lib/service.c

   1 /*
   2  * libwebsockets - small server side websockets and web server implementation
   3  *
   4  * Copyright (C) 2010-2015 Andy Green <andy@warmcat.com>
   5  *
   6  *  This library is free software; you can redistribute it and/or
   7  *  modify it under the terms of the GNU Lesser General Public
   8  *  License as published by the Free Software Foundation:
   9  *  version 2.1 of the License.
  10  *
  11  *  This library is distributed in the hope that it will be useful,
  12  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  *  Lesser General Public License for more details.
  15  *
  16  *  You should have received a copy of the GNU Lesser General Public
  17  *  License along with this library; if not, write to the Free Software
  18  *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
  19  *  MA  02110-1301  USA
  20  */
  21
  22 #include "private-libwebsockets.h"
  23
  24 static int
  25 lws_calllback_as_writeable(struct lws *wsi)
  26 {
  27         int n;
  28
  29         switch (wsi->mode) {
  30         case LWSCM_WS_CLIENT:
  31                 n = LWS_CALLBACK_CLIENT_WRITEABLE;
  32                 break;
  33         case LWSCM_WS_SERVING:
  34                 n = LWS_CALLBACK_SERVER_WRITEABLE;
  35                 break;
  36         default:
  37                 n = LWS_CALLBACK_HTTP_WRITEABLE;
  38                 break;
  39         }
  40         lwsl_debug("%s: %p (user=%p)\n", __func__, wsi, wsi->user_space);
  41         return user_callback_handle_rxflow(wsi->protocol->callback,
  42                                            wsi, (enum lws_callback_reasons) n,
  43                                            wsi->user_space, NULL, 0);
  44 }
  45
  46 int
  47 lws_handle_POLLOUT_event(struct lws *wsi, struct lws_pollfd *pollfd)
  48 {
  49         int write_type = LWS_WRITE_PONG;
  50         struct lws_tokens eff_buf;
  51 #ifdef LWS_USE_HTTP2
  52         struct lws *wsi2;
  53 #endif
  54         int ret, m, n;
  55
  56         /*
  57          * user callback is lowest priority to get these notifications
  58          * actually, since other pending things cannot be disordered
  59          */
  60
  61         /* Priority 1: pending truncated sends are incomplete ws fragments
  62          *             If anything else sent first the protocol would be
  63          *             corrupted.
  64          */
  65         if (wsi->trunc_len) {
  66                 if (lws_issue_raw(wsi, wsi->trunc_alloc + wsi->trunc_offset,
  67                                   wsi->trunc_len) < 0) {
  68                         lwsl_info("%s signalling to close\n", __func__);
  69                         return -1;
  70                 }
  71                 /* leave POLLOUT active either way */
  72                 return 0;
  73         } else
  74                 if (wsi->state == LWSS_FLUSHING_STORED_SEND_BEFORE_CLOSE)
  75                         return -1; /* retry closing now */
  76
  77
  78 #ifdef LWS_USE_HTTP2
  79         /* Priority 2: protocol packets
  80          */
  81         if (wsi->pps) {
  82                 lwsl_info("servicing pps %d\n", wsi->pps);
  83                 switch (wsi->pps) {
  84                 case LWS_PPS_HTTP2_MY_SETTINGS:
  85                 case LWS_PPS_HTTP2_ACK_SETTINGS:
  86                         lws_http2_do_pps_send(lws_get_context(wsi), wsi);
  87                         break;
  88                 default:
  89                         break;
  90                 }
  91                 wsi->pps = LWS_PPS_NONE;
  92                 lws_rx_flow_control(wsi, 1);
  93
  94                 return 0; /* leave POLLOUT active */
  95         }
  96 #endif
  97         /* Priority 3: pending control packets (pong or close)
  98          */
  99         if ((wsi->state == LWSS_ESTABLISHED &&
 100              wsi->u.ws.ping_pending_flag) ||
 101             (wsi->state == LWSS_RETURNED_CLOSE_ALREADY &&
 102              wsi->u.ws.payload_is_close)) {
 103
 104                 if (wsi->u.ws.payload_is_close)
 105                         write_type = LWS_WRITE_CLOSE;
 106
 107                 n = lws_write(wsi, &wsi->u.ws.ping_payload_buf[LWS_PRE],
 108                               wsi->u.ws.ping_payload_len, write_type);
 109                 if (n < 0)
 110                         return -1;
 111
 112                 /* well he is sent, mark him done */
 113                 wsi->u.ws.ping_pending_flag = 0;
 114                 if (wsi->u.ws.payload_is_close)
 115                         /* oh... a close frame was it... then we are done */
 116                         return -1;
 117
 118                 /* otherwise for PING, leave POLLOUT active either way */
 119                 return 0;
 120         }
 121
 122         /* Priority 4: if we are closing, not allowed to send more data frags
 123          *             which means user callback or tx ext flush banned now
 124          */
 125         if (wsi->state == LWSS_RETURNED_CLOSE_ALREADY)
 126                 goto user_service;
 127
 128         /* Priority 5: Tx path extension with more to send
 129          *
 130          *             These are handled as new fragments each time around
 131          *             So while we must block new writeable callback to enforce
 132          *             payload ordering, but since they are always complete
 133          *             fragments control packets can interleave OK.
 134          */
 135         if (wsi->state == LWSS_ESTABLISHED && wsi->u.ws.tx_draining_ext) {
 136                 lwsl_ext("SERVICING TX EXT DRAINING\n");
 137                 if (lws_write(wsi, NULL, 0, LWS_WRITE_CONTINUATION) < 0)
 138                         return -1;
 139                 /* leave POLLOUT active */
 140                 return 0;
 141         }
 142
 143         /* Priority 6: user can get the callback
 144          */
 145         m = lws_ext_cb_active(wsi, LWS_EXT_CB_IS_WRITEABLE, NULL, 0);
 146         if (m)
 147                 return -1;
 148 #ifndef LWS_NO_EXTENSIONS
 149         if (!wsi->extension_data_pending)
 150                 goto user_service;
 151 #endif
 152         /*
 153          * check in on the active extensions, see if they
 154          * had pending stuff to spill... they need to get the
 155          * first look-in otherwise sequence will be disordered
 156          *
 157          * NULL, zero-length eff_buf means just spill pending
 158          */
 159
 160         ret = 1;
 161         while (ret == 1) {
 162
 163                 /* default to nobody has more to spill */
 164
 165                 ret = 0;
 166                 eff_buf.token = NULL;
 167                 eff_buf.token_len = 0;
 168
 169                 /* give every extension a chance to spill */
 170
 171                 m = lws_ext_cb_active(wsi,
 172                                         LWS_EXT_CB_PACKET_TX_PRESEND,
 173                                                &eff_buf, 0);
 174                 if (m < 0) {
 175                         lwsl_err("ext reports fatal error\n");
 176                         return -1;
 177                 }
 178                 if (m)
 179                         /*
 180                          * at least one extension told us he has more
 181                          * to spill, so we will go around again after
 182                          */
 183                         ret = 1;
 184
 185                 /* assuming they gave us something to send, send it */
 186
 187                 if (eff_buf.token_len) {
 188                         n = lws_issue_raw(wsi, (unsigned char *)eff_buf.token,
 189                                           eff_buf.token_len);
 190                         if (n < 0) {
 191                                 lwsl_info("closing from POLLOUT spill\n");
 192                                 return -1;
 193                         }
 194                         /*
 195                          * Keep amount spilled small to minimize chance of this
 196                          */
 197                         if (n != eff_buf.token_len) {
 198                                 lwsl_err("Unable to spill ext %d vs %s\n",
 199                                                           eff_buf.token_len, n);
 200                                 return -1;
 201                         }
 202                 } else
 203                         continue;
 204
 205                 /* no extension has more to spill */
 206
 207                 if (!ret)
 208                         continue;
 209
 210                 /*
 211                  * There's more to spill from an extension, but we just sent
 212                  * something... did that leave the pipe choked?
 213                  */
 214
 215                 if (!lws_send_pipe_choked(wsi))
 216                         /* no we could add more */
 217                         continue;
 218
 219                 lwsl_info("choked in POLLOUT service\n");
 220
 221                 /*
 222                  * Yes, he's choked.  Leave the POLLOUT masked on so we will
 223                  * come back here when he is unchoked.  Don't call the user
 224                  * callback to enforce ordering of spilling, he'll get called
 225                  * when we come back here and there's nothing more to spill.
 226                  */
 227
 228                 return 0;
 229         }
 230 #ifndef LWS_NO_EXTENSIONS
 231         wsi->extension_data_pending = 0;
 232 #endif
 233 user_service:
 234         /* one shot */
 235
 236         if (pollfd)
 237                 if (lws_change_pollfd(wsi, LWS_POLLOUT, 0)) {
 238                         lwsl_info("failed at set pollfd\n");
 239                         return 1;
 240                 }
 241
 242 #ifdef LWS_USE_HTTP2
 243         /*
 244          * we are the 'network wsi' for potentially many muxed child wsi with
 245          * no network connection of their own, who have to use us for all their
 246          * network actions.  So we use a round-robin scheme to share out the
 247          * POLLOUT notifications to our children.
 248          *
 249          * But because any child could exhaust the socket's ability to take
 250          * writes, we can only let one child get notified each time.
 251          *
 252          * In addition children may be closed / deleted / added between POLLOUT
 253          * notifications, so we can't hold pointers
 254          */
 255
 256         if (wsi->mode != LWSCM_HTTP2_SERVING) {
 257                 lwsl_info("%s: non http2\n", __func__);
 258                 goto notify;
 259         }
 260
 261         wsi->u.http2.requested_POLLOUT = 0;
 262         if (!wsi->u.http2.initialized) {
 263                 lwsl_info("pollout on uninitialized http2 conn\n");
 264                 return 0;
 265         }
 266
 267         lwsl_info("%s: doing children\n", __func__);
 268
 269         wsi2 = wsi;
 270         do {
 271                 wsi2 = wsi2->u.http2.next_child_wsi;
 272                 lwsl_info("%s: child %p\n", __func__, wsi2);
 273                 if (!wsi2)
 274                         continue;
 275                 if (!wsi2->u.http2.requested_POLLOUT)
 276                         continue;
 277                 wsi2->u.http2.requested_POLLOUT = 0;
 278                 if (lws_calllback_as_writeable(wsi2)) {
 279                         lwsl_debug("Closing POLLOUT child\n");
 280                         lws_close_free_wsi(wsi2, LWS_CLOSE_STATUS_NOSTATUS);
 281                 }
 282                 wsi2 = wsi;
 283         } while (wsi2 != NULL && !lws_send_pipe_choked(wsi));
 284
 285         lwsl_info("%s: completed\n", __func__);
 286
 287         return 0;
 288 notify:
 289 #endif
 290         return lws_calllback_as_writeable(wsi);
 291 }
 292
 293 int
 294 lws_service_timeout_check(struct lws *wsi, unsigned int sec)
 295 {
 296         struct lws_context_per_thread *pt = &wsi->context->pt[(int)wsi->tsi];
 297
 298         /*
 299          * if extensions want in on it (eg, we are a mux parent)
 300          * give them a chance to service child timeouts
 301          */
 302         if (lws_ext_cb_active(wsi, LWS_EXT_CB_1HZ, NULL, sec) < 0)
 303                 return 0;
 304
 305         if (!wsi->pending_timeout)
 306                 return 0;
 307
 308         /*
 309          * if we went beyond the allowed time, kill the
 310          * connection
 311          */
 312         if ((time_t)sec > wsi->pending_timeout_limit) {
 313 #if LWS_POSIX
 314                 lwsl_notice("wsi %p: TIMEDOUT WAITING on %d (did hdr %d, ah %p, wl %d, pfd events %d)\n",
 315                             (void *)wsi, wsi->pending_timeout,
 316                             wsi->hdr_parsing_completed, wsi->u.hdr.ah,
 317                             pt->ah_wait_list_length,
 318                             pt->fds[wsi->sock].events);
 319 #endif
 320                 /*
 321                  * Since he failed a timeout, he already had a chance to do
 322                  * something and was unable to... that includes situations like
 323                  * half closed connections.  So process this "failed timeout"
 324                  * close as a violent death and don't try to do protocol
 325                  * cleanup like flush partials.
 326                  */
 327                 wsi->socket_is_permanently_unusable = 1;
 328                 if (wsi->mode == LWSCM_WSCL_WAITING_SSL)
 329                         wsi->context->protocols[0].callback(wsi,
 330                                         LWS_CALLBACK_CLIENT_CONNECTION_ERROR,
 331                                         wsi->user_space, NULL, 0);
 332                 lws_close_free_wsi(wsi, LWS_CLOSE_STATUS_NOSTATUS);
 333
 334                 return 1;
 335         }
 336
 337         return 0;
 338 }
 339
 340 int lws_rxflow_cache(struct lws *wsi, unsigned char *buf, int n, int len)
 341 {
 342         /* his RX is flowcontrolled, don't send remaining now */
 343         if (wsi->rxflow_buffer) {
 344                 /* rxflow while we were spilling prev rxflow */
 345                 lwsl_info("stalling in existing rxflow buf\n");
 346                 return 1;
 347         }
 348
 349         /* a new rxflow, buffer it and warn caller */
 350         lwsl_info("new rxflow input buffer len %d\n", len - n);
 351         wsi->rxflow_buffer = lws_malloc(len - n);
 352         wsi->rxflow_len = len - n;
 353         wsi->rxflow_pos = 0;
 354         memcpy(wsi->rxflow_buffer, buf + n, len - n);
 355
 356         return 0;
 357 }
 358
 359 /* this is used by the platform service code to stop us waiting for network
 360  * activity in poll() when we have something that already needs service
 361  */
 362
 363 int
 364 lws_service_adjust_timeout(struct lws_context *context, int timeout_ms, int tsi)
 365 {
 366         struct lws_context_per_thread *pt = &context->pt[tsi];
 367         int n;
 368
 369         /* Figure out if we really want to wait in poll()
 370          * We only need to wait if really nothing already to do and we have
 371          * to wait for something from network
 372          */
 373
 374         /* 1) if we know we are draining rx ext, do not wait in poll */
 375         if (pt->rx_draining_ext_list)
 376                 return 0;
 377
 378 #ifdef LWS_OPENSSL_SUPPORT
 379         /* 2) if we know we have non-network pending data, do not wait in poll */
 380         if (lws_ssl_anybody_has_buffered_read_tsi(context, tsi)) {
 381                 lwsl_info("ssl buffered read\n");
 382                 return 0;
 383         }
 384 #endif
 385
 386         /* 3) if any ah has pending rx, do not wait in poll */
 387         for (n = 0; n < context->max_http_header_pool; n++)
 388                 if (pt->ah_pool[n].rxpos != pt->ah_pool[n].rxlen) {
 389                         /* any ah with pending rx must be attached to someone */
 390                         assert(pt->ah_pool[n].wsi);
 391                         return 0;
 392                 }
 393
 394         return timeout_ms;
 395 }
 396
 397 /*
 398  * guys that need POLLIN service again without waiting for network action
 399  * can force POLLIN here if not flowcontrolled, so they will get service.
 400  *
 401  * Return nonzero if anybody got their POLLIN faked
 402  */
 403 int
 404 lws_service_flag_pending(struct lws_context *context, int tsi)
 405 {
 406         struct lws_context_per_thread *pt = &context->pt[tsi];
 407 #ifdef LWS_OPENSSL_SUPPORT
 408         struct lws *wsi_next;
 409 #endif
 410         struct lws *wsi;
 411         int forced = 0;
 412         int n;
 413
 414         /* POLLIN faking */
 415
 416         /*
 417          * 1) For all guys with already-available ext data to drain, if they are
 418          * not flowcontrolled, fake their POLLIN status
 419          */
 420         wsi = pt->rx_draining_ext_list;
 421         while (wsi) {
 422                 pt->fds[wsi->position_in_fds_table].revents |=
 423                         pt->fds[wsi->position_in_fds_table].events & LWS_POLLIN;
 424                 if (pt->fds[wsi->position_in_fds_table].revents &
 425                     LWS_POLLIN)
 426                         forced = 1;
 427                 wsi = wsi->u.ws.rx_draining_ext_list;
 428         }
 429
 430 #ifdef LWS_OPENSSL_SUPPORT
 431         /*
 432          * 2) For all guys with buffered SSL read data already saved up, if they
 433          * are not flowcontrolled, fake their POLLIN status so they'll get
 434          * service to use up the buffered incoming data, even though their
 435          * network socket may have nothing
 436          */
 437         wsi = pt->pending_read_list;
 438         while (wsi) {
 439                 wsi_next = wsi->pending_read_list_next;
 440                 pt->fds[wsi->position_in_fds_table].revents |=
 441                         pt->fds[wsi->position_in_fds_table].events & LWS_POLLIN;
 442                 if (pt->fds[wsi->position_in_fds_table].revents & LWS_POLLIN) {
 443                         forced = 1;
 444                         /*
 445                          * he's going to get serviced now, take him off the
 446                          * list of guys with buffered SSL.  If he still has some
 447                          * at the end of the service, he'll get put back on the
 448                          * list then.
 449                          */
 450                         lws_ssl_remove_wsi_from_buffered_list(wsi);
 451                 }
 452
 453                 wsi = wsi_next;
 454         }
 455 #endif
 456         /*
 457          * 3) For any wsi who have an ah with pending RX who did not
 458          * complete their current headers, and are not flowcontrolled,
 459          * fake their POLLIN status so they will be able to drain the
 460          * rx buffered in the ah
 461          */
 462         for (n = 0; n < context->max_http_header_pool; n++)
 463                 if (pt->ah_pool[n].rxpos != pt->ah_pool[n].rxlen &&
 464                     !pt->ah_pool[n].wsi->hdr_parsing_completed) {
 465                         pt->fds[pt->ah_pool[n].wsi->position_in_fds_table].revents |=
 466                                 pt->fds[pt->ah_pool[n].wsi->position_in_fds_table].events &
 467                                         LWS_POLLIN;
 468                         if (pt->fds[pt->ah_pool[n].wsi->position_in_fds_table].revents &
 469                             LWS_POLLIN)
 470                                 forced = 1;
 471                 }
 472
 473         return forced;
 474 }
 475
 476 /**
 477  * lws_service_fd() - Service polled socket with something waiting
 478  * @context:    Websocket context
 479  * @pollfd:     The pollfd entry describing the socket fd and which events
 480  *              happened.
 481  *
 482  *      This function takes a pollfd that has POLLIN or POLLOUT activity and
 483  *      services it according to the state of the associated
 484  *      struct lws.
 485  *
 486  *      The one call deals with all "service" that might happen on a socket
 487  *      including listen accepts, http files as well as websocket protocol.
 488  *
 489  *      If a pollfd says it has something, you can just pass it to
 490  *      lws_service_fd() whether it is a socket handled by lws or not.
 491  *      If it sees it is a lws socket, the traffic will be handled and
 492  *      pollfd->revents will be zeroed now.
 493  *
 494  *      If the socket is foreign to lws, it leaves revents alone.  So you can
 495  *      see if you should service yourself by checking the pollfd revents
 496  *      after letting lws try to service it.
 497  */
 498
 499 LWS_VISIBLE int
 500 lws_service_fd_tsi(struct lws_context *context, struct lws_pollfd *pollfd, int tsi)
 501 {
 502         struct lws_context_per_thread *pt = &context->pt[tsi];
 503         lws_sockfd_type our_fd = 0, tmp_fd;
 504         struct lws_tokens eff_buf;
 505         unsigned int pending = 0;
 506         struct lws *wsi, *wsi1;
 507         char draining_flow = 0;
 508         int timed_out = 0;
 509         time_t now;
 510         int n, m;
 511         int more;
 512
 513         /*
 514          * you can call us with pollfd = NULL to just allow the once-per-second
 515          * global timeout checks; if less than a second since the last check
 516          * it returns immediately then.
 517          */
 518
 519         time(&now);
 520
 521         /* TODO: if using libev, we should probably use timeout watchers... */
 522         if (context->last_timeout_check_s != now) {
 523                 context->last_timeout_check_s = now;
 524
 525                 lws_plat_service_periodic(context);
 526
 527                 /* global timeout check once per second */
 528
 529                 if (pollfd)
 530                         our_fd = pollfd->fd;
 531
 532                 wsi = context->pt[tsi].timeout_list;
 533                 while (wsi) {
 534                         /* we have to take copies, because he may be deleted */
 535                         wsi1 = wsi->timeout_list;
 536                         tmp_fd = wsi->sock;
 537                         if (lws_service_timeout_check(wsi, (unsigned int)now)) {
 538                                 /* he did time out... */
 539                                 if (tmp_fd == our_fd)
 540                                         /* it was the guy we came to service! */
 541                                         timed_out = 1;
 542                                         /* he's gone, no need to mark as handled */
 543                         }
 544                         wsi = wsi1;
 545                 }
 546 #if 0
 547                 {
 548                         char s[300], *p = s;
 549
 550                         for (n = 0; n < context->count_threads; n++)
 551                                 p += sprintf(p, " %7lu (%5d), ",
 552                                              context->pt[n].count_conns,
 553                                              context->pt[n].fds_count);
 554
 555                         lwsl_notice("load: %s\n", s);
 556                 }
 557 #endif
 558         }
 559
 560         /* the socket we came to service timed out, nothing to do */
 561         if (timed_out)
 562                 return 0;
 563
 564         /* just here for timeout management? */
 565         if (!pollfd)
 566                 return 0;
 567
 568         /* no, here to service a socket descriptor */
 569         wsi = wsi_from_fd(context, pollfd->fd);
 570         if (!wsi)
 571                 /* not lws connection ... leave revents alone and return */
 572                 return 0;
 573
 574         /*
 575          * so that caller can tell we handled, past here we need to
 576          * zero down pollfd->revents after handling
 577          */
 578
 579 #if LWS_POSIX
 580
 581         /* handle session socket closed */
 582
 583         if ((!(pollfd->revents & pollfd->events & LWS_POLLIN)) &&
 584             (pollfd->revents & LWS_POLLHUP)) {
 585                 wsi->socket_is_permanently_unusable = 1;
 586                 lwsl_debug("Session Socket %p (fd=%d) dead\n",
 587                                                        (void *)wsi, pollfd->fd);
 588
 589                 goto close_and_handled;
 590         }
 591
 592 #ifdef _WIN32
 593         if (pollfd->revents & LWS_POLLOUT)
 594                 wsi->sock_send_blocking = FALSE;
 595 #endif
 596
 597 #endif
 598
 599         /* okay, what we came here to do... */
 600
 601         switch (wsi->mode) {
 602         case LWSCM_HTTP_SERVING:
 603         case LWSCM_HTTP_SERVING_ACCEPTED:
 604         case LWSCM_SERVER_LISTENER:
 605         case LWSCM_SSL_ACK_PENDING:
 606                 n = lws_server_socket_service(context, wsi, pollfd);
 607                 if (n) /* closed by above */
 608                         return 1;
 609                 goto handled;
 610
 611         case LWSCM_WS_SERVING:
 612         case LWSCM_WS_CLIENT:
 613         case LWSCM_HTTP2_SERVING:
 614
 615                 /* 1: something requested a callback when it was OK to write */
 616
 617                 if ((pollfd->revents & LWS_POLLOUT) &&
 618                     (wsi->state == LWSS_ESTABLISHED ||
 619                      wsi->state == LWSS_HTTP2_ESTABLISHED ||
 620                      wsi->state == LWSS_HTTP2_ESTABLISHED_PRE_SETTINGS ||
 621                      wsi->state == LWSS_RETURNED_CLOSE_ALREADY ||
 622                      wsi->state == LWSS_FLUSHING_STORED_SEND_BEFORE_CLOSE) &&
 623                     lws_handle_POLLOUT_event(wsi, pollfd)) {
 624                         if (wsi->state == LWSS_RETURNED_CLOSE_ALREADY)
 625                                 wsi->state = LWSS_FLUSHING_STORED_SEND_BEFORE_CLOSE;
 626                         lwsl_info("lws_service_fd: closing\n");
 627                         goto close_and_handled;
 628                 }
 629
 630                 if (wsi->state == LWSS_RETURNED_CLOSE_ALREADY ||
 631                     wsi->state == LWSS_AWAITING_CLOSE_ACK) {
 632                         /*
 633                          * we stopped caring about anything except control
 634                          * packets.  Force flow control off, defeat tx
 635                          * draining.
 636                          */
 637                         lws_rx_flow_control(wsi, 1);
 638                         wsi->u.ws.tx_draining_ext = 0;
 639                 }
 640
 641                 if (wsi->u.ws.tx_draining_ext) {
 642                         /* we cannot deal with new RX until the TX ext
 643                          * path has been drained.  It's because new
 644                          * rx will, eg, crap on the wsi rx buf that
 645                          * may be needed to retain state.
 646                          *
 647                          * TX ext drain path MUST go through event loop
 648                          * to avoid blocking.
 649                          */
 650                         break;
 651                 }
 652
 653                 if (!(wsi->rxflow_change_to & LWS_RXFLOW_ALLOW))
 654                         /* We cannot deal with any kind of new RX
 655                          * because we are RX-flowcontrolled.
 656                          */
 657                         break;
 658
 659                 /* 2: RX Extension needs to be drained
 660                  */
 661
 662                 if (wsi->state == LWSS_ESTABLISHED &&
 663                     wsi->u.ws.rx_draining_ext) {
 664
 665                         lwsl_ext("%s: RX EXT DRAINING: Service\n", __func__);
 666 #ifndef LWS_NO_CLIENT
 667                         if (wsi->mode == LWSCM_WS_CLIENT) {
 668                                 n = lws_client_rx_sm(wsi, 0);
 669                                 if (n < 0)
 670                                         /* we closed wsi */
 671                                         n = 0;
 672                         } else
 673 #endif
 674                                 n = lws_rx_sm(wsi, 0);
 675
 676                         goto handled;
 677                 }
 678
 679                 if (wsi->u.ws.rx_draining_ext)
 680                         /*
 681                          * We have RX EXT content to drain, but can't do it
 682                          * right now.  That means we cannot do anything lower
 683                          * priority either.
 684                          */
 685                         break;
 686
 687                 /* 3: RX Flowcontrol buffer needs to be drained
 688                  */
 689
 690                 if (wsi->rxflow_buffer) {
 691                         lwsl_info("draining rxflow (len %d)\n",
 692                                 wsi->rxflow_len - wsi->rxflow_pos
 693                         );
 694                         /* well, drain it */
 695                         eff_buf.token = (char *)wsi->rxflow_buffer +
 696                                                 wsi->rxflow_pos;
 697                         eff_buf.token_len = wsi->rxflow_len - wsi->rxflow_pos;
 698                         draining_flow = 1;
 699                         goto drain;
 700                 }
 701
 702                 /* 4: any incoming (or ah-stashed incoming rx) data ready?
 703                  * notice if rx flow going off raced poll(), rx flow wins
 704                  */
 705
 706                 if (!(pollfd->revents & pollfd->events & LWS_POLLIN))
 707                         break;
 708 read:
 709
 710                 /* all the union members start with hdr, so even in ws mode
 711                  * we can deal with the ah via u.hdr
 712                  */
 713                 if (wsi->u.hdr.ah) {
 714                         lwsl_err("%s: %p: using inherited ah rx\n", __func__, wsi);
 715                         eff_buf.token_len = wsi->u.hdr.ah->rxlen -
 716                                             wsi->u.hdr.ah->rxpos;
 717                         eff_buf.token = (char *)wsi->u.hdr.ah->rx +
 718                                         wsi->u.hdr.ah->rxpos;
 719                 } else {
 720
 721                         eff_buf.token_len = lws_ssl_capable_read(wsi, pt->serv_buf,
 722                                              pending ? pending : LWS_MAX_SOCKET_IO_BUF);
 723                         switch (eff_buf.token_len) {
 724                         case 0:
 725                                 lwsl_info("service_fd: closing due to 0 length read\n");
 726                                 goto close_and_handled;
 727                         case LWS_SSL_CAPABLE_MORE_SERVICE:
 728                                 lwsl_info("SSL Capable more service\n");
 729                                 n = 0;
 730                                 goto handled;
 731                         case LWS_SSL_CAPABLE_ERROR:
 732                                 lwsl_info("Closing when error\n");
 733                                 goto close_and_handled;
 734                         }
 735
 736                         eff_buf.token = (char *)pt->serv_buf;
 737                 }
 738                 /*
 739                  * give any active extensions a chance to munge the buffer
 740                  * before parse.  We pass in a pointer to an lws_tokens struct
 741                  * prepared with the default buffer and content length that's in
 742                  * there.  Rather than rewrite the default buffer, extensions
 743                  * that expect to grow the buffer can adapt .token to
 744                  * point to their own per-connection buffer in the extension
 745                  * user allocation.  By default with no extensions or no
 746                  * extension callback handling, just the normal input buffer is
 747                  * used then so it is efficient.
 748                  */
 749 drain:
 750                 do {
 751                         more = 0;
 752
 753                         m = lws_ext_cb_active(wsi, LWS_EXT_CB_PACKET_RX_PREPARSE,
 754                                               &eff_buf, 0);
 755                         if (m < 0)
 756                                 goto close_and_handled;
 757                         if (m)
 758                                 more = 1;
 759
 760                         /* service incoming data */
 761
 762                         if (eff_buf.token_len) {
 763                                 /*
 764                                  * if draining from rxflow buffer, not
 765                                  * critical to track what was used since at the
 766                                  * use it bumps wsi->rxflow_pos.  If we come
 767                                  * around again it will pick up from where it
 768                                  * left off.
 769                                  */
 770                                 n = lws_read(wsi, (unsigned char *)eff_buf.token,
 771                                              eff_buf.token_len);
 772                                 if (n < 0) {
 773                                         /* we closed wsi */
 774                                         n = 0;
 775                                         goto handled;
 776                                 }
 777                         }
 778
 779                         eff_buf.token = NULL;
 780                         eff_buf.token_len = 0;
 781                 } while (more);
 782
 783                 if (wsi->u.hdr.ah) {
 784                         lwsl_err("%s: %p: detaching inherited used ah\n", __func__, wsi);
 785                         /* show we used all the pending rx up */
 786                         wsi->u.hdr.ah->rxpos = wsi->u.hdr.ah->rxlen;
 787                         /* we can run the normal ah detach flow despite
 788                          * being in ws union mode, since all union members
 789                          * start with hdr */
 790                         lws_header_table_detach(wsi);
 791                 }
 792
 793                 pending = lws_ssl_pending(wsi);
 794                 if (pending) {
 795                         pending = pending > LWS_MAX_SOCKET_IO_BUF ?
 796                                         LWS_MAX_SOCKET_IO_BUF : pending;
 797                         goto read;
 798                 }
 799
 800                 if (draining_flow && wsi->rxflow_buffer &&
 801                     wsi->rxflow_pos == wsi->rxflow_len) {
 802                         lwsl_info("flow buffer: drained\n");
 803                         lws_free_set_NULL(wsi->rxflow_buffer);
 804                         /* having drained the rxflow buffer, can rearm POLLIN */
 805 #ifdef LWS_NO_SERVER
 806                         n =
 807 #endif
 808                         _lws_rx_flow_control(wsi);
 809                         /* n ignored, needed for NO_SERVER case */
 810                 }
 811
 812                 break;
 813
 814         default:
 815 #ifdef LWS_NO_CLIENT
 816                 break;
 817 #else
 818                 n = lws_client_socket_service(context, wsi, pollfd);
 819                 if (n)
 820                         return 1;
 821                 goto handled;
 822 #endif
 823         }
 824
 825         n = 0;
 826         goto handled;
 827
 828 close_and_handled:
 829         lwsl_debug("Close and handled\n");
 830         lws_close_free_wsi(wsi, LWS_CLOSE_STATUS_NOSTATUS);
 831         /*
 832          * pollfd may point to something else after the close
 833          * due to pollfd swapping scheme on delete on some platforms
 834          * we can't clear revents now because it'd be the wrong guy's revents
 835          */
 836         return 1;
 837
 838 handled:
 839         pollfd->revents = 0;
 840         return n;
 841 }
 842
 843 LWS_VISIBLE int
 844 lws_service_fd(struct lws_context *context, struct lws_pollfd *pollfd)
 845 {
 846         return lws_service_fd_tsi(context, pollfd, 0);
 847 }
 848
 849 /**
 850  * lws_service() - Service any pending websocket activity
 851  * @context:    Websocket context
 852  * @timeout_ms: Timeout for poll; 0 means return immediately if nothing needed
 853  *              service otherwise block and service immediately, returning
 854  *              after the timeout if nothing needed service.
 855  *
 856  *      This function deals with any pending websocket traffic, for three
 857  *      kinds of event.  It handles these events on both server and client
 858  *      types of connection the same.
 859  *
 860  *      1) Accept new connections to our context's server
 861  *
 862  *      2) Call the receive callback for incoming frame data received by
 863  *          server or client connections.
 864  *
 865  *      You need to call this service function periodically to all the above
 866  *      functions to happen; if your application is single-threaded you can
 867  *      just call it in your main event loop.
 868  *
 869  *      Alternatively you can fork a new process that asynchronously handles
 870  *      calling this service in a loop.  In that case you are happy if this
 871  *      call blocks your thread until it needs to take care of something and
 872  *      would call it with a large nonzero timeout.  Your loop then takes no
 873  *      CPU while there is nothing happening.
 874  *
 875  *      If you are calling it in a single-threaded app, you don't want it to
 876  *      wait around blocking other things in your loop from happening, so you
 877  *      would call it with a timeout_ms of 0, so it returns immediately if
 878  *      nothing is pending, or as soon as it services whatever was pending.
 879  */
 880
 881 LWS_VISIBLE int
 882 lws_service(struct lws_context *context, int timeout_ms)
 883 {
 884         return lws_plat_service(context, timeout_ms);
 885 }
 886
 887 LWS_VISIBLE int
 888 lws_service_tsi(struct lws_context *context, int timeout_ms, int tsi)
 889 {
 890         return lws_plat_service_tsi(context, timeout_ms, tsi);
 891 }
 892