1/* RxRPC remote transport endpoint 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/udp.h>
16#include <linux/in.h>
17#include <linux/in6.h>
18#include <linux/icmp.h>
19#include <linux/slab.h>
20#include <net/sock.h>
21#include <net/af_rxrpc.h>
22#include <net/ip.h>
23#include <net/route.h>
24#include "ar-internal.h"
25
26static LIST_HEAD(rxrpc_peers);
27static DEFINE_RWLOCK(rxrpc_peer_lock);
28static DECLARE_WAIT_QUEUE_HEAD(rxrpc_peer_wq);
29
30static void rxrpc_destroy_peer(struct work_struct *work);
31
32/*
33 * assess the MTU size for the network interface through which this peer is
34 * reached
35 */
36static void rxrpc_assess_MTU_size(struct rxrpc_peer *peer)
37{
38	struct rtable *rt;
39	struct flowi fl;
40	int ret;
41
42	peer->if_mtu = 1500;
43
44	memset(&fl, 0, sizeof(fl));
45
46	switch (peer->srx.transport.family) {
47	case AF_INET:
48		fl.oif = 0;
49		fl.proto = IPPROTO_UDP,
50		fl.nl_u.ip4_u.saddr = 0;
51		fl.nl_u.ip4_u.daddr = peer->srx.transport.sin.sin_addr.s_addr;
52		fl.nl_u.ip4_u.tos = 0;
53		/* assume AFS.CM talking to AFS.FS */
54		fl.uli_u.ports.sport = htons(7001);
55		fl.uli_u.ports.dport = htons(7000);
56		break;
57	default:
58		BUG();
59	}
60
61	ret = ip_route_output_key(&init_net, &rt, &fl);
62	if (ret < 0) {
63		_leave(" [route err %d]", ret);
64		return;
65	}
66
67	peer->if_mtu = dst_mtu(&rt->dst);
68	dst_release(&rt->dst);
69
70	_leave(" [if_mtu %u]", peer->if_mtu);
71}
72
73/*
74 * allocate a new peer
75 */
76static struct rxrpc_peer *rxrpc_alloc_peer(struct sockaddr_rxrpc *srx,
77					   gfp_t gfp)
78{
79	struct rxrpc_peer *peer;
80
81	_enter("");
82
83	peer = kzalloc(sizeof(struct rxrpc_peer), gfp);
84	if (peer) {
85		INIT_WORK(&peer->destroyer, &rxrpc_destroy_peer);
86		INIT_LIST_HEAD(&peer->link);
87		INIT_LIST_HEAD(&peer->error_targets);
88		spin_lock_init(&peer->lock);
89		atomic_set(&peer->usage, 1);
90		peer->debug_id = atomic_inc_return(&rxrpc_debug_id);
91		memcpy(&peer->srx, srx, sizeof(*srx));
92
93		rxrpc_assess_MTU_size(peer);
94		peer->mtu = peer->if_mtu;
95
96		if (srx->transport.family == AF_INET) {
97			peer->hdrsize = sizeof(struct iphdr);
98			switch (srx->transport_type) {
99			case SOCK_DGRAM:
100				peer->hdrsize += sizeof(struct udphdr);
101				break;
102			default:
103				BUG();
104				break;
105			}
106		} else {
107			BUG();
108		}
109
110		peer->hdrsize += sizeof(struct rxrpc_header);
111		peer->maxdata = peer->mtu - peer->hdrsize;
112	}
113
114	_leave(" = %p", peer);
115	return peer;
116}
117
118/*
119 * obtain a remote transport endpoint for the specified address
120 */
121struct rxrpc_peer *rxrpc_get_peer(struct sockaddr_rxrpc *srx, gfp_t gfp)
122{
123	struct rxrpc_peer *peer, *candidate;
124	const char *new = "old";
125	int usage;
126
127	_enter("{%d,%d,%pI4+%hu}",
128	       srx->transport_type,
129	       srx->transport_len,
130	       &srx->transport.sin.sin_addr,
131	       ntohs(srx->transport.sin.sin_port));
132
133	/* search the peer list first */
134	read_lock_bh(&rxrpc_peer_lock);
135	list_for_each_entry(peer, &rxrpc_peers, link) {
136		_debug("check PEER %d { u=%d t=%d l=%d }",
137		       peer->debug_id,
138		       atomic_read(&peer->usage),
139		       peer->srx.transport_type,
140		       peer->srx.transport_len);
141
142		if (atomic_read(&peer->usage) > 0 &&
143		    peer->srx.transport_type == srx->transport_type &&
144		    peer->srx.transport_len == srx->transport_len &&
145		    memcmp(&peer->srx.transport,
146			   &srx->transport,
147			   srx->transport_len) == 0)
148			goto found_extant_peer;
149	}
150	read_unlock_bh(&rxrpc_peer_lock);
151
152	/* not yet present - create a candidate for a new record and then
153	 * redo the search */
154	candidate = rxrpc_alloc_peer(srx, gfp);
155	if (!candidate) {
156		_leave(" = -ENOMEM");
157		return ERR_PTR(-ENOMEM);
158	}
159
160	write_lock_bh(&rxrpc_peer_lock);
161
162	list_for_each_entry(peer, &rxrpc_peers, link) {
163		if (atomic_read(&peer->usage) > 0 &&
164		    peer->srx.transport_type == srx->transport_type &&
165		    peer->srx.transport_len == srx->transport_len &&
166		    memcmp(&peer->srx.transport,
167			   &srx->transport,
168			   srx->transport_len) == 0)
169			goto found_extant_second;
170	}
171
172	/* we can now add the new candidate to the list */
173	peer = candidate;
174	candidate = NULL;
175
176	list_add_tail(&peer->link, &rxrpc_peers);
177	write_unlock_bh(&rxrpc_peer_lock);
178	new = "new";
179
180success:
181	_net("PEER %s %d {%d,%u,%pI4+%hu}",
182	     new,
183	     peer->debug_id,
184	     peer->srx.transport_type,
185	     peer->srx.transport.family,
186	     &peer->srx.transport.sin.sin_addr,
187	     ntohs(peer->srx.transport.sin.sin_port));
188
189	_leave(" = %p {u=%d}", peer, atomic_read(&peer->usage));
190	return peer;
191
192	/* we found the peer in the list immediately */
193found_extant_peer:
194	usage = atomic_inc_return(&peer->usage);
195	read_unlock_bh(&rxrpc_peer_lock);
196	goto success;
197
198	/* we found the peer on the second time through the list */
199found_extant_second:
200	usage = atomic_inc_return(&peer->usage);
201	write_unlock_bh(&rxrpc_peer_lock);
202	kfree(candidate);
203	goto success;
204}
205
206/*
207 * find the peer associated with a packet
208 */
209struct rxrpc_peer *rxrpc_find_peer(struct rxrpc_local *local,
210				   __be32 addr, __be16 port)
211{
212	struct rxrpc_peer *peer;
213
214	_enter("");
215
216	/* search the peer list */
217	read_lock_bh(&rxrpc_peer_lock);
218
219	if (local->srx.transport.family == AF_INET &&
220	    local->srx.transport_type == SOCK_DGRAM
221	    ) {
222		list_for_each_entry(peer, &rxrpc_peers, link) {
223			if (atomic_read(&peer->usage) > 0 &&
224			    peer->srx.transport_type == SOCK_DGRAM &&
225			    peer->srx.transport.family == AF_INET &&
226			    peer->srx.transport.sin.sin_port == port &&
227			    peer->srx.transport.sin.sin_addr.s_addr == addr)
228				goto found_UDP_peer;
229		}
230
231		goto new_UDP_peer;
232	}
233
234	read_unlock_bh(&rxrpc_peer_lock);
235	_leave(" = -EAFNOSUPPORT");
236	return ERR_PTR(-EAFNOSUPPORT);
237
238found_UDP_peer:
239	_net("Rx UDP DGRAM from peer %d", peer->debug_id);
240	atomic_inc(&peer->usage);
241	read_unlock_bh(&rxrpc_peer_lock);
242	_leave(" = %p", peer);
243	return peer;
244
245new_UDP_peer:
246	_net("Rx UDP DGRAM from NEW peer %d", peer->debug_id);
247	read_unlock_bh(&rxrpc_peer_lock);
248	_leave(" = -EBUSY [new]");
249	return ERR_PTR(-EBUSY);
250}
251
252/*
253 * release a remote transport endpoint
254 */
255void rxrpc_put_peer(struct rxrpc_peer *peer)
256{
257	_enter("%p{u=%d}", peer, atomic_read(&peer->usage));
258
259	ASSERTCMP(atomic_read(&peer->usage), >, 0);
260
261	if (likely(!atomic_dec_and_test(&peer->usage))) {
262		_leave(" [in use]");
263		return;
264	}
265
266	rxrpc_queue_work(&peer->destroyer);
267	_leave("");
268}
269
270/*
271 * destroy a remote transport endpoint
272 */
273static void rxrpc_destroy_peer(struct work_struct *work)
274{
275	struct rxrpc_peer *peer =
276		container_of(work, struct rxrpc_peer, destroyer);
277
278	_enter("%p{%d}", peer, atomic_read(&peer->usage));
279
280	write_lock_bh(&rxrpc_peer_lock);
281	list_del(&peer->link);
282	write_unlock_bh(&rxrpc_peer_lock);
283
284	_net("DESTROY PEER %d", peer->debug_id);
285	kfree(peer);
286
287	if (list_empty(&rxrpc_peers))
288		wake_up_all(&rxrpc_peer_wq);
289	_leave("");
290}
291
292/*
293 * preemptively destroy all the peer records from a transport endpoint rather
294 * than waiting for them to time out
295 */
296void __exit rxrpc_destroy_all_peers(void)
297{
298	DECLARE_WAITQUEUE(myself,current);
299
300	_enter("");
301
302	/* we simply have to wait for them to go away */
303	if (!list_empty(&rxrpc_peers)) {
304		set_current_state(TASK_UNINTERRUPTIBLE);
305		add_wait_queue(&rxrpc_peer_wq, &myself);
306
307		while (!list_empty(&rxrpc_peers)) {
308			schedule();
309			set_current_state(TASK_UNINTERRUPTIBLE);
310		}
311
312		remove_wait_queue(&rxrpc_peer_wq, &myself);
313		set_current_state(TASK_RUNNING);
314	}
315
316	_leave("");
317}
318