xref: /linux/net/mptcp/token.c (revision 5d7f3375cd574fc83f0cd30839b21455c0e79ae2) 
1 // SPDX-License-Identifier: GPL-2.0
2 /* Multipath TCP token management
3  * Copyright (c) 2017 - 2019, Intel Corporation.
4  *
5  * Note: This code is based on mptcp_ctrl.c from multipath-tcp.org,
6  *       authored by:
7  *
8  *       Sébastien Barré <sebastien.barre@uclouvain.be>
9  *       Christoph Paasch <christoph.paasch@uclouvain.be>
10  *       Jaakko Korkeaniemi <jaakko.korkeaniemi@aalto.fi>
11  *       Gregory Detal <gregory.detal@uclouvain.be>
12  *       Fabien Duchêne <fabien.duchene@uclouvain.be>
13  *       Andreas Seelinger <Andreas.Seelinger@rwth-aachen.de>
14  *       Lavkesh Lahngir <lavkesh51@gmail.com>
15  *       Andreas Ripke <ripke@neclab.eu>
16  *       Vlad Dogaru <vlad.dogaru@intel.com>
17  *       Octavian Purdila <octavian.purdila@intel.com>
18  *       John Ronan <jronan@tssg.org>
19  *       Catalin Nicutar <catalin.nicutar@gmail.com>
20  *       Brandon Heller <brandonh@stanford.edu>
21  */
22 
23 #define pr_fmt(fmt) "MPTCP: " fmt
24 
25 #include <linux/kernel.h>
26 #include <linux/module.h>
27 #include <linux/memblock.h>
28 #include <linux/ip.h>
29 #include <linux/tcp.h>
30 #include <net/sock.h>
31 #include <net/inet_common.h>
32 #include <net/protocol.h>
33 #include <net/mptcp.h>
34 #include "protocol.h"
35 
36 #define TOKEN_MAX_CHAIN_LEN	4
37 
38 struct token_bucket {
39 	spinlock_t		lock;
40 	int			chain_len;
41 	struct hlist_nulls_head	req_chain;
42 	struct hlist_nulls_head	msk_chain;
43 };
44 
45 static struct token_bucket *token_hash __read_mostly;
46 static unsigned int token_mask __read_mostly;
47 
48 static struct token_bucket *token_bucket(u32 token)
49 {
50 	return &token_hash[token & token_mask];
51 }
52 
53 /* called with bucket lock held */
54 static struct mptcp_subflow_request_sock *
55 __token_lookup_req(struct token_bucket *t, u32 token)
56 {
57 	struct mptcp_subflow_request_sock *req;
58 	struct hlist_nulls_node *pos;
59 
60 	hlist_nulls_for_each_entry_rcu(req, pos, &t->req_chain, token_node)
61 		if (req->token == token)
62 			return req;
63 	return NULL;
64 }
65 
66 /* called with bucket lock held */
67 static struct mptcp_sock *
68 __token_lookup_msk(struct token_bucket *t, u32 token)
69 {
70 	struct hlist_nulls_node *pos;
71 	struct sock *sk;
72 
73 	sk_nulls_for_each_rcu(sk, pos, &t->msk_chain)
74 		if (mptcp_sk(sk)->token == token)
75 			return mptcp_sk(sk);
76 	return NULL;
77 }
78 
79 static bool __token_bucket_busy(struct token_bucket *t, u32 token)
80 {
81 	return !token || t->chain_len >= TOKEN_MAX_CHAIN_LEN ||
82 	       __token_lookup_req(t, token) || __token_lookup_msk(t, token);
83 }
84 
85 static void mptcp_crypto_key_gen_sha(u64 *key, u32 *token, u64 *idsn)
86 {
87 	/* we might consider a faster version that computes the key as a
88 	 * hash of some information available in the MPTCP socket. Use
89 	 * random data at the moment, as it's probably the safest option
90 	 * in case multiple sockets are opened in different namespaces at
91 	 * the same time.
92 	 */
93 	get_random_bytes(key, sizeof(u64));
94 	mptcp_crypto_key_sha(*key, token, idsn);
95 }
96 
97 /**
98  * mptcp_token_new_request - create new key/idsn/token for subflow_request
99  * @req: the request socket
100  *
101  * This function is called when a new mptcp connection is coming in.
102  *
103  * It creates a unique token to identify the new mptcp connection,
104  * a secret local key and the initial data sequence number (idsn).
105  *
106  * Return: 0 on success.
107  */
108 int mptcp_token_new_request(struct request_sock *req)
109 {
110 	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
111 	struct token_bucket *bucket;
112 	u32 token;
113 
114 	mptcp_crypto_key_sha(subflow_req->local_key,
115 			     &subflow_req->token,
116 			     &subflow_req->idsn);
117 	pr_debug("req=%p local_key=%llu, token=%u, idsn=%llu\n",
118 		 req, subflow_req->local_key, subflow_req->token,
119 		 subflow_req->idsn);
120 
121 	token = subflow_req->token;
122 	bucket = token_bucket(token);
123 	spin_lock_bh(&bucket->lock);
124 	if (__token_bucket_busy(bucket, token)) {
125 		spin_unlock_bh(&bucket->lock);
126 		return -EBUSY;
127 	}
128 
129 	hlist_nulls_add_head_rcu(&subflow_req->token_node, &bucket->req_chain);
130 	bucket->chain_len++;
131 	spin_unlock_bh(&bucket->lock);
132 	return 0;
133 }
134 
135 /**
136  * mptcp_token_new_connect - create new key/idsn/token for subflow
137  * @ssk: the socket that will initiate a connection
138  *
139  * This function is called when a new outgoing mptcp connection is
140  * initiated.
141  *
142  * It creates a unique token to identify the new mptcp connection,
143  * a secret local key and the initial data sequence number (idsn).
144  *
145  * On success, the mptcp connection can be found again using
146  * the computed token at a later time, this is needed to process
147  * join requests.
148  *
149  * Return: 0 on success.
150  */
151 int mptcp_token_new_connect(struct sock *ssk)
152 {
153 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
154 	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
155 	int retries = MPTCP_TOKEN_MAX_RETRIES;
156 	struct sock *sk = subflow->conn;
157 	struct token_bucket *bucket;
158 
159 again:
160 	mptcp_crypto_key_gen_sha(&subflow->local_key, &subflow->token,
161 				 &subflow->idsn);
162 
163 	bucket = token_bucket(subflow->token);
164 	spin_lock_bh(&bucket->lock);
165 	if (__token_bucket_busy(bucket, subflow->token)) {
166 		spin_unlock_bh(&bucket->lock);
167 		if (!--retries)
168 			return -EBUSY;
169 		goto again;
170 	}
171 
172 	pr_debug("ssk=%p, local_key=%llu, token=%u, idsn=%llu\n",
173 		 ssk, subflow->local_key, subflow->token, subflow->idsn);
174 
175 	WRITE_ONCE(msk->token, subflow->token);
176 	__sk_nulls_add_node_rcu((struct sock *)msk, &bucket->msk_chain);
177 	bucket->chain_len++;
178 	spin_unlock_bh(&bucket->lock);
179 	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
180 	return 0;
181 }
182 
183 /**
184  * mptcp_token_move_request - move request token ownership to a clone
185  * @req: original request socket
186  * @new_req: cloned request socket
187  *
188  * Move the token hash entry from the original request to its clone.
189  */
190 void mptcp_token_move_request(struct request_sock *req,
191 			      struct request_sock *new_req)
192 {
193 	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
194 	struct mptcp_subflow_request_sock *new_subflow_req;
195 	struct mptcp_subflow_request_sock *pos;
196 	struct token_bucket *bucket;
197 
198 	new_subflow_req = mptcp_subflow_rsk(new_req);
199 
200 	if (hlist_nulls_unhashed_lockless(&subflow_req->token_node)) {
201 		mptcp_token_init_request(new_req);
202 		return;
203 	}
204 
205 	bucket = token_bucket(subflow_req->token);
206 	spin_lock_bh(&bucket->lock);
207 	if (hlist_nulls_unhashed(&subflow_req->token_node)) {
208 		mptcp_token_init_request(new_req);
209 	} else {
210 		pos = __token_lookup_req(bucket, subflow_req->token);
211 		if (pos == subflow_req)
212 			hlist_nulls_replace_init_rcu(&subflow_req->token_node,
213 						     &new_subflow_req->token_node);
214 		else
215 			mptcp_token_init_request(new_req);
216 	}
217 	spin_unlock_bh(&bucket->lock);
218 }
219 
220 /**
221  * mptcp_token_accept - replace a req sk with full sock in token hash
222  * @req: the request socket to be removed
223  * @msk: the just cloned socket linked to the new connection
224  *
225  * Called when a SYN packet creates a new logical connection, i.e.
226  * is not a join request.
227  *
228  * Return: true on success.
229  */
230 bool mptcp_token_accept(struct mptcp_subflow_request_sock *req,
231 			struct mptcp_sock *msk)
232 {
233 	struct mptcp_subflow_request_sock *pos;
234 	struct sock *sk = (struct sock *)msk;
235 	struct token_bucket *bucket;
236 	bool ret = false;
237 
238 	bucket = token_bucket(req->token);
239 	spin_lock_bh(&bucket->lock);
240 	if (hlist_nulls_unhashed(&req->token_node))
241 		goto unlock;
242 
243 	pos = __token_lookup_req(bucket, req->token);
244 	if (pos != req)
245 		goto unlock;
246 
247 	hlist_nulls_del_init_rcu(&req->token_node);
248 	__sk_nulls_add_node_rcu((struct sock *)msk, &bucket->msk_chain);
249 	ret = true;
250 
251 unlock:
252 	spin_unlock_bh(&bucket->lock);
253 	if (ret)
254 		sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
255 
256 	return ret;
257 }
258 
259 bool mptcp_token_exists(u32 token)
260 {
261 	struct hlist_nulls_node *pos;
262 	struct token_bucket *bucket;
263 	struct mptcp_sock *msk;
264 	struct sock *sk;
265 
266 	rcu_read_lock();
267 	bucket = token_bucket(token);
268 
269 again:
270 	sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
271 		msk = mptcp_sk(sk);
272 		if (READ_ONCE(msk->token) == token)
273 			goto found;
274 	}
275 	if (get_nulls_value(pos) != (token & token_mask))
276 		goto again;
277 
278 	rcu_read_unlock();
279 	return false;
280 found:
281 	rcu_read_unlock();
282 	return true;
283 }
284 
285 /**
286  * mptcp_token_get_sock - retrieve mptcp connection sock using its token
287  * @net: restrict to this namespace
288  * @token: token of the mptcp connection to retrieve
289  *
290  * This function returns the mptcp connection structure with the given token.
291  * A reference count on the mptcp socket returned is taken.
292  *
293  * Return: NULL if no connection with the given token value exists.
294  */
295 struct mptcp_sock *mptcp_token_get_sock(struct net *net, u32 token)
296 {
297 	struct hlist_nulls_node *pos;
298 	struct token_bucket *bucket;
299 	struct mptcp_sock *msk;
300 	struct sock *sk;
301 
302 	rcu_read_lock();
303 	bucket = token_bucket(token);
304 
305 again:
306 	sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
307 		msk = mptcp_sk(sk);
308 		if (READ_ONCE(msk->token) != token ||
309 		    !net_eq(sock_net(sk), net))
310 			continue;
311 
312 		if (!refcount_inc_not_zero(&sk->sk_refcnt))
313 			goto not_found;
314 
315 		if (READ_ONCE(msk->token) != token ||
316 		    !net_eq(sock_net(sk), net)) {
317 			sock_put(sk);
318 			goto again;
319 		}
320 		goto found;
321 	}
322 	if (get_nulls_value(pos) != (token & token_mask))
323 		goto again;
324 
325 not_found:
326 	msk = NULL;
327 
328 found:
329 	rcu_read_unlock();
330 	return msk;
331 }
332 EXPORT_SYMBOL_GPL(mptcp_token_get_sock);
333 
334 /**
335  * mptcp_token_iter_next - iterate over the token container from given pos
336  * @net: namespace to be iterated
337  * @s_slot: start slot number
338  * @s_num: start number inside the given lock
339  *
340  * Description:
341  *   On successful iteration, the iterator is moved to the next position and a
342  *   reference to the returned socket is acquired.
343  *
344  * Return:
345  *   The first mptcp connection structure found inside the token container
346  *   starting from the specified position, or NULL.
347  */
348 struct mptcp_sock *mptcp_token_iter_next(const struct net *net, long *s_slot,
349 					 long *s_num)
350 {
351 	struct mptcp_sock *ret = NULL;
352 	struct hlist_nulls_node *pos;
353 	int slot, num = 0;
354 
355 	for (slot = *s_slot; slot <= token_mask; *s_num = 0, slot++) {
356 		struct token_bucket *bucket = &token_hash[slot];
357 		struct sock *sk;
358 
359 		num = 0;
360 
361 		if (hlist_nulls_empty(&bucket->msk_chain))
362 			continue;
363 
364 		rcu_read_lock();
365 		sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
366 			++num;
367 			if (!net_eq(sock_net(sk), net))
368 				continue;
369 
370 			if (num <= *s_num)
371 				continue;
372 
373 			if (!refcount_inc_not_zero(&sk->sk_refcnt))
374 				continue;
375 
376 			if (!net_eq(sock_net(sk), net)) {
377 				sock_put(sk);
378 				continue;
379 			}
380 
381 			ret = mptcp_sk(sk);
382 			rcu_read_unlock();
383 			goto out;
384 		}
385 		rcu_read_unlock();
386 	}
387 
388 out:
389 	*s_slot = slot;
390 	*s_num = num;
391 	return ret;
392 }
393 EXPORT_SYMBOL_GPL(mptcp_token_iter_next);
394 
395 /**
396  * mptcp_token_destroy_request - remove mptcp connection/token
397  * @req: mptcp request socket dropping the token
398  *
399  * Remove the token associated to @req.
400  */
401 void mptcp_token_destroy_request(struct request_sock *req)
402 {
403 	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
404 	struct mptcp_subflow_request_sock *pos;
405 	struct token_bucket *bucket;
406 
407 	if (hlist_nulls_unhashed_lockless(&subflow_req->token_node))
408 		return;
409 
410 	bucket = token_bucket(subflow_req->token);
411 	spin_lock_bh(&bucket->lock);
412 	if (hlist_nulls_unhashed(&subflow_req->token_node))
413 		goto unlock;
414 
415 	pos = __token_lookup_req(bucket, subflow_req->token);
416 	if (pos == subflow_req) {
417 		hlist_nulls_del_init_rcu(&pos->token_node);
418 		bucket->chain_len--;
419 	}
420 
421 unlock:
422 	spin_unlock_bh(&bucket->lock);
423 }
424 
425 /**
426  * mptcp_token_destroy - remove mptcp connection/token
427  * @msk: mptcp connection dropping the token
428  *
429  * Remove the token associated to @msk
430  */
431 void mptcp_token_destroy(struct mptcp_sock *msk)
432 {
433 	struct sock *sk = (struct sock *)msk;
434 	struct token_bucket *bucket;
435 	struct mptcp_sock *pos;
436 
437 	if (sk_unhashed((struct sock *)msk))
438 		return;
439 
440 	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
441 	bucket = token_bucket(msk->token);
442 	spin_lock_bh(&bucket->lock);
443 	pos = __token_lookup_msk(bucket, msk->token);
444 	if (!WARN_ON_ONCE(pos != msk)) {
445 		__sk_nulls_del_node_init_rcu((struct sock *)pos);
446 		bucket->chain_len--;
447 	}
448 	spin_unlock_bh(&bucket->lock);
449 	WRITE_ONCE(msk->token, 0);
450 }
451 
452 void __init mptcp_token_init(void)
453 {
454 	int i;
455 
456 	token_hash = alloc_large_system_hash("MPTCP token",
457 					     sizeof(struct token_bucket),
458 					     0,
459 					     20,/* one slot per 1MB of memory */
460 					     HASH_ZERO,
461 					     NULL,
462 					     &token_mask,
463 					     0,
464 					     64 * 1024);
465 	for (i = 0; i < token_mask + 1; ++i) {
466 		INIT_HLIST_NULLS_HEAD(&token_hash[i].req_chain, i);
467 		INIT_HLIST_NULLS_HEAD(&token_hash[i].msk_chain, i);
468 		spin_lock_init(&token_hash[i].lock);
469 	}
470 }
471 
472 #if IS_MODULE(CONFIG_MPTCP_KUNIT_TEST)
473 EXPORT_SYMBOL_GPL(mptcp_token_new_request);
474 EXPORT_SYMBOL_GPL(mptcp_token_new_connect);
475 EXPORT_SYMBOL_GPL(mptcp_token_accept);
476 EXPORT_SYMBOL_GPL(mptcp_token_destroy_request);
477 EXPORT_SYMBOL_GPL(mptcp_token_destroy);
478 #endif
479