xref: /linux/net/mptcp/token.c (revision 067012974c8ae31a8886046df082aeba93592972) 
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_RETRIES	4
37 #define TOKEN_MAX_CHAIN_LEN	4
38 
39 struct token_bucket {
40 	spinlock_t		lock;
41 	int			chain_len;
42 	struct hlist_nulls_head	req_chain;
43 	struct hlist_nulls_head	msk_chain;
44 };
45 
46 static struct token_bucket *token_hash __read_mostly;
47 static unsigned int token_mask __read_mostly;
48 
49 static struct token_bucket *token_bucket(u32 token)
50 {
51 	return &token_hash[token & token_mask];
52 }
53 
54 /* called with bucket lock held */
55 static struct mptcp_subflow_request_sock *
56 __token_lookup_req(struct token_bucket *t, u32 token)
57 {
58 	struct mptcp_subflow_request_sock *req;
59 	struct hlist_nulls_node *pos;
60 
61 	hlist_nulls_for_each_entry_rcu(req, pos, &t->req_chain, token_node)
62 		if (req->token == token)
63 			return req;
64 	return NULL;
65 }
66 
67 /* called with bucket lock held */
68 static struct mptcp_sock *
69 __token_lookup_msk(struct token_bucket *t, u32 token)
70 {
71 	struct hlist_nulls_node *pos;
72 	struct sock *sk;
73 
74 	sk_nulls_for_each_rcu(sk, pos, &t->msk_chain)
75 		if (mptcp_sk(sk)->token == token)
76 			return mptcp_sk(sk);
77 	return NULL;
78 }
79 
80 static bool __token_bucket_busy(struct token_bucket *t, u32 token)
81 {
82 	return !token || t->chain_len >= TOKEN_MAX_CHAIN_LEN ||
83 	       __token_lookup_req(t, token) || __token_lookup_msk(t, token);
84 }
85 
86 static void mptcp_crypto_key_gen_sha(u64 *key, u32 *token, u64 *idsn)
87 {
88 	/* we might consider a faster version that computes the key as a
89 	 * hash of some information available in the MPTCP socket. Use
90 	 * random data at the moment, as it's probably the safest option
91 	 * in case multiple sockets are opened in different namespaces at
92 	 * the same time.
93 	 */
94 	get_random_bytes(key, sizeof(u64));
95 	mptcp_crypto_key_sha(*key, token, idsn);
96 }
97 
98 /**
99  * mptcp_token_new_request - create new key/idsn/token for subflow_request
100  * @req: the request socket
101  *
102  * This function is called when a new mptcp connection is coming in.
103  *
104  * It creates a unique token to identify the new mptcp connection,
105  * a secret local key and the initial data sequence number (idsn).
106  *
107  * Returns 0 on success.
108  */
109 int mptcp_token_new_request(struct request_sock *req)
110 {
111 	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
112 	struct token_bucket *bucket;
113 	u32 token;
114 
115 	mptcp_crypto_key_sha(subflow_req->local_key,
116 			     &subflow_req->token,
117 			     &subflow_req->idsn);
118 	pr_debug("req=%p local_key=%llu, token=%u, idsn=%llu\n",
119 		 req, subflow_req->local_key, subflow_req->token,
120 		 subflow_req->idsn);
121 
122 	token = subflow_req->token;
123 	bucket = token_bucket(token);
124 	spin_lock_bh(&bucket->lock);
125 	if (__token_bucket_busy(bucket, token)) {
126 		spin_unlock_bh(&bucket->lock);
127 		return -EBUSY;
128 	}
129 
130 	hlist_nulls_add_head_rcu(&subflow_req->token_node, &bucket->req_chain);
131 	bucket->chain_len++;
132 	spin_unlock_bh(&bucket->lock);
133 	return 0;
134 }
135 
136 /**
137  * mptcp_token_new_connect - create new key/idsn/token for subflow
138  * @sk: the socket that will initiate a connection
139  *
140  * This function is called when a new outgoing mptcp connection is
141  * initiated.
142  *
143  * It creates a unique token to identify the new mptcp connection,
144  * a secret local key and the initial data sequence number (idsn).
145  *
146  * On success, the mptcp connection can be found again using
147  * the computed token at a later time, this is needed to process
148  * join requests.
149  *
150  * returns 0 on success.
151  */
152 int mptcp_token_new_connect(struct sock *sk)
153 {
154 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
155 	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
156 	int retries = TOKEN_MAX_RETRIES;
157 	struct token_bucket *bucket;
158 
159 	pr_debug("ssk=%p, local_key=%llu, token=%u, idsn=%llu\n",
160 		 sk, subflow->local_key, subflow->token, subflow->idsn);
161 
162 again:
163 	mptcp_crypto_key_gen_sha(&subflow->local_key, &subflow->token,
164 				 &subflow->idsn);
165 
166 	bucket = token_bucket(subflow->token);
167 	spin_lock_bh(&bucket->lock);
168 	if (__token_bucket_busy(bucket, subflow->token)) {
169 		spin_unlock_bh(&bucket->lock);
170 		if (!--retries)
171 			return -EBUSY;
172 		goto again;
173 	}
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 	return 0;
180 }
181 
182 /**
183  * mptcp_token_accept - replace a req sk with full sock in token hash
184  * @req: the request socket to be removed
185  * @msk: the just cloned socket linked to the new connection
186  *
187  * Called when a SYN packet creates a new logical connection, i.e.
188  * is not a join request.
189  */
190 void mptcp_token_accept(struct mptcp_subflow_request_sock *req,
191 			struct mptcp_sock *msk)
192 {
193 	struct mptcp_subflow_request_sock *pos;
194 	struct token_bucket *bucket;
195 
196 	bucket = token_bucket(req->token);
197 	spin_lock_bh(&bucket->lock);
198 
199 	/* pedantic lookup check for the moved token */
200 	pos = __token_lookup_req(bucket, req->token);
201 	if (!WARN_ON_ONCE(pos != req))
202 		hlist_nulls_del_init_rcu(&req->token_node);
203 	__sk_nulls_add_node_rcu((struct sock *)msk, &bucket->msk_chain);
204 	spin_unlock_bh(&bucket->lock);
205 }
206 
207 bool mptcp_token_exists(u32 token)
208 {
209 	struct hlist_nulls_node *pos;
210 	struct token_bucket *bucket;
211 	struct mptcp_sock *msk;
212 	struct sock *sk;
213 
214 	rcu_read_lock();
215 	bucket = token_bucket(token);
216 
217 again:
218 	sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
219 		msk = mptcp_sk(sk);
220 		if (READ_ONCE(msk->token) == token)
221 			goto found;
222 	}
223 	if (get_nulls_value(pos) != (token & token_mask))
224 		goto again;
225 
226 	rcu_read_unlock();
227 	return false;
228 found:
229 	rcu_read_unlock();
230 	return true;
231 }
232 
233 /**
234  * mptcp_token_get_sock - retrieve mptcp connection sock using its token
235  * @token: token of the mptcp connection to retrieve
236  *
237  * This function returns the mptcp connection structure with the given token.
238  * A reference count on the mptcp socket returned is taken.
239  *
240  * returns NULL if no connection with the given token value exists.
241  */
242 struct mptcp_sock *mptcp_token_get_sock(u32 token)
243 {
244 	struct hlist_nulls_node *pos;
245 	struct token_bucket *bucket;
246 	struct mptcp_sock *msk;
247 	struct sock *sk;
248 
249 	rcu_read_lock();
250 	bucket = token_bucket(token);
251 
252 again:
253 	sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
254 		msk = mptcp_sk(sk);
255 		if (READ_ONCE(msk->token) != token)
256 			continue;
257 		if (!refcount_inc_not_zero(&sk->sk_refcnt))
258 			goto not_found;
259 		if (READ_ONCE(msk->token) != token) {
260 			sock_put(sk);
261 			goto again;
262 		}
263 		goto found;
264 	}
265 	if (get_nulls_value(pos) != (token & token_mask))
266 		goto again;
267 
268 not_found:
269 	msk = NULL;
270 
271 found:
272 	rcu_read_unlock();
273 	return msk;
274 }
275 EXPORT_SYMBOL_GPL(mptcp_token_get_sock);
276 
277 /**
278  * mptcp_token_iter_next - iterate over the token container from given pos
279  * @net: namespace to be iterated
280  * @s_slot: start slot number
281  * @s_num: start number inside the given lock
282  *
283  * This function returns the first mptcp connection structure found inside the
284  * token container starting from the specified position, or NULL.
285  *
286  * On successful iteration, the iterator is move to the next position and the
287  * the acquires a reference to the returned socket.
288  */
289 struct mptcp_sock *mptcp_token_iter_next(const struct net *net, long *s_slot,
290 					 long *s_num)
291 {
292 	struct mptcp_sock *ret = NULL;
293 	struct hlist_nulls_node *pos;
294 	int slot, num = 0;
295 
296 	for (slot = *s_slot; slot <= token_mask; *s_num = 0, slot++) {
297 		struct token_bucket *bucket = &token_hash[slot];
298 		struct sock *sk;
299 
300 		num = 0;
301 
302 		if (hlist_nulls_empty(&bucket->msk_chain))
303 			continue;
304 
305 		rcu_read_lock();
306 		sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
307 			++num;
308 			if (!net_eq(sock_net(sk), net))
309 				continue;
310 
311 			if (num <= *s_num)
312 				continue;
313 
314 			if (!refcount_inc_not_zero(&sk->sk_refcnt))
315 				continue;
316 
317 			if (!net_eq(sock_net(sk), net)) {
318 				sock_put(sk);
319 				continue;
320 			}
321 
322 			ret = mptcp_sk(sk);
323 			rcu_read_unlock();
324 			goto out;
325 		}
326 		rcu_read_unlock();
327 	}
328 
329 out:
330 	*s_slot = slot;
331 	*s_num = num;
332 	return ret;
333 }
334 EXPORT_SYMBOL_GPL(mptcp_token_iter_next);
335 
336 /**
337  * mptcp_token_destroy_request - remove mptcp connection/token
338  * @req: mptcp request socket dropping the token
339  *
340  * Remove the token associated to @req.
341  */
342 void mptcp_token_destroy_request(struct request_sock *req)
343 {
344 	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
345 	struct mptcp_subflow_request_sock *pos;
346 	struct token_bucket *bucket;
347 
348 	if (hlist_nulls_unhashed(&subflow_req->token_node))
349 		return;
350 
351 	bucket = token_bucket(subflow_req->token);
352 	spin_lock_bh(&bucket->lock);
353 	pos = __token_lookup_req(bucket, subflow_req->token);
354 	if (!WARN_ON_ONCE(pos != subflow_req)) {
355 		hlist_nulls_del_init_rcu(&pos->token_node);
356 		bucket->chain_len--;
357 	}
358 	spin_unlock_bh(&bucket->lock);
359 }
360 
361 /**
362  * mptcp_token_destroy - remove mptcp connection/token
363  * @msk: mptcp connection dropping the token
364  *
365  * Remove the token associated to @msk
366  */
367 void mptcp_token_destroy(struct mptcp_sock *msk)
368 {
369 	struct token_bucket *bucket;
370 	struct mptcp_sock *pos;
371 
372 	if (sk_unhashed((struct sock *)msk))
373 		return;
374 
375 	bucket = token_bucket(msk->token);
376 	spin_lock_bh(&bucket->lock);
377 	pos = __token_lookup_msk(bucket, msk->token);
378 	if (!WARN_ON_ONCE(pos != msk)) {
379 		__sk_nulls_del_node_init_rcu((struct sock *)pos);
380 		bucket->chain_len--;
381 	}
382 	spin_unlock_bh(&bucket->lock);
383 }
384 
385 void __init mptcp_token_init(void)
386 {
387 	int i;
388 
389 	token_hash = alloc_large_system_hash("MPTCP token",
390 					     sizeof(struct token_bucket),
391 					     0,
392 					     20,/* one slot per 1MB of memory */
393 					     HASH_ZERO,
394 					     NULL,
395 					     &token_mask,
396 					     0,
397 					     64 * 1024);
398 	for (i = 0; i < token_mask + 1; ++i) {
399 		INIT_HLIST_NULLS_HEAD(&token_hash[i].req_chain, i);
400 		INIT_HLIST_NULLS_HEAD(&token_hash[i].msk_chain, i);
401 		spin_lock_init(&token_hash[i].lock);
402 	}
403 }
404 
405 #if IS_MODULE(CONFIG_MPTCP_KUNIT_TESTS)
406 EXPORT_SYMBOL_GPL(mptcp_token_new_request);
407 EXPORT_SYMBOL_GPL(mptcp_token_new_connect);
408 EXPORT_SYMBOL_GPL(mptcp_token_accept);
409 EXPORT_SYMBOL_GPL(mptcp_token_destroy_request);
410 EXPORT_SYMBOL_GPL(mptcp_token_destroy);
411 #endif
412