net/rxrpc/ar-transport.c

   1 /* RxRPC point-to-point transport session management
   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 #include <linux/module.h>
  13 #include <linux/net.h>
  14 #include <linux/skbuff.h>
  15 #include <linux/slab.h>
  16 #include <net/sock.h>
  17 #include <net/af_rxrpc.h>
  18 #include "ar-internal.h"
  19
  20 /*
  21  * Time after last use at which transport record is cleaned up.
  22  */
  23 unsigned rxrpc_transport_expiry = 3600 * 24;
  24
  25 static void rxrpc_transport_reaper(struct work_struct *work);
  26
  27 static LIST_HEAD(rxrpc_transports);
  28 static DEFINE_RWLOCK(rxrpc_transport_lock);
  29 static DECLARE_DELAYED_WORK(rxrpc_transport_reap, rxrpc_transport_reaper);
  30
  31 /*
  32  * allocate a new transport session manager
  33  */
  34 static struct rxrpc_transport *rxrpc_alloc_transport(struct rxrpc_local *local,
  35                                                      struct rxrpc_peer *peer,
  36                                                      gfp_t gfp)
  37 {
  38         struct rxrpc_transport *trans;
  39
  40         _enter("");
  41
  42         trans = kzalloc(sizeof(struct rxrpc_transport), gfp);
  43         if (trans) {
  44                 trans->local = local;
  45                 trans->peer = peer;
  46                 INIT_LIST_HEAD(&trans->link);
  47                 trans->bundles = RB_ROOT;
  48                 trans->client_conns = RB_ROOT;
  49                 trans->server_conns = RB_ROOT;
  50                 skb_queue_head_init(&trans->error_queue);
  51                 spin_lock_init(&trans->client_lock);
  52                 rwlock_init(&trans->conn_lock);
  53                 atomic_set(&trans->usage, 1);
  54                 trans->debug_id = atomic_inc_return(&rxrpc_debug_id);
  55
  56                 if (peer->srx.transport.family == AF_INET) {
  57                         switch (peer->srx.transport_type) {
  58                         case SOCK_DGRAM:
  59                                 INIT_WORK(&trans->error_handler,
  60                                           rxrpc_UDP_error_handler);
  61                                 break;
  62                         default:
  63                                 BUG();
  64                                 break;
  65                         }
  66                 } else {
  67                         BUG();
  68                 }
  69         }
  70
  71         _leave(" = %p", trans);
  72         return trans;
  73 }
  74
  75 /*
  76  * obtain a transport session for the nominated endpoints
  77  */
  78 struct rxrpc_transport *rxrpc_get_transport(struct rxrpc_local *local,
  79                                             struct rxrpc_peer *peer,
  80                                             gfp_t gfp)
  81 {
  82         struct rxrpc_transport *trans, *candidate;
  83         const char *new = "old";
  84         int usage;
  85
  86         _enter("{%pI4+%hu},{%pI4+%hu},",
  87                &local->srx.transport.sin.sin_addr,
  88                ntohs(local->srx.transport.sin.sin_port),
  89                &peer->srx.transport.sin.sin_addr,
  90                ntohs(peer->srx.transport.sin.sin_port));
  91
  92         /* search the transport list first */
  93         read_lock_bh(&rxrpc_transport_lock);
  94         list_for_each_entry(trans, &rxrpc_transports, link) {
  95                 if (trans->local == local && trans->peer == peer)
  96                         goto found_extant_transport;
  97         }
  98         read_unlock_bh(&rxrpc_transport_lock);
  99
 100         /* not yet present - create a candidate for a new record and then
 101          * redo the search */
 102         candidate = rxrpc_alloc_transport(local, peer, gfp);
 103         if (!candidate) {
 104                 _leave(" = -ENOMEM");
 105                 return ERR_PTR(-ENOMEM);
 106         }
 107
 108         write_lock_bh(&rxrpc_transport_lock);
 109
 110         list_for_each_entry(trans, &rxrpc_transports, link) {
 111                 if (trans->local == local && trans->peer == peer)
 112                         goto found_extant_second;
 113         }
 114
 115         /* we can now add the new candidate to the list */
 116         trans = candidate;
 117         candidate = NULL;
 118         usage = atomic_read(&trans->usage);
 119
 120         rxrpc_get_local(trans->local);
 121         atomic_inc(&trans->peer->usage);
 122         list_add_tail(&trans->link, &rxrpc_transports);
 123         write_unlock_bh(&rxrpc_transport_lock);
 124         new = "new";
 125
 126 success:
 127         _net("TRANSPORT %s %d local %d -> peer %d",
 128              new,
 129              trans->debug_id,
 130              trans->local->debug_id,
 131              trans->peer->debug_id);
 132
 133         _leave(" = %p {u=%d}", trans, usage);
 134         return trans;
 135
 136         /* we found the transport in the list immediately */
 137 found_extant_transport:
 138         usage = atomic_inc_return(&trans->usage);
 139         read_unlock_bh(&rxrpc_transport_lock);
 140         goto success;
 141
 142         /* we found the transport on the second time through the list */
 143 found_extant_second:
 144         usage = atomic_inc_return(&trans->usage);
 145         write_unlock_bh(&rxrpc_transport_lock);
 146         kfree(candidate);
 147         goto success;
 148 }
 149
 150 /*
 151  * find the transport connecting two endpoints
 152  */
 153 struct rxrpc_transport *rxrpc_find_transport(struct rxrpc_local *local,
 154                                              struct rxrpc_peer *peer)
 155 {
 156         struct rxrpc_transport *trans;
 157
 158         _enter("{%pI4+%hu},{%pI4+%hu},",
 159                &local->srx.transport.sin.sin_addr,
 160                ntohs(local->srx.transport.sin.sin_port),
 161                &peer->srx.transport.sin.sin_addr,
 162                ntohs(peer->srx.transport.sin.sin_port));
 163
 164         /* search the transport list */
 165         read_lock_bh(&rxrpc_transport_lock);
 166
 167         list_for_each_entry(trans, &rxrpc_transports, link) {
 168                 if (trans->local == local && trans->peer == peer)
 169                         goto found_extant_transport;
 170         }
 171
 172         read_unlock_bh(&rxrpc_transport_lock);
 173         _leave(" = NULL");
 174         return NULL;
 175
 176 found_extant_transport:
 177         atomic_inc(&trans->usage);
 178         read_unlock_bh(&rxrpc_transport_lock);
 179         _leave(" = %p", trans);
 180         return trans;
 181 }
 182
 183 /*
 184  * release a transport session
 185  */
 186 void rxrpc_put_transport(struct rxrpc_transport *trans)
 187 {
 188         _enter("%p{u=%d}", trans, atomic_read(&trans->usage));
 189
 190         ASSERTCMP(atomic_read(&trans->usage), >, 0);
 191
 192         trans->put_time = get_seconds();
 193         if (unlikely(atomic_dec_and_test(&trans->usage))) {
 194                 _debug("zombie");
 195                 /* let the reaper determine the timeout to avoid a race with
 196                  * overextending the timeout if the reaper is running at the
 197                  * same time */
 198                 rxrpc_queue_delayed_work(&rxrpc_transport_reap, 0);
 199         }
 200         _leave("");
 201 }
 202
 203 /*
 204  * clean up a transport session
 205  */
 206 static void rxrpc_cleanup_transport(struct rxrpc_transport *trans)
 207 {
 208         _net("DESTROY TRANS %d", trans->debug_id);
 209
 210         rxrpc_purge_queue(&trans->error_queue);
 211
 212         rxrpc_put_local(trans->local);
 213         rxrpc_put_peer(trans->peer);
 214         kfree(trans);
 215 }
 216
 217 /*
 218  * reap dead transports that have passed their expiry date
 219  */
 220 static void rxrpc_transport_reaper(struct work_struct *work)
 221 {
 222         struct rxrpc_transport *trans, *_p;
 223         unsigned long now, earliest, reap_time;
 224
 225         LIST_HEAD(graveyard);
 226
 227         _enter("");
 228
 229         now = get_seconds();
 230         earliest = ULONG_MAX;
 231
 232         /* extract all the transports that have been dead too long */
 233         write_lock_bh(&rxrpc_transport_lock);
 234         list_for_each_entry_safe(trans, _p, &rxrpc_transports, link) {
 235                 _debug("reap TRANS %d { u=%d t=%ld }",
 236                        trans->debug_id, atomic_read(&trans->usage),
 237                        (long) now - (long) trans->put_time);
 238
 239                 if (likely(atomic_read(&trans->usage) > 0))
 240                         continue;
 241
 242                 reap_time = trans->put_time + rxrpc_transport_expiry;
 243                 if (reap_time <= now)
 244                         list_move_tail(&trans->link, &graveyard);
 245                 else if (reap_time < earliest)
 246                         earliest = reap_time;
 247         }
 248         write_unlock_bh(&rxrpc_transport_lock);
 249
 250         if (earliest != ULONG_MAX) {
 251                 _debug("reschedule reaper %ld", (long) earliest - now);
 252                 ASSERTCMP(earliest, >, now);
 253                 rxrpc_queue_delayed_work(&rxrpc_transport_reap,
 254                                          (earliest - now) * HZ);
 255         }
 256
 257         /* then destroy all those pulled out */
 258         while (!list_empty(&graveyard)) {
 259                 trans = list_entry(graveyard.next, struct rxrpc_transport,
 260                                    link);
 261                 list_del_init(&trans->link);
 262
 263                 ASSERTCMP(atomic_read(&trans->usage), ==, 0);
 264                 rxrpc_cleanup_transport(trans);
 265         }
 266
 267         _leave("");
 268 }
 269
 270 /*
 271  * preemptively destroy all the transport session records rather than waiting
 272  * for them to time out
 273  */
 274 void __exit rxrpc_destroy_all_transports(void)
 275 {
 276         _enter("");
 277
 278         rxrpc_transport_expiry = 0;
 279         cancel_delayed_work(&rxrpc_transport_reap);
 280         rxrpc_queue_delayed_work(&rxrpc_transport_reap, 0);
 281
 282         _leave("");
 283 }