src/core/or/conflux_params.c

   1 /* Copyright (c) 2023, The Tor Project, Inc. */
   2 /* See LICENSE for licensing information */
   3
   4 /**
   5  * \file conflux_params.h
   6  * \brief Header file for conflux_params.c.
   7  **/
   8
   9 #include "core/or/or.h"
  10
  11 #include "app/config/config.h"
  12
  13 #include "core/or/conflux_params.h"
  14 #include "core/or/congestion_control_common.h"
  15 #include "core/or/circuitlist.h"
  16
  17 #include "feature/nodelist/networkstatus.h"
  18 #include "feature/nodelist/networkstatus_st.h"
  19 #include "feature/nodelist/routerstatus_st.h"
  20 #include "feature/relay/routermode.h"
  21
  22 #include "core/or/origin_circuit_st.h"
  23
  24 /**
  25  * Consensus parameters defaults, minimums and maximums.
  26  */
  27
  28 /* For "cfx_enabled". */
  29 #define CONFLUX_ENABLED_MIN (0)
  30 #define CONFLUX_ENABLED_MAX (1)
  31 #define CONFLUX_ENABLED_DEFAULT (1)
  32
  33 /* For "cfx_low_exit_threshold". This is a percentage scaled to 10000 so we can
  34  * support two decimal points. For example, 65.78% would be 6578. */
  35 #define LOW_EXIT_THRESHOLD_MIN (0)
  36 #define LOW_EXIT_THRESHOLD_MAX (10000)
  37 #define LOW_EXIT_THRESHOLD_DEFAULT (6000)
  38
  39 /* For "cfx_max_linked_set". */
  40 #define MAX_LINKED_SET_MIN (0)
  41 #define MAX_LINKED_SET_MAX (UINT8_MAX)
  42 #define MAX_LINKED_SET_DEFAULT (10)
  43
  44 /* For "cfx_max_prebuilt_set". */
  45 #define MAX_PREBUILT_SET_MIN (0)
  46 #define MAX_PREBUILT_SET_MAX (UINT8_MAX)
  47 #define MAX_PREBUILT_SET_DEFAULT (3)
  48
  49 /* For "cfx_max_leg_retry". */
  50 #define MAX_UNLINKED_LEG_RETRY_DEFAULT (3)
  51 #define MAX_UNLINKED_LEG_RETRY_MIN (0)
  52 #define MAX_UNLINKED_LEG_RETRY_MAX (UINT8_MAX)
  53
  54 /* For "cfx_num_legs_set". */
  55 #define NUM_LEGS_SET_MIN (0)
  56 #define NUM_LEGS_SET_MAX (UINT8_MAX)
  57 #define NUM_LEGS_SET_DEFAULT (2)
  58
  59 /* For "cfx_max_legs_set" */
  60 #define MAX_LEGS_SET_MIN (3)
  61 #define MAX_LEGS_SET_MAX (UINT8_MAX)
  62 #define MAX_LEGS_SET_DEFAULT (8)
  63
  64 /* For "cfx_send_pct". */
  65 #define CFX_SEND_PCT_MIN (0)
  66 #define CFX_SEND_PCT_MAX (255)
  67 #define CFX_SEND_PCT_DFLT 100
  68
  69 /* For "cfx_drain_pct". */
  70 #define CFX_DRAIN_PCT_MIN (0)
  71 #define CFX_DRAIN_PCT_MAX (255)
  72 #define CFX_DRAIN_PCT_DFLT 0
  73
  74 /*
  75  * Cached consensus parameters.
  76  */
  77
  78 /* Indicate if conflux is enabled or disabled. */
  79 static bool conflux_enabled = CONFLUX_ENABLED_DEFAULT;
  80 /* Maximum number of linked set we are allowed to have (even if in use). */
  81 static uint8_t max_linked_set = MAX_LINKED_SET_DEFAULT;
  82 /* Maximum number of pre built set. */
  83 static uint8_t max_prebuilt_set = MAX_PREBUILT_SET_DEFAULT;
  84 /* Maximum number of unlinked leg retry that is how many times are we allowed
  85  * to retry a leg until it successfully links. */
  86 STATIC uint32_t max_unlinked_leg_retry = MAX_UNLINKED_LEG_RETRY_DEFAULT;
  87 /* Number of legs per set. */
  88 static uint8_t num_legs_set = NUM_LEGS_SET_DEFAULT;
  89 /* Maximum number of legs per set allowed at exits */
  90 static uint8_t max_legs_set = MAX_LEGS_SET_DEFAULT;
  91 /* The low Exit relay threshold, as a ratio between 0 and 1, used as a limit to
  92  * decide the amount of pre-built set we build depending on how many Exit relay
  93  * supports conflux in our current consensus. */
  94 static double low_exit_threshold_ratio =
  95   LOW_EXIT_THRESHOLD_DEFAULT / (double)LOW_EXIT_THRESHOLD_MAX;
  96
  97 static uint8_t cfx_drain_pct = CFX_DRAIN_PCT_DFLT;
  98 static uint8_t cfx_send_pct = CFX_SEND_PCT_DFLT;
  99
 100 /* Ratio of Exit relays in our consensus supporting conflux. This is computed
 101  * at every consensus and it is between 0 and 1. */
 102 static double exit_conflux_ratio = 0.0;
 103
 104 /** Sets num_conflux_exit with the latest count of Exits in the given consensus
 105  * that supports Conflux. */
 106 static void
 107 count_exit_with_conflux_support(const networkstatus_t *ns)
 108 {
 109   double supported = 0.0;
 110   int total_exits = 0;
 111
 112   if (!ns || smartlist_len(ns->routerstatus_list) == 0) {
 113     return;
 114   }
 115
 116   SMARTLIST_FOREACH_BEGIN(ns->routerstatus_list, const routerstatus_t *, rs) {
 117     if (!rs->is_exit || rs->is_bad_exit) {
 118       continue;
 119     }
 120     if (rs->pv.supports_conflux) {
 121       supported++;
 122     }
 123     total_exits++;
 124   } SMARTLIST_FOREACH_END(rs);
 125
 126   if (total_exits > 0) {
 127     exit_conflux_ratio =
 128       supported / total_exits;
 129   } else {
 130     exit_conflux_ratio = 0.0;
 131   }
 132
 133   log_info(LD_GENERAL, "Consensus has %.2f %% Exit relays supporting Conflux",
 134            exit_conflux_ratio * 100.0);
 135 }
 136
 137 /**
 138  * Return true iff conflux feature is enabled and usable for a given circuit.
 139  *
 140  * Circ may be NULL, in which case we only check the consensus and torrc. */
 141 bool
 142 conflux_is_enabled(const circuit_t *circ)
 143 {
 144   const or_options_t *opts = get_options();
 145
 146   /* Conflux CAN NOT operate properly without congestion control and so
 147    * automatically disabled conflux if we don't have CC enabled. */
 148   if (!congestion_control_enabled()) {
 149     return false;
 150   }
 151
 152   if (circ) {
 153     /* If circuit is non-null, we need to check to see if congestion
 154      * control was successfully negotiated. Conflux depends upon congestion
 155      * control, and consensus checks are not enough because there can be a
 156      * race between those checks and the consensus update to enable
 157      * congestion control. This happens in Shadow, and at relay restart. */
 158     if (CIRCUIT_IS_ORIGIN(circ)) {
 159       tor_assert(CONST_TO_ORIGIN_CIRCUIT(circ)->cpath);
 160       tor_assert(CONST_TO_ORIGIN_CIRCUIT(circ)->cpath->prev);
 161       if (!CONST_TO_ORIGIN_CIRCUIT(circ)->cpath->prev->ccontrol)
 162         return false;
 163     } else {
 164       if (!circ->ccontrol)
 165         return false;
 166     }
 167   }
 168
 169   /* For clients, this is mostly for sbws. For relays, this is an emergency
 170    * emergency override, in case a bug is discovered by a relay operator
 171    * and we can't set a consensus param fast enough. Basically gives them
 172    * an option other than downgrading. */
 173   if (opts->ConfluxEnabled != -1) {
 174     if (server_mode(opts)) {
 175       char *msg;
 176       static ratelim_t rlimit = RATELIM_INIT(60 * 60); /* Hourly */
 177       if ((msg = rate_limit_log(&rlimit, time(NULL)))) {
 178         log_warn(LD_GENERAL,
 179                  "This tor is a relay and ConfluxEnabled is set to 0. "
 180                  "We would ask you to please write to us on "
 181                  "tor-relays@lists.torproject.org or file a bug explaining "
 182                  "why you have disabled this option. Without news from you, "
 183                  "we might end up marking your relay as a BadExit.");
 184         tor_free(msg);
 185       }
 186     }
 187     return opts->ConfluxEnabled;
 188   }
 189
 190   return conflux_enabled;
 191 }
 192
 193 /** Return the maximum number of linked set we are allowed to have. */
 194 uint8_t
 195 conflux_params_get_max_linked_set(void)
 196 {
 197   return max_linked_set;
 198 }
 199
 200 /** Return the number of maximum pre built sets that is allowed to have. */
 201 uint8_t
 202 conflux_params_get_max_prebuilt(void)
 203 {
 204   /* Without any Exit supporting conflux, we won't be able to build a set. The
 205    * float problem here is minimal because exit_conflux_ratio is either a flat
 206    * 0 or else it means we do have at least an exit. */
 207   if (exit_conflux_ratio <= 0.0) {
 208     return 0;
 209   }
 210
 211   /* Allow only 1 pre built set if we are lower than the low exit threshold
 212    * parameter from the consensus. */
 213   if (exit_conflux_ratio < low_exit_threshold_ratio) {
 214     return 1;
 215   }
 216   return max_prebuilt_set;
 217 }
 218
 219 /** Return the maximum number of retry we can do until a leg links. */
 220 uint8_t
 221 conflux_params_get_max_unlinked_leg_retry(void)
 222 {
 223   return max_unlinked_leg_retry;
 224 }
 225
 226 /** Return the number of legs per set. */
 227 uint8_t
 228 conflux_params_get_num_legs_set(void)
 229 {
 230   return num_legs_set;
 231 }
 232
 233 /** Return the maximum number of legs per set. */
 234 uint8_t
 235 conflux_params_get_max_legs_set(void)
 236 {
 237   return max_legs_set;
 238 }
 239
 240 /** Return the drain percent we must hit before switching */
 241 uint8_t
 242 conflux_params_get_drain_pct(void)
 243 {
 244   return cfx_drain_pct;
 245 }
 246
 247 /** Return the percent of the congestion window to send before switching. */
 248 uint8_t
 249 conflux_params_get_send_pct(void)
 250 {
 251   return cfx_send_pct;
 252 }
 253
 254 /** Update global conflux related consensus parameter values, every consensus
 255  * update. */
 256 void
 257 conflux_params_new_consensus(const networkstatus_t *ns)
 258 {
 259   /* Params used by conflux_pool.c */
 260   conflux_enabled =
 261     networkstatus_get_param(ns, "cfx_enabled",
 262                             CONFLUX_ENABLED_DEFAULT,
 263                             CONFLUX_ENABLED_MIN, CONFLUX_ENABLED_MAX);
 264
 265   low_exit_threshold_ratio =
 266     networkstatus_get_param(ns, "cfx_low_exit_threshold",
 267                             LOW_EXIT_THRESHOLD_DEFAULT,
 268                             LOW_EXIT_THRESHOLD_MIN, LOW_EXIT_THRESHOLD_MAX) /
 269     (double)LOW_EXIT_THRESHOLD_MAX;
 270
 271   max_linked_set =
 272     networkstatus_get_param(ns, "cfx_max_linked_set",
 273                             MAX_LINKED_SET_DEFAULT,
 274                             MAX_LINKED_SET_MIN, MAX_LINKED_SET_MAX);
 275
 276   max_prebuilt_set =
 277     networkstatus_get_param(ns, "cfx_max_prebuilt_set",
 278                             MAX_PREBUILT_SET_DEFAULT,
 279                             MAX_PREBUILT_SET_MIN, MAX_PREBUILT_SET_MAX);
 280
 281   max_unlinked_leg_retry =
 282     networkstatus_get_param(ns, "cfx_max_unlinked_leg_retry",
 283                             MAX_UNLINKED_LEG_RETRY_DEFAULT,
 284                             MAX_UNLINKED_LEG_RETRY_MIN,
 285                             MAX_UNLINKED_LEG_RETRY_MAX);
 286
 287   num_legs_set =
 288     networkstatus_get_param(ns, "cfx_num_legs_set",
 289                             NUM_LEGS_SET_DEFAULT,
 290                             NUM_LEGS_SET_MIN, NUM_LEGS_SET_MAX);
 291
 292   max_legs_set =
 293     networkstatus_get_param(ns, "cfx_max_legs_set",
 294                             MAX_LEGS_SET_DEFAULT,
 295                             MAX_LEGS_SET_MIN, MAX_LEGS_SET_MAX);
 296
 297   /* Params used by conflux.c */
 298   cfx_send_pct = networkstatus_get_param(ns, "cfx_send_pct",
 299       CFX_SEND_PCT_DFLT,
 300       CFX_SEND_PCT_MIN,
 301       CFX_SEND_PCT_MAX);
 302
 303   cfx_drain_pct = networkstatus_get_param(ns, "cfx_drain_pct",
 304       CFX_DRAIN_PCT_DFLT,
 305       CFX_DRAIN_PCT_MIN,
 306       CFX_DRAIN_PCT_MAX);
 307
 308   count_exit_with_conflux_support(ns);
 309 }