net/rxrpc/call_accept.c

   1 /* incoming call handling
   2  *
   3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  */
  11
  12 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  13
  14 #include <linux/module.h>
  15 #include <linux/net.h>
  16 #include <linux/skbuff.h>
  17 #include <linux/errqueue.h>
  18 #include <linux/udp.h>
  19 #include <linux/in.h>
  20 #include <linux/in6.h>
  21 #include <linux/icmp.h>
  22 #include <linux/gfp.h>
  23 #include <linux/circ_buf.h>
  24 #include <net/sock.h>
  25 #include <net/af_rxrpc.h>
  26 #include <net/ip.h>
  27 #include "ar-internal.h"
  28
  29 /*
  30  * Preallocate a single service call, connection and peer and, if possible,
  31  * give them a user ID and attach the user's side of the ID to them.
  32  */
  33 static int rxrpc_service_prealloc_one(struct rxrpc_sock *rx,
  34                                       struct rxrpc_backlog *b,
  35                                       rxrpc_notify_rx_t notify_rx,
  36                                       rxrpc_user_attach_call_t user_attach_call,
  37                                       unsigned long user_call_ID, gfp_t gfp,
  38                                       unsigned int debug_id)
  39 {
  40         const void *here = __builtin_return_address(0);
  41         struct rxrpc_call *call;
  42         struct rxrpc_net *rxnet = rxrpc_net(sock_net(&rx->sk));
  43         int max, tmp;
  44         unsigned int size = RXRPC_BACKLOG_MAX;
  45         unsigned int head, tail, call_head, call_tail;
  46
  47         max = rx->sk.sk_max_ack_backlog;
  48         tmp = rx->sk.sk_ack_backlog;
  49         if (tmp >= max) {
  50                 _leave(" = -ENOBUFS [full %u]", max);
  51                 return -ENOBUFS;
  52         }
  53         max -= tmp;
  54
  55         /* We don't need more conns and peers than we have calls, but on the
  56          * other hand, we shouldn't ever use more peers than conns or conns
  57          * than calls.
  58          */
  59         call_head = b->call_backlog_head;
  60         call_tail = READ_ONCE(b->call_backlog_tail);
  61         tmp = CIRC_CNT(call_head, call_tail, size);
  62         if (tmp >= max) {
  63                 _leave(" = -ENOBUFS [enough %u]", tmp);
  64                 return -ENOBUFS;
  65         }
  66         max = tmp + 1;
  67
  68         head = b->peer_backlog_head;
  69         tail = READ_ONCE(b->peer_backlog_tail);
  70         if (CIRC_CNT(head, tail, size) < max) {
  71                 struct rxrpc_peer *peer = rxrpc_alloc_peer(rx->local, gfp);
  72                 if (!peer)
  73                         return -ENOMEM;
  74                 b->peer_backlog[head] = peer;
  75                 smp_store_release(&b->peer_backlog_head,
  76                                   (head + 1) & (size - 1));
  77         }
  78
  79         head = b->conn_backlog_head;
  80         tail = READ_ONCE(b->conn_backlog_tail);
  81         if (CIRC_CNT(head, tail, size) < max) {
  82                 struct rxrpc_connection *conn;
  83
  84                 conn = rxrpc_prealloc_service_connection(rxnet, gfp);
  85                 if (!conn)
  86                         return -ENOMEM;
  87                 b->conn_backlog[head] = conn;
  88                 smp_store_release(&b->conn_backlog_head,
  89                                   (head + 1) & (size - 1));
  90
  91                 trace_rxrpc_conn(conn, rxrpc_conn_new_service,
  92                                  atomic_read(&conn->usage), here);
  93         }
  94
  95         /* Now it gets complicated, because calls get registered with the
  96          * socket here, particularly if a user ID is preassigned by the user.
  97          */
  98         call = rxrpc_alloc_call(rx, gfp, debug_id);
  99         if (!call)
 100                 return -ENOMEM;
 101         call->flags |= (1 << RXRPC_CALL_IS_SERVICE);
 102         call->state = RXRPC_CALL_SERVER_PREALLOC;
 103
 104         trace_rxrpc_call(call, rxrpc_call_new_service,
 105                          atomic_read(&call->usage),
 106                          here, (const void *)user_call_ID);
 107
 108         write_lock(&rx->call_lock);
 109         if (user_attach_call) {
 110                 struct rxrpc_call *xcall;
 111                 struct rb_node *parent, **pp;
 112
 113                 /* Check the user ID isn't already in use */
 114                 pp = &rx->calls.rb_node;
 115                 parent = NULL;
 116                 while (*pp) {
 117                         parent = *pp;
 118                         xcall = rb_entry(parent, struct rxrpc_call, sock_node);
 119                         if (user_call_ID < xcall->user_call_ID)
 120                                 pp = &(*pp)->rb_left;
 121                         else if (user_call_ID > xcall->user_call_ID)
 122                                 pp = &(*pp)->rb_right;
 123                         else
 124                                 goto id_in_use;
 125                 }
 126
 127                 call->user_call_ID = user_call_ID;
 128                 call->notify_rx = notify_rx;
 129                 rxrpc_get_call(call, rxrpc_call_got_kernel);
 130                 user_attach_call(call, user_call_ID);
 131                 rxrpc_get_call(call, rxrpc_call_got_userid);
 132                 rb_link_node(&call->sock_node, parent, pp);
 133                 rb_insert_color(&call->sock_node, &rx->calls);
 134                 set_bit(RXRPC_CALL_HAS_USERID, &call->flags);
 135         }
 136
 137         list_add(&call->sock_link, &rx->sock_calls);
 138
 139         write_unlock(&rx->call_lock);
 140
 141         rxnet = call->rxnet;
 142         write_lock(&rxnet->call_lock);
 143         list_add_tail(&call->link, &rxnet->calls);
 144         write_unlock(&rxnet->call_lock);
 145
 146         b->call_backlog[call_head] = call;
 147         smp_store_release(&b->call_backlog_head, (call_head + 1) & (size - 1));
 148         _leave(" = 0 [%d -> %lx]", call->debug_id, user_call_ID);
 149         return 0;
 150
 151 id_in_use:
 152         write_unlock(&rx->call_lock);
 153         rxrpc_cleanup_call(call);
 154         _leave(" = -EBADSLT");
 155         return -EBADSLT;
 156 }
 157
 158 /*
 159  * Preallocate sufficient service connections, calls and peers to cover the
 160  * entire backlog of a socket.  When a new call comes in, if we don't have
 161  * sufficient of each available, the call gets rejected as busy or ignored.
 162  *
 163  * The backlog is replenished when a connection is accepted or rejected.
 164  */
 165 int rxrpc_service_prealloc(struct rxrpc_sock *rx, gfp_t gfp)
 166 {
 167         struct rxrpc_backlog *b = rx->backlog;
 168
 169         if (!b) {
 170                 b = kzalloc(sizeof(struct rxrpc_backlog), gfp);
 171                 if (!b)
 172                         return -ENOMEM;
 173                 rx->backlog = b;
 174         }
 175
 176         if (rx->discard_new_call)
 177                 return 0;
 178
 179         while (rxrpc_service_prealloc_one(rx, b, NULL, NULL, 0, gfp,
 180                                           atomic_inc_return(&rxrpc_debug_id)) == 0)
 181                 ;
 182
 183         return 0;
 184 }
 185
 186 /*
 187  * Discard the preallocation on a service.
 188  */
 189 void rxrpc_discard_prealloc(struct rxrpc_sock *rx)
 190 {
 191         struct rxrpc_backlog *b = rx->backlog;
 192         struct rxrpc_net *rxnet = rxrpc_net(sock_net(&rx->sk));
 193         unsigned int size = RXRPC_BACKLOG_MAX, head, tail;
 194
 195         if (!b)
 196                 return;
 197         rx->backlog = NULL;
 198
 199         /* Make sure that there aren't any incoming calls in progress before we
 200          * clear the preallocation buffers.
 201          */
 202         spin_lock_bh(&rx->incoming_lock);
 203         spin_unlock_bh(&rx->incoming_lock);
 204
 205         head = b->peer_backlog_head;
 206         tail = b->peer_backlog_tail;
 207         while (CIRC_CNT(head, tail, size) > 0) {
 208                 struct rxrpc_peer *peer = b->peer_backlog[tail];
 209                 kfree(peer);
 210                 tail = (tail + 1) & (size - 1);
 211         }
 212
 213         head = b->conn_backlog_head;
 214         tail = b->conn_backlog_tail;
 215         while (CIRC_CNT(head, tail, size) > 0) {
 216                 struct rxrpc_connection *conn = b->conn_backlog[tail];
 217                 write_lock(&rxnet->conn_lock);
 218                 list_del(&conn->link);
 219                 list_del(&conn->proc_link);
 220                 write_unlock(&rxnet->conn_lock);
 221                 kfree(conn);
 222                 if (atomic_dec_and_test(&rxnet->nr_conns))
 223                         wake_up_var(&rxnet->nr_conns);
 224                 tail = (tail + 1) & (size - 1);
 225         }
 226
 227         head = b->call_backlog_head;
 228         tail = b->call_backlog_tail;
 229         while (CIRC_CNT(head, tail, size) > 0) {
 230                 struct rxrpc_call *call = b->call_backlog[tail];
 231                 rcu_assign_pointer(call->socket, rx);
 232                 if (rx->discard_new_call) {
 233                         _debug("discard %lx", call->user_call_ID);
 234                         rx->discard_new_call(call, call->user_call_ID);
 235                         rxrpc_put_call(call, rxrpc_call_put_kernel);
 236                 }
 237                 rxrpc_call_completed(call);
 238                 rxrpc_release_call(rx, call);
 239                 rxrpc_put_call(call, rxrpc_call_put);
 240                 tail = (tail + 1) & (size - 1);
 241         }
 242
 243         kfree(b);
 244 }
 245
 246 /*
 247  * Allocate a new incoming call from the prealloc pool, along with a connection
 248  * and a peer as necessary.
 249  */
 250 static struct rxrpc_call *rxrpc_alloc_incoming_call(struct rxrpc_sock *rx,
 251                                                     struct rxrpc_local *local,
 252                                                     struct rxrpc_connection *conn,
 253                                                     struct sk_buff *skb)
 254 {
 255         struct rxrpc_backlog *b = rx->backlog;
 256         struct rxrpc_peer *peer, *xpeer;
 257         struct rxrpc_call *call;
 258         unsigned short call_head, conn_head, peer_head;
 259         unsigned short call_tail, conn_tail, peer_tail;
 260         unsigned short call_count, conn_count;
 261
 262         /* #calls >= #conns >= #peers must hold true. */
 263         call_head = smp_load_acquire(&b->call_backlog_head);
 264         call_tail = b->call_backlog_tail;
 265         call_count = CIRC_CNT(call_head, call_tail, RXRPC_BACKLOG_MAX);
 266         conn_head = smp_load_acquire(&b->conn_backlog_head);
 267         conn_tail = b->conn_backlog_tail;
 268         conn_count = CIRC_CNT(conn_head, conn_tail, RXRPC_BACKLOG_MAX);
 269         ASSERTCMP(conn_count, >=, call_count);
 270         peer_head = smp_load_acquire(&b->peer_backlog_head);
 271         peer_tail = b->peer_backlog_tail;
 272         ASSERTCMP(CIRC_CNT(peer_head, peer_tail, RXRPC_BACKLOG_MAX), >=,
 273                   conn_count);
 274
 275         if (call_count == 0)
 276                 return NULL;
 277
 278         if (!conn) {
 279                 /* No connection.  We're going to need a peer to start off
 280                  * with.  If one doesn't yet exist, use a spare from the
 281                  * preallocation set.  We dump the address into the spare in
 282                  * anticipation - and to save on stack space.
 283                  */
 284                 xpeer = b->peer_backlog[peer_tail];
 285                 if (rxrpc_extract_addr_from_skb(local, &xpeer->srx, skb) < 0)
 286                         return NULL;
 287
 288                 peer = rxrpc_lookup_incoming_peer(local, xpeer);
 289                 if (peer == xpeer) {
 290                         b->peer_backlog[peer_tail] = NULL;
 291                         smp_store_release(&b->peer_backlog_tail,
 292                                           (peer_tail + 1) &
 293                                           (RXRPC_BACKLOG_MAX - 1));
 294                 }
 295
 296                 /* Now allocate and set up the connection */
 297                 conn = b->conn_backlog[conn_tail];
 298                 b->conn_backlog[conn_tail] = NULL;
 299                 smp_store_release(&b->conn_backlog_tail,
 300                                   (conn_tail + 1) & (RXRPC_BACKLOG_MAX - 1));
 301                 conn->params.local = rxrpc_get_local(local);
 302                 conn->params.peer = peer;
 303                 rxrpc_see_connection(conn);
 304                 rxrpc_new_incoming_connection(rx, conn, skb);
 305         } else {
 306                 rxrpc_get_connection(conn);
 307         }
 308
 309         /* And now we can allocate and set up a new call */
 310         call = b->call_backlog[call_tail];
 311         b->call_backlog[call_tail] = NULL;
 312         smp_store_release(&b->call_backlog_tail,
 313                           (call_tail + 1) & (RXRPC_BACKLOG_MAX - 1));
 314
 315         rxrpc_see_call(call);
 316         call->conn = conn;
 317         call->peer = rxrpc_get_peer(conn->params.peer);
 318         call->cong_cwnd = call->peer->cong_cwnd;
 319         return call;
 320 }
 321
 322 /*
 323  * Set up a new incoming call.  Called in BH context with the RCU read lock
 324  * held.
 325  *
 326  * If this is for a kernel service, when we allocate the call, it will have
 327  * three refs on it: (1) the kernel service, (2) the user_call_ID tree, (3) the
 328  * retainer ref obtained from the backlog buffer.  Prealloc calls for userspace
 329  * services only have the ref from the backlog buffer.  We want to pass this
 330  * ref to non-BH context to dispose of.
 331  *
 332  * If we want to report an error, we mark the skb with the packet type and
 333  * abort code and return NULL.
 334  *
 335  * The call is returned with the user access mutex held.
 336  */
 337 struct rxrpc_call *rxrpc_new_incoming_call(struct rxrpc_local *local,
 338                                            struct rxrpc_connection *conn,
 339                                            struct sk_buff *skb)
 340 {
 341         struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
 342         struct rxrpc_sock *rx;
 343         struct rxrpc_call *call;
 344         u16 service_id = sp->hdr.serviceId;
 345
 346         _enter("");
 347
 348         /* Get the socket providing the service */
 349         rx = rcu_dereference(local->service);
 350         if (rx && (service_id == rx->srx.srx_service ||
 351                    service_id == rx->second_service))
 352                 goto found_service;
 353
 354         trace_rxrpc_abort(0, "INV", sp->hdr.cid, sp->hdr.callNumber, sp->hdr.seq,
 355                           RX_INVALID_OPERATION, EOPNOTSUPP);
 356         skb->mark = RXRPC_SKB_MARK_LOCAL_ABORT;
 357         skb->priority = RX_INVALID_OPERATION;
 358         _leave(" = NULL [service]");
 359         return NULL;
 360
 361 found_service:
 362         spin_lock(&rx->incoming_lock);
 363         if (rx->sk.sk_state == RXRPC_SERVER_LISTEN_DISABLED ||
 364             rx->sk.sk_state == RXRPC_CLOSE) {
 365                 trace_rxrpc_abort(0, "CLS", sp->hdr.cid, sp->hdr.callNumber,
 366                                   sp->hdr.seq, RX_INVALID_OPERATION, ESHUTDOWN);
 367                 skb->mark = RXRPC_SKB_MARK_LOCAL_ABORT;
 368                 skb->priority = RX_INVALID_OPERATION;
 369                 _leave(" = NULL [close]");
 370                 call = NULL;
 371                 goto out;
 372         }
 373
 374         call = rxrpc_alloc_incoming_call(rx, local, conn, skb);
 375         if (!call) {
 376                 skb->mark = RXRPC_SKB_MARK_BUSY;
 377                 _leave(" = NULL [busy]");
 378                 call = NULL;
 379                 goto out;
 380         }
 381
 382         trace_rxrpc_receive(call, rxrpc_receive_incoming,
 383                             sp->hdr.serial, sp->hdr.seq);
 384
 385         /* Lock the call to prevent rxrpc_kernel_send/recv_data() and
 386          * sendmsg()/recvmsg() inconveniently stealing the mutex once the
 387          * notification is generated.
 388          *
 389          * The BUG should never happen because the kernel should be well
 390          * behaved enough not to access the call before the first notification
 391          * event and userspace is prevented from doing so until the state is
 392          * appropriate.
 393          */
 394         if (!mutex_trylock(&call->user_mutex))
 395                 BUG();
 396
 397         /* Make the call live. */
 398         rxrpc_incoming_call(rx, call, skb);
 399         conn = call->conn;
 400
 401         if (rx->notify_new_call)
 402                 rx->notify_new_call(&rx->sk, call, call->user_call_ID);
 403         else
 404                 sk_acceptq_added(&rx->sk);
 405
 406         spin_lock(&conn->state_lock);
 407         switch (conn->state) {
 408         case RXRPC_CONN_SERVICE_UNSECURED:
 409                 conn->state = RXRPC_CONN_SERVICE_CHALLENGING;
 410                 set_bit(RXRPC_CONN_EV_CHALLENGE, &call->conn->events);
 411                 rxrpc_queue_conn(call->conn);
 412                 break;
 413
 414         case RXRPC_CONN_SERVICE:
 415                 write_lock(&call->state_lock);
 416                 if (rx->discard_new_call)
 417                         call->state = RXRPC_CALL_SERVER_RECV_REQUEST;
 418                 else
 419                         call->state = RXRPC_CALL_SERVER_ACCEPTING;
 420                 write_unlock(&call->state_lock);
 421                 break;
 422
 423         case RXRPC_CONN_REMOTELY_ABORTED:
 424                 rxrpc_set_call_completion(call, RXRPC_CALL_REMOTELY_ABORTED,
 425                                           conn->remote_abort, -ECONNABORTED);
 426                 break;
 427         case RXRPC_CONN_LOCALLY_ABORTED:
 428                 rxrpc_abort_call("CON", call, sp->hdr.seq,
 429                                  conn->local_abort, -ECONNABORTED);
 430                 break;
 431         default:
 432                 BUG();
 433         }
 434         spin_unlock(&conn->state_lock);
 435
 436         if (call->state == RXRPC_CALL_SERVER_ACCEPTING)
 437                 rxrpc_notify_socket(call);
 438
 439         /* We have to discard the prealloc queue's ref here and rely on a
 440          * combination of the RCU read lock and refs held either by the socket
 441          * (recvmsg queue, to-be-accepted queue or user ID tree) or the kernel
 442          * service to prevent the call from being deallocated too early.
 443          */
 444         rxrpc_put_call(call, rxrpc_call_put);
 445
 446         _leave(" = %p{%d}", call, call->debug_id);
 447 out:
 448         spin_unlock(&rx->incoming_lock);
 449         return call;
 450 }
 451
 452 /*
 453  * handle acceptance of a call by userspace
 454  * - assign the user call ID to the call at the front of the queue
 455  * - called with the socket locked.
 456  */
 457 struct rxrpc_call *rxrpc_accept_call(struct rxrpc_sock *rx,
 458                                      unsigned long user_call_ID,
 459                                      rxrpc_notify_rx_t notify_rx)
 460         __releases(&rx->sk.sk_lock.slock)
 461         __acquires(call->user_mutex)
 462 {
 463         struct rxrpc_call *call;
 464         struct rb_node *parent, **pp;
 465         int ret;
 466
 467         _enter(",%lx", user_call_ID);
 468
 469         ASSERT(!irqs_disabled());
 470
 471         write_lock(&rx->call_lock);
 472
 473         if (list_empty(&rx->to_be_accepted)) {
 474                 write_unlock(&rx->call_lock);
 475                 release_sock(&rx->sk);
 476                 kleave(" = -ENODATA [empty]");
 477                 return ERR_PTR(-ENODATA);
 478         }
 479
 480         /* check the user ID isn't already in use */
 481         pp = &rx->calls.rb_node;
 482         parent = NULL;
 483         while (*pp) {
 484                 parent = *pp;
 485                 call = rb_entry(parent, struct rxrpc_call, sock_node);
 486
 487                 if (user_call_ID < call->user_call_ID)
 488                         pp = &(*pp)->rb_left;
 489                 else if (user_call_ID > call->user_call_ID)
 490                         pp = &(*pp)->rb_right;
 491                 else
 492                         goto id_in_use;
 493         }
 494
 495         /* Dequeue the first call and check it's still valid.  We gain
 496          * responsibility for the queue's reference.
 497          */
 498         call = list_entry(rx->to_be_accepted.next,
 499                           struct rxrpc_call, accept_link);
 500         write_unlock(&rx->call_lock);
 501
 502         /* We need to gain the mutex from the interrupt handler without
 503          * upsetting lockdep, so we have to release it there and take it here.
 504          * We are, however, still holding the socket lock, so other accepts
 505          * must wait for us and no one can add the user ID behind our backs.
 506          */
 507         if (mutex_lock_interruptible(&call->user_mutex) < 0) {
 508                 release_sock(&rx->sk);
 509                 kleave(" = -ERESTARTSYS");
 510                 return ERR_PTR(-ERESTARTSYS);
 511         }
 512
 513         write_lock(&rx->call_lock);
 514         list_del_init(&call->accept_link);
 515         sk_acceptq_removed(&rx->sk);
 516         rxrpc_see_call(call);
 517
 518         /* Find the user ID insertion point. */
 519         pp = &rx->calls.rb_node;
 520         parent = NULL;
 521         while (*pp) {
 522                 parent = *pp;
 523                 call = rb_entry(parent, struct rxrpc_call, sock_node);
 524
 525                 if (user_call_ID < call->user_call_ID)
 526                         pp = &(*pp)->rb_left;
 527                 else if (user_call_ID > call->user_call_ID)
 528                         pp = &(*pp)->rb_right;
 529                 else
 530                         BUG();
 531         }
 532
 533         write_lock_bh(&call->state_lock);
 534         switch (call->state) {
 535         case RXRPC_CALL_SERVER_ACCEPTING:
 536                 call->state = RXRPC_CALL_SERVER_RECV_REQUEST;
 537                 break;
 538         case RXRPC_CALL_COMPLETE:
 539                 ret = call->error;
 540                 goto out_release;
 541         default:
 542                 BUG();
 543         }
 544
 545         /* formalise the acceptance */
 546         call->notify_rx = notify_rx;
 547         call->user_call_ID = user_call_ID;
 548         rxrpc_get_call(call, rxrpc_call_got_userid);
 549         rb_link_node(&call->sock_node, parent, pp);
 550         rb_insert_color(&call->sock_node, &rx->calls);
 551         if (test_and_set_bit(RXRPC_CALL_HAS_USERID, &call->flags))
 552                 BUG();
 553
 554         write_unlock_bh(&call->state_lock);
 555         write_unlock(&rx->call_lock);
 556         rxrpc_notify_socket(call);
 557         rxrpc_service_prealloc(rx, GFP_KERNEL);
 558         release_sock(&rx->sk);
 559         _leave(" = %p{%d}", call, call->debug_id);
 560         return call;
 561
 562 out_release:
 563         _debug("release %p", call);
 564         write_unlock_bh(&call->state_lock);
 565         write_unlock(&rx->call_lock);
 566         rxrpc_release_call(rx, call);
 567         rxrpc_put_call(call, rxrpc_call_put);
 568         goto out;
 569
 570 id_in_use:
 571         ret = -EBADSLT;
 572         write_unlock(&rx->call_lock);
 573 out:
 574         rxrpc_service_prealloc(rx, GFP_KERNEL);
 575         release_sock(&rx->sk);
 576         _leave(" = %d", ret);
 577         return ERR_PTR(ret);
 578 }
 579
 580 /*
 581  * Handle rejection of a call by userspace
 582  * - reject the call at the front of the queue
 583  */
 584 int rxrpc_reject_call(struct rxrpc_sock *rx)
 585 {
 586         struct rxrpc_call *call;
 587         bool abort = false;
 588         int ret;
 589
 590         _enter("");
 591
 592         ASSERT(!irqs_disabled());
 593
 594         write_lock(&rx->call_lock);
 595
 596         if (list_empty(&rx->to_be_accepted)) {
 597                 write_unlock(&rx->call_lock);
 598                 return -ENODATA;
 599         }
 600
 601         /* Dequeue the first call and check it's still valid.  We gain
 602          * responsibility for the queue's reference.
 603          */
 604         call = list_entry(rx->to_be_accepted.next,
 605                           struct rxrpc_call, accept_link);
 606         list_del_init(&call->accept_link);
 607         sk_acceptq_removed(&rx->sk);
 608         rxrpc_see_call(call);
 609
 610         write_lock_bh(&call->state_lock);
 611         switch (call->state) {
 612         case RXRPC_CALL_SERVER_ACCEPTING:
 613                 __rxrpc_abort_call("REJ", call, 1, RX_USER_ABORT, -ECONNABORTED);
 614                 abort = true;
 615                 /* fall through */
 616         case RXRPC_CALL_COMPLETE:
 617                 ret = call->error;
 618                 goto out_discard;
 619         default:
 620                 BUG();
 621         }
 622
 623 out_discard:
 624         write_unlock_bh(&call->state_lock);
 625         write_unlock(&rx->call_lock);
 626         if (abort) {
 627                 rxrpc_send_abort_packet(call);
 628                 rxrpc_release_call(rx, call);
 629                 rxrpc_put_call(call, rxrpc_call_put);
 630         }
 631         rxrpc_service_prealloc(rx, GFP_KERNEL);
 632         _leave(" = %d", ret);
 633         return ret;
 634 }
 635
 636 /*
 637  * rxrpc_kernel_charge_accept - Charge up socket with preallocated calls
 638  * @sock: The socket on which to preallocate
 639  * @notify_rx: Event notification function for the call
 640  * @user_attach_call: Func to attach call to user_call_ID
 641  * @user_call_ID: The tag to attach to the preallocated call
 642  * @gfp: The allocation conditions.
 643  * @debug_id: The tracing debug ID.
 644  *
 645  * Charge up the socket with preallocated calls, each with a user ID.  A
 646  * function should be provided to effect the attachment from the user's side.
 647  * The user is given a ref to hold on the call.
 648  *
 649  * Note that the call may be come connected before this function returns.
 650  */
 651 int rxrpc_kernel_charge_accept(struct socket *sock,
 652                                rxrpc_notify_rx_t notify_rx,
 653                                rxrpc_user_attach_call_t user_attach_call,
 654                                unsigned long user_call_ID, gfp_t gfp,
 655                                unsigned int debug_id)
 656 {
 657         struct rxrpc_sock *rx = rxrpc_sk(sock->sk);
 658         struct rxrpc_backlog *b = rx->backlog;
 659
 660         if (sock->sk->sk_state == RXRPC_CLOSE)
 661                 return -ESHUTDOWN;
 662
 663         return rxrpc_service_prealloc_one(rx, b, notify_rx,
 664                                           user_attach_call, user_call_ID,
 665                                           gfp, debug_id);
 666 }
 667 EXPORT_SYMBOL(rxrpc_kernel_charge_accept);