xref: /linux/net/mptcp/token.c (revision 17b121ad0c43342bc894632f6710b894849ca372) 
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  * Returns 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  * @sk: 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  * returns 0 on success.
150  */
151 int mptcp_token_new_connect(struct sock *sk)
152 {
153 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
154 	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
155 	int retries = MPTCP_TOKEN_MAX_RETRIES;
156 	struct token_bucket *bucket;
157 
158 again:
159 	mptcp_crypto_key_gen_sha(&subflow->local_key, &subflow->token,
160 				 &subflow->idsn);
161 
162 	bucket = token_bucket(subflow->token);
163 	spin_lock_bh(&bucket->lock);
164 	if (__token_bucket_busy(bucket, subflow->token)) {
165 		spin_unlock_bh(&bucket->lock);
166 		if (!--retries)
167 			return -EBUSY;
168 		goto again;
169 	}
170 
171 	pr_debug("ssk=%p, local_key=%llu, token=%u, idsn=%llu\n",
172 		 sk, subflow->local_key, subflow->token, subflow->idsn);
173 
174 	WRITE_ONCE(msk->token, subflow->token);
175 	__sk_nulls_add_node_rcu((struct sock *)msk, &bucket->msk_chain);
176 	bucket->chain_len++;
177 	spin_unlock_bh(&bucket->lock);
178 	return 0;
179 }
180 
181 /**
182  * mptcp_token_accept - replace a req sk with full sock in token hash
183  * @req: the request socket to be removed
184  * @msk: the just cloned socket linked to the new connection
185  *
186  * Called when a SYN packet creates a new logical connection, i.e.
187  * is not a join request.
188  */
189 void mptcp_token_accept(struct mptcp_subflow_request_sock *req,
190 			struct mptcp_sock *msk)
191 {
192 	struct mptcp_subflow_request_sock *pos;
193 	struct token_bucket *bucket;
194 
195 	bucket = token_bucket(req->token);
196 	spin_lock_bh(&bucket->lock);
197 
198 	/* pedantic lookup check for the moved token */
199 	pos = __token_lookup_req(bucket, req->token);
200 	if (!WARN_ON_ONCE(pos != req))
201 		hlist_nulls_del_init_rcu(&req->token_node);
202 	__sk_nulls_add_node_rcu((struct sock *)msk, &bucket->msk_chain);
203 	spin_unlock_bh(&bucket->lock);
204 }
205 
206 bool mptcp_token_exists(u32 token)
207 {
208 	struct hlist_nulls_node *pos;
209 	struct token_bucket *bucket;
210 	struct mptcp_sock *msk;
211 	struct sock *sk;
212 
213 	rcu_read_lock();
214 	bucket = token_bucket(token);
215 
216 again:
217 	sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
218 		msk = mptcp_sk(sk);
219 		if (READ_ONCE(msk->token) == token)
220 			goto found;
221 	}
222 	if (get_nulls_value(pos) != (token & token_mask))
223 		goto again;
224 
225 	rcu_read_unlock();
226 	return false;
227 found:
228 	rcu_read_unlock();
229 	return true;
230 }
231 
232 /**
233  * mptcp_token_get_sock - retrieve mptcp connection sock using its token
234  * @token: token of the mptcp connection to retrieve
235  *
236  * This function returns the mptcp connection structure with the given token.
237  * A reference count on the mptcp socket returned is taken.
238  *
239  * returns NULL if no connection with the given token value exists.
240  */
241 struct mptcp_sock *mptcp_token_get_sock(u32 token)
242 {
243 	struct hlist_nulls_node *pos;
244 	struct token_bucket *bucket;
245 	struct mptcp_sock *msk;
246 	struct sock *sk;
247 
248 	rcu_read_lock();
249 	bucket = token_bucket(token);
250 
251 again:
252 	sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
253 		msk = mptcp_sk(sk);
254 		if (READ_ONCE(msk->token) != token)
255 			continue;
256 		if (!refcount_inc_not_zero(&sk->sk_refcnt))
257 			goto not_found;
258 		if (READ_ONCE(msk->token) != token) {
259 			sock_put(sk);
260 			goto again;
261 		}
262 		goto found;
263 	}
264 	if (get_nulls_value(pos) != (token & token_mask))
265 		goto again;
266 
267 not_found:
268 	msk = NULL;
269 
270 found:
271 	rcu_read_unlock();
272 	return msk;
273 }
274 EXPORT_SYMBOL_GPL(mptcp_token_get_sock);
275 
276 /**
277  * mptcp_token_iter_next - iterate over the token container from given pos
278  * @net: namespace to be iterated
279  * @s_slot: start slot number
280  * @s_num: start number inside the given lock
281  *
282  * This function returns the first mptcp connection structure found inside the
283  * token container starting from the specified position, or NULL.
284  *
285  * On successful iteration, the iterator is move to the next position and the
286  * the acquires a reference to the returned socket.
287  */
288 struct mptcp_sock *mptcp_token_iter_next(const struct net *net, long *s_slot,
289 					 long *s_num)
290 {
291 	struct mptcp_sock *ret = NULL;
292 	struct hlist_nulls_node *pos;
293 	int slot, num = 0;
294 
295 	for (slot = *s_slot; slot <= token_mask; *s_num = 0, slot++) {
296 		struct token_bucket *bucket = &token_hash[slot];
297 		struct sock *sk;
298 
299 		num = 0;
300 
301 		if (hlist_nulls_empty(&bucket->msk_chain))
302 			continue;
303 
304 		rcu_read_lock();
305 		sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
306 			++num;
307 			if (!net_eq(sock_net(sk), net))
308 				continue;
309 
310 			if (num <= *s_num)
311 				continue;
312 
313 			if (!refcount_inc_not_zero(&sk->sk_refcnt))
314 				continue;
315 
316 			if (!net_eq(sock_net(sk), net)) {
317 				sock_put(sk);
318 				continue;
319 			}
320 
321 			ret = mptcp_sk(sk);
322 			rcu_read_unlock();
323 			goto out;
324 		}
325 		rcu_read_unlock();
326 	}
327 
328 out:
329 	*s_slot = slot;
330 	*s_num = num;
331 	return ret;
332 }
333 EXPORT_SYMBOL_GPL(mptcp_token_iter_next);
334 
335 /**
336  * mptcp_token_destroy_request - remove mptcp connection/token
337  * @req: mptcp request socket dropping the token
338  *
339  * Remove the token associated to @req.
340  */
341 void mptcp_token_destroy_request(struct request_sock *req)
342 {
343 	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
344 	struct mptcp_subflow_request_sock *pos;
345 	struct token_bucket *bucket;
346 
347 	if (hlist_nulls_unhashed(&subflow_req->token_node))
348 		return;
349 
350 	bucket = token_bucket(subflow_req->token);
351 	spin_lock_bh(&bucket->lock);
352 	pos = __token_lookup_req(bucket, subflow_req->token);
353 	if (!WARN_ON_ONCE(pos != subflow_req)) {
354 		hlist_nulls_del_init_rcu(&pos->token_node);
355 		bucket->chain_len--;
356 	}
357 	spin_unlock_bh(&bucket->lock);
358 }
359 
360 /**
361  * mptcp_token_destroy - remove mptcp connection/token
362  * @msk: mptcp connection dropping the token
363  *
364  * Remove the token associated to @msk
365  */
366 void mptcp_token_destroy(struct mptcp_sock *msk)
367 {
368 	struct token_bucket *bucket;
369 	struct mptcp_sock *pos;
370 
371 	if (sk_unhashed((struct sock *)msk))
372 		return;
373 
374 	bucket = token_bucket(msk->token);
375 	spin_lock_bh(&bucket->lock);
376 	pos = __token_lookup_msk(bucket, msk->token);
377 	if (!WARN_ON_ONCE(pos != msk)) {
378 		__sk_nulls_del_node_init_rcu((struct sock *)pos);
379 		bucket->chain_len--;
380 	}
381 	spin_unlock_bh(&bucket->lock);
382 }
383 
384 void __init mptcp_token_init(void)
385 {
386 	int i;
387 
388 	token_hash = alloc_large_system_hash("MPTCP token",
389 					     sizeof(struct token_bucket),
390 					     0,
391 					     20,/* one slot per 1MB of memory */
392 					     HASH_ZERO,
393 					     NULL,
394 					     &token_mask,
395 					     0,
396 					     64 * 1024);
397 	for (i = 0; i < token_mask + 1; ++i) {
398 		INIT_HLIST_NULLS_HEAD(&token_hash[i].req_chain, i);
399 		INIT_HLIST_NULLS_HEAD(&token_hash[i].msk_chain, i);
400 		spin_lock_init(&token_hash[i].lock);
401 	}
402 }
403 
404 #if IS_MODULE(CONFIG_MPTCP_KUNIT_TEST)
405 EXPORT_SYMBOL_GPL(mptcp_token_new_request);
406 EXPORT_SYMBOL_GPL(mptcp_token_new_connect);
407 EXPORT_SYMBOL_GPL(mptcp_token_accept);
408 EXPORT_SYMBOL_GPL(mptcp_token_destroy_request);
409 EXPORT_SYMBOL_GPL(mptcp_token_destroy);
410 #endif
411