DNSPARSER_parse (request, request_length);
  if (NULL == p)
  {
    fprintf (stderr, "Received malformed DNS packet!\n");
    // FIXME: drop instead?
    GNUNET_DNS_request_forward (rh);
    return;
  }
  fprintf (stdout,
           "%s with ID: %5u Flags: %s%s%s%s%s%s, Return Code: %s, Opcode: %s\n",
           p->flags.query_or_response ? "Response" : "Query",
           p->id,
           p->flags.recursion_desired ? "RD " : "",
           p->flags.message_truncated ? "MT " : "",
           p->flags.authoritative_answer ? "AA " : "",
           p->flags.checking_disabled ? "CD " : "",
           p->flags.authenticated_data ? "AD " : "",
           p->flags.recursion_available ? "RA " : "",
           return_codes[p->flags.return_code & 15],
           op_codes[p->flags.opcode & 15]);
  if (p->num_queries > 0)
    fprintf (stdout,
             "\tQueries:\n");
  for (i = 0; i < p->num_queries; i++)
    display_query (&p->queries[i]);

  if (p->num_answers > 0)
    fprintf (stdout,
             "\tAnswers:\n");
  for (i = 0; i < p->num_answers; i++)
    display_record (&p->answers[i]);
  fprintf (stdout, "\n");
  GNUNET_DNSPARSER_free_packet (p);
  GNUNET_DNS_request_forward (rh);
}


/**
 * Shutdown.
 */
static void
do_disconnect (void *cls)
{
  if (NULL != handle)
  {
    GNUNET_DNS_disconnect (handle);
    handle = NULL;
  }
}


/**
 * Main function that will be run by the scheduler.
 *
 * @param cls closure
 * @param args remaining command-line arguments
 * @param cfgfile name of the configuration file used (for saving, can be NULL!)
 * @param cfg configuration
 */
static void
run (void *cls, char *const *args, const char *cfgfile,
     const struct GNUNET_CONFIGURATION_Handle *cfg)
{
  enum GNUNET_DNS_Flags flags;

  flags = GNUNET_DNS_FLAG_REQUEST_MONITOR | GNUNET_DNS_FLAG_RESPONSE_MONITOR;
  if (inbound_only | outbound_only)
    flags = 0;
  if (inbound_only)
    flags |= GNUNET_DNS_FLAG_REQUEST_MONITOR;
  if (outbound_only)
    flags |= GNUNET_DNS_FLAG_RESPONSE_MONITOR;
  handle =
    GNUNET_DNS_connect (cfg,
                        flags,
                        &display_request,
                        NULL);
  GNUNET_SCHEDULER_add_shutdown (&do_disconnect, NULL);
}


int
main (int argc, char *const *argv)
{
  struct GNUNET_GETOPT_CommandLineOption options[] = {
    GNUNET_GETOPT_option_flag ('i',
                               "inbound-only",
                               gettext_noop ("only monitor DNS queries"),
                               &inbound_only),

    GNUNET_GETOPT_option_flag ('o',
                               "outbound-only",
                               gettext_noop ("only monitor DNS queries"),
                               &outbound_only),

    GNUNET_GETOPT_option_verbose (&verbosity),
    GNUNET_GETOPT_OPTION_END
  };

  ret = (GNUNET_OK ==
         GNUNET_PROGRAM_run (GNUNET_OS_project_data_gnunet (),
                             argc, argv, "gnunet-dns-monitor",
                             gettext_noop
                               ("Monitor DNS queries."), options,
                             &run, NULL)) ? ret : 1;
  return ret;
}


/* end of gnunet-dns-monitor.c */
