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/*
 * This file is part of the Nice GLib ICE library.
 *
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 * (C) 2006-2009 Collabora Ltd.
 *  Contact: Youness Alaoui
 * (C) 2006-2009 Nokia Corporation. All rights reserved.
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 *  Contact: Kai Vehmanen
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is the Nice GLib ICE library.
 *
 * The Initial Developers of the Original Code are Collabora Ltd and Nokia
 * Corporation. All Rights Reserved.
 *
 * Contributors:
 *   Kai Vehmanen, Nokia
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 *   Youness Alaoui, Collabora Ltd.
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 *   Dafydd Harries, Collabora Ltd.
 *
 * Alternatively, the contents of this file may be used under the terms of the
 * the GNU Lesser General Public License Version 2.1 (the "LGPL"), in which
 * case the provisions of LGPL are applicable instead of those above. If you
 * wish to allow use of your version of this file only under the terms of the
 * LGPL and not to allow others to use your version of this file under the
 * MPL, indicate your decision by deleting the provisions above and replace
 * them with the notice and other provisions required by the LGPL. If you do
 * not delete the provisions above, a recipient may use your version of this
 * file under either the MPL or the LGPL.
 */

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/*
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 * @file conncheck.c
 * @brief ICE connectivity checks
 */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

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#include <errno.h>
#include <string.h>

#include <glib.h>

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#include "debug.h"

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#include "agent.h"
#include "agent-priv.h"
#include "conncheck.h"
#include "discovery.h"
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#include "stun/stun5389.h"
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#include "stun/usages/ice.h"
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#include "stun/usages/bind.h"
#include "stun/usages/turn.h"
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static void priv_update_check_list_failed_components (NiceAgent *agent, NiceStream *stream);
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static void priv_update_check_list_state_for_ready (NiceAgent *agent, NiceStream *stream, NiceComponent *component);
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static guint priv_prune_pending_checks (NiceStream *stream, guint component_id);
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static gboolean priv_schedule_triggered_check (NiceAgent *agent, NiceStream *stream, NiceComponent *component, NiceSocket *local_socket, NiceCandidate *remote_cand, gboolean use_candidate);
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static void priv_mark_pair_nominated (NiceAgent *agent, NiceStream *stream, NiceComponent *component, NiceCandidate *localcand, NiceCandidate *remotecand);
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static size_t priv_create_username (NiceAgent *agent, NiceStream *stream,
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    guint component_id, NiceCandidate *remote, NiceCandidate *local,
    uint8_t *dest, guint dest_len, gboolean inbound);
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static size_t priv_get_password (NiceAgent *agent, NiceStream *stream,
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    NiceCandidate *remote, uint8_t **password);
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static void conn_check_free_item (gpointer data);
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static CandidateCheckPair *priv_conn_check_add_for_candidate_pair_matched (
    NiceAgent *agent, guint stream_id, NiceComponent *component,
    NiceCandidate *local, NiceCandidate *remote, NiceCheckState initial_state);
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static gboolean priv_update_selected_pair (NiceAgent *agent,
    NiceComponent *component, CandidateCheckPair *pair);
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static int priv_timer_expired (GTimeVal *timer, GTimeVal *now)
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{
  return (now->tv_sec == timer->tv_sec) ?
    now->tv_usec >= timer->tv_usec :
    now->tv_sec >= timer->tv_sec;
}
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static gchar
priv_state_to_gchar (NiceCheckState state)
{
  switch (state) {
    case NICE_CHECK_WAITING:
      return 'W';
    case NICE_CHECK_IN_PROGRESS:
      return 'I';
    case NICE_CHECK_SUCCEEDED:
      return 'S';
    case NICE_CHECK_FAILED:
      return 'F';
    case NICE_CHECK_FROZEN:
      return 'Z';
    case NICE_CHECK_CANCELLED:
      return 'C';
    case NICE_CHECK_DISCOVERED:
      return 'D';
    default:
      g_assert_not_reached ();
  }
}

static const gchar *
priv_candidate_type_to_string (NiceCandidateType type)
{
  switch (type) {
    case NICE_CANDIDATE_TYPE_HOST:
      return "host";
    case NICE_CANDIDATE_TYPE_SERVER_REFLEXIVE:
      return "srflx";
    case NICE_CANDIDATE_TYPE_PEER_REFLEXIVE:
      return "prflx";
    case NICE_CANDIDATE_TYPE_RELAYED:
      return "relay";
    default:
      g_assert_not_reached ();
  }
}

/*
 * Dump the conncheck lists of the agent
 */
static void
priv_print_conn_check_lists (NiceAgent *agent, const gchar *where, const gchar *detail)
{
  GSList *i, *k;
  guint j;

  if (!nice_debug_is_verbose ())
    return;

#define PRIORITY_LEN 32

  nice_debug ("Agent %p : *** conncheck list DUMP (called from %s%s)",
      agent, where, detail ? detail : "");
  for (i = agent->streams; i ; i = i->next) {
    NiceStream *stream = i->data;
    for (j = 1; j <= stream->n_components; j++) {
      for (k = stream->conncheck_list; k ; k = k->next) {
        CandidateCheckPair *pair = k->data;
        if (pair->component_id == j) {
          gchar local_addr[INET6_ADDRSTRLEN];
          gchar remote_addr[INET6_ADDRSTRLEN];
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          StunTimer *timer = &pair->timer;
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          nice_address_to_string (&pair->local->addr, local_addr);
          nice_address_to_string (&pair->remote->addr, remote_addr);

          nice_debug ("Agent %p : *** sc=%d/%d : pair %p : "
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              "f=%s t=%s:%s timer=%d/%d %d/%dms "
              "[%s]:%u > [%s]:%u state=%c%s%s%s",
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              agent, pair->stream_id, pair->component_id, pair,
              pair->foundation,
              priv_candidate_type_to_string (pair->local->type),
              priv_candidate_type_to_string (pair->remote->type),
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              timer->retransmissions, timer->max_retransmissions,
              timer->delay - stun_timer_remainder (timer), timer->delay,
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              local_addr, nice_address_get_port (&pair->local->addr),
              remote_addr, nice_address_get_port (&pair->remote->addr),
              priv_state_to_gchar (pair->state),
              pair->valid ? "V" : "",
              pair->nominated ? "N" : "",
              g_slist_find (agent->triggered_check_queue, pair) ? "T" : "");
        }
      }
    }
  }
}

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/* Add the pair to the triggered checks list, if not already present
 */
static void
priv_add_pair_to_triggered_check_queue (NiceAgent *agent, CandidateCheckPair *pair)
{
  g_assert (pair);

  if (agent->triggered_check_queue == NULL ||
      g_slist_find (agent->triggered_check_queue, pair) == NULL)
    agent->triggered_check_queue = g_slist_append (agent->triggered_check_queue, pair);
}

/* Remove the pair from the triggered checks list
 */
static void
priv_remove_pair_from_triggered_check_queue (NiceAgent *agent, CandidateCheckPair *pair)
{
  g_assert (pair);
  agent->triggered_check_queue = g_slist_remove (agent->triggered_check_queue, pair);
}

/* Get the pair from the triggered checks list
 */
static CandidateCheckPair *
priv_get_pair_from_triggered_check_queue (NiceAgent *agent)
{
  CandidateCheckPair *pair = NULL;

  if (agent->triggered_check_queue) {
    pair = (CandidateCheckPair *)agent->triggered_check_queue->data;
    priv_remove_pair_from_triggered_check_queue (agent, pair);
  }
  return pair;
}

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/*
 * Check if the conncheck list if Active according to
 * ICE spec, 5.7.4 (Computing States)
 *
 * note: the ICE spec in unclear about that, but the check list should
 * be considered active when there is at least a pair in Waiting state
 * OR a pair in In-Progress state.
 */
static gboolean
priv_is_checklist_active (NiceStream *stream)
{
  GSList *i;

  for (i = stream->conncheck_list; i ; i = i->next) {
    CandidateCheckPair *p = i->data;
    if (p->state == NICE_CHECK_WAITING || p->state == NICE_CHECK_IN_PROGRESS)
      return TRUE;
  }
  return FALSE;
}

/*
 * Check if the conncheck list if Frozen according to
 * ICE spec, 5.7.4 (Computing States)
 */
static gboolean
priv_is_checklist_frozen (NiceStream *stream)
{
  GSList *i;

  if (stream->conncheck_list == NULL)
    return FALSE;

  for (i = stream->conncheck_list; i ; i = i->next) {
    CandidateCheckPair *p = i->data;
    if (p->state != NICE_CHECK_FROZEN)
      return FALSE;
  }
  return TRUE;
}

/*
 * Check if all components of the stream have
 * a valid pair (used for ICE spec, 7.1.3.2.3, point 2.)
 */
static gboolean
priv_all_components_have_valid_pair (NiceStream *stream)
{
  guint i;
  GSList *j;

  for (i = 1; i <= stream->n_components; i++) {
    for (j = stream->conncheck_list; j ; j = j->next) {
      CandidateCheckPair *p = j->data;
      if (p->component_id == i && p->valid)
        break;
    }
    if (j == NULL)
      return FALSE;
  }
  return TRUE;
}

/*
 * Check if the foundation in parameter matches the foundation
 * of a valid pair in the conncheck list [of stream] (used for ICE spec,
 * 7.1.3.2.3, point 2.)
 */
static gboolean
priv_foundation_matches_a_valid_pair (const gchar *foundation, NiceStream *stream)
{
  GSList *i;

  for (i = stream->conncheck_list; i ; i = i->next) {
    CandidateCheckPair *p = i->data;
    if (p->valid &&
        strncmp (p->foundation, foundation,
            NICE_CANDIDATE_PAIR_MAX_FOUNDATION) == 0)
      return TRUE;
  }
  return FALSE;
}

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/*
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 * Finds the next connectivity check in WAITING state.
 */
static CandidateCheckPair *priv_conn_check_find_next_waiting (GSList *conn_check_list)
{
  GSList *i;

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  /* note: list is sorted in priority order to first waiting check has
   *       the highest priority */
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  for (i = conn_check_list; i ; i = i->next) {
    CandidateCheckPair *p = i->data;
    if (p->state == NICE_CHECK_WAITING)
      return p;
  }

  return NULL;
}

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/*
 * Finds the next connectivity check in FROZEN state.
 */
static CandidateCheckPair *
priv_conn_check_find_next_frozen (GSList *conn_check_list)
{
  GSList *i;

  /* note: list is sorted in priority order to first frozen check has
   *       the highest priority */
  for (i = conn_check_list; i ; i = i->next) {
    CandidateCheckPair *p = i->data;
    if (p->state == NICE_CHECK_FROZEN)
      return p;
  }

  return NULL;
}

/*
 * Returns the number of check lists of the agent
 */
static guint
priv_number_of_check_lists (NiceAgent *agent)
{
  guint n = 0;
  GSList *i;

  for (i = agent->streams; i ; i = i->next) {
    NiceStream *stream = i->data;
    if (stream->conncheck_list != NULL)
      n++;
  }
  return n;
}

/*
 * Returns the number of active check lists of the agent
 */
static guint
priv_number_of_active_check_lists (NiceAgent *agent)
{
  guint n = 0;
  GSList *i;

  for (i = agent->streams; i ; i = i->next)
    if (priv_is_checklist_active (i->data))
      n++;
  return n;
}

/*
 * Returns the first stream of the agent having a Frozen
 * connection check list
 */
static NiceStream *
priv_find_first_frozen_check_list (NiceAgent *agent)
{
  GSList *i;

  for (i = agent->streams; i ; i = i->next) {
    NiceStream *stream = i->data;
    if (priv_is_checklist_frozen (stream))
      return stream;
  }
  return NULL;
}

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/*
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 * Initiates a new connectivity check for a ICE candidate pair.
 *
 * @return TRUE on success, FALSE on error
 */
static gboolean priv_conn_check_initiate (NiceAgent *agent, CandidateCheckPair *pair)
{
  g_get_current_time (&pair->next_tick);
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  g_time_val_add (&pair->next_tick, agent->timer_ta * 1000);
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  pair->state = NICE_CHECK_IN_PROGRESS;
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  nice_debug ("Agent %p : pair %p state IN_PROGRESS", agent, pair);
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  conn_check_send (agent, pair);
  return TRUE;
}

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/*
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 * Unfreezes the next connectivity check in the list. Follows the
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 * algorithm (2.) defined in 5.7.4 (Computing States) of the ICE spec
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 * (RFC5245)
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 *
 * See also sect 7.1.2.2.3 (Updating Pair States), and
 * priv_conn_check_unfreeze_related().
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 * 
 * @return TRUE on success, and FALSE if no frozen candidates were found.
 */
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static gboolean priv_conn_check_unfreeze_next (NiceAgent *agent, NiceStream *stream)
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{
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  GSList *i, *j;
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  GSList *found_list = NULL;
  gboolean result = FALSE;
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  priv_print_conn_check_lists (agent, G_STRFUNC, NULL);

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  for (i = stream->conncheck_list; i ; i = i->next) {
    CandidateCheckPair *p1 = i->data;
    CandidateCheckPair *pair = NULL;
    guint lowest_component_id = stream->n_components + 1;
    guint64 highest_priority = 0;
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    if (g_slist_find_custom (found_list, p1->foundation, (GCompareFunc)strcmp))
      continue;
    found_list = g_slist_prepend (found_list, p1->foundation);
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    for (j = stream->conncheck_list; j ; j = j->next) {
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      CandidateCheckPair *p2 = i->data;
      if (strncmp (p2->foundation, p1->foundation,
              NICE_CANDIDATE_PAIR_MAX_FOUNDATION) == 0) {
        if (p2->component_id < lowest_component_id ||
            (p2->component_id == lowest_component_id &&
             p2->priority > highest_priority)) {
          pair = p2;
          lowest_component_id = p2->component_id;
          highest_priority = p2->priority;
        }
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      }
    }
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    if (pair) {
      nice_debug ("Agent %p : Pair %p with s/c-id %u/%u (%s) unfrozen.",
          agent, pair, pair->stream_id, pair->component_id, pair->foundation);
      pair->state = NICE_CHECK_WAITING;
      nice_debug ("Agent %p : pair %p state WAITING", agent, pair);
      result = TRUE;
    }
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  }
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  g_slist_free (found_list);
  return result;
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}

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/*
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 * Unfreezes the next next connectivity check in the list after
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 * check 'success_check' has successfully completed.
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 *
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 * See sect 7.1.2.2.3 (Updating Pair States) of ICE spec (ID-19).
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 * 
 * @param agent context
 * @param ok_check a connectivity check that has just completed
 *
 * @return TRUE on success, and FALSE if no frozen candidates were found.
 */
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static void priv_conn_check_unfreeze_related (NiceAgent *agent, NiceStream *stream, CandidateCheckPair *ok_check)
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{
  GSList *i, *j;

  g_assert (ok_check);
  g_assert (ok_check->state == NICE_CHECK_SUCCEEDED);
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  g_assert (stream);
  g_assert (stream->id == ok_check->stream_id);
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  priv_print_conn_check_lists (agent, G_STRFUNC, NULL);

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  /* step: perform the step (1) of 'Updating Pair States' */
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  for (i = stream->conncheck_list; i ; i = i->next) {
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    CandidateCheckPair *p = i->data;
   
    if (p->stream_id == ok_check->stream_id) {
      if (p->state == NICE_CHECK_FROZEN &&
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          strncmp (p->foundation, ok_check->foundation,
              NICE_CANDIDATE_PAIR_MAX_FOUNDATION) == 0) {
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	nice_debug ("Agent %p : Unfreezing check %p (after successful check %p).", agent, p, ok_check);
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	p->state = NICE_CHECK_WAITING;
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        nice_debug ("Agent %p : pair %p state WAITING", agent, p);
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      }
    }
  }

  /* step: perform the step (2) of 'Updating Pair States' */
  stream = agent_find_stream (agent, ok_check->stream_id);
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  if (priv_all_components_have_valid_pair (stream)) {
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    for (i = agent->streams; i ; i = i->next) {
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      /* the agent examines the check list for each other
       * media stream in turn
       */
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      NiceStream *s = i->data;
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      if (s->id == ok_check->stream_id)
        continue;
      if (priv_is_checklist_active (s)) {
        /* checklist is Active
         */
        for (j = s->conncheck_list; j ; j = j->next) {
	  CandidateCheckPair *p = j->data;
          if (p->state == NICE_CHECK_FROZEN &&
              priv_foundation_matches_a_valid_pair (p->foundation, stream)) {
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	    nice_debug ("Agent %p : Unfreezing check %p from stream %u (after successful check %p).", agent, p, s->id, ok_check);
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	    p->state = NICE_CHECK_WAITING;
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            nice_debug ("Agent %p : pair %p state WAITING", agent, p);
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          }
        }
      } else if (priv_is_checklist_frozen (s)) {
        /* checklist is Frozen
         */
        gboolean match_found = FALSE;
        /* check if there is one pair in the check list whose
         * foundation matches a pair in the valid list under
         * consideration
         */
        for (j = s->conncheck_list; j ; j = j->next) {
	  CandidateCheckPair *p = j->data;
          if (priv_foundation_matches_a_valid_pair (p->foundation, stream)) {
            match_found = TRUE;
            nice_debug ("Agent %p : Unfreezing check %p from stream %u (after successful check %p).", agent, p, s->id, ok_check);
            p->state = NICE_CHECK_WAITING;
            nice_debug ("Agent %p : pair %p state WAITING", agent, p);
          }
        }

        if (!match_found) {
          /* set the pair with the lowest component ID
           * and highest priority to Waiting
           */
          priv_conn_check_unfreeze_next (agent, s);
        }
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      }
    }
  }    
}

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static void
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candidate_check_pair_fail (NiceStream *stream, NiceAgent *agent, CandidateCheckPair *p)
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{
  StunTransactionId id;
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  NiceComponent *component;
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  component = nice_stream_find_component_by_id (stream, p->component_id);
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  p->state = NICE_CHECK_FAILED;
  nice_debug ("Agent %p : pair %p state FAILED", agent, p);

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  if (p->stun_message.buffer != NULL) {
    stun_message_id (&p->stun_message, id);
    stun_agent_forget_transaction (&component->stun_agent, id);
  }
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  p->stun_message.buffer = NULL;
  p->stun_message.buffer_len = 0;
}

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/*
 * Function that resubmits a new connection check, after a previous
 * check in in-progress state got cancelled due to an incoming stun
 * request matching this same pair
 *
 * @return will return TRUE if the pair is scheduled for recheck
 */
static gboolean
priv_conn_recheck_on_timeout (NiceAgent *agent, CandidateCheckPair *p)
{
  if (p->recheck_on_timeout) {
    g_assert (p->state == NICE_CHECK_IN_PROGRESS);
    /* this cancelled pair may have the flag 'mark nominated
     * on response arrival' set, we want to keep it, because
     * this is needed to nominate this pair in aggressive
     * nomination, when the agent is in controlled mode.
     *
     * this cancelled pair may also have the flag 'use candidate
     * on next check' set, that we want to preserve too.
     */
    nice_debug ("Agent %p : pair %p was cancelled, "
        "triggering a new connection check", agent, p);
    p->recheck_on_timeout = FALSE;
    p->state = NICE_CHECK_WAITING;
    nice_debug ("Agent %p : pair %p state WAITING", agent, p);
    priv_add_pair_to_triggered_check_queue (agent, p);
    return TRUE;
  }
  return FALSE;
}

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/*
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 * Helper function for connectivity check timer callback that
 * runs through the stream specific part of the state machine. 
 *
 * @param schedule if TRUE, schedule a new check
 *
 * @return will return FALSE when no more pending timers.
 */
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static gboolean priv_conn_check_tick_stream (NiceStream *stream, NiceAgent *agent, GTimeVal *now)
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{
  gboolean keep_timer_going = FALSE;
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  GSList *i;
  CandidateCheckPair *pair;
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  /* step: process ongoing STUN transactions */
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  for (i = stream->conncheck_list; i ; i = i->next) {
    CandidateCheckPair *p = i->data;
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    if (p->state == NICE_CHECK_IN_PROGRESS) {
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      if (p->stun_message.buffer == NULL) {
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	nice_debug ("Agent %p : STUN connectivity check was cancelled, marking as done.", agent);
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	p->state = NICE_CHECK_FAILED;
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        nice_debug ("Agent %p : pair %p state FAILED", agent, p);
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      } else if (priv_timer_expired (&p->next_tick, now)) {
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        switch (stun_timer_refresh (&p->timer)) {
          case STUN_USAGE_TIMER_RETURN_TIMEOUT:
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            {
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              gchar tmpbuf1[INET6_ADDRSTRLEN], tmpbuf2[INET6_ADDRSTRLEN];
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              /* case: conncheck cancelled due to in-progress incoming
               * check, requeing the pair, ICE spec, sect 7.2.1.4
               * "Triggered Checks", "If the state of that pair is
               * In-Progress..."
               */
              if (priv_conn_recheck_on_timeout (agent, p))
                break;

              /* case: error, abort processing */
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              nice_address_to_string (&p->local->addr, tmpbuf1);
              nice_address_to_string (&p->remote->addr, tmpbuf2);
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              nice_debug ("Agent %p : Retransmissions failed, giving up on connectivity check %p", agent, p);
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              nice_debug ("Agent %p : Failed pair is [%s]:%u --> [%s]:%u", agent,
                  tmpbuf1, nice_address_get_port (&p->local->addr),
                  tmpbuf2, nice_address_get_port (&p->remote->addr));
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              candidate_check_pair_fail (stream, agent, p);
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              priv_print_conn_check_lists (agent, G_STRFUNC,
                  ", retransmission failed");
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              break;
            }
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          case STUN_USAGE_TIMER_RETURN_RETRANSMIT:
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            {
              unsigned int timeout = stun_timer_remainder (&p->timer);
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              /* case: conncheck cancelled due to in-progress incoming
               * check, requeing the pair, ICE spec, sect 7.2.1.4
               * "Triggered Checks", "If the state of that pair is
               * In-Progress..."
               */
              if (priv_conn_recheck_on_timeout (agent, p))
                break;

              /* case: not ready, so schedule a new timeout */
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              nice_debug ("Agent %p :STUN transaction retransmitted on pair %p "
                  "(timeout %dms, delay=%dms, retrans=%d).",
                  agent, p, timeout, p->timer.delay, p->timer.retransmissions);
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              agent_socket_send (p->sockptr, &p->remote->addr,
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                  stun_message_length (&p->stun_message),
                  (gchar *)p->stun_buffer);


              /* note: convert from milli to microseconds for g_time_val_add() */
              p->next_tick = *now;
              g_time_val_add (&p->next_tick, timeout * 1000);

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              return TRUE;
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            }
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          case STUN_USAGE_TIMER_RETURN_SUCCESS:
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            {
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              unsigned int timeout = stun_timer_remainder (&p->timer);

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              /* note: convert from milli to microseconds for g_time_val_add() */
              p->next_tick = *now;
              g_time_val_add (&p->next_tick, timeout * 1000);

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              keep_timer_going = TRUE;
              break;
            }
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          default:
            /* Nothing to do. */
            break;
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        }
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      }
    }
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   }

  /* step: perform an ordinary check, ICE spec, 5.8 "Scheduling Checks"
   * note: This code is executed when the triggered checks list is
   * empty, and when no STUN message has been sent (pacing constraint)
   */
  pair = priv_conn_check_find_next_waiting (stream->conncheck_list);
  if (pair) {
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    /* remove the pair from the triggered check list if needed. This
     * may happen with the cancelled pair, that's just been added
     * in state waiting to the triggered check list above in the
     * same function.
     */
    priv_remove_pair_from_triggered_check_queue (agent, pair);
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    priv_print_conn_check_lists (agent, G_STRFUNC,
        ", got a pair in Waiting state");
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    priv_conn_check_initiate (agent, pair);
    return TRUE;
  }

  /* note: this is unclear in the ICE spec, but a check list in Frozen
   * state (where all pairs are in Frozen state) is not supposed to
   * change its state by an ordinary check, but only by the success of
   * checks in other check lists, in priv_conn_check_unfreeze_related().
   * The underlying idea is to concentrate the checks on a single check
   * list initially.
   */
  if (priv_is_checklist_frozen (stream))
    return keep_timer_going;

  /* step: ordinary check continued, if there's no pair in the waiting
   * state, pick a pair in the frozen state
   */
  pair = priv_conn_check_find_next_frozen (stream->conncheck_list);
  if (pair) {
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    priv_print_conn_check_lists (agent, G_STRFUNC,
        ", got a pair in Frozen state");
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    pair->state = NICE_CHECK_WAITING;
    nice_debug ("Agent %p : pair %p state WAITING", agent, pair);
    priv_conn_check_initiate (agent, pair);
    return TRUE;
  }
  return keep_timer_going;
}

static gboolean
priv_conn_check_tick_stream_nominate (NiceStream *stream, NiceAgent *agent)
{
  gboolean keep_timer_going = FALSE;
  guint s_inprogress = 0;
  guint s_succeeded = 0;
  guint s_discovered = 0;
  guint s_nominated = 0;
  guint s_waiting_for_nomination = 0;
  guint s_valid = 0;
  guint frozen = 0;
  guint waiting = 0;
  GSList *i, *k;
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  for (i = stream->conncheck_list; i ; i = i->next) {
    CandidateCheckPair *p = i->data;
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    if (p->state == NICE_CHECK_FROZEN)
      ++frozen;
    else if (p->state == NICE_CHECK_IN_PROGRESS)
      ++s_inprogress;
    else if (p->state == NICE_CHECK_WAITING)
      ++waiting;
    else if (p->state == NICE_CHECK_SUCCEEDED)
      ++s_succeeded;
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    else if (p->state == NICE_CHECK_DISCOVERED)
      ++s_discovered;
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    if (p->valid)
      ++s_valid;
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    if ((p->state == NICE_CHECK_SUCCEEDED || p->state == NICE_CHECK_DISCOVERED)
        && p->nominated)
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      ++s_nominated;
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    else if ((p->state == NICE_CHECK_SUCCEEDED ||
            p->state == NICE_CHECK_DISCOVERED) && !p->nominated)
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      ++s_waiting_for_nomination;
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  }
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    /* note: keep the timer going as long as there is work to be done */
  if (s_inprogress)
    keep_timer_going = TRUE;
  
    /* note: if some components have established connectivity,
     *       but yet no nominated pair, keep timer going */
  if (s_nominated < stream->n_components &&
      s_waiting_for_nomination) {
    keep_timer_going = TRUE;
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    if (NICE_AGENT_IS_COMPATIBLE_WITH_RFC5245_OR_OC2007R2 (agent)) {
      if (agent->nomination_mode == NICE_NOMINATION_MODE_REGULAR &&
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          agent->controlling_mode) {
#define NICE_MIN_NUMBER_OF_VALID_PAIRS 2
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        /* ICE 8.1.1.1 Regular nomination
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         * we choose to nominate the valid pair of a component if
         * - there is no pair left frozen, waiting or in-progress, or
         * - if there are at least two valid pairs, or
         * - if there is at least one valid pair of type HOST-HOST
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         *
         * This is the "stopping criterion" described in 8.1.1.1, and is
         * a "local optimization" between accumulating more valid pairs,
         * and limiting the time spent waiting for in-progress connections
         * checks until they finally fail.
         */
        GSList *component_item;

        for (component_item = stream->components; component_item;
             component_item = component_item->next) {
          NiceComponent *component = component_item->data;
          gboolean already_done = FALSE;
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          gboolean stopping_criterion = FALSE;
          guint p_valid = 0;
          guint p_frozen = 0;
          guint p_waiting = 0;
          guint p_inprogress = 0;
          guint p_host_host_valid = 0;
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          /* verify that the choice of the pair to be nominated
           * has not already been done
           */
          for (k = stream->conncheck_list; k ; k = k->next) {
            CandidateCheckPair *p = k->data;
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            if (p->component_id == component->id) {
              if (p->use_candidate_on_next_check)
                already_done = TRUE;
              if (p->state == NICE_CHECK_FROZEN)
                p_frozen++;
              else if (p->state == NICE_CHECK_WAITING)
                p_waiting++;
              else if (p->state == NICE_CHECK_IN_PROGRESS)
                p_inprogress++;
              if (p->valid)
                p_valid++;
              if (p->valid &&
                  p->local->type == NICE_CANDIDATE_TYPE_HOST &&
                  p->remote->type == NICE_CANDIDATE_TYPE_HOST)
                p_host_host_valid++;
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            }
          }

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          if (already_done)
            continue;

          stopping_criterion =
              (p_host_host_valid > 0 ||
               p_valid >= NICE_MIN_NUMBER_OF_VALID_PAIRS ||
               (p_waiting == 0 && p_inprogress == 0 && p_frozen == 0));

          if (!stopping_criterion)
            continue;

          /* when the stopping criterion is satisfied, we choose
           * a pair to be nominated in the list of valid pairs,
           * and add it to the triggered checks list
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           */
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          for (k = stream->conncheck_list; k ; k = k->next) {
            CandidateCheckPair *p = k->data;
            /* note: highest priority item selected (list always sorted) */
            if (p->component_id == component->id &&
                !p->nominated &&
                !p->use_candidate_on_next_check &&
                p->valid) {
              nice_debug ("Agent %p : restarting check %p with "
                  "USE-CANDIDATE attrib (regular nomination)", agent, p);
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              p->recheck_on_timeout = FALSE;
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              p->use_candidate_on_next_check = TRUE;
              priv_add_pair_to_triggered_check_queue (agent, p);
              break; /* move to the next component */
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            }
          }
        }
      }
    } else if (agent->controlling_mode) {
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      GSList *component_item;

      for (component_item = stream->components; component_item;
           component_item = component_item->next) {
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        NiceComponent *component = component_item->data;
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	for (k = stream->conncheck_list; k ; k = k->next) {
	  CandidateCheckPair *p = k->data;
	  /* note: highest priority item selected (list always sorted) */
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	  if (p->component_id == component->id &&
              (p->state == NICE_CHECK_SUCCEEDED ||
               p->state == NICE_CHECK_DISCOVERED)) {
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	    nice_debug ("Agent %p : restarting check %p as the nominated pair.", agent, p);
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	    p->nominated = TRUE;
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            p->recheck_on_timeout = FALSE;
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            priv_update_selected_pair (agent, component, p);
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            priv_add_pair_to_triggered_check_queue (agent, p);
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	    break; /* move to the next component */
	  }
	}
      }
    }
  }
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  if (stream->tick_counter++ % 50 == 0)
    nice_debug ("Agent %p : stream %u: timer tick #%u: %u frozen, %u in-progress, "
        "%u waiting, %u succeeded, %u discovered, %u nominated, "
        "%u waiting-for-nom, %u valid.", agent, stream->id,
        stream->tick_counter, frozen, s_inprogress, waiting, s_succeeded,
        s_discovered, s_nominated, s_waiting_for_nomination, s_valid);
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  return keep_timer_going;

}

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static void
conn_check_stop (NiceAgent *agent)
{
  if (agent->conncheck_timer_source == NULL)
    return;

  g_source_destroy (agent->conncheck_timer_source);
  g_source_unref (agent->conncheck_timer_source);
  agent->conncheck_timer_source = NULL;
}

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/*
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 * Timer callback that handles initiating and managing connectivity
 * checks (paced by the Ta timer).
 *
 * This function is designed for the g_timeout_add() interface.
 *
 * @return will return FALSE when no more pending timers.
 */
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static gboolean priv_conn_check_tick_unlocked (NiceAgent *agent)
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{
  CandidateCheckPair *pair = NULL;
  gboolean keep_timer_going = FALSE;
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  GSList *i, *j;
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  GTimeVal now;
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  g_get_current_time (&now);
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  /* the conncheck really starts when we have built
   * a connection check list for each stream
   */
  if (priv_number_of_check_lists (agent) < g_slist_length (agent->streams))
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    return TRUE;

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  /* configure the initial state of the check lists of the agent
   * as described in ICE spec, 5.7.4
   *
   * if all pairs in all check lists are in frozen state, then
   * we are in the initial state (5.7.4, point 1.)
   */
  if (priv_number_of_active_check_lists (agent) == 0) {
    /* set some pairs of the first stream in the waiting state
     * ICE spec, 5.7.4, point 2.
     *
     * note: we adapt the ICE spec here, by selecting the first
     * frozen check list, which is not necessarily the check
     * list of the first stream (the first stream may be completed)
     */
    NiceStream *stream = priv_find_first_frozen_check_list (agent);
    if (stream)
      priv_conn_check_unfreeze_next (agent, stream);
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  }
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  /* step: perform a test from the triggered checks list,
   * ICE spec, 5.8 "Scheduling Checks"
   */
  pair = priv_get_pair_from_triggered_check_queue (agent);

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  if (pair) {
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    priv_print_conn_check_lists (agent, G_STRFUNC,
        ", got a pair from triggered check list");
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    priv_conn_check_initiate (agent, pair);
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    return TRUE;
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  }

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  /* step: process ongoing STUN transactions and
   * perform an ordinary check, ICE spec, 5.8, "Scheduling Checks"
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   */
  for (i = agent->streams; i ; i = i->next) {
    NiceStream *stream = i->data;
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    if (priv_conn_check_tick_stream (stream, agent, &now))
      keep_timer_going = TRUE;
    if (priv_conn_check_tick_stream_nominate (stream, agent))
      keep_timer_going = TRUE;
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  }
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  /* step: stop timer if no work left */
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  if (keep_timer_going != TRUE) {
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    nice_debug ("Agent %p : %s: stopping conncheck timer", agent, G_STRFUNC);
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    for (i = agent->streams; i; i = i->next) {
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      NiceStream *stream = i->data;
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      priv_update_check_list_failed_components (agent, stream);
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      for (j = stream->components; j; j = j->next) {
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        NiceComponent *component = j->data;
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        priv_update_check_list_state_for_ready (agent, stream, component);
      }
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    }
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    priv_print_conn_check_lists (agent, G_STRFUNC,
        ", conncheck timer stopped");

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    /* Stopping the timer so destroy the source.. this will allow
       the timer to be reset if we get a set_remote_candidates after this
       point */
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    conn_check_stop (agent);
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    /* XXX: what to signal, is all processing now really done? */
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    nice_debug ("Agent %p : changing conncheck state to COMPLETED.", agent);
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  }

  return keep_timer_going;
}

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static gboolean priv_conn_check_tick (gpointer pointer)
{
  gboolean ret;
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  NiceAgent *agent = pointer;
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  agent_lock();
  if (g_source_is_destroyed (g_main_current_source ())) {
    nice_debug ("Source was destroyed. "
        "Avoided race condition in priv_conn_check_tick");
    agent_unlock ();
    return FALSE;
  }
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  ret = priv_conn_check_tick_unlocked (agent);
  agent_unlock_and_emit (agent);
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  return ret;
}

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static gboolean priv_conn_keepalive_retransmissions_tick (gpointer pointer)
{
  CandidatePair *pair = (CandidatePair *) pointer;

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  agent_lock();
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  /* A race condition might happen where the mutex above waits for the lock
   * and in the meantime another thread destroys the source.
   * In that case, we don't need to run our retransmission tick since it should
   * have been cancelled */
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  if (g_source_is_destroyed (g_main_current_source ())) {
    nice_debug ("Source was destroyed. "
        "Avoided race condition in priv_conn_keepalive_retransmissions_tick");
    agent_unlock ();
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    return FALSE;
  }

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  g_source_destroy (pair->keepalive.tick_source);
  g_source_unref (pair->keepalive.tick_source);
  pair->keepalive.tick_source = NULL;

  switch (stun_timer_refresh (&pair->keepalive.timer)) {
    case STUN_USAGE_TIMER_RETURN_TIMEOUT:
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      {
        /* Time out */
        StunTransactionId id;
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        NiceComponent *component;
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        if (!agent_find_component (pair->keepalive.agent,
                pair->keepalive.stream_id, pair->keepalive.component_id,
                NULL, &component)) {
          nice_debug ("Could not find stream or component in"
              " priv_conn_keepalive_retransmissions_tick");
          agent_unlock ();
          return FALSE;
        }
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        stun_message_id (&pair->keepalive.stun_message, id);
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        stun_agent_forget_transaction (&component->stun_agent, id);
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        pair->keepalive.stun_message.buffer = NULL;
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        if (pair->keepalive.agent->media_after_tick) {
          nice_debug ("Agent %p : Keepalive conncheck timed out!! "
              "but media was received. Suspecting keepalive lost because of "
              "network bottleneck", pair->keepalive.agent);
        } else {
          nice_debug ("Agent %p : Keepalive conncheck timed out!! "
              "peer probably lost connection", pair->keepalive.agent);
          agent_signal_component_state_change (pair->keepalive.agent,
              pair->keepalive.stream_id, pair->keepalive.component_id,
              NICE_COMPONENT_STATE_FAILED);
        }
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        break;
      }
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    case STUN_USAGE_TIMER_RETURN_RETRANSMIT:
      /* Retransmit */
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      agent_socket_send (pair->local->sockptr, &pair->remote->addr,
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          stun_message_length (&pair->keepalive.stun_message),
          (gchar *)pair->keepalive.stun_buffer);

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      nice_debug ("Agent %p : Retransmitting keepalive conncheck",
          pair->keepalive.agent);
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      agent_timeout_add_with_context (pair->keepalive.agent,
          &pair->keepalive.tick_source,
          "Pair keepalive", stun_timer_remainder (&pair->keepalive.timer),
          priv_conn_keepalive_retransmissions_tick, pair);
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      break;
    case STUN_USAGE_TIMER_RETURN_SUCCESS:
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      agent_timeout_add_with_context (pair->keepalive.agent,
          &pair->keepalive.tick_source,
          "Pair keepalive", stun_timer_remainder (&pair->keepalive.timer),
          priv_conn_keepalive_retransmissions_tick, pair);
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      break;
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    default:
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      g_assert_not_reached();
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      break;
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  }


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  agent_unlock_and_emit (pair->keepalive.agent);
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  return FALSE;
}

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static guint32 peer_reflexive_candidate_priority (NiceAgent *agent,
    NiceCandidate *local_candidate)
{
  NiceCandidate *candidate_priority =
      nice_candidate_new (NICE_CANDIDATE_TYPE_PEER_REFLEXIVE);
  guint32 priority;

  candidate_priority->transport = local_candidate->transport;
  candidate_priority->component_id = local_candidate->component_id;
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  candidate_priority->base_addr = local_candidate->addr;
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  if (agent->compatibility == NICE_COMPATIBILITY_GOOGLE) {
    priority = nice_candidate_jingle_priority (candidate_priority);
  } else if (agent->compatibility == NICE_COMPATIBILITY_MSN ||
             agent->compatibility == NICE_COMPATIBILITY_OC2007) {
    priority = nice_candidate_msn_priority (candidate_priority);
  } else if (agent->compatibility == NICE_COMPATIBILITY_OC2007R2) {
    priority = nice_candidate_ms_ice_priority (candidate_priority,
        agent->reliable, FALSE);
  } else {
    priority = nice_candidate_ice_priority (candidate_priority,
        agent->reliable, FALSE);
  }
  nice_candidate_free (candidate_priority);

  return priority;
}

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static void ms_ice2_legacy_conncheck_send(StunMessage *msg, NiceSocket *sock,
    const NiceAddress *remote_addr)
{
  uint32_t *fingerprint_attr;
  uint32_t fingerprint_orig;
  uint16_t fingerprint_len;
  size_t buffer_len;

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  if (msg->agent->ms_ice2_send_legacy_connchecks == FALSE) {
    return;
  }

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  fingerprint_attr = (uint32_t *)stun_message_find (msg,
      STUN_ATTRIBUTE_FINGERPRINT, &fingerprint_len);

  if (fingerprint_attr == NULL) {
    nice_debug ("FINGERPRINT not found.");
    return;
  }

  if (fingerprint_len != sizeof (fingerprint_orig)) {
    nice_debug ("Unexpected FINGERPRINT length %u.", fingerprint_len);
    return;
  }

  memcpy (&fingerprint_orig, fingerprint_attr, sizeof (fingerprint_orig));
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  buffer_len = stun_message_length (msg);

  *fingerprint_attr = stun_fingerprint (msg->buffer, buffer_len, TRUE);

  agent_socket_send (sock, remote_addr, buffer_len, (gchar *)msg->buffer);

  memcpy (fingerprint_attr, &fingerprint_orig, sizeof (fingerprint_orig));
}
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/*
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 * Timer callback that handles initiating and managing connectivity
 * checks (paced by the Ta timer).
 *
 * This function is designed for the g_timeout_add() interface.
 *
 * @return will return FALSE when no more pending timers.
 */
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static gboolean priv_conn_keepalive_tick_unlocked (NiceAgent *agent)
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{
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  GSList *i, *j, *k;
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  int errors = 0;
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  gboolean ret = FALSE;
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  size_t buf_len = 0;
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  /* case 1: session established and media flowing
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   *         (ref ICE sect 10 "Keepalives" ID-19)  */
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  for (i = agent->streams; i; i = i->next) {
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    NiceStream *stream = i->data;
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    for (j = stream->components; j; j = j->next) {
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      NiceComponent *component = j->data;
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      if (component->selected_pair.local != NULL) {
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	CandidatePair *p = &component->selected_pair;
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        /* Disable keepalive checks on TCP candidates */
        if (p->local->transport != NICE_CANDIDATE_TRANSPORT_UDP)
          continue;

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        if (agent->compatibility == NICE_COMPATIBILITY_GOOGLE ||
            agent->keepalive_conncheck) {
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          uint8_t uname[NICE_STREAM_MAX_UNAME];
          size_t uname_len =
              priv_create_username (agent, agent_find_stream (agent, stream->id),
                  component->id, p->remote, p->local, uname, sizeof (uname),
                  FALSE);
          uint8_t *password = NULL;
          size_t password_len = priv_get_password (agent,
              agent_find_stream (agent, stream->id), p->remote, &password);

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