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 {
  39         const void *here = __builtin_return_address(0);
  40         struct rxrpc_call *call;
  41         int max, tmp;
  42         unsigned int size = RXRPC_BACKLOG_MAX;
  43         unsigned int head, tail, call_head, call_tail;
  44
  45         max = rx->sk.sk_max_ack_backlog;
  46         tmp = rx->sk.sk_ack_backlog;
  47         if (tmp >= max) {
  48                 _leave(" = -ENOBUFS [full %u]", max);
  49                 return -ENOBUFS;
  50         }
  51         max -= tmp;
  52
  53         /* We don't need more conns and peers than we have calls, but on the
  54          * other hand, we shouldn't ever use more peers than conns or conns
  55          * than calls.
  56          */
  57         call_head = b->call_backlog_head;
  58         call_tail = READ_ONCE(b->call_backlog_tail);
  59         tmp = CIRC_CNT(call_head, call_tail, size);
  60         if (tmp >= max) {
  61                 _leave(" = -ENOBUFS [enough %u]", tmp);
  62                 return -ENOBUFS;
  63         }
  64         max = tmp + 1;
  65
  66         head = b->peer_backlog_head;
  67         tail = READ_ONCE(b->peer_backlog_tail);
  68         if (CIRC_CNT(head, tail, size) < max) {
  69                 struct rxrpc_peer *peer = rxrpc_alloc_peer(rx->local, gfp);
  70                 if (!peer)
  71                         return -ENOMEM;
  72                 b->peer_backlog[head] = peer;
  73                 smp_store_release(&b->peer_backlog_head,
  74                                   (head + 1) & (size - 1));
  75         }
  76
  77         head = b->conn_backlog_head;
  78         tail = READ_ONCE(b->conn_backlog_tail);
  79         if (CIRC_CNT(head, tail, size) < max) {
  80                 struct rxrpc_connection *conn;
  81
  82                 conn = rxrpc_prealloc_service_connection(gfp);
  83                 if (!conn)
  84                         return -ENOMEM;
  85                 b->conn_backlog[head] = conn;
  86                 smp_store_release(&b->conn_backlog_head,
  87                                   (head + 1) & (size - 1));
  88         }
  89
  90         /* Now it gets complicated, because calls get registered with the
  91          * socket here, particularly if a user ID is preassigned by the user.
  92          */
  93         call = rxrpc_alloc_call(gfp);
  94         if (!call)
  95                 return -ENOMEM;
  96         call->flags |= (1 << RXRPC_CALL_IS_SERVICE);
  97         call->state = RXRPC_CALL_SERVER_PREALLOC;
  98
  99         trace_rxrpc_call(call, rxrpc_call_new_service,
 100                          atomic_read(&call->usage),
 101                          here, (const void *)user_call_ID);
 102
 103         write_lock(&rx->call_lock);
 104         if (user_attach_call) {
 105                 struct rxrpc_call *xcall;
 106                 struct rb_node *parent, **pp;
 107
 108                 /* Check the user ID isn't already in use */
 109                 pp = &rx->calls.rb_node;
 110                 parent = NULL;
 111                 while (*pp) {
 112                         parent = *pp;
 113                         xcall = rb_entry(parent, struct rxrpc_call, sock_node);
 114                         if (user_call_ID < call->user_call_ID)
 115                                 pp = &(*pp)->rb_left;
 116                         else if (user_call_ID > call->user_call_ID)
 117                                 pp = &(*pp)->rb_right;
 118                         else
 119                                 goto id_in_use;
 120                 }
 121
 122                 call->user_call_ID = user_call_ID;
 123                 call->notify_rx = notify_rx;
 124                 rxrpc_get_call(call, rxrpc_call_got);
 125                 user_attach_call(call, user_call_ID);
 126                 rxrpc_get_call(call, rxrpc_call_got_userid);
 127                 rb_link_node(&call->sock_node, parent, pp);
 128                 rb_insert_color(&call->sock_node, &rx->calls);
 129                 set_bit(RXRPC_CALL_HAS_USERID, &call->flags);
 130         }
 131
 132         write_unlock(&rx->call_lock);
 133
 134         write_lock(&rxrpc_call_lock);
 135         list_add_tail(&call->link, &rxrpc_calls);
 136         write_unlock(&rxrpc_call_lock);
 137
 138         b->call_backlog[call_head] = call;
 139         smp_store_release(&b->call_backlog_head, (call_head + 1) & (size - 1));
 140         _leave(" = 0 [%d -> %lx]", call->debug_id, user_call_ID);
 141         return 0;
 142
 143 id_in_use:
 144         write_unlock(&rx->call_lock);
 145         rxrpc_cleanup_call(call);
 146         _leave(" = -EBADSLT");
 147         return -EBADSLT;
 148 }
 149
 150 /*
 151  * Preallocate sufficient service connections, calls and peers to cover the
 152  * entire backlog of a socket.  When a new call comes in, if we don't have
 153  * sufficient of each available, the call gets rejected as busy or ignored.
 154  *
 155  * The backlog is replenished when a connection is accepted or rejected.
 156  */
 157 int rxrpc_service_prealloc(struct rxrpc_sock *rx, gfp_t gfp)
 158 {
 159         struct rxrpc_backlog *b = rx->backlog;
 160
 161         if (!b) {
 162                 b = kzalloc(sizeof(struct rxrpc_backlog), gfp);
 163                 if (!b)
 164                         return -ENOMEM;
 165                 rx->backlog = b;
 166         }
 167
 168         if (rx->discard_new_call)
 169                 return 0;
 170
 171         while (rxrpc_service_prealloc_one(rx, b, NULL, NULL, 0, gfp) == 0)
 172                 ;
 173
 174         return 0;
 175 }
 176
 177 /*
 178  * Discard the preallocation on a service.
 179  */
 180 void rxrpc_discard_prealloc(struct rxrpc_sock *rx)
 181 {
 182         struct rxrpc_backlog *b = rx->backlog;
 183         unsigned int size = RXRPC_BACKLOG_MAX, head, tail;
 184
 185         if (!b)
 186                 return;
 187         rx->backlog = NULL;
 188
 189         head = b->peer_backlog_head;
 190         tail = b->peer_backlog_tail;
 191         while (CIRC_CNT(head, tail, size) > 0) {
 192                 struct rxrpc_peer *peer = b->peer_backlog[tail];
 193                 kfree(peer);
 194                 tail = (tail + 1) & (size - 1);
 195         }
 196
 197         head = b->conn_backlog_head;
 198         tail = b->conn_backlog_tail;
 199         while (CIRC_CNT(head, tail, size) > 0) {
 200                 struct rxrpc_connection *conn = b->conn_backlog[tail];
 201                 write_lock(&rxrpc_connection_lock);
 202                 list_del(&conn->link);
 203                 list_del(&conn->proc_link);
 204                 write_unlock(&rxrpc_connection_lock);
 205                 kfree(conn);
 206                 tail = (tail + 1) & (size - 1);
 207         }
 208
 209         head = b->call_backlog_head;
 210         tail = b->call_backlog_tail;
 211         while (CIRC_CNT(head, tail, size) > 0) {
 212                 struct rxrpc_call *call = b->call_backlog[tail];
 213                 if (rx->discard_new_call) {
 214                         _debug("discard %lx", call->user_call_ID);
 215                         rx->discard_new_call(call, call->user_call_ID);
 216                 }
 217                 rxrpc_call_completed(call);
 218                 rxrpc_release_call(rx, call);
 219                 rxrpc_put_call(call, rxrpc_call_put);
 220                 tail = (tail + 1) & (size - 1);
 221         }
 222
 223         kfree(b);
 224 }
 225
 226 /*
 227  * generate a connection-level abort
 228  */
 229 static int rxrpc_busy(struct rxrpc_local *local, struct sockaddr_rxrpc *srx,
 230                       struct rxrpc_wire_header *whdr)
 231 {
 232         struct msghdr msg;
 233         struct kvec iov[1];
 234         size_t len;
 235         int ret;
 236
 237         _enter("%d,,", local->debug_id);
 238
 239         whdr->type      = RXRPC_PACKET_TYPE_BUSY;
 240         whdr->serial    = htonl(1);
 241
 242         msg.msg_name    = &srx->transport.sin;
 243         msg.msg_namelen = sizeof(srx->transport.sin);
 244         msg.msg_control = NULL;
 245         msg.msg_controllen = 0;
 246         msg.msg_flags   = 0;
 247
 248         iov[0].iov_base = whdr;
 249         iov[0].iov_len  = sizeof(*whdr);
 250
 251         len = iov[0].iov_len;
 252
 253         _proto("Tx BUSY %%1");
 254
 255         ret = kernel_sendmsg(local->socket, &msg, iov, 1, len);
 256         if (ret < 0) {
 257                 _leave(" = -EAGAIN [sendmsg failed: %d]", ret);
 258                 return -EAGAIN;
 259         }
 260
 261         _leave(" = 0");
 262         return 0;
 263 }
 264
 265 /*
 266  * accept an incoming call that needs peer, transport and/or connection setting
 267  * up
 268  */
 269 static int rxrpc_accept_incoming_call(struct rxrpc_local *local,
 270                                       struct rxrpc_sock *rx,
 271                                       struct sk_buff *skb,
 272                                       struct sockaddr_rxrpc *srx)
 273 {
 274         struct rxrpc_connection *conn;
 275         struct rxrpc_skb_priv *sp, *nsp;
 276         struct rxrpc_call *call;
 277         struct sk_buff *notification;
 278         int ret;
 279
 280         _enter("");
 281
 282         sp = rxrpc_skb(skb);
 283
 284         /* get a notification message to send to the server app */
 285         notification = alloc_skb(0, GFP_NOFS);
 286         if (!notification) {
 287                 _debug("no memory");
 288                 ret = -ENOMEM;
 289                 goto error_nofree;
 290         }
 291         rxrpc_new_skb(notification);
 292         notification->mark = RXRPC_SKB_MARK_NEW_CALL;
 293
 294         conn = rxrpc_incoming_connection(local, srx, skb);
 295         if (IS_ERR(conn)) {
 296                 _debug("no conn");
 297                 ret = PTR_ERR(conn);
 298                 goto error;
 299         }
 300
 301         call = rxrpc_incoming_call(rx, conn, skb);
 302         rxrpc_put_connection(conn);
 303         if (IS_ERR(call)) {
 304                 _debug("no call");
 305                 ret = PTR_ERR(call);
 306                 goto error;
 307         }
 308
 309         /* attach the call to the socket */
 310         read_lock_bh(&local->services_lock);
 311         if (rx->sk.sk_state == RXRPC_CLOSE)
 312                 goto invalid_service;
 313
 314         write_lock(&rx->call_lock);
 315         if (!test_and_set_bit(RXRPC_CALL_INIT_ACCEPT, &call->flags)) {
 316                 rxrpc_get_call(call, rxrpc_call_got);
 317
 318                 spin_lock(&call->conn->state_lock);
 319                 if (sp->hdr.securityIndex > 0 &&
 320                     call->conn->state == RXRPC_CONN_SERVICE_UNSECURED) {
 321                         _debug("await conn sec");
 322                         list_add_tail(&call->accept_link, &rx->secureq);
 323                         call->conn->state = RXRPC_CONN_SERVICE_CHALLENGING;
 324                         set_bit(RXRPC_CONN_EV_CHALLENGE, &call->conn->events);
 325                         rxrpc_queue_conn(call->conn);
 326                 } else {
 327                         _debug("conn ready");
 328                         call->state = RXRPC_CALL_SERVER_ACCEPTING;
 329                         list_add_tail(&call->accept_link, &rx->acceptq);
 330                         rxrpc_get_call_for_skb(call, notification);
 331                         nsp = rxrpc_skb(notification);
 332                         nsp->call = call;
 333
 334                         ASSERTCMP(atomic_read(&call->usage), >=, 3);
 335
 336                         _debug("notify");
 337                         spin_lock(&call->lock);
 338                         ret = rxrpc_queue_rcv_skb(call, notification, true,
 339                                                   false);
 340                         spin_unlock(&call->lock);
 341                         notification = NULL;
 342                         BUG_ON(ret < 0);
 343                 }
 344                 spin_unlock(&call->conn->state_lock);
 345
 346                 _debug("queued");
 347         }
 348         write_unlock(&rx->call_lock);
 349
 350         _debug("process");
 351         rxrpc_fast_process_packet(call, skb);
 352
 353         _debug("done");
 354         read_unlock_bh(&local->services_lock);
 355         rxrpc_free_skb(notification);
 356         rxrpc_put_call(call, rxrpc_call_put);
 357         _leave(" = 0");
 358         return 0;
 359
 360 invalid_service:
 361         _debug("invalid");
 362         read_unlock_bh(&local->services_lock);
 363
 364         rxrpc_release_call(rx, call);
 365         rxrpc_put_call(call, rxrpc_call_put);
 366         ret = -ECONNREFUSED;
 367 error:
 368         rxrpc_free_skb(notification);
 369 error_nofree:
 370         _leave(" = %d", ret);
 371         return ret;
 372 }
 373
 374 /*
 375  * accept incoming calls that need peer, transport and/or connection setting up
 376  * - the packets we get are all incoming client DATA packets that have seq == 1
 377  */
 378 void rxrpc_accept_incoming_calls(struct rxrpc_local *local)
 379 {
 380         struct rxrpc_skb_priv *sp;
 381         struct sockaddr_rxrpc srx;
 382         struct rxrpc_sock *rx;
 383         struct rxrpc_wire_header whdr;
 384         struct sk_buff *skb;
 385         int ret;
 386
 387         _enter("%d", local->debug_id);
 388
 389         skb = skb_dequeue(&local->accept_queue);
 390         if (!skb) {
 391                 _leave("\n");
 392                 return;
 393         }
 394
 395         _net("incoming call skb %p", skb);
 396
 397         rxrpc_see_skb(skb);
 398         sp = rxrpc_skb(skb);
 399
 400         /* Set up a response packet header in case we need it */
 401         whdr.epoch      = htonl(sp->hdr.epoch);
 402         whdr.cid        = htonl(sp->hdr.cid);
 403         whdr.callNumber = htonl(sp->hdr.callNumber);
 404         whdr.seq        = htonl(sp->hdr.seq);
 405         whdr.serial     = 0;
 406         whdr.flags      = 0;
 407         whdr.type       = 0;
 408         whdr.userStatus = 0;
 409         whdr.securityIndex = sp->hdr.securityIndex;
 410         whdr._rsvd      = 0;
 411         whdr.serviceId  = htons(sp->hdr.serviceId);
 412
 413         if (rxrpc_extract_addr_from_skb(&srx, skb) < 0)
 414                 goto drop;
 415
 416         /* get the socket providing the service */
 417         read_lock_bh(&local->services_lock);
 418         hlist_for_each_entry(rx, &local->services, listen_link) {
 419                 if (rx->srx.srx_service == sp->hdr.serviceId &&
 420                     rx->sk.sk_state != RXRPC_CLOSE)
 421                         goto found_service;
 422         }
 423         read_unlock_bh(&local->services_lock);
 424         goto invalid_service;
 425
 426 found_service:
 427         _debug("found service %hd", rx->srx.srx_service);
 428         if (sk_acceptq_is_full(&rx->sk))
 429                 goto backlog_full;
 430         sk_acceptq_added(&rx->sk);
 431         read_unlock_bh(&local->services_lock);
 432
 433         ret = rxrpc_accept_incoming_call(local, rx, skb, &srx);
 434         if (ret < 0)
 435                 sk_acceptq_removed(&rx->sk);
 436         switch (ret) {
 437         case -ECONNRESET: /* old calls are ignored */
 438         case -ECONNABORTED: /* aborted calls are reaborted or ignored */
 439         case 0:
 440                 return;
 441         case -ECONNREFUSED:
 442                 goto invalid_service;
 443         case -EBUSY:
 444                 goto busy;
 445         case -EKEYREJECTED:
 446                 goto security_mismatch;
 447         default:
 448                 BUG();
 449         }
 450
 451 backlog_full:
 452         read_unlock_bh(&local->services_lock);
 453 busy:
 454         rxrpc_busy(local, &srx, &whdr);
 455         rxrpc_free_skb(skb);
 456         return;
 457
 458 drop:
 459         rxrpc_free_skb(skb);
 460         return;
 461
 462 invalid_service:
 463         skb->priority = RX_INVALID_OPERATION;
 464         rxrpc_reject_packet(local, skb);
 465         return;
 466
 467         /* can't change connection security type mid-flow */
 468 security_mismatch:
 469         skb->priority = RX_PROTOCOL_ERROR;
 470         rxrpc_reject_packet(local, skb);
 471         return;
 472 }
 473
 474 /*
 475  * handle acceptance of a call by userspace
 476  * - assign the user call ID to the call at the front of the queue
 477  */
 478 struct rxrpc_call *rxrpc_accept_call(struct rxrpc_sock *rx,
 479                                      unsigned long user_call_ID,
 480                                      rxrpc_notify_rx_t notify_rx)
 481 {
 482         struct rxrpc_call *call;
 483         struct rb_node *parent, **pp;
 484         int ret;
 485
 486         _enter(",%lx", user_call_ID);
 487
 488         ASSERT(!irqs_disabled());
 489
 490         write_lock(&rx->call_lock);
 491
 492         ret = -ENODATA;
 493         if (list_empty(&rx->acceptq))
 494                 goto out;
 495
 496         /* check the user ID isn't already in use */
 497         ret = -EBADSLT;
 498         pp = &rx->calls.rb_node;
 499         parent = NULL;
 500         while (*pp) {
 501                 parent = *pp;
 502                 call = rb_entry(parent, struct rxrpc_call, sock_node);
 503
 504                 if (user_call_ID < call->user_call_ID)
 505                         pp = &(*pp)->rb_left;
 506                 else if (user_call_ID > call->user_call_ID)
 507                         pp = &(*pp)->rb_right;
 508                 else
 509                         goto out;
 510         }
 511
 512         /* dequeue the first call and check it's still valid */
 513         call = list_entry(rx->acceptq.next, struct rxrpc_call, accept_link);
 514         list_del_init(&call->accept_link);
 515         sk_acceptq_removed(&rx->sk);
 516         rxrpc_see_call(call);
 517
 518         write_lock_bh(&call->state_lock);
 519         switch (call->state) {
 520         case RXRPC_CALL_SERVER_ACCEPTING:
 521                 call->state = RXRPC_CALL_SERVER_RECV_REQUEST;
 522                 break;
 523         case RXRPC_CALL_COMPLETE:
 524                 ret = call->error;
 525                 goto out_release;
 526         default:
 527                 BUG();
 528         }
 529
 530         /* formalise the acceptance */
 531         rxrpc_get_call(call, rxrpc_call_got_userid);
 532         call->notify_rx = notify_rx;
 533         call->user_call_ID = user_call_ID;
 534         rb_link_node(&call->sock_node, parent, pp);
 535         rb_insert_color(&call->sock_node, &rx->calls);
 536         if (test_and_set_bit(RXRPC_CALL_HAS_USERID, &call->flags))
 537                 BUG();
 538         if (test_and_set_bit(RXRPC_CALL_EV_ACCEPTED, &call->events))
 539                 BUG();
 540
 541         write_unlock_bh(&call->state_lock);
 542         write_unlock(&rx->call_lock);
 543         rxrpc_queue_call(call);
 544         _leave(" = %p{%d}", call, call->debug_id);
 545         return call;
 546
 547 out_release:
 548         write_unlock_bh(&call->state_lock);
 549         write_unlock(&rx->call_lock);
 550         _debug("release %p", call);
 551         rxrpc_release_call(rx, call);
 552         _leave(" = %d", ret);
 553         return ERR_PTR(ret);
 554 out:
 555         write_unlock(&rx->call_lock);
 556         _leave(" = %d", ret);
 557         return ERR_PTR(ret);
 558 }
 559
 560 /*
 561  * Handle rejection of a call by userspace
 562  * - reject the call at the front of the queue
 563  */
 564 int rxrpc_reject_call(struct rxrpc_sock *rx)
 565 {
 566         struct rxrpc_call *call;
 567         int ret;
 568
 569         _enter("");
 570
 571         ASSERT(!irqs_disabled());
 572
 573         write_lock(&rx->call_lock);
 574
 575         ret = -ENODATA;
 576         if (list_empty(&rx->acceptq)) {
 577                 write_unlock(&rx->call_lock);
 578                 _leave(" = -ENODATA");
 579                 return -ENODATA;
 580         }
 581
 582         /* dequeue the first call and check it's still valid */
 583         call = list_entry(rx->acceptq.next, struct rxrpc_call, accept_link);
 584         list_del_init(&call->accept_link);
 585         sk_acceptq_removed(&rx->sk);
 586         rxrpc_see_call(call);
 587
 588         write_lock_bh(&call->state_lock);
 589         switch (call->state) {
 590         case RXRPC_CALL_SERVER_ACCEPTING:
 591                 __rxrpc_set_call_completion(call, RXRPC_CALL_SERVER_BUSY,
 592                                             0, ECONNABORTED);
 593                 if (test_and_set_bit(RXRPC_CALL_EV_REJECT_BUSY, &call->events))
 594                         rxrpc_queue_call(call);
 595                 ret = 0;
 596                 break;
 597         case RXRPC_CALL_COMPLETE:
 598                 ret = call->error;
 599                 break;
 600         default:
 601                 BUG();
 602         }
 603
 604         write_unlock_bh(&call->state_lock);
 605         write_unlock(&rx->call_lock);
 606         rxrpc_release_call(rx, call);
 607         _leave(" = %d", ret);
 608         return ret;
 609 }
 610
 611 /**
 612  * rxrpc_kernel_accept_call - Allow a kernel service to accept an incoming call
 613  * @sock: The socket on which the impending call is waiting
 614  * @user_call_ID: The tag to attach to the call
 615  * @notify_rx: Where to send notifications instead of socket queue
 616  *
 617  * Allow a kernel service to accept an incoming call, assuming the incoming
 618  * call is still valid.  The caller should immediately trigger their own
 619  * notification as there must be data waiting.
 620  */
 621 struct rxrpc_call *rxrpc_kernel_accept_call(struct socket *sock,
 622                                             unsigned long user_call_ID,
 623                                             rxrpc_notify_rx_t notify_rx)
 624 {
 625         struct rxrpc_call *call;
 626
 627         _enter(",%lx", user_call_ID);
 628         call = rxrpc_accept_call(rxrpc_sk(sock->sk), user_call_ID, notify_rx);
 629         _leave(" = %p", call);
 630         return call;
 631 }
 632 EXPORT_SYMBOL(rxrpc_kernel_accept_call);
 633
 634 /**
 635  * rxrpc_kernel_reject_call - Allow a kernel service to reject an incoming call
 636  * @sock: The socket on which the impending call is waiting
 637  *
 638  * Allow a kernel service to reject an incoming call with a BUSY message,
 639  * assuming the incoming call is still valid.
 640  */
 641 int rxrpc_kernel_reject_call(struct socket *sock)
 642 {
 643         int ret;
 644
 645         _enter("");
 646         ret = rxrpc_reject_call(rxrpc_sk(sock->sk));
 647         _leave(" = %d", ret);
 648         return ret;
 649 }
 650 EXPORT_SYMBOL(rxrpc_kernel_reject_call);
 651
 652 /*
 653  * rxrpc_kernel_charge_accept - Charge up socket with preallocated calls
 654  * @sock: The socket on which to preallocate
 655  * @notify_rx: Event notification function for the call
 656  * @user_attach_call: Func to attach call to user_call_ID
 657  * @user_call_ID: The tag to attach to the preallocated call
 658  * @gfp: The allocation conditions.
 659  *
 660  * Charge up the socket with preallocated calls, each with a user ID.  A
 661  * function should be provided to effect the attachment from the user's side.
 662  * The user is given a ref to hold on the call.
 663  *
 664  * Note that the call may be come connected before this function returns.
 665  */
 666 int rxrpc_kernel_charge_accept(struct socket *sock,
 667                                rxrpc_notify_rx_t notify_rx,
 668                                rxrpc_user_attach_call_t user_attach_call,
 669                                unsigned long user_call_ID, gfp_t gfp)
 670 {
 671         struct rxrpc_sock *rx = rxrpc_sk(sock->sk);
 672         struct rxrpc_backlog *b = rx->backlog;
 673
 674         if (sock->sk->sk_state == RXRPC_CLOSE)
 675                 return -ESHUTDOWN;
 676
 677         return rxrpc_service_prealloc_one(rx, b, notify_rx,
 678                                           user_attach_call, user_call_ID,
 679                                           gfp);
 680 }
 681 EXPORT_SYMBOL(rxrpc_kernel_charge_accept);