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path: root/src/sensor/gnunet-service-sensor.c
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/*
     This file is part of GNUnet.
     (C) 

     GNUnet 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, 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
     General Public License for more details.

     You should have received a copy of the GNU General Public License
     along with GNUnet; see the file COPYING.  If not, write to the
     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
     Boston, MA 02111-1307, USA.
*/

/**
 * @file sensor/gnunet-service-sensor.c
 * @brief sensor service implementation
 * @author Omar Tarabai
 */
#include <inttypes.h>
#include "platform.h"
#include "gnunet_util_lib.h"
#include "sensor.h"
#include "gnunet_statistics_service.h"
#include "gnunet_peerstore_service.h"

/**
 * Minimum sensor execution interval (in seconds)
 */
#define MIN_INTERVAL 30

/**
 * Structure containing sensor definition
 */
struct SensorInfo
{

  /**
   * The configuration handle
   * carrying sensor information
   */
  struct GNUNET_CONFIGURATION_Handle *cfg;

  /*
   * Sensor name
   */
  char *name;

  /*
   * Path to definition file
   */
  char *def_file;

  /*
   * First part of version number
   */
  uint16_t version_major;

  /*
   * Second part of version number
   */
  uint16_t version_minor;

  /*
   * Sensor description
   */
  char *description;

  /*
   * Sensor currently enabled
   */
  int enabled;

  /*
   * Category under which the sensor falls (e.g. tcp, datastore)
   */
  char *category;

  /*
   * When does the sensor become active
   */
  struct GNUNET_TIME_Absolute *start_time;

  /*
   * When does the sensor expire
   */
  struct GNUNET_TIME_Absolute *end_time;

  /*
   * Time interval to collect sensor information (e.g. every 1 min)
   */
  struct GNUNET_TIME_Relative interval;

  /*
   * Lifetime of an information sample after which it is deleted from storage
   * If not supplied, will default to the interval value
   */
  struct GNUNET_TIME_Relative lifetime;

  /*
   * A set of required peer capabilities for the sensor to collect meaningful information (e.g. ipv6)
   */
  char *capabilities;

  /*
   * Either "gnunet-statistics" or external "process"
   */
  char *source;

  /*
   * Name of the GNUnet service that is the source for the gnunet-statistics entry
   */
  char *gnunet_stat_service;

  /*
   * Name of the gnunet-statistics entry
   */
  char *gnunet_stat_name;

  /**
   * Handle to statistics get request (OR GNUNET_SCHEDULER_NO_TASK)
   */
  struct GNUNET_STATISTICS_GetHandle *gnunet_stat_get_handle;

  /*
   * Name of the external process to be executed
   */
  char *ext_process;

  /*
   * Arguments to be passed to the external process
   */
  char *ext_args;

  /*
   * Handle to the external process
   */
  struct GNUNET_OS_CommandHandle *ext_cmd;

  /*
   * Did we already receive a value
   * from the currently running external
   * proccess ? #GNUNET_YES / #GNUNET_NO
   */
  int ext_cmd_value_received;

  /*
   * The output datatype to be expected
   */
  char *expected_datatype;

  /*
   * Peer-identity of peer running collection point
   */
  struct GNUNET_PeerIdentity *collection_point;

  /*
   * Time interval to send sensor information to collection point (e.g. every 30 mins)
   */
  struct GNUNET_TIME_Relative *collection_interval;

  /*
   * Flag specifying if value is to be communicated to the p2p network
   */
  int p2p_report;

  /*
   * Time interval to communicate value to the p2p network
   */
  struct GNUNET_TIME_Relative *p2p_interval;

  /*
   * Execution task (OR GNUNET_SCHEDULER_NO_TASK)
   */
  GNUNET_SCHEDULER_TaskIdentifier execution_task;

  /*
   * Is the sensor being executed
   */
  int running;

};

/**
 * Our configuration.
 */
static const struct GNUNET_CONFIGURATION_Handle *cfg;

/**
 * Hashmap of loaded sensor definitions
 */
struct GNUNET_CONTAINER_MultiHashMap *sensors;

/**
 * Supported sources of sensor information
 */
static const char *sources[] = { "gnunet-statistics", "process", NULL };

/**
 * Supported datatypes of sensor information
 */
static const char *datatypes[] = { "uint64", "double", "string", NULL };

/**
 * Handle to statistics service
 */
struct GNUNET_STATISTICS_Handle *statistics;

/**
 * Handle to peerstore service
 */
struct GNUNET_PEERSTORE_Handle *peerstore;

/**
 * Service name
 */
char *subsystem = "sensor";

/**
 * My peer id
 */
struct GNUNET_PeerIdentity peerid;

/**
 * Remove sensor execution from scheduler
 *
 * @param cls unused
 * @param key hash of sensor name, key to hashmap
 * @param value a 'struct SensorInfo *'
 * @return #GNUNET_YES if we should continue to
 *         iterate,
 *         #GNUNET_NO if not.
 */
static int destroy_sensor(void *cls,
    const struct GNUNET_HashCode *key, void *value)
{
  struct SensorInfo *sensorinfo = value;

  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Destroying sensor `%s'\n", sensorinfo->name);
  if(GNUNET_SCHEDULER_NO_TASK != sensorinfo->execution_task)
  {
    GNUNET_SCHEDULER_cancel(sensorinfo->execution_task);
    sensorinfo->execution_task = GNUNET_SCHEDULER_NO_TASK;
  }
  if(NULL != sensorinfo->gnunet_stat_get_handle)
  {
    GNUNET_STATISTICS_get_cancel(sensorinfo->gnunet_stat_get_handle);
    sensorinfo->gnunet_stat_get_handle = NULL;
  }
  if(NULL != sensorinfo->ext_cmd)
  {
    GNUNET_OS_command_stop(sensorinfo->ext_cmd);
    sensorinfo->ext_cmd = NULL;
  }
  if(NULL != sensorinfo->cfg)
    GNUNET_CONFIGURATION_destroy(sensorinfo->cfg);
  if(NULL != sensorinfo->name)
    GNUNET_free(sensorinfo->name);
  if(NULL != sensorinfo->def_file)
    GNUNET_free(sensorinfo->def_file);
  if(NULL != sensorinfo->description)
    GNUNET_free(sensorinfo->description);
  if(NULL != sensorinfo->category)
    GNUNET_free(sensorinfo->category);
  if(NULL != sensorinfo->capabilities)
    GNUNET_free(sensorinfo->capabilities);
  if(NULL != sensorinfo->gnunet_stat_service)
    GNUNET_free(sensorinfo->gnunet_stat_service);
  if(NULL != sensorinfo->gnunet_stat_name)
    GNUNET_free(sensorinfo->gnunet_stat_name);
  if(NULL != sensorinfo->ext_process)
    GNUNET_free(sensorinfo->ext_process);
  if(NULL != sensorinfo->ext_args)
    GNUNET_free(sensorinfo->ext_args);
  GNUNET_free(sensorinfo);
  return GNUNET_YES;
}

/**
 * Disable a sensor
 * Sensor will not run again unless
 * explicitly enabled or reloaded
 *
 * @param sensor sensor information
 */
static void set_sensor_enabled(struct SensorInfo *sensor, int state)
{
  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
      "Sensor `%s': Setting enabled to %d.\n",
      sensor->name, state);
  sensor->enabled = GNUNET_NO;
  GNUNET_assert(NULL != sensor->cfg);
  GNUNET_CONFIGURATION_set_value_string(sensor->cfg, sensor->name, "ENABLED",
      (GNUNET_YES == state)?"YES":"NO");
  GNUNET_CONFIGURATION_write(sensor->cfg, sensor->def_file);
}

/**
 * Task run during shutdown.
 *
 * @param cls unused
 * @param tc unused
 */
static void
shutdown_task (void *cls,
	       const struct GNUNET_SCHEDULER_TaskContext *tc)
{
  GNUNET_CONTAINER_multihashmap_iterate(sensors, &destroy_sensor, NULL);
  GNUNET_CONTAINER_multihashmap_destroy(sensors);
  if(NULL != statistics)
  {
    GNUNET_STATISTICS_destroy(statistics, GNUNET_YES);
    statistics = NULL;
  }
  if(NULL != peerstore)
  {
    GNUNET_PEERSTORE_disconnect(peerstore);
    peerstore = NULL;
  }
  GNUNET_SCHEDULER_shutdown();
}


/**
 * A client disconnected.  Remove all of its data structure entries.
 *
 * @param cls closure, NULL
 * @param client identification of the client
 */
static void
handle_client_disconnect (void *cls,
			  struct GNUNET_SERVER_Client
			  * client)
{
}

/**
 * Parses a version number string into major and minor
 *
 * @param version full version string
 * @param major pointer to parsed major value
 * @param minor pointer to parsed minor value
 * @return #GNUNET_OK if parsing went ok, #GNUNET_SYSERROR in case of error
 */
static int
version_parse(char *version, uint16_t *major, uint16_t *minor)
{
  int majorval = 0;
  int minorval = 0;

  for(; isdigit(*version); version++)
  {
    majorval *= 10;
    majorval += *version - '0';
  }
  if(*version != '.')
    return GNUNET_SYSERR;
  version++;
  for(; isdigit(*version); version++)
  {
    minorval *= 10;
    minorval += *version - '0';
  }
  if(*version != 0)
    return GNUNET_SYSERR;
  *major = majorval;
  *minor = minorval;

  return GNUNET_OK;
}

/**
 * Load sensor definition from configuration
 *
 * @param cfg configuration handle
 * @param sectionname configuration section containing definition
 */
static struct SensorInfo *
load_sensor_from_cfg(struct GNUNET_CONFIGURATION_Handle *cfg, const char *sectionname)
{
  struct SensorInfo *sensor;
  char *version_str;
  char *starttime_str;
  char *endtime_str;
  unsigned long long time_sec;

  sensor = GNUNET_new(struct SensorInfo);
  //name
  sensor->name = GNUNET_strdup(sectionname);
  //version
  if(GNUNET_OK != GNUNET_CONFIGURATION_get_value_string(cfg, sectionname, "VERSION", &version_str))
  {
    GNUNET_log(GNUNET_ERROR_TYPE_ERROR, _("Error reading sensor version\n"));
    GNUNET_free(sensor);
    return NULL;
  }
  if(GNUNET_OK != version_parse(version_str, &(sensor->version_major), &(sensor->version_minor)))
  {
    GNUNET_log(GNUNET_ERROR_TYPE_ERROR, _("Invalid sensor version number, format should be major.minor\n"));
    GNUNET_free(sensor);
    GNUNET_free(version_str);
    return NULL;
  }
  GNUNET_free(version_str);
  //description
  GNUNET_CONFIGURATION_get_value_string(cfg, sectionname, "DESCRIPTION", &sensor->description);
  //category
  if(GNUNET_OK != GNUNET_CONFIGURATION_get_value_string(cfg, sectionname, "CATEGORY", &sensor->category) ||
        NULL == sensor->category)
  {
    GNUNET_log(GNUNET_ERROR_TYPE_ERROR, _("Error reading sensor category\n"));
    GNUNET_free(sensor);
    return NULL;
  }
  //enabled
  if(GNUNET_NO == GNUNET_CONFIGURATION_get_value_yesno(cfg, sectionname, "ENABLED"))
    sensor->enabled = GNUNET_NO;
  else
    sensor->enabled = GNUNET_YES;
  //start time
  sensor->start_time = NULL;
  if(GNUNET_OK == GNUNET_CONFIGURATION_get_value_string(cfg, sectionname, "START_TIME", &starttime_str))
  {
    GNUNET_STRINGS_fancy_time_to_absolute(starttime_str, sensor->start_time);
    GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Start time loaded: `%s'. Parsed: %d\n", starttime_str, (NULL != sensor->start_time));
    GNUNET_free(starttime_str);
  }
  //end time
  sensor->end_time = NULL;
  if(GNUNET_OK == GNUNET_CONFIGURATION_get_value_string(cfg, sectionname, "END_TIME", &endtime_str))
  {
    GNUNET_STRINGS_fancy_time_to_absolute(endtime_str, sensor->end_time);
    GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "End time loaded: `%s'. Parsed: %d\n", endtime_str, (NULL != sensor->end_time));
    GNUNET_free(endtime_str);
  }
  //interval
  if(GNUNET_OK != GNUNET_CONFIGURATION_get_value_number(cfg, sectionname, "INTERVAL", &time_sec))
  {
    GNUNET_log(GNUNET_ERROR_TYPE_ERROR, _("Error reading sensor run interval\n"));
    GNUNET_free(sensor);
    return NULL;
  }
  if(time_sec < MIN_INTERVAL)
  {
    GNUNET_log(GNUNET_ERROR_TYPE_ERROR, _("Sensor run interval too low (%" PRIu64 " < %d)\n"),
        time_sec, MIN_INTERVAL);
    GNUNET_free(sensor);
    return NULL;
  }
  sensor->interval = GNUNET_TIME_relative_multiply(GNUNET_TIME_UNIT_SECONDS, time_sec);
  //lifetime
  if(GNUNET_OK == GNUNET_CONFIGURATION_get_value_number(cfg, sectionname, "LIFETIME", &time_sec))
  {
    sensor->lifetime = GNUNET_TIME_relative_multiply(GNUNET_TIME_UNIT_SECONDS, time_sec);
  }
  else
    sensor->lifetime = sensor->interval;
  //capabilities TODO
  //source
  if(GNUNET_OK != GNUNET_CONFIGURATION_get_value_choice(cfg, sectionname, "SOURCE", sources, (const char **)&sensor->source))
  {
    GNUNET_log(GNUNET_ERROR_TYPE_ERROR, _("Error reading sensor source\n"));
    GNUNET_free(sensor);
    return NULL;
  }
  if(sources[0] == sensor->source) //gnunet-statistics
  {
    if(GNUNET_OK != GNUNET_CONFIGURATION_get_value_string(cfg, sectionname, "GNUNET_STAT_SERVICE", &sensor->gnunet_stat_service) ||
        GNUNET_OK != GNUNET_CONFIGURATION_get_value_string(cfg, sectionname, "GNUNET_STAT_NAME", &sensor->gnunet_stat_name))
    {
      GNUNET_log(GNUNET_ERROR_TYPE_ERROR, _("Error reading sensor gnunet-statistics source information\n"));
      GNUNET_free(sensor);
      return NULL;
    }
    sensor->gnunet_stat_get_handle = NULL;
  }
  else if(sources[1] == sensor->source) //process
  {
    if(GNUNET_OK != GNUNET_CONFIGURATION_get_value_string(cfg, sectionname, "EXT_PROCESS", &sensor->ext_process))
    {
      GNUNET_log(GNUNET_ERROR_TYPE_ERROR, _("Error reading sensor process name\n"));
      GNUNET_free(sensor);
      return NULL;
    }
    GNUNET_CONFIGURATION_get_value_string(cfg, sectionname, "EXT_ARGS", &sensor->ext_args);
  }
  //expected datatype
  if(GNUNET_OK != GNUNET_CONFIGURATION_get_value_choice(cfg, sectionname, "EXPECTED_DATATYPE", datatypes, (const char **)&sensor->expected_datatype))
  {
    GNUNET_log(GNUNET_ERROR_TYPE_ERROR, _("Error reading sensor expected datatype\n"));
    GNUNET_free(sensor);
    return NULL;
  }
  if(sources[0] == sensor->source && datatypes[0] != sensor->expected_datatype)
  {
    GNUNET_log(GNUNET_ERROR_TYPE_ERROR, _("Invalid expected datatype, gnunet-statistics returns uint64 values\n"));
    GNUNET_free(sensor);
    return NULL;
  }
  //TODO: reporting mechanism
  //execution task
  sensor->execution_task = GNUNET_SCHEDULER_NO_TASK;
  //running
  sensor->running = GNUNET_NO;

  return sensor;
}

/**
 * Load sensor definition from file
 *
 * @param filename full path to file containing sensor definition
 */
static struct SensorInfo *
load_sensor_from_file(const char *filename)
{
  struct GNUNET_CONFIGURATION_Handle *sensorcfg;
  const char *filebasename;
  struct SensorInfo *sensor;

  //test file
  if(GNUNET_YES != GNUNET_DISK_file_test(filename))
  {
    GNUNET_log(GNUNET_ERROR_TYPE_ERROR, _("Failed to access sensor file: %s\n"), filename);
    return NULL;
  }
  //load file as configuration
  sensorcfg = GNUNET_CONFIGURATION_create();
  if(GNUNET_SYSERR == GNUNET_CONFIGURATION_parse(sensorcfg, filename))
  {
    GNUNET_CONFIGURATION_destroy(sensorcfg);
    GNUNET_log(GNUNET_ERROR_TYPE_ERROR, _("Failed to load sensor definition: %s\n"), filename);
    return NULL;
  }
  //configuration section should be the same as filename
  filebasename = GNUNET_STRINGS_get_short_name(filename);
  sensor = load_sensor_from_cfg(sensorcfg, filebasename);
  if(NULL == sensor)
  {
    GNUNET_CONFIGURATION_destroy(sensorcfg);
    return NULL;
  }
  sensor->def_file = GNUNET_strdup(filename);
  sensor->cfg = sensorcfg;

  return sensor;
}

/**
 * Compares version numbers of two sensors
 *
 * @param s1 first sensor
 * @param s2 second sensor
 * @return 1: s1 > s2, 0: s1 == s2, -1: s1 < s2
 */
static int
sensor_version_compare(struct SensorInfo *s1, struct SensorInfo *s2)
{
  if(s1->version_major == s2->version_major)
    return (s1->version_minor < s2->version_minor) ? -1 : (s1->version_minor > s2->version_minor);
  else
    return (s1->version_major < s2->version_major) ? -1 : (s1->version_major > s2->version_major);
}

/**
 * Adds a new sensor to given hashmap.
 * If the same name exist, compares versions and update if old.
 *
 * @param sensor Sensor structure to add
 * @param map Hashmap to add to
 * @return #GNUNET_YES if added, #GNUNET_NO if not added which is not necessarily an error
 */
static int
add_sensor_to_hashmap(struct SensorInfo *sensor, struct GNUNET_CONTAINER_MultiHashMap *map)
{
  struct GNUNET_HashCode key;
  struct SensorInfo *existing;

  GNUNET_CRYPTO_hash(sensor->name, strlen(sensor->name), &key);
  existing = GNUNET_CONTAINER_multihashmap_get(map, &key);
  if(NULL != existing) //sensor with same name already exists
  {
    if(sensor_version_compare(existing, sensor) >= 0) //same or newer version already exist
    {
      GNUNET_log(GNUNET_ERROR_TYPE_INFO, _("Sensor `%s' already exists with same or newer version\n"), sensor->name);
      return GNUNET_NO;
    }
    else
    {
      GNUNET_CONTAINER_multihashmap_remove(map, &key, existing); //remove the old version
      GNUNET_free(existing);
      GNUNET_log(GNUNET_ERROR_TYPE_INFO, "Upgrading sensor `%s' to a newer version\n", sensor->name);
    }
  }
  if(GNUNET_SYSERR == GNUNET_CONTAINER_multihashmap_put(map, &key, sensor, GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY))
  {
    GNUNET_log(GNUNET_ERROR_TYPE_ERROR, _("Error adding new sensor `%s' to global hashmap, this should not happen\n"), sensor->name);
    return GNUNET_NO;
  }

  return GNUNET_YES;
}

/**
 * Iterating over files in sensors directory
 *
 * @param cls closure
 * @param filename complete filename (absolute path)
 * @return #GNUNET_OK to continue to iterate
 */
static int
reload_sensors_dir_cb(void *cls, const char *filename)
{
  struct SensorInfo *sensor;

  if(GNUNET_YES != GNUNET_DISK_file_test(filename))
    return GNUNET_OK;
  sensor = load_sensor_from_file(filename);
  if(NULL == sensor)
  {
    GNUNET_log(GNUNET_ERROR_TYPE_ERROR, _("Error loading sensor from file: %s\n"), filename);
    return GNUNET_OK;
  }
  if(GNUNET_YES == add_sensor_to_hashmap(sensor, sensors))
    GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, _("Sensor `%s' added to global hashmap\n"), sensor->name);
  else
    GNUNET_log(GNUNET_ERROR_TYPE_WARNING, ("Could not add sensor `%s' to global hashmap\n"), sensor->name);

  return GNUNET_OK;
}

/*
 * Get path to the directory containing the sensor definition files
 *
 * @return sensor files directory
 */
static char *
get_sensor_dir()
{
  char* datadir;
  char* sensordir;

  datadir = GNUNET_OS_installation_get_path(GNUNET_OS_IPK_DATADIR);
  GNUNET_asprintf(&sensordir, "%ssensors%s",
      datadir, DIR_SEPARATOR_STR);
  GNUNET_free(datadir);

  return sensordir;
}

/**
 * Reads sensor definitions from data files
 *
 */
static void
reload_sensors()
{
  char* sensordir;

  sensordir = get_sensor_dir();
  GNUNET_log(GNUNET_ERROR_TYPE_INFO, _("Reloading sensor definitions from directory `%s'\n"), sensordir);
  GNUNET_assert(GNUNET_YES == GNUNET_DISK_directory_test(sensordir, GNUNET_YES));

  //read all files in sensors directory
  GNUNET_DISK_directory_scan(sensordir, &reload_sensors_dir_cb, NULL);
  GNUNET_log(GNUNET_ERROR_TYPE_INFO, _("Loaded %d sensors from directory `%s'\n"),
      GNUNET_CONTAINER_multihashmap_size(sensors), sensordir);
  GNUNET_free(sensordir);
}

/**
 * Creates a structure with basic sensor info to be sent to a client
 *
 * @param sensor sensor information
 * @return message ready to be sent to client
 */
static struct SensorInfoMessage *
create_sensor_info_msg(struct SensorInfo *sensor)
{
  struct SensorInfoMessage *msg;
  uint16_t len;
  size_t name_len;
  size_t desc_len;
  char *str_ptr;

  name_len = strlen(sensor->name);
  if(NULL == sensor->description)
    desc_len = 0;
  else
    desc_len = strlen(sensor->description) + 1;
  len = 0;
  len += sizeof(struct SensorInfoMessage);
  len += name_len;
  len += desc_len;
  msg = GNUNET_malloc(len);
  msg->header.size = htons(len);
  msg->header.type = htons(GNUNET_MESSAGE_TYPE_SENSOR_INFO);
  msg->name_len = htons(name_len);
  msg->description_len = htons(desc_len);
  msg->version_major = htons(sensor->version_major);
  msg->version_minor = htons(sensor->version_minor);
  str_ptr = (char*) &msg[1];
  memcpy(str_ptr, sensor->name, name_len);
  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Sending sensor name (%d): %.*s\n",
        name_len, name_len, str_ptr);
  str_ptr += name_len;
  memcpy(str_ptr, sensor->description, desc_len);
  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Sending sensor description (%d): %.*s\n",
          desc_len, desc_len, str_ptr);

  return msg;
}

/**
 * Handle GET SENSOR message.
 *
 * @param cls closure
 * @param client identification of the client
 * @param message the actual message
 */
static void
handle_get_sensor (void *cls, struct GNUNET_SERVER_Client *client,
            const struct GNUNET_MessageHeader *message)
{
  struct GNUNET_SERVER_TransmitContext *tc;
  char *sensorname;
  size_t sensorname_len;
  struct GNUNET_HashCode key;
  struct SensorInfo *sensorinfo;
  struct SensorInfoMessage *msg;

  sensorname = (char *)&message[1];
  sensorname_len = ntohs(message->size) - sizeof(struct GNUNET_MessageHeader);
  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "`%s' message received for sensor (%d) `%.*s'\n",
              "GET SENSOR", sensorname_len, sensorname_len, sensorname);
  tc = GNUNET_SERVER_transmit_context_create (client);
  GNUNET_CRYPTO_hash(sensorname, sensorname_len, &key);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Created key hash for requested sensor\n");
  sensorinfo = (struct SensorInfo *)GNUNET_CONTAINER_multihashmap_get(sensors, &key);
  if(NULL != sensorinfo)
  {
    msg = create_sensor_info_msg(sensorinfo);
    GNUNET_SERVER_transmit_context_append_message(tc, (struct GNUNET_MessageHeader *)msg);
    GNUNET_free(msg);
  }
  else
    GNUNET_log(GNUNET_ERROR_TYPE_WARNING, "Requested sensor `%.*s' was not found\n",
        sensorname_len, sensorname);
  GNUNET_SERVER_transmit_context_append_data(tc, NULL, 0, GNUNET_MESSAGE_TYPE_SENSOR_END);
  GNUNET_SERVER_transmit_context_run (tc, GNUNET_TIME_UNIT_FOREVER_REL);
}

/**
 * Iterator for sensors and adds them to transmit context
 *
 * @param cls a 'struct GNUNET_SERVER_TransmitContext *'
 * @param key hash of sensor name, key to hashmap
 * @param value a 'struct SensorInfo *'
 */
int add_sensor_to_tc(void *cls,
    const struct GNUNET_HashCode *key, void *value)
{
  struct GNUNET_SERVER_TransmitContext *tc = cls;
  struct SensorInfo *sensorinfo = value;
  struct SensorInfoMessage *msg;

  msg = create_sensor_info_msg(sensorinfo);
  GNUNET_SERVER_transmit_context_append_message(tc, (struct GNUNET_MessageHeader *)msg);

  GNUNET_free(msg);

  return GNUNET_YES;
}

/**
 * Handle GET ALL SENSORS message.
 *
 * @param cls closure
 * @param client identification of the client
 * @param message the actual message
 */
static void
handle_get_all_sensors (void *cls, struct GNUNET_SERVER_Client *client,
            const struct GNUNET_MessageHeader *message)
{
  struct GNUNET_SERVER_TransmitContext *tc;

  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "`%s' message received.\n",
                "GET ALL SENSOR");
  tc = GNUNET_SERVER_transmit_context_create (client);
  GNUNET_CONTAINER_multihashmap_iterate(sensors, &add_sensor_to_tc, tc);
  GNUNET_SERVER_transmit_context_append_data(tc, NULL, 0, GNUNET_MESSAGE_TYPE_SENSOR_END);
  GNUNET_SERVER_transmit_context_run (tc, GNUNET_TIME_UNIT_FOREVER_REL);
}

/**
 * Do a series of checks to determine if sensor should execute
 *
 * @return #GNUNET_YES / #GNUNET_NO
 */
static int
should_run_sensor(struct SensorInfo *sensorinfo)
{
  struct GNUNET_TIME_Absolute now;

  if(GNUNET_NO == sensorinfo->enabled)
  {
    GNUNET_log(GNUNET_ERROR_TYPE_INFO, "Sensor `%s' is disabled, will not run\n", sensorinfo->name);
    return GNUNET_NO;
  }
  now = GNUNET_TIME_absolute_get();
  if(NULL != sensorinfo->start_time
      && now.abs_value_us < sensorinfo->start_time->abs_value_us)
  {
    GNUNET_log(GNUNET_ERROR_TYPE_INFO, "Start time for sensor `%s' not reached yet, will not run\n", sensorinfo->name);
    return GNUNET_NO;
  }
  if(NULL != sensorinfo->end_time
      && now.abs_value_us >= sensorinfo->end_time->abs_value_us)
  {
    GNUNET_log(GNUNET_ERROR_TYPE_INFO, "Sensor `%s' expired, disabling.\n", sensorinfo->name);
    set_sensor_enabled(sensorinfo, GNUNET_NO);
    return GNUNET_NO;
  }
  return GNUNET_YES;
}

/**
 * Callback function to process statistic values
 *
 * @param cls 'struct SensorInfo *'
 * @param subsystem name of subsystem that created the statistic
 * @param name the name of the datum
 * @param value the current value
 * @param is_persistent #GNUNET_YES if the value is persistent, #GNUNET_NO if not
 * @return #GNUNET_OK to continue, #GNUNET_SYSERR to abort iteration
 */
int sensor_statistics_iterator (void *cls,
    const char *ss,
    const char *name,
    uint64_t value,
    int is_persistent)
{
  struct SensorInfo *sensorinfo = cls;
  struct GNUNET_TIME_Absolute expiry;

  GNUNET_log(GNUNET_ERROR_TYPE_INFO, "Received a value for sensor `%s': %" PRIu64 "\n", sensorinfo->name, value);
  expiry = GNUNET_TIME_relative_to_absolute(sensorinfo->lifetime);
  GNUNET_PEERSTORE_store(peerstore,
      subsystem,
      &peerid,
      sensorinfo->name,
      &value,
      sizeof(value),
      expiry,
      GNUNET_PEERSTORE_STOREOPTION_MULTIPLE,
      NULL,
      NULL);
  return GNUNET_SYSERR; /* We only want one value */
}

/**
 * Continuation called after sensor gets all gnunet statistics values
 *
 * @param cls 'struct SensorInfo *'
 * @param success #GNUNET_OK if statistics were
 *        successfully obtained, #GNUNET_SYSERR if not.
 */
void end_sensor_run_stat (void *cls, int success)
{
  struct SensorInfo *sensorinfo = cls;

  sensorinfo->gnunet_stat_get_handle = NULL;
  sensorinfo->running = GNUNET_NO;
}

/**
 * Tries to parse a received sensor value to its
 * expected datatype
 *
 * @param value the string value received, should be null terminated
 * @param sensor sensor information struct
 * @param ret pointer to parsed value
 * @return size of new parsed value, 0 for error
 */
static size_t
parse_sensor_value (const char *value, struct SensorInfo* sensor, void **ret)
{
  uint64_t *ullval;
  double *dval;
  char *endptr;

  *ret = NULL;
  if ('\0' == *value)
    return 0;
  //"uint64", "double", "string"
  if (0 == strcmp("uint64", sensor->expected_datatype))
  {
    ullval = GNUNET_new(uint64_t);
    *ullval = strtoull(value, &endptr, 10);
    if ('\0' != *endptr &&
        '\n' != *endptr) /* Invalid string */
      return 0;
    *ret = ullval;
    return sizeof(uint64_t);
  }
  if(0 == strcmp("double", sensor->expected_datatype))
  {
    dval = GNUNET_new(double);
    *dval = strtod(value, &endptr);
    if(value == endptr)
      return 0;
   *ret = dval;
   return sizeof(double);
  }
  if(0 == strcmp("string", sensor->expected_datatype))
  {
    *ret = GNUNET_strdup(value);
    return strlen(value) + 1;
  }
  GNUNET_log(GNUNET_ERROR_TYPE_ERROR,
      _("Unknown value type expected by sensor, this should not happen.\n"));
  return 0;
}

/**
 * Callback for output of executed sensor process
 *
 * @param cls 'struct SensorInfo *'
 * @param line line of output from a command, NULL for the end
 */
void sensor_process_callback (void *cls, const char *line)
{
  struct SensorInfo *sensorinfo = cls;
  void *value;
  size_t valsize;
  struct GNUNET_TIME_Absolute expiry;

  if(NULL == line)
  {
    GNUNET_OS_command_stop(sensorinfo->ext_cmd);
    sensorinfo->ext_cmd = NULL;
    sensorinfo->running = GNUNET_NO;
    sensorinfo->ext_cmd_value_received = GNUNET_NO;
    return;
  }
  if(GNUNET_YES == sensorinfo->ext_cmd_value_received)
    return; /* We only want one *valid* value */
  GNUNET_log(GNUNET_ERROR_TYPE_INFO, "Received a value for sensor `%s': %s\n", sensorinfo->name, line);
  valsize = parse_sensor_value(line, sensorinfo, &value);
  if (valsize == 0) /* invalid value, FIXME: should we disable the sensor now? */
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
        _("Received an invalid value for sensor `%s': %s\n"),
        sensorinfo->name, line);
  }
  else
  {
    sensorinfo->ext_cmd_value_received = GNUNET_YES;
    expiry = GNUNET_TIME_relative_to_absolute(sensorinfo->lifetime);
    GNUNET_PEERSTORE_store(peerstore,
        subsystem,
        &peerid,
        sensorinfo->name,
        value,
        valsize,
        expiry,
        GNUNET_PEERSTORE_STOREOPTION_MULTIPLE,
        NULL,
        NULL);
  }
}

/**
 * Checks if the given file is a path
 *
 * @return #GNUNET_YES / #GNUNET_NO
 */
static int
is_path(char *filename)
{
  size_t filename_len;
  int i;

  filename_len = strlen(filename);
  for(i = 0; i < filename_len; i++)
  {
    if(DIR_SEPARATOR == filename[i])
      return GNUNET_YES;
  }
  return GNUNET_NO;
}

/**
 * Actual execution of a sensor
 *
 * @param cls 'struct SensorInfo'
 * @param tc unsed
 */
void
sensor_run (void *cls,
    const struct GNUNET_SCHEDULER_TaskContext * tc)
{
  struct SensorInfo *sensorinfo = cls;
  int check_result;
  char *sensors_dir;
  char *process_path;

  sensorinfo->execution_task = GNUNET_SCHEDULER_add_delayed(sensorinfo->interval, &sensor_run, sensorinfo);
  if(GNUNET_YES == sensorinfo->running) //FIXME: should we try to kill?
  {
    GNUNET_log(GNUNET_ERROR_TYPE_WARNING, "Sensor `%s' running for too long, will try again next interval\n", sensorinfo->name);
    return;
  }
  if(GNUNET_NO == should_run_sensor(sensorinfo))
    return;
  sensorinfo->running = GNUNET_YES;
  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Starting the execution of sensor `%s'\n", sensorinfo->name);
  if(sources[0] == sensorinfo->source) //gnunet-statistics
  {
    sensorinfo->gnunet_stat_get_handle = GNUNET_STATISTICS_get(statistics,
        sensorinfo->gnunet_stat_service,
        sensorinfo->gnunet_stat_name,
        sensorinfo->interval, //try to get values only for the interval of the sensor
        &end_sensor_run_stat,
        &sensor_statistics_iterator,
        sensorinfo);
  }
  else if(sources[1] == sensorinfo->source)
  {
    if(GNUNET_YES == is_path(sensorinfo->ext_process))
    {
      GNUNET_log(GNUNET_ERROR_TYPE_ERROR,
          _("Sensor `%s': External process should not be a path, disabling sensor.\n"),
          sensorinfo->name);
      set_sensor_enabled(sensorinfo, GNUNET_NO);
      return;
    }
    //check if the process exists in $PATH
    process_path = GNUNET_strdup(sensorinfo->ext_process);
    check_result =
        GNUNET_OS_check_helper_binary(process_path, GNUNET_NO, NULL);
    if(GNUNET_SYSERR == check_result)
    {
      //search in sensor directory
      sensors_dir = get_sensor_dir();
      GNUNET_free(process_path);
      GNUNET_asprintf(&process_path, "%s%s-files%s%s",
          sensors_dir,
          sensorinfo->name,
          DIR_SEPARATOR_STR,
          sensorinfo->ext_process);
      GNUNET_free(sensors_dir);
      check_result =
        GNUNET_OS_check_helper_binary(process_path, GNUNET_NO, NULL);
    }
    if(GNUNET_SYSERR == check_result)
    {
      GNUNET_log(GNUNET_ERROR_TYPE_ERROR,
          _("Sensor `%s' process `%s' problem: binary doesn't exist or not executable\n"),
          sensorinfo->name,
          sensorinfo->ext_process);
      set_sensor_enabled(sensorinfo, GNUNET_NO);
      sensorinfo->running = GNUNET_NO;
      GNUNET_free(process_path);
      return;
    }
    sensorinfo->ext_cmd_value_received = GNUNET_NO;
    sensorinfo->ext_cmd = GNUNET_OS_command_run(&sensor_process_callback,
        sensorinfo,
        GNUNET_TIME_UNIT_FOREVER_REL,
        process_path,
        sensorinfo->ext_process,
        sensorinfo->ext_args,
        NULL);
    GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Process started for sensor `%s'\n", sensorinfo->name);
    GNUNET_free(process_path);
  }
  else
  {
    sensorinfo->running = GNUNET_NO;
    GNUNET_break(0); //shouldn't happen
  }
}

/**
 * Starts the execution of a sensor
 *
 * @param cls unused
 * @param key hash of sensor name, key to hashmap (unused)
 * @param value a 'struct SensorInfo *'
 * @return #GNUNET_YES if we should continue to
 *         iterate,
 *         #GNUNET_NO if not.
 */
int schedule_sensor(void *cls,
    const struct GNUNET_HashCode *key, void *value)
{
  struct SensorInfo *sensorinfo = value;

  if(GNUNET_NO == should_run_sensor(sensorinfo))
    return GNUNET_YES;
  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Scheduling sensor `%s' to run after %" PRIu64 " microseconds\n",
      sensorinfo->name, sensorinfo->interval.rel_value_us);
  if(GNUNET_SCHEDULER_NO_TASK != sensorinfo->execution_task)
  {
    GNUNET_log(GNUNET_ERROR_TYPE_ERROR,
        _("Sensor `%s' execution task already set, this should not happen\n"), sensorinfo->name);
    return GNUNET_NO;
  }
  sensorinfo->execution_task = GNUNET_SCHEDULER_add_delayed(sensorinfo->interval, &sensor_run, sensorinfo);
  return GNUNET_YES;
}

/**
 * Starts the execution of all enabled sensors
 *
 */
static void
schedule_all_sensors()
{
  GNUNET_CONTAINER_multihashmap_iterate(sensors, &schedule_sensor, NULL);
}

/**
 * Process statistics requests.
 *
 * @param cls closure
 * @param server the initialized server
 * @param c configuration to use
 */
static void
run (void *cls,
     struct GNUNET_SERVER_Handle *server,
     const struct GNUNET_CONFIGURATION_Handle *c)
{
  static const struct GNUNET_SERVER_MessageHandler handlers[] = {
    {&handle_get_sensor, NULL, GNUNET_MESSAGE_TYPE_SENSOR_GET,
     0},
    {&handle_get_all_sensors, NULL, GNUNET_MESSAGE_TYPE_SENSOR_GETALL,
     sizeof (struct GNUNET_MessageHeader)},
    {NULL, NULL, 0, 0}
  };

  cfg = c;
  sensors = GNUNET_CONTAINER_multihashmap_create(10, GNUNET_NO);
  reload_sensors();
  schedule_all_sensors();
  statistics = GNUNET_STATISTICS_create("sensor", cfg);
  GNUNET_CRYPTO_get_peer_identity(cfg, &peerid);
  peerstore = GNUNET_PEERSTORE_connect(cfg);
  GNUNET_SERVER_add_handlers (server, handlers);
  GNUNET_SERVER_disconnect_notify (server, 
				   &handle_client_disconnect,
				   NULL);
  GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_FOREVER_REL,
				&shutdown_task,
				NULL);
}


/**
 * The main function for the sensor service.
 *
 * @param argc number of arguments from the command line
 * @param argv command line arguments
 * @return 0 ok, 1 on error
 */
int
main (int argc, char *const *argv)
{
  return (GNUNET_OK ==
          GNUNET_SERVICE_run (argc,
                              argv,
                              "sensor",
			      GNUNET_SERVICE_OPTION_NONE,
			      &run, NULL)) ? 0 : 1;
}

/* end of gnunet-service-sensor.c */