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 
token_bucket(u32 token)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 *
__token_lookup_req(struct token_bucket * t,u32 token)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 *
__token_lookup_msk(struct token_bucket * t,u32 token)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 
__token_bucket_busy(struct token_bucket * t,u32 token)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 
mptcp_crypto_key_gen_sha(u64 * key,u32 * token,u64 * idsn)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  */
mptcp_token_new_request(struct request_sock * req)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  * returns 0 on success.
150  */
mptcp_token_new_connect(struct sock * ssk)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_accept - replace a req sk with full sock in token hash
185  * @req: the request socket to be removed
186  * @msk: the just cloned socket linked to the new connection
187  *
188  * Called when a SYN packet creates a new logical connection, i.e.
189  * is not a join request.
190  */
mptcp_token_accept(struct mptcp_subflow_request_sock * req,struct mptcp_sock * msk)191 void mptcp_token_accept(struct mptcp_subflow_request_sock *req,
192 			struct mptcp_sock *msk)
193 {
194 	struct mptcp_subflow_request_sock *pos;
195 	struct sock *sk = (struct sock *)msk;
196 	struct token_bucket *bucket;
197 
198 	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
199 	bucket = token_bucket(req->token);
200 	spin_lock_bh(&bucket->lock);
201 
202 	/* pedantic lookup check for the moved token */
203 	pos = __token_lookup_req(bucket, req->token);
204 	if (!WARN_ON_ONCE(pos != req))
205 		hlist_nulls_del_init_rcu(&req->token_node);
206 	__sk_nulls_add_node_rcu((struct sock *)msk, &bucket->msk_chain);
207 	spin_unlock_bh(&bucket->lock);
208 }
209 
mptcp_token_exists(u32 token)210 bool mptcp_token_exists(u32 token)
211 {
212 	struct hlist_nulls_node *pos;
213 	struct token_bucket *bucket;
214 	struct mptcp_sock *msk;
215 	struct sock *sk;
216 
217 	rcu_read_lock();
218 	bucket = token_bucket(token);
219 
220 again:
221 	sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
222 		msk = mptcp_sk(sk);
223 		if (READ_ONCE(msk->token) == token)
224 			goto found;
225 	}
226 	if (get_nulls_value(pos) != (token & token_mask))
227 		goto again;
228 
229 	rcu_read_unlock();
230 	return false;
231 found:
232 	rcu_read_unlock();
233 	return true;
234 }
235 
236 /**
237  * mptcp_token_get_sock - retrieve mptcp connection sock using its token
238  * @net: restrict to this namespace
239  * @token: token of the mptcp connection to retrieve
240  *
241  * This function returns the mptcp connection structure with the given token.
242  * A reference count on the mptcp socket returned is taken.
243  *
244  * returns NULL if no connection with the given token value exists.
245  */
mptcp_token_get_sock(struct net * net,u32 token)246 struct mptcp_sock *mptcp_token_get_sock(struct net *net, u32 token)
247 {
248 	struct hlist_nulls_node *pos;
249 	struct token_bucket *bucket;
250 	struct mptcp_sock *msk;
251 	struct sock *sk;
252 
253 	rcu_read_lock();
254 	bucket = token_bucket(token);
255 
256 again:
257 	sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
258 		msk = mptcp_sk(sk);
259 		if (READ_ONCE(msk->token) != token ||
260 		    !net_eq(sock_net(sk), net))
261 			continue;
262 
263 		if (!refcount_inc_not_zero(&sk->sk_refcnt))
264 			goto not_found;
265 
266 		if (READ_ONCE(msk->token) != token ||
267 		    !net_eq(sock_net(sk), net)) {
268 			sock_put(sk);
269 			goto again;
270 		}
271 		goto found;
272 	}
273 	if (get_nulls_value(pos) != (token & token_mask))
274 		goto again;
275 
276 not_found:
277 	msk = NULL;
278 
279 found:
280 	rcu_read_unlock();
281 	return msk;
282 }
283 EXPORT_SYMBOL_GPL(mptcp_token_get_sock);
284 
285 /**
286  * mptcp_token_iter_next - iterate over the token container from given pos
287  * @net: namespace to be iterated
288  * @s_slot: start slot number
289  * @s_num: start number inside the given lock
290  *
291  * This function returns the first mptcp connection structure found inside the
292  * token container starting from the specified position, or NULL.
293  *
294  * On successful iteration, the iterator is moved to the next position and
295  * a reference to the returned socket is acquired.
296  */
mptcp_token_iter_next(const struct net * net,long * s_slot,long * s_num)297 struct mptcp_sock *mptcp_token_iter_next(const struct net *net, long *s_slot,
298 					 long *s_num)
299 {
300 	struct mptcp_sock *ret = NULL;
301 	struct hlist_nulls_node *pos;
302 	int slot, num = 0;
303 
304 	for (slot = *s_slot; slot <= token_mask; *s_num = 0, slot++) {
305 		struct token_bucket *bucket = &token_hash[slot];
306 		struct sock *sk;
307 
308 		num = 0;
309 
310 		if (hlist_nulls_empty(&bucket->msk_chain))
311 			continue;
312 
313 		rcu_read_lock();
314 		sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
315 			++num;
316 			if (!net_eq(sock_net(sk), net))
317 				continue;
318 
319 			if (num <= *s_num)
320 				continue;
321 
322 			if (!refcount_inc_not_zero(&sk->sk_refcnt))
323 				continue;
324 
325 			if (!net_eq(sock_net(sk), net)) {
326 				sock_put(sk);
327 				continue;
328 			}
329 
330 			ret = mptcp_sk(sk);
331 			rcu_read_unlock();
332 			goto out;
333 		}
334 		rcu_read_unlock();
335 	}
336 
337 out:
338 	*s_slot = slot;
339 	*s_num = num;
340 	return ret;
341 }
342 EXPORT_SYMBOL_GPL(mptcp_token_iter_next);
343 
344 /**
345  * mptcp_token_destroy_request - remove mptcp connection/token
346  * @req: mptcp request socket dropping the token
347  *
348  * Remove the token associated to @req.
349  */
mptcp_token_destroy_request(struct request_sock * req)350 void mptcp_token_destroy_request(struct request_sock *req)
351 {
352 	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
353 	struct mptcp_subflow_request_sock *pos;
354 	struct token_bucket *bucket;
355 
356 	if (hlist_nulls_unhashed(&subflow_req->token_node))
357 		return;
358 
359 	bucket = token_bucket(subflow_req->token);
360 	spin_lock_bh(&bucket->lock);
361 	pos = __token_lookup_req(bucket, subflow_req->token);
362 	if (!WARN_ON_ONCE(pos != subflow_req)) {
363 		hlist_nulls_del_init_rcu(&pos->token_node);
364 		bucket->chain_len--;
365 	}
366 	spin_unlock_bh(&bucket->lock);
367 }
368 
369 /**
370  * mptcp_token_destroy - remove mptcp connection/token
371  * @msk: mptcp connection dropping the token
372  *
373  * Remove the token associated to @msk
374  */
mptcp_token_destroy(struct mptcp_sock * msk)375 void mptcp_token_destroy(struct mptcp_sock *msk)
376 {
377 	struct sock *sk = (struct sock *)msk;
378 	struct token_bucket *bucket;
379 	struct mptcp_sock *pos;
380 
381 	if (sk_unhashed((struct sock *)msk))
382 		return;
383 
384 	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
385 	bucket = token_bucket(msk->token);
386 	spin_lock_bh(&bucket->lock);
387 	pos = __token_lookup_msk(bucket, msk->token);
388 	if (!WARN_ON_ONCE(pos != msk)) {
389 		__sk_nulls_del_node_init_rcu((struct sock *)pos);
390 		bucket->chain_len--;
391 	}
392 	spin_unlock_bh(&bucket->lock);
393 	WRITE_ONCE(msk->token, 0);
394 }
395 
mptcp_token_init(void)396 void __init mptcp_token_init(void)
397 {
398 	int i;
399 
400 	token_hash = alloc_large_system_hash("MPTCP token",
401 					     sizeof(struct token_bucket),
402 					     0,
403 					     20,/* one slot per 1MB of memory */
404 					     HASH_ZERO,
405 					     NULL,
406 					     &token_mask,
407 					     0,
408 					     64 * 1024);
409 	for (i = 0; i < token_mask + 1; ++i) {
410 		INIT_HLIST_NULLS_HEAD(&token_hash[i].req_chain, i);
411 		INIT_HLIST_NULLS_HEAD(&token_hash[i].msk_chain, i);
412 		spin_lock_init(&token_hash[i].lock);
413 	}
414 }
415 
416 #if IS_MODULE(CONFIG_MPTCP_KUNIT_TEST)
417 EXPORT_SYMBOL_GPL(mptcp_token_new_request);
418 EXPORT_SYMBOL_GPL(mptcp_token_new_connect);
419 EXPORT_SYMBOL_GPL(mptcp_token_accept);
420 EXPORT_SYMBOL_GPL(mptcp_token_destroy_request);
421 EXPORT_SYMBOL_GPL(mptcp_token_destroy);
422 #endif
423