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;
 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                 return si;
 147         }
 148
 149         return NULL;
 150 }
 151
 152 int
 153 usteer_snr_to_signal(struct usteer_node *node, int snr)
 154 {
 155         int noise = -95;
 156
 157         if (snr < 0)
 158                 return snr;
 159
 160         if (node->noise)
 161                 noise = node->noise;
 162
 163         return noise + snr;
 164 }
 165
 166 bool
 167 usteer_check_request(struct sta_info *si, enum usteer_event_type type)
 168 {
 169         struct uevent ev = {
 170                 .si_cur = si,
 171         };
 172         int min_signal;
 173         bool ret = true;
 174
 175         if (type == EVENT_TYPE_AUTH)
 176                 goto out;
 177
 178         if (type == EVENT_TYPE_ASSOC) {
 179                 /* Check if assoc request has lower signal than min_signal.
 180                  * If this is the case, block assoc even when assoc steering is enabled.
 181                  *
 182                  * Otherwise, the client potentially ends up in a assoc - kick loop.
 183                  */
 184                 if (config.min_snr && si->signal < usteer_snr_to_signal(si->node, config.min_snr)) {
 185                         ev.reason = UEV_REASON_LOW_SIGNAL;
 186                         ev.threshold.cur = si->signal;
 187                         ev.threshold.ref = usteer_snr_to_signal(si->node, config.min_snr);
 188                         ret = false;
 189                         goto out;
 190                 } else if (!config.assoc_steering) {
 191                         goto out;
 192                 }
 193         }
 194
 195         min_signal = usteer_snr_to_signal(si->node, config.min_connect_snr);
 196         if (si->signal < min_signal) {
 197                 ev.reason = UEV_REASON_LOW_SIGNAL;
 198                 ev.threshold.cur = si->signal;
 199                 ev.threshold.ref = min_signal;
 200                 ret = false;
 201                 goto out;
 202         }
 203
 204         if (current_time - si->created < config.initial_connect_delay) {
 205                 ev.reason = UEV_REASON_CONNECT_DELAY;
 206                 ev.threshold.cur = current_time - si->created;
 207                 ev.threshold.ref = config.initial_connect_delay;
 208                 ret = false;
 209                 goto out;
 210         }
 211
 212         if (!find_better_candidate(si, &ev, UEV_SELECT_REASON_ALL, 0))
 213                 goto out;
 214
 215         ev.reason = UEV_REASON_BETTER_CANDIDATE;
 216         ev.node_cur = si->node;
 217         ret = false;
 218
 219 out:
 220         switch (type) {
 221         case EVENT_TYPE_PROBE:
 222                 ev.type = UEV_PROBE_REQ_ACCEPT;
 223                 break;
 224         case EVENT_TYPE_ASSOC:
 225                 ev.type = UEV_ASSOC_REQ_ACCEPT;
 226                 break;
 227         case EVENT_TYPE_AUTH:
 228                 ev.type = UEV_AUTH_REQ_ACCEPT;
 229                 break;
 230         default:
 231                 break;
 232         }
 233
 234         if (!ret)
 235                 ev.type++;
 236
 237         if (!ret && si->stats[type].blocked_cur >= config.max_retry_band) {
 238                 ev.reason = UEV_REASON_RETRY_EXCEEDED;
 239                 ev.threshold.cur = si->stats[type].blocked_cur;
 240                 ev.threshold.ref = config.max_retry_band;
 241         }
 242         usteer_event(&ev);
 243
 244         return ret;
 245 }
 246
 247 static bool
 248 is_more_kickable(struct sta_info *si_cur, struct sta_info *si_new)
 249 {
 250         if (!si_cur)
 251                 return true;
 252
 253         if (si_new->kick_count > si_cur->kick_count)
 254                 return false;
 255
 256         return si_cur->signal > si_new->signal;
 257 }
 258
 259 static void
 260 usteer_roam_set_state(struct sta_info *si, enum roam_trigger_state state,
 261                       struct uevent *ev)
 262 {
 263         si->roam_event = current_time;
 264
 265         if (si->roam_state == state) {
 266                 if (si->roam_state == ROAM_TRIGGER_IDLE) {
 267                         si->roam_tries = 0;
 268                         return;
 269                 }
 270
 271                 si->roam_tries++;
 272         } else {
 273                 si->roam_tries = 0;
 274         }
 275
 276         si->roam_state = state;
 277         usteer_event(ev);
 278 }
 279
 280 static void
 281 usteer_roam_sm_start_scan(struct sta_info *si, struct uevent *ev)
 282 {
 283         /* Start scanning in case we are not timeout-constrained or timeout has expired */
 284         if (!config.roam_scan_timeout ||
 285             current_time > si->roam_scan_timeout_start + config.roam_scan_timeout) {
 286                 usteer_roam_set_state(si, ROAM_TRIGGER_SCAN, ev);
 287                 return;
 288         }
 289
 290         /* We are currently in scan timeout / cooldown.
 291          * Check if we are in ROAM_TRIGGER_IDLE state. Enter this state if not.
 292          */
 293         if (si->roam_state == ROAM_TRIGGER_IDLE)
 294                 return;
 295
 296         /* Enter idle state */
 297         usteer_roam_set_state(si, ROAM_TRIGGER_IDLE, ev);
 298 }
 299
 300 static bool
 301 usteer_roam_sm_found_better_node(struct sta_info *si, struct uevent *ev, enum roam_trigger_state next_state)
 302 {
 303         uint64_t max_age = 2 * config.roam_scan_interval;
 304
 305         if (max_age > current_time - si->roam_scan_start)
 306                 max_age = current_time - si->roam_scan_start;
 307
 308         if (find_better_candidate(si, ev, (1 << UEV_SELECT_REASON_SIGNAL), max_age)) {
 309                 usteer_roam_set_state(si, next_state, ev);
 310                 return true;
 311         }
 312
 313         return false;
 314 }
 315
 316 static bool
 317 usteer_roam_trigger_sm(struct usteer_local_node *ln, struct sta_info *si)
 318 {
 319         struct uevent ev = {
 320                 .si_cur = si,
 321         };
 322
 323         switch (si->roam_state) {
 324         case ROAM_TRIGGER_SCAN:
 325                 if (!si->roam_tries) {
 326                         si->roam_scan_start = current_time;
 327                 }
 328
 329                 /* Check if we've found a better node regardless of the scan-interval */
 330                 if (usteer_roam_sm_found_better_node(si, &ev, ROAM_TRIGGER_SCAN_DONE))
 331                         break;
 332
 333                 /* Only scan every scan-interval */
 334                 if (current_time - si->roam_event < config.roam_scan_interval)
 335                         break;
 336
 337                 /* Check if no node was found within roam_scan_tries tries */
 338                 if (config.roam_scan_tries && si->roam_tries >= config.roam_scan_tries) {
 339                         if (!config.roam_scan_timeout) {
 340                                 /* Prepare to kick client */
 341                                 usteer_roam_set_state(si, ROAM_TRIGGER_SCAN_DONE, &ev);
 342                         } else {
 343                                 /* Kick in scan timeout */
 344                                 si->roam_scan_timeout_start = current_time;
 345                                 usteer_roam_set_state(si, ROAM_TRIGGER_IDLE, &ev);
 346                         }
 347                         break;
 348                 }
 349
 350                 /* Send beacon-request to client */
 351                 usteer_ubus_trigger_client_scan(si);
 352                 usteer_roam_sm_start_scan(si, &ev);
 353                 break;
 354
 355         case ROAM_TRIGGER_IDLE:
 356                 usteer_roam_sm_start_scan(si, &ev);
 357                 break;
 358
 359         case ROAM_TRIGGER_SCAN_DONE:
 360                 usteer_ubus_bss_transition_request(si, 1, false, false, 100);
 361                 si->kick_time = current_time;
 362                 usteer_roam_set_state(si, ROAM_TRIGGER_IDLE, &ev);
 363                 break;
 364         }
 365
 366         return false;
 367 }
 368
 369 static void
 370 usteer_local_node_roam_check(struct usteer_local_node *ln, struct uevent *ev)
 371 {
 372         struct sta_info *si;
 373         int min_signal;
 374
 375         if (config.roam_scan_snr)
 376                 min_signal = config.roam_scan_snr;
 377         else if (config.roam_trigger_snr)
 378                 min_signal = config.roam_trigger_snr;
 379         else
 380                 return;
 381
 382         usteer_update_time();
 383         min_signal = usteer_snr_to_signal(&ln->node, min_signal);
 384
 385         list_for_each_entry(si, &ln->node.sta_info, node_list) {
 386                 if (si->connected != STA_CONNECTED || si->signal >= min_signal ||
 387                         si->kick_time ||
 388                     current_time - si->roam_kick < config.roam_trigger_interval) {
 389                         usteer_roam_set_state(si, ROAM_TRIGGER_IDLE, ev);
 390                         continue;
 391                 }
 392
 393                 /*
 394                  * If the state machine kicked a client, other clients should wait
 395                  * until the next turn
 396                  */
 397                 if (usteer_roam_trigger_sm(ln, si))
 398                         return;
 399         }
 400 }
 401
 402 static void
 403 usteer_local_node_snr_kick(struct usteer_local_node *ln)
 404 {
 405         unsigned int min_count = DIV_ROUND_UP(config.min_snr_kick_delay, config.local_sta_update);
 406         struct uevent ev = {
 407                 .node_local = &ln->node,
 408         };
 409         struct sta_info *si;
 410         int min_signal;
 411
 412         if (!config.min_snr)
 413                 return;
 414
 415         min_signal = usteer_snr_to_signal(&ln->node, config.min_snr);
 416         ev.threshold.ref = min_signal;
 417
 418         list_for_each_entry(si, &ln->node.sta_info, node_list) {
 419                 if (si->connected != STA_CONNECTED)
 420                         continue;
 421
 422                 if (si->signal >= min_signal) {
 423                         si->below_min_snr = 0;
 424                         continue;
 425                 } else {
 426                         si->below_min_snr++;
 427                 }
 428
 429                 if (si->below_min_snr <= min_count)
 430                         continue;
 431
 432                 si->kick_count++;
 433
 434                 ev.type = UEV_SIGNAL_KICK;
 435                 ev.threshold.cur = si->signal;
 436                 ev.count = si->kick_count;
 437                 usteer_event(&ev);
 438
 439                 usteer_ubus_kick_client(si);
 440                 return;
 441         }
 442 }
 443
 444 static void
 445 usteer_local_node_load_kick(struct usteer_local_node *ln)
 446 {
 447         struct usteer_node *node = &ln->node;
 448         struct sta_info *kick1 = NULL, *kick2 = NULL;
 449         struct sta_info *candidate = NULL;
 450         struct sta_info *si;
 451         struct uevent ev = {
 452                 .node_local = &ln->node,
 453         };
 454         unsigned int min_count = DIV_ROUND_UP(config.load_kick_delay, config.local_sta_update);
 455
 456         if (!config.load_kick_enabled || !config.load_kick_threshold ||
 457             !config.load_kick_delay)
 458                 return;
 459
 460         if (node->load < config.load_kick_threshold) {
 461                 if (!ln->load_thr_count)
 462                         return;
 463
 464                 ln->load_thr_count = 0;
 465                 ev.type = UEV_LOAD_KICK_RESET;
 466                 ev.threshold.cur = node->load;
 467                 ev.threshold.ref = config.load_kick_threshold;
 468                 goto out;
 469         }
 470
 471         if (++ln->load_thr_count <= min_count) {
 472                 if (ln->load_thr_count > 1)
 473                         return;
 474
 475                 ev.type = UEV_LOAD_KICK_TRIGGER;
 476                 ev.threshold.cur = node->load;
 477                 ev.threshold.ref = config.load_kick_threshold;
 478                 goto out;
 479         }
 480
 481         ln->load_thr_count = 0;
 482         if (node->n_assoc < config.load_kick_min_clients) {
 483                 ev.type = UEV_LOAD_KICK_MIN_CLIENTS;
 484                 ev.threshold.cur = node->n_assoc;
 485                 ev.threshold.ref = config.load_kick_min_clients;
 486                 goto out;
 487         }
 488
 489         list_for_each_entry(si, &ln->node.sta_info, node_list) {
 490                 struct sta_info *tmp;
 491
 492                 if (si->connected != STA_CONNECTED)
 493                         continue;
 494
 495                 if (is_more_kickable(kick1, si))
 496                         kick1 = si;
 497
 498                 tmp = find_better_candidate(si, NULL, (1 << UEV_SELECT_REASON_LOAD), 0);
 499                 if (!tmp)
 500                         continue;
 501
 502                 if (is_more_kickable(kick2, si)) {
 503                         kick2 = si;
 504                         candidate = tmp;
 505                 }
 506         }
 507
 508         if (!kick1) {
 509                 ev.type = UEV_LOAD_KICK_NO_CLIENT;
 510                 goto out;
 511         }
 512
 513         if (kick2)
 514                 kick1 = kick2;
 515
 516         kick1->kick_count++;
 517
 518         ev.type = UEV_LOAD_KICK_CLIENT;
 519         ev.si_cur = kick1;
 520         ev.si_other = candidate;
 521         ev.count = kick1->kick_count;
 522
 523         usteer_ubus_kick_client(kick1);
 524
 525 out:
 526         usteer_event(&ev);
 527 }
 528
 529 static void
 530 usteer_local_node_perform_kick(struct usteer_local_node *ln)
 531 {
 532         struct sta_info *si;
 533
 534         list_for_each_entry(si, &ln->node.sta_info, node_list) {
 535                 if (!si->kick_time || si->kick_time > current_time)
 536                         continue;
 537
 538                 usteer_ubus_kick_client(si);
 539         }
 540 }
 541
 542 void
 543 usteer_local_node_kick(struct usteer_local_node *ln)
 544 {
 545         struct uevent ev = {
 546                 .node_local = &ln->node,
 547         };
 548
 549         usteer_local_node_perform_kick(ln);
 550
 551         usteer_local_node_snr_kick(ln);
 552         usteer_local_node_load_kick(ln);
 553         usteer_local_node_roam_check(ln, &ev);
 554 }