gnunet-service-transport_validation.c

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/*
     This file is part of GNUnet.
     Copyright (C) 2010-2015 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
 */

#include "platform.h"
#include "gnunet-service-transport_ats.h"
#include "gnunet-service-transport_hello.h"
#include "gnunet-service-transport_neighbours.h"
#include "gnunet-service-transport_plugins.h"
#include "gnunet-service-transport_validation.h"
#include "gnunet-service-transport.h"
#include "gnunet_hello_lib.h"
#include "gnunet_ats_service.h"
#include "gnunet_peerinfo_service.h"
#include "gnunet_signatures.h"

enum GNUNET_TRANSPORT_ValidationState {
  GNUNET_TRANSPORT_VS_NONE,

  GNUNET_TRANSPORT_VS_NEW,

  GNUNET_TRANSPORT_VS_UPDATE,

  GNUNET_TRANSPORT_VS_TIMEOUT,

  GNUNET_TRANSPORT_VS_REMOVE
};




#define PONG_SIGNATURE_LIFETIME GNUNET_TIME_relative_multiply(GNUNET_TIME_UNIT_HOURS, 1)

#define HELLO_ADDRESS_EXPIRATION GNUNET_TIME_relative_multiply(GNUNET_TIME_UNIT_HOURS, 12)

#define UNVALIDATED_PING_KEEPALIVE GNUNET_TIME_relative_multiply(GNUNET_TIME_UNIT_MINUTES, 5)

#define VALIDATED_PING_FREQUENCY GNUNET_TIME_relative_multiply(GNUNET_TIME_UNIT_MINUTES, 15)

#define CONNECTED_PING_FREQUENCY GNUNET_TIME_relative_multiply(GNUNET_TIME_UNIT_MINUTES, 2)

#define ACCEPTABLE_PING_DELAY GNUNET_TIME_relative_multiply(GNUNET_TIME_UNIT_SECONDS, 1)

#define VALIDATION_MAP_SIZE 256

#define PING_PRIORITY 2

#define PONG_PRIORITY 4


GNUNET_NETWORK_STRUCT_BEGIN

struct TransportPingMessage {
  struct GNUNET_MessageHeader header;

  uint32_t challenge GNUNET_PACKED;

  struct GNUNET_PeerIdentity target;
};


struct TransportPongMessage {
  struct GNUNET_MessageHeader header;

  uint32_t challenge GNUNET_PACKED;

  struct GNUNET_CRYPTO_EddsaSignature signature;

  struct GNUNET_CRYPTO_EccSignaturePurpose purpose;

  struct GNUNET_TIME_AbsoluteNBO expiration;

  uint32_t addrlen GNUNET_PACKED;
};
GNUNET_NETWORK_STRUCT_END

struct ValidationEntry {
  struct GNUNET_HELLO_Address *address;

  struct GST_BlacklistCheck *bc;

  struct GNUNET_CRYPTO_EddsaSignature pong_sig_cache;

  struct GNUNET_SCHEDULER_Task *timeout_task;

  struct GNUNET_SCHEDULER_Task *revalidation_task;

  struct GNUNET_TIME_Absolute send_time;

  struct GNUNET_TIME_Absolute next_validation;

  struct GNUNET_TIME_Absolute valid_until;

  struct GNUNET_TIME_Absolute pong_sig_valid_until;

  struct GNUNET_TIME_Absolute revalidation_block;

  struct GNUNET_TIME_Relative latency;

  enum GNUNET_TRANSPORT_ValidationState state;

  uint32_t challenge;

  int copied;

  int in_use;

  int expecting_pong;

  int known_to_ats;

  enum GNUNET_NetworkType network;
};


static struct GNUNET_CONTAINER_MultiPeerMap *validation_map;

static struct GNUNET_PEERINFO_NotifyContext *pnc;

static struct GNUNET_TIME_Relative validation_delay;

static unsigned int validations_running;

static unsigned int validations_fast_start_threshold;

static struct GNUNET_TIME_Absolute validation_next;


struct ValidationEntryMatchContext {
  struct ValidationEntry *ve;

  const struct GNUNET_HELLO_Address *address;
};


static void
publish_ve_stat_update()
{
  GNUNET_STATISTICS_set(GST_stats,
                        gettext_noop("# Addresses in validation map"),
                        GNUNET_CONTAINER_multipeermap_size(validation_map),
                        GNUNET_NO);
}


static int
validation_entry_match(void *cls,
                       const struct GNUNET_PeerIdentity *key,
                       void *value)
{
  struct ValidationEntryMatchContext *vemc = cls;
  struct ValidationEntry *ve = value;

  if (0 == GNUNET_HELLO_address_cmp(ve->address,
                                    vemc->address))
    {
      vemc->ve = ve;
      return GNUNET_NO;
    }
  return GNUNET_YES;
}


static void
validation_entry_changed(struct ValidationEntry *ve,
                         enum GNUNET_TRANSPORT_ValidationState state)
{
  ve->state = state;
}


static int
cleanup_validation_entry(void *cls,
                         const struct GNUNET_PeerIdentity *key,
                         void *value)
{
  struct ValidationEntry *ve = value;

  ve->next_validation = GNUNET_TIME_UNIT_ZERO_ABS;
  ve->valid_until = GNUNET_TIME_UNIT_ZERO_ABS;

  /* Notify about deleted entry */
  validation_entry_changed(ve,
                           GNUNET_TRANSPORT_VS_REMOVE);

  if (NULL != ve->bc)
    {
      GST_blacklist_test_cancel(ve->bc);
      ve->bc = NULL;
    }
  GNUNET_break(GNUNET_OK ==
               GNUNET_CONTAINER_multipeermap_remove(validation_map,
                                                    &ve->address->peer,
                                                    ve));
  publish_ve_stat_update();
  if (GNUNET_YES == ve->known_to_ats)
    {
      GST_ats_expire_address(ve->address);
      GNUNET_assert(GNUNET_NO ==
                    GST_ats_is_known_no_session(ve->address));
      ve->known_to_ats = GNUNET_NO;
    }
  GNUNET_HELLO_address_free(ve->address);
  if (NULL != ve->timeout_task)
    {
      GNUNET_SCHEDULER_cancel(ve->timeout_task);
      ve->timeout_task = NULL;
    }
  if (NULL != ve->revalidation_task)
    {
      GNUNET_SCHEDULER_cancel(ve->revalidation_task);
      ve->revalidation_task = NULL;
    }
  if ((GNUNET_YES == ve->expecting_pong) &&
      (validations_running > 0))
    {
      validations_running--;
      GNUNET_STATISTICS_set(GST_stats,
                            gettext_noop("# validations running"),
                            validations_running,
                            GNUNET_NO);
    }
  GNUNET_free(ve);
  return GNUNET_OK;
}


static void
timeout_hello_validation(void *cls)
{
  struct ValidationEntry *ve = cls;
  struct GNUNET_TIME_Absolute max;
  struct GNUNET_TIME_Relative left;

  ve->timeout_task = NULL;
  /* For valid addresses, we want to wait until the expire;
     for addresses under PING validation, we want to wait
     until we give up on the PING */
  max = GNUNET_TIME_absolute_max(ve->valid_until,
                                 ve->revalidation_block);
  left = GNUNET_TIME_absolute_get_remaining(max);
  if (left.rel_value_us > 0)
    {
      /* We should wait a bit longer. This happens when
         address lifetimes are extended due to successful
         validations. */
      ve->timeout_task =
        GNUNET_SCHEDULER_add_delayed(left,
                                     &timeout_hello_validation,
                                     ve);
      return;
    }
  GNUNET_STATISTICS_update(GST_stats,
                           gettext_noop("# address records discarded (timeout)"),
                           1,
                           GNUNET_NO);
  cleanup_validation_entry(NULL,
                           &ve->address->peer,
                           ve);
}


static void
transmit_ping_if_allowed(void *cls,
                         const struct GNUNET_PeerIdentity *pid,
                         const struct GNUNET_HELLO_Address *address_null,
                         struct GNUNET_ATS_Session *session_null,
                         int result)
{
  struct ValidationEntry *ve = cls;
  struct TransportPingMessage ping;
  struct GNUNET_TRANSPORT_PluginFunctions *papi;
  struct GNUNET_TIME_Absolute next;
  const struct GNUNET_MessageHeader *hello;
  ssize_t ret;
  size_t tsize;
  size_t slen;
  uint16_t hsize;
  struct GNUNET_ATS_Session *session;

  ve->bc = NULL;
  if (GNUNET_OK != result)
    {
      GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
                 "Blacklist denies sending PING to `%s' `%s' `%s'\n",
                 GNUNET_i2s(pid),
                 GST_plugins_a2s(ve->address),
                 ve->address->transport_name);
      GNUNET_STATISTICS_update(GST_stats,
                               gettext_noop("# address records discarded (blacklist)"),
                               1,
                               GNUNET_NO);
      cleanup_validation_entry(NULL,
                               pid,
                               ve);
      return;
    }
  hello = GST_hello_get();
  GNUNET_assert(NULL != hello);
  slen = strlen(ve->address->transport_name) + 1;
  hsize = ntohs(hello->size);
  tsize = sizeof(struct TransportPingMessage) +
          ve->address->address_length + slen + hsize;

  ping.header.size =
    htons(sizeof(struct TransportPingMessage) +
          ve->address->address_length + slen);
  ping.header.type = htons(GNUNET_MESSAGE_TYPE_TRANSPORT_PING);
  ping.challenge = htonl(ve->challenge);
  ping.target = *pid;

  if (tsize >= GNUNET_MAX_MESSAGE_SIZE)
    {
      GNUNET_break(0);
      hsize = 0;
      tsize =
        sizeof(struct TransportPingMessage) + ve->address->address_length +
        slen + hsize;
    }
  {
    char message_buf[tsize] GNUNET_ALIGN;

    GNUNET_memcpy(message_buf,
                  hello,
                  hsize);
    GNUNET_memcpy(&message_buf[hsize],
                  &ping,
                  sizeof(struct TransportPingMessage));
    GNUNET_memcpy(&message_buf[sizeof(struct TransportPingMessage) + hsize],
                  ve->address->transport_name,
                  slen);
    GNUNET_memcpy(&message_buf[sizeof(struct TransportPingMessage) + slen + hsize],
                  ve->address->address,
                  ve->address->address_length);
    papi = GST_plugins_find(ve->address->transport_name);
    GNUNET_assert(NULL != papi);
    session = papi->get_session(papi->cls,
                                ve->address);
    if (NULL == session)
      {
        /* Could not get a valid session */
        GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
                   "Failed to get session to send PING to `%s' at `%s'\n",
                   GNUNET_i2s(pid),
                   GST_plugins_a2s(ve->address));
        return;
      }

    ret = papi->send(papi->cls, session,
                     message_buf, tsize,
                     PING_PRIORITY,
                     ACCEPTABLE_PING_DELAY,
                     NULL, NULL);
    if (-1 == ret)
      {
        GNUNET_log(GNUNET_ERROR_TYPE_INFO,
                   "Failed to send PING to `%s' at `%s'\n",
                   GNUNET_i2s(pid),
                   GST_plugins_a2s(ve->address));
        return;
      }
    GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
               "Transmitted plain PING to `%s' `%s' `%s'\n",
               GNUNET_i2s(pid),
               GST_plugins_a2s(ve->address),
               ve->address->transport_name);
    ve->network = papi->get_network(papi->cls,
                                    session);
    GNUNET_break(GNUNET_NT_UNSPECIFIED != ve->network);
    GST_neighbours_notify_data_sent(ve->address,
                                    session,
                                    tsize);
    next = GNUNET_TIME_relative_to_absolute(validation_delay);
    validation_next = GNUNET_TIME_absolute_max(next,
                                               validation_next);
    ve->send_time = GNUNET_TIME_absolute_get();
    GNUNET_STATISTICS_update(GST_stats,
                             gettext_noop("# PINGs for address validation sent"),
                             1,
                             GNUNET_NO);
    ve->expecting_pong = GNUNET_YES;
    validations_running++;
    GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
               "Validation started, %u validation processes running\n",
               validations_running);
    GNUNET_STATISTICS_set(GST_stats,
                          gettext_noop("# validations running"),
                          validations_running,
                          GNUNET_NO);
    /*  Notify about PING sent */
    validation_entry_changed(ve,
                             GNUNET_TRANSPORT_VS_UPDATE);
  }
}


static void
revalidate_address(void *cls)
{
  struct ValidationEntry *ve = cls;
  struct GNUNET_TIME_Relative canonical_delay;
  struct GNUNET_TIME_Relative delay;
  struct GNUNET_TIME_Relative blocked_for;
  struct GST_BlacklistCheck *bc;
  uint32_t rdelay;

  ve->revalidation_task = NULL;
  delay = GNUNET_TIME_absolute_get_remaining(ve->revalidation_block);
  /* Considering current connectivity situation, what is the maximum
     block period permitted? */
  if (GNUNET_YES == ve->in_use)
    canonical_delay = CONNECTED_PING_FREQUENCY;
  else if (GNUNET_TIME_absolute_get_remaining(ve->valid_until).rel_value_us > 0)
    canonical_delay = VALIDATED_PING_FREQUENCY;
  else
    canonical_delay = UNVALIDATED_PING_KEEPALIVE;
  /* Use delay that is MIN of original delay and possibly adjusted
     new maximum delay (which may be lower); the real delay
     is originally randomized between "canonical_delay" and "2 * canonical_delay",
     so continue to permit that window for the operation. */
  delay = GNUNET_TIME_relative_min(delay,
                                   GNUNET_TIME_relative_multiply(canonical_delay,
                                                                 2));
  ve->revalidation_block = GNUNET_TIME_relative_to_absolute(delay);
  if (delay.rel_value_us > 0)
    {
      /* should wait a bit longer */
      GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
                 "Waiting for %s longer before (re)validating address `%s'\n",
                 GNUNET_STRINGS_relative_time_to_string(delay,
                                                        GNUNET_YES),
                 GST_plugins_a2s(ve->address));
      ve->revalidation_task =
        GNUNET_SCHEDULER_add_delayed(delay,
                                     &revalidate_address, ve);
      ve->next_validation = GNUNET_TIME_relative_to_absolute(delay);
      return;
    }
  /* check if globally we have too many active validations at a
     too high rate, if so, delay ours */
  blocked_for = GNUNET_TIME_absolute_get_remaining(validation_next);
  if ((validations_running > validations_fast_start_threshold) &&
      (blocked_for.rel_value_us > 0))
    {
      /* Validations are blocked, have to wait for blocked_for time */
      GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
                 "Validations blocked for another %s, delaying validating address `%s'\n",
                 GNUNET_STRINGS_relative_time_to_string(blocked_for,
                                                        GNUNET_YES),
                 GST_plugins_a2s(ve->address));
      GNUNET_STATISTICS_update(GST_stats,
                               gettext_noop("# validations delayed by global throttle"),
                               1,
                               GNUNET_NO);
      ve->revalidation_task =
        GNUNET_SCHEDULER_add_delayed(blocked_for,
                                     &revalidate_address,
                                     ve);
      ve->next_validation = GNUNET_TIME_relative_to_absolute(blocked_for);
      return;
    }

  /* We are good to go; remember to not go again for `canonical_delay` time;
     add up to `canonical_delay` to randomize start time */
  ve->revalidation_block = GNUNET_TIME_relative_to_absolute(canonical_delay);
  /* schedule next PINGing with some extra random delay to avoid synchronous re-validations */
  rdelay =
    GNUNET_CRYPTO_random_u32(GNUNET_CRYPTO_QUALITY_WEAK,
                             canonical_delay.rel_value_us);

  delay = GNUNET_TIME_relative_add(canonical_delay,
                                   GNUNET_TIME_relative_multiply
                                     (GNUNET_TIME_UNIT_MICROSECONDS,
                                     rdelay));

  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
             "Validating now, next scheduled for %s, now validating address `%s'\n",
             GNUNET_STRINGS_relative_time_to_string(blocked_for,
                                                    GNUNET_YES),
             GST_plugins_a2s(ve->address));
  ve->revalidation_task =
    GNUNET_SCHEDULER_add_delayed(delay,
                                 &revalidate_address,
                                 ve);
  ve->next_validation = GNUNET_TIME_relative_to_absolute(delay);

  /* start PINGing by checking blacklist */
  GNUNET_STATISTICS_update(GST_stats,
                           gettext_noop("# address revalidations started"), 1,
                           GNUNET_NO);
  if (NULL != ve->bc)
    {
      GST_blacklist_test_cancel(ve->bc);
      ve->bc = NULL;
    }
  bc = GST_blacklist_test_allowed(&ve->address->peer,
                                  ve->address->transport_name,
                                  &transmit_ping_if_allowed,
                                  ve,
                                  NULL,
                                  NULL);
  if (NULL != bc)
    {
      /* If transmit_ping_if_allowed was already called it may have freed ve,
       * so only set ve->bc if it has not been called.
       */
      ve->bc = bc;
    }
}


static struct ValidationEntry *
find_validation_entry(const struct GNUNET_HELLO_Address *address)
{
  struct ValidationEntryMatchContext vemc;
  struct ValidationEntry *ve;

  vemc.ve = NULL;
  vemc.address = address;
  GNUNET_CONTAINER_multipeermap_get_multiple(validation_map,
                                             &address->peer,
                                             &validation_entry_match, &vemc);
  if (NULL != (ve = vemc.ve))
    return ve;
  GNUNET_assert(GNUNET_NO ==
                GST_ats_is_known_no_session(address));
  ve = GNUNET_new(struct ValidationEntry);
  ve->in_use = GNUNET_SYSERR; /* not defined */
  ve->address = GNUNET_HELLO_address_copy(address);
  ve->pong_sig_valid_until = GNUNET_TIME_UNIT_ZERO_ABS;
  memset(&ve->pong_sig_cache,
         '\0',
         sizeof(struct GNUNET_CRYPTO_EddsaSignature));
  ve->latency = GNUNET_TIME_UNIT_FOREVER_REL;
  ve->challenge =
    GNUNET_CRYPTO_random_u32(GNUNET_CRYPTO_QUALITY_NONCE, UINT32_MAX);
  ve->timeout_task =
    GNUNET_SCHEDULER_add_delayed(UNVALIDATED_PING_KEEPALIVE,
                                 &timeout_hello_validation,
                                 ve);
  GNUNET_CONTAINER_multipeermap_put(validation_map,
                                    &address->peer,
                                    ve,
                                    GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE);
  publish_ve_stat_update();
  validation_entry_changed(ve,
                           GNUNET_TRANSPORT_VS_NEW);
  return ve;
}


static int
add_valid_address(void *cls,
                  const struct GNUNET_HELLO_Address *address,
                  struct GNUNET_TIME_Absolute expiration)
{
  const struct GNUNET_HELLO_Message *hello = cls;
  struct ValidationEntry *ve;
  struct GNUNET_PeerIdentity pid;
  struct GNUNET_ATS_Properties prop;
  struct GNUNET_TRANSPORT_PluginFunctions *papi;

  if (0 == GNUNET_TIME_absolute_get_remaining(expiration).rel_value_us)
    return GNUNET_OK;           /* expired */
  if (GNUNET_OK != GNUNET_HELLO_get_id(hello, &pid))
    {
      GNUNET_break(0);
      return GNUNET_OK;         /* invalid HELLO !? */
    }
  if (NULL == (papi = GST_plugins_find(address->transport_name)))
    {
      /* might have been valid in the past, but we don't have that
         plugin loaded right now */
      return GNUNET_OK;
    }
  if (NULL ==
      papi->address_to_string(papi->cls,
                              address->address,
                              address->address_length))
    {
      /* Why do we try to add an ill-formed address? */
      GNUNET_break(0);
      GNUNET_log(GNUNET_ERROR_TYPE_ERROR,
                 "Address with %u bytes for plugin %s and peer %s is malformed\n",
                 (unsigned int)address->address_length,
                 address->transport_name,
                 GNUNET_i2s(&pid));
      return GNUNET_OK;
    }

  ve = find_validation_entry(address);
  ve->network = papi->get_network_for_address(papi->cls,
                                              address);
  GNUNET_break(GNUNET_NT_UNSPECIFIED != ve->network);
  ve->valid_until = GNUNET_TIME_absolute_max(ve->valid_until,
                                             expiration);
  if (NULL == ve->revalidation_task)
    {
      GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
                 "Starting revalidations for valid address `%s'\n",
                 GST_plugins_a2s(ve->address));
      ve->next_validation = GNUNET_TIME_absolute_get();
      ve->revalidation_task = GNUNET_SCHEDULER_add_now(&revalidate_address, ve);
    }
  validation_entry_changed(ve,
                           GNUNET_TRANSPORT_VS_UPDATE);
  memset(&prop, 0, sizeof(prop));
  prop.scope = ve->network;
  prop.delay = GNUNET_TIME_relative_divide(ve->latency, 2);
  if (GNUNET_YES != ve->known_to_ats)
    {
      ve->known_to_ats = GNUNET_YES;
      GST_ats_add_address(address, &prop);
      GNUNET_assert(GNUNET_YES ==
                    GST_ats_is_known_no_session(ve->address));
    }
  return GNUNET_OK;
}


static void
process_peerinfo_hello(void *cls,
                       const struct GNUNET_PeerIdentity *peer,
                       const struct GNUNET_HELLO_Message *hello,
                       const char *err_msg)
{
  GNUNET_assert(NULL != peer);
  if (NULL == hello)
    return;
  if (0 == memcmp(&GST_my_identity,
                  peer,
                  sizeof(struct GNUNET_PeerIdentity)))
    {
      /* Peerinfo returned own identity, skip validation */
      return;
    }
  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
             "Handling HELLO for peer `%s'\n",
             GNUNET_i2s(peer));
  GNUNET_assert(NULL ==
                GNUNET_HELLO_iterate_addresses(hello, GNUNET_NO,
                                               &add_valid_address,
                                               (void *)hello));
}


void
GST_validation_start(unsigned int max_fds)
{
  validation_next = GNUNET_TIME_absolute_get();
  validation_delay.rel_value_us = (GNUNET_CONSTANTS_IDLE_CONNECTION_TIMEOUT.rel_value_us) / (max_fds / 2);
  validations_fast_start_threshold = (max_fds / 2);
  validations_running = 0;
  GNUNET_STATISTICS_set(GST_stats,
                        gettext_noop("# validations running"),
                        validations_running,
                        GNUNET_NO);
  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
             "Validation uses a fast start threshold of %u connections and a delay of %s\n",
             validations_fast_start_threshold,
             GNUNET_STRINGS_relative_time_to_string(validation_delay,
                                                    GNUNET_YES));
  validation_map = GNUNET_CONTAINER_multipeermap_create(VALIDATION_MAP_SIZE,
                                                        GNUNET_NO);
  pnc = GNUNET_PEERINFO_notify(GST_cfg, GNUNET_YES,
                               &process_peerinfo_hello, NULL);
}


void
GST_validation_stop()
{
  GNUNET_CONTAINER_multipeermap_iterate(validation_map,
                                        &cleanup_validation_entry,
                                        NULL);
  GNUNET_CONTAINER_multipeermap_destroy(validation_map);
  validation_map = NULL;
  GNUNET_PEERINFO_notify_cancel(pnc);
}


static void
multicast_pong(void *cls,
               struct GNUNET_TIME_Absolute valid_until,
               struct GNUNET_TIME_Absolute validation_block,
               const struct GNUNET_HELLO_Address *address)
{
  struct TransportPongMessage *pong = cls;
  struct GNUNET_TRANSPORT_PluginFunctions *papi;
  struct GNUNET_ATS_Session *session;

  papi = GST_plugins_find(address->transport_name);
  if (NULL == papi)
    {
      GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
                 "Plugin %s not supported, cannot send PONG\n",
                 address->transport_name);
      return;
    }
  GNUNET_assert(NULL != papi->send);
  GNUNET_assert(NULL != papi->get_session);
  session = papi->get_session(papi->cls, address);
  if (NULL == session)
    {
      GNUNET_break(0);
      return;
    }
  GST_ats_new_session(address, session);
  papi->send(papi->cls, session,
             (const char *)pong,
             ntohs(pong->header.size),
             PONG_PRIORITY,
             ACCEPTABLE_PING_DELAY,
             NULL, NULL);
  GST_neighbours_notify_data_sent(address,
                                  session,
                                  pong->header.size);
}


int
GST_validation_handle_ping(const struct GNUNET_PeerIdentity *sender,
                           const struct GNUNET_MessageHeader *hdr,
                           const struct GNUNET_HELLO_Address *sender_address,
                           struct GNUNET_ATS_Session *session)
{
  const struct TransportPingMessage *ping;
  struct TransportPongMessage *pong;
  struct GNUNET_TRANSPORT_PluginFunctions *papi;
  struct GNUNET_CRYPTO_EddsaSignature *sig_cache;
  struct GNUNET_TIME_Absolute *sig_cache_exp;
  const char *addr;
  const char *addrend;
  char *plugin_name;
  char *pos;
  size_t len_address;
  size_t len_plugin;
  ssize_t ret;
  struct GNUNET_HELLO_Address address;

  if (0 ==
      memcmp(&GST_my_identity,
             sender,
             sizeof(struct GNUNET_PeerIdentity)))
    return GNUNET_OK; /* our own, ignore! */
  if (ntohs(hdr->size) < sizeof(struct TransportPingMessage))
    {
      GNUNET_break_op(0);
      return GNUNET_SYSERR;
    }
  ping = (const struct TransportPingMessage *)hdr;
  if (0 !=
      memcmp(&ping->target,
             &GST_my_identity,
             sizeof(struct GNUNET_PeerIdentity)))
    {
      GNUNET_STATISTICS_update(GST_stats,
                               gettext_noop
                                 ("# PING message for different peer received"), 1,
                               GNUNET_NO);
      return GNUNET_SYSERR;
    }
  GNUNET_STATISTICS_update(GST_stats,
                           gettext_noop("# PING messages received"), 1,
                           GNUNET_NO);
  addr = (const char *)&ping[1];
  len_address = ntohs(hdr->size) - sizeof(struct TransportPingMessage);
  /* peer wants to confirm that this is one of our addresses, this is what is
   * used for address validation */

  sig_cache = NULL;
  sig_cache_exp = NULL;
  papi = NULL;
  if (len_address > 0)
    {
      addrend = memchr(addr, '\0', len_address);
      if (NULL == addrend)
        {
          GNUNET_break_op(0);
          return GNUNET_SYSERR;
        }
      addrend++;
      len_plugin = strlen(addr) + 1;
      len_address -= len_plugin;
      address.local_info = GNUNET_HELLO_ADDRESS_INFO_NONE;
      address.address = addrend;
      address.address_length = len_address;
      address.transport_name = addr;
      address.peer = GST_my_identity;

      if (NULL == address.transport_name)
        {
          GNUNET_break(0);
        }

      if (0 != strstr(address.transport_name, "_client"))
        {
          plugin_name = GNUNET_strdup(address.transport_name);
          pos = strstr(plugin_name, "_client");
          GNUNET_assert(NULL != pos);
          GNUNET_snprintf(pos, strlen("_server") + 1, "%s", "_server");
        }
      else
        plugin_name = GNUNET_strdup(address.transport_name);

      if (NULL == (papi = GST_plugins_find(plugin_name)))
        {
          /* we don't have the plugin for this address */
          GNUNET_log(GNUNET_ERROR_TYPE_INFO,
                     _("Plugin `%s' not available, cannot confirm having this address\n"),
                     plugin_name);
          GNUNET_free(plugin_name);
          return GNUNET_SYSERR;
        }
      GNUNET_free(plugin_name);
      if (GNUNET_OK !=
          papi->check_address(papi->cls,
                              addrend,
                              len_address))
        {
          GNUNET_STATISTICS_update(GST_stats,
                                   gettext_noop
                                     ("# failed address checks during validation"), 1,
                                   GNUNET_NO);
          GNUNET_log(GNUNET_ERROR_TYPE_INFO,
                     _("Address `%s' is not one of my addresses, not confirming PING\n"),
                     GST_plugins_a2s(&address));
          return GNUNET_SYSERR;
        }
      else
        {
          GNUNET_STATISTICS_update(GST_stats,
                                   gettext_noop
                                     ("# successful address checks during validation"), 1,
                                   GNUNET_NO);
          GNUNET_log(GNUNET_ERROR_TYPE_INFO,
                     "Address `%s' is one of my addresses, confirming PING\n",
                     GST_plugins_a2s(&address));
        }

      if (GNUNET_YES !=
          GST_hello_test_address(&address,
                                 &sig_cache,
                                 &sig_cache_exp))
        {
          GNUNET_log(GNUNET_ERROR_TYPE_INFO,
                     _("Not confirming PING from peer `%s' with address `%s' since I cannot confirm having this address.\n"),
                     GNUNET_i2s(sender),
                     GST_plugins_a2s(&address));
          return GNUNET_SYSERR;
        }
    }
  else
    {
      addrend = NULL;           /* make gcc happy */
      len_plugin = 0;
      static struct GNUNET_CRYPTO_EddsaSignature no_address_signature;
      static struct GNUNET_TIME_Absolute no_address_signature_expiration;

      sig_cache = &no_address_signature;
      sig_cache_exp = &no_address_signature_expiration;
    }

  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
             "I am `%s', sending PONG to peer `%s'\n",
             GNUNET_i2s_full(&GST_my_identity),
             GNUNET_i2s(sender));

  /* message with structure:
   * [TransportPongMessage][Transport name][Address] */

  pong = GNUNET_malloc(sizeof(struct TransportPongMessage) + len_address + len_plugin);
  pong->header.size =
    htons(sizeof(struct TransportPongMessage) + len_address + len_plugin);
  pong->header.type = htons(GNUNET_MESSAGE_TYPE_TRANSPORT_PONG);
  pong->purpose.size =
    htonl(sizeof(struct GNUNET_CRYPTO_EccSignaturePurpose) +
          sizeof(uint32_t) + sizeof(struct GNUNET_TIME_AbsoluteNBO) +
          len_address + len_plugin);
  pong->purpose.purpose = htonl(GNUNET_SIGNATURE_PURPOSE_TRANSPORT_PONG_OWN);
  GNUNET_memcpy(&pong->challenge, &ping->challenge, sizeof(ping->challenge));
  pong->addrlen = htonl(len_address + len_plugin);
  GNUNET_memcpy(&pong[1], addr, len_plugin);    /* Copy transport plugin */
  if (len_address > 0)
    {
      GNUNET_assert(NULL != addrend);
      GNUNET_memcpy(&((char *)&pong[1])[len_plugin], addrend, len_address);
    }
  if (GNUNET_TIME_absolute_get_remaining(*sig_cache_exp).rel_value_us <
      PONG_SIGNATURE_LIFETIME.rel_value_us / 4)
    {
      /* create / update cached sig */
      GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
                 "Creating PONG signature to indicate ownership.\n");
      *sig_cache_exp = GNUNET_TIME_relative_to_absolute(PONG_SIGNATURE_LIFETIME);
      pong->expiration = GNUNET_TIME_absolute_hton(*sig_cache_exp);
      if (GNUNET_OK !=
          GNUNET_CRYPTO_eddsa_sign(GST_my_private_key, &pong->purpose,
                                   sig_cache))
        {
          GNUNET_log(GNUNET_ERROR_TYPE_ERROR,
                     _("Failed to create PONG signature for peer `%s'\n"), GNUNET_i2s(sender));
        }
    }
  else
    {
      pong->expiration = GNUNET_TIME_absolute_hton(*sig_cache_exp);
    }
  pong->signature = *sig_cache;

  GNUNET_assert(NULL != sender_address);

  /* first see if the session we got this PING from can be used to transmit
   * a response reliably */
  if (NULL == papi)
    {
      ret = -1;
    }
  else
    {
      GNUNET_assert(NULL != papi->send);
      GNUNET_assert(NULL != papi->get_session);
      if (NULL == session)
        {
          session = papi->get_session(papi->cls, sender_address);
        }
      if (NULL == session)
        {
          GNUNET_break(0);
          ret = -1;
        }
      else
        {
          ret = papi->send(papi->cls, session,
                           (const char *)pong,
                           ntohs(pong->header.size),
                           PONG_PRIORITY, ACCEPTABLE_PING_DELAY,
                           NULL, NULL);
          if (-1 != ret)
            GST_neighbours_notify_data_sent(sender_address,
                                            session,
                                            pong->header.size);
        }
    }
  if (-1 != ret)
    {
      GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
                 "Transmitted PONG to `%s' via reliable mechanism\n",
                 GNUNET_i2s(sender));
      /* done! */
      GNUNET_STATISTICS_update(GST_stats,
                               gettext_noop
                                 ("# PONGs unicast via reliable transport"), 1,
                               GNUNET_NO);
      GNUNET_free(pong);
      return GNUNET_OK;
    }

  /* no reliable method found, try transmission via all known addresses */
  GNUNET_STATISTICS_update(GST_stats,
                           gettext_noop
                             ("# PONGs multicast to all available addresses"), 1,
                           GNUNET_NO);
  GST_validation_get_addresses(sender,
                               &multicast_pong, pong);
  GNUNET_free(pong);
  return GNUNET_OK;
}


void
GST_validation_handle_address(const struct GNUNET_HELLO_Address *address)
{
  struct GNUNET_TRANSPORT_PluginFunctions *papi;
  struct ValidationEntry *ve;

  papi = GST_plugins_find(address->transport_name);
  if (NULL == papi)
    {
      /* This plugin is currently unvailable ... ignore */
      GNUNET_log(GNUNET_ERROR_TYPE_INFO,
                 "No plugin available for %s\n",
                 address->transport_name);
      return;
    }
  ve = find_validation_entry(address);
  if (NULL == ve->revalidation_task)
    {
      GNUNET_log(GNUNET_ERROR_TYPE_INFO,
                 "Validation process started for fresh address `%s' of %s\n",
                 GST_plugins_a2s(ve->address),
                 GNUNET_i2s(&ve->address->peer));
      ve->revalidation_task = GNUNET_SCHEDULER_add_now(&revalidate_address, ve);
    }
  else
    {
      GNUNET_log(GNUNET_ERROR_TYPE_INFO,
                 "Validation already running for address `%s' of %s\n",
                 GST_plugins_a2s(ve->address),
                 GNUNET_i2s(&ve->address->peer));
    }
}


static int
validate_address_iterator(void *cls,
                          const struct GNUNET_HELLO_Address *address,
                          struct GNUNET_TIME_Absolute expiration)
{
  if (0 == GNUNET_TIME_absolute_get_remaining(expiration).rel_value_us)
    {
      GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
                 "Skipping expired address from HELLO\n");
      return GNUNET_OK;         /* expired */
    }
  GST_validation_handle_address(address);
  return GNUNET_OK;
}


static ssize_t
add_valid_peer_address(void *cls,
                       size_t max,
                       void *buf)
{
  struct ValidationEntry *ve = cls;

  if (GNUNET_YES == ve->copied)
    return GNUNET_SYSERR; /* Done */
  ve->copied = GNUNET_YES;
  return GNUNET_HELLO_add_address(ve->address,
                                  ve->valid_until,
                                  buf,
                                  max);
}


int
GST_validation_handle_pong(const struct GNUNET_PeerIdentity *sender,
                           const struct GNUNET_MessageHeader *hdr)
{
  const struct TransportPongMessage *pong;
  struct ValidationEntry *ve;
  const char *tname;
  const char *addr;
  size_t addrlen;
  size_t slen;
  size_t size;
  struct GNUNET_HELLO_Message *hello;
  struct GNUNET_HELLO_Address address;
  int sig_res;
  int do_verify;

  if (0 ==
      memcmp(&GST_my_identity,
             sender,
             sizeof(struct GNUNET_PeerIdentity)))
    return GNUNET_OK; /* our own, ignore! */

  if (ntohs(hdr->size) < sizeof(struct TransportPongMessage))
    {
      GNUNET_break_op(0);
      return GNUNET_SYSERR;
    }
  GNUNET_STATISTICS_update(GST_stats,
                           gettext_noop("# PONG messages received"), 1,
                           GNUNET_NO);

  /* message with structure:
   * [TransportPongMessage][Transport name][Address] */

  pong = (const struct TransportPongMessage *)hdr;
  tname = (const char *)&pong[1];
  size = ntohs(hdr->size) - sizeof(struct TransportPongMessage);
  addr = memchr(tname, '\0', size);
  if (NULL == addr)
    {
      GNUNET_break_op(0);
      return GNUNET_SYSERR;
    }
  addr++;
  slen = strlen(tname) + 1;
  addrlen = size - slen;

  if (NULL == GST_plugins_find(tname))
    {
      /* we got the PONG, but the transport plugin specified in it
         is not supported by this peer, so this cannot be a good
         PONG for us. */
      GNUNET_break_op(0);
      return GNUNET_OK;
    }

  address.peer = *sender;
  address.address = addr;
  address.address_length = addrlen;
  address.transport_name = tname;
  address.local_info = GNUNET_HELLO_ADDRESS_INFO_NONE;
  ve = find_validation_entry(&address);
  if ((NULL == ve) || (GNUNET_NO == ve->expecting_pong))
    {
      GNUNET_STATISTICS_update(GST_stats,
                               gettext_noop
                                 ("# PONGs dropped, no matching pending validation"),
                               1, GNUNET_NO);
      return GNUNET_OK;
    }
  /* now check that PONG is well-formed */
  if (0 != memcmp(&ve->address->peer,
                  sender,
                  sizeof(struct GNUNET_PeerIdentity)))
    {
      GNUNET_break_op(0);
      return GNUNET_SYSERR;
    }
  if (0 ==
      GNUNET_TIME_absolute_get_remaining
        (GNUNET_TIME_absolute_ntoh(pong->expiration)).rel_value_us)
    {
      GNUNET_STATISTICS_update(GST_stats,
                               gettext_noop
                                 ("# PONGs dropped, signature expired"), 1,
                               GNUNET_NO);
      return GNUNET_SYSERR;
    }

  sig_res = GNUNET_SYSERR;
  do_verify = GNUNET_YES;
  if (0 != GNUNET_TIME_absolute_get_remaining(ve->pong_sig_valid_until).rel_value_us)
    {
      /* We have a cached and valid signature for this peer,
       * try to compare instead of verify */
      if (0 == memcmp(&ve->pong_sig_cache,
                      &pong->signature,
                      sizeof(struct GNUNET_CRYPTO_EddsaSignature)))
        {
          /* signatures are identical, we can skip verification */
          sig_res = GNUNET_OK;
          do_verify = GNUNET_NO;
        }
      else
        {
          sig_res = GNUNET_SYSERR;
          /* signatures do not match, we have to verify */
        }
    }

  if (GNUNET_YES == do_verify)
    {
      /* Do expensive verification */
      sig_res = GNUNET_CRYPTO_eddsa_verify(GNUNET_SIGNATURE_PURPOSE_TRANSPORT_PONG_OWN,
                                           &pong->purpose,
                                           &pong->signature,
                                           &ve->address->peer.public_key);
      if (sig_res == GNUNET_SYSERR)
        {
          GNUNET_break_op(0);
          GNUNET_log(GNUNET_ERROR_TYPE_WARNING,
                     "Failed to verify: invalid signature on address `%s':%s from peer `%s'\n",
                     tname,
                     GST_plugins_a2s(ve->address),
                     GNUNET_i2s(sender));
        }
    }
  if (sig_res == GNUNET_SYSERR)
    {
      GNUNET_break_op(0);
      return GNUNET_SYSERR;
    }

  GNUNET_log(GNUNET_ERROR_TYPE_INFO,
             "Validation process successful for peer `%s' with plugin `%s' address `%s'\n",
             GNUNET_i2s(sender),
             tname,
             GST_plugins_a2s(ve->address));
  GNUNET_STATISTICS_update(GST_stats,
                           gettext_noop("# validations succeeded"),
                           1,
                           GNUNET_NO);
  /* validity achieved, remember it! */
  ve->expecting_pong = GNUNET_NO;
  ve->valid_until = GNUNET_TIME_relative_to_absolute(HELLO_ADDRESS_EXPIRATION);
  ve->pong_sig_cache = pong->signature;
  ve->pong_sig_valid_until = GNUNET_TIME_absolute_ntoh(pong->expiration);
  ve->latency = GNUNET_TIME_absolute_get_duration(ve->send_time);
  {
    if (GNUNET_YES == ve->known_to_ats)
      {
        GNUNET_assert(GNUNET_YES ==
                      GST_ats_is_known_no_session(ve->address));
        GST_ats_update_delay(ve->address,
                             GNUNET_TIME_relative_divide(ve->latency, 2));
      }
    else
      {
        struct GNUNET_ATS_Properties prop;

        memset(&prop, 0, sizeof(prop));
        GNUNET_break(GNUNET_NT_UNSPECIFIED != ve->network);
        prop.scope = ve->network;
        prop.delay = GNUNET_TIME_relative_divide(ve->latency, 2);
        GNUNET_assert(GNUNET_NO ==
                      GST_ats_is_known_no_session(ve->address));
        ve->known_to_ats = GNUNET_YES;
        GST_ats_add_address(ve->address, &prop);
        GNUNET_assert(GNUNET_YES ==
                      GST_ats_is_known_no_session(ve->address));
      }
  }
  if (validations_running > 0)
    {
      validations_running--;
      GNUNET_STATISTICS_set(GST_stats,
                            gettext_noop("# validations running"),
                            validations_running,
                            GNUNET_NO);
      GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
                 "Validation finished, %u validation processes running\n",
                 validations_running);
    }
  else
    {
      GNUNET_break(0);
    }

  /* Notify about new validity */
  validation_entry_changed(ve,
                           GNUNET_TRANSPORT_VS_UPDATE);

  /* build HELLO to store in PEERINFO */
  GNUNET_STATISTICS_update(GST_stats,
                           gettext_noop("# HELLOs given to peerinfo"),
                           1,
                           GNUNET_NO);
  ve->copied = GNUNET_NO;
  hello = GNUNET_HELLO_create(&ve->address->peer.public_key,
                              &add_valid_peer_address,
                              ve,
                              GNUNET_NO);
  GNUNET_break(NULL !=
               GNUNET_PEERINFO_add_peer(GST_peerinfo,
                                        hello,
                                        NULL,
                                        NULL));
  GNUNET_free(hello);
  return GNUNET_OK;
}


int
GST_validation_handle_hello(const struct GNUNET_MessageHeader *hello)
{
  const struct GNUNET_HELLO_Message *hm =
    (const struct GNUNET_HELLO_Message *)hello;
  struct GNUNET_PeerIdentity pid;
  int friend;

  friend = GNUNET_HELLO_is_friend_only(hm);
  if (((GNUNET_YES != friend) &&
       (GNUNET_NO != friend)) ||
      (GNUNET_OK != GNUNET_HELLO_get_id(hm, &pid)))
    {
      /* malformed HELLO */
      GNUNET_break_op(0);
      return GNUNET_SYSERR;
    }
  if (0 ==
      memcmp(&GST_my_identity,
             &pid,
             sizeof(struct GNUNET_PeerIdentity)))
    {
      /* got our own HELLO, how boring */
      GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
                 "Validation received our own HELLO (%s), ignoring\n",
                 GNUNET_i2s(&pid));
      return GNUNET_OK;
    }
  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
             "Validation received HELLO message for peer `%s' with size %u, checking for new addresses\n",
             GNUNET_i2s(&pid),
             ntohs(hello->size));
  GNUNET_assert(NULL ==
                GNUNET_HELLO_iterate_addresses(hm,
                                               GNUNET_NO,
                                               &validate_address_iterator,
                                               NULL));
  return GNUNET_OK;
}


struct IteratorContext {
  GST_ValidationAddressCallback cb;

  void *cb_cls;
};


static int
iterate_addresses(void *cls,
                  const struct GNUNET_PeerIdentity *key,
                  void *value)
{
  struct IteratorContext *ic = cls;
  struct ValidationEntry *ve = value;

  ic->cb(ic->cb_cls,
         ve->valid_until,
         ve->revalidation_block,
         ve->address);
  return GNUNET_OK;
}


void
GST_validation_get_addresses(const struct GNUNET_PeerIdentity *target,
                             GST_ValidationAddressCallback cb,
                             void *cb_cls)
{
  struct IteratorContext ic;

  ic.cb = cb;
  ic.cb_cls = cb_cls;
  GNUNET_CONTAINER_multipeermap_get_multiple(validation_map,
                                             target,
                                             &iterate_addresses, &ic);
}


void
GST_validation_set_address_use(const struct GNUNET_HELLO_Address *address,
                               int in_use)
{
  struct ValidationEntry *ve;

  if (GNUNET_HELLO_address_check_option(address,
                                        GNUNET_HELLO_ADDRESS_INFO_INBOUND))
    return; /* ignore inbound for validation */
  if (NULL == GST_plugins_find(address->transport_name))
    {
      /* How can we use an address for which we don't have the plugin? */
      GNUNET_break(0);
      return;
    }
  ve = find_validation_entry(address);
  if (NULL == ve)
    {
      GNUNET_break(0);
      return;
    }
  if (in_use == ve->in_use)
    return;
  ve->in_use = in_use;
  if (GNUNET_YES == in_use)
    {
      /* from now on, higher frequeny, so reschedule now */
      if (NULL != ve->revalidation_task)
        GNUNET_SCHEDULER_cancel(ve->revalidation_task);
      ve->revalidation_task = GNUNET_SCHEDULER_add_now(&revalidate_address,
                                                       ve);
    }
}


/* end of file gnunet-service-transport_validation.c */