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 sta_info *si_cur, struct sta_info *si_new)
  26 {
  27         int n_assoc_cur = si_cur->node->n_assoc;
  28         int n_assoc_new = si_new->node->n_assoc;
  29         bool ref_5g = si_cur->node->freq > 4000;
  30         bool node_5g = si_new->node->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(struct sta_info *si_cur, struct sta_info *si_new)
  44 {
  45         const bool is_better = si_new->signal - si_cur->signal
  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 sta_info *si)
  56 {
  57         return si->node->n_assoc >= config.load_kick_min_clients &&
  58                si->node->load > config.load_kick_threshold;
  59 }
  60
  61 static bool
  62 has_better_load(struct sta_info *si_cur, struct sta_info *si_new)
  63 {
  64         return !below_load_threshold(si_cur) && below_load_threshold(si_new);
  65 }
  66
  67 static bool
  68 below_max_assoc(struct sta_info *si)
  69 {
  70         struct usteer_node *node = si->node;
  71
  72         return !node->max_assoc || node->n_assoc < node->max_assoc;
  73 }
  74
  75 static uint32_t
  76 is_better_candidate(struct sta_info *si_cur, struct sta_info *si_new)
  77 {
  78         uint32_t reasons = 0;
  79
  80         if (!below_max_assoc(si_new))
  81                 return 0;
  82
  83         if (below_assoc_threshold(si_cur, si_new) &&
  84             !below_assoc_threshold(si_new, si_cur))
  85                 reasons |= (1 << UEV_SELECT_REASON_NUM_ASSOC);
  86
  87         if (better_signal_strength(si_cur, si_new))
  88                 reasons |= (1 << UEV_SELECT_REASON_SIGNAL);
  89
  90         if (has_better_load(si_cur, si_new) &&
  91                 !has_better_load(si_cur, si_new))
  92                 reasons |= (1 << UEV_SELECT_REASON_LOAD);
  93
  94         return reasons;
  95 }
  96
  97 static struct sta_info *
  98 find_better_candidate(struct sta_info *si_ref, struct uevent *ev)
  99 {
 100         struct sta_info *si;
 101         struct sta *sta = si_ref->sta;
 102         uint32_t reasons;
 103
 104         list_for_each_entry(si, &sta->nodes, list) {
 105                 if (si == si_ref)
 106                         continue;
 107
 108                 if (current_time - si->seen > config.seen_policy_timeout)
 109                         continue;
 110
 111                 if (strcmp(si->node->ssid, si_ref->node->ssid) != 0)
 112                         continue;
 113
 114                 reasons = is_better_candidate(si_ref, si);
 115                 if (!reasons)
 116                         continue;
 117
 118                 if (is_better_candidate(si, si_ref))
 119                         continue;
 120
 121                 if (ev) {
 122                         ev->si_other = si;
 123                         ev->select_reasons = reasons;
 124                 }
 125
 126                 return si;
 127         }
 128
 129         return NULL;
 130 }
 131
 132 static int
 133 snr_to_signal(struct usteer_node *node, int snr)
 134 {
 135         int noise = -95;
 136
 137         if (snr < 0)
 138                 return snr;
 139
 140         if (node->noise)
 141                 noise = node->noise;
 142
 143         return noise + snr;
 144 }
 145
 146 bool
 147 usteer_check_request(struct sta_info *si, enum usteer_event_type type)
 148 {
 149         struct uevent ev = {
 150                 .si_cur = si,
 151         };
 152         int min_signal;
 153         bool ret = true;
 154
 155         if (type == EVENT_TYPE_AUTH)
 156                 goto out;
 157
 158         if (type == EVENT_TYPE_ASSOC) {
 159                 /* Check if assoc request has lower signal than min_signal.
 160                  * If this is the case, block assoc even when assoc steering is enabled.
 161                  *
 162                  * Otherwise, the client potentially ends up in a assoc - kick loop.
 163                  */
 164                 if (config.min_snr && si->signal < snr_to_signal(si->node, config.min_snr)) {
 165                         ev.reason = UEV_REASON_LOW_SIGNAL;
 166                         ev.threshold.cur = si->signal;
 167                         ev.threshold.ref = min_signal;
 168                         ret = false;
 169                         goto out;
 170                 } else if (!config.assoc_steering) {
 171                         goto out;
 172                 }
 173         }
 174
 175         min_signal = snr_to_signal(si->node, config.min_connect_snr);
 176         if (si->signal < min_signal) {
 177                 ev.reason = UEV_REASON_LOW_SIGNAL;
 178                 ev.threshold.cur = si->signal;
 179                 ev.threshold.ref = min_signal;
 180                 ret = false;
 181                 goto out;
 182         }
 183
 184         if (current_time - si->created < config.initial_connect_delay) {
 185                 ev.reason = UEV_REASON_CONNECT_DELAY;
 186                 ev.threshold.cur = current_time - si->created;
 187                 ev.threshold.ref = config.initial_connect_delay;
 188                 ret = false;
 189                 goto out;
 190         }
 191
 192         if (!find_better_candidate(si, &ev))
 193                 goto out;
 194
 195         ev.reason = UEV_REASON_BETTER_CANDIDATE;
 196         ev.node_cur = si->node;
 197         ret = false;
 198
 199 out:
 200         switch (type) {
 201         case EVENT_TYPE_PROBE:
 202                 ev.type = UEV_PROBE_REQ_ACCEPT;
 203                 break;
 204         case EVENT_TYPE_ASSOC:
 205                 ev.type = UEV_ASSOC_REQ_ACCEPT;
 206                 break;
 207         case EVENT_TYPE_AUTH:
 208                 ev.type = UEV_AUTH_REQ_ACCEPT;
 209                 break;
 210         default:
 211                 break;
 212         }
 213
 214         if (!ret)
 215                 ev.type++;
 216
 217         if (!ret && si->stats[type].blocked_cur >= config.max_retry_band) {
 218                 ev.reason = UEV_REASON_RETRY_EXCEEDED;
 219                 ev.threshold.cur = si->stats[type].blocked_cur;
 220                 ev.threshold.ref = config.max_retry_band;
 221         }
 222         usteer_event(&ev);
 223
 224         return ret;
 225 }
 226
 227 static bool
 228 is_more_kickable(struct sta_info *si_cur, struct sta_info *si_new)
 229 {
 230         if (!si_cur)
 231                 return true;
 232
 233         if (si_new->kick_count > si_cur->kick_count)
 234                 return false;
 235
 236         return si_cur->signal > si_new->signal;
 237 }
 238
 239 static void
 240 usteer_roam_set_state(struct sta_info *si, enum roam_trigger_state state,
 241                       struct uevent *ev)
 242 {
 243         si->roam_event = current_time;
 244
 245         if (si->roam_state == state) {
 246                 if (si->roam_state == ROAM_TRIGGER_IDLE) {
 247                         si->roam_tries = 0;
 248                         return;
 249                 }
 250
 251                 si->roam_tries++;
 252         } else {
 253                 si->roam_tries = 0;
 254         }
 255
 256         si->roam_state = state;
 257         usteer_event(ev);
 258 }
 259
 260 static bool
 261 usteer_roam_trigger_sm(struct sta_info *si)
 262 {
 263         struct uevent ev = {
 264                 .si_cur = si,
 265         };
 266         int min_signal;
 267
 268         min_signal = snr_to_signal(si->node, config.roam_trigger_snr);
 269
 270         switch (si->roam_state) {
 271         case ROAM_TRIGGER_SCAN:
 272                 if (current_time - si->roam_event < config.roam_scan_interval)
 273                         break;
 274
 275                 if (find_better_candidate(si, &ev) ||
 276                     si->roam_scan_done > si->roam_event) {
 277                         usteer_roam_set_state(si, ROAM_TRIGGER_SCAN_DONE, &ev);
 278                         break;
 279                 }
 280
 281                 if (config.roam_scan_tries &&
 282                     si->roam_tries >= config.roam_scan_tries) {
 283                         usteer_roam_set_state(si, ROAM_TRIGGER_WAIT_KICK, &ev);
 284                         break;
 285                 }
 286
 287                 usteer_ubus_trigger_client_scan(si);
 288                 usteer_roam_set_state(si, ROAM_TRIGGER_SCAN, &ev);
 289                 break;
 290
 291         case ROAM_TRIGGER_IDLE:
 292                 if (find_better_candidate(si, &ev)) {
 293                         usteer_roam_set_state(si, ROAM_TRIGGER_SCAN_DONE, &ev);
 294                         break;
 295                 }
 296
 297                 usteer_roam_set_state(si, ROAM_TRIGGER_SCAN, &ev);
 298                 break;
 299
 300         case ROAM_TRIGGER_SCAN_DONE:
 301                 /* Check for stale scan results, kick back to SCAN state if necessary */
 302                 if (current_time - si->roam_scan_done > 2 * config.roam_scan_interval) {
 303                         usteer_roam_set_state(si, ROAM_TRIGGER_SCAN, &ev);
 304                         break;
 305                 }
 306
 307                 if (find_better_candidate(si, &ev))
 308                         usteer_roam_set_state(si, ROAM_TRIGGER_WAIT_KICK, &ev);
 309
 310                 break;
 311
 312         case ROAM_TRIGGER_WAIT_KICK:
 313                 if (si->signal > min_signal)
 314                         break;
 315
 316                 usteer_roam_set_state(si, ROAM_TRIGGER_NOTIFY_KICK, &ev);
 317                 usteer_ubus_notify_client_disassoc(si);
 318                 break;
 319         case ROAM_TRIGGER_NOTIFY_KICK:
 320                 if (current_time - si->roam_event < config.roam_kick_delay * 100)
 321                         break;
 322
 323                 usteer_roam_set_state(si, ROAM_TRIGGER_KICK, &ev);
 324                 break;
 325         case ROAM_TRIGGER_KICK:
 326                 usteer_ubus_kick_client(si);
 327                 usteer_roam_set_state(si, ROAM_TRIGGER_IDLE, &ev);
 328                 return true;
 329         }
 330
 331         return false;
 332 }
 333
 334 static void
 335 usteer_local_node_roam_check(struct usteer_local_node *ln, struct uevent *ev)
 336 {
 337         struct sta_info *si;
 338         int min_signal;
 339
 340         if (config.roam_scan_snr)
 341                 min_signal = config.roam_scan_snr;
 342         else if (config.roam_trigger_snr)
 343                 min_signal = config.roam_trigger_snr;
 344         else
 345                 return;
 346
 347         usteer_update_time();
 348         min_signal = snr_to_signal(&ln->node, min_signal);
 349
 350         list_for_each_entry(si, &ln->node.sta_info, node_list) {
 351                 if (si->connected != STA_CONNECTED || si->signal >= min_signal ||
 352                     current_time - si->roam_kick < config.roam_trigger_interval) {
 353                         usteer_roam_set_state(si, ROAM_TRIGGER_IDLE, ev);
 354                         continue;
 355                 }
 356
 357                 /*
 358                  * If the state machine kicked a client, other clients should wait
 359                  * until the next turn
 360                  */
 361                 if (usteer_roam_trigger_sm(si))
 362                         return;
 363         }
 364 }
 365
 366 static void
 367 usteer_local_node_snr_kick(struct usteer_local_node *ln)
 368 {
 369         struct uevent ev = {
 370                 .node_local = &ln->node,
 371         };
 372         struct sta_info *si;
 373         int min_signal;
 374
 375         if (!config.min_snr)
 376                 return;
 377
 378         min_signal = snr_to_signal(&ln->node, config.min_snr);
 379         ev.threshold.ref = min_signal;
 380
 381         list_for_each_entry(si, &ln->node.sta_info, node_list) {
 382                 if (si->connected != STA_CONNECTED)
 383                         continue;
 384
 385                 if (si->signal >= min_signal)
 386                         continue;
 387
 388                 si->kick_count++;
 389
 390                 ev.type = UEV_SIGNAL_KICK;
 391                 ev.threshold.cur = si->signal;
 392                 ev.count = si->kick_count;
 393                 usteer_event(&ev);
 394
 395                 usteer_ubus_kick_client(si);
 396                 return;
 397         }
 398 }
 399
 400 void
 401 usteer_local_node_kick(struct usteer_local_node *ln)
 402 {
 403         struct usteer_node *node = &ln->node;
 404         struct sta_info *kick1 = NULL, *kick2 = NULL;
 405         struct sta_info *candidate = NULL;
 406         struct sta_info *si;
 407         struct uevent ev = {
 408                 .node_local = &ln->node,
 409         };
 410         unsigned int min_count = DIV_ROUND_UP(config.load_kick_delay, config.local_sta_update);
 411
 412         usteer_local_node_roam_check(ln, &ev);
 413         usteer_local_node_snr_kick(ln);
 414
 415         if (!config.load_kick_enabled || !config.load_kick_threshold ||
 416             !config.load_kick_delay)
 417                 return;
 418
 419         if (node->load < config.load_kick_threshold) {
 420                 if (!ln->load_thr_count)
 421                         return;
 422
 423                 ln->load_thr_count = 0;
 424                 ev.type = UEV_LOAD_KICK_RESET;
 425                 ev.threshold.cur = node->load;
 426                 ev.threshold.ref = config.load_kick_threshold;
 427                 goto out;
 428         }
 429
 430         if (++ln->load_thr_count <= min_count) {
 431                 if (ln->load_thr_count > 1)
 432                         return;
 433
 434                 ev.type = UEV_LOAD_KICK_TRIGGER;
 435                 ev.threshold.cur = node->load;
 436                 ev.threshold.ref = config.load_kick_threshold;
 437                 goto out;
 438         }
 439
 440         ln->load_thr_count = 0;
 441         if (node->n_assoc < config.load_kick_min_clients) {
 442                 ev.type = UEV_LOAD_KICK_MIN_CLIENTS;
 443                 ev.threshold.cur = node->n_assoc;
 444                 ev.threshold.ref = config.load_kick_min_clients;
 445                 goto out;
 446         }
 447
 448         list_for_each_entry(si, &ln->node.sta_info, node_list) {
 449                 struct sta_info *tmp;
 450
 451                 if (si->connected != STA_CONNECTED)
 452                         continue;
 453
 454                 if (is_more_kickable(kick1, si))
 455                         kick1 = si;
 456
 457                 tmp = find_better_candidate(si, NULL);
 458                 if (!tmp)
 459                         continue;
 460
 461                 if (is_more_kickable(kick2, si)) {
 462                         kick2 = si;
 463                         candidate = tmp;
 464                 }
 465         }
 466
 467         if (!kick1) {
 468                 ev.type = UEV_LOAD_KICK_NO_CLIENT;
 469                 goto out;
 470         }
 471
 472         if (kick2)
 473                 kick1 = kick2;
 474
 475         kick1->kick_count++;
 476
 477         ev.type = UEV_LOAD_KICK_CLIENT;
 478         ev.si_cur = kick1;
 479         ev.si_other = candidate;
 480         ev.count = kick1->kick_count;
 481
 482         usteer_ubus_kick_client(kick1);
 483
 484 out:
 485         usteer_event(&ev);
 486 }