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 */
 23unsigned rxrpc_transport_expiry = 3600 * 24;
 24
 25static void rxrpc_transport_reaper(struct work_struct *work);
 26
 27static LIST_HEAD(rxrpc_transports);
 28static DEFINE_RWLOCK(rxrpc_transport_lock);
 29static DECLARE_DELAYED_WORK(rxrpc_transport_reap, rxrpc_transport_reaper);
 30
 31/*
 32 * allocate a new transport session manager
 33 */
 34static 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 */
 78struct 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
126success:
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 */
137found_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 */
143found_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 */
153struct 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
176found_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 */
186void 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 */
206static 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 */
220static 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 */
274void __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}