src/feature/stats/predict_ports.c

   1 /* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
   2  * Copyright (c) 2007-2021, The Tor Project, Inc. */
   3 /* See LICENSE for licensing information */
   4
   5 /**
   6  * \file predict_ports.c
   7  * \brief Remember what ports we've needed so we can have circuits ready.
   8  *
   9  * Predicted ports are used by clients to remember how long it's been
  10  * since they opened an exit connection to each given target
  11  * port. Clients use this information in order to try to keep circuits
  12  * open to exit nodes that can connect to the ports that they care
  13  * about.  (The predicted ports mechanism also handles predicted circuit
  14  * usage that _isn't_ port-specific, such as resolves, internal circuits,
  15  * and so on.)
  16  **/
  17
  18 #include "core/or/or.h"
  19
  20 #include "app/config/config.h"
  21 #include "core/or/channelpadding.h"
  22 #include "core/or/circuituse.h"
  23 #include "feature/relay/routermode.h"
  24 #include "feature/relay/selftest.h"
  25 #include "feature/stats/predict_ports.h"
  26 #include "lib/container/bitarray.h"
  27 #include "lib/time/tvdiff.h"
  28
  29 static size_t predicted_ports_total_alloc = 0;
  30
  31 static void predicted_ports_alloc(void);
  32
  33 /** A single predicted port: used to remember which ports we've made
  34  * connections to, so that we can try to keep making circuits that can handle
  35  * those ports. */
  36 typedef struct predicted_port_t {
  37   /** The port we connected to */
  38   uint16_t port;
  39   /** The time at which we last used it */
  40   time_t time;
  41 } predicted_port_t;
  42
  43 /** A list of port numbers that have been used recently. */
  44 static smartlist_t *predicted_ports_list=NULL;
  45 /** How long do we keep predicting circuits? */
  46 static time_t prediction_timeout=0;
  47 /** When was the last time we added a prediction entry (HS or port) */
  48 static time_t last_prediction_add_time=0;
  49
  50 /**
  51  * How much time left until we stop predicting circuits?
  52  */
  53 int
  54 predicted_ports_prediction_time_remaining(time_t now)
  55 {
  56   time_t seconds_waited;
  57   time_t seconds_left;
  58
  59   /* Protect against overflow of return value. This can happen if the clock
  60    * jumps backwards in time. Update the last prediction time (aka last
  61    * active time) to prevent it. This update is preferable to using monotonic
  62    * time because it prevents clock jumps into the past from simply causing
  63    * very long idle timeouts while the monotonic time stands still. */
  64   seconds_waited = time_diff(last_prediction_add_time, now);
  65   if (seconds_waited == TIME_MAX) {
  66     last_prediction_add_time = now;
  67     seconds_waited = 0;
  68   }
  69
  70   /* Protect against underflow of the return value. This can happen for very
  71    * large periods of inactivity/system sleep. */
  72   if (seconds_waited > prediction_timeout)
  73     return 0;
  74
  75   seconds_left = time_diff(seconds_waited, prediction_timeout);
  76   if (BUG(seconds_left == TIME_MAX))
  77     return INT_MAX;
  78
  79   return (int)(seconds_left);
  80 }
  81
  82 /** We just got an application request for a connection with
  83  * port <b>port</b>. Remember it for the future, so we can keep
  84  * some circuits open that will exit to this port.
  85  */
  86 static void
  87 add_predicted_port(time_t now, uint16_t port)
  88 {
  89   predicted_port_t *pp = tor_malloc(sizeof(predicted_port_t));
  90
  91   //  If the list is empty, re-randomize predicted ports lifetime
  92   if (!any_predicted_circuits(now)) {
  93     prediction_timeout =
  94      (time_t)channelpadding_get_circuits_available_timeout();
  95   }
  96
  97   last_prediction_add_time = now;
  98
  99   log_info(LD_CIRC,
 100           "New port prediction added. Will continue predictive circ building "
 101           "for %d more seconds.",
 102           predicted_ports_prediction_time_remaining(now));
 103
 104   pp->port = port;
 105   pp->time = now;
 106   predicted_ports_total_alloc += sizeof(*pp);
 107   smartlist_add(predicted_ports_list, pp);
 108 }
 109
 110 /** Remember that <b>port</b> has been asked for as of time <b>now</b>.
 111  * This is used for predicting what sorts of streams we'll make in the
 112  * future and making exit circuits to anticipate that.
 113  */
 114 void
 115 rep_hist_note_used_port(time_t now, uint16_t port)
 116 {
 117   tor_assert(predicted_ports_list);
 118
 119   if (!port) /* record nothing */
 120     return;
 121
 122   SMARTLIST_FOREACH_BEGIN(predicted_ports_list, predicted_port_t *, pp) {
 123     if (pp->port == port) {
 124       pp->time = now;
 125
 126       last_prediction_add_time = now;
 127       log_info(LD_CIRC,
 128                "New port prediction added. Will continue predictive circ "
 129                "building for %d more seconds.",
 130                predicted_ports_prediction_time_remaining(now));
 131       return;
 132     }
 133   } SMARTLIST_FOREACH_END(pp);
 134   /* it's not there yet; we need to add it */
 135   add_predicted_port(now, port);
 136 }
 137
 138 /** Return a newly allocated pointer to a list of uint16_t * for ports that
 139  * are likely to be asked for in the near future.
 140  */
 141 smartlist_t *
 142 rep_hist_get_predicted_ports(time_t now)
 143 {
 144   int predicted_circs_relevance_time;
 145   smartlist_t *out = smartlist_new();
 146   tor_assert(predicted_ports_list);
 147
 148   predicted_circs_relevance_time = (int)prediction_timeout;
 149
 150   /* clean out obsolete entries */
 151   SMARTLIST_FOREACH_BEGIN(predicted_ports_list, predicted_port_t *, pp) {
 152     if (pp->time + predicted_circs_relevance_time < now) {
 153       log_debug(LD_CIRC, "Expiring predicted port %d", pp->port);
 154
 155       predicted_ports_total_alloc -= sizeof(predicted_port_t);
 156       tor_free(pp);
 157       SMARTLIST_DEL_CURRENT(predicted_ports_list, pp);
 158     } else {
 159       smartlist_add(out, tor_memdup(&pp->port, sizeof(uint16_t)));
 160     }
 161   } SMARTLIST_FOREACH_END(pp);
 162   return out;
 163 }
 164
 165 /**
 166  * Take a list of uint16_t *, and remove every port in the list from the
 167  * current list of predicted ports.
 168  */
 169 void
 170 rep_hist_remove_predicted_ports(const smartlist_t *rmv_ports)
 171 {
 172   /* Let's do this on O(N), not O(N^2). */
 173   bitarray_t *remove_ports = bitarray_init_zero(UINT16_MAX);
 174   SMARTLIST_FOREACH(rmv_ports, const uint16_t *, p,
 175                     bitarray_set(remove_ports, *p));
 176   SMARTLIST_FOREACH_BEGIN(predicted_ports_list, predicted_port_t *, pp) {
 177     if (bitarray_is_set(remove_ports, pp->port)) {
 178       tor_free(pp);
 179       predicted_ports_total_alloc -= sizeof(*pp);
 180       SMARTLIST_DEL_CURRENT(predicted_ports_list, pp);
 181     }
 182   } SMARTLIST_FOREACH_END(pp);
 183   bitarray_free(remove_ports);
 184 }
 185
 186 /** The user asked us to do a resolve. Rather than keeping track of
 187  * timings and such of resolves, we fake it for now by treating
 188  * it the same way as a connection to port 80. This way we will continue
 189  * to have circuits lying around if the user only uses Tor for resolves.
 190  */
 191 void
 192 rep_hist_note_used_resolve(time_t now)
 193 {
 194   rep_hist_note_used_port(now, 80);
 195 }
 196
 197 /** The last time at which we needed an internal circ. */
 198 static time_t predicted_internal_time = 0;
 199 /** The last time we needed an internal circ with good uptime. */
 200 static time_t predicted_internal_uptime_time = 0;
 201 /** The last time we needed an internal circ with good capacity. */
 202 static time_t predicted_internal_capacity_time = 0;
 203
 204 /** Remember that we used an internal circ at time <b>now</b>. */
 205 void
 206 rep_hist_note_used_internal(time_t now, int need_uptime, int need_capacity)
 207 {
 208   // If the list is empty, re-randomize predicted ports lifetime
 209   if (!any_predicted_circuits(now)) {
 210     prediction_timeout = channelpadding_get_circuits_available_timeout();
 211   }
 212
 213   last_prediction_add_time = now;
 214
 215   log_info(LD_CIRC,
 216           "New port prediction added. Will continue predictive circ building "
 217           "for %d more seconds.",
 218           predicted_ports_prediction_time_remaining(now));
 219
 220   predicted_internal_time = now;
 221   if (need_uptime)
 222     predicted_internal_uptime_time = now;
 223   if (need_capacity)
 224     predicted_internal_capacity_time = now;
 225 }
 226
 227 /** Return 1 if we've used an internal circ recently; else return 0. */
 228 int
 229 rep_hist_get_predicted_internal(time_t now, int *need_uptime,
 230                                 int *need_capacity)
 231 {
 232   int predicted_circs_relevance_time;
 233
 234   predicted_circs_relevance_time = (int)prediction_timeout;
 235
 236   if (!predicted_internal_time) { /* initialize it */
 237     predicted_internal_time = now;
 238     predicted_internal_uptime_time = now;
 239     predicted_internal_capacity_time = now;
 240   }
 241   if (predicted_internal_time + predicted_circs_relevance_time < now)
 242     return 0; /* too long ago */
 243   if (predicted_internal_uptime_time + predicted_circs_relevance_time >= now)
 244     *need_uptime = 1;
 245   // Always predict that we need capacity.
 246   *need_capacity = 1;
 247   return 1;
 248 }
 249
 250 /** Any ports used lately? These are pre-seeded if we just started
 251  * up or if we're running a hidden service. */
 252 int
 253 any_predicted_circuits(time_t now)
 254 {
 255   int predicted_circs_relevance_time;
 256   predicted_circs_relevance_time = (int)prediction_timeout;
 257
 258   return smartlist_len(predicted_ports_list) ||
 259          predicted_internal_time + predicted_circs_relevance_time >= now;
 260 }
 261
 262 /** Return 1 if we have no need for circuits currently, else return 0. */
 263 int
 264 rep_hist_circbuilding_dormant(time_t now)
 265 {
 266   const or_options_t *options = get_options();
 267
 268   if (any_predicted_circuits(now))
 269     return 0;
 270
 271   /* see if we'll still need to build testing circuits */
 272   if (server_mode(options) &&
 273       (!router_all_orports_seem_reachable(options) ||
 274        !circuit_enough_testing_circs()))
 275     return 0;
 276
 277   return 1;
 278 }
 279
 280 /**
 281  * Allocate whatever memory and structs are needed for predicting
 282  * which ports will be used. Also seed it with port 80, so we'll build
 283  * circuits on start-up.
 284  */
 285 static void
 286 predicted_ports_alloc(void)
 287 {
 288   predicted_ports_list = smartlist_new();
 289 }
 290
 291 void
 292 predicted_ports_init(void)
 293 {
 294   predicted_ports_alloc();
 295   add_predicted_port(time(NULL), 443); // Add a port to get us started
 296 }
 297
 298 /** Free whatever memory is needed for predicting which ports will
 299  * be used.
 300  */
 301 void
 302 predicted_ports_free_all(void)
 303 {
 304   if (!predicted_ports_list)
 305     return;
 306   predicted_ports_total_alloc -=
 307     smartlist_len(predicted_ports_list)*sizeof(predicted_port_t);
 308   SMARTLIST_FOREACH(predicted_ports_list, predicted_port_t *,
 309                     pp, tor_free(pp));
 310   smartlist_free(predicted_ports_list);
 311 }