lib/pollfd.c

   1 /*
   2  * libwebsockets - small server side websockets and web server implementation
   3  *
   4  * Copyright (C) 2010-2014 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 int
  25 insert_wsi_socket_into_fds(struct libwebsocket_context *context,
  26                                                        struct libwebsocket *wsi)
  27 {
  28         struct libwebsocket_pollargs pa = { wsi->sock, LWS_POLLIN, 0 };
  29
  30         if (context->fds_count >= context->max_fds) {
  31                 lwsl_err("Too many fds (%d)\n", context->max_fds);
  32                 return 1;
  33         }
  34
  35         if (wsi->sock >= context->max_fds) {
  36                 lwsl_err("Socket fd %d is too high (%d)\n",
  37                                                 wsi->sock, context->max_fds);
  38                 return 1;
  39         }
  40
  41         assert(wsi);
  42         assert(wsi->sock >= 0);
  43
  44         lwsl_info("insert_wsi_socket_into_fds: wsi=%p, sock=%d, fds pos=%d\n",
  45                                             wsi, wsi->sock, context->fds_count);
  46
  47         context->protocols[0].callback(context, wsi,
  48                 LWS_CALLBACK_LOCK_POLL,
  49                 wsi->user_space, (void *) &pa, 0);
  50
  51         context->lws_lookup[wsi->sock] = wsi;
  52         wsi->position_in_fds_table = context->fds_count;
  53         context->fds[context->fds_count].fd = wsi->sock;
  54         context->fds[context->fds_count].events = LWS_POLLIN;
  55
  56         lws_plat_insert_socket_into_fds(context, wsi);
  57
  58         /* external POLL support via protocol 0 */
  59         context->protocols[0].callback(context, wsi,
  60                 LWS_CALLBACK_ADD_POLL_FD,
  61                 wsi->user_space, (void *) &pa, 0);
  62
  63         context->protocols[0].callback(context, wsi,
  64                 LWS_CALLBACK_UNLOCK_POLL,
  65                 wsi->user_space, (void *)&pa, 0);
  66
  67         return 0;
  68 }
  69
  70 int
  71 remove_wsi_socket_from_fds(struct libwebsocket_context *context,
  72                                                       struct libwebsocket *wsi)
  73 {
  74         int m;
  75         struct libwebsocket_pollargs pa = { wsi->sock, 0, 0 };
  76
  77         lws_libev_io(context, wsi, LWS_EV_STOP | LWS_EV_READ | LWS_EV_WRITE);
  78
  79         if (!--context->fds_count) {
  80                 context->protocols[0].callback(context, wsi,
  81                         LWS_CALLBACK_LOCK_POLL,
  82                         wsi->user_space, (void *) &pa, 0);
  83                 goto do_ext;
  84         }
  85
  86         if (wsi->sock > context->max_fds) {
  87                 lwsl_err("Socket fd %d too high (%d)\n",
  88                                                    wsi->sock, context->max_fds);
  89                 return 1;
  90         }
  91
  92         lwsl_info("%s: wsi=%p, sock=%d, fds pos=%d\n", __func__,
  93                                     wsi, wsi->sock, wsi->position_in_fds_table);
  94
  95         context->protocols[0].callback(context, wsi,
  96                 LWS_CALLBACK_LOCK_POLL,
  97                 wsi->user_space, (void *)&pa, 0);
  98
  99         m = wsi->position_in_fds_table; /* replace the contents for this */
 100
 101         /* have the last guy take up the vacant slot */
 102         context->fds[m] = context->fds[context->fds_count];
 103
 104         lws_plat_delete_socket_from_fds(context, wsi, m);
 105
 106         /*
 107          * end guy's fds_lookup entry remains unchanged
 108          * (still same fd pointing to same wsi)
 109          */
 110         /* end guy's "position in fds table" changed */
 111         context->lws_lookup[context->fds[context->fds_count].fd]->
 112                                                 position_in_fds_table = m;
 113         /* deletion guy's lws_lookup entry needs nuking */
 114         context->lws_lookup[wsi->sock] = NULL;
 115         /* removed wsi has no position any more */
 116         wsi->position_in_fds_table = -1;
 117
 118 do_ext:
 119         /* remove also from external POLL support via protocol 0 */
 120         if (wsi->sock) {
 121                 context->protocols[0].callback(context, wsi,
 122                     LWS_CALLBACK_DEL_POLL_FD, wsi->user_space,
 123                     (void *) &pa, 0);
 124         }
 125         context->protocols[0].callback(context, wsi,
 126                                        LWS_CALLBACK_UNLOCK_POLL,
 127                                        wsi->user_space, (void *) &pa, 0);
 128         return 0;
 129 }
 130
 131 int
 132 lws_change_pollfd(struct libwebsocket *wsi, int _and, int _or)
 133 {
 134         struct libwebsocket_context *context = wsi->protocol->owning_server;
 135         int tid;
 136         int sampled_tid;
 137         struct libwebsocket_pollfd *pfd;
 138         struct libwebsocket_pollargs pa;
 139
 140         pfd = &context->fds[wsi->position_in_fds_table];
 141         pa.fd = wsi->sock;
 142
 143         context->protocols[0].callback(context, wsi,
 144                 LWS_CALLBACK_LOCK_POLL, wsi->user_space,  (void *) &pa, 0);
 145
 146         pa.prev_events = pfd->events;
 147         pa.events = pfd->events = (pfd->events & ~_and) | _or;
 148
 149         context->protocols[0].callback(context, wsi,
 150                         LWS_CALLBACK_CHANGE_MODE_POLL_FD,
 151                                 wsi->user_space, (void *) &pa, 0);
 152
 153         /*
 154          * if we changed something in this pollfd...
 155          *   ... and we're running in a different thread context
 156          *     than the service thread...
 157          *       ... and the service thread is waiting ...
 158          *         then cancel it to force a restart with our changed events
 159          */
 160         if (pa.prev_events != pa.events) {
 161
 162                 if (lws_plat_change_pollfd(context, wsi, pfd)) {
 163                         lwsl_info("%s failed\n", __func__);
 164                         return 1;
 165                 }
 166
 167                 sampled_tid = context->service_tid;
 168                 if (sampled_tid) {
 169                         tid = context->protocols[0].callback(context, NULL,
 170                                      LWS_CALLBACK_GET_THREAD_ID, NULL, NULL, 0);
 171                         if (tid != sampled_tid)
 172                                 libwebsocket_cancel_service(context);
 173                 }
 174         }
 175
 176         context->protocols[0].callback(context, wsi,
 177                 LWS_CALLBACK_UNLOCK_POLL, wsi->user_space, (void *) &pa, 0);
 178
 179         return 0;
 180 }
 181
 182
 183 /**
 184  * libwebsocket_callback_on_writable() - Request a callback when this socket
 185  *                                       becomes able to be written to without
 186  *                                       blocking
 187  *
 188  * @context:    libwebsockets context
 189  * @wsi:        Websocket connection instance to get callback for
 190  */
 191
 192 LWS_VISIBLE int
 193 libwebsocket_callback_on_writable(struct libwebsocket_context *context,
 194                                                       struct libwebsocket *wsi)
 195 {
 196 #ifdef LWS_USE_HTTP2
 197         struct libwebsocket *network_wsi, *wsi2;
 198         int already;
 199
 200         lwsl_info("%s: %p\n", __func__, wsi);
 201
 202         if (wsi->mode != LWS_CONNMODE_HTTP2_SERVING)
 203                 goto network_sock;
 204
 205         if (wsi->u.http2.requested_POLLOUT) {
 206                 lwsl_info("already pending writable\n");
 207                 return 1;
 208         }
 209
 210         if (wsi->u.http2.tx_credit <= 0) {
 211                 /*
 212                  * other side is not able to cope with us sending
 213                  * anything so no matter if we have POLLOUT on our side.
 214                  *
 215                  * Delay waiting for our POLLOUT until peer indicates he has
 216                  * space for more using tx window command in http2 layer
 217                  */
 218                 lwsl_info("%s: %p: waiting_tx_credit (%d)\n", __func__, wsi, wsi->u.http2.tx_credit);
 219                 wsi->u.http2.waiting_tx_credit = 1;
 220                 return 0;
 221         }
 222
 223         network_wsi = lws_http2_get_network_wsi(wsi);
 224         already = network_wsi->u.http2.requested_POLLOUT;
 225
 226         /* mark everybody above him as requesting pollout */
 227
 228         wsi2 = wsi;
 229         while (wsi2) {
 230                 wsi2->u.http2.requested_POLLOUT = 1;
 231                 lwsl_info("mark %p pending writable\n", wsi2);
 232                 wsi2 = wsi2->u.http2.parent_wsi;
 233         }
 234
 235         /* for network action, act only on the network wsi */
 236
 237         wsi = network_wsi;
 238         if (already)
 239                 return 1;
 240 network_sock:
 241 #endif
 242
 243         if (lws_ext_callback_for_each_active(wsi,
 244                                 LWS_EXT_CALLBACK_REQUEST_ON_WRITEABLE, NULL, 0))
 245                 return 1;
 246
 247         if (wsi->position_in_fds_table < 0) {
 248                 lwsl_err("%s: failed to find socket %d\n", __func__, wsi->sock);
 249                 return -1;
 250         }
 251
 252         if (lws_change_pollfd(wsi, 0, LWS_POLLOUT))
 253                 return -1;
 254
 255         lws_libev_io(context, wsi, LWS_EV_START | LWS_EV_WRITE);
 256
 257         return 1;
 258 }
 259
 260 /**
 261  * libwebsocket_callback_on_writable_all_protocol() - Request a callback for
 262  *                      all connections using the given protocol when it
 263  *                      becomes possible to write to each socket without
 264  *                      blocking in turn.
 265  *
 266  * @protocol:   Protocol whose connections will get callbacks
 267  */
 268
 269 LWS_VISIBLE int
 270 libwebsocket_callback_on_writable_all_protocol(
 271                                   const struct libwebsocket_protocols *protocol)
 272 {
 273         struct libwebsocket_context *context = protocol->owning_server;
 274         int n;
 275         struct libwebsocket *wsi;
 276
 277         for (n = 0; n < context->fds_count; n++) {
 278                 wsi = context->lws_lookup[context->fds[n].fd];
 279                 if (!wsi)
 280                         continue;
 281                 if (wsi->protocol == protocol)
 282                         libwebsocket_callback_on_writable(context, wsi);
 283         }
 284
 285         return 0;
 286 }