policy.c

   1 /*
   2  *   This program is free software; you can redistribute it and/or modify
   3  *   it under the terms of the GNU General Public License as published by
   4  *   the Free Software Foundation; either version 2 of the License.
   5  *
   6  *   This program is distributed in the hope that it will be useful,
   7  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
   8  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   9  *   GNU General Public License for more details.
  10  *
  11  *   You should have received a copy of the GNU General Public License
  12  *   along with this program; if not, write to the Free Software
  13  *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
  14  *
  15  *   Copyright (C) 2020 embedd.ch
  16  *   Copyright (C) 2020 Felix Fietkau <nbd@nbd.name>
  17  *   Copyright (C) 2020 John Crispin <john@phrozen.org>
  18  */
  19
  20 #include "usteer.h"
  21 #include "node.h"
  22 #include "event.h"
  23
  24 static bool
  25 below_assoc_threshold(struct usteer_node *node_cur, struct usteer_node *node_new)
  26 {
  27         int n_assoc_cur = node_cur->n_assoc;
  28         int n_assoc_new = node_new->n_assoc;
  29         bool ref_5g = node_cur->freq > 4000;
  30         bool node_5g = node_new->freq > 4000;
  31
  32         if (ref_5g && !node_5g)
  33                 n_assoc_new += config.band_steering_threshold;
  34         else if (!ref_5g && node_5g)
  35                 n_assoc_cur += config.band_steering_threshold;
  36
  37         n_assoc_new += config.load_balancing_threshold;
  38
  39         return n_assoc_new <= n_assoc_cur;
  40 }
  41
  42 static bool
  43 better_signal_strength(int signal_cur, int signal_new)
  44 {
  45         const bool is_better = signal_new - signal_cur
  46                                 > (int) config.signal_diff_threshold;
  47
  48         if (!config.signal_diff_threshold)
  49                 return false;
  50
  51         return is_better;
  52 }
  53
  54 static bool
  55 below_load_threshold(struct usteer_node *node)
  56 {
  57         return node->n_assoc >= config.load_kick_min_clients &&
  58                node->load > config.load_kick_threshold;
  59 }
  60
  61 static bool
  62 has_better_load(struct usteer_node *node_cur, struct usteer_node *node_new)
  63 {
  64         return !below_load_threshold(node_cur) && below_load_threshold(node_new);
  65 }
  66
  67 bool
  68 usteer_policy_node_below_max_assoc(struct usteer_node *node)
  69 {
  70         return !node->max_assoc || node->n_assoc < node->max_assoc;
  71 }
  72
  73 static bool
  74 over_min_signal(struct usteer_node *node, int signal)
  75 {
  76         if (config.min_snr && signal < usteer_snr_to_signal(node, config.min_snr))
  77                 return false;
  78
  79         if (config.roam_trigger_snr && signal < usteer_snr_to_signal(node, config.roam_trigger_snr))
  80                 return false;
  81
  82         return true;
  83 }
  84
  85 static uint32_t
  86 is_better_candidate(struct sta_info *si_cur, struct sta_info *si_new)
  87 {
  88         struct usteer_node *current_node = si_cur->node;
  89         struct usteer_node *new_node = si_new->node;
  90         int current_signal = si_cur->signal;
  91         int new_signal = si_new->signal;
  92         uint32_t reasons = 0;
  93
  94         if (!usteer_policy_node_below_max_assoc(new_node))
  95                 return 0;
  96
  97         if (!over_min_signal(new_node, new_signal))
  98                 return 0;
  99
 100         if (below_assoc_threshold(current_node, new_node) &&
 101             !below_assoc_threshold(new_node, current_node))
 102                 reasons |= (1 << UEV_SELECT_REASON_NUM_ASSOC);
 103
 104         if (better_signal_strength(current_signal, new_signal))
 105                 reasons |= (1 << UEV_SELECT_REASON_SIGNAL);
 106
 107         if (has_better_load(current_node, new_node) &&
 108                 !has_better_load(current_node, new_node))
 109                 reasons |= (1 << UEV_SELECT_REASON_LOAD);
 110
 111         return reasons;
 112 }
 113
 114 static struct sta_info *
 115 find_better_candidate(struct sta_info *si_ref, struct uevent *ev, uint32_t required_criteria, uint64_t max_age)
 116 {
 117         struct sta_info *si, *candidate = NULL;
 118         struct sta *sta = si_ref->sta;
 119         uint32_t reasons;
 120
 121         list_for_each_entry(si, &sta->nodes, list) {
 122                 if (si == si_ref)
 123                         continue;
 124
 125                 if (current_time - si->seen > config.seen_policy_timeout)
 126                         continue;
 127
 128                 if (strcmp(si->node->ssid, si_ref->node->ssid) != 0)
 129                         continue;
 130
 131                 if (max_age && max_age < current_time - si->seen)
 132                         continue;
 133
 134                 reasons = is_better_candidate(si_ref, si);
 135                 if (!reasons)
 136                         continue;
 137
 138                 if (!(reasons & required_criteria))
 139                         continue;
 140
 141                 if (ev) {
 142                         ev->si_other = si;
 143                         ev->select_reasons = reasons;
 144                 }
 145
 146                 if (candidate && si->signal > candidate->signal)
 147                         candidate = si;
 148         }
 149
 150         return candidate;
 151 }
 152
 153 int
 154 usteer_snr_to_signal(struct usteer_node *node, int snr)
 155 {
 156         int noise = -95;
 157
 158         if (snr < 0)
 159                 return snr;
 160
 161         if (node->noise)
 162                 noise = node->noise;
 163
 164         return noise + snr;
 165 }
 166
 167 bool
 168 usteer_check_request(struct sta_info *si, enum usteer_event_type type)
 169 {
 170         struct uevent ev = {
 171                 .si_cur = si,
 172         };
 173         int min_signal;
 174         bool ret = true;
 175
 176         if (type == EVENT_TYPE_AUTH)
 177                 goto out;
 178
 179         if (type == EVENT_TYPE_ASSOC) {
 180                 /* Check if assoc request has lower signal than min_signal.
 181                  * If this is the case, block assoc even when assoc steering is enabled.
 182                  *
 183                  * Otherwise, the client potentially ends up in a assoc - kick loop.
 184                  */
 185                 if (config.min_snr && si->signal < usteer_snr_to_signal(si->node, config.min_snr)) {
 186                         ev.reason = UEV_REASON_LOW_SIGNAL;
 187                         ev.threshold.cur = si->signal;
 188                         ev.threshold.ref = usteer_snr_to_signal(si->node, config.min_snr);
 189                         ret = false;
 190                         goto out;
 191                 } else if (!config.assoc_steering) {
 192                         goto out;
 193                 }
 194         }
 195
 196         min_signal = usteer_snr_to_signal(si->node, config.min_connect_snr);
 197         if (si->signal < min_signal) {
 198                 ev.reason = UEV_REASON_LOW_SIGNAL;
 199                 ev.threshold.cur = si->signal;
 200                 ev.threshold.ref = min_signal;
 201                 ret = false;
 202                 goto out;
 203         }
 204
 205         if (current_time - si->created < config.initial_connect_delay) {
 206                 ev.reason = UEV_REASON_CONNECT_DELAY;
 207                 ev.threshold.cur = current_time - si->created;
 208                 ev.threshold.ref = config.initial_connect_delay;
 209                 ret = false;
 210                 goto out;
 211         }
 212
 213         if (!find_better_candidate(si, &ev, UEV_SELECT_REASON_ALL, 0))
 214                 goto out;
 215
 216         ev.reason = UEV_REASON_BETTER_CANDIDATE;
 217         ev.node_cur = si->node;
 218         ret = false;
 219
 220 out:
 221         switch (type) {
 222         case EVENT_TYPE_PROBE:
 223                 ev.type = UEV_PROBE_REQ_ACCEPT;
 224                 break;
 225         case EVENT_TYPE_ASSOC:
 226                 ev.type = UEV_ASSOC_REQ_ACCEPT;
 227                 break;
 228         case EVENT_TYPE_AUTH:
 229                 ev.type = UEV_AUTH_REQ_ACCEPT;
 230                 break;
 231         default:
 232                 break;
 233         }
 234
 235         if (!ret)
 236                 ev.type++;
 237
 238         if (!ret && si->stats[type].blocked_cur >= config.max_retry_band) {
 239                 ev.reason = UEV_REASON_RETRY_EXCEEDED;
 240                 ev.threshold.cur = si->stats[type].blocked_cur;
 241                 ev.threshold.ref = config.max_retry_band;
 242         }
 243         usteer_event(&ev);
 244
 245         return ret;
 246 }
 247
 248 static bool
 249 is_more_kickable(struct sta_info *si_cur, struct sta_info *si_new)
 250 {
 251         if (!si_cur)
 252                 return true;
 253
 254         if (si_new->kick_count > si_cur->kick_count)
 255                 return false;
 256
 257         return si_cur->signal > si_new->signal;
 258 }
 259
 260 static void
 261 usteer_roam_set_state(struct sta_info *si, enum roam_trigger_state state,
 262                       struct uevent *ev)
 263 {
 264         si->roam_event = current_time;
 265
 266         if (si->roam_state == state) {
 267                 if (si->roam_state == ROAM_TRIGGER_IDLE) {
 268                         si->roam_tries = 0;
 269                         return;
 270                 }
 271
 272                 si->roam_tries++;
 273         } else {
 274                 si->roam_tries = 0;
 275         }
 276
 277         si->roam_state = state;
 278         usteer_event(ev);
 279 }
 280
 281 static void
 282 usteer_roam_sm_start_scan(struct sta_info *si, struct uevent *ev)
 283 {
 284         /* Start scanning in case we are not timeout-constrained or timeout has expired */
 285         if (!config.roam_scan_timeout ||
 286             current_time > si->roam_scan_timeout_start + config.roam_scan_timeout) {
 287                 usteer_roam_set_state(si, ROAM_TRIGGER_SCAN, ev);
 288                 return;
 289         }
 290
 291         /* We are currently in scan timeout / cooldown.
 292          * Check if we are in ROAM_TRIGGER_IDLE state. Enter this state if not.
 293          */
 294         if (si->roam_state == ROAM_TRIGGER_IDLE)
 295                 return;
 296
 297         /* Enter idle state */
 298         usteer_roam_set_state(si, ROAM_TRIGGER_IDLE, ev);
 299 }
 300
 301 static struct sta_info *
 302 usteer_roam_sm_found_better_node(struct sta_info *si, struct uevent *ev, enum roam_trigger_state next_state)
 303 {
 304         uint64_t max_age = 2 * config.roam_scan_interval;
 305         struct sta_info *candidate;
 306
 307         if (max_age > current_time - si->roam_scan_start)
 308                 max_age = current_time - si->roam_scan_start;
 309
 310         candidate = find_better_candidate(si, ev, (1 << UEV_SELECT_REASON_SIGNAL), max_age);
 311         if (candidate)
 312                 usteer_roam_set_state(si, next_state, ev);
 313
 314         return candidate;
 315 }
 316
 317 static bool
 318 usteer_roam_trigger_sm(struct usteer_local_node *ln, struct sta_info *si)
 319 {
 320         struct sta_info *candidate;
 321         struct uevent ev = {
 322                 .si_cur = si,
 323         };
 324
 325         switch (si->roam_state) {
 326         case ROAM_TRIGGER_SCAN:
 327                 if (!si->roam_tries) {
 328                         si->roam_scan_start = current_time;
 329                 }
 330
 331                 /* Check if we've found a better node regardless of the scan-interval */
 332                 if (usteer_roam_sm_found_better_node(si, &ev, ROAM_TRIGGER_SCAN_DONE))
 333                         break;
 334
 335                 /* Only scan every scan-interval */
 336                 if (current_time - si->roam_event < config.roam_scan_interval)
 337                         break;
 338
 339                 /* Check if no node was found within roam_scan_tries tries */
 340                 if (config.roam_scan_tries && si->roam_tries >= config.roam_scan_tries) {
 341                         if (!config.roam_scan_timeout) {
 342                                 /* Prepare to kick client */
 343                                 usteer_roam_set_state(si, ROAM_TRIGGER_SCAN_DONE, &ev);
 344                         } else {
 345                                 /* Kick in scan timeout */
 346                                 si->roam_scan_timeout_start = current_time;
 347                                 usteer_roam_set_state(si, ROAM_TRIGGER_IDLE, &ev);
 348                         }
 349                         break;
 350                 }
 351
 352                 /* Send beacon-request to client */
 353                 usteer_ubus_trigger_client_scan(si);
 354                 usteer_roam_sm_start_scan(si, &ev);
 355                 break;
 356
 357         case ROAM_TRIGGER_IDLE:
 358                 usteer_roam_sm_start_scan(si, &ev);
 359                 break;
 360
 361         case ROAM_TRIGGER_SCAN_DONE:
 362                 candidate = usteer_roam_sm_found_better_node(si, &ev, ROAM_TRIGGER_SCAN_DONE);
 363                 /* Kick back in case no better node is found */
 364                 if (!candidate)
 365                         usteer_roam_set_state(si, ROAM_TRIGGER_IDLE, &ev);
 366
 367                 usteer_ubus_bss_transition_request(si, 1, false, false, 100, candidate->node);
 368                 si->kick_time = current_time;
 369                 usteer_roam_set_state(si, ROAM_TRIGGER_IDLE, &ev);
 370                 break;
 371         }
 372
 373         return false;
 374 }
 375
 376 static void
 377 usteer_local_node_roam_check(struct usteer_local_node *ln, struct uevent *ev)
 378 {
 379         struct sta_info *si;
 380         int min_signal;
 381
 382         if (config.roam_scan_snr)
 383                 min_signal = config.roam_scan_snr;
 384         else if (config.roam_trigger_snr)
 385                 min_signal = config.roam_trigger_snr;
 386         else
 387                 return;
 388
 389         usteer_update_time();
 390         min_signal = usteer_snr_to_signal(&ln->node, min_signal);
 391
 392         list_for_each_entry(si, &ln->node.sta_info, node_list) {
 393                 if (si->connected != STA_CONNECTED || si->signal >= min_signal ||
 394                         si->kick_time ||
 395                         (si->bss_transition_response.status_code && current_time - si->bss_transition_response.timestamp < config.steer_reject_timeout) ||
 396                     current_time - si->roam_kick < config.roam_trigger_interval) {
 397                         usteer_roam_set_state(si, ROAM_TRIGGER_IDLE, ev);
 398                         continue;
 399                 }
 400
 401                 /*
 402                  * If the state machine kicked a client, other clients should wait
 403                  * until the next turn
 404                  */
 405                 if (usteer_roam_trigger_sm(ln, si))
 406                         return;
 407         }
 408 }
 409
 410 static void
 411 usteer_local_node_snr_kick(struct usteer_local_node *ln)
 412 {
 413         unsigned int min_count = DIV_ROUND_UP(config.min_snr_kick_delay, config.local_sta_update);
 414         struct uevent ev = {
 415                 .node_local = &ln->node,
 416         };
 417         struct sta_info *si;
 418         int min_signal;
 419
 420         if (!config.min_snr)
 421                 return;
 422
 423         min_signal = usteer_snr_to_signal(&ln->node, config.min_snr);
 424         ev.threshold.ref = min_signal;
 425
 426         list_for_each_entry(si, &ln->node.sta_info, node_list) {
 427                 if (si->connected != STA_CONNECTED)
 428                         continue;
 429
 430                 if (si->signal >= min_signal) {
 431                         si->below_min_snr = 0;
 432                         continue;
 433                 } else {
 434                         si->below_min_snr++;
 435                 }
 436
 437                 if (si->below_min_snr <= min_count)
 438                         continue;
 439
 440                 si->kick_count++;
 441
 442                 ev.type = UEV_SIGNAL_KICK;
 443                 ev.threshold.cur = si->signal;
 444                 ev.count = si->kick_count;
 445                 usteer_event(&ev);
 446
 447                 usteer_ubus_kick_client(si);
 448                 return;
 449         }
 450 }
 451
 452 static void
 453 usteer_local_node_load_kick(struct usteer_local_node *ln)
 454 {
 455         struct usteer_node *node = &ln->node;
 456         struct sta_info *kick1 = NULL, *kick2 = NULL;
 457         struct sta_info *candidate = NULL;
 458         struct sta_info *si;
 459         struct uevent ev = {
 460                 .node_local = &ln->node,
 461         };
 462         unsigned int min_count = DIV_ROUND_UP(config.load_kick_delay, config.local_sta_update);
 463
 464         if (!config.load_kick_enabled || !config.load_kick_threshold ||
 465             !config.load_kick_delay)
 466                 return;
 467
 468         if (node->load < config.load_kick_threshold) {
 469                 if (!ln->load_thr_count)
 470                         return;
 471
 472                 ln->load_thr_count = 0;
 473                 ev.type = UEV_LOAD_KICK_RESET;
 474                 ev.threshold.cur = node->load;
 475                 ev.threshold.ref = config.load_kick_threshold;
 476                 goto out;
 477         }
 478
 479         if (++ln->load_thr_count <= min_count) {
 480                 if (ln->load_thr_count > 1)
 481                         return;
 482
 483                 ev.type = UEV_LOAD_KICK_TRIGGER;
 484                 ev.threshold.cur = node->load;
 485                 ev.threshold.ref = config.load_kick_threshold;
 486                 goto out;
 487         }
 488
 489         ln->load_thr_count = 0;
 490         if (node->n_assoc < config.load_kick_min_clients) {
 491                 ev.type = UEV_LOAD_KICK_MIN_CLIENTS;
 492                 ev.threshold.cur = node->n_assoc;
 493                 ev.threshold.ref = config.load_kick_min_clients;
 494                 goto out;
 495         }
 496
 497         list_for_each_entry(si, &ln->node.sta_info, node_list) {
 498                 struct sta_info *tmp;
 499
 500                 if (si->connected != STA_CONNECTED)
 501                         continue;
 502
 503                 if (is_more_kickable(kick1, si))
 504                         kick1 = si;
 505
 506                 tmp = find_better_candidate(si, NULL, (1 << UEV_SELECT_REASON_LOAD), 0);
 507                 if (!tmp)
 508                         continue;
 509
 510                 if (is_more_kickable(kick2, si)) {
 511                         kick2 = si;
 512                         candidate = tmp;
 513                 }
 514         }
 515
 516         if (!kick1) {
 517                 ev.type = UEV_LOAD_KICK_NO_CLIENT;
 518                 goto out;
 519         }
 520
 521         if (kick2)
 522                 kick1 = kick2;
 523
 524         kick1->kick_count++;
 525
 526         ev.type = UEV_LOAD_KICK_CLIENT;
 527         ev.si_cur = kick1;
 528         ev.si_other = candidate;
 529         ev.count = kick1->kick_count;
 530
 531         usteer_ubus_kick_client(kick1);
 532
 533 out:
 534         usteer_event(&ev);
 535 }
 536
 537 static void
 538 usteer_local_node_perform_kick(struct usteer_local_node *ln)
 539 {
 540         struct sta_info *si;
 541
 542         list_for_each_entry(si, &ln->node.sta_info, node_list) {
 543                 if (!si->kick_time || si->kick_time > current_time)
 544                         continue;
 545
 546                 usteer_ubus_kick_client(si);
 547         }
 548 }
 549
 550 void
 551 usteer_local_node_kick(struct usteer_local_node *ln)
 552 {
 553         struct uevent ev = {
 554                 .node_local = &ln->node,
 555         };
 556
 557         usteer_local_node_perform_kick(ln);
 558
 559         usteer_local_node_snr_kick(ln);
 560         usteer_local_node_load_kick(ln);
 561         usteer_local_node_roam_check(ln, &ev);
 562 }