xref: /openbmc/linux/net/mptcp/token.c (revision b03afaa8) 
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 	int retries = TOKEN_MAX_RETRIES;
113 	struct token_bucket *bucket;
114 	u32 token;
115 
116 again:
117 	mptcp_crypto_key_gen_sha(&subflow_req->local_key,
118 				 &subflow_req->token,
119 				 &subflow_req->idsn);
120 	pr_debug("req=%p local_key=%llu, token=%u, idsn=%llu\n",
121 		 req, subflow_req->local_key, subflow_req->token,
122 		 subflow_req->idsn);
123 
124 	token = subflow_req->token;
125 	bucket = token_bucket(token);
126 	spin_lock_bh(&bucket->lock);
127 	if (__token_bucket_busy(bucket, token)) {
128 		spin_unlock_bh(&bucket->lock);
129 		if (!--retries)
130 			return -EBUSY;
131 		goto again;
132 	}
133 
134 	hlist_nulls_add_head_rcu(&subflow_req->token_node, &bucket->req_chain);
135 	bucket->chain_len++;
136 	spin_unlock_bh(&bucket->lock);
137 	return 0;
138 }
139 
140 /**
141  * mptcp_token_new_connect - create new key/idsn/token for subflow
142  * @sk: the socket that will initiate a connection
143  *
144  * This function is called when a new outgoing mptcp connection is
145  * initiated.
146  *
147  * It creates a unique token to identify the new mptcp connection,
148  * a secret local key and the initial data sequence number (idsn).
149  *
150  * On success, the mptcp connection can be found again using
151  * the computed token at a later time, this is needed to process
152  * join requests.
153  *
154  * returns 0 on success.
155  */
156 int mptcp_token_new_connect(struct sock *sk)
157 {
158 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
159 	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
160 	int retries = TOKEN_MAX_RETRIES;
161 	struct token_bucket *bucket;
162 
163 	pr_debug("ssk=%p, local_key=%llu, token=%u, idsn=%llu\n",
164 		 sk, subflow->local_key, subflow->token, subflow->idsn);
165 
166 again:
167 	mptcp_crypto_key_gen_sha(&subflow->local_key, &subflow->token,
168 				 &subflow->idsn);
169 
170 	bucket = token_bucket(subflow->token);
171 	spin_lock_bh(&bucket->lock);
172 	if (__token_bucket_busy(bucket, subflow->token)) {
173 		spin_unlock_bh(&bucket->lock);
174 		if (!--retries)
175 			return -EBUSY;
176 		goto again;
177 	}
178 
179 	WRITE_ONCE(msk->token, subflow->token);
180 	__sk_nulls_add_node_rcu((struct sock *)msk, &bucket->msk_chain);
181 	bucket->chain_len++;
182 	spin_unlock_bh(&bucket->lock);
183 	return 0;
184 }
185 
186 /**
187  * mptcp_token_accept - replace a req sk with full sock in token hash
188  * @req: the request socket to be removed
189  * @msk: the just cloned socket linked to the new connection
190  *
191  * Called when a SYN packet creates a new logical connection, i.e.
192  * is not a join request.
193  */
194 void mptcp_token_accept(struct mptcp_subflow_request_sock *req,
195 			struct mptcp_sock *msk)
196 {
197 	struct mptcp_subflow_request_sock *pos;
198 	struct token_bucket *bucket;
199 
200 	bucket = token_bucket(req->token);
201 	spin_lock_bh(&bucket->lock);
202 
203 	/* pedantic lookup check for the moved token */
204 	pos = __token_lookup_req(bucket, req->token);
205 	if (!WARN_ON_ONCE(pos != req))
206 		hlist_nulls_del_init_rcu(&req->token_node);
207 	__sk_nulls_add_node_rcu((struct sock *)msk, &bucket->msk_chain);
208 	spin_unlock_bh(&bucket->lock);
209 }
210 
211 /**
212  * mptcp_token_get_sock - retrieve mptcp connection sock using its token
213  * @token: token of the mptcp connection to retrieve
214  *
215  * This function returns the mptcp connection structure with the given token.
216  * A reference count on the mptcp socket returned is taken.
217  *
218  * returns NULL if no connection with the given token value exists.
219  */
220 struct mptcp_sock *mptcp_token_get_sock(u32 token)
221 {
222 	struct hlist_nulls_node *pos;
223 	struct token_bucket *bucket;
224 	struct mptcp_sock *msk;
225 	struct sock *sk;
226 
227 	rcu_read_lock();
228 	bucket = token_bucket(token);
229 
230 again:
231 	sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
232 		msk = mptcp_sk(sk);
233 		if (READ_ONCE(msk->token) != token)
234 			continue;
235 		if (!refcount_inc_not_zero(&sk->sk_refcnt))
236 			goto not_found;
237 		if (READ_ONCE(msk->token) != token) {
238 			sock_put(sk);
239 			goto again;
240 		}
241 		goto found;
242 	}
243 	if (get_nulls_value(pos) != (token & token_mask))
244 		goto again;
245 
246 not_found:
247 	msk = NULL;
248 
249 found:
250 	rcu_read_unlock();
251 	return msk;
252 }
253 EXPORT_SYMBOL_GPL(mptcp_token_get_sock);
254 
255 /**
256  * mptcp_token_iter_next - iterate over the token container from given pos
257  * @net: namespace to be iterated
258  * @s_slot: start slot number
259  * @s_num: start number inside the given lock
260  *
261  * This function returns the first mptcp connection structure found inside the
262  * token container starting from the specified position, or NULL.
263  *
264  * On successful iteration, the iterator is move to the next position and the
265  * the acquires a reference to the returned socket.
266  */
267 struct mptcp_sock *mptcp_token_iter_next(const struct net *net, long *s_slot,
268 					 long *s_num)
269 {
270 	struct mptcp_sock *ret = NULL;
271 	struct hlist_nulls_node *pos;
272 	int slot, num;
273 
274 	for (slot = *s_slot; slot <= token_mask; *s_num = 0, slot++) {
275 		struct token_bucket *bucket = &token_hash[slot];
276 		struct sock *sk;
277 
278 		num = 0;
279 
280 		if (hlist_nulls_empty(&bucket->msk_chain))
281 			continue;
282 
283 		rcu_read_lock();
284 		sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
285 			++num;
286 			if (!net_eq(sock_net(sk), net))
287 				continue;
288 
289 			if (num <= *s_num)
290 				continue;
291 
292 			if (!refcount_inc_not_zero(&sk->sk_refcnt))
293 				continue;
294 
295 			if (!net_eq(sock_net(sk), net)) {
296 				sock_put(sk);
297 				continue;
298 			}
299 
300 			ret = mptcp_sk(sk);
301 			rcu_read_unlock();
302 			goto out;
303 		}
304 		rcu_read_unlock();
305 	}
306 
307 out:
308 	*s_slot = slot;
309 	*s_num = num;
310 	return ret;
311 }
312 EXPORT_SYMBOL_GPL(mptcp_token_iter_next);
313 
314 /**
315  * mptcp_token_destroy_request - remove mptcp connection/token
316  * @req: mptcp request socket dropping the token
317  *
318  * Remove the token associated to @req.
319  */
320 void mptcp_token_destroy_request(struct request_sock *req)
321 {
322 	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
323 	struct mptcp_subflow_request_sock *pos;
324 	struct token_bucket *bucket;
325 
326 	if (hlist_nulls_unhashed(&subflow_req->token_node))
327 		return;
328 
329 	bucket = token_bucket(subflow_req->token);
330 	spin_lock_bh(&bucket->lock);
331 	pos = __token_lookup_req(bucket, subflow_req->token);
332 	if (!WARN_ON_ONCE(pos != subflow_req)) {
333 		hlist_nulls_del_init_rcu(&pos->token_node);
334 		bucket->chain_len--;
335 	}
336 	spin_unlock_bh(&bucket->lock);
337 }
338 
339 /**
340  * mptcp_token_destroy - remove mptcp connection/token
341  * @msk: mptcp connection dropping the token
342  *
343  * Remove the token associated to @msk
344  */
345 void mptcp_token_destroy(struct mptcp_sock *msk)
346 {
347 	struct token_bucket *bucket;
348 	struct mptcp_sock *pos;
349 
350 	if (sk_unhashed((struct sock *)msk))
351 		return;
352 
353 	bucket = token_bucket(msk->token);
354 	spin_lock_bh(&bucket->lock);
355 	pos = __token_lookup_msk(bucket, msk->token);
356 	if (!WARN_ON_ONCE(pos != msk)) {
357 		__sk_nulls_del_node_init_rcu((struct sock *)pos);
358 		bucket->chain_len--;
359 	}
360 	spin_unlock_bh(&bucket->lock);
361 }
362 
363 void __init mptcp_token_init(void)
364 {
365 	int i;
366 
367 	token_hash = alloc_large_system_hash("MPTCP token",
368 					     sizeof(struct token_bucket),
369 					     0,
370 					     20,/* one slot per 1MB of memory */
371 					     HASH_ZERO,
372 					     NULL,
373 					     &token_mask,
374 					     0,
375 					     64 * 1024);
376 	for (i = 0; i < token_mask + 1; ++i) {
377 		INIT_HLIST_NULLS_HEAD(&token_hash[i].req_chain, i);
378 		INIT_HLIST_NULLS_HEAD(&token_hash[i].msk_chain, i);
379 		spin_lock_init(&token_hash[i].lock);
380 	}
381 }
382 
383 #if IS_MODULE(CONFIG_MPTCP_KUNIT_TESTS)
384 EXPORT_SYMBOL_GPL(mptcp_token_new_request);
385 EXPORT_SYMBOL_GPL(mptcp_token_new_connect);
386 EXPORT_SYMBOL_GPL(mptcp_token_accept);
387 EXPORT_SYMBOL_GPL(mptcp_token_destroy_request);
388 EXPORT_SYMBOL_GPL(mptcp_token_destroy);
389 #endif
390