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